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Using a partonic transport model we investigate the evolution of conical structures in ultrarelativistic matter. Using two different source terms and varying the transport properties of the matter we study the formation of Mach Cones. Furthermore, in an additional study we extract the two-particle correlations from the numerical calculations and compare them to an analytical approximation. The influence of the viscosity to the shape of Mach Cones and the corresponding two-particle correlations is studied by adjusting the cross section of the medium.
In the 1960s, theoretical concepts prepared the path to nuclear matter with proton and neutron numbers far beyond the nuclei known at that time. The new laboratory GSI was founded for research on reactions with heavy ions, in particular those for production of the predicted super-heavy nuclei. In this contribution it is presented how the interaction between experiment and theory resulted in a continuous improvement of the experimental set-ups on the one hand, and of the knowledge of the processes during the nuclear reaction and of the properties of the produced nuclei on the other hand. In the course of this work six new elements from 107 to 112 were produced and identified. An overview of the present status of experimental results and a comparison with theoretical interpretations is given.
We have studied one-proton-removal reactions of about 500MeV/u 17Ne beams on a carbon target at the R3B/LAND setup at GSI by detecting beam-like 15O-p and determining their relative-energy distribution. We exclusively selected the removal of a 17Ne halo proton, and the Glauber-model analysis of the 16F momentum distribution resulted in an s2 contribution in the 17Ne ground state of about 40%.
p-process nucleosynthesis via proton-capture reactions in thermonuclear supernovae explosions
(2015)
Model calculations within the framework of the so-called γ process show an underproduction of the p nucleus with the highest isotopic abundace 92Mo. This discrepancy can be narrowed by taking into account the alternative production site of a type Ia supernova explosion. Here, the nucleus 92Mo can be produced by a sequence of proton-capture reactions. The amount of 92Mo nuclei produced via this reaction chain is most sensitive to the reactions 90Zr(p,γ) and 91Nb(p,γ). Both rates have to be investigated experimentally to study the impact of this nucleosynthesis aspect on the long-standing 92Mo-problem. We have already measured the proton-capture reaction on 90Zr using high-resolution in-beam γ-ray spectroscopy. In this contribution, we will present our preliminary results of the total cross sections as well as the partial cross sections. Furthermore, we plan to measure the 91Nb(p,γ) reaction soon. Due to the radioactive target material, the 91Nb nuclei have to be produced prior to the experiment. The current status of this production will be presented in this contribution.
The Compressed Baryonic Matter (CBM) experiment [1] is a fixed target heavy-ion experiment that will operate at the international Facility for Antiproton and Ion Research (FAIR) [2] now under construction in Darmstadt, Germany. The experiment intends to study rare probes, which are emitted from heavy ion collisions with a beam energy of 4 to 45 AGeV. A focus is laid to the short lived open charm particles and to particles decaying into di-lepton pairs. Handling the up to 107 Au+Au collisions/s required for generating those probes with sufficient statistics, as much as reaching the required sensitivity for observing them, forms a major challenge for the silicon detectors of the experiment. We present the concept and the development status of two central detectors of CBM, the CMOS pixel based micro vertex detector (MVD) and the micro-strip detector based silicon tracking system (STS).
22nd International Workshop on Vertex Detectors, 15-20 September 2013 Lake Starnberg, Germany
XIII Nuclei in the Cosmos, 7-11 July, 2014 Debrecen, Hungary.
As an alternative production scenario to the so-called g process, the most abundant p nucleus 92Mo may be produced by a chain of proton-capture reactions in supernovae type Ia. The reactions 90Zr(p,g) and 91Nb(p,g) are the most important reactions in this chain. We have measured the first reaction using high-resolution in-beam g-spectroscopy at HORUS, Cologne, Germany, to contribute to the existing experimental data base. So far, we only investigated the high-energy part of the Gamow window and the analysis is still in progress. We plan to study the second reaction in standard kinematics at the FRANZ facility, Frankfurt, Germany. Current developments at FRANZ will be explained in detail.
We present the results of two-pion production in tagged quasi-free np collisions at a deutron incident beam energy of 1.25 GeV/c measured with the High-Acceptance Di-Electron Spectrometer (HADES) installed at GSI. The specific acceptance of HADES allowed for the first time to obtain high-precision data on π+π− and π−π0 production in np collisions in a region corresponding to large transverse momenta of the secondary particles. The obtained differential cross section data provide strong constraints on the production mechanisms and on the various baryon resonance contributions (∆∆, N(1440), N(1520), ∆(1600)). The invariant mass and angular distributions from the np → npπ+π −and np → ppπ−π0 reactions are compared with different theoretical model predictions.
We have measured the radiative neutron-capture cross section and the total neutron-induced cross section of one of the most important isotopes for the s process, the 25Mg. The measurements have been carried out at the neutron time-of-flight facilities n_TOF at CERN (Switzerland) and GELINA installed at the EC-JRC-IRMM (Belgium). The cross sections as a function of neutron energy have been measured up to approximately 300 keV, covering the energy region of interest to the s process. The data analysis is ongoing and preliminary results show the potential relevance for the s process.
We discuss recent applications of the partonic perturbative QCD based cascade model BAMPS with focus on heavy-ion phenomenology in the hard and soft momentum range. First, the elliptic flow and suppression of charm and bottom quarks are studied at LHC energies. Thereafter, we compare in a detailed study the standard Gunion-Bertsch approximation of the matrix elements for inelastic processes to the exact results in leading order perturbative QCD. Since a disagreement is found, we propose an improved Gunion-Bertsch matrix element, which agrees with the exact result in all phase space regions.
We investigate the properties of the QCD matter across the deconfinement phase transition. In the scope of the parton-hadron string dynamics (PHSD) transport approach, we study the strongly interacting matter in equilibrium as well as the out-of equilibrium dynamics of relativistic heavy-ion collisions. We present here in particular the results on the electromagnetic radiation, i.e. photon and dilepton production, in relativistic heavy-ion collisions and the relevant correlator in equilibrium, i.e. the electric conductivity. By comparing our calculations for the heavy-ion collisions to the available data, we determine the relative importance of the various production sources and address the possible origin of the observed strong elliptic flow ν2 of direct photons.
We present results for calculating fusion cross-sections using a new microscopic approach based on a time-dependent density-constrained DFT calculations. The theory is implemented by using densities and other information obtained from TDDFT time-evolution of the nuclear system as a constraint on the density for DFT calculations.
There are only 3 methods for the production of heavy and superheavy (SH) nuclei, namely, fusion reactions, a sequence of neutron capture and beta(-) decay and multinucleon transfer reactions. Low values of the fusion cross sections and very short half-lives of nuclei with Z<120 put obstacles in synthesis of new elements. At the same time, an important area of SH isotopes located between those produced in the cold and hot fusion reactions remains unstudied yet. This gap could be filled in fusion reactions of 48Ca with available lighter isotopes of Pu, Am, and Cm. New neutron-enriched isotopes of SH elements may be produced with the use of a 48Ca beam if a 250Cm target would be prepared. In this case we get a real chance to reach the island of stability owing to a possible beta(+) decay of 291114 and 287112 nuclei formed in this reaction with a cross section of about 0.8 pb. A macroscopic amount of the long-living SH nuclei located at the island of stability may be produced by using the pulsed nuclear reactors of the next generation only if the neutron fluence per pulse will be increased by about three orders of magnitude. Multinucleon transfer processes look quite promising for the production and study of neutron-rich heavy nuclei located in upper part of the nuclear map not reachable by other reaction mechanisms. Reactions with actinide beams and targets are of special interest for synthesis of new neutron-enriched transfermium nuclei and not-yet-known nuclei with closed neutron shell N=126 having the largest impact on the astrophysical r-process. The estimated cross sections for the production of these nuclei allows one to plan such experiments at currently available accelerators.
The HITRAP linear decelerator currently being set up at GSI will provide slow, few keV/u highly charged ions for atomic physics experiments. The expected beam intensity is up to 105 ions per shot. To optimize phase and amplitude of the RF systems intensity, bunch length and kinetic energy of the particles need to be monitored. The bunch length that we need to fit is about 2 ns, which is typically measured by capacitive pickups. However, they do not work for the low beam intensities that we face. We investigated the bunch length with a fast CVD diamond detector working in single particle counting mode. Averaging over 8 shots yields a clear, regular picture of the bunched beam. Energy measurements by capacitive pickups are limited by the presence of intense primary and partially decelerated beam and hence make tuning of the IH-structure impossible. The energy of the decelerated fraction of the beam behind the first deceleration cavity was determined to about 10 % accuracy with a permanent dipole magnet combined with a MCP. Better detector calibration should help reaching the required 1%. Design of the detectors as well as the results of the measurements will be presented.
A test stand for optical beam tomography was developed. As a new non-destructive beam-diagnostic system for high current ion beams, the test stand will be installed in the low energy beam transport section (LEBT) of the Frankfurt Neutron Source (FRANZ) behind the chopper system. The test stand consists of a rotatable vacuum chamber with a mounted CCD camera. The maximum rotation angle amounts to 270°. In a first phase the optical beam profile measurement and 3D density reconstruction is tested with a time independent 10 keV He beam. The measurements and performance of data processing algorithms are compared with the beam transport simulations. In a later phase the performance with time dependent beams (120 keV, 200 mA) at a repetition rate of 250 kHz and a duty cycle of 2.5% has to be evaluated. An overview of the first phase results is shown.
Space charge lenses use a confined electron cloud for the focusing of ion beams. The focusing strength is given by the electron density whereas the density distribution influences the mapping quality of the space charge lens and is related to the confinement. The plasma parameters, loss as well as production mechanisms have a strong impact on plasma beam interactions. A scaled up space charge lens was constructed to investigate the properties of a nonneutral plasmas in detail. New non-interceptive diagnostic has been developed to characterize the collective behaviour of the confined nonneutral plasma in terms of an optimized lens design and parameters. Experimental results will be presented in comparison with numerical simulations.
A non-interceptive optical diagnostic system on the basis of beam tomography, was developed for the planned Frankfurt Neutron Source (FRANZ). The proton driver linac of FRANZ will provide energies up to 2.0 MeV. The measurement device will non-interceptively derive required beam parameters at the end of the LEBT at beam energies of 120 keV and a current of 200 mA. On a narrow space of 351.2 mm length a rotatable tomography tank will perform a multi-turn tomography with a high and stable vacuum pressure. The tank allows to plug different measurement equipment additionally to the CCD Camera installed, to perform optical beam tomography. A collection of developed algorithms provides information about the density distribution, shape, size, location and emittance on the basis of CCD images. Simulated, as well as measured data have been applied to the evaluation algorithms to test the reliability of the beam. The actual contribution gives an overview on the current diagnostic possibilities of this diagnostic system.
Intense ion beams with small phase space occupation (high brilliance) are mandatory to keep beam losses low in high current injector accelerators like those planned for FAIR. The low energy beam transport from the ion source towards the linac has to keep the emittance growth low and has to support the optimization of the ion source tune. The Frankfurt Neutron Source Facility FRANZ is currently under construction. An intense beam of protons (2 MeV, 200 mA) will be used for neutron production using the Li7(p,n)Be7 reaction for studies of the astrophysical s-process. A collimation channel, which can be adjusted to allow the transport of beams with a certain beam emittance, is an ideal tool to optimize the ion source tune in terms of beam brightness. Therefore a collimation channel in the Low Energy Beam Transport section will be used. Through defined apertures and transversal phase space rotation using focusing solenoids the beam halo as well as unwanted H2+ and H3+ fractions will be cut. Theoretical studies which were carried out so far and a first design of the setup will be presented.
Beam test of the direct plasma injection scheme (DPIS) is carried out successfully for the first time in China, by setting up a comprehensive test and research platform of RFQ and laser ion source. The C6+ beam is accelerated successfully, and the peak beam current reaches more than 6mA which is measured by a Faraday cup of unique structure. The RF power coupled into the RFQ cavity is also examined, and results reveal that it is the RF power of about 195kW that can produce the peak beam current.
A CW RFQ prototype
(2011)
A short RFQ prototype was built for RF-tests of high power RFQ structures. We will study thermal effects and determine critical points of the design. HF-simulations with CST Microwave Studio and measurements were done. The cw-tests with 20 kW/m RF-power and simulations of thermal effects with ALGOR were finished successfully. The optimization of some details of the HF design is on focus now. First results and the status of the project will be presented.
Beam measurements with the new RFQ beam matching section at the Frankfurt Funneling Experiment
(2011)
Funneling is a method to increase low energy beam currents in multiple stages. The Frankfurt Funneling Experiment is a model of such a stage. The experiment is built up of two ion sources with electrostatic lens systems, a Two-Beam-RFQ accelerator, a funneling deflector and a beam diagnostic system. The two beams are bunched and accelerated in a Two-Beam RFQ. A funneling deflector combines the bunches to a common beam axis. A new beam transport system between RFQ accelerator and deflector has been constructed and mounted. With these extended RFQ-electrodes the drift between the Two-Beam-RFQ and the rf-deflector will be minimized and therefore unwanted emittance growth reduced. After first rf measurements current work are beam tests with the improved Two-Beam-RFQ. First results will be presented.
Usually 4-ROD Radio Frequency Quadrupoles (RFQ) are built for frequencies up to 216 MHz. For higher frequencies 4-VANE structures are more common. The advantages of 4-Rod structures, the greater flexibility for tuning and being more comfortable for maintenance, are motivating the development of a 4-Rod RFQ for higher frequencies than 216 MHz. In particular a 325 MHz RFQ with an output energy of 3 MeV is needed for the proton linac for the FAIR project of GSI. This paper reports about the design studies and the latest developments of this RFQ.
For the injector upgrade at FNAL a 4-rod Radio Frequency Quadrupole (RFQ) with a resonance frequency of 200 MHz has been build. With this short structure of only 1.3 m a very compact injector design has been realized. Simulations with CST Microwave Studio® were performed for the design. Their results leading to the RF characterizations of the RFQ and the final RF setup which has been accomplished at IAP of the Goethe-University Frankfurt are presented in this paper.
The LANSCE linear accelerator at Los Alamos National Laboratory provides H− and H+ beams to several user facilities that support Isotope Production, NNSA Stockpile Stewardship, and Basic Energy Science programs. These beams are initially accelerated to 750 keV using Cockcroft-Walton (CW) based injectors that have been in operation for over 37 years. They have failure modes which can result in prolonged operational downtime due to the unavailability of replacement parts. To reduce long-term operational risks and to realize future beam performance goals in support of the Materials Test Station (MTS) and the Matter-Radiation Interactions in Extremes (MaRIE) Facility, plans are underway to develop a Radio-Frequency Quadrupole (RFQ) based front end as a modern injector replacement for the existing CW injectors. Our progress to date will be discussed.
n order to reach the desired intensities of heavy ion beams for the experiments at FAIR, SIS18 and SIS100 have to be operated with intermediate charge states. Operation with intermediate charge state heavy ions at the intensity level of about 1011 ions per cycle has never been demonstrated elsewhere and requires a dedicated upgrade program for SIS18 and a dedicated machine design for SIS100. The specific problems coming along with the intermediate charge state operation in terms of charge exchange processes at collisions with residual gas atoms, pressure bumps by ion induced desorption and corresponding beam loss appears far below the typical space charge limits. Thus, new design concepts and new technical equipment addressing these issues are developed and realized with highest priority. The upgrade program of SIS18 addressing the goal of minimum ionization beam loss and stable residual gas pressure conditions has been defined in 2005. A major part of this upgrade program has been successfully realized, with the result of a world record in accelerated number of intermediate charge state heavy ions.
Accelerator Driven Systems (ADS) are promising tools for the efficient transmutation of nuclear waste products in dedicated industrial installations, called transmuters. The Myrrha project at Mol, Belgium, placed itself on the path towards these applications with a multipurpose and versatile system based on a liquid PbBi (LBE) cooled fast reactor (80 MWth) which may be operated in both critical and subcritical modes. In the latter case the core is fed by spallation neutrons obtained from a 600 MeV proton beam hitting the LBE coolant/target. The accelerator providing this beam is a high intensity CW superconducting linac which is laid out for the highest achievable reliability. The combination of a parallel redundant and of a fault tolerant scheme should allow obtaining an MTBF value in excess of 250 hours that is required for optimal integrity and successful operation of the ADS. Myrrha is expected to be operational in 2023. The forthcoming 4-year period is fully dedicated to R&D activities, and in the field of the accelerator they are strongly focused on the reliability aspects and on the proper shaping of the beam trip spectrum.
Development of fragmented low-Z ion beams for the NA61 fixed-target experiment at the CERN SPS
(2011)
The NA61 experiment, aims to study the properties of the onset of deconfinement at low SPS energies and to find signatures of the critical point of strongly interacting matter. A broad range in T-μB phase diagram will be covered by performing an energy (13A-158A GeV/c) and system size (p+p, Be+Be, Ar+Ca, Xe+La) scan. In a first phase, fragmented ion beams of 7Be or 11C produced as secondaries with the same momentum per nucleon when the incident primary Pb-ion beam hits a thin Be target will be used. The H2 beam line that transports the beam to the experiment acts as a double spectrometer which combined with a new thin target (degrader) where fragments loose energy proportional to the square of their charge allows the separation of the wanted A/Z fragments. Thin scintillators and TOF measurement for the low energy points are used as particle identification devices. In this paper results from the first test of the fragmented ion beam done in 2010 will be presented showing that a pure Be beam can be obtained satisfying the needs of the experiment.
Space charge lenses using a stable electron cloud for focusing low energy heavy ion beams are an alternative concept to conventional ion optics. Due to external fields electrons are confined inside the lens’ volume. In case of a homogeneously distributed electron cloud the linear electric space charge field enables beam focusing free of aberration. Since the mapping quality of the lens is related to the confinement, non-destructive diagnostics has been developed to determine the plasma parameters and to characterize the collective behavior of the confined nonneutral plasma. Moreover, a scaled up space charge lens was constructed for a detailed investigation of the nonneutral plasma properties as well as beam interactions with a stable confined electron cloud. Experimental results will be presented in comparison with numerical simulations.
As the successor of the EUROTRANS project, the MAX project is aiming to continue the R&D effects for a European Accelerator-Driven System and to bring the conceptual design to reality. The layout of the driver linac for MAX will follow the reference design made for the XT-ADS phase of the EUROTRANS project. For the injector part, new design strategies and approaches, e.g. half resonant frequency, half transition-energy between the RFQ and the CH-DTL, and using the 4-rod RFQ structure instead of the originally proposed 4-vane RFQ, have been conceived and studied to reach a more reliable CW operation at reduced costs. In this paper, the design and simulation results of the MAX injector are presented.
MYRRHA is conceived as an accelerator driven system (ADS) for transmutation of high level nuclear waste. The neutron source is created by coupling a proton accelerator of 600 MeV with a 4 mA proton beam, a spallation source and a sub-critical core. The IAP of Frankfurt University is responsible for the development of the 17 MeV injector operated at 176 MHz. The injector consists of a 1.5 MeV 4-Rod-RFQ and six CH-drifttube-structures. The first two CH-structures will be operated at room temperature and the other CH-structures are superconducting cavities assembled in one cryo-module. To achieve the extremely high reliability required by the ADS application, the design of the 17 MeV injector has been intensively studied, with respect to thermal issues, minimum peak fields and field distribution.
Chromatic, geometric and space charge effects on laser accelerated protons focused by a solenoid
(2011)
We studied numerically emittance and transmission effects by chromatic and geometric aberrations, with and without space charge, for a proton beam behind a solenoid in the laser proton experiment LIGHT at GSI. The TraceWin code was employed using a field map for the solenoid and an initial distribution with exponential energy dependence close to the experiment. The results show a strong effect of chromatic, and a relatively weak one of geometric aberrations as well as dependence of proton transmission on distance from the solenoid. The chromatic effect has an energy filtering property due to the finite radius beam pipe. Furthermore, a relatively modest dependence of transmission on space charge is found for p production intensity below 1011.
Experimental results and theoretical predictions in laser acceleration of protons achieved energies of ten to several tens of MeV. The LIGHT project (Laser Ion Generation, Handling and Transport) is proposed to use the PHELIX laser accelerated protons and to provide transport, focusing and injection into a conventional accelerator. This study demonstrates transport and focusing of laser-accelerated 10 MeV protons by a pulsed 18 T magnetic solenoid. The effect of co-moving electrons on the beam dynamics is investigated. The unique features of the proton distribution like small emittances and high yield of the order of 1013 protons per shot open new research area. The possibility of creating laser based injectors for ion accelerators is addressed. With respect to transit energies, direct matching into DTL's seems adequate. The bunch injection into a proposed CH− structure is under investigation at IAP Frankfurt. Options and simulation tools are presented.
An optimized design of a stellarator-type storage ring for low energy ion beams was numerically investigated. The magnetic field variation along the circumference and therefore magnetic heating is suppressed by using simple circular correction coils. Particle-in-Cell (PIC) simulations in a magnetic flux coordinate system show the ability of high current ion beam accumulation in such a configuration with unique features for clockwise and anticlockwise moving beams. Additionally scaled down experiments with two 30 degree room temperature toroidal segments were performed to demonstrate toroidal transport and to develop optical beam diagnostics. Properties of multi-component beams, redistribution of transversal momenta in the non-adiabatic part of the experimental configuration and investigation of strongly confined beam induced electron clouds will be addressed.
For the research program with cooled antiprotons at FAIR a dedicated 70 MeV, 70 mA proton injector is required. The main acceleration of this room temperature linac will be provided by six CH cavities operated at 325 MHz. Each cavity will be powered by a 2.5 MW Klystron. For the second acceleration unit from 11.5 MeV to 24.2 MeV a 1:2 scaled model has been built. Low level RF measurements have been performed to determine the main parameters and to prove the concept of coupled CH cavities. For this second tank technical and mechanical investigations have been performed in 2010 to develop a complete technical concept for the manufacturing. In Spring 2011, the construction of the first power prototype has started. The main components of this cavity will be ready for measurements in summer 2011. At that time, the cavity will be tested with a preliminary aluminum drift tube structure, which will allow precise frequency and field tuning. This paper will report on the recent technical development and achievements. It will outline the main fabrication steps towards that novel type of proton DTL. Also first low level RF measurements are expected.
The MYRRHA Project (Multi Purpose Hybrid Reactor for High Tech Applications) at Mol/belgium will be a user facility with emphasis on research with neutron generated by a spallation source. One main aspect is the demonstration of nuclear waste technology using an accelerator driven system. A superconducting linac delivers a 4 mA, 600 MeV proton beam. The first accelerating section is covered by the 17 MeV injector. It consists of a proton source, an RFQ, two room temperature CH cavities and 4 superconducting CH-cavities. The initial design has used an RF frequency of 352 MHz. Recently the frequency of the injector has been set to 176 MHz. The main reason is the possible use of a 4-rod-RFQ with reduced power dissipation and energy, respectively. The status of the overall injector layout including cavity design is presented.
SIS100 is the main synchrotron of the FAIR project. It is designed to accelerate high intensity intermediate charge state uranium beams from 200 MeV/u up to 2.7 GeV/u. Intermediate charge state heavy ions are exposed to a high probability of charge exchange due to collisions with residual gas molecules. Since the charge exchange process changes the magnetic rigidity, the involved ions are lost behind dispersive elements, and an energy-dependent gas desorption takes place. The StrahlSim code has been used to predict the stability of the residual gas pressure in SIS100 under beam loss driven dynamic conditions. The results show, that a stable operation at highest U28+ intensities is possible, under the constraint that the vacuum chambers of the ion catcher system are cold enough to pump hydrogen. Furthermore, in order to determine the load to the cryogenic system, the average beam energy deposition onto the ion catcher system has been calculated.
The ARMADILLO bunch compressor currently being designed at IAP is capable of reaching a longitudinal pulse compression ratio of 45 for proton beams of 150 mA at 2 MeV. It will provide one nanosecond proton pulses with a peak current of 7.7 A. The system guides nine linacμbunches deflected by a 5 MHz rf kicker and uses four dipole magnets - two homogeneous and two with field gradients - to merge them on the target. For longitudinal focusing and an energy variation of ±200 keV two multitrack rf cavities are included. ARMADILLO will be installed at the end of the Frankfurt Neutron Source FRANZ making use of the unique 250 kHz time structure. This contribution will provide an overview of the layout of the system as well as recent advances in component design and beam dynamics of the compressor.
At the Institute for Applied Physics (IAP), University of Frankfurt, a s.c. 325 MHz CH-Cavity is under development for future beam tests at GSI UNILAC, Darmstadt. The cavity with 7 accelerating cells has a geometrical beta of 0.15 corresponding to 11.4 AMeV. The design gradient is 5 MV/m. The geometry of this resonator was optimized with respect to a compact design, low peak fields, surface processing, power coupling and tuning. Furthermore a new tuning system based on bellow tuners inside the resonator will control the frequency during operation. After rf tests in Frankfurt the cavity will be tested with a 10 mA, 11.4 AMeV beam delivered by the GSI UNILAC. In this paper rf simulations, multipacting analysis as well as thermal calculations will be presented.
The SIS300 synchrotron, planned for the new Facility for Antiproton and Ion Research (FAIR) at GSI-Darmstadt, will become the first superconducting synchrotron worldwide using cos(θ) magnets for resonant slow extraction. A multi-objective optimization algorithm has been developed for the design of the non-linear magnet scheme. The optimization algorithm makes use of the analytical model for the slow extraction from Kobayashi, the analytical description of the resonance excitation and amplitude-dependent tune-shift from Bengtsson, and corrects the chromaticity in order to fulfill the Hardt condition. As a result, the placement of the chromatic and harmonic sextupole magnets in SIS300, the number of sextupole families and the gradients of these families have been optimized for a high efficiency slow extraction. The algorithm accounts also for the sextupole errors on the dipole magnets, compensating its effects. Furthermore, optimized time-dependent settings for the sextupole magnets are generated to compensate the persistent current decay occurring at slow extraction. Tolerances for the magnets are set for the limits where the compensation is no longer valid.
Chopper systems are used to pulse charged particle beams. In most cases, electric deflection systems are used to generate beam pulses of defined lengths and appropriate repetition rates. At high beam intensities, the field distribution of the chopper system needs to be adapted precisely to the beam dynamics in order to avoid aberrations. An additional challenge is a robust design which guarantees reliable operation. For the Frankfurt Neutron Source FRANZ, an E×B chopper system is being developed which combines static magnetic deflection with a pulsed electric field in a Wien filter configuration. It will generate proton pulses with a flat top of 50 ns at a repetition rate of 250 kHz for 120 keV, 200 mA beams. For the electric deflection, pre-experiments with static and pulsed fields were performed using a helium ion beam. In pulsed mode operation, ion beams of different energies were deflected with voltages of up to ±6 kV and the resulting response was measured using a beam current transformer. A comparison between experiments and theoretical calculations as well as numerical simulations are presented.
A modern linear accelerator of ions is a long chain of different accelerating-focusing structures. The design of new linacs, as well as an upgrade and optimization of operating facilities, requires precise and reliable beam matching with the subsequent sections. Proper matching of the beam to the channel allows to improve the performance of the whole linac and to reduce the specific costs. Additionally it helps to avoide particle loss in high energy high intensity linacs. Generally a matching algorithm combines precisely measured or calculated accelerating-focusing external fields and experimentally obtained details of the beam parameters with an advanced code for beam dynamics simulations including space charge effects. Experimental results are introduced into a code as input data. The described algorithm has already been successfully implemented for several GSI projects: an upgrade of the GSI heavy ion linac UNILAC, an ion linac for the cancer therapy, the proton linac for the FAIR facility, a facility for laser acceleration of ions and others. Measured data and results of beam dynamics simulations leading to an achieved improvement of the linac performance are presented.
At GSI a new, superconducting (sc) continuous wave (cw) LINAC is under design in cooperation with the Institute for Applied Physics (IAP) of Frankfurt University and the Helmholtz Institut Mainz (HIM). This proposed LINAC is highly requested by a broad community of future users to fulfill the requirements of nuclear chemistry, nuclear physics, and especially in the research field of Super Heavy Elements (SHE). In this context the preliminary layout of the LINAC has been carried out by IAP. The main acceleration of up to 7.3 AMeV will be provided by nine sc Crossbar-H-mode (CH) cavities operated at 217 MHz. Currently, a prototype of the cw LINAC as a demonstrator is under development. The demonstrator comprises a sc CH-cavity embedded between two sc solenoids mounted in a horizontal cryomodule. A full performance test of the demonstrator in 2013/14 by injecting and accelerating a beam from the GSI High Charge Injector (HLI) is one important milestone of the project. The status of the demonstrator is presented.
The superconducting CH-structure (Crossbar-H-mode) is a multi-cell drift tube cavity for the low and medium energy range operated in the H21-mode, which has been developed at the Institute for Applied Physics (IAP) of Frankfurt University. With respect to different high power applications two types of superconducting CH-structures (f = 325 MHz, β = 0.16, seven cells and f = 217 MHz, β = 0.059, 15 cells) are presently under construction and accordingly under development. The structural mechanical simulation is a very important aspect of the cavity design. Furthermore, several simulations with ANSYS Workbench have been performed to predict the deformation of the cavity walls due to the cavity cool-down, pressure effects and mechanical vibrations. To readjust the fast frequency changes in consequence of the cavity shape deformation, a new concept for the dynamic frequency tuning has been investigated, including a novel type of bellow-tuner.
The Frankfurt Neutron Source at the Stern-Gerlach-Zentrum is driven by a 2 MeV proton linac consisting of a 4-rod-radio-frequency-quadrupol (RFQ) and an 8 gap IH-DTL structure. RFQ and IH cavity will be powered by only one radio frequency (RF) amplifier to reduce costs. The RF-amplifier of the RFQ-IH combination is coupled into the RFQ. Internal inductive coupling along the axis connects the RFQ with the IH cavity ensuring the required power transition as well as a fixed phase relation between the two structures. The main acceleration of 120 keV up to 2.03 MeV will be reached by the RFQ-IH combination with 175 MHz and at a total length of 2.3 m. The losses in the RFQ-IH combination are about 200 kW.
We report on the event-by-event multiplicity fluctuations of identified particles in central Pb+Pb collisions measured by the NA49 experiment at the CERN SPS. Employing a novel approach we unfolded the moments of the unknown multiplicity distributions of protons (p), kaons (K), pions (π) and electrons. Using these moments we reconstructed an excitation function of the fluctuation measure νdyn[A;B], with A and B denoting different particle types. Specifically, we reconstructed νdyn for the [p, π], [p, K] and [K, π] pairs. The energy dependence of νdyn is in agreement with previously published NA49 results on the related measure σdyn. Moreover, for [K; p] and [K;p] pairs, we discovered a dependence of the fluctuation measure νdyn on the phase space coverage (acceptance). Interestingly for the [p,π] case no significant acceptance dependence was observed. These observations provide a likely explanation of the reported differences between measurements of NA49 and those of STAR in central Au+Au collisions.
The study of energy and system size dependence of fluctuations of identified hadrons is one of the key goals of NA61/SHINE at the CERN SPS. Results may allow to discover the critical point (CP) of strongly interacting matter as well as to uncover properties of the onset of deconfinement (OD). Measured fluctuations are affected by numerous other effects like volume fluctuations and conservation laws. NA49 seems to observe fluctuations possibly related to the CP in collisions of medium size nuclei at the top SPS energy. However, this result will remain inconclusive until systematic data on energy and system size dependence will be available. Moreover, fluctuations in p+p as well as in Pb+Pb interactions should be better understood. In this contribution new results on multiplicity fluctuations of identified hadrons in p+p interactions at the CERN SPS energies will be presented. The NA61 data will be compared with the corresponding results on central Pb+Pb collisions of NA49 in the common acceptance region of both experiments. Furthermore, predictions of models (EPOS, UrQMD and HSD) for p+p interactions will be tested.
While the existence of a strongly interacting state of matter, known as “quark-gluon plasma” (QGP), has been established in heavy ion collision experiments in the past decade, the task remains to map out the transition from the hadronic matter to the QGP. This is done by measuring the dependence of key observables (such as particle suppression and elliptic flow) on the collision energy of the heavy ions. This procedure, known as "beam energy scan", has been most recently performed at the Relativistic Heavy Ion Collider (RHIC).
Utilizing a Boltzmann+hydrodynamics hybrid model, we study the collision energy dependence of initial state eccentricities and the final state elliptic and triangular flow. This approach is well suited to investigate the relative importance of hydrodynamics and hadron transport at different collision energies.