IPAC2011 - List of Authors (Ratzinger, U.)

Paper

Title

Page

A Coupled RFQ-IH Combination for the Neutron Source FRANZ

74

M. Heilmann, O. Meusel, D. Mäder, U. Ratzinger, A. Schempp
IAP, Frankfurt am Main, Germany

Funding: HIC for FAIR
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.

MOPC082

Status of the 325 MHz SC CH-Cavity at IAP Frankfurt

265

M. Busch, F.D. Dziuba, H. Podlech, U. Ratzinger
IAP, Frankfurt am Main, Germany
M. Amberg, K. Aulenbacher
HIM, Mainz, Germany
W.A. Barth, S. Mickat
GSI, Darmstadt, Germany

Funding: BMBF contract no. 06FY161I
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.

MOPC083

Structural Mechanics of Superconducting CH Cavities

268

M. Amberg, K. Aulenbacher
HIM, Mainz, Germany
W.A. Barth, S. Mickat
GSI, Darmstadt, Germany
M. Busch, F.D. Dziuba, H. Podlech, U. Ratzinger
IAP, Frankfurt am Main, Germany

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.

MOPC084

The Superconducting cw LINAC Demonstrator for GSI

271

F.D. Dziuba, M. Busch, H. Podlech, U. Ratzinger
IAP, Frankfurt am Main, Germany
M. Amberg, K. Aulenbacher
HIM, Mainz, Germany
W.A. Barth, S. Mickat
GSI, Darmstadt, Germany

Funding: BMBF Contr. No. 06FY9089I, Helmholtz Institut Mainz
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.

MOPS028

An Ion Beam Matching to a Linac Accelerating-focusing Channel

661

A. Orzhekhovskaya, W.A. Barth, G. Clemente, L.A. Dahl, P. Gerhard, L. Groening, M. Kaiser, M.T. Maier, S. Mickat, B. Schlitt, H. Vormann, S.G. Yaramyshev
GSI, Darmstadt, Germany
U. Ratzinger
IAP, Frankfurt am Main, Germany

Funding: Work supported by HIC for FAIR
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.

MOPS029

Experiments with a Fast Chopper System for Intense Ion Beams

664

H. Dinter, M. Droba, M. Lotz, O. Meusel, I. Müller, D. Noll, U. Ratzinger, K. Schulte, C. Wagner, C. Wiesner
IAP, Frankfurt am Main, Germany

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.

MOPS030

Beam Dynamics of the FRANZ Bunch Compressor using Realistic Fields with a Focus on the Rebuncher Cavities

667

D. Noll, L.P. Chau, M. Droba, O. Meusel, H. Podlech, U. Ratzinger, C. Wiesner
IAP, Frankfurt am Main, Germany

Funding: Work supported by HIC for FAIR.
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.

WEPC059

Optimization of the Sextupole Scheme and Compensation of the Time-Dependent Field Errors during Slow Extraction from the Superconducting Synchrotron SIS300

2151

A. Saa Hernandez, P.J. Spiller
GSI, Darmstadt, Germany
U. Ratzinger
IAP, Frankfurt am Main, Germany

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.

WEPS004

Confinement, Accumulation and Diagnostic of Low Energy Ion Beams in Toroidal Fields

2487

M. Droba, A. Ates, O. Meusel, H. Niebuhr, U. Ratzinger, J.F. Wagner
IAP, Frankfurt am Main, Germany

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.

WEPS033

Matching a Laser Driven Proton Injector to a CH - Drift Tube Linacs

2556

A. Almomani, M. Droba, U. Ratzinger
IAP, Frankfurt am Main, Germany
I. Hofmann
HIJ, Jena, Germany

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.

WEPS036

First Coupled CH Power Cavity for the FAIR Proton Injector

2565

R. M. Brodhage, C. Fix, H. Podlech, U. Ratzinger
IAP, Frankfurt am Main, Germany
G. Clemente, L. Groening
GSI, Darmstadt, Germany

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.

WEPS038

Development of CH-Cavities for the 17 MeV MYRRHA-Injector

2571

D. Mäder, H. Klein, H. Podlech, U. Ratzinger, M. Vossberg, C. Zhang
IAP, Frankfurt am Main, Germany

Funding: European Union FP7 MAX Contract Number 269565
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.

WEPS039

General Layout of the 17 MeV Injector for MYRRHA

2574

H. Podlech, M. Busch, F.D. Dziuba, H. Klein, D. Mäder, U. Ratzinger, A. Schempp, R. Tiede, C. Zhang
IAP, Frankfurt am Main, Germany
M. Amberg
HIM, Mainz, Germany

Funding: European Union FP7 MAX Contract Number 269565
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.

Poster WEPS039 [2.281 MB]

WEPS040

The Driver Linac of the Neutron Source FRANZ

2577

U. Ratzinger, B. Basten, L.P. Chau, H. Dinter, M. Droba, M. Heilmann, M. Lotz, O. Meusel, I. Müller, D. Mäder, Y.C. Nie, D. Noll, H. Podlech, A. Schempp, W. Schweizer, K. Volk, C. Wiesner, C. Zhang
IAP, Frankfurt am Main, Germany

FRANZ is under construction at the Goethe University Frankfurt. A 2MeV ± 100 keV proton beam will produce 1 keV to 200 keV neutrons on a Li7 target. Experiments are planned in the field of nuclear astrophysics as well as in applied physics. A dc operated proton source with a maximum beam current of 200 mA was successfully beam tested end of 2010. FRANZ will have two experimental areas: One for activation experiments with cw proton beams of a few mA generating a usable neutron flux of some 10 billion per square cm per second, the other one for 250 kHz, 1 ns short neutron bunches generated by 1 ns proton pulses of a few Ampere beam current. A special 2 MeV, 175 MHz high current cavity is realized at present as a RFQ-DTL combination. Novel techniques have been invented to reach the needed pulsed target beam current by a bunch compressor system.
Work supported by HICforFAIR and GSI.

WEPS043

From EUROTRANS to MAX: New Strategies and Approaches for the Injector Development

2583

C. Zhang, H. Klein, D. Mäder, H. Podlech, U. Ratzinger, A. Schempp, R. Tiede
IAP, Frankfurt am Main, Germany

Funding: The research leading to these results has received funding from the European Atomic Energy Community’s (Euratom) Seventh Framework Programme FP7/2007-2011 under grant agreement n° [269565].
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.

WEPS094

Dynamic Vacuum Stability in SIS100

2724

P. Puppel, U. Ratzinger
IAP, Frankfurt am Main, Germany
P.J. Spiller
GSI, Darmstadt, Germany

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.

WEPZ002

Chromatic, Geometric and Space Charge Effects on Laser Accelerated Protons Focused by a Solenoid

2766

H.Y. Al-Omari, U. Ratzinger
IAP, Frankfurt am Main, Germany
I. Hofmann
GSI, Darmstadt, Germany

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.

THPS034

Studies on Electron Cloud Dynamics for an Optimized Space Charge Lens Design

3493

K. Schulte, M. Droba, B. Glaeser, S. Klaproth, O. Meusel, U. Ratzinger
IAP, Frankfurt am Main, Germany

Funding: Work supported by HIC for FAIR.
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.