Study of slow and fast extraction for the ultralow energy storage ring (USR)

The Facility for Antiproton and Ion Research (FAIR, GSI) will not only provide future users with high fluxes of antiprotons in the high-energy range, but it is also intended to include a dedicated program for low-energy antiproton research in the keV regime, realized with the FLAIR project. The deceleration of antiprotons with an initial energy of 30 MeV down to ultralow energies of 20 keV will be realized in two steps. First, the beam is cooled and slowed down to an energy of 300 keV in a conventional magnetic ring, the Low energy Storage Ring (LSR) before being transferred into the electrostatic Ultralow energy Storage Ring (USR). In this synchrotron the deceleration to a final energy of 20 keV will be realized. This paper describes the ion-beam optical and mechanical layout of the beam extraction from the USR and summarizes the expected beam qualities of extracted beams.     

FLAIR – a facility for low-energy antiproton and ion research

In order to exploit the unique possibilities that will become available at the Facility for Antiproton and Ion Research (FAIR) at GSI in Darmstadt, a collaboration of about 50 institutes from 15 countries was formed to efficiently enable an innovative research program towards low-energy antimatter-physics. In the Facility for Low-energy Antiproton and Ion Research (FLAIR) antiprotons and heavy (radioactive) ions are slowed down from 30 MeV to energies as low as 20 keV by a magnetic low-energy storage ring (LSR) and an electrostatic ultra-low energy storage ring (USR) or are even brought to rest by a universal trap facility (HITRAP). In this paper, the facility and the research program covered are briefly described with some emphasis on the accelerator chain and the expected particle numbers. for the FLAIR collaboration     

Perspectives for low energy antiproton physics at FAIR

The CRYRING accelerator, previously located at the Manne Siegbahn Laboratory of Stockholm University, has been chosen by the FLAIR collaboration as the central accelerator for the planned facility. It has been modified to allow for high-energy injection and extraction and is capable of providing fast and slow extracted beams of antiprotons and highly charged ions. It is currently being installed at the ESR of GSI Darmstadt where it can be used with highly charged ions. The future possibilities for its use with slow antiprotons will be discussed.     

SPARC collaboration: new strategy for storage ring physics at FAIR

SPARC collaboration at FAIR pursues the worldwide unique research program by utilizing storage ring and trapping facilities for highly-charged heavy ions. The main focus is laid on the exploration of the physics at strong, ultra-short electromagnetic fields including the fundamental interactions between electrons and heavy nuclei as well as on the experiments at the border between nuclear and atomic physics. Very recently SPARC worked out a realization scheme for experiments with highly-charged heavy-ions at relativistic energies in the High-Energy Storage Ring HESR and at very low-energies at the CRYRING coupled to the present ESR. Both facilities provide unprecedented physics opportunities already at the very early stage of FAIR operation. The installation of CRYRING, dedicated Low-energy Storage Ring (LSR) for FLAIR, may even enable a much earlier realisation of the physics program of FLAIR with slow anti-protons.     

Ultra-low energy storage ring at FLAIR

The Ultra-low energy electrostatic Storage Ring (USR) at the future Facility for Low-energy Antiproton and Ion Research (FLAIR) will provide cooled beams of antiprotons in the energy range between 300 keV down to 20 keV and possibly less. The USR has been completely redesigned over the past three years. The ring structure is based on a “split achromat” lattice that allows in-ring experiments with internal gas jet target. Beam parameters might be adjusted in a wide range: from very short pulses in the nanosecond regime to a Coasting beam. In addition, a combined fast and slow extraction scheme was developed that allows for providing external experiments with cooled beams of different time structure. Detailed investigations of the USR, including studies into the ring’s long term beam dynamics, life time, equilibrium momentum spread and equilibrium lateral spread during collisions with an internal target were carried out. New tools and beam handling techniques for diagnostics of ultra-low energy ions at beam intensities less than 10⁶ were developed by the QUASAR Group. In this paper, progress on the USR project will be presented with an emphasis on the expected beam parameters available to the experiments at FLAIR.     

Electrostatic ultra-low-energy antiproton recycling ring

There is a strong need to push forward developments in the storage and control of ultra-low-energy antiproton beams to enable important scientific research. To this end, a small electrostatic ring, and associated electrostatic acceleration section, is being designed and developed by the QUASAR group. The ring will be placed on the MUSASHI beamline at the CERN-AD. It will serve as a prototype for the future ultra-low energy storage ring (USR), to be integrated at the facility for low-energy antiproton and ion research (FLAIR) and will enable various components of the USR to be tested and optimised. A reaction microscope will be integrated in the ring to enable partial ionisation cross section measurements to be made. This small recycler ring will be unique due to its combination of size, electrostatic nature and energy and type of circulating particles (ca 3?C30 keV antiprotons). A short electrostatic accelerating section is also being developed, which will be placed between the beamline and the ring to accelerate the antiprotons from the trap extraction energy (typically 250 eV) to the final required (re-circulating) energy. The AD recycler project will be described, including ring design, accelerating injection section and the inclusion of a reaction microscope and the experiments it will enable.     

Present status of the USR project

The Facility for Low-energy Antiproton and Ion Research (FLAIR) and a large part of the wide physics program decisively rely on new experimental techniques to cool and slow down antiprotons to 20 keV, in particular on the development of an ultra-low energy electrostatic storage ring (USR). The whole research program connected with anti-matter/matter interactions is only feasible if such a machine will be realized. For the USR to fulfil its key role in the FLAIR project, the development of novel and challenging methods and technologies is necessary: the combination of the electrostatic storage mode with a deceleration of the stored ions from 300 keV to 20 keV, electron cooling at all energies in both longitudinal and transverse phase-space, bunching of the stored beam to ultra-short pulses in the nanosecond regime and the development of an in-ring reaction microscope for antiproton-matter rearrangement experiments. In this contribution, the present status of the USR project is summarized and the new machine lattice is presented.     

Preliminary design studies of an extraction of the USR

The next-generation Facility for Low energy Antiproton and Ion Research (FLAIR) at GSI is going to be a dedicated research facility for ion research in the keV range. These ion beams will allow to explore fundamental properties in matter-antimatter research at ultra-low energies of only 20 keV/q in hitherto impossible experiments. To provide these very low energy beams, the Ultra-low energy Storage Ring (USR), an electrostatic synchrotron, will play a major role within the FLAIR complex. It combines the electrostatic storage mode with deceleration from an initial energy of 300 keV/q down to 20 keV/q—as well as an efficient beam cooling. To fulfill its role as a multi-purpose experimental facility, the design of the USR has not only to cover in-ring experiments, but needs to include a highly flexible beam extraction for serving different external experiments as well.     

Double-strangeness production with antiprotons

The production of double-strangeness by antiproton annihilation in nuclei will be an exciting way to investigate whether the formation of deeply bound antikaonic nuclear clusters occurs. The existence of deeply bound antikaonic nuclear clusters is a lively debated problem in hadron physics today, which can be solved only experimentally. At CERN with the Antiproton Decelerator (AD) and in future with the new FAIR facility at Darmstadt low energy antiprotons are available to perform this type of experiments. The use of antiprotons for the production of double-strangeness was recently discussed by Weise and Kienle and indeed, it would be very challenging to produce and study such “double-strange nuclei” in the view of the prediction of Akaishi and Yamazaki that double-antikaon bound nuclear systems with strangeness (S?=???2) will be formed with binding energies up to 200–300 MeV. Such binding energies might result in an increase of the average density to more than 3 times the average nuclear density. If such dense systems are created, conditions in the phase diagram might be reached where phase transition to kaon condensation or colour superconductivity will occur at low temperature.     

AD: low-energy antiproton production at CERN

Well into its 10th year of running for physics, the Antiproton Decelerator (AD) supplies antiprotons to 4 different physics collaborations: ATRAP, ALPHA, ASACUSA and ACE. Antiprotons are injected at 3.5 GeV/c, then cooled and decelerated before being extracted at 100, 300 or 500 MeV/c in single or multi-batch mode. Here we will discuss the challenges of keeping reliability and performance at adequate levels, prospects of future physics scheduling and also possible additional experiments and machine improvements.     

Beam instrumentation for the Ultra-low energy Storage Ring (USR)

The electrostatic Ultra-low energy Storage Ring (USR) at the future Facility for Low energy Antiproton and Ion Research (FLAIR) will make available antiprotons from 300?keV down to 20?keV beam energy. This multipurpose machine puts challenging demands on the beam instrumentation due to the varied bunch structure (ultra-short bunches of 1?C2?ns up to a quasi-DC beam structure on the other), together with variable very low beam energies, ultra-low currents of down to 1?nA (or even less in the transfer lines which means less than 2 × 10⁷ particles). Thus, the development of new diagnostic devices is required as most of the standard techniques are not suitable. Within the QUASAR Group, the necessary beam instrumentation for the commissioning phase and standard operation of the USR, as well as advanced techniques such as a gas curtain-jet beam profile monitor, have been developed and prototypes of all devices have been built up. This paper presents the design of all beam diagnostics devices for the USR and summarizes the results from first measurements.     

Cross-beam atomic collision experiment between ultra-low-energy antiprotons and a supersonic gas jet

The antiproton is a unique projectile in the study of atomic collision physics. With an aim to produce an antiproton beam at atomic-physics energies for ‘pure’ collision experiments, we have so far developed techniques to decelerate, cool and confine antiprotons in vacuo. Our recent success in stable extraction of the beam has opened up the possibility to study ionization and atomic capture processes between an antiproton and an atom at an unprecedented low energy from 10 eV to 1 keV under the single-collision condition. We have prepared a powerful supersonic helium gas jet to be crossed with the antiproton beam. The reaction rate is of the order of 10^???4, and rigorous identification of particles is required for reduction of huge background counts. The reaction events are recognized by an electron signal followed by antiproton annihilation with an appropriate interval in the time of flight. Our design and strategy of the experiment are presented.     

In-flight antiproton annihilation on nuclei at low energies

The results of the annihilation cross sections measurement of 5.3 MeV antiprotons on nickel, tin, platinum and Mylar targets performed by the ASACUSA Collaboration at CERN are presented and compared with the existing data and models. From the experimental point of view the presented data are the first measurement of antinucleon annihilation cross sections at low energies obtained with a pulsed beam. This results open the road for the next measurements at the very low energies of the order of 100 keV that are in progress by the ASACUSA Collaboration. The experimental method foreseen for the 100 keV measurement is illustrated.     

The ISAC post-accelerator

The acceleration chain of the ISAC facility boosts the energy of both radioactive and stable light and heavy ions for beam delivery to both a medium energy area in ISAC-I and a high energy area in ISAC-II. The post-accelerator comprises a 35.4 MHz RFQ to accelerate beams of A/q ≤ 30 from 2 keV/u to 150 keV/u and a post stripper, 106.1 MHz variable energy drift tube linac (DTL) to accelerate ions of A/q ≤ 6 to a final energy between 0.15 MeV/u to 1.5 MeV/u. A 40 MV superconducting linac further accelerates beam from 1.5 MeV/u to energies above the Coulomb barrier. All linacs operate cw to preserve beam intensity.     

Hadron physics with PANDA

The PANDA experiment at the new FAIR facility has a dedicated program of utilizing antiprotons for hadron physics. It belongs to the group of core experiments, which will be realized at the first stages of the facility. PANDA will be a universal detector to study the strong interaction by utilizing the annihilation process of antiprotons with protons and nuclear matter. The past few years have been used by the collaboration to do extensive detector R&D and to sharpen the physics case. This paper gives an introduction into the hadron physics with antiprotons as it is planned with PANDA.     

Beam life time studies and design optimization of the Ultra-low energy Storage Ring

The Ultra-low energy electrostatic Storage Ring (USR) at the future Facility for Low-energy Antiproton and Ion Research (FLAIR) will provide cooled beams of antiprotons in the energy range between 300 keV down to 20 keV. Based on the original design concept developed in 2005, the USR has been completely redesigned over the past few years by the QUASAR Group. The ring structure is now based on a ’split achromat’ lattice. This ensures compact ring dimensions of 10 m × 10 m, whilst allowing both, in-ring experiments with gas jet targets and studies with extracted beams. In the USR, a wide range of beam parameters shall be provided, ranging from very short pulses in the nanosecond regime to a coasting beam. In addition, a combined fast and slow extraction scheme will be featured that allows for providing external experiments with cooled beams of different time structure. Detailed investigations into the dynamics of low energy beams, including studies into the long term beam dynamics and ion kinetics, beam life time, equilibrium momentum spread and equilibrium lateral spread during collisions with an internal target were carried out. This required the development of new simulation tools to further the understanding of beam storage with electrostatic fields. In addition, studies into beam diagnostics methods for the monitoring of ultra-low energy ions at beam intensities less than 10 ⁶ were carried out. This includes instrumentation for the early commissioning of the machine, as well as for later operation with antiprotons. In this paper, on overview of the technical design of the USR is given with emphasis on two of the most important operating modes, long term beam dynamics and the design of the beam diagnostics system.     

Recombination experiments at CRYRING

Recent advances in studies of electron-ion recombination processes at low relative energies with the electron cooler of the heavy-ion storage ring CRYRING are shown. Through the use of an adiabatically expanded electron beam, collisions down to 10^-4eV relative energies were measured with highly charged ions stored in the ring at around 15 MeV/amu energies. Examples of recombination measurements for bare ions of D⁺, He²⁺, N⁷⁺, Ne¹⁰⁺ and Si¹⁴⁺ are presented. Further on, results of an experiment measuring laser-induced recombination (LIR) into n=3 states of deuterium with polarized laser light are shown. This revised version was published online in July 2006 with corrections to the Cover Date.     

An intense source of antiprotons for antimatter research at FNAL

There is considerable interest in low energy antiprotons for atomic, nuclear, and particle physics. The LEAR facility at CERN is currently the only source of antiprotons with low enough energy to be stored and accumulated in a Penning trap. With only minimal hardware modifications, the Fermilab Linac and Booster synchrotron can be used to decelerate an initial ensemble of 10¹¹ antiprotons with an efficiency of approximately 0.5%. Subsequent improvements will be able to increase this efficiency to near 100% transmission of 10¹² antiprotons. These transfers could take place as often as two or three times a day with only a marginal decrease in Tevatron Collider luminosity. This revised version was published online in August 2006 with corrections to the Cover Date.     

The future of the cern ad infrastructures in the context of elena machine design and integration

ELENA will lower the energy of AD antiprotons from 5MeV to 100keV, thus increasing by a factor of up to 100 the number of antiprotons usable by the experiments (Oelert et al. 2014). The AD infrastructures must be adapted to cope with another 20 years of low energy antiproton physics. To fit the ELENA ring in the already crowded AD hall, old kicker generators must be relocated to a new technical building, existing and new services and racks must be re-arranged also at height, preserving access and maintenance capabilities. The ELENA beam will be delivered to existing experiments via new transfer lines without compromising the possibility to maintain a visitors path to this very popular place at CERN. New experimental areas being designed to house new experiments (GBAR, BASE), and re-arrangement for future experiments (cleaning rooms relocation in the new technical building, control rooms in a separate building with a cafeteria and a conference room) are also detailed.     

Particle detectors for the future antiproton Paul trap of the ASACUSA experiment at CERN

Two detectors which will be used to commission a superconducting radiofrequency Paul trap for antiprotons, now being constructed at CERN and MPQ, are described. One is a microwire secondary electron emission monitor which will nondestructively measure the spatial profile of a low energy (E= 10?100 keV) antiproton beam. The other is a system of electromagnetic shower counters which will detect the secondary particles emerging from the antiproton annihilations occurring in the trap.