The first cavity of a standalone superconducting (sc) continuous wave (cw) heavy ion Linac as a demonstration of the capability of 217 MHz multi gap Crossbar H-mode structures (CH) has been already commissioned at high acceleration gain. The worldwide first beam test with a superconducting multi gap CH-cavity was a milestone of the R&D work of HIM and GSI in collaboration with Goethe University Frankfurt (GUF) in preparation of the sc cw heavy ion Linac project, substituting GSI-UNILAC as a heavy ion high duty factor Linac. Recently the first two of four fully equipped cw-Linac cryomodules are in procurement. To meet the future FAIR science requirements higher beam intensity has to be achieved in the present GSI-accelerator complex. In the last years ion source developments, in particular for the high current Vacuum Arc Ion Sources (VARIS), were concentrated on heavy elements, as Bi and Pb, aiming for stable routine ion source operation at a sufficient rep. rate and high production efficiency. Stripping is a key technology for all heavy ion accelerators. After upgrade of the supersonic N 2 -gas jet implementation of high current foil stripping, recently a new H 2 gas cell, using a pulsed gas regime synchronized with arrival of the beam pulse has been developed. An enhanced stripper gas density as well as a simultaneously reduced gas load results in an increased stripping efficiency, while the beam emittance remains the same. A new record beam intensity (11.1 emA) for 238 U 28+ beams at 1.4 MeV/u has been achieved, applying the pulsed high density H 2 -stripper target to a high intensity 238 U 4+ beam from the VARIS ion source. Further ion source developments have been accomplished recently providing for sufficient heavy ion beam intensities at the High Current Injector Linac. A machine investigation program has been performed in 2020. The focus was to optimize the entire FAIR injector chain for high intensity heavy ion beam after the successful implementation of different upgrade measures. Besides a dedicated operation mode applying UNILAC, as a heavy ion Linac, at a synchronous phase significantly lower than 30 degrees for high intensity proton beam, could be established. Thus, UNILAC is able to deliver a sufficient proton beam intensity for the FAIR commissioning phase, when the FAIR-proton Linac is not yet available.
The GSI Universal Linear Accelerator UNILAC and the synchrotron SIS18 will serve as injector for the upcoming FAIR-facility. The UNILAC-High Current Injector will be improved and modernized until FAIR is commissioned and the Alvarez post stripper accelerator is replaced. The reference heavy ion for future FAIR-operation is uranium, with highest intensity requirements. To re-establish uranium beam operation and to improve high current beam operation, different subjects have been explored in dedicated machine investigation campaigns. After a beam line modification in 2017 the RFQ-performance had deteriorated significantly; new rods have been installed and the RF-working point has been redefined. Also the Superlens-performance had become unsatisfactory; improved with a modified RF-coupler. With a pulsed hydrogen gas stripper target the uranium beam stripping efficiency could be increased by 65%. Various work has already been carried out to establish this stripper device in routine operation. With medium heavy ion beams a very high beam brilliance at the end of transfer line to SIS18 was achieved. Results of the measurement campaigns and the UNILAC upgrade activities will be presented.
Numerous ambitious particle accelerator facilities, based on proton and ion linear accelerators, have recently been in development for fundamental research, as well as for industrial applications. The advanced design of such new machines, as well as the upgrade and optimization of existing linacs, requires adequate, precise and reliable tools to simulate beam dynamics. The software package DYNAMION, created about 30 years ago, is undergoing systematic improvement and further development in order to characterize modern ion linacs and to provide solutions for its intrinsic complex problems. The DYNAMION code features Front to End beam dynamics simulations under space charge conditions in a linac system, comprising an arbitrary sequence of accelerating-focusing structures and beam transport lines. The evolution of a macroparticle ensemble could be analyzed at a high level of specification. A 3D distribution of the external electrical field (RFQ, DTL) is modeled using integrated internal solvers. Optionally, a 3D electromagnetic field mapping, supplied by specialized external codes, could be used. The recent status of the DYNAMION software package is presented in this paper. Furthermore, the performance of the code is demonstrated on the basis of its application for various linear accelerator/decelerator projects.
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