GSI, Darmstadt
Funding: EU-Research Infrastructure Activity under the FP6 "Structuring the European Research Area" program (CARE, contract number RII3-CT-2003-506395); EU-INTAS Project Ref. no. 06-1000012-8782
The present GSI accelerator chain will serve as an injector for FAIR. The linear accelerator UNILAC and the heavy ion synchrotron SIS18 should deliver up to 1012 U28+ particles/sec. In the past two years different hardware measures and a careful fine tuning of the UNILAC resulted in a 35% increase of the beam intensity to a new record of 1.25*1011 U27+ ions per 100μs or 2.3*1010 U73+ ions per 100μs. The increased stripper gas density, the optimization of the Alvarez-matching, the use of various newly developed beam diagnostics devices and a new charge state separator system in the foil stripper section comprised the successful development program. The contribution reports results of beam measurements during the high current operation with uranium beams (pulse beam power up to 0.65 MW). The UNILAC upgrade for FAIR will be continued by assembling a new front-end for U4+, stronger power supplies for the Alvarez quadrupoles, and versatile high current beam diagnostics devices. Additionally, the offered primary proton beam intensities will be increased by a new proton linac, which should be commissioned in 2013.
GSI, Darmstadt
IAP, Frankfurt am Main
For injection into the ion trap facility HITRAP, the GSI accelerator complex has the unique possibility to provide beams of highly stripped ions and even bare nuclei up to Uranium at an energy of 4 MeV/u. The HITRAP facility consists of linear 108 MHz-structures of IH- and RFQ-type to decelerate the beams further down to 6 keV/u for capturing in a large penning trap for cooling purpose. The installation is completed except of the RFQ-tank. During commissioning periods in 2007 64Ni28+ and 20Ne10+ beam was used to investigate the beam optics from the experimental storage ring extraction to the HITRAP double-drift-buncher system. In 2008 the IH-structure decelerator and the downstream matching section was examined with 197Au79+ beam. Comprehensive beam diagnostics were installed: Faraday cups, tubular and short capacitive pick ups, SEM grids, YAG scintillation screens, a single shot pepperpot emittance meter, and a diamond detector for bunch shape measurements. Results of the extensive measurements are presented.
ITEP, Moscow
GSI, Darmstadt
Funding: Work supported by the European Community INTAS Project Ref. no. 06-1000012-8782.
For the operation of the GSI-accelerator chain as an injector for the future FAIR facility a considerable increase of the heavy ion beam intensity by a factor 3-5 at the end of the UNILAC is required. The bottleneck of the whole UNILAC, is the front-end system of the High Current Injector. It is shown that the transverse RFQ-acceptance can be significantly increased while the emittance growth can be reduced. Both goals are achieved with only a moderate change of the RFQ electrode geometry; the intervane voltage raised from 125 kV to 155 kV keeping the design limit of the maximum field at the electrode surface. The changed resonant frequency can be compensated with a relatively small correction of the carrying rings. The beam parameters in the final focusing elements of the LEBT were improved together with the input radial matcher design; the length of the gentle buncher section was considerably increased to provide slow and smooth bunching resulting in a reduce influence of space charge forces. DYNAMION-simulation with the modified electrode design resulted in an increase of U4+-beam current of up to 20 emA. It is planned to start the upgrade measure in spring 2009.
GSI, Darmstadt
A dedicated charge separator system is now installed in the transfer line to the GSI-synchrotron SIS18. In former times charge separation was performed with a single 11 degree dipole magnet after a 25 m beam transport section. This was not adequate to meet the requirements during high current operation for FAIR: it only allows for charge state separation of low intensity and low emittance beams. With the new compact charge separator system emittance blow up and unwanted beam losses for high intensity beam operation will be avoided. Additionally a new beam diagnostics test bench is integrated. With this the beam parameters (ion current, beam profile, beam position, transversal emittance, bunch structure and beam energy) for the injection into the SIS18 can be measured in parallel to the routine operation in the transfer line. Results of the commissioning with high intensity argon beams as well as with an uranium beam will be reported.
GSI, Darmstadt
HIT, Heidelberg
A clinical facility for cancer therapy using energetic proton and ion beams (C, He and O) has been installed at the Radiologische Universitätsklinik in Heidelberg, Germany. It consists of two ECR ion sources, a 7 MeV/u linac injector, and a 6.5 Tm synchrotron to accelerate the ions to energies of 430 MeV/u. The linac comprises a 400 keV/u RFQ and a 7 MeV/u IH-DTL operating at 216.8 MHz and has been commissioned successfully in 2006. Yet the overall achieved transmission through the injector linac did not exceed 30% due to a mismatch of the beam at the RFQ entrance. Thus a detailed upgrade programme has been started to exchange the RFQ with a new radial matcher design, to correct the alignment and to optimize beam transport to the IH-DTL. The aim is to achieve a sufficient linac transmission above 60%. The new design of the RFQ has been finished in 2007 and the RFQ is currently in production. A test bench comprising a full ion source and LEBT setup to commission the RFQ in 2008 is under construction at Danfysik in Danemark. The current status of this upgrade programme will be reported in this contribution.
GSI, Darmstadt
ORNL, Oak Ridge, Tennessee
CEA, Gif-sur-Yvette
Funding: CARE, contract number RII3-CT-2003-506395) European Community INTAS Project Ref. no. 06-1000012-8782
Transverse emittance growth along the Alvarez DTL section is a major concern with respect to the preservation of beam quality of high current beams at the GSI UNILAC. In order to define measures to reduce this growth appropriate tools to simulate the beam dynamics are indispensable. This paper is on benchmarking of three beam dynamics simulation codes, i.e. DYNAMION, PARMILA, and PARTRAN against systematic measurements of beam emittance growth for different machine settings. Experimental set-ups, data reduction, the preparation of the simulations, and the evaluation of the simulations will be described. It was found that the mean value of final horizontal and vertical rms-emittances can be reproduced well by the codes.
IAP, Frankfurt am Main
GSI, Darmstadt
Funding: Work supported by BMBF under contract 06FY160I.
The Heavy highly charged Ion TRAP (HITRAP) project at GSI is in the commissioning phase. Highly charged ions up to U92+ provided by the GSI accelerator facility will be decelerated and subsequently injected into a large Penning trap for cooling to the MeV/u energy level. A combination of an IH- and an RFQ-structure decelerates the ions from 4 MeV/u down to 6 keV/u. In front of the decelerator a double drift-buncher-system is provided for phase focusing and a final de-buncher integrated in the RFQ-tank reduces the energy spread in order to improve the efficiency for beam capture in the cooler trap*. This contribution concentrates on the beam dynamics simulations and corresponding measurements in the commissioning beam times up to the position of the entrance to the RFQ. Single-shot emittance measurements at higher energies using the GSI pepper pot device and construction of a new device using Micro-Channel Plate technology for low energies as well as profile measurements are presented.
*HITRAP webpage of AP division at GSI, http://www.gsi.de/forschung/ap/projects/hitrap/index_e.html
GSI, Darmstadt
During the LINAC conference in Knoxville 2006 the operating frequency of the FAIR proton linac was fixed at 325.224 MHz. Even though the six CH-Structures need slightly different rf levels, the proton linac will be equipped with identical rf power sources. That applies although for the RFQ structure. To supply the FAIR accelerators with a good beam quality by the UNILAC as the high current heavy ion injector for FAIR, as well as an high duty factor accelerator for nuclear physics experiments, different upgrades and modifications have to be made at the rf components. In addition there has to be an upgrade for a planned 50% duty cycle mode, higher beam load within the post-stripper section as well as the provision of an excellent rf operation for the next 30 years. Discussions on possible collaborations with CERN in terms of LLRF and the combining of the procurement for tube amplifiers for bunching cavities are on the way. This paper describes the actual status of the proton linac rf system and the future requirements for the existing UNILAC rf systems.