Hähnel, H.

Mickat, S.

Ratzinger, U.

Tiede, R.

GSI Repository

Development of a KONUS based High Energy Linac for the UNILAC∗H. Ha¨hnel†1, U. Ratzinger1, R. Tiede1, and S. Mickat21IAP, Goethe University, Frankfurt, Germany; 2GSI, Darmstadt, GermanyTo meet the requirements of 15 mA U28+ at 11.4 AMeVfor injection into the SIS18, the GSI UNILAC has to beupgraded. The Alvarez linac in the poststripper U28+ sec-tion of the UNILAC is nearing 40 years of operation andtherefore has to be replaced to ensure reliable and efficientoperation for FAIR. We propose an IH-DTL linac as re-placement for the current GSI UNILAC Alvarez. The newdesign is based on the KONUS beam dynamics conceptand delivers high beam quality well within FAIR require-ments. It will drastically reduce the fabrication costs andwill leave about 30 m within the UNILAC (Fig. 1) for laterlinac energy upgrades by e.g. 325 MHz CH-DTL cavitiesas in [1].existing   Alvarezproposed IH-DTLMEBTRFQI 1H I 2HSourceLEBTHLISIS18Figure 1: Sketch of the UNILAC accelerator (adapted [2]).The proposed linac consists of six 108 MHz IH-tanksand seven quadrupole triplet lenses (Fig. 2). It is designedto accelerate 15 mA U28+ from 1.4 MeV/u to 11.4 MeV/u.The beam dynamics simulation includes realistic estima-tions of necessary drift lengths for tank walls, lens housingand phase probes for all lenses. The drift tube aperture is25 mm and the lens aperture 40 mm with a maximum poletip field of 1.05 T for the highest gradient of 50.1 T/m. Themaximum on axis field is 11 MV/m.L1 L2 L3 L4 L5 L6 L70 m 5 m 10 m 15 m 20 m 25 mTank 1 Tank 2 Tank 3 Tank 4 Tank 5 Tank 6Figure 2: Sketch of the proposed IH-DTL.Beam Dynamics (preliminary)Beam dynamics simulations (LORASR) for the pro-posed high energy linac already show very promising re-sults. The used input emittances are a pessimistic estima-tion based on the prestripper output emittances using theMEBT upgrade as proposed by the authors in [3]. The∗Work supported by BMBF 05P12RFRB9† haehnel@iap.uni-frankfurt.detransversal input emittances are 0.8 mm mrad (90 %) andthe longitudinal input emittance is 6.3 keV/u ns (90 %). Amatching section with buncher will be necessary in front ofthe proposed design.0 5 10 15 20 251,01,11,21,3RMS emittance growthbeam axis [m] x-x' y-y' ph-WFigure 3: RMS emittance growth of the proposed high en-ergy linac section.The rms emittance growth along the proposed linac isshown in Fig. 3, indicating only 5.3 % in the longitudi-nal plane and about 30 % in the transversal planes. Fur-ther improvement in the transversal planes is expected tobe achieved by adjusting the focusing scheme (Fig. 4).0 5 10 15 20 25-20-1001020 100% 95%y [mm]    x [mm]beam axis [m]Figure 4: Transversal beam envelopes of the proposed highenergy linac section.In conclusion the proposed concept provides a modernalternative to the Alvarez concept. With a higher RF effi-ciency and lower production cost it can provide good beamquality. Further optimizations regarding beam quality aswell as first CST model studies are currently ongoing atIAP. Final judgment on beam quality relies on the avail-ability of beam dynamics simulations for the proposed newAlvarez.References[1] A. Almomani, U. Ratzinger, THPME010, Proc. IPAC2014[2] S. Mickat et al., MOPP060, Proc. LINAC2014[3] H. Ha¨hnel, U. Ratzinger, R. Tiede, MOPP062, Proc.LINAC2014FG-UNILAC-13 GSI SCIENTIFIC REPORT 2014408 DOI:10.15120/GR-2015-1-FG-UNILAC-13

Development of a KONUS based High Energy Linac for the UNILAC

http://repository.gsi.de/record/184125/files/FG-UNILAC-13.pdf

Development of a KONUS based High Energy Linac for the UNILAC

Abstract

Similar works

Full text

Available Versions

GSI Repository