Facility For Antiproton Research Articles

Stimulated Recovery of the Radiation Damage in Lead Tungstate Crystals

The lead tungstate crystal (PbWO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> , PWO) is one of the widely used scintillation materials for electromagnetic calorimeters (EMCs) in high-energy physics experiments. The degradation of the optical transmittance in the range of the luminescence spectrum under ionizing radiation leads to losses of the light output resulting in the deterioration of the energy resolution and limiting the lifetime of the calorimeter. A possible way to restore radiation damage is the in situ illumination by visible or near-infrared light of the whole crystal volume. It allows recovering the transmittance losses due to the depopulation of the color centers. Such a kind of stimulated recovery subsystem based on a blue light-emitting diode is considered for the EMC of the PANDA detector at Facility for Antiproton and Ion Research (FAIR) (Darmstadt, Germany). Here, we report on the stimulated recovery studies of the lead tungstate radiation damage induced by external light from laser diodes at different wavelengths. The level of technological development of laser diodes allows increasing the efficiency of the stimulated recovery.

FAIR: The Future European Facility for Antiproton And Ion Research

FAIR, the new international Facility for Antiproton and Ion Research at GSI, will cover a broad spectrum of hadronic, nuclear, and atomic physics research and appli- cation. A system of synchrotrons will provide intense proton and heavy ion beams of intermediate energy with the option to produce secondary beams of radioactive nuclei and antiprotons. NUSTAR, NUclear STructure, Astrophysics and Reactions, will play a premier role within the FAIR research program. Nuclei at the limits of binding will become accessible and new probes for reaction studies with unstable nuclei become available.

A Flexible Search Coil Set-Up for Magnetic Measurements of Accelerator Dipole Magnets

Search coils are used for fast and reliable measurements of field integrals as well as integral homogeneities of dipole magnets. A long experience exists at GSI Helmholtzzentrum fur Schwerionenforschung (GSI) using search coils in series measurements of synchrotron dipoles as well as measurements of dipoles with large deflecting angles. The biggest advantage of this technique is a direct and fast measurement of the field integral. Current technology, however, always required a dedicated coil for each bending radius and length. A prominent example is High Energy Beam Transfer (HEBT) of the Facility for Antiproton and Ion Research (FAIR) project with 6 different radii between 4.5 m and 167 m. In addition to the 6 coils, radius dependent moving and guiding systems are necessary. To overcome the above mentioned drawbacks we developed a modular search coil system with adjustable radius including the support and movement system. The features of the system and measurement results are presented.

Studies of equation of state properties of high-energy-density matter generated by intense ion beams at the facility for antiprotons and ion research.

The work presented in this paper shows with the help of two-dimensional hydrodynamic simulations that intense heavy-ion beams are a very efficient tool to induce high energy density (HED) states in solid matter. These simulations have been carried out using a computer code BIG2 that is based on a Godunov-type numerical algorithm. This code includes ion beam energy deposition using the cold stopping model, which is a valid approximation for the temperature range accessed in these simulations. Different phases of matter achieved due to the beam heating are treated using a semiempirical equation-of-state (EOS) model. To take care of the solid material properties, the Prandl-Reuss model is used. The high specific power deposited by the projectile particles in the target leads to phase transitions on a timescale of the order of tens of nanosecond, which means that the sample material achieves thermodynamic equilibrium during the heating process. In these calculations we use Pb as the sample material that is irradiated by an intense uranium beam. The beam parameters including particle energy, focal spot size, bunch length, and bunch intensity are considered to be the same as the design parameters of the ion beam to be generated by the SIS100 heavy-ion synchrotron at the Facility for Antiprotons and Ion Research (FAIR), at Darmstadt. The purpose of this work is to propose experiments to measure the EOS properties of HED matter including studies of the processes of phase transitions at the FAIR facility. Our simulations have shown that depending on the specific energy deposition, solid lead will undergo phase transitions leading to an expanded hot liquid state, two-phase liquid-gas state, or the critical parameter regime. In a similar manner, other materials can be studied in such experiments, which will be a very useful addition to the knowledge in this important field of research.

Status of the Compressed Baryonic Matter experiment at FAIR

The Compressed Baryonic Matter (CBM) experiment will investigate high-energy heavy-ion collisions at the international Facility for Antiproton and Ion Research (FAIR), which is under construction in Darmstadt, Germany. The CBM research program is focused on the exploration of QCD matter at neutron star core densities, such as study of the equation-of-state and the search for phase transitions. Key experimental observables include (multi-) strange (anti-) particles, electron-positron pairs and dimuons, particle correlations and fluctuations, and hyper-nuclei. In order to measure these diagnostic probes multi-differentially with unprecedented precision, the CBM detector and data acquisition systems are designed to run at reaction rates up to 10 MHz. This requires the development of fast and radiation hard detectors and readout electronics for track reconstruction, electron and muon identification, time-of-flight (TOF) determination and event characterization. The data are read-out by ultra-fast, radiation-tolerant, and free-streaming front-end electronics, and then transferred via radiation-hard data aggregation units and high-speed optical connections to a high-performance computing center. A fast and highly parallelized software will perform online track reconstruction, particle identification and event analysis. The components of the CBM experimental setup will be discussed and results of physics performance studies will be presented.

Simultaneous muon and reference hadron measurements in the compressed baryonic matter experiment at FAIR

The mission of the Compressed Baryonic Matter (CBM) experiment at the future Facility for Antiproton and Ion Research (FAIR) in Darmstadt is to explore the QCD phase diagram at high net baryon densities likely to exist in the core of neutron stars. The CBM detector system is designed to perform multi-differential measurements of hadrons and leptons in central gold-gold collisions at beam energies between 2 and 11 A GeV with unprecedented precision and statistics. In order to reduce the systematic errors of the lepton measurements, which generally suffer from a large combinatorial background, both electrons and muons will be measured with the same acceptance. Up to now, no di-muon measurements have been performed in heavy-ion collisions at beam energies below 158 A GeV. The main device for electron identification, a Ring Imaging Cherenkov (RICH) detector, can be replaced by a setup comprising hadron absorbers and tracking detectors for muon measurements. In order to obtain a complete picture of the reaction, it is important to measure simultaneously leptons and hadrons. This requirement is fulfilled for the RICH, which has a low material budget, and only little affects the trajectories of hadrons on their way to the Time-of-Flight (TOF) detector. In contrast, the simultaneous measurement of muons and hadrons within the same experimental acceptance poses a substantial challenge. This article reviews the simulated performance of the CBM experiment for muon identification, together with the possibility of simultaneous hadron measurements.

Electromagnetic form factors of the transition from the spin-3/2 Σ to the Λ hyperon

The three electromagnetic form factors for the transition from a $3/{2}^{+}\phantom{\rule{4pt}{0ex}}{\mathrm{\ensuremath{\Sigma}}}^{*}$ hyperon to the ground-state $\mathrm{\ensuremath{\Lambda}}$ hyperon are studied. At low energies, combinations of the transition form factors can be deduced from Dalitz decays of the ${\mathrm{\ensuremath{\Sigma}}}^{*}$ hyperon to $\mathrm{\ensuremath{\Lambda}}$ plus an electron-positron pair. It is pointed out how more information can be obtained with the help of the self-analyzing weak decay of the $\mathrm{\ensuremath{\Lambda}}$. In particular, it is shown that these transition form factors are complex quantities already in this kinematical region. Such measurements are feasible at hyperon factories such as, for instance, the Facility for Antiproton and Ion Research (FAIR). At higher energies, the transition form factors can be measured in electron-positron collisions. The transition form factors are related to decay distributions and differential cross sections. Using dispersion theory, the low-energy electromagnetic form factors for the ${\mathrm{\ensuremath{\Sigma}}}^{*}$-to-$\mathrm{\ensuremath{\Lambda}}$ transition are related to the pion vector form factor. The additionally required input, i.e., the two-pion--${\mathrm{\ensuremath{\Sigma}}}^{*}$--$\mathrm{\ensuremath{\Lambda}}$ amplitudes, is determined from relativistic next-to-leading-order (NLO) baryon chiral perturbation theory, including the baryons from the octet and the decuplet. A poorly known NLO parameter is fixed to the experimental value of the ${\mathrm{\ensuremath{\Sigma}}}^{*}\ensuremath{\rightarrow}\mathrm{\ensuremath{\Lambda}}\ensuremath{\gamma}$ decay width. Pion rescattering is taken into account by using dispersion theory and solving a Muskhelishvili-Omn\`es equation. Subtracted and unsubtracted dispersion relations are discussed. However, in view of the fact that the transition form factors are complex quantities, the current data situation does not allow for a full determination of the subtraction constants. To reduce the number of free parameters, unsubtracted dispersion relations are used to make predictions for the transition form factors in the low-energy space- and timelike regions.

Numerical analysis of cooldown of large magnets for low energy beam line for Facility for Antiproton and Ion Research

Numerical analysis of cooldown of large magnets for low energy beam line for Facility for Antiproton and Ion Research

Exploring Cosmic Matter in the Laboratory—The Compressed Baryonic Matter Experiment at FAIR

The Compressed Baryonic Matter (CBM) experiment is one of four scientific pillars of the future Facility for Antiproton and Ion Research (FAIR) in Darmstadt. In collisions between heavy nuclei at FAIR energies, it is expected that the matter in the reaction zone is compressed to more than five times saturation density, corresponding to the density in the core of a massive neutron star. This offers the unique opportunity to study in the laboratory the high-density equation-of-state (EOS) of nuclear matter, and to search for new phases of Quantum Chromo Dynamics (QCD) matter at large baryon-chemical potentials. Promising experimental observables sensitive to the EOS and to possible phase transitions will be discussed, together with a brief description of the CBM experiment.

Status of high intensity proton injector for Facility for Antiproton and Ion Research.

The high intensity proton injector for the international accelerator Facility for Antiproton and Ion Research located at GSI-Darmstadt in Germany consists of a pulsed 2.45 GHz microwave ion source, a Low Energy Beam Transport (LEBT), and an electrostatic chopper matching the proton beam to the radio frequency quadrupole. The ion source is based on electron cyclotron resonance plasma production and it has to provide a proton beam at 95 keV energy and up to 100 mA current. The LEBT system with two short solenoids each including two magnetic steerers will transport the proton beam into the compact proton linac, accelerating it to the energy of 68 MeV and serving as the injector of the upgraded heavy ion synchrotron (SIS18). This paper describes the commissioning of the proton injector including beam characterization measurements that have been done at CEA/Saclay in France and is currently at the final commissioning stage.

Megaprojects: 2 Facility for Antiproton and Ion Research

The second article of the series on megaprojects presents FAIR prospects for seamless experimentation across the nuclear landscape, and more; FAIR offers facilities to explore exotic plasma, nuclei and materials! Details of the scientific programme, technological challenges, present status and future plans of FAIR are presented. India’s role as the third largest contributing country in FAIR GmbH is highlighted. Outreach activities and avenues to work in FAIR are discussed in detail.

System size dependence of net-charge fluctuation in nucleus-nucleus collisions at FAIR energies

Dynamical net-charge fluctuations are studied in symmetric nuclear collisions of different system size and at two different collision energies that in the near future will be available at the Facility for Antiproton and Ion Research (FAIR). Multiparticle emission data simulated by the ultra-relativistic quantum molecular dynamics (UrQMD) are analyzed for this purpose. Our primary objective is to examine the system size dependence of dynamical fluctuation of conserved charge at typical FAIR conditions. The centrality, pseudorapidity interval size and azimuthal angle interval size dependence of the dynamical fluctuations are studied too. The effects of global charge conservation (GCC) and finite multiplicity bin width correction are taken into account. To a large extent the systematics followed by the dynamical fluctuations at FAIR conditions are found to be a lower energy extrapolation of the observations made in this regard in the Relativistic Heavy-ion Collider (RHIC) experiments.

Anisotropic flow of charged and identified hadrons at FAIR energies and its dependence on the nuclear equation of state

In this article, we examine the equation of state (EoS) dependence of the anisotropic flow parameters ($v_{1}$, $v_{2}$ and $v_{4}$) of charged and identified hadrons, as a function of transverse momentum ($p_{\rm T}$), rapidity ($y_{c.m.}$) and the incident beam energy ($\rm E_{\rm Lab}$) in mid-central Au + Au collisions in the energy range $\rm E_{\rm Lab} = 6 -25$ A GeV. Simulations are carried out by employing different variants of the Ultra-relativistic Quantum Molecular Dynamics (UrQMD) model, namely the pure transport (cascade) mode and the hybrid mode. In the hybrid mode, transport calculations are coupled with the ideal hydrodynamical evolution. Within the hydrodynamic scenario, two different equations of state (EoS) viz. Hadron gas and Chiral + deconfinement EoS have been employed separately to possibly mimic the hadronic and partonic scenarios, respectively. It is observed that the flow parameters are sensitive to the onset of hydrodynamic expansion of the fireball in comparison to the pure transport approach. The results would be useful as predictions for the upcoming low energy experiments at Facility for Antiproton and Ion Research (FAIR) and Nuclotron-based Ion Collider fAcility (NICA).

Charge stripping at high energy heavy ion Linacs

For each heavy-ion accelerator facility charge stripping is a key technology – the stripping charge state, its efficiency to produce ions in the selected charge state, and the beam quality after stripping substantially determine the entire accelerator performance. Modern heavy ion accelerator facilities such as the future Facility for Antiproton and Ion Research (FAIR) at GSI, Darmstadt, Germany provide for high-intensity heavy-ion beams beyond 200 MeV/u. Heavy ions generated in an ion source at comparatively low charge states are pre-accelerated in a Linac to a few MeV/u, after charge stripping the average charge state is increased and one (or several) ion charge states are selected for further acceleration. This enables more efficient acceleration up to the final beam energy, compared to acceleration of ions with a low charge state. C-foil stripping allows for highest mean charge state and best stripping efficiency into the desired charge state. Therefore minimum acceleration voltage could be expected utilizing C-foil stripping. Due to the high power deposited by the ions in the stripping media and radiation damages if solids are used, self-recovering stripper media must be used in any case. First layout scenarios for a 200 MeV/u heavy ion Linac considering efficient heavy ion stripping will be presented.

The Silicon Tracking System of the CBM Experiment at FAIR

The Compressed Baryonic Matter (CBM) experiment at the future Facility for Antiproton and Ion Research (FAIR) aims to study the properties of nuclear matter at high net-baryon densities and moderate temperatures.The Silicon Tracking System (STS) is the key detector to reconstruct with a high efficiency up to 1000 charged particle trajectories created in heavy-ion collisions at interaction rates of up to 10 MHz. It will determine the momentum of the particles with a momentum resolution Δp/p ≈ 1-2% which requires ultra-low detector material budget of 0.3-1% X0 per layer. The detector comprise eight layers of double-sided silicon micro-strip sensors and will be placed inside the 1 Tm superconducting magnet which limits the space available, which in turn requires advanced cooling approaches and mechanical design with precise tracking layers alignment. The micro-strip sensors have to be radiation hard and checked for their quality optically and electrically before the assembly.This contribution gives an overview of the STS and presents the status of its component quality control and assembly procedures.

Experimental study of residual activity induced in aluminum targets irradiated by high-energy heavy-ion beams: A comparison of experimental data and FLUKA simulations

A number of heavy-ion accelerators are either under construction (e.g., the Facility for Antiproton and Ion Research in Darmstadt and the High Intensity Accelerator Facility in China) or already in operation at many places worldwide. For these accelerators, activation of construction components due to beam loss, even during routine machine operation, is a serious issue, especially with the upcoming high-intensity facilities. Aluminum is one of the most commonly used construction materials in beam lines, collimators, and other components. Therefore, we report here on activation experiments on aluminum samples to verify and benchmark simulation codes. The analysis was performed by gamma spectroscopy of the irradiated targets. Our results on the induced activity measured in samples irradiated by uranium beams at 125 MeV/u and 200 MeV/u and a xenon beam at 300 MeV/u show activation levels significantly lower than those predicted by FLUKA simulations.

A timing RPC with low resistive ceramic electrodes

For precise start time determination a Beam Fragmentation T0 Counter (BFTC) is under development for the Time-of-Flight Wall of the Compressed Baryonic Matter Spectrometer (CBM) at the Facility for Antiproton and Ion Research (FAIR) at Darmstadt/Germany. This detector will be located around the beam pipe, covering the front area of the Projectile Spectator Detector. The fluxes at this region are expected to exceed 105cm−2s−1. Resistive plate chambers (RPC) with ceramic composite electrodes could be use because of their high rate capabilities and radiation hardness of material. Efficiency ≥ 97 %, time resolution ≤ 90 ps and rate capability ≥ 105cm−2s−1 were confirmed during many tests with high beam fluxes of relativistic electrons. We confirm the stability of these characteristics with low resistive Si3N4/SiC floating electrodes for a prototype of eight small RPCs, where each of them contains six gas gaps. The active RPC size amounts 20×20 mm2 produced on basis of Al3O2 and Si3N4/SiC ceramics. Recent test results obtained with relativistic electrons at the linear accelerator ELBE of the Helmholtz-Zentrum Dresden-Rossendorf with new PADI-10 Front-end electronic will be presented.

Simulation study of the reaction with PANDA at FAIR

The PANDA experiment will be one of the pillars of the new Facility for Antiproton and Ion Research (FAIR), which is currently under construction in Darmstadt, Germany. PANDA will be a fixed-target experiment which will allow the study of non-perturbative phenomena of the strong interaction. These will be probed in antiproton-proton collisions in the momentum range of 1.5 - 15 GeV/c. Within the PANDA physics program, strangeness production will be addressed through processes. Measurements of the channel for its comparison with the existing data of the channel are highly encouraged to study the role of isospin symmetry in hadron production dynamics. This work consists on a simulation study focusing on the feasibility of measuring the channel at PANDA.

Final Design of the Superferric Branched Dipoles for the FAIR Super-FRS

The superconducting fragment separator (Super-FRS) of facility for antiproton and ion research (FAIR) located in Darmstadt, Germany, requires three branched superferric dipoles which are more complex than the 21 standard dipoles already designed by Commissariat l’Energie Atomique et aux nergies alternatives (CEA). The 50-ton branched dipoles allow the beam of particles to be directed towards the different branches of the separator. The final design proposed by CEA Paris-Saclay for these dipoles integrates features required for the installation of the Y-shaped vacuum chamber which have an impact on the magnetic and mechanical design of the magnet. The coil casing design was modified and the cold-to-warm supports had to be reorganized to contain the Laplace forces acting on the weakened mechanical structure. Cryogenic experiments have been conducted to characterize the behavior of the active thermosiphon concept and to validate the cryogenic design proposed last year. We present in this paper the final design for the FAIR Super-FRS branched dipole magnets along with the design simulation results (magnetic, cryogenic, and mechanical analyses) and the main results of the active thermosiphon tests conducted recently.

Opportunities for measurements of astrophysical‐relevant alpha‐capture reaction rates at CRYRING@ESR

The heavy‐ion storage ring CRYRING@ESR has recently been installed and commissioned at GSI as one of the first installations of the upcoming Facility for Antiproton and Ion Research (FAIR). It is designed to store highly charged ions in the energy range between 300 keV/u and about 10 MeV/u. It will incorporate a gas‐jet target providing high‐density jets of, among other gases, hydrogen and helium. This will allow to study alpha‐capture reaction rates of astrophysical interest in the energy range of the Gamow window for core‐collapse supernovae. Special interest comes from the long‐lived radio‐isotope 44Ti (t1/2 = 58.9 years), which is supposed to be produced in the alpha‐rich freeze‐out during such an event. The nucleosynthesis of this isotope is of great interest, as the amount of material produced can be estimated by direct observation in remnants of recent supernovae. The disagreements between the observations and the estimations from astrophysical models show the need of more experimental data for the production and consumption reactions in the energy range of a core‐collapse supernova. In this article, we will describe the proposed method of injecting beams of 44Ti into CRYRING@ESR and performing the actual reaction rate measurements.