SPARC Topical Workshop 2016

It will be presented the COST action "Fundamental Parameters for Interactions of X-rays with Matter" submitted on April 2016. This action was supported by colleagues of nine european countries, including several members of the SPARC collaboration, and aims to establish an European network of the atomic physicists.

While quantum electrodynamics (QED) is usually referred to as the most accurately tested theory, its validity for electrons in very strong fields is still not tested with high accuracy. The strongest magnetic fields available in the laboratory are experienced by electrons in the groundstate of highly charged heavy ions which can be probed by hyperfine spectroscopy. Even though the ground state hyperfine transition in hydrogen-like bismuth was observed already in 1994 [1], the significance of the experiment as a test for QED was limited by the unknown magnetic moment distribution inside the nucleus. However, it was suggested that a so-called specific difference between the hyperfine splittings in hydrogen-like and lithium-like ions of the same isotope can be used to cancel nuclear structure effects and provide an accurate test of QED [2]. The transition in Li-like Bismuth was observed for the first time in 2011 at the Experimental Storage Ring ESR located at the GSI Helmholtzzentrum f¨ur Schwerionenforschung in Darmstadt [3]. Yet the accuracy of the result was limited by the calibration of the electron cooler voltage, determining the ion velocity. Here, we report on improved laser spectroscopic measurements of the hyperfine splittings in hydrogen- and lithium-like bismuth ions (209Bi82+ and 209Bi80+) at the ESR. The accuracy was improved by about an order of magnitude compared to the first observation in 2011 [3]. The most important new feature was an in-situ high voltage measurement system with an accuracy at the 10-ppm level provided by German metrology institute Physikalisch-Technische Bundesanstalt. As the dominant systematic effect, the space charge effect of the electron cooler current on the ion velocity was determined with two independent techniques that provided consistent results. We will discuss systematic effects, present the measured transition energies of both hydrogen- and lithium-like bismuth and show the experimentally determined value for the specific difference in 209Bi. References [1] I. Klaft et al. Phys. Rev. Lett 73, 2428 (1994) [2] V. Shabaev et al., Phys. Rev. Lett. 86, 3959 (2001) [3] M. Lochmann et al., Phys. Rev. A 90, 030501 (2014)

Precision spectroscopy of highly charged ions provides a powerful tool to study many unexplored realms of physics, shedding light on many astrophysical, quantum electrodynamic, atomic collision and spectroscopic mysteries. X-ray spectra of various supernova remnants, obtained by ASCA and Suzaku observatories provided conclusive evidence of H- and He-like Si, S, Ar, Ca and Fe ions[1]. The x-rays of H-, He- and Li-like Fe have been observed in solar flares and studied with tokmak plasmas. The transition energies and lifetime measurement provide a testing ground for understanding of wave function of atomic systems. Beam-foil spectroscopic technique is one of the most elegant tools to study highly charged ions for the measurement of both transition energies and lifetime. However this technique suffers from inherent cascading and blending problem. If the level under study is repopulated by the decay of higher levels, then this is called cascading effect. Cascading problem is inherent to BFS, and hence independent of detectors spectral resolution. On the other hand the presence of nearby transitions (below the detector resolution i.e. ~150 eV at 5.9 keV) in same ion species causes intra-ion blending, where as similar transitions from neighbouring ion species give rise to inter-ion blending also called satellite blending. In contrast to the problem imposed by cascading effect, intra-ion and inter-ion blending effect imposes problem due to experimental limit of detector resolution. To eradicate this problem, we have designed and developed high resolution multi channel Doppler tuned spectrometer (MCDTS) setup coupled with high precision foil movement system at IUAC New Delhi [2]. A beam of 165 MeV 56Fe12+ ions from the 15 UD Pelletron accelerator at IUAC, New Delhi was used in this experiment. When a well focussed beam interacts with 100 µg/cm2 thin Carbon foil, various electron stripping and capture process take place, which produce the excited H-, He- and Li-like Fe ions. We have resolved the 1s2s 3S1 – 1s2 1S0 (M1) transition in He-like Fe from its satellite 1s2s2p 4P05/2 – 1s22s 2S1/2 (M2) transition in Li-like Fe with reasonably high precision by using MCDTS setup energetically, obtained to be 6636.0 ± 4.3 eV and 6619.9 ± 5.4 eV, respectively. Further the lifetime of 1s2s2p 4P05/2 level has been measured with high precision foil-movement system, comes out to be 76 ± 1.7 ps. The details of such measurements along with setup will be presented. Keyword: Highly Charged Ions, x-ray, Metastable Transitions, Doppler Tuned Spectrometer References [1] D. F. Gonzlez et. al. Astrophysics J. Lett. 781, L26 (2014). [2] Ranjeet K. Karn et. al. Rev. of Sci. Instrum. 85, 066108 (2014).

Collisional interaction of fast ions with large biomolecules, PAH and fullerenes is an active field of research which is not only important for the development of theoretical models for collisional aspects in many body systems but also for its application towards the modeling of radiation damage and astrophysical absorption spectrum in VUV region. There has been some distinct progress in the study of ionization and fragmentation of large biomolecules in last decade. This progress is reflected in experiments as well as in the theoretical modeling. The secondary electron emission from nucleobases and water is an important parameter to estimate the radiation damage caused by the fast ions. Besides keV and a few MeV protons, we have recently pushed this field by using highly charge heavy ions (C, O, F and Si) as projectiles in the energy range of ~100 keV to ~100 MeV i.e. across the Bragg peak of energy loss. A recently installed 14.5 GHz ECR based ion-accelerator on 400 kV deck and the existing 14 MV Pelletron tandem accelerator in TIFR, Mumbai are being used to investigate these aspects. The targets are uracil, bromouracil and adenine, besides water molecule. In particular the angular distribution and angular asymmetry in the electron double differential cross sections and total ionization cross section in case of water [3,5] or biomolecules provides a very crucial input regarding the many-body aspects. The dramatically large forward backward asymmetry in electron emission for uracil compared to small molecules indicates some kind of many-body or size effect. Many body effect, such as a collective plasmon resonance has been observed in C-based molecules, coronene and fullerene and such plasmon resonance accounts for nearly half of the ionization yields. The best known quantum mechanical model although comes closer to the water data at high energies, at intermediate energies it fails. Inclusion of transfer-ionization mechanism improves the agreement with a suitable scaled model. A large and unusual enhancement in e-emission from a BrU bio-molecule over uracil has also been quantitatively determined now. The detailed data for these molecules has been used to develop a scaling rule of ionization cross section for water and uracil in terms of velocity and charge states, which will have input for the model calculation for radiation damage at hadron therapy. Details will be presented based on the results in our group along with some occasional references from the work done elsewhere. e-mail: lokesh@tifr.res.in; ltribedi@gmail.com

High-precision X-ray spectroscopy of highly-charged heavy ions is one of the established subjects within the program of SPARC. To improve the precision of such experiments, the detector concept of silicon microcalorimeters, which detect the temperature change of an absorber induced by an incoming photon, is now exploited. Silicon microcalorimeters were successfully applied in several experiments at the ESR at GSI. However, for application at FAIR further improvements in detector design and performance are mandatory, namely • larger detector solid angle • combination of absorbers for high x-ray energies around 50–100 keV with absorbers for low x-ray energies around 5–10 keV • improvement in readout electronics and data acquisition . A prototype detector system with a dry 3He/4He dilution refrigerator and an array of 32 detector pixels was installed at the ESR in the recent test beamtime in June 2016. The cryogenic system performed perfectly well. An energy resolution of around 150 eV at a X-ray energy of 30 keV was obtained, which allowed the observation of Lyman-alpha emission from hydrogen-like xenon ions with high precision. The contribution will present first results of the analysis from this test as well as perspectives for further improvements, in particular towards a detector with an increased solid angle and 100 detector pixels.

High precision x-ray spectroscopy of heavy highly charged ions provides an excellent tool for a test of the most advanced theories describing the atomic structure in the regime of extreme field strengths. These theories take into account quantum electrodynamic (QED) corrections of higher orders and the structure of the atomic nucleus. In this contribution, we present the experiment where the Lyman-α and -β transitions in hydrogen-like gold (Au78+) were measured for the first time with a high-resolution twin crystal spectrometer FOCAL [1] at the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt, Germany. The measurement was carried out at the experimental storage ring (ESR) by colliding initially bare Au ions with an argon gas target at a velocity of 0.47 c, where c denotes the velocity of light. After single-electron capture into an exited state of the projectile ion, radiation is emitted by a decay cascade into the ground state of the ion, part of which is Bragg-reflected on a curved Si crystal in Laue configuration and finally detected by a 2D position sensitive germanium detector. References [1] Beyer H. F. et al., Spectrochimica Acta B 64, 736 (2009)

The energy distribution of electrons emitted in heavy-ion atom collision is a characteristic observable for understanding the underlying charge-transfer processes. Previously, we studied the collision system U88+ + N2 at a projectile energy of 90 MeV/u at the ESR using the magnet forward-angle electron spectrometer [1-3]. For electrons released from the projectile ions in collisions with neutral target atoms, the shape of the electron-loss-to-continuum cusp is not a function of the target atomic number according to first-order perturbation theory, which was applied in ref. [2]. However, for the cusp shape of U28+ ions colliding with different atomic targets, which is relevant for understanding the lifetimes of beams in the heavy-ion accelerators of FAIR, we observed a strong asymmetry of the electron cusp shape that varies significantly with the atomic number of the target [4]. These spectra cannot be explained by current theories. In a recent experiment we therefore compared the cusp-electron spectra of U89+ projectiles colliding with neutral N2 and Xe targets at 76 MeV/u. Amongst others, the experimental results provide tests to theory describing two-center effects in the double-differential cross-sections of projectile ionization of heavy ions [5]. [1] P.-M. Hillenbrand et al., Phys. Rev. A 90, 022707 (2014) [2] P.-M. Hillenbrand et al., Phys. Rev. A 90, 042713 (2014) [3] P.-M. Hillenbrand et al., Phys. Rev. A 91, 022705 (2015) [4] P.-M. Hillenbrand et al., Phys. Rev. A 93, 042709 (2016) [5] A. B. Voitkiv et al., Phys. Rev. A 76, 022709 (2007)

In July 2016, test experiments with stored 12C3+ beams (122 MeV/u) could be conducted at the ESR in Darmstadt, Germany. The same type of ion beam was used in August 2012 for a laser cooling experiment, but then a small admixture (12%) of 16O4+ was present. This time, we had pure carbon ion beams and also with a much higher (~10x) intensity. Inside the vacuum of the ESR, an XUV detector system, developed by the university of Münster, was installed for tests using the fluorescence from the laser-excited ions. For the excitation, two different laser systems have been used, a pulsed system and a scanning cw system. Both laser systems were developed for laser cooling of stored ion beams, and were also to be tested during this beamtime. The pulsed laser system was developed by the TU-Dresden and HZDR, the scanning cw laser system by the TU-Darmstadt. We will present the detector and laser systems used during the test beamtime at the ESR, and will show some of the preliminary data that could be obtained.

Recent modification of the internal target source setup at the experimental storage ring (ESR) led to a significant improvement of its performance. In particular, a reliable operation of the light target gases helium and hydrogen at unprecedented area densities up to values of 10E14 1/cm² was demonstrated [1]. In the course of these optimization efforts, a remarkably versatile target source was established, enabling operation over the whole range of desired target gases (from H2 to Xe) and area densities (~10E10 to ~10E14 1/cm²). For more general, future applications at storage rings a completely new inlet chamber was proposed based on the experience gained during previous modification processes [2]. The much more compact chamber design will maintain the demanding storage ring vacuum requirements while enabling the operation of the target beam at an interaction length down to 1 mm. This is of paramount importance with respect to the realization of high precision experiments, e.g. by reducing the inaccuracy of the observation angle causing the relativistic Doppler broadening [3]. The new inlet chamber design is currently being assembled and commissioned at GSI. A thorough investigation of the exact target properties is mandatory prior to deployment at a storage ring. Experimental results obtained during the commissioning process of the new internal target chamber design will be presented. Further experimental prospects enabled for the first time by the novel multiphase target source will be discussed. [1] M. Kühnel et al., Nucl. Instr. Meth. A 602, 311 (2009) [2] N. Petridis, A. Kalinin and R. E. Grisenti, "Technical Design Report: SPARC-Target@HESR", Stored Particles Atomic Physics Research Collaboration (2014) [3] T. Stöhlker et al., Nucl. Instr. Meth. B 205, 210 (2003)

The approach for the calculation of the binding energies in highly charged ions is presented. The method merges ab initio QED treatment in the first and second orders of the perturbation theory in the fine-structure constant with the third- and higher-order electron-correlation contributions evaluated within the Breit approximation. The nuclear recoil and nuclear polarization effects are taken into account.

The ab initio Lamb shift calculations can be performed only for few-electron atomic systems such as H-like, He-like and Li-Like ions and for many-electron atoms in local density approximation (LDA). For this reason the construction of simple one-electron approach to one-loop QED operator is an important task of the relativistic quantum theory of atoms and molecules described by the Dirac-Breit-Coulomb Hamiltonian. In this work we used the model QED potential [1,2] approach to calculations of the Lamb shift in few-electron quasi-molecules. In particular model QED potential is applied to calculate Lamb shift in the U${}^{91+}$-U${}^{92+}$ dimer. The obtained results are compared with the data of {\it ab initio} calculations [3]. % [1] V.M. Shabaev, I.I. Tupitsyn, and V.A. Yerokhin, Phys.~Rev.~A v. 88, 012513 (2013). [2] I.I. Tupitsyn and E.V. Berseneva, Optics and Spectroscopy v.114, 682, (2013). [3] A.N. Artemyev and A. Surzhykov, Phys.Rev.Lett. v.114, 243004 (2015).

The collision of highly charged, heavy ions with atomic or molecular gas targets or free electrons causes a variety of reactions such as electronic excitation, ionization, radiative electron capture and, in the case of molecules, dissociation. After such a highly energetic reaction, these targets remain in superexcited electronic states which themselves may decay via fluorescence, autoionization into radiative states or dissociation into excited fragments. Typically, these processes are followed by the emission of one or more fluorescence photons in the spectral range from visible light (VIS) to vacuum-ultraviolet radiation (VUV). A Seya-Namioka type spectrometer for the dispersion and detection of this fluorescence in the wavelength range between 35 nm and 180 nm for experiments at gas- and electron targets and electron coolers at the FAIR facility will be set up. The benefit of using a fluorescence spectrometer is the inherent sensitivity of this technique to the charge and electronic states of the target atoms and molecules. Processes to be investigated will be radiative electron capture and dielectronic recombination. In a preliminary measurement, an already existing spectrometer has been used that does not meet the vacuum conditions and was separated by a window, restricting the detectable wavelengths to the visible and near-UV spectral range, however fluorescence spectra from a Xenon gas target, excited with Xe54+ with 50MeV/u could be obtained. During this experiment, the need for a complete remote control of the spectrometer in terms of position adjustment in three dimensions, rotation of the optical grating and the entrance slit turned out to be a requirement for future experiments. A remote-controllable support for the spectrometer has been developed and tested at the ESR Gas Target during operation.

Dielectronic recombination (DR) has been developed as a powerful spectroscopic tool for study of highly charged ions (HCI). The newly twin-electron-beam technique invented at the TSR leads to a significant improvement of the DR experimental energy resolution. The electron beams created from a separate ultra-cold electron target can be much colder as compared to electron-beam produced from the thermal cathode electron gun. In addition, the electron cooler can be used to cool the ion beam continuously during the measurement with the electron-target. Based on the experience of the present DR experiments at the CSRm, the upgrading of the electron cooler (300 kV) of the CSRe for DR experiments with HCI and even radioactive ions is in progress. Moreover, the DR experiment is being planned and designed on the High-Intensity heavy ion Accelarator Facilitiey (HIAF) by combining an electron-cooler and an electron-target at the SRing. The combination of an electron-cooler and an seperate electron-target on HIAF will provide an unique platform for DR experiments of HCI, and will alsoenhance the DR resonance technique to investigate the strong field QED, relativistic effects and nuclear properties. We will present the preparation of the DR experiments at the CSRe and give an overview of the DR experiments plans on HIAF.

One of the goals of Helmholtz Institute Jena with respect to the Facility for Antiproton and Ion Research is to provide highly charged, low-energy ions by using the S-EBIT facility currently being installed at GSI [1]. This is of particular importance during the FAIR construction related shutdown period of the GSI accelerator complex, when little to no beam time can be provided. During this period the S-EBIT shall facilitate research and development works for SPARC experiments at FAIR. This accelerator-independent source of HCI will not only provide ions necessary for R&D of HITRAP [2] experimental stations but also serve as a standalone device for research and R&D activities (e.g. development of x-ray spectrometers, calorimeter detectors, x-ray optics etc. [3]). Furthermore, the combination of S-EBIT with the available laser infrastructure e.g. JETI200 will be a unique platform for the study of highly charged ions subject to intense laser radiation [4] as it is planned at a later stage once the SEBIT facility has been moved to Jena. An overview of the research program as well as the status of the current activities will be presented. References [1] R. Schuch et al., JINST5, C12018 (2010) [2] F. Herfurth et al., Phys. Scr. T166, 014065 (2015) [3] D. Hengstler et al., Phys. Scr. T166, 014054 (2015) [4] M. Vogel et al., Nucl. Instr. Meth. B 285, 65 (2012)

The secondary electron emission from nucleobases and water is an important topic in the contemporary atomic collision physics. Highly charged ion induced ionization, radical emission following fragmentation are important mechanisms in the study of radiation-damage which will have applications in case of hadron therapy. In the present study, the collision energies are made to vary across the Bragg energy loss peak. By using a tandem 14 MV accelerator and an ECR source on a 400 kV deck. In particular the angular distribution and angular asymmetry in the electron double differential cross sections and total ionization cross section for uracil molecule provide some crucial inputs regarding the many-body aspects and also a test of the theoretical models. In the context of tumor cells exposed to high energy ion beams, radio-sensitizers (high atomic number nnoparticles, e.g.) are well known reagents used to increase the killing efficiency of malignant cells. Further, the radiosensitizing properties of halouracils is a subject of theoretical and experimental investigations. Several work have been carried out with halouracils, particularly in studying the fragment products . However, a quantitative study of the enhancement of the electron intensity due to the presence of a nanoparticle in DNA base molecule is missing. In order to get a quantitative estimate of the enhancement we have made complimentary measurements using bromouracil as a target. The details of the energy and angular distributions of the electron emission have been studied using 42 MeV bare C-ions. Unusually large enhancement in e-emission particularly in low energy region (0-50 eV) from the high-Z based BrU molecule has been noticed for all angles. The derived absolute cross sections are compared against a number of theoretical models such as CB1 and CDW-EIS. The studies on involve HCIs of C, O, F and Si of varieties of energy ~keV/u -MeV/u. The detailed data for these molecules has been used to develop a scaling rule of ionization in terms of velocity and charge states, which will have input for the model calculation for radiation damage at hadron therapy. Inclusion of transfer-ionization mechanism improves the agreement with a suitable scaled model. The investigations are carried out using ToF as well as e-spectroscopy based measurements. Some recent references: [1] S. Biswas and L. C. Tribedi, Phys. Rev. A 92, 060701(R) (2015) [2] A. Kelkar et al, Phys. Rev. A 92, 052708 (2015) [3] S. Bhattacharjee et al, J. Phys. B 49 065202 (2016) [4] A. Agnihotri et al, Phys Rev A 87 032716 (2013) [5] S. Nandi et al, Phys Rev A 87, 052710 (2013) [6] L. Tribedi et al, Eur Phys J D 66, 303(2012) [7] A. Agnihotri et al, Phys Rev A 85, 032711 (2012) *e-mail: lokesh@tifr.res.in; ltribedi@gmail.com

Molecular dimers widely exist in planetary atmosphere, and play an important role in molecular and surface physics, astrophysics, and climate. The N2Ar dimer is a typical molecular complex of Ar with N2, which is particularly relevant to the atmosphere of Titan. In the present work, the 1 MeV Ne^{8+} ions were used to produce the (N2Ar)^{3+} ions, the momenta of fragment ions of three-body fragmentation of N2Ar were measured based on the reaction microscopy. Our results indicate that (N2Ar)^{3+} ion can decay from nonsequential dissociation or sequential dissociation. These three mechanisms can be directly distinguished in Dalitz plot and Newton diagrams. In the sequential dissociation processes after single electron loss of Ar site and double electron loss on N2 site, the dimer ion starts to dissociate along the potential energy curve of N2^{2+} + Ar+, the metastable N2^{2+} rotates when it is far away from Ar+ and finally fragment into two N+ ions, the two fine structure appear in Newton diagram. The ring structure indicates the dissociation from the metastable N2^{2+} ions of longer lifetime and the fusiform structure is from the dissociation from the metastable N2^{2+} ions of shorter lifetime.

The HILITE experiment is designed to produce well-defined ion targets, specifically of highly charged ions, and to make them available for studies at high-intensity lasers. It features a cryogenic Penning trap and methods to control the ion cloud composition, size, shape, position and density. Educts and products of the ion-laser interaction can be studied destructively and non-destructively, supporting studies for example of non-linear ionization processes. Besides the capability to capture, store, manipulate and detect ions, we plan to employ the well-defined magnetic field inhomogeneity to transport photoelectrons out of the trap center to a time- and position-sensitive detector which is not irradiated by the laser. We show how this offers the opportunity to measure the momentum of emitted electrons by evaluating the time of flight and the impact position on the detector. The system is currently entering the stage of commissioning, we present the concept, setup and first characterizing measurements.

The well-known existing disparity between the interaction range and the coupling constant for the electromagnetic and the strong force suggests independent treatment of atomic and nuclear phenomena. However, the borderline between atomic and nuclear physics i.e. Coulomb barrier region provides an interesting playground for many basic nuclear and atomic processes which mutually influence each other [1]. The present work is intended to explore the mutual influence of atomic and nuclear interactions on each other using the X-ray spectroscopy technique [2]. The emitted projectile ion X-rays have been measured as a function of the beam energies around the Coulomb barrier regime. Interestingly, the variation of the X-ray centroid energies corresponding to the projectile ionization exhibits an unexpected enhancement below the Coulomb barrier. The sudden increment in the X-ray energy may be explained regarding the interference effects between atomic and nuclear interactions, which occurs due to the recoil of respective nuclei. It results in the initiation of shaking processes which consequently enhance the atomic ionization near the Coulomb barrier. Further, it has been observed that the sudden enhancement due to the nuclei-nuclei interactions occurs slightly below from the theoretical predictions of Coulomb barrier height. It clearly indicates the coupling of elastic channels at sub-barrier energies. The present findings have been validated with three asymmetric collision systems in inverse kinematics heavy ion reactions. Moreover, the work suggests modifications in the theoretical atomic predictions by incorporating the influence of the nuclear effects during the heavy ion induced reactions around the Coulomb barrier. This study may open up new channels for interdisciplinary research comprising of atomic and nuclear physics. References [1] M. S. Freedman, Annu. Rev. Nucl. Sci. 24, 209 (1974). [2] P. Sharma and T. Nandi, Phys. Lett. A 380, 182 (2016).

The photon induced K shell x-ray intensity ratios and the satellite spectra of chlorine are investigated. Unlike conventional use of crystal spectrometers, the satellite x-ray structure is observed using energy dispersive spectrometer with high resolution silicon drift detector and x-ray tube as photon source. The energy shift of chlorine KL1 line from the KL0 position is also measured and found to be ~21 eV, which in close agreement with the theoretical value as reported with ion induced x-ray satellite measurement experiments. The Kα/Kβ X-ray intensity ratios of Chlorine are also investigated for three compounds of chlorine namely NaCl, NiCl2 and FeCl3. The variation in x-ray spectra peak structure is observed for these compounds.

The focusing properties of two-stage (tandem) ideal parallel plate mirror analyzer (PPA) are investigated both analytically using Mathematica [1] and in simulations using SIMION [2]. Both U and S arrangements [3] for 45 and 30 dgrs tandems are investigated for 1st and 2nd order focusing conditions, energy dispersion, trace width, overall transmission and detection solid angle. The effect of a retardation stage between the two stages to improve overall energy resolution is also included. Optimization conditions for highest energy resolution and transmission are explored. Our results are compared to analytical formulas used in applications of the U arrangement 450 tandem in zero-degree Auger projectile spectroscopy (ZAPS) [4-6]. These results could have bearing on the solid angle correction factor [5, 7] used in the recent investigation of the R = σ(4P)/σ(2P) ratio of cross sections [5], where the yield of the long-lived 1s2s2p 4P measured by ZAPS has to be correctly normalized to the prompt 2P yield. This is a work in progress and results to date are presented. REFERENCES: [1] Wolfram Mathematica 9.0, Wolfram Research Inc. [2] SIMION, Electron-optics simulation software, Scientific Instrument Services, Inc. (SIS) http://simion.com [3] Mikhail Yavor, Optics of Charged Particle Analyzers in Advances in Imaging and Electron Physics, ed. P. Hawkes (Elsevier Inc. Amsterdam 2009) vol. 157, pp. 1-406. [4] T. J. M. Zouros and D. H. Lee 1997, Chapter 13 pp. 426-479, in Accelerator-based atomic physics techniques and applications, Eds. S. Shafroth and J.C. Austin, (AIP Woodbury, NY). [5] D. Strohschein et al 2008, Phys. Rev. A 77 022706. [6] D. H. Lee 1990, Ph. D dissertation Kansas State University, Manhattan, KS [7] S. Doukas et al 2015, Rev. Sci. Instrum. 86 043111

The combination of advanced lasers and heavy ion storage rings provides a novel research platform for atomic physics and nuclear physics of highly charged ions (HCI). Laser cooling of highly charged heavy ion beams could reach a much lower momentum spread and much faster cooling speed as compared to electron-cooling and stochastic-cooling. Laser cooling is also considered as one of the most promising techniques to reach high phase-space densities for relativistic heavy ion beams at storage rings. Meanwhile, laser spectroscopy of HCI has already been demonstrated as a precision spectroscopy tool at many storage rings, especially for hyperfine-splitting measurements of H-like and Li-like Bi at the ESR in Darmstadt, Germany. Based on the success of laser cooling of C3+ at the ESR, and the experience of test laser cooling experiments at the CSRe, an experiment of laser cooling of Li-like O5+ ion beams is currently preparing at the CSRe by using a 220 nm cw laser. These experiments can hopefully be performed at the beginning of next year. Laser cooling and precision laser spectroscopy of HCI and even radioactive ion beams, are also being prepared for the High Intensity Accelerator Facility (HIAF), in China and for FAIR in Germany. We will present the preparation of laser cooling of O5+ at the CSRe, and also present the design of the laser cooling and laser spectroscopy of HCI at HIAF.

Investigation of the g factor is one of the most accurate tools for testing physical theories and for determination of fundamental constants. Considerable progress was made recently with experiments with light ions. Moving to the high-Z sector potentially gives new opportunities for precision investigations of the atomic g factor. Further research in this field requires rigorous theoretical consideration of nuclear effects. We present the relativistic calculation of the nuclear recoil correction to the g factor of B-like ions, as an extension of our previous non-relativistic work [1]. The inter-electronic interaction is taken into account to the first order in 1/Z and higher orders are accounted for with screening potential. The low-order relativistic approximation is derived from the QED theory of the nuclear recoil effect [2]. [1] A. A. Shchepetnov et al., J. Phys. Conf. Ser. 583, 012001 (2015) [2] V. M. Shabaev, Phys. Rev. A 64, 052104 (2001)

The combined field of heavy ion and strong laser pulse can be used to produce the electron-positron pairs from the vacuum. This process gives an opportunity for testing QED effects in non-perturbative regime. For experimental investigation of such effects one can use the relativistic ion beam with a strong laser source. The large Lorentz factor leads to to the enhancement of laser power and frequency in the rest frame of the ion and increases the pair-production probability. In order to study the non-perturbative QED effects one needs the proper theoretical methods for description of processes in strong fields. A method for calculation of electron-positron pair production in the combined field of heavy nucleus and laser pulse is presented. The approach is based on numerical solving of the time-dependent Dirac equation in a finite basis set. Using the developed approach the preliminary results for pair-production probabilities are obtained.

The PEGASUS project at GSI aims at providing an intense and portable spin-polarized electron beam for experiments in crossed- and merged-beams arrangements at various ion-beam facilities. Electron energies will range from 1 to 10 keV at electron currents up to 100 μA. Laser induced electron emission from GaAs photocathodes with a state of negative electron affinity will be utilized for beam generation. With a set of electrostatic lenses and benders, the electrons will be transported to the interaction zone. Wien-filters will be used for controlling the spin orientation. The experiment has been designed to be transportable such that it can be used in different places for different experiments, for example as a user experiment at storage rings or as a stand-alone installation coupled with diagnostic elements. Currently planned first experiments comprise the investigation of asymmetries in nonradiative electron capture to continuum at CRYRING at GSI and the measurement of the circular dichroism in collisions of spin polarized electrons with chiral molecules using an ESA22 electron spectrometer.

We investigate the polarization entanglement of two photons emitted in the atomic processes with few-electron ions. All results have been obtained within the framework of the density matrix approach and relativistic quantum theory. We consider two different schemes. In the first one the initial state is the state with well-defined angular momentum and its projection onto the quantization axis. In the second scheme the initial state is the superposition of the states with well-defined angular momenta. Detailed calculations have been performed for radiative recombination, dielectronic recombination and sequential decay.

High-precision measurements of the isotope shifts in heavy ions, that are anticipated at the FAIR facilities, will give a unique possibility for tests of QED in a new region: strong-coupling regime beyond the Furry picture. In addition, these studies will allow determination of the nuclear charge radius differences for radioactive isotopes with a lifetime longer than about 1 min. These investigations require high-precision calculations of the isotope shifts, including the relativistic and QED effects. Such calculations were performed for Li-like ions in Ref. [1] and for B-like ions in Ref. [2]. [1] N. A. Zubova et al., Phys. Rev. A 90, 062512 (2014). [2] N. A. Zubova et al., Phys. Rev. A 93, 052502 (2016).

The purpose of the present work is to obtain a simple expression for estimation of the probability of K-shell ionization in heavy ion collisions. The transition amplitudes was calculated numerically and approximated by a simple analytical expression. It allows obtaining the process probability in a closed analytic form as well. In the present work we focus on the case of asymmetric collisions, when the charges of colliding nuclei noticeably differ. In this case the commonly used monopole approximation is not sufficient, since it is known to be consistent with accurate calculations for small internuclear distances and symmetrical collisions. The nonperturbative wave functions are constructed from monopole states, which are calculated using the dual kinetically balanced B-spline basis set method. The process probability is found to decrease by ~30% for large values of the ratio of nuclei charges.

The Frankfurt Low Energy Storage Ring (FLSR)[1] is an electrostatic storage ring at Institut für Kernphysik, Goethe Universität, Frankfurt am Main, Germany. It has been installed as a novel tool for experiments of the reaction dynamics of vibrational cool molecular ions. First beam was stored in 2013. Since then a number of ions/molecules has been stored. First experiments on dissociative recombination of vibrational cold HeH have been carried out after installation of an electron gun at one of the four interaction points (IP) of the ring (points of enhanced ion density). A large, position sensitive MCP detector has been installed at the 180° port of the ring to detect neutral fragments. In order to determine the kinetic energy loss from reactions of molecules with residual gas ions, this set up has recently been extended by a spectrometer for recoil ions from the residual gas as a first stage of an upgrade to a full reaction microscope, which is planned in the next future. In this contribution results from the experiments above will be presented and design considerations will be discussed. [1] K.E. Stiebing, V. Alexandrov, R. Dörner, S. Enz, T. Kruppi, A. Schempp, H. Schmidt Böcking, M. Völp, P. Ziel, M. Dworak, W. Dilfer; Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment; 614(1):10-16, 2010

To cool ion beams in the heavy ion storage ring CRYRING and thus achieve a low momentum spread, CRYRING features an electron cooler, where the ion beam is superimposed with a monoenergetic electron beam. In order to calculate the velocity of the electrons and therefore of the cooled ion beam, it is mandatory to continously monitor the cooler voltage with a high-precision divider. For that purpose a high-precision voltage divider for voltages up to 35 kV is currently being constructed in Münster, which will be similar to the ultrahigh-precision voltage dividers in use at the KATRIN experiment. The precision of the divider will be in the low ppm range and will, if other sources of systematic uncertainties like e.g. space charge effects are under control, allow for measurement uncertainties in the < 10e-5 region. This project is supported by BMBF under contract number 05P15PMFAA. D. Winzen thanks HGS-HIRe for FAIR for funding his scholarship.

In the present work critical distances for homonuclear quasi-molecules are calculated for a range of point-like and extended nuclei with 85 < Z < 100. High-precision relativistic calculations of the ground-state energy of molecular ions with charges Z = 1, 2, 10, 20, 30, 40, 50, 60, 70, 80, 90, 92, 100 at ``chemical distances''R = 2/Z (in a.u.) were executed. To solve the two-centered Dirac equation the Dirac-Fock-Sturm method, based on the Dirac-Sturm orbitals application for constructing Dirac wave functions is used. According to this method wave functions represent a set of Dirac-Sturm basic functions, which are central-field 4-component Dirac bispinors centred at the ions. The radial parts of these orbitals are obtained by solving numerically the finite-difference radial one-center Dirac and Dirac-Sturm equations.

The study of heavy-ion systems at the GSI Helmholtz-center for Heavy-Ion Research in Darmstadt has proven to provide a deep insight into atomic structures and interactions processes in the presence of extreme field-strengths [1]. The FAIR project which is currently being built at the site of the GSI and especially its High-Energy Storage Ring (HESR) give raise to new opportunities for heavy-ion experiments with the full range of charge-states and energies reaching up to the GeV/u regime [2]. The planning of future heavy-ion-atom collision experiments at relativistic energies at the HESR’s internal gas-target may profit from the availability of a fast calculator for the emission characteristics of the occurring interactions. In particular, those processes are of great importance, which give rise to the emission of high energy photons and electrons that may contribute to the background of a broad range of planned experiments. As a starting point for such a universal calculator, we recently begun to assemble results of theoretic physics concerning relativistic heavy-ion-atom interactions [3-5] into a set of tools that was used to create a database: Precise results on Radiative Electron Recombination, Bremsstrahlung and Binary Encounter processes in a vast parameter range can be found within seconds using the resulting database. The results were used in first simulations on possible day-zero-experiments at the HESR. References [1] T Stöhlker, Y A Litvinov et al., Physica Scripta 2013 (T156) [2] T Stöhlker, Y A Litvinov et al., Hyperfine Interact 227 (2014) [3] A Surzhykov, S Fritsche et al., Phys. Rev. A 65 (2003) [4] V A Yerokhin and A Surzhykov, Phys. Rev. A 82 (2010) [5] F Salvat, A Jablonski and C J Powell, Comput. Phys. Commun. 165 (2005)

Highly charged heavy ions provide a unique possibility to test atomic structure calculations. We would like to study effects of electron-electron correlations in Be-like krypton via a laser spectroscopy measurement of the fine-structure transition from the metastable 3P0 state. For this purpose the ions are stored at β=0.69 in the Experimental Storage Ring (ESR) where the transition to the 3P1 state is excited by an anticollinear laser beam, followed by the almost immediate decay to the ground state by emission of λ=17 nm XUV photons. To collect the forward emitted photons the Institut für Kernphysik in Münster developed a system for in-vacuum detection of XUV photons in the wavelength range from <10 nm up to about 250 nm. Therefore a cathode plate with a slit for the ions is moved into the beam. XUV photons hitting the plate produce mostly low energetic secondary electrons. These electrons are guided electromagnetically onto an in-vacuum MCP detector. In a test beam time at the ESR with 12C3+, the 2s1/2 --> 2p1/2 transition at λ0≈155 nm was investigated using the XUV detection system. First results and conclusions with regard to the upcoming experiment will be presented. This work is supported by BMBF under contract number 05P12PMFAE.

As a result of cooperative theoretical and experimental research of the g-factor of light highly charged ions, the best up-to-date determination of the electron mass was provided [1]. It's expected that independent determination of the fine structure constant will be the result of the corresponding investigations of heavy hydrogen-like and boron-like ions [2,3]. The ARTEMIS experiment is an important contribution towards this goal and it's being carried out presently in GSI [4]. Apart from the g-factor, the non-linear contributions to the Zeeman splitting in boron-like ions are important. Also hyperfine-structure effects should be taken into account for ions with nonzero nuclear spin. Corresponding investigations were performed for 1s_1/2 and 2s_1/2 states [5,6,7]. We present theoretical study of the quadratic Zeeman effect and the hyperfine-interaction correction to the linear Zeeman effect for the 2p_1/2 state including the QED correction. [1] S. Sturm et al., Nature 506, 467 (2014). [2] V. M. Shabaev et al., Phys. Rev. Lett. 96, 253002 (2006). [3] A. V. Volotka and G. Plunien, Phys. Rev. Lett. 113, 023002 (2014). [4] D. von Lindenfels et al., Phys. Rev. A 87, 023412 (2013). [5] D. L. Moskovkin et al., Phys. Rev. A 73, 052506 (2006). [6] D. L. Moskovkin et al., Phys. Rev. A 77, 063421 (2008). [7] V. A. Yerokhin et al., Phys. Rev. A 85, 022512 (2012).

The Technical Design Reports: SPARC@HERS:Instrumentation approved by the Expert Committee Experiments (ECE) on 22 Jan 2016 establishes a large group of Institutes, including National Institute for Laser, Plasma and Radiation Physics (INFLPR), distributed over the subjects Laser Spectroscopy, Intense Laser/Ion Interaction and Laser Cooling. More than 70 researchers, including the INFLPR researchers are listed as participants for these subjects. The development of new lasers with novel sources like soft-X-ray lasers or high average power XUV-lasers require specific technical design for the coupling module to the storage ring and for the corresponding differential pumping stages (including the turbo pumps). In collaboration between the Institute of Applied Physics (FSU & HI Jena) and the INFLPR, existing data in conjunction with new experimental tools will be used to establish technical issues and requirements and workout the design of an appropriate optical experiment coupling the new XUV source and the storage ring. As a next step we will carry out the commissioning of the experimental setup configuration which will be the XUV-storage ring coupling unit. Preliminary technical specifications and requirements of an appropriate solution for coupling of lasers to the UHV storage ring will be presented here. Beside the main contribution to the design work, further works are needed in support of the experiment proposed by SPARC. A summary of theoretical and experimental works performed at INFLPR in support of SPARC@FAIR will also be presented.

The talk will report on the latest achievements in high repetition rate table-top XUV sources. These devices, based on high harmonic generation of femtosecond fiber lasers, now deliver up to 1 mW (~1E14 photons/s) and 26.6eV. The concept for an XUV source and beam delivery to be first used for Photoionization experiments at CRYRING will be presented. This instrument will be portable and can, in prinicle, be coupled to most of the storage rings and ion traps of the future FAIR facility. It will enable seminal studies an highly-charged ions including pump-probe experiments on Femtosecond time scales.

The presentation starts with the basic principle of the Cryogenic Current Comparator (CCC) as a high-sensitive, non-destructive monitoring tool for charged beams with nA-intensities. It will be shown that superconducting is essential to get the outstanding performance, and the main superconducting parts like the toroidal pick-up coil, the shielding, the DC-matching-transformer, the Superconducting Quantum Interference Device (SQUID) and also the flux-concentrator and flux-compensator will be illustrated. The second part of the presentation shows the progress in the development of the next CCD generation with eXtended Dimensions (CCC-XD) for larger beamline diameters planned for the new FAIR accelerator facility at GSI. The new, specially designed nanocrystalline flux concentrator enables low-noise operation and a high system bandwidth of up to 200 kHz. The niobium shielding is extended in its geometric dimensions and will effectively suppress (< -200 dB) disturbing magnetic fields of the beamline environment. A completely new SQUID sensor with Josephson junctions with sub-µm dimensions offers the lowest possible noise-limited current resolution in combination with a good suppression of external disturbances. Complete with a new cryostat the CCC-XD will be ready for testing in the CRYRING at GSI in spring 2017.

The relativistic wave function of a twisted electron which accounts for the field of a bare ion in all orders is constructed. This wave function is utilized for the description of the radiative recombination of a twisted electron with a heavy ion. Two types of ionic targets are considered, namely the infinitely extended one and the target with a finite spatial distribution. For the infinite target we compare our results with the ones obtained previously in the framework of the first Born approximation. Additionally, the case when the twisted electron is a superposition is studied.

Knowledge of fundamental electronic mechanisms at play in Fast Ion – Slow Ion Collisions (FISIC) can provide a real breakthrough in the understanding of energy transfer in various plasmas such as inertial confinement fusion plasmas, stellar/interstellar plasmas and also in material damages. Indeed, when a few MeV/u ions collide with a few keV/u ions, a hitherto unexplored collision regime is reached: a regime where the ion energy transfer is at its maximum. There, all the primary electronic processes, like electron capture, loss and excitation, reach their optimum leading, for instance, to possible interference effects. Measurements and reliable theoretical predictions are completely lacking in this intermediate collision regime corresponding therefore to a real “terra incognita” for atomic physics. Crossing two multicharged ion beams, under well controlled conditions, has always been a very challenging task, whatever the domain of physics under consideration. The forthcoming availability of MeV energy, intense and stable ion beams of high optical quality at French and German Large Scale Facilities (GANIL/SPIRAL2 and FAIR/CRYRING) opens new opportunities towards the intermediate collision regime. With the FISIC project, we propose an experimental crossed-beam arrangement with an ultimate control of experimental conditions to measure absolute electronic cross sections. The goal is to span from a pure three-body problem (collision between a bare ion and a hydrogenic target) to a collision system between dressed partners (study of the effect of a controlled number of additional electrons). For the realization of such a challenging experimental project, a lot of technical barriers have to be overcome, among them, the control and detection of the slow ion charge states, the detection of high energy ions, the overlap between the two ion beams, the design of the collider, the vacuum conditions, the stripping issue of intense ion beams delivered by the SPIRAL2 accelerator,… A status report on the progress of the FISIC program will be presented at the conference.

In the present work we report on the results of the X-ray spectroscopy experiments performed at EBIS-A facility in Kielce [1]. These experiments concern the studies of the X-ray emission from highly charged ions extracted from the EBIT, in this case ~3 keV×q Xeq+ ions (q=26-40), interacting with metallic Be foil. In such process the so-called „hollow atoms” are created [2-3]. The X-ray emitted in deexcitation of hollow atoms carry information on the structure of such exotic objects as excited highly charged ions. Another type of experiments performed at the EBIS facility is the study of atomic processes taking place in the EBIT plasma, in particular, the electron impact ionization/excitation, radiative/nonradiative deexcitation and radiative recombination processes. In both experiments the X-rays were measured with semiconductor drift detector (SDD) having 129 eV energy resolution at Mn Kα line. The X-ray spectra obtained were interpreted assuming electric dipole selection rules and available calculations of X-ray energies in highly charged Xe ions [4]. This allowed to understand the studied processes qualitatively, however, more detailed atomic structure MCDF calculations are needed to fully describe the observed X-ray spectra. References [1] D. Banaś et al. J. Instrum. 5, C09005 (2010) [2] H. Winter, F. Aumayr, J. Phys. B 58, 1 (1999) [3] J-P. Briand Phys. Rev. Lett. 65, 2 (1990) [4] B. Rudek et al. Nature Photonics 6 (2012)