SMI-2023: 14th International Conference on Stopping and Manipulation of Ions and Related Topics

Gas stopping of energetic projectile fragments has been an important pathway to science with stopped and reaccelerated beams at the National Superconducting Cyclotron Laboratory (NSCL) for almost two decades. The NSCL has transitioned into the recently opened Facility for Rare Isotope Beams (FRIB) to provide significantly more exotic and more intense exotic beams, prompting upgrades to the gas-stopping facility.
FRIB will continue to provide low-energy beams with the two operating linear gas-stopping cells. In order to extract light ions rapidly, which are difficult to stop efficiently in linear gas cells, a gas-filled reverse cyclotron has been constructed. The device uses a superconducting cyclotron-type magnet and helium gas to capture and stop the injected beam. The beam is transported to the center of the magnet by a traveling-wave RF-carpet system, extracted through the central bore with an ion conveyor and will be accelerated to a few ten keV energy for delivery to the users.
Following construction and successful low-energy ion transport tests with an internal ion source, the cyclotron gas stopper was moved to an experimental vault and connected to the A1900 fragment separator at the NSCL, now to the ARIS separator. After a series of runs with primary beams to commission the new dedicated high-energy beam line and test injection into the cyclotron stopper, a beam of 46K fragments was stopped and extracted. Beta activity with a half-life of 46K, detected at the end of the ion conveyor, proved successful extraction of this beam from the cyclotron stopper.
A summary of the commissioning tests with high-energy beam and plans for integrating the device into FRIB’s low-energy beam distribution network will be presented.

This material is based upon work supported by NSF under grants PHY-09-58726, PHY-11-02511, PHY-15-65546. It is also based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics and used resources of the Facility for Rare Isotope Beams (FRIB), which is a DOE Office of Science User Facility, under Award Number DE-SC0000661.

A new cryogenic ion catcher filled with helium gas has been commissioned at the ZeroDegree spectrometer following BigRIPS at RIKEN/RIBF for the thermalization of high-energy RI beams from the BigRIPS beamline, as a part of the SLOWRI facility. The ion catcher is combined with a multi-reflection time-of-flight mass spectrograph and both are located downstream of the ZeroDegree spectrometer. This setup had its first on-line commissioning run in December 2020, where we measured more than 70 nuclear masses including 3 new masses [1, 2].

The ion catcher consists of a reentrant cryogenic catcher gas cell and an outer vacuum chamber. The catcher gas cell has a two-stage RF carpet configuration [3]. In off-line tests, the ion transport was first investigated using surface ionization ion sources, followed by Ar$^+$ and Kr$^+$ ions produced by $\alpha$-particle emission in the helium gas. Recently, we have started ion transport tests using the fission products from a $^{248}$Cm fission source. We are investigating the ion transport efficiency and charge state distributions for the fission products of various elements.

In this talk, I will give an overview of the development of the ion catcher, possible plans for future upgrades, and prospects.

[1] S. Iimura et al., Phys. Rev. Lett. 130, 012501 (2023).
[2] M. Rosenbusch et al., Nucl. Instrum. Meth. A 1047, 167824 (2023).
[3] A. Takamine et al., RIKEN Accel. Prog. Rep. 52, 139 (2019).

The low-energy RI-beam production system by laser ionization, PALIS [1,2], is being developed at the RIKEN Radioactive Isotope Beam Factory (RIBF) SLOWRI facility. The small gas catcher cell was implemented in front of the second focal plane in the Superconducting Radioactive Isotope Beam Separator (BigRIPS). The ion extraction is based on the techniques of the Ion Guide Isotope Separator On-Line (IGISOL) and In-Gas laser ionization and Spectroscopy (IGLIS). PALIS is designed to enable low-energy RI-beam experiments by parasitic operation during the BigRIPS experiments. The presentation will consist of the current status of the development, commissioning results for off/on-line experiments and also introduce some peripheral equipment, such as the gas circulation system [3], optical components for long laser beam flight path[4].

References:
[1] T. Sonoda et al. Prog. Theor. Exp. Phys. 113 (2019) D02.
[2] T. Sonoda et. al. Nucl. Inst. And Meth. B295(2013)1.
[3] T. Sonoda et. al. Rev. Sci. Instrum. 87 (065104) (2016).
[4] T. Sonoda et. al. Nucl. Inst. and Meth. A877(2018)118.

The superconducting Linear Accelerator (SPIRAL2-LINAC) coupled with the Super Separator Spectrometer (S3) will allow GANIL to produce neutron-deficient and super heavy nuclei via fusion-evaporation reactions. At the focal plane of S3, the S3-Low Energy Branch (S3-LEB) setup will stop and neutralize the exotic ions before performing in-gas-jet resonant laser ionization that would allow accessing some fundamental properties of the nuclei. Moreover, this highly selective and efficient technique will produce pure beams for further measurements. Among these, mass measurements by a Multi-Reflection Time-Of-Flight Mass Spectrometer (MR-ToF-MS) will be performed.
JetRIS is working in complement to the Radiation Detected Resonance Ionization Spectroscopy (RADRIS) setup at GSI. RADRIS performed resonance ionization of heavy nuclides such as nobelium in the gas cell before guiding the laser-produced ions to an alpha detector. JetRIS is also using resonant ionization spectroscopy, but the technology is similar to the one chosen for the S3-LEB gas cell, where RIS is performed in a hypersonic gas jet to reduce the pressure and Doppler broadening inside the gas cell. Presently, the ions produced by resonant ionization are studied using an alpha detector for efficient detection with low background. It is foreseen to install an MR-TOF-MS to enhance the possibilities of the setup by using mass-selected ion detection. This will allow studying long-lived nuclides where an activity-based detection is impractical as well as beta-decaying nuclides.
Both setups will make use of an MR-ToF-MS, which requires the incoming beam to be bunched. For this, a Radio Frequency Quadrupole Cooler Buncher (RFQcb) has already been designed and is currently commissioned with the S3-LEB setup. This commissioning will make use of ion-trajectory simulations to get the best transmission possible during the bunching process and then compare these simulations to experimental results. Simulations for the bunching unit of the JetRIS setup are being prepared, adapting the design to that of the S3-LEB RFQcb.

Here, we present the ongoing work on the RFQcb simulations to improve the efficiency for S3-LEB in GANIL, and on the design for the new RFQcb for JetRIS at GSI.

Since 2010, the CARIBU facility at Argonne National Laboratory’s ATLAS facility has provided hundreds of neutron-rich isotopes for study. CARIBU delivers beams of these isotopes by first thermalizing the $^{252}$Cf spontaneous fission products inside a gas catcher system, then using an RFQ ion guide to direct the beam towards an isobar separator, an RFQ ion buncher, and finally an MR-TOF. The result is a highly efficient means to provide cooled, bunched, isobarically pure neutron-rich beams. This talk will describe the CARIBU facility and highlight the many successful experiments that benefited from CARIBU beams. CARIBU’s successor, nuCARIBU, will supply neutron-rich beams resulting from neutron-induced fission of various target foils inside the gas catcher. nuCARIBU is expected to be operational within a year, and a description of this upgrade to CARIBU will also be provided.

The production of exotic nuclei at the vicinity of the last abundance peak of the rapid-neutron capture (r-) process as for a long time pose a challenge. A new facility, called the N=126 Factory is currently under construction at Argonne National Laboratory and aims at undertaking this challenge by producing these exotic nuclei via multi-nucleon transfers reactions. The facility will first include a large-volume gas cell to collect and thermalize the reaction products. Then, upon extraction from the gas cell and radio-frequency quadrupole (RFQ) ion guide, the ion beam will be separated by a high-resolution mass separator magnet before being bunched in a RFQ ion cooler-buncher. The produced bunches will then be sent to a multi-reflection time-of-flight mass spectrometer (MR-ToF) for the removal of isobaric contamination. The first experimental equipment to take beams from the N=126 Factory will be the Canadian Penning Trap and several mass measurements proposals aimed at studying mass modeling predictions for the r-process near the N=126 and in the rare-earth region has already been accepted. The status of the N=126 Factory capabilities and construction status will be presented.
This work is supported in part by the U.S. Department of Energy, Office of Nuclear Physics, under Contract No. DE-AC02-06CH11357; by NSERC (Canada), Application No. SAPPJ-2018-00028; by the National Science Foundation under Grant No. PHY-2011890; by the University of Notre Dame; and with resources of ANL’s ATLAS facility, an Office of Science User Facility.

Multi-layer printed circuit boards (PCBs) are dielectric substrates with a thin metal layer glued together. With the current PCB manufacturing processes, metallic 2D planar structures can be tailored with fine resolution (<75 um) at a relatively low cost. These structures can be used to transport ions by applying the proper potential to the different planar electrodes. There is a wide variety of PCB-to-PCB and cable-to-PCB connectors, PCB mounting hardware, etc… making the use of several PCBs to create a 3D planar structure possible. Moreover, the PCB can also allocate, besides the electrodes which generate the electric field for ion transport, all the needed electronic components (resistors, capacitors…) to generate those electric fields, making it a monolithic structure easy to work with.
In the FRS Ion Catcher, several structures using PCB technology were designed and manufactured to transport ions in different environments, characterized by pressures ranging from low vacuum to atmospheric and temperatures ranging from cryogenic to room temperature. Those structures are mainly PCB radio frequency (RF) carpets. In the future, a PCB-based radio frequency quadrupole (RFQ) designed at the University of Edinburgh will be used at the FRS Ion Catcher.
A review of the different PCB-based ion transport structures used in the FRS Ion Catcher group and plans and developments covering fine-pitch RF Carpets, a PCB-based RFQ, and a testing chamber for future ion transport developments will be presented.

The Superallowed Transition Beta-Neutrino Decay Ion Coincidence Trap (St. Benedict) is currently under construction at the Nuclear Science Laboratory (NSL) at the University of Notre Dame. It aims to measure the beta-neutrino angular correlation parameter for superallowed mixed mirror beta decays. Measurements of this kind offer unique insight into the electroweak part of the Standard Model through tests of unitarity of the Cabibo-Kobayashi-Maskawa (CKM) matrix. In order to make these measurements at the required precision, radioactive ions coming from the tandem accelerator at the NSL must be stopped and then delivered to a trap in bunches with low emittance and well defined energy. St. Benedict will achieve this with the use of several elements including a large volume gas cell, a differentially pumped chamber containing both a radio-frequency carpet and a radio frequency quadrupole (RFQ) ion guide, an RFQ cooler and buncher and a Paul trap. Progress on the offline commissioning of the ion guide and cooler and buncher will be presented along with the status of the Paul trap. This work is supported by the National Science Foundation under grant number PHY-1725711.

Ion implantation is a well-known and popular method to study the significant modification in electrical, structural, magnetic, and optical properties in insulators and semiconductors to apply in various industrial developments. The Au ion implantation in transition metal oxide (NiO) can produce a different kind of vacancy and substitutional defects in the matrix that can modify the magnetic properties of the materials. In this context, we studied the defect-modulated magnetic anisotropy behavior of 90 nm thick NiO films using ion implantation. The electronic and nuclear energy loss value of 30 KeV Au ion in NiO is 0.37 and 4.80 KeV/cm, calculated from Stopping and Range of Ions in Matter (SRIM). The sputtering yield varies from 12.60 – 4.69 for O and 3.03 to 4.97 for Ni for the ion fluence of $5\times10^{14}$ – $1\times10^{16}$ ions/cm$^2$, respectively, calculated from TRIDYN and SRIM calculation shows that the projected range for 30 KeV Au in NiO is 6 nm. The thickness of the film reduces with ion fluences and has been observed from the dynamic TRIDYN simulation. The damages and vacancy defect states in the matrix are confirmed from photoluminescence spectra. The ion implantation-induced defect influences the crystallite size and affects the saturation magnetization and magneton number. The hysteresis of the M-H loop fitted with the general fit procedure of Kalchidagraph exhibits the ferromagnetic nature of NiO rather than antiferromagnetic behavior. The introduction of intermediate defect states observed from UV-Vis absorption spectra correlates the variation of saturation magnetization of ferromagnetism in NiO. In our case, defect-induced magnetic anisotropy in NiO thin films linearly varies with crystallite size. The tuneable magnetic anisotropy with defects in the NiO matrix may be useful for storage devices, battery cathodes, and gas sensors for technological applications.

In the Fragment Separator (FRS) at GSI, exotic nuclei are produced by projectile fragmentation and fission at relativistic energies, separated in-flight and range-bunched. For many experiments the nuclei have to be slowed down from relativistic energies to a few eV and thermalized. At the FRS Ion Catcher experiment, this is realized with a cryogenic gas-filled stopping cell (CSC). After the ions have been stopped and extracted from the CSC, they are guided through the gas filled RFQ beam line to a multiple-reflection time-of-flight mass spectrometer (MR-TOF-MS) for high precision mass measurements or isobar and isomer separation. In order to widen the range of measurable nuclei with shorter half-lives and be able to cope with higher beam intensities, some technical improvements had to be implemented. The CSC needs to be able to handle high incoming ion rates, for this purpose a special, shortened DC-electrode configuration was installed in the CSC, providing also the advantage to reduce the extraction time. On the other hand, the MR-TOF-MS has to run with high repetition rate yielding short cycle times and thus rendering very short-lived exotic nuclei to be experimentally accessible before their decay. Additionally, measurements with high repetition rates also result in a higher rate capability for the MR-TOF-MS, getting rid of the interactions between the ions (space-charge effects) and reducing the number of events detected under dead-time conditions.
In this poster, the dedicated technical improvements to achieve higher rate capability and higher repetition rate will be shown together with preliminary results.

Collaboration group: TORTORELLI, Nazarena (LMU, Munich, Germany and GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, Germany); AMANBAYEV, D. (JLU Gießen, Germany); AYET, S. (GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, Germany); BECK, S. (JLU Gießen, Germany); BERGMANN, J. (JLU Gießen, Germany); BRENCIC, Z. (Jozef Stefan Institute, Ljubljana, Slovenia); CONSTANTIN, P. (Extreme Light Infrastructure Nuclear Physics, Horia Hulubei National Institute for R & D in Physics and Nuclear Engineering, Bucharest-Magurele, Romania); DICKEL, T. (GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, Germany and JLU Gießen, Germany); GRÖF, L. (JLU Gießen, Germany); KRIPKO KONCZ, G. (JLU Gießen, Germany); MARDOR, I. (Soreq Nuclear Research Center, 8180000, Yavne, Israel and Doctoral School in Engineering and Applications of Lasers and Accelerators, University Polytechnica of Bucharest, Bucharest, Romania); NARANG, M. (GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, Germany); POHJALAINEN, I. (University of Jyväskylä, Finland); PLAß, W. R. (GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, Germany and JLU Gießen, Germany); REITER, M. P. (University of Edinburgh, UK); ROTARU, A. (Extreme Light Infrastructure Nuclear Physics, Horia Hulubei National Institute for R & D in Physics and Nuclear Engineering, Bucharest-Magurele, Romania and Doctoral School for Applied Sciences, University Polytechnica of Bucharest, Bucharest, Romania); SCHEIDENBERGER, C. (GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, Germany and JLU Gießen, Germany); THIROLF, P. (LMU Munich,Germany); YU, J. (GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, Germany); ZHAO, J. (GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, Germany and Peking University, Beijing, China).

Presenter: TORTORELLI, Nazarena (Ludwig-Maximilians-University Munich and GSI)

Comments:
This abstract is addressed for a poster session, it is not for a talk.

Multi-reflection time-of-flight (MRTOF) mass spectrometry [1] has become a new powerful tool for fast and precise measurements of atomic masses. It is a breakthrough-technology considering the required duration of a measurement and the small number of rare events needed to reach a relative mass precision of $\delta m/m \leq 10^{-7}$. In order to utilize the powerful isotope production capabilities of the RIBF facility and study nuclear masses for cutting-edge research, a new MRTOF mass spectrograph (MRTOF-MS) has been assembled; it became operational for the first time in spring 2020 [2]. The new device has been coupled to a cryogenic gas cell to convert the radioisotopes produced at relativistic energies into a low-energy beam amenable to ion trapping. The setup underwent an initial on-line commissioning at the BigRIPS facility at the end of 2020, wherein more than 70 nuclear masses were measured.
In this talk, I will explain the MRTOF technique and the new setup at BigRIPS along with advances like decay-correlated mass spectroscopy. Also the technological challenges will be discussed, e.g. providing low-energy ion beams at RIBF and reaching high mass accuracy. The topics will include efforts to decrease mass-dependent effects coming from non-static electric fields in the mass spectrometer, and some studies to increase the resolving power of the MRTOF system.
Furthermore, a short summary of the first commissioning experiments and follow-up mass measurements will be presented. Among other measurements presented, these results include new masses of neutron-rich titanium and vanadium isotopes revealing a vanishing of a shell gap at $N = 34$, which is known to be pronounced in Ca isotopes [3].

[1] H. Wollnik, M. Przewloka, Int. J. Mass Spectrom. Ion Proc. 96 (1990) 267.
[2] M. Rosenbusch et al., Nucl. Instrum. Meth. A 1047, 167824 (2023).
[3] S. Iimura et al., Phys. Rev. Lett. 130, 012501 (2023).

TRIUMF’s Ion Trap for Atomic and Nuclear science (TITAN) is specialized in high-precision measurement on exotic nuclei by using different electromagnetic traps. High-precision mass measurements of these isotopes are demanded for studies of nuclear structure and nuclear astrophysics processes, happening for isotopes far away from the valley of stability. However, one of the challenges when studying these rare isotopes at ISOL facilities is the amount of isobaric backgrounds produced from the target. To overcome this, the TITAN MR-TOF-MS applies mass selective Re-Trapping (RT) to be used as an isobar separator for beam purification with a high separation power. The isobarically-purified beam is then sent to the penning trap or other downstream experiments in TITAN. In addition, MR-TOF-MS can be used as its own isobar separator with RT cycles prior to the mass measurements. This will boost the usual 10$^4$ dynamic range of MR-TOF-MS to 10$^8$ and thus increasing the sensitivity of the system for detection of nuclei with a very low production yields (0.01 pps of $^{60}$Ga [1]). The TITAN MR-TOF MS enables the studies of short-lived and exotic nuclei far away from the valley of stability due to the fast measurement cycles (a few ms) and high sensitivity. In this work, the performance for isobaric purification, the capabilities and latest technical upgrades of MR-TOF-MS will be presented.
[1] S. Paul et al., Phys. Rev. C 104 065803 (2021)

The KEK Isotope Separation System (KISS) [1,2] facility for laser and decay spectroscopy of nuclides produced via multi-nucleon transfer (MNT) reactions is installed at the RIKEN Nishina Center. Recently, a multi-reflection time-of-flight mass spectrograph (MRTOF-MS) [3] has been installed to provide high-precision mass measurements. Following laser ionization ($Z$-selection) the KISS facility accelerates ions to 20~keV and employs a dipole magnet mass analyzer ($A$-selection) to delivery fairly high-purity beams from the vast cocktail of MNT products. To make the 20 keV KISS beam amenable to ion trapping, they are injection into a gas-cell-based cooler-buncher (GCCB) in which they thermalize. Most ions are up-charged to $q$=2$^{+}$ in the stopping process, while nearly all contaminant molecules are broken into light species and not efficiently transported by the RF carpet [4] or RF traps wherein ions are prepared prior to transfer to the MRTOF-MS for mass measurement. By combination of MNT with multi-stage purification, the application of high-precision mass spectroscopy by MRTOF-MS at KISS is expected to allow us to greatly expand the nuclear chart and deepen our understanding of the unexplored regions: around $N$ = 126 and southeast of uranium. \par
In this talk we will present details of the first experiments performed at KISS for the investigation of the actinide region. These experiments were performed with MNT products of the $^{238}$U + $^{198}$Pt system [5]. We have succeeded in the direct mass measurements of nineteen neutron-rich actinide nuclides spanning from protactinium to plutonium, including the first identification of a new uranium isotope ($^{241}$U) since the 1970s.

[1]~Y.~Hirayama \it{et al.}\rm, Nucl. Instrum. Meth. B \bf{353}\rm, 4 (2015). \par
[2]~Y.~Hirayama \it{et al.}\rm, Nucl. Instrum. Meth. B \bf{412}\rm, 11 (2017).\par
[3]~P. Schury \it{et al.}\rm, Nucl. Inst. Meth. B \bf{335}\rm, 39 (2014).\par
[4]~M. Wada \it{et al.}\rm, Nucl. Inst. Meth. B \bf{204}\rm, 570 (2003).\par
[5]~T. Niwase \it{et al.}\rm, Phys. Rev. Lett. in press. \par

The NEXT experiment intends to produce Neutron-rich EXotic heavy nuclei in multinucleon Transfer reactions. Measuring the mass of these nuclei to high precision provides information on their internal nuclear structure and useful input data for the modelling of nucleosynthesis processes.

The NEXT setup will be placed at the AGOR cyclotron at the Partrec facility in Groningen. The transfer products will be pre-separated in a solenoid separator before being slowed to thermal energies in a gas catcher and extracted via an RF carpet [1]. The extracted ions are bunched using a novel ion guide consisting of a stack of ring electrodes [2]. The bunched ions are then accelerated to a few keV and transferred to a Multi-Reflection Time-of-Flight Mass Spectrometer (MR-TOF MS) which separates the prepared ions from their isobaric contaminants and measures their masses. Simulation of the MR-TOF MS performance indicates that a mass resolving power of R $\sim10^5$ after only $300$ ion revolutions is possible for $^{85}$Rb$^+$ [3].

Currently the extraction performance of the gas catcher for heavy short-lived ions is being evaluated, while the MR-TOF has undergone commissioning and testing. The ion guide drivers are in development.

In this contribution an overview of the NEXT setup will be given, with focus on the gas catcher and MR-TOF MS, and the current project status will be discussed.

[1] J. Even, X. Chen, A. Soylu, P. Fischer, A. Karpov, V. Saiko, J. Saren, M. Schlaich, T. Schlathölter, L. Schweikhard, J. Uusitalo, and F. Wienholtz, “The NEXT project: Towards production and investigation of neutron-rich heavy nuclides,” Atoms, vol. 10, no. 2, p. 59, 2022.

[2] X. Chen, J. Even, P. Fischer, M. Schlaich, T. Schlathölter, L. Schweikhard, and A. Soylu, “Stacked-Ring Ion Guide for Cooling and Bunching Rare Isotopes”, International Journal of Mass Spectrometry, vol. 477, 116856, 2022.

[3] M. Schlaich, “Development and Characterization of a Multi-Reflection Time-of-Flight Mass Spectrometer for the Offline Ion Source of PUMA”, Master’s Thesis, Technische Universität Darmstadt, Darmstadt, Germany, 2021.

SHANS (Spectrometer for Heavy Atom and Nuclear Structure), which is a gas-filled recoil separator located at the Institute of Modern Physics in Lanzhou, is an apparatus used to study the heavy nuclei produced in the heavy-ion-induced fusion reactions. Over the past decade, a dozen of isotopes have been synthesized for the first time on this separator and their structures have been investigated.

An MRTOF-MS (Multi-Reflection Time-of-Flight Mass Spectrometer) with a new configuration different from the existed ones coupled with a CGC (Cryogenic Gas Catcher) and an ion cooling trap system, is being developed at SHANS to extend its research field such as isobaric selection and high precision mass measurement. Each of these three subsystems has passed the test, the transport efficiency of the radio-frequency carpet of the CGC is larger than 80%, the width of the pulsed beam extracted from the trap system is about 300 ns, the mass resolving power of the MRTOF-MS reached 90 000, and an efficiency of about 50% of the mass spectrometer has been obtained.

In this talk, SHANS together with the main experimental results on it will be reviewed, and the design, construction, offline commissioning and performance of CGC, trap and MRTOF-MS will be presented in detail.

V.A. Virtanen*,1 T. Eronen A. Kankainen and the I284 and I279 collaborations

Multi-Reflection Time-of-Flight Mass-Spectrometers (MR-ToF-MS) [1] have gained ground in radioactive beam facilities in the past 10 years, due to their comparatively fast operation cycles (~10 ms) and high mass resolving powers (R = m/dm ~ 2∙105). This enables the separation and subsequent mass measurement of particularly short-lived and exotic radioactive nuclei. The operation of an MR-ToF-MS is based on trapping a temporally short bunches of ions (~50 ns FWHM in temporal width), which have been accelerated to an approximately the same energy. Ions with different mass-to-charge ratios are separated by their time-of-flight, as they are trapped and moving along closed paths in the device. At the Ion-Guide Isotope-Separator On-Line (IGISOL) facility [2] at the University of Jyväskylä an MR-ToF-MS has been recently commissioned and used for mass separation and measurements of exotic isobaric radioactive nuclei. The MR-ToF-MS can also be used for selecting ions for other experiments, such as decay spectroscopy. In this contribution, an overview and the recent mass measurements utilizing the IGISOL MR-ToF-MS are presented, with preliminary mass spectra of fission fragments around A=90, relevant for the astrophysical rapid neutron capture process (r process), as well as mass spectra of multi-nucleon transfer reaction products produced with xenon beam on bismuth target.

References

[1] W. R. Plan, T. Dickel, and C. Scheidenberger, “Multiple-reflection time-of-flight mass spectrometry”, International Journal of Mass Spectrometry, vol. 349-350, pp. 134–144, 2013. doi: 10.1016/j.ijms.2013.06.005.

[2] I. Moore et al., “Towards commissioning the new IGISOL-4 facility”, Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, vol. 317, pp. 208–213, 2013. doi: 10.1016/j.nimb.2013.06.036.

At GSI, Darmstadt, Germany we use the in gas-Jet Resonant Ionization Spectroscopy (JetRIS) apparatus [1] to perform laser spectroscopy of elements in the heavy actinide region to determine their atomic and nuclear properties. JetRIS presently utilizes $\alpha$-decay detection to maximize sensitivity while minimizing the background from unwanted ions. However, for long-lived nuclides (t$_\frac{1}{2}>$ 10 h) a decay-based detection will not be practical. Thus, a multi-reflection time-of-flight mass separator (MR-ToF MS) is being developed for the JetRIS apparatus, allowing a separation of ions according to their mass-to-charge ratios with a high mass-resolving power, opening the possibility of mass-selected ion detection. This will also allow measuring $\beta$-decaying species and long-lived isotopes. An overview of the MR-ToF MS design and its integration into the system will be given. Prospects for future measurements will be discussed.
$\lbrack$1$\rbrack$ S. Raeder et al., NIM-B 2020, 463, 272–276.

We have developed the KEK Isotope Separation System (KISS) [1] at RIKEN to study heavy element synthesis in the universe. KISS presently consists of an argon gas cell based laser ion source (atomic number selection) followed by isotope separation on-line (mass number selection). KISS has successfully provided pure low-energy beams of neutron-rich isotopes near $N=$ 126 in the platinum region and near $N=$ 152 in the uranium region produced by multi-nucleon transfer reactions, which were studied by their nuclear spectroscopy such as $\beta$-decay spectroscopy, mass measurements, and laser spectroscopy.

To extend the studies to more neutron-rich regions, we plan to upgrade the KISS facility to KISS-II [2] whereby we replace the present argon gas cell with a next-generation, large-volume, cryogenic helium gas catcher utilizing an advanced RF curtain structure. The RF curtain structure features a 4-phase RF traveling wave technique [3] which enables efficient transport of the desired radioactive ions under a strong plasma of He$^{2+}$ and e$^-$ induced by ionizing interactions with the primary and secondary beams. The helium gas catcher can offer faster, more efficient, and element-independent extraction of ions. Delivering such wide isobaric cocktail beams to the existing multi-reflection time-of-flight mass spectrograph (MRTOF-MS) will allow for high-efficacy mass measurements as the device can simultaneously analyze numerous ion species. For e.g. decay studies, the MRTOF-MS could be used to provide an isobarically (or even isomerically) pure beam as well. Therefore, the use of a helium gas catcher could provide at least one order of magnitude improvement in experimental efficacy over the existing argon gas cell.

In advance of the development of the large-volume He gas catcher, we have started to test the RF curtain structure installed in a small-volume cryogenic helium gas catcher at KISS. We could successfully extract radioactive ions from the gas catcher and identify them by using the MRTOF-MS. In this presentation, we will introduce the activities at KISS and the overview of KISS-II, and report the development of the small-volume cryogenic helium gas catcher.

[1] Y. Hirayama et al., Nucl. Instr. and Meth. B 353 (2015) 4, B 412 (2017) 11.
[2] T. Aoki et al., https://arxiv.org/abs/2209.12649v2.
[3] K.R. Lund et al., Nucl. Instru. and Meth. B 463 (2020) 378.

The gas-stopping technique is considered very efficient for slowing down the incident radioactive beam ions having from E = a few 10 keV to a few GeV and manipulating for further applications [1-3]. After multiple collisions with buffer gas atoms, the ions are thermalized, transported by the DC field or the RF field or combined both, and utilized for various applications, i.e. high precision measurement or reacceleration.
In the ISOL beamline at RAON, a heavy-ion accelerator complex that is newly constructed in Korea [4], a gas-cell cooler and buncher, shortly GCCB has been installed to manipulate the low energy RI beam ions produced by the ISOL method, whose design is based on that in the KISS facility (KEK/WNSC). Filled with room-temperature helium gas of low pressure below 2.5 mbar, it implements a combination of DC and RF fields to utilize ion surfing mode for ion transportation [5]. The ions near the exit orifice are extracted by the gas flow, guided by an RFQ ion guide, and delivered to a trap system. The trap system comprises two linear Paul traps and a flat trap, after which an MRTOF mass analyzer is located. The characteristics of the GCCB were investigated by an ion source inside and outside the gas cell after construction, where the MRTOF was utilized for analyzing the behaviors it showed under different conditions.
As another gas stopper in RAON, an RFQ cooler-buncher was installed to provide bunched ions of improved emittance for an electron beam ion source (EBIS) and a collinear laser spectrometer (CLS) in 2021 [6] and is now operational.
In this presentation, the current status of the gas stoppers (GCCB and RFQ-CB) as well as the ISOL facility in RAON will be shared.

The Standard Model is known to be incomplete. One such area where it falls short is evidenced by the most precise evaluation of the V$_{ud}$ element of the CKM matrix, which currently yields a $\sim$2.4$\sigma$ tension with unitarity. In an effort to further study this, the Superallowed Beta-Neutrino Decay Ion Coincidence Trap (St. Benedict), in construction at the University of Notre Dame Nuclear Science Laboratory (NSL), aims to precisely measure the beta-neutrino angular correlation parameter in superallowed mixed $\beta$ decay transitions between mirror nuclei in order to improve the accuracy on the determination of V$_{ud}$. St. Benedict will consist of a gas catcher to stop the radioactive ion beams produced by the NSL’s TwinSol RIB facility; a radio-frequency (RF) carpet and radio-frequency quadrupole (RFQ) ion guide to transport the ions through a differentially pumped region; an RFQ cooler and buncher to cool and bunch the beam; and a linear Paul trap where the measurement will take place. The off-line commissioning of the gas catcher and the RF carpet will be presented. This work is supported by the NSF under grant number PHY-1725711.

The Isotope Separator On-Line (ISOL) facility at Japan Atomic Energy Agency (JAEA) is utilized for precision experiments on short-lived radioactive isotopes (RI) using ion trap techniques. This has the potential to facilitate new research areas in nuclear physics and chemistry, including mass measurements of neutron-rich transactinide nuclei and in-trap gas-phase ion chemistry of superheavy elements. To conduct such experiments, efficient and rapid production of low-energy RI beams with energies in the electron-volt range is required.
To achieve this, we have developed a windowless gas cell cooler and buncher (GCCB) that is capable of passing 30-keV ion beams from ISOL into a 100-Pa helium gas cell through an entrance hole without a thin window and decelerating and thermalizing ions purely through gas collisions with helium atoms, without any electrostatic deceleration [1]. The thermalized ions are then extracted by means of radiofrequency (RF) ion guide techniques, RF carpet and sextupole ion guide, and mass separated by a quadrupole mass separator. To investigate the gas cell performance and the characteristics of the extraction charge state, we used both stable and RI beams with a wide range of elements from Rubidium ($Z = 37$) to Actinium ($Z = 89$). We found that their extraction charge states were distributed up to 3+ and showed a strong dependence on their atomic structure. Our results allowed us to calculate the charge-changing cross-section at low energies [2] and could help predict the charge state distribution for extracted ion beams of desired elements, such as superheavy elements with production rates of less than one particle per hour.
In this talk, we will present the details of the GCCB apparatus and experimental results, along with the prospects of future experiments.

[1] Y. Ito et al., JPS Conf. Proc. 6 (2015) 030112, Ion preparation systems for low-energy experiments at SLOWRI.
[2] I.Yu. Tolstikhina, Y. Ito, V.P. Shevelko, Nucl. Instrum. Meth. B 532 (2022) 27, Prediction of charge-changing cross sections of low-charged $^{88}$Sr, $^{138}$Ba and $^{142}$Nd ions in a He-gas target at collision energies 50 eV/u-10 GeV/u.

Stopping devices provide access to a wide range of exotic radioactive ion beams with precise and low-energies at projectile fragmentation facilities. The stopping process includes slowing down the fast exotic beams in solid degraders combined with momentum compression and removal of the remaining kinetic energy by collision with helium buffer gas. The beam stopping facility at the Facility for Rare Isotopes Beams (FRIB) includes two gas cells, namely the Room Temperature Gas Cell (RTGC) constructed by Argonne National Lab and the Advanced Cryogenic Gas Stopper (ACGS), connected two momentum compression high beam lines and low energy transport systems. The ACGS is design and built to increase extraction efficiency, reduce drift time, reduce molecular contamination, and minimize space charge effect with relative to RTGC. Some of ACGS design properties has been tested with several beams and showed significant improvements. The stopped beam facility provides exotic radioactive beams to low energy experimental stations and reaccelerated experiments. The various user demands lead continuous improvements on the stopping and extraction efficiencies, the drift time in gas cell and the chemical forms of the extracted beams. The molecular forms of extracted ions have been studied for a variety of chemical elements at the room and cryogenic temperatures. The recent developments in ACGS and the stopped beam facility, and new challenges with the Advance Rare Isotope Separator (ARIS) beams will be presented.

Jiajun Yu, for the FRS Ion Catcher collaboration

In the FRS Ion Catcher (FRS-IC) [1-3] at GSI, short-lived nuclei produced at relativistic energies of up to 1 GeV/u at the fragment separator (FRS), are slowed down and thermalized in a cryogenic stopping cell (CSC) and identified/separated with a high-accuracy multiple-reflection time-of-flight mass spectrometer (MR-TOF-MS). High-accuracy mass measurements at the FRS-IC have been carried out over a wide range of the nuclear chart.

Over the past few years, significant technical upgrades and improvements have been incorporated into the FRS-IC setup. The IN-Cell REAction SystEm (INCREASE) experimental setup was constructed for multi-nucleon transfer and spontaneous fission experiments [4]. A slow control system has been developed to monitor, control, and log all components of the setup [5]. To ensure an ultra-pure gas condition, the gas lines, cold trap gas purifier, and trace gas line for charge-state manipulations of ions in the gas have been upgraded. Notably, the MR-TOF-MS has achieved one million mass resolving power, and a laser ablation carbon cluster ion source (LACCI) has been built and commissioned to provide calibrants for the MR-TOF-MS, achieving an accuracy of ~10-8 over the entire mass range. In addition, the 2D position sensitive MCP detector is being tested in MR-TOF-MS to enable quick system tuning. All of these latest developments at the FRS-IC will be presented in this contribution.

References:
[1] W.R. Plaß et al., Nucl. Instrum. Methods B, 317 (2013) 457
[2] W.R. Plaß et al., Int. J. Mass Spectrom. 394 (2013) 134
[3] T. Dickel et al., Nucl. Instrum. and Methods A, 777 (2015) 172
[4] R. Adrian et al., Nucl. Instrum. Methods B, 512 (2022) 83-90
[5] A.N. State et al., Nucl. Instrum. and Methods A 1034 (2022): 166772

Experiments with thermalized and low-energy exotic nuclides extracted from a gas-filled stopping cell rely on an efficient production, stopping and preparation of the mentioned rare nuclides. However, an often forgotten and only partially considered aspect is the interplay between the separator and the stopping in the stopping cell. Over the years, several novel techniques have been developed and applied for experiments with the FRS Ion Catcher at the final focus of the FRS at GSI, with the aim to improve access interesting short-lived nuclei.
These methods include:
(a) Rate enhancement and separation quality by careful selection of targets, beam energies and ion optics.
(b) Optimization of the stopping efficiency in terms of matching and manipulation of the longitudinal momentum distribution. This can be done to either achieve a high stopping efficiency of a single rare nuclide or to achieve stopping of a broad range of interesting nuclides at the same time.
(c) Coupling of the data acquisition systems of the FRS and the multiple-reflection time-of-flight mass spectrometer (MR-TOF-MS) of the FRS Ion Catcher to perform a time correlation between the FRS event by event in-flight particle identification and the extracted nuclei analyzed by the MR-TOF-MS.
Additionally, the FRS Ion Catcher is used as an independent diagnostics tool for other nuclear physics experiments. Via precise and accurate mass measurement an unambiguous and independent calibration of the in-flight particle identification can be performed.

The Low-Energy Branch (LEB) [1] for the MARA separator [2] is a facility under construction at the Accelerator Laboratory of the University of Jyväskylä. The facility will be used to study the ground-state properties and decay modes of exotic nuclei far from stability combining multiple techniques to investigate nuclear properties of isotopes far from stability.
MARA-LEB will stop and neutralise reaction products selected by the MARA separator in a small-volume buffer gas cell. A state-of-the-art Titanium:Sapphire laser system allows for re-ionsiation of selected species and for laser spectroscopic analysis. Re-ionised atoms can be extracted and accelerated by the ion transport system [3] and further mass- and velocity-selected before being directed either into specialised detector stations, for decay spectroscopy, or a dedicated cooler-buncher and Multi-Reflection Time-of-Flight Mass Spectrometer, for high-precision mass measurements.
In a recent experiment at MARA, where the dynamics of non-fusion reaction channels was studied by the GSI-JYFL collaboration various heavy nuclei in the 84 ≤ Z ≤ 92 region, which includes some light actinides, were produced. Data analysis from this experiment is still under way [4]. Nevertheless, preliminary experimental yields show that laser spectroscopy of these heavy nuclei may be feasible in the MARA-LEB facility.
This is a promising prospect given the recent increased interest in the study of exotic species in this region via the use of laser spectroscopical techniques [5]. There is limited information on the actinides due to low production cross-sections combined with the lack of stable isotopes for many of the elements in this group. The use of non-fusion reactions such as Multi-Nucleon Transfer (MNT) has been proposed as a way to enhance access to this region of the nuclear chart and thus improve the prospects for laser ionisation of these elements. MARA-LEB will combine the required mass resolution and laser spectroscopic capabilities to carry out studies in with these new experimental conditions.
An update on the current status of MARA-LEB will be presented, alongside a discussion of the feasibility of laser spectroscopy experiments in the new facility given the cross-sections extracted from these recent MARA experiments.

[1] P. Papadakis, et al., Hyperfine Interact. 237, 152 (2016).
[2] J. Uusitalo, J. Sarén, J. Partanen, J. Hilton, Acta Phys. Pol. B 50, 319 (2019).
[3] P. Papadakis, J. Liimatainen, J. Sarén, I. D. Moore, et al., Nucl. Instrum. Meth. Phys. Res. B 463, 286 (2020).
[4] J. Khuyagbaatar, et al., To be published.
[5] M. Block, M. Laatiaoui, S. Raeder, Prog. Part. Nucl. Phys. 116, 103834 (2021).

Klaus Wendt
Institute for Physics
Johannes Gutenberg University Mainz

The laser ion source trap LIST has been proposed about 20 years ago [1] and meanwhile successfully been implemented at ISOLDE and also elsewhere for strong selectivity enhancement in the ionization of exotic isotopes [2,3], specifically addressing those, which exhibits strong isobaric interferences. Recently the capability of using the device for direct in-source high resolution laser spectroscopy has been added by incorporating a transversal overlap region between laser beam and evaporating atomic species. This refinement was first tested off-line and afterwards adapted for on-line application at ISOLDE [4]. The technical developments and some recent results on direct in-source hyperfine structure and isotope shift measurements, carried out off-line on isotopes of Tc, lanthanides [5,6] and actinides [7] as well as the new on-line installation at ISOLDE will be discussed in the presentation.
[1] K. Blaum et al., Nucl. Instrum. Meth. Phys. Res. B 204 331–335 (2003)
[2] D.A. Fink et al., Nucl. Instr. Meth. in Phys. Res. B 344, 83-95 (2015)
[3] D.A. Fink et al., Phys. Rev. X 5,011018 (2015)
[4] R. Heinke et al., Hyp. Int. 238, 6 (2017)
[5] T. Kron et al, Phys. Rev C 102, 034307 (2020)
[5] D. Studer et al., Eur. Phys. J. A 56, 69 (2020)
[7] F. Weber et al., Phys. Rev. C 107, 034313 (2023)

The heaviest elements are of interest to nuclear and atomic physicists due to their peculiar properties. While nuclear shell structure effects are responsible for their very existence stabilizing them against spontaneous fission, the structure of their electronic shells is affected by strong relativistic effects leading to different atomic and chemical properties compared to their lighter homologs. Here, laser spectroscopy is a versatile tool to unveil fundamental atomic properties of an element while subtle changes in the atomic transition for different isotopes of the same element enable the inference of fundamental nuclear information. Any investigation of the heaviest elements is nevertheless hampered by their scarcity. Up to the chemical element fermium ($Z$=100), a limited number of long-lived isotopes can be produced in macroscopic amounts through irradiation of actinide samples in reactors where they undergo neutron capture and successive beta decay. Heavier elements and more exotic isotopes of the lighter actinide elements are only accessible through fusion-evaporation reactions at minute quantities and at high energies. An exploration of the region of the heaviest elements with laser spectroscopy became possible with the RAdiation Detected Resonance Ionization Spectroscopy (RADRIS) technique. Here, recoils from fusion-evaporation reactions are produced and separated by the velocity filter SHIP at GSI Darmstadt. The transmitted recoils are then stopped in high-purity argon gas and collected onto a thin filament. After re-evaporation, the released neutral atoms are probed by two-step resonance laser ionization. The so created photo-ions were then guided to a detector where they were identified by their characteristic alpha decay. After the first identification and characterization of a strong atomic ground-state transition in nobelium ($Z$=102), detailed studies on the nobelium isotopes $^{252-254}$No were performed.
In this contribution the present advancements and recent results of the RADRIS technique along with future prospects for laser spectroscopy of the heaviest elements will be presented. This includes the application on decay-daughter products of nobelium enabling the study of the fermium isotopes $^{248-250}$Fm, and with a dedicated detector setup also the long-lived isotope $^{254}$Fm (T$_{1/2}$=3.24h). The performance of the setup was in optimized for the necessary cycliy operation and the filament material to increase the total efficiency for the search of atomic levels in heavier elements such as lawrencium ($Z$=103). A first experimental campaign for the search of an atomic level in 255Fm was recently performed. Next steps include the extension of the RADRIS method to more exotic isotopes and the continuation of the level search in lawrencium as well as developments for higher spectral resolution spectroscopy. For the latter a dedicated setup was recently commissioned combining the efficient stopping and neutralization from the RADRIS technique with the high resolution of in-gas-jet spectroscopy. Laser spectroscopy in the low-density and low-temperature regime of the gas-jet enables higher resolution in the spectroscopy while the continuous operation and swift evacuation of the gas cell using electrical fields will allow us to address shorter-lived isotopes.

In-gas-jet laser spectroscopy of heavy actinides with JetRIS at GSI
Rafael Ferrer1, Julian Auler4, Michael Block2,3,4 Alexandre Brizard5, Premaditya Chhetri1, Arno Claessens1, Christoph E. Düllmann2,3,4, Francesca Giacoppo2, Manuel J. Gutiérrez2,3 Fritz-Peter Heßberger2, Fedor Ivandikov1, Tom Kieck2,3,4, EunKang Kim4, Sandro Kraemer1, Mustapha Laatiaoui4, Jeremy Lantis4, Nathalie Lecesne 5, Vladimir Manea6, D. Muenzberg2,3,4, Steven Nothhelfer2,3,4, Sebastian Raeder2,3, Emmanuel Rey-Herme7, Jekabs Romans1, Elisa Romero-Romero4, Elisabeth Rickert2,3,4, Antoine de Roubin1, Hervé Savajols5, Matou Stemmler8, Marine Vandebrouck7, Kenneth van Beek2,9, Piet Van Duppen1, Jessica Warbinek2,4, Klaus Wendt8, Alexander Yakushev2,3, Alexandra Zadvornaya1
1 KU Leuven, Instituut voor Kern- en Stralingsfysica, Leuven, Belgium
2 GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, DE
3 Helmholtz-Institut, Mainz, DE
4 Johannes Gutenberg-Universität, Department Chemie, Mainz, DE
5 GANIL, CEA/DRF-CNRS/IN2P3, B.P. 55027, 14076 Caen, France
6 Université Paris-Saclay, CNRS/IN2P3, IJCLab, 91405 Orsay, France
7 Irfu, CEA, Université Paris-Saclay, 91191 Gif-sur-Yvette, France
8 Johannes Gutenberg-Universität, Institut für Physik, Mainz, DE
9 Technische Universität, Institut für angewandte Physik, Darmstadt, DE

The In-Gas Laser Ionization and Spectroscopy (IGLIS) technique is a powerful tool to study atomic and nuclear properties of short-lived actinides. Such studies are important to understand the atomic level scheme of these heavy elements, which is influenced by strong electron correlations and relativistic effects. Also, fundamental nuclear properties such as moments, spins and charge radii are unknown for most of these nuclei. Thus, experimental data are crucial to test and improve the predictions of state-of-the-art atomic and nuclear theoretical models.
The Radiation Detection Resonance Ionization Spectroscopy (RADRIS) setup, at the GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt, has recently provided such experimental data for nobelium and fermium isotopes [1, 2]. The RADRIS data, however, are limited in the attainable spectral resolution mainly owing to collision- and Doppler-broadening effects. To overcome these limitations the JetRIS setup [3] has been designed to perform laser spectroscopy in a low- density and low-temperature supersonic gas jet [4] produced by a convergent-divergent contoured nozzle installed at the gas cell exit [5,6]. The performance of JetRIS has been tested online with the spectroscopy of 254No, showing a six-fold increase in spectral resolution with respect to the RADRIS data.
In this contribution we will present the research and development work carried out to commission
the JetRIS setup as well as its performance in the last online campaign and the prospects.

[1] M. Laatiaoui et al., Nature 538, (2016) 495–498
[2 S. Raeder et al., Phys. Rev. Lett., 120 (2018) 232503
[3] S. Raeder et al., NIMB 463, (2020) 272–276
[4] Yu. Kudryavtsev et al., Nucl. Instrum. Methods Phys. Res. B, 297 (2013) 7-22
[5] R. Ferrer et al., Phys. Rev. Res., 3 (2021) 043041
[6] D. Muenzberg et al., Atoms 2022, 10(2), 57

Laser spectroscopy research into heavy actinides has been garnering interest in recent years, as experimental techniques advance and become applicable in studies of even heavier species. These studies are, however, complicated by the low production cross sections and short half-lives of the isotopes of interest.
The In-Gas Laser Ionization and Spectroscopy (IGLIS) technique has been a mainstay in laser spectroscopy studies of the heavier elements. In particular JetRIS is designed for high-efficiency, high-resolution resonant ionization spectroscopy studies with target to detector transport times in the range of hundreds of milliseconds. The working principles of the technique are to stop the fusion evaporation products in a gas cell, transport the thermalized ionic species via electrostatic potentials and gas flow to a tantalum filament, where they are adsorbed and subsequently desorbed as neutrals and carried into the low pressure and low temperature hypersonic gas jet, where the atoms are laser ionized.
In the 2022 beamtime at GSI the JetRIS experiment was commissioned and produced its first results. The experiment was successful in producing spectra of nobelium (254No) with a seven-fold improved resolution compared to conventional gas cell experiments, thus establishing the viability of the technique, however with a low overall efficiency (of the order of 0.1 %).This calls for detailed simulation studies of the gas cell to try to understand the system and improve its performance.
The current work presents an extensive model created in the COMSOL simulation environment, the benchmarks of this model against experimental data and simulations of the impact potential modifications will have on the system’s performance.

Laser spectroscopy is one of the pillars of nuclear-physics research with radioactive ion beams, allowing to determine mean-square charge radii, spins and electromagnetic moments of nuclear ground states and isomeric states from the lightest to the heaviest nuclei currently produced. These observables, in turn, play an essential role in the interpretation of nuclear structure and the development of state-of-the-art nuclear models. Consequently, laser-spectroscopy setups are important components of low-energy-physics programs at accelerator facilities, either operational or under construction.

The main challenge of laser spectroscopy with radioactive isotopes is to reach the required sensitivity in terms of count rate, due to minute production rates and unwanted background, and in terms of spectral resolution, due to the goal of quantifying isotope shifts and hyperfine structures which give access to the nuclear properties. This double challenge has motivated the development of a whole range of laser-spectroscopy approaches. Some aim to probe atoms as closely as possible to the production or stopping point, despite having to deal with unwanted spectral broadening mechanisms. Others rely on a complex preparation prior to the laser-atom interaction, allowing high spectral resolution, but suffering inherent efficiency losses. Finally, a whole new set of techniques, such as in-gas-jet laser spectroscopy (for gas-catcher-based setups) or perpendicular-ionization in-source laser spectroscopy (for hot-cavity-based setups) [2] aims to achieve an acceptable compromise of both worlds. In addition, the coupling of laser-spectroscopy setups to mass spectrometers was shown to greatly boost count-rate sensitivity [3].

This contribution will give an overview of some of the state-of-the-art approaches in the stopping and manipulation of radioactive isotope at accelerator facilities with the purpose of laser spectroscopy. Some of the main themes driving current developments will be discussed, with examples from existing laboratories.

[1] Yu. Kudryavtsev et al., Nucl. Instr. Meth. B 297, 7–22 (2013)
[2] R. Heinke et al., Hyperfine Interact. 238, 6 (2017)
[3] B. Marsh et al., Nucl. Instr. Meth. B 317, 550–556 (2013)

S3LEB (Super Separator Spectrometer-Low Energy Branch) is a low energy radioactive ion beam facility, which will be employed for the study of exotic nuclei, under commissioning as a part of GANIL-SPIRAL2 facility [1]. High intensity primary beams, delivered by the superconducting LINAC of the SPIRAL 2 facility, will allow for increased production rate for nuclear fusion evaporation reaction thus will facilitate exploration of the heavier regions of the nuclide chart with low production cross section and shorter lifetime. The produced ions will be separated by the recoil separator S3 and will be send to the S3LEB facility at the focal plane of S3 [2].
S3LEB is a gas cell setup followed by radiofrequency quadrupole units, which allows selective ionization of radioactive ions of interest as well as efficient transmission of the ions to an MR-TOF (Multi-Reflection Time of Flight separator) for further beam purification and detection. The ions thermalized and neutralized inside the buffer gas cell are selectively laser ionized either inside the gas cell or in a hypersonic gas jet environment created after the gas cell using a De-Laval nozzle. First offline results from S3LEB commissioning were published recently presenting the commissioning of laser systems and conditions for optimum operation of the ion guiding and mass selection RFQs using an alkali source [3].
Here we present the progress in the offline commissioning of the S3LEB setup highlighting the first laser spectroscopy test results with the coupling of gas cell to the system and its transmission through ion guides to the MR-TOF spectrometer. For the commissioning tests, a tantalum filament was installed in the gas cell for the production of stable isotopes of Er, one of the day 1 experiment case. Characterization of the laser ions in the gas cell setup has been performed. We also report a systematic study of the cooling and buncher RFQ parameters for optimized conditions in terms of relative transmission efficiency and resolution in time.
Finally, the road map to online commissioning will be presented.
References:
[1] A.K.Orduz, 31st Linear Accelerator Conference, Aug 2022, Liverpool, UK , URL: https:// doi.org/10.18429/JACoW-LINAC2022-TU2AA02
[2] F. Déchery et al., Eur. Phys. J. A 51, 66 (2015), URL: https://doi.org/10.1140/epja/i2015-15066-3
[3] J.Romans et al., Atoms, 10, 21 (2022) URL : https://doi.org/10.3390/atoms10010021

The new SPIRAL2 facility with its Super Separator Spectrometer (S$^3$) at GANIL is set to produce record intensities of neutron-deficient isotopes close to the proton dripline [1]. The products will be stopped and neutralized in the gas cell of the S$^3$ Low Energy Branch (S$^3$-LEB) [2,3], then extracted and studied by laser spectroscopy, mass spectrometry and decay spectroscopy. The extraction time of the S$^3$-LEB gas cell is on the order of a few hundred milliseconds, which will cause significant losses for isotopes with half-lives below 100 ms. The neutralization efficiency is contingent upon the number of electrons extracted from the buffer gas by the incident beam during the stopping process, which is heavily reliant on the beam intensity. The FRIENDS$^3$ project [4] aims to design a fast gas cell with an efficient neutralization technique in order to enable nuclear-structure studies by laser spectroscopy on short-lived isotopes.

The prototype performance was simulated under different operating pressures using COMSOL [5] and SIMION [6]. Detailed simulations of the neutralization process are also ongoing using the COMSOL Plasma module.

Neutralization tests have begun using a simplified test bench. First, studies have focused on electron generation by different mechanisms, such as emission from a filament and ionization of the gas by a beta source.

This contribution will give an update on the progress of the project. The first simulation and design studies of the FRIENDS$^3$ prototype and the preliminary test results with the simplified test benches will be presented.

1. F. Déchery, et al., Nucl. Instrum. Meth. B 376, 125 (2016).
2. J. Romans, et al., Atoms 10, 21 (2022).
3. J. Romans, et al., Nucl. Instrum. Meth. B 536 (2023).
4. V. Manea, et al., ‘Fast radioactive ion extraction and neutralization device for s$^3$’, project ANR-21-CE31-0001 (2021).
5. COMSOL Multiphysics® v. 6.1. www.comsol.com. COMSOL AB, Stockholm, Sweden.
6. D. A. Dahl, Int. Jour. Mass Spectrom. 200, 3 (2000).

The energy of the first-excited nuclear state of Thorium-229 ($^{229m}$Th) is so low that it can be excited from the ground state by a vacuum ultraviolet laser. One of the applications is a nuclear clock: an atomic clock based on the nuclear transition between the ground state and $^{229m}$Th. An ion trap is an optimal system for the nuclear clock because the quantum states of the $^{229}$Th ion in a trap can be precisely controlled by laser cooling.
We developed an RF carpet gas cell to obtain a low-energy $^{229}$Th ion beam which was used as an ion source for our ion trap experiment. The $^{229}$Th recoil ions emitted from $^{233}$U were cooled by collisions with a helium buffer gas and extracted as a low-energy ion beam by an RF carpet. Since 2% of recoil $^{229}$Th ions from $^{233}$U is $^{229m}$Th, laser spectroscopy of trapped $^{229m}$Th ions can be performed by attaching the ion trap to the gas cell developed in this study. Such measurements provide more detailed knowledge of this unique nuclear state. In this presentation, we present details on our experiments on trapping and laser spectroscopy of triply charged thorium ions.

The HITRAP facility, located at the GSI Helmholtzzentrum für Schwerionenforschung GmbH in Darmstadt, Germany, is designed to decelerate, cool and transport heavy, highly charged ions (HCI) created by the GSI accelerator complex to various attached experiments. The system consists of a two-stage deceleration structure, an interdigital H-type linac (IH) and a radio-frequency quadrupole (RFQ), followed by a cryogenic Penning-Malmberg trap for subsequent ion stopping cooling. The deceleration stages reduce the ion energy from initially 4$\,$MeV/u to 500$\,$keV/u and to 6$\,$keV/u respectively, before forwarding a slow, but hot ion bunch towards the cooling trap.
The trap is operated in a so-called nested configuration, in which the electrons, created by an external photo-electron source, are stored simultaneously with ions and serve as cold thermal bath. Via Coulomb interactions the ions transfer their energy to the electrons, which continuously dissipate energy via synchrotron radiation, due to their circular motion in the strong magnetic field of the trap.
After cooling, a low-energy transfer beamline allows the transport and delivery of those ions towards users at different experiments. A Dresden EBIT, attached to the beamline, is used for commissioning of the cooling trap as well as a source of light HCI for some experiments.
So far, deceleration of heavy HCI has been set up down to 6$\,$keV/u, though the process is somewhat hampered by a low delivery rate of one ion bunch per 40 seconds. The subsequent electron cooling process is under development with promising results. A routine operation of the transport beamline is set up and light ions are transported from the EBIT towards the cooling trap. There they are regularly stored and mixed with electrons. An interaction between them has been verified, however a clear cooling effect could not be observed so far. The current status of this development as well as future aspects will be presented.

Thorium isotopes became of high interest in the search for fundamental physics and for testing of the standard model of particle physics because of their unique nuclear and atomic properties [1,2]. In the project Trapping And Cooling of Thorium Ions via Calcium (𝑇𝐴𝐶𝑇𝐼𝐶𝑎), ion trapping and spectroscopic techniques are developed for a precise determination of nuclear moments, hyperfine intervals, and isotope shifts with different Th isotopes [3]. Two methods are used to produce atomic thorium ions, i. e., laser ablation of macroscopic thorium samples [3] and thin layers of alpha-decaying uranium isotopes which produce thorium daughter nuclei that recoil from the sample with the momentum imparted by the alpha decay [4]. While the former process yields predominantly singly charged ions, the latter also leads to substantially more highly charged ions [4]. Within this project, laser ablated thorium-232 ions were trapped in a linear Paul trap [3], a recoil ion source providing electrostatically decelerated Th ions [4] has been built and commissioned, and an apparatus for systematic studies of the laser-ablation production of atomic and molecular Th ions has been developed.
Laser ablation and in-flight reactions are used for the production of molecular thorium ions. Molecules including ThF [5] are of interest in the search for scalar dark matter [6] and could be used as quantum sensors to search for CP violations [7]. For this, further experiments are aimed at investigating the laser ablation behavior of different thorium isotopes in salt-based form and the formation and delivery of different thorium molecules from chemically different Th samples.

[1] V. V. Flambaum, Physical Review Letters 97, 1–3 (2006).
[2] V. V. Flambaum et al., Physical Review A 97, 1–12 (2018).
[3] K. Groot-Berning et al., Phys. Rev. A 99, 023420 (2019)
[4] R. Haas et al., Hyperfine Interact. 241, 25 (2020)
[5] V. V. Flambaum, Phys. Rev. C 99, 35501 (2019).
[6] D. Antypas et al., Quantum Sci. Technol. 6, 034001 (2021).
[7] N. R. Hutzler et al., https://arxiv.org/abs/2010.08709 (2020).

Neutron-capture cross-sections of radioactive neutron-rich isotopes have a wide impact on nuclear reactions and nuclear structure. They also impact nuclear astrophysics studies. Measurement of these cross-sections is currently considered impossible due to the instability of the targets and projectile.

We propose a method to overcome this limitation. We plan to stop and thermalise fission fragments in a cryogenic stopping cell. These fragments will then form a cooled low-energy beam transported into an RF trap system (coined ‘NG-Trap’ [1]). An intense neutron beam will consequently irradiate this trapped ‘cloud target’. The reacted ions will be mass-selected, identified and counted using a multiple-reflection time-of-flight mass-spectrometer (MR-TOF-MS), thus extracting (n,γ) cross-sections.

This talk will present a triple-RFQ system [2] currently operating at Tel-Aviv University to research and develop the cloud target concept. This system is the first step in designing the NG-Trap system that will be installed at the Soreq Applied Research Accelerator Facility (SARAF) [3], currently under construction in Yavne, Israel.

[1] T. Dickel et al., EPJ Web of Conferences 260, 11021 (2022)
[2] E. Haettner et al., Nucl. Instr. Meth. A 880, 138 (2018)
[3] I. Mardor et al., Eur. Phys. Jour. A 54: 91 (2018)

The IGISOL facility has been actively involved in nuclear physics research for over three decades [1]. The facility utilizes beams from a K-130 cyclotron to produce low-energy ion beams for nuclear ground-state studies. The main fields of research are precision Penning-trap -based mass measurements and trap-assisted decay spectroscopy, collinear laser spectroscopy, and development of in-source laser spectroscopic methods and instruments.
The advances in Penning trap techniques, combined with efficient inductively heated hot cavity catcher laser ion source (HCLIS), have enabled ultra-sensitive Phase-Imaging Ion-Cyclotron-Resonance (PI-ICR) assisted in-source RIS [2]the N=Z in the immediate region below ¹⁰⁰Sn. This novel combination of techniques was used to cross the N=50 shell closure near ¹⁰⁰Sn for the first time with the charge-radii measurement of ⁹⁶Ag. Since then, the measurements have been extended to ⁹⁵Ag, with the immediate goal being a direct mass measurement of ⁹⁴Ag. The utilization of the setup for producing proton rich Pd, Cd, In and Sn is also being investigated.
In this talk we will discuss the development of the HCLIS, the recent results and the near future aims.
[1] J. Äystö et al., Three decades of research using IGISOL technique at the University of Jyväskylä.: Springer, 2014.
[2] M. Reponen et al., "Evidence of a sudden increase in the nuclear size of proton-rich silver-96," Nat. Comm., vol. 12, no. 4596, 2021.

Investigating the boundaries of the nuclear chart and understanding the structure of the heaviest elements are at the forefront of nuclear physics. The existence of the superheavy nuclei is intimately linked to nuclear shell e?ects which counterpart Coulomb repulsion and therefore hinder spontaneous ?ssion. Moreover, heavy and superheavy nuclides feature of-ten metastable excited states with half- lives that can exceed the one of the ground state.

Long-lived isomeric states can have excitation energies of only few tens of keV or below, therefore their identi?cation is challenging, especially in decay-based measurements. On the other hand, Penning trap mass spectrometry can provide su?cient resolving power to allow the separation of isomeric states when they are populated in the same reaction as theground state. Direct high-precision mass measurements provide also indispensable knowledge on binding energies, shell strength and yield important anchor-points on α-decay chains, constraining absolute mass values of the more exotic heaviest nuclei.

The SHIPTRAP spectrometer at GSI Darmstadt, Germany has shown that direct high-
precision mass measurements of 102No and 103Lr isotopes around the deformed shell closure N = 152 are feasible. Thanks to several improvements in the ion preparation with the implementation of a second-generation gas-stopping cell operating at cryogenic temperatures and the development of the Phase-Imaging Ion-Cyclotron-Resonance (PI-ICR) technique which boosts the sensitivity of mass measurements, the investigation of 251No, 254Lr and the superheavy nuclides 257Rf and 258Db were performed in the latest experimental campaigns with rates down to one detected ion per day.

Despite lowest rates, the PI-ICR technique allowed operating with a mass resolving powers of up to 107 and accurately determining the excitation energies of the 251m,254mNo, 254m,255mLr, and 257mRf isomeric states which had
previously been derived only indirectly via decay spectroscopy. The overall e?ciency of the setup have been improved and its stability over extended measurement times tested.

In this contribution an overview of the technical developments and the recent experimental campaigns will be presented.

Different kinds of buffer gas cells find many applications for the thermalization of fast multi-charged ions and their extraction as secondary ion beams [1-3], also for studies of the heaviest elements [4]. Commonly, high vacuum conditions are needed downstream of the cell for further applications of the secondary ion beams. A universal high-pressure gas cell UniCell [5] was proposed recently, to be applied in physics and chemical studies of superheavy elements. Chemical studies are usually performed by the gas chromatography method at a pressure of up to 1 bar, with a narrow chromatography channel being formed by silicon detector arrays [6]. Thus, interfacing between UniCell and the detector channel requires effective transport of ions driven by the gas flow. Such a device, the Ion Transfer by Gas Flow (ITGF) device, was proposed and studied by COMSOL [7] simulations. The ITGF device is an RF-only gas channel, along which the cross section changes smoothly from the circular UniCell exit to the slit-like entry into the chromatography channel. The ITGF thus serves for an efficient ion extraction, and prevents collisions of ions with the wall. Our work numerically investigates this new ion transfer device in combination with UniCell. Parameter optimization were performed by COMSOL simulations; optimized settings suggest a fast (∼a few ms) and highly efficient (up to 100%) extraction of ions in a wide mass range from UniCell as well as their quantitative transmission through the ITGF into the high pressure environment specific for chemical studies.

References
[1] F. Schlottmann, M. Allers, A.T. Kirk et al., J. Am. Soc. Mass Spectrom. 30, 1813-1823 (2019).
[2] M. Ranjan, P. Dendooven, S. Purushothaman, et al., Nucl. Instrum. Meth. A 770, 87-97 (2015).
[3] G. Savard, A.F. Levand, B.J. Zabransky, Nucl. Instrum. Meth. B 376, 246-250 (2016).
[4] O. Kaleja et al., Nucl. Instrum. Meth. B 463, 280-285 (2020).
[5] V. Varentsov and A. Yakushev, Nucl. Instrum. Meth. A 940, 206-214 (2019).
[6] A. Yakushev et al., Front. Chem. 10, 976635 (2022).
[7] COMSOL, https://www.comsol.com

S. Malbrunot-Ettenauer for the RadMol and MIRACLS collaborations

Ion traps have long been recognised as superb precision tools for fundamental physics research. Thanks to their extraordinary versatility, they have repeatedly opened up new science opportunities which in turn have led to remarkable advancements in ion-trap technology. As one example in the field of rare isotope science, the MIRACLS and recently-formed RadMol collaborations are developing new methods in ion trapping and manipulation to study radioactive molecules and (negative) ions.

Radioactive molecules, in which one or more of its constituting atoms contain a short-lived radioactive nucleus, have recently been introduced as highly sensitive probes for new physics beyond the Standard Model of particle physics. However, radioactive molecules are challenging to address experimentally. In addition to the short half lives, radioactive samples are only available in minute quantities at dedicated radioactive ion beam (RIB) facilities where they are typically synthesised in ‘hot’ environments. To overcome these challenges, we have pursued a series of ion-trap experiments at ISAC@TRIUMF and ISOLDE@CERN with the goal to efficiently form (ionic) molecules of interest and cool them to temperatures adequate for future precision experiments.

In this talk, recent advances at RadMol and MIRACLS dedicated to the research on radioactive molecules will be presented. Among others, these include the formation of molecules or their sympathetic cooling via co-trapped and laser cooled ions, both achieved in cooler-bunchers commonly available at modern RIB facilities. Closely related instruments have also been exploited to study negative ions and, thus, to enhance the signal sensitivity of laser photodetachment threshold spectroscopy as required for the precise determination of electron affinities. Building on these techniques, a prospect for future precision experiments with radioactive molecules and negative ions with low production yields will be given.

Progress towards the EDM3 instrument at FRIB: A tool for studying radioactive molecules embedded inside cryogenic solids

J. Ballof
Facility for Rare Isotope Beams, Michigan State University, East Lansing, MI 48824, USA

The study of radioactive molecules receives increasing attention due to their enhanced sensitivity to fundamental symmetry violations and Beyond Standard Model physics. In particular, 225RaF has been proposed as powerful probe due to its enhanced Schiff-moment. While the principle advantage of such systems is known for more than 30 years [1], the progress in the field relies on the development of novel instruments and the availability of suitable radioisotopes. At the Facility for Rare Isotope Beams (FRIB), the latter is being addressed by development of isotope harvesting techniques [2].

Within this contribution, we introduce the in-design FRIB-EDM3 instrument. The setup was designed to study polar radioactive molecules (like RaF) in transparent cryogenic solids by laser spectroscopy with the EDM3-method [3]. The efficient ionization of harvested radioisotopes from aqueous phase is pursued with a spray-ionization method [4]. Subsequently, the molecular ion beam is analyzed by mass-to-charge ratio by a quadrupole mass filter and neutralized in a charge-exchange cell before its implantation in a solid argon matrix. We will present the design of the instrument and report on the progress of its construction.

This work is supported the U.S. DOE, Office of Science, Office of Nuclear Physics, under contract DE-SC0019015.

1. T.A. Isaev et al., Lasercooled radium monofluoride: A molecular all-in-one probe for new physics (2013), https://arxiv.org/abs/1302.5682.
2. E.P. Abel et al., J. Phys. G: Nucl. Part. Phys. 46, 100501 (2019).
3. A. C. Vutha et al., Phys. Rev. A 98, 032513 (2018).
4. R.T. Kelly et al., Mass Spectrom. Rev. 29, 294 (2010).

The NEXT collaboration is pursuing a phased program to search for neutrinoless double beta decay of 136Xe using high pressure xenon gas time projection chambers. In addition to the capabilities of precise calorimetry and topological imaging, xenon gas detectors also offer a further opportunity: the plausible implementation of barium daughter ion tagging. In this talk I will present advances in the development of barium tagging in high pressure xenon gas, with a focus on R&D toward single ion manipulation and imaging. Topics to be covered include methods for concentrating ions to sensors via high pressure RF carpets, advances in single ion microscopy in high pressure gas, recent developments in chemical ion sensing technology, and proposed demonstrator detectors that aim to prove the technique with double beta decays, potentially unlocking new levels of sensitivity to the Majorana nature of the neutrino.

A system is being developed to extract from liquid xenon into vacuum and subsequently identify the Xe-136 double-beta decay daughter isotope Ba-136. The system will consist of several devices starting with a capillary to transport the ion from liquid into a gas volume followed by a RF-only ion funnel to extract the ion to vacuum while recapturing the Xe gas for future use. Afterwards, the ion will be trapped in a linear Paul trap and identified via laser fluorescence spectroscopy. A Multi-Reflection Time of Flight mass spectrometer will verify the ion’s mass A=136 and support ion-extraction studies during the development phase. Different ion sources are also being developed, in particular an accelerator-based in-liquid Xe Ba-ion source.

This approach of ion extraction and identification is intended for a potential future upgrade to the neutrinoless double-beta decay (0νββ) experiment nEXO which will deploy 5 tonnes of liquid Xe enriched in the isotope Xe-136. An individual identification of the ββ-decay product allows for an ideally background-free measurement by vetoing naturally occurring gamma and beta backgrounds. This identification increases the experiment’s sensitivity to 0νββ and offers an unambiguous identification in case of a positive 0νββ signal.

In this presentation the various ion-transport methods under investigation will be discussed along with the status of their developments.

Daler Amanbayev1, S. Ayet2, D. Balabanski3, S. Beck1, J. Bergmann1, P. Constantin3, T. Dickel1,2, H. Geissel1,2, T. Grahn4,5, L. Gröf1, E. Haettner2, M. Harakeh6, C. Hornung1, N. Kalantar-Nayestanaki6, G. Kripko-Koncz1, I. Mardor7,8, I. Miskun1, A. Mollaebrahimi1,10, I. Moore4,5, W. R. Plaß1,2, I. Pohjalainen4, S. Purushothaman2, M. P. Reiter9, A. Rotaru3, C. Scheidenberger1,2, A. Spataru3, A. State3, A. Zadvornaya1.

1 - Justus-Liebig-Universität Gießen, 2 - GSI Helmholzzentrum für Schwerionenforschung, Darmstadt, Germany, 3 - IFIN-HH/ELI-NP, Magurele, Romania, 4 - University of Jyväskylä, Finland, 5 - Helsinki Institute of Physics, Helsinki, Finland, 6 - ESRIG, University of Groningen, The Netherlands, 7 - TAU, Tel-Aviv, Israel, 8 - Soreq NRC, Yavne, Israel, 9 - University of Edinburgh, UK, 10 - TRIUMF, Vancouver, British Columbia, Canada.

A cryogenic stopping cell (CSC) for the Super-FRS [1] at FAIR has been developed to enable fast and efficient thermalization of intense beams of short-lived nuclides produced at relativistic energies of up to 1.5 GeV/u.
It features a novel high areal density two-stage orthogonal extraction (HADO-CSC) concept [2] that allows achieving the unprecedented design performance parameters required to take full advantage of the Super-FRS. Combined with the multiple-reflection time-of-flight mass-spectrometer (MR-TOF-MS) [3], the CSC is part of the Early and First-Science programs of FAIR as a setup for the measurement of beta-delayed neutron-branching ratios, high-accuracy mass measurements and reaction studies. Furthermore, it will be a key device to enable the scientific programs of MATS [4], LaSpec [5] and the Super-FRS Experiment Collaboration [6] at the low-energy branch of the Super-FRS.
This contribution presents the status of the project and technical developments including helium recovery unit (HRU) and test chamber for the RF carpets. Furthermore, it presents recent experimental results obtained with the prototype CSC [7] at the FRS Ion Catcher [8] which validate the selected design concepts.

References:
[1] H. Geissel et al., NIM B 204 (2003) 71
[2] T. Dickel et al., NIM B 376 (2016) 216
[3] W.R. Plaß et al., Phys. Scr. 014069 (2015) T166
[4] D. Rodriguez et al., Int. J. Mass Spectrom. 349 (2013) 255
[5] W. Nörtershäuser et al., Hyperfine Interact. 171 (2006) 149
[6] J. Äystö et al., NIM B 376 (2016) 111
[7] I. Miskun, PhD Thesis, JLU Gießen (2019)
[8] W. R. Plaß et al., Hyperfine Interact 240 (2019) 73

Using low-energy antiprotons, the antiProton Unstable Matter Annihilation (PUMA) experiment [1] aims to probe the isospin composition in the density tail of radioactive nuclei. For this purpose, the isotopes of interested are trapped together with the antiprotons in a dedicated Penning trap. By measuring the charge of the particles emitted as a result of the annihilation reaction, the experiment provides the neutron-to-proton annihilation ratio as a new observable for nuclear structure theory. It allows to investigate neutron skin formation of neutron-rich nuclei as well as halo nuclei.

Before radioactive isotopes are studied, the experimental technique is first applied to stable nuclei, including the investigation of the proton-to-neutron content on the surface of 208Pb [2] or its evolution in the chain of stable tin and xenon isotopes. Therefore, a versatile offline ion source has been developed to generate isotopically pure and cooled ion bunches of about 10$^{5}$ particles. A multi-reflection time-of-flight mass spectrometer (MR-ToF MS) [3] and a linear Paul trap are integrated downstream the ion source region. They are used for mass separation, ion accumulation, and cooling before the ion bunches are injected into the PUMA Penning trap, loaded with antiprotons.

The status of the offline ion source beamline and first measurements to determine the ion bunch properties after the ejection from the MR-ToF MS and Paul trap will be shown.

[1] PUMA Collaboration, PUMA, antiProton unstable matter annihilation. Eur. Phys. J. A 58, 88 (2022)

[2] PREX Collaboration, Measurement of the neutron radius of 208 Pb through parity violation in electron scattering. Phys. Rev. Lett. 108, 112502 (2012)

[3] R. N. Wolf et al., ISOLTRAP’s multi-reflection time-of-flight mass separator/spectrometer. Int. J. Mass Spectrom. 349-350, 123–133 (2013)

A brief overview and summary of the present conference will be presented.