5th Slow Extraction Workshop at MedAustron in Wiener Neustadt

MedAustron is a synchrotron based particle therapy facility located in Wiener Neustadt, Austria.

It comprises of 4 irradiation rooms, 3 of which are dedicated to medical treatment using protons (62.4 and 252.7 MeV) and carbon ions (120 and 402.8 MeV/u) delivered via 3 fixed beam lines (2 horizontal and 1 vertical) and 1 Gantry (protons only). It is the only facility world-wide that uses a rotator system combined with the Gantry.

The fourth irradiation room is dedicated purely to research, with the delivery of carbon, helium ion beams and protons up to 800 MeV.

Since the completion of the building construction in 2012, the planned commissioning with carbon ions was finalized in 2023 and MedAustron is now operating at its full functionality. The facility is constantly striving to enhance treatment performance and expand the range of indications, which includes improvements to slow extraction mechanisms. Since the first patient treatment in December 2016, more than 2,000 patients have been treated at MedAustron.

The presentation will include an overview of the facility and an introduction to the ongoing projects for performance improvement including potential topics for collaboration.

CNAO is one of the four centres in Europe, and six worldwide, offering treatments of tumours with both protons and carbon ions. By the end of 2023 more than 4800 patients were treated at CNAO.
The CNAO synchrotron provides carbon ion beams with energies up to 400 MeV/u and protons up to 227 MeV in 3 treatment rooms and one experimental room open also to external users. The beam distribution in all the lines is based on active scanning and the maximum field size is 200 mm x 200 mm. Experiments at CNAO can benefit of the presence of an equipped biological laboratory.
The major upgrades ongoing of the facility are:
1) An additional ion source was installed and commissioning shall start soon. The new source will produce additional ions species and the first species for which an authorization was asked are He, Li, O and Fe.
2) A Single Room Facility for protons with a gantry will be installed in a new building next to the present one
3) An accelerator based BNCT Facility will also be installed
4) The research area will be expanded as well as the biology labs and rooms for small animals experiments will be made accessible
A carbon ion gantry will be a fundamental improvement of the facility and for that reason gantry design activities are ongoing in the framework of the HITRIplus and EuroSIG international collaborations.

Heidelberg ion beam therapy centre (HIT) was the first dedicated ion beam therapy facility in Europe.
Since 2009 more than 8000 patients have been treated with carbon ions, protons and, more recently, also with helium ions.

Several compact application facilities have been designed and developed for space science study and cancer therapy by IMP (Institute of Modern Physics, Chinese Academy of Sciences) based on technical developments and plentiful experiences from HIRFL-CSR and HIAF. For the complicated space environment simulation and related science research, the SESRI (Space Environment Simulation and Research Infrastructure) and PREF (Proton Radiation Effects Facility) are constructed to ensure the safe operation of spacecraft and the health of astronauts in the space environment. In addition, the second generation of cancer therapy facility is also designed and optimized. A strict design, fabrication and installation process has been built to guarantee stable and reliable operation for the developed facilities.

The Next Ion Medical Machine Study (NIMMS) is an international collaboration initiative, established in 2018 and based at CERN, with the goal of developing new technologies for the future generation of accelerators for cancer therapy with ions. It has four work packages: superconducting magnets, gantries, compact synchrotrons and high-frequency linacs.
This contribution focuses on medical synchrotron developments and potential facility implementation.

Heavy-ion single event effect (SEE) test facilities are critical in the development of microelectronic components that will be exposed to the ionizing particles present in the hostile environment of space. CHARM High-energy Ions for Micro Electronics Reliability Assurance (CHIMERA) and HEARTS have developed a high-energy ion beam capable of scanning a wide range of Linear Energy Transfer (LET) at low intensities to study ionization effects on space-bound technology using CERN's Proton Synchrotron (PS). This contribution describes the extraction and transport of low-intensity lead ions at multiple energies to the CHARM facility at the East Area of CERN. Furthermore, it discusses the implementation of a Radio Frequency Knockout (RFKO) technique that streamlines beam extraction and enhances particle flux control and reproducibility across different energies, thereby improving performance and reliability in SEE testing.

In the framework of the Physics Beyond Colliders Study Group, recent efforts have demonstrated the feasibility of increasing, by over an order of magnitude, the intensity of the 400 GeV proton beam delivered to the underground Experimental Cavern North 3 (ECN3) of CERN’s North Area. At the June 2023 CERN Council, an ambitious study project was approved to deliver a Technical Design Report detailing a coherent upgrade plan for a new High Intensity ECN3 (HI-ECN3) fixed target facility, to start operation after Long Shutdown 3 (LS3) and to spearhead the search for the existence of physics Beyond the Standard Model at CERN, which has evaded direct discovery in high energy colliders. In this contribution, the latest status of the project is presented along with the timeline for the new, or upgraded, fixed target experimental programme at CERN.

The GSI facility for research with heavy ions provides experiments with slow
extracted beams from the synchrotron SIS18 since the early 1990s. Presently, the
new FAIR facility is under construction next to the GSI site. FAIR will allow
experiments to continue and extend their heavy ion research programs by
providing beams of higher energies and higher intensities with slow extraction
from the new synchrotron SIS100. In this contribution, we give an overview of
the experiments utilizing slow extraction at GSI and FAIR and their requirements
on beam parameters and quality. Also, we introduce the synchrotrons SIS18 and
SIS100 with respect to their capabilities for slow extraction.

The Slow Extraction Survey was conducted in 2021 as part of the iFAST-REX collaboration and extended to a broader audience at the Slow Extraction Workshop in 2022. Eleven facilities from around the world participated in the parameter collection. The survey aimed to establish the current state of slow extraction in all facilities and use this as a baseline for future collaborations and developments.
This presentation summarizes the results of the parameter collection and provides an update on the recent developments of the participating facilities since 2022. The focus will be on the extraction parameter as well as the intensity ripples in the extracted beam and corresponding mitigation measures.

There are 7 carbon synchrotron and 12 proton synchrotron in operation for particle therapy in Japan. Advanced slow extraction technique has been developed for raster scanning irradiation for carbon ion therapy in HIMAC and other facilities such as double RF knock-out method for ripple reduction and multiple-energy operation using extended flattop. This technique have enabled the scanning irradiation for respiratory moving organ such as Lung, Liver, and Pancreas, and the treatment for large radioresistant tumor such as bone and soft tissue cancer within a reasonable irradiation time. The newest carbon ion therapy facility, East Japan Heavy Ion Center, Faculty of Medicine, Yamagata University, has 600 available beam energies to control the beam range by 0.5 mm step. Beam extraction parameters are tuned by many energies with use of interpolation to reduce ripples and spike in the extracted spill. This facility also have a superconducting rotating gantry, 15-degree step operation for 600 energies are successfully commissioned by March 2023. Stable extraction control is also utilized for physical experiment which needs extremely low intensity of ~100 particles per second.

Single Event Effects (SEE) testing is a critical part of developing technologies for the interplanetary space environment. The proposed BNL High Energy Effects Test (HEET) facility that we would build off the AGS, is being designed for the needs of the SEE testing community. This short report will discuss the proposed design, from the slow extraction to a new beamline, and the capabilities of this new facility.

Mu2e experiment, searching for a super rare mode of the CLFV decay of muon into an electron is in preparation for data taking at Fermilab’s Muon Campus facility. The experiment requires the 8 GeV proton beam continuous delivery aided by the Slow Extraction (SX) from the Delivery Ring. The first beam commissioning of the SX has been scheduled for FY2024. However, there was a possibility to start commissioning earlier, in FY2023. Here we will discuss our first experience and challenges with running SX in the Delivery Ring.

J-PARC Main Ring(MR) accelerates the proton beam from 3 GeV to 30 GeV and delivers the beam to the Hadron Experimental Facility(HEF) through slow extraction using third-order resonance. At the HEF various particle and nuclear physics experiments are conducted mainly using kaon beams generated on secondary particle production targets and also primary proton beams. From 2021 to 2023, the J-PARC MR upgraded its components such as main magnet power supplies and RF cavities intending to shorten the acceleration time and the repetition time. Although there were various troubles in and after the MR upgrade, we performed the first 30 GeV slow extraction operation after the upgrade in June 2023. We successfully reproduced the high extraction efficiency of 99.5% with the same 5.2s repetition cycle as before the upgrade. Currently, preparations are underway for a beam tuning operation with a shortened repetition time of 4.24 s. In this talk, we will explain the current status and plan of the slow extraction system of the J-PARC MR.

High Intensity Heavy-ion Accelerator Facility (HIAF) is a giant accelerator facility aiming at high intensity primary and secondary beam preparation which is under construction in China. To achieve the challenging intensity goal, high intensity beam preparation remains a top priority of dynamics research. The first issue is how to accumulate in BRing with High injection gain(>56) and low beam loss(<5%). The second one is serious beam loss in early acceleration, when space charge effect, dynamic vacuum effect, collective instability dominate the intensity limitation. We developed a dedicated simulation platform CISP-GPU for coupling high intensity dynamics research. A series of stabilization efforts are performed to achieve the intensity goal, which needs higher performance for power supply, RF system and vacuum chamber. We have made breakthrough in this key components. Now more than 50% of the hardware series fabrication are completed. The series installation and joint commissioning will start in Feb. of this year. The civil construction and supporting facilities are in the closeout phase. They will accomplish in Apr. of this year. We will conduct installation and commission simultaneously in the coming years.

Xsuite is a modular simulation package bringing to a single flexible and modern framework capabilities of different tools developed at CERN in the past decades, notably MAD-X, Sixtrack, Sixtracklib, COMBI and PyHEADTAIL. The suite consists of a set of Python modules (Xobjects, Xpart, Xtrack, Xcoll, Xfields, Xdeps) that can be flexibly combined together and with other accelerator- specific and general-purpose python tools to study complex simulation scenarios. Different computing platforms are supported, including conventional CPUs, as well as GPUs from different vendors. The code allows for symplectic modeling of the particle dynamics, combined with the effect of synchrotron radiation, impedances, feedbacks, space charge, electron cloud, beam-beam, beamstrahlung, and electron lenses. For collimation studies, beam-matter interaction is simulated using the K2 scattering model or interfacing Xsuite with the BDSIM/Geant4 library. Methods are made available to compute and optimize the accelerator lattice functions, chromatic properties, equilibrium beam sizes. By now the tool has reached a mature stage of development and is used for simulations studies by a large and diverse user community.

The intensity ripples in the extracted beam are a crucial topic for clinical treatment, as a constant particle flux is required for optimal operation of the accelerator within safety regulations. Therefore, ripple mitigation techniques are widely used in facilities worldwide.
This talk discusses the intensity ripples at MedAustron by analysing the ripple frequency spectrum and the impact of the ripples on the quality of the beam. Empty Bucket Channeling (EBC) is a common method for mitigating ripples, and its effect on beam quality can be quantified by high-bandwidth intensity measurements. Various extraction techniques such as RF Knockout, Constant Optics Slow Extraction (COSE) and Phase Displacement Extraction (PDE) are compared based on their capability of ripple suppression.
Measurements of the ripple transfer function for different ripple frequencies and amplitudes can be used to identify the components that are most sensitive to ripple transmission, which correlates to the relevance for ripple suppression for these components.

Results of two topics are presented in this contribution.
The first one is the influence of some quantities on the spill quality of the KO extraction from the future GSI heavy ion synchrotron SIS100 studied with particle tracking simulations. This technique is still foreseen as standard slow extraction technique in SIS100. The results suggest that for such conditions the presently applied KO signal is a major source of spill micro structures. One peciularity of the KO extraction from this synchrotron arises from its circumference of about 1 km and a spill recording with high sampling rates up to 100 kHz such that the revolution time is not necessarily much shorter than the time intervals of the spill measurement.
The second topic is related to transit times during tune sweep slow extraction from the present GSI heavy ion synchrotron SIS18. The width of their distribution supports the mitigation of spill micro structures. Hence, a transit time determination is desirable. A first attempt of that is presented.

In this contribution, we will discuss the beam dynamics relevant for the KO extracted spill feedback loop by means of Xsuite simulations and measurements at GSI SIS-18. The fundamental limitations of this feedback scheme under typical machine settings and excitation waveforms will be highlighted.
This project has received funding from the European Union’s Horizon 2020 Research and Innovation programme under GA No 101004730.

The beam response to an external periodic excitation delivers relevant information about the ion-beam optics, tune distribution and stability of a circulating beam in a storage ring. In this contribution the horizontal beam response under conditions typical for slow extraction is presented for a coasting beam. The resulting spectrum exhibits a splitting behaviour. The single particle dynamics is discussed and an interpretation based on simulation results is presented.

The Heidelberg Ion-Beam Therapy Centre HIT uses the RF-KO slow extraction method to extract the particles from the synchrotron. To improve the spill quality of the extracted beam a new RF-signal was investigated which increases the R-value from 92.5% to 97.5%. The signal is a multiband RF signal broadened with a random BPSK at 3 frequency bands. The new KO-DDS which generates the signal is in medical use since October 2023 and the first experience are presented in this talk.

In this talk, we investigate the transit time of particles in a third-integer resonant extraction process. Transit time is defined as the number of turns a particle takes to get extracted once it is in the unstable region, i.e., outside the triangular separatrix. The study of transit time is important because transit time determines the beam response time during resonant extraction and thus knowing it aprori could be practically useful in designing a resonant extraction system. We shall review and borrow a few important results from the first-order Kobayashi Hamiltonian formalism that would aid us in the transit time studies of particles during the extraction process. Here we investigate the transit time of particles in different parts of the phase space distribution and compare against the analytical results. We also compare the simulation result of the transit time of particles (with higher statistics) for the static as well as dynamic extraction conditions cases, particularly in the context of resonant extraction parameters for Mu2e experiment at Fermilab.

The main magnet power supplies for the J-PARC Main Ring were upgraded from 2021 to 2023. In addition to increasing the maximum voltage output to shorten the acceleration time from 3GeV to 30GeV, reducing the current ripples for improving the beam spill structure was also one of the major objectives of the power supply upgrade. Although good results were obtained in current ripple measurements during the power supply development stage, the expected reduction in the current ripple has not yet been achieved, and new problems have also come to light from the beam operation after the upgrade. In this talk, we will explain the current status of the spill structure in the slow extraction beam operation after upgrading the main electromagnet power supplies and plans.

Inevitably, to evaluate the quality of the slow extracted beams delivered to experiments, we need to understand how different frequency components develop. How we evaluate this is to look at the beam spills in a beamline. However, while those are the end result and what the experiments see, they don’t directly represent how the different frequencies get imprinted into the spill. This is what transit time analysis tells us. To evaluate the ripple components more realistically, we plan to use direct field ripple measurements in a reference magnet that includes the vacuum chamber. This talk will present the idea and the status of the project.

Spill uniformity is a key performance metric for the experimental users in the CERN North Area, who receive slow-extracted protons from the Super Proton Synchrotron. In this contribution, RF empty-bucket techniques are studied to suppress the low-frequency variations in the spill caused by power-converter ripple. The study includes simulation, measurement and the long-term experience after making the solution operational in mid-2023.

Multiple energy extraction can deliver multiple energy flattops per accelerator cycle, improving treatment efficiency. In this process, the extraction efficiency of each flattop and the beam loss during non-extraction times are the key parameters. Such beam loss is mainly composed of the spill intensity overshoot, which reduces the number of particles available for treatment and thereby lowers treatment efficiency. So, two new schemes for multiple energy extraction are proposed which can reduce the overshoot while maintain high extraction efficiency. To compare different schemes, a beam loss index is defined and a simple evaluation model established. The model relates such beam loss and the extraction efficiency to the number of tumor layers irradiated per accelerator cycle, allowing for a more intuitive analysis of how beam loss influences treatment efficiency. Then, a comparison experiment between these two schemes and other two schemes is conducted at the Xi’an 200 MeV Proton Application Facility (XiPAF). Results show that the new schemes can indeed reduce the beam loss as expected. However, the beam loss can’t be eliminated completely, and the differences among the four schemes are relatively small. Analysis with the established model reveals that the differences among the 4 schemes may have limited influence on the treatment efficiency. Furthermore, through discussion, it is found that the implementation costs vary significantly among different schemes. Therefore, in situations where such beam loss is acceptable, the scheme with the lowest cost may be a better choice actually.

The temporary quality of the slowly extracted beams from a synchrotron on the 100 microseconds time scale is crucial for fixed-target experiments and hadron therapy. The spill micro structure is caused by power supply ripples that act on the ring quadrupoles. To reveal the beam dynamics of the slowly extracted beams, the transit time is investigated theoretically and experimentally. It is a crucial physics quantity which relates the beam dynamics inside the synchrotron with the temporal structure of the extracted beam. The investigation was performed at SIS18 at GSI, where tune scan slow extraction is routinely performed. In simulation, different approaches for the transit time determination were proposed and executed with particle tracking tools Xsuite. Experimentally, spills with sinusoidal tune excitations were evaluated, and the results show that the variation of transit time and spread during extraction is related to emittance reduction during the extraction process. Spill quality improvements described by the duty factor increases for smaller emittances had been shown in previous papers and will shortly be repeated here. To achieve a better insight into the beam dynamics an experimental test of quasi-step-type excitations of a fast quadrupole field was performed experimentally. The results and conclusions will be presented.

Experiments and simulations regarding the micro spill structure of slowly extracted bunched beams have been performed at GSI for years. In SIS18 the bunch spacing was limited to a minimum of 185 us due to the operating frequency range of the installed cavities and LLRF. To overcome this limit, which is not suitable for many detectors, a new cavity system was developed.
The cavity was installed in SIS18 in July 2023 and commissioned with beam in November 2023.
Challenges in the development and selected measurements with and without beam are presented.

The Mechanical and Materials Engineering group of the Engineering Department at CERN has gained in the last decade important experience in the comprehensive characterization of low Z materials, offering valuable insights into their properties and field of application. We focus on elucidating the unique challenges associated with low Z materials, encompassing their processing, welding techniques, and fabrication methods. Our expertise covers advanced non-destructive testing (NDT) methods as part of quality control to ensure the integrity of the materials, such as Computed Tomography (CT), High-Resolution X-Ray Diffraction (HR-XRD) or specially adapted Scanning Electron Microscopy (SEM) techniques for the investigation of light materials. We are also equipped with Focused Ion Beam (FIB)-SEM and instrumented nanoindentation as destructive techniques used during the post-mortem evaluations of for example HiRadMat specimens, fixed targets or beam instrumentation devices. By leveraging our state-of-the-art facilities, we provide essential support for an advanced understanding and application of low Z materials in a wide variety of projects at CERN.

The CERN Super Proton Synchrotron (SPS) plays a crucial role in the CERN Fixed Target (FT) physics program by extracting proton beams towards the North Area (NA) targets. In order to gradually deliver the proton beams to the three primary NA targets, slow extraction is performed by approaching the third order resonance in the SPS, and the spill is eventually split on two vertical splitters upstream of the targets. To enhance the efficiency of the extraction and maximize the duty factor, a set of algorithms has been developed and integrated into the SPS operation controls system. These algorithms automatically regulate the target symmetry, intensity, and flatten the spill structure in real-time. This presentation outlines the functionalities of these tools and highlights their operational benefits for the FT physics. Finally, an outlook on the future evolution of these algorithms and their potential integration into an operational framework is given.

A poster describing the limitations of extraction from a compact scaling fixed field accelerator. The LhARA Stage 2 FFA is used as the optics baseline, based on the RACCAM study. RF-KO is applied as the main extraction method.
Poster first presented at IPAC 2023 by A. Steinberg, with results published in IOP conference proceedings.

Mitigating the micro-structure of the spill can be achieved by adjusting the machine settings or manipulating the beam properties. At SIS18, spill smoothing was commissioned by changing the longitudinal distribution of the circulating beam with RF cavities. Tune scan slow extraction was performed using two different frequencies for the RF cavities: bunching was performed at roughly 4.85 MHz (4 circulating bunches) or roughly 81.44 MHz (with 90 circulating bunches). The arrival times of particles were measured using a plastic scintillator (BC400). The analogue signal from the photomultiplier was converted to a logic signal by a 300 MHz discriminator and then characterized by the Time-Digital-Converter (TDC, CAEN V1290N), which recorded the timestamps of each individual particle with a time resolution of about 50 ps for the TDC only. The time structure of the particle arrival times with respect to the RF cavity and particle intervals with respect to each other were analyzed. For the 4.85 MHz low RF frequency, the standard deviation σ of the distribution of particle arrival times with respect to the RF cavity is about 6 ns, which is significantly shorter than for circulating bunches. In addition, a variation of σ and a drift of the centre of approximately 5 ns were observed along the extraction. These are typical values also observed previously. For the extraction with a higher frequency RF of 81.44 MHz the corresponding σ is about 2 ns. In addition, the shape of the distribution of particle arrival times changes significantly during the extraction. A possible reason for this change could be the excitation of the synchrotron-betatron resonance.

Within the EU-funded activity IFAST, the task REX (Resonance Extraction Improvement) was launched in 2021 as WP 5.3. The IFAST-REX consortium comprises European hadron synchrotron facilities CERN and GSI, the hadron therapy centres CNAO, HIT, MedAustron, MIT and SEEIIST, as well as the companies Barthel HF-Technik and Bergoz Instrumentation. It deals with the crucial challenge of slow extraction in mitigating the current fluctuation on the time scale of typically 0.01 to 10 ms, primarily caused by magnet power supplier ripples. Higher frequency ripples due to the properties of beam excitation methods are also considered. IFAST-REX is organized into four modules: Two modules execute the realization of a high dynamic range low-frequency current transformer and tailored high power amplifiers for beam excitation. The other two modules focus on developing simulation tools for accurate long-term slow extraction and developing diagnostics related to extracted particle detection and analysis. This contribution summarizes the current status of the consortium efforts by indicating to selected results.

This project has received funding from the European Union’s Horizon 2020 Research and Innovation programme under GA No 101004730.

The poster was presented at IPAC 2023.

The High energy FRagment Separator (HFRS), a new generation in-flight radioactive separator in the intensity Heavy Ion Accelerator Facility (HIAF), is under construction in China. It is characterized by large ion-optical acceptance, high resolution power, high magnetic rigidity, and excellent particle identification. In combination with the HIAF accelerator facility, which will provide high-intensity beams, a wide range of neutron-rich and proton-rich exotic nuclei far from the stability using not only projectile fragmentation but also in-flight fission can be produced and studied. In addition, some experiments which need high beam energy like hypernuclei and Δ-resonances studies in exotic nuclei can be also carried out in the HFRS. In this paper, the development of ion-optical calculation and the high-order correction of aberrations are demonstrated using the detailed measured and simulated magnetic field distribution first. Then, the performance of the separator are studied using fission products and heavy fragmentation products. This work will guide future experimental designs at the HFRS.

The HIAF project is a new international advanced accelerator in China, which needs a new type of high power, high precision, fast-cycling pulse power supplies to provide excitation current for the magnets of its B-Ring system.

Monitoring the extraction of protons from the CERN Super Proton Synchrotron (SPS) ring to the North Area (NA) facility at a high rate is crucial for optimizing the extraction process and ensuring efficient fixed target physics. To achieve this, it is necessary to measure beam current fluctuations across a wide range of frequencies, from a few hundred Hz to several hundred MHz. This optimization is important for the current facility operation, ongoing NA consolidation, and future Physics Beyond Colliders (PBC) projects. PBC may even require measurements in the several GHz range.

This presentation will focus on the current status and future prospects of fast spill monitors that have been developed and tested in recent years. One particular emphasis will be on a monitor that detects beam-induced Optical Transition Radiation (OTR). Additionally, an overview of the status of diamond, secondary electron emission, and Cherenkov light monitors will be provided.

The secondary emission beam monitors of the North Area at CERN (BSIs) form a vital component in the delivery of stable beams to experiments and users. Located in the primary beam lines, these monitors operate by integrating low-energy secondary electrons emitted proportionally to the charged particle flux. In turn, the absolute calibration of these monitors plays a key role in their operation. One possibility is installing an activation foil in the proximity of the detector to be calibrated, exposing it to a substantial fluence, and then measuring by gamma spectrometry the activity of key isotopes generated in those foils. By comparison of those activities with cross-section values from literature, an absolute proton flux through the activation foil can be derived.

In 2022, a first calibration of the BSI monitor at the T10 target station was made using aluminium and copper foils, resulting in an agreement of 99.1+/-1.8% between the fluence integrated by the monitor and the activation foil. The method was further extended to calibrate the monitors of the three target stations located in the TCC2 cavern: T2, T4 and T6. The contribution will focus on the method of calibration of the monitors and on the experience gained, and will present some of the difficulties encountered in the various calibration runs attempted.

The Cryogenic Current Comparator (CCC) is a SQUID based superconducting device for intensity measurement, which has first been proposed as a beam diagnostics in the mid 90s at GSI. In the course of plannings for FAIR the CCC has been revitalized as intensity monitor for exotic/highly charged ions and antiprotons in the storage rings as well as for slow extracted beams in the extraction and experimental lines. Since 2014 systematic investigations have been carried out within a dedicated collaboration, which led to improvements of detector and cryostat, resulting in nA spill measurements with a prototype at GSI and in the following installation of a CCC in CERN Antiproton Decelerator (AD).
The optimization process of the device is ongoing, with respect to varying operating conditions, system robustness, current resolution and last not least system costs. Due to the planned realization steps of the FAIR facility, the application of the CCC for online spill measurement and analysis has moved into the forground now. In the first stage of FAIR, CCCs will be installed at SIS18 extraction and in front of SFRS, one of the two devices is already in operation at GSI and tested in the 2023 run. We will show some results from beam measurements and present an overview of CCC development, focused on the possibilities for online analysis of slow extracted beams.

The J-PARC Hadron beamline is a slow-extraction beamline with three primary beamlines. The A line (30 GeV, 65 kW, spill length of 2 seconds, cycle of 5.2 seconds) serves as a beamline for experiments utilizing secondary particles generated at the T1 target. The B-line (30 GeV, 24 W, spill length of 2 seconds, cycle of 5.2 seconds) branches out part of A-line beam, directly employing protons for experiments. The C-line (8 GeV, 0.33 kW, spill length of 0.5 seconds, cycle of 9.6 seconds) is a beamline of the bunched slow extraction to generate muons for experiments.
While a variety of monitors are prepared for beam diagnostics in these beamlines, this presentation focuses on introducing the main profile monitors, RGIPMs (Residual Gas Ionization Profile Monitor).
The RGIPMs in the primary beam lines has desirable features such as non-destructive measurement, radiation resistance, requring minimal maintenance, and good signal to noise ratio because the RGIPMs collect ionized electrons when the proton beams pass through residual gas of about 1 Pa.
This presentation provides a detailed explanation of the measurement mechanism and introduces the performance of RGIPM, including the stability of short-term and long-term profiles.

J-PARC Main Ring currently delivers 30 GeV, 65 kW (7 × 1013 ppp) slow-extracted proton beams over 2 s to the hadron experimental facility to drive various nuclear and particle physics experiments. A high-intensity beam triggered by risky machine trips could cause serious damage to an electric septum or a production target. The Hadron Hall incident that occurred in 2013 was the most serious in the J-PARC facility. A production gold target in the Hadron Hall was evaporated by an accidental short pulsed SX beam, which was caused by a malfunction of the spill feedback quadrupole (EQ) power supply. In 2021, a vacuum circuit breaker (VCB) malfunction for the quadrupole power supplies in straight sections caused serious damage to the electrostatic septum. We predicted trips of the main bending and defocusing quadrupole power supplies could generate a short-pulse beam to the target. We have analyzed beam behaviors of past incidents and predicted risks and then executed their measures, that are indispensable for a high-intensity SX run.

2020 MedAustron and Instrumentation Technologies started to develop a new RF instrument, capable of handling all RF use-cases in the injector or the synchrotron at MedAustron. This development is now mostly finished and the device is ready for commissioning. The system can be used as digitizer or beam diagnostic device, but it can also generate arbitrary RF signals. Combining RF readout and generation, it can be used to regulate cavity amplitudes and phases, and additionally beam phase and radial position regulation is possible for synchrotron applications. On the beam diagnostic side, online beam energy measurements (using time of flight) and beam position measurements are available. With offline data processing, Schottky measurements and longitudinal phase space reconstructions are possible. The presentation will introduce the instrument and some basic design principles and will show some examples how it can be used or is already used at MedAustron.

This presentation describes some of the beam losses and instabilities observed in the MedAustron synchrotron during operation that could potentially affect the efficiency of RFKO slow extraction. The slow extraction process at MedAustron is driven by a Betatron core for clinical operation, and the RFKO method is being studied experimentally in view of a future machine improvement. This study summarizes the different causes of beam losses observed before and during extraction and the lessons learned for both Betatron and RFKO operations.

The NASA Space Radiation Laboratory (NSRL) uses beams of various ions species slowly extracted from Booster synchrotron at Brookhaven National Laboratory. Experimenters at NSRL require uniformly distributed radiation dose to simulate the space radiation environment. The NSRL facility generates uniform beam distribution of various ion species at the location of the target using a pair of octupole magnets in the beam-transport line. The beamline is designed to be achromatic through the octupoles and to the target. However, the dispersion function depends on the trajectory of the beam as it is transported out of the booster and into the beamline. The dependance on this trajectory has not been previously studied. In this presentation, we describe a new model we have developed to study this effect and show measurements to compare to our simulations.

The SESRI facility, known as the Space Environment Simulation and Research Infrastructure, was successfully completed in Harbin, China, in 2022. It stands as a comprehensive ion species facility exclusively dedicated to space environment simulation and associated scientific research.
During the design and construction phases of SESRI, two major challenges were encountered. To effectively tackle the issues presented by low-energy, large-emittance beams, the facility implemented a series of slow extraction schemes. Among these, the most crucial involved the gradual ramping of sextupole strength and the incorporation of dynamic bumpers. Addressing another challenge related to beam uniformity, extensive discussions were conducted on the correlations between waveforms and particle profiles measured on Multistrip Ionization Chambers (MICs). Subsequently, a feedback system was implemented, resulting in a remarkable improvement in beam uniformities to surpass the 95% mark.

The synchrotron SIS100 has been optimized for operation with the partially
stripped ion U28+, resulting in a number of unique challenges: transverse
emittances are comparatively large; the beam has high damage potential due to
the high dE/dx; the lattice must provide efficient collimation of ions losing
electrons in collisions with residual gas to prevent vacuum instabilities.
Resulting in strong focusing, slow extraction requires correction of the large
horizontal chromaticity to ensure high extraction efficiency while satisfying
the tight geometrical constraints. Amplitude dependent tune-shift by
chromaticity sextupoles then causes a bending of the separatrix which needs to
be compensated by octupoles. Additional higher-order effects arise from field
errors of main dipoles and quadrupoles, which were measured to have unexpectedly
large systematic multipoles, significantly changing the geometry of the
separatrix. We discuss possible ways of mitigating the effect of those
nonlinearities using the available corrector magnets as well as consequences for
the choice of slow extraction scheme and commissioning strategy.

Modern low emittance lattices typically require a reduced cell length and high quadrupole gradients, thereby generating large natural chromaticities. Thanks to the low dispersion requirement the chromaticity correction requires strong sextupoles, which accentuate the role of the non-linear dynamics in the machine. We present the design considerations of a resonant slow extraction based on the radio frequency knock-out (RF-KO) scheme, where the underlying dynamics are not
only governed by the well-known Kobayashi Hamiltonian.

The current beam power for the user operation in J-PARC MR's slow extraction beam is 64 kW. After the beam operation at this beam intensity, the on-contact residual radiation dose rate with a cooling time of 6.5 h exceeded 10 mSv/h around the ESS. To further increase the beam intensity while keeping the maintainability of the devices, further reduction of the beam loss is essential. Thus we are planning to reduce the beam loss using beam diffusers which are placed upstream of ESS. In this talk, we will discuss the configuration of beam diffusers, simulation studies using FLUKA code, the beam test results conducted in 2021, and plans.

Mu2e experiment, searching for a super rare mode of the CLFV decay of muon into an electron is in preparation for data taking at Fermilab’s Muon Campus facility. The experiment requires the 8 GeV proton beam continuous delivery aided by the Slow Extraction (SX) from the Delivery Ring. The first beam commissioning of the SX has been scheduled for FY2024. However, there was a possibility to start commissioning earlier, in FY2023. Here we will discuss our first experience and challenges with running SX in the Delivery Ring.

Slow extraction is an unavoidably lossy process. Primary particles are deemed to intercept the electrostatic septum wires while separating the extracted from the circulating beam. Over the last years, a technique to reduce septum losses has been proposed at CERN for the SPS: shadowing of electrostatic septum via Silicon bent crystals. Very promising results both in dedicated measurements campaign and during normal physics production were shown for the local shadowing concept. In this contribution, we present the latest results at the CERN SPS using non-local shadowing concept to further reduce losses (now achieving a 50% loss reduction), its implementation and expected performance reach.

Uncontrolled beam loss at the electrostatic septum is a performance limit for hadron accelerators delivering slow-extracted beam to fixed-target experiments. The application of numerical optimizers has been shown to reduce such beam loss. The efficiency depends on the parameters to optimize, the details of the extraction process and the used hardware. In this presentation, the minimization of losses by optimizing the extraction efficiency for the present GSI heavy ion synchrotron SIS18 is described. Three different algorithms were used for that – Nelder-Mead, Powell and COBYLA. Varying two parameters of the sextupole settings allows to halve the beam losses. The advantages and limitations are discussed as well as future plans for improvement.

The synchrotrons SIS18 and SIS100 at GSI/FAIR uses resonant extraction for slow beam extraction. The electrostatic extraction septa (ES) utilizes thin wire arrays as anode, which are sensitive to beam loss, especially at low beam energies and for heavy ions, where the energy loss dE/dx is high. Beam loss can lead to high temperatures, where the anode wires break due to reduced mechanical strength. As an example, in 2022, about half of the anode wires at SIS18 were broken during beam operation with high intensity uranium beam. To mitigate further damage, a set-up of protective collimators was recently performed in 2023, to prevent dispersive losses at the anode wires. For SIS100, slow extraction at high intensities of heavy ions up to uranium are foreseen. Losses at extraction energy also can lead to high steady-state temperatures, which depends on the slow extraction parameters, most notably the step size at the ES. In this contribution we discuss machine protection of the electrostatic septa at SIS18 and SIS100, and ideas for future improvement.

Electrostatic septa are critical components in particle accelerators, but operating them can be challenging. Optimizing their settings is key to enhancing beam quality and reducing losses. Recent techniques at CERN focus on minimizing setup time and monitoring spark rates to prevent equipment damage. This talk will share experiences and advancements from CERN, offering valuable insights into improving beam quality and operational efficiency.

The impact of high-flux protons on the inherent beam loss in the slow extraction from SPS towards the North Area has been recently discussed and potential improvements have been proposed. These solutions are mainly aiming to reduce the high component activation and related reduction of lifetime, as well as observed non straightness in the anode body. Recent studies have allowed to demonstrate feasibility of replacing the currently installed stainless steel tank, flanges, and anode body by lowZ materials. The design iteration and material choice has led to the fabrication of a reduced length prototype, demonstrating mechanical, electrical, as well as the vacuum related performance. The results from the full length and prototype design will be compared to the existing system. Furthermore, the optimization of the anode body straightness including results from 3d optical metrology will be discussed.

Mu2e experiment requires 8 GeV proton beam to study rare neutrinoless decays of a muon to an electron. The delivery of 8 spills every 1.4 seconds with 1E12 protons per spill is provided by means of resonant slow extraction. Two electrostatic septa (ESS) have been designed to facilitate the slow extraction. Each septum will have a cathode that is energized to a nominal voltage of 100kV with a gap of 14m to achieve a 2mrad kick. ESS1 is the leading septum with 544 foil strips and one diffuser foil with a cathode length of 133.6cm. ESS2 is the trailing septum with 673 foils with a cathode length 166.4cm. The mechanical design, assembly, conditioning, and installation of the ESS will be discussed in detail.

In 2008, an electrostatic septum was built to a CERN design in industry for the slow extraction in CNAO’s medical accelerator in Pavia. Shortly after it’s installation, several shortcomings revealed themselves, such as limited orbiting beam acceptance and difficulties to operate the displacement system remotely.
In 2020 a collaboration was launched between CERN and CNAO to design a version of the electrostatic extraction septum which mitigates the shortcomings, taking advantage of the latest developments in the field, and upgrade the device to make it suitable for future operational parameters.
This presentation will highlight the innovations implemented and summarise the results of the initial laboratory tests.

Accelerators for ion beam therapy are always based on synchrotrons if ions other than protons are used.
In order to be able to use the raster scanning method, the beam must be slowly extracted from the synchrotron.
This talk summarizes the most important current requirements for slow extraction at medical facilities.
Additionally we ask: What future topics are being discussed a lot in particle therapy and what requirements do they place on slow extraction?

The need for greater flexibility, faster turnaround times, reduced energy consumption, reducing operational cost at maximum physics output and the sheer size of potential future accelerators such as the FCC ask for new particle accelerator operational models with automation at the center. AI/ML is already playing a significant role in the accelerator domain with numerous applications in design, diagnostics and control. This contribution will introduce the building blocks for automating exploitation for the CERN accelerator fleet. These building blocks include classical automation concepts as have been introduced mainly with the LHC and since recently also frameworks that allow full automation of various processes with AI/ML techniques. CERN's vision for the coming years will also be shortly summarised and finally a few operational examples for automation and optimisation in the control room will be shown.

The CERN Super Proton Synchrotron offers slow-extracted, high-intensity proton beams at 400 GeV/c for 3 fixed targets in the CERN North Area hall with a spill length of about 5 s. Various effects are detrimental to the spill quality due to the nature of slow extraction. Some of these spill deterioration sources have been successfully tackled in recent years and for others, projects are ongoing to find solutions (i.e. hysteresis compensation). Continuous compensation of intensity fluctuations at n x 50 Hz from power converter ripples has however been particularly difficult. During the 2023 SPS proton run, the deployment of two techniques - “Empty-Bucket Channelling” and active control with Adaptive Bayesian Optimisation - finally sufficiently suppressed intensity modulations at these frequencies. This paper will focus on Adaptive Bayesian Optimisation for n x 50 Hz control. The chosen algorithm will be discussed and implementation details in the CERN control system will be given. Finally the 2023 results will be presented and next steps summarised.

Protons impacting the electrostatic septum wires produce a significant activation of the septum and its surroundings. Such induced activation is the main limiting factor for the number of protons that can be delivered to the experiments and hence to the physics thruput of the CERN SPS. In this contribution, we present a data-driven model to predict the induced radioactivity around the electrostatic septum from prompt loss readings.

A third-integer resonant slow extraction system is being developed for the Fermilab's Delivery Ring to deliver protons to the Mu2e experiment. During a slow extraction process, the beam on target is liable to experience small intensity variations due to many factors. Owing to the experiment's strict requirements in the quality of the spill, a Spill Regulation System (SRS) is currently under design. The SRS primarily consists of three components - slow regulation, fast regulation, and harmonic content tracker. In this presentation, we shall present the investigations of using Machine Learning (ML) in the fast regulation system, including further optimizations of PID controller gains for the fast regulation, prospects of an ML agent completely replacing the PID controller using supervised learning schemes such as Long Short-Term Memory (LSTM) and Gated Recurrent Unit (GRU) ML models, the simulated impact and limitation of beam pipe's B-field screening bandwidth on both PID and ML regulation of the spill. We also present here nascent results of Reinforcement Learning efforts with and without neuralized PID, including continuous-action actor-critic methods and soft actor-critic methods, to regulate the spill rate.

Slow resonant extraction plays a crucial role in delivering a high-quality continuous beam to experiments. Simulating extraction and transport of charged particle beams from a synchrotron to a transport line require a process of careful modeling and experimentation. There are various particle tracking simulation tools available to use and each has its merits and deficiencies. In this work we have used a long-term tracking program built atop the Bmad software toolkit to run third integer resonant extraction simulations in the booster synchrotron at Brookhaven National Laboratory. In this presentation, we will present results of detailed slow extraction, multi-particle tracking simulations, and we will describe the features that make Bmad a useful tool for this work.

Slow extraction is needed for continuous particle spills from synchrotrons but is inherently lossy due to the non-zero particle density between circulating and extracted beam lines. At CERN's SPS, this results in significant activation of electrostatic septa, making it a highly radioactive area. The current SPS operational parameters and annual slow-extracted protons are already constrained by this activation. With increasing demands for higher intensities and integrated flux, enhancing extraction efficiency and reducing activation are critical, not only for SPS but for all facilities using slow extraction.
This contribution explores the current status and future prospects of supplanting the conventional thin electrostatic septa with innovative crystal technology at the SPS. Initially, we delve into the current performance and potential future capabilities of crystal systems, followed by an examination of some concepts for their practical application. Subsequently, a proposed timeline and a feasible R&D pathway for integrating this technology into the SPS infrastructure are presented.

Bent crystals have become a well-established technology, utilized in diverse accelerator applications at CERN such as the crystal-assisted collimation system in the LHC and loss reduction during slow extraction from SPS using the shadowing technique. Future plans involve employing bent crystals as a key component to measure the electric and magnetic dipole momentum of short-lived particles in a double-crystal experiment within the LHC.
Recognizing the strategic significance of bent crystals in current and upcoming projects, in-house production has been deemed strategically beneficial.
Thus, the DECRYCE (DEvelopment of CRYstals for Collimation and Beam Extraction) project was initiated. It aims to oversee the entire production chain, from the procurement of low-dislocation crystal wafers to cutting specific crystal strips aligned with the crystal lattice planes, designing the bender system, and validating and qualifying crystals using X-ray and particle beams.
This contribution will outline the project's progress status and the results achieved in its first year of activity with an outlook on the slow extraction applications.

The SHERPA (“Slow High-efficiency Extraction from Ring Positron Accelerator”) project aim is to develop an efficient technique to extract a positron beam from one of the accelerator rings composing the DAΦNE accelerator complex at the Frascati National Laboratory of INFN, setting up a new beam line able to deliver positron spills of O(ms) length, excellent beam energy spread and emittance.
The most common approach to slowly extract from a ring is to increase betatron oscillations approaching a tune resonance in order to gradually eject particles from the circulating beam.
SHERPA proposes a paradigm change using coherent processes in bent crystals to kick out positrons from the ring, a cheaper and less complex alternative [1]. This non-resonant technique, already successfully used and still developed mainly in hadron accelerators, will provide a continuous multi-turn extraction of a high quality beam [2, 3, 4, 5].
Realizing this for sub-GeV leptons is challenging, however would provide the world’s first primary positron beam obtained with crystal extraction. An immediate application of this new extracted beam line would be the PADME (“Positron Annihilation into Dark Matter Experiment”) experiment [6], currently strongly limited by the duty cycle. Using the proposed extraction, PADME could increase the statistics by a factor 104 and its sensitivity by a factor 102.
This technology can be applied in general for both negative and positive leptons, including muons, providing a know how that can be applied for several accelerating machine aspects in the next future, as collimation, extraction and beam splitting, contributing to a general improvement in the particle accelerator field.
In the talk will be given an overview of the whole experiment, describing in particular the crystal extraction principle, the accelerator optics studies [7], the crystal prototype and the characterization apparatus. Simulation and experimental results will be reported, together with new future applications.

References:
. [1] M. Biryukov et al, Crystal channeling and its application at high-energy accelerators. Springer Science Business Media, 2013 
17 

. [2] X. Altuna et al, Phis. Lett. B 357 (1995) 671-677 

. [3] A.G. Afonin et al, Phys. Rev. Lett. 87, 094802 (2001) 

. [4] W. Scandale et al, Phys. Lett. B 758 (2016) 129-133 

. [5] M.A. Fraser et al, 8th IPAC, Copenhagen (2017) 

. [6] M. Raggi et al, EPJ Web Conf. 142 (2017) 01026
. [7] M. Garattini et al., Phys. Rev Accel. Beams 25 (2022) 033501

In recent years, mixed helium (He-2+) and carbon ion (C-6+) irradiation schemes have been proposed to facilitate in-vivo range verification in ion beam therapy. Such a scheme implies accelerating and extracting both ion species simultaneously, with the idea of using C-6+ for tumor treatment, while performing real-time dosimetry with He-2+ in a detector downstream of the patient.

The MedAustron center for ion beam therapy and research, which supplies protons and carbon ions for clinical treatment, is currently being commissioned to additionally provide helium ions for nonclinical research. The availability of both He-2+ and C-6+ beams opens the opportunity for studying the feasibility of the described mixed beam irradiation scheme.

A key aspect in this context is the slow extraction of the ion mix, which is affected by both the relative charge-to-mass ratio offset and possible deviations in the transverse phase space distributions. This talk suggests radio frequency knock-out as extraction mechanism and presents Xsuite simulations to discuss challenges and mitigation for maintaining a constant He/C ratio throughout the spill.

The NIMMS Helium Synchrotron is a 30 m circumference ring which provides slow extracted protons and helium ions to a proposed treatment and research facility.
For a state-of-the-art research facility, flexible extraction options are essential. These options include having high intensity pulses, and variable timescale pulses to investigate radiobiological FLASH effects.
A variety of different extraction methods are explored with the compact Helium Synchrotron optics to investigate the most promising options to be incorporated into the NIMMS TDR. Simulations demonstrate those methods on the scale of 100 ms of spill.

Improved slow extraction beam stability can be achieved by better control of the magnet power supply currents. However, the required performance exceeds capabilities of available current measurement systems. Within the IFast collaboration, such an improved current measurement system is being developed. This presentation summarizes the requirements, the solution under development and achieved performance.

MedAustron is an ion therapy facility for protons and carbon ions located in Wiener Neustadt, Austria. The beam is presently extracted for clinical operation from the synchrotron with third-order resonant slow extraction via acceleration with a betatron core. However, due to the flexibility of the synchrotron operation for Non Clinical Research (NCR) purposes, other extraction methods can be investigated for potential improvement of the machine performance as presented in this work.
Radio-Frequency Knock Out (RFKO) extraction was investigated by applying an RF signal voltage across the horizontal Schottky plates in the synchrotron. Different excitation signals were evaluated with the required transverse excitation frequency band applied.
Investigation of the synchronous ramping of all synchrotron magnets for extraction via Constant Optics Slow Extraction operation (COSE) was undertaken for a bunched beam in order to extend the implementation of COSE with possible Multi Energy Extraction (MEE).
The last extraction method presented here is via longitudinal RF manipulation in order to extract the beam by sweeping a properly configured empty bucket through the beam stack. This method is known as Phase Displacement Extraction (PDE).
Extraction rates with these methods were observed which meet the clinical requirements and might also be considered compatible with FLASH.

This presentation provides an overview of the current simulation framework used at MedAustron to simulate the multi-energy extraction process. These simulations aim to assist in the commissioning of a potential future implementation of MEE at MedAustron. The recent improvements in the Xsuite tracking code facilitate the simulation of beam re-acceleration, including all the necessary dynamic changes in the lattice to perform RF-knockout slow extraction. This study presents an example of a Xsuite-based MEE simulation applied to the MedAustron synchrotron.

The excitation signals used in Radio Frequency Knock Out (RF KO) resonant slow extraction influence the temporal structure of the resulting spill. Therefore, a careful design of excitation signals is crucial to prevent artificial ripples in the spill caused by the excitation. At the same time, tailored signals can suppress ripples introduced by external sources such as power converters.
This contribution presents simulation studies which yield insight into the particle dynamics of the excited system and lead to the proposal of an improved excitation method. The new method is experimentally compared with other commonly applied techniques, explaining their respective advantages and drawbacks.

Radio-frequency (RF) techniques can be utilised to provide a tailored time structure to slow extraction users. In this contribution, a manipulation known as RF phase displacement is presented as a way of satisfying two different beam requests: (i) ~millisecond-scale spills for FLASH therapy/Radiation-to-Electronics users, and (ii) ~second-scale spills with nanosecond bunching for a dark-matter search experiment known as SHiP. Simulation results and measurements are compared in order to characterise the technique.