STATUS OF THE 325 MHz SC CH-CAVITY AT IAP FRANKFURT ∗ M. Busch † ,1 , F. Dziuba 1 , H. Podlech 1 , U. Ratzinger 1 , W. Barth 2,3 , S. Mickat 2,3 , M. Amberg 3 , K. Aulenbacher 3,4 1 IAP Frankfurt University, 60438 Frankfurt am Main, Germany 2 GSI Helmholtzzentrum, 64291 Darmstadt, Germany 3 Helmholtz-Institut Mainz (HIM), 55099 Mainz, Germany 4 KPH Mainz University, 55128 Mainz, Germany Abstract At the Institute for Applied Physics (IAP), University of Frankfurt, a s.c. 325 MHz CH-Cavity is under devel- opment 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 preliminary coupler simulations will be presented. THE 325 MHZ CH-CAVITY Presently many projects with high requirements re- garding beam power and quality (e.g. MYRRHA (Multi Purpose HYbrid Research Reactor for High-Tech Applications) [1]) and spallation neutron sources ask for new linac concepts. The superconducting CH-cavity ful- fill these specification because it reduces the number of drift spaces between cavities significantl compared to con- ventional low-β ion linacs [2]. Along with KONUS beam dynamics, which decreases the transverse rf defocusing and allows the development of long lens free sections, this yields high real estate gradients with moderate electric and magnetic peak fields So far a 19-cell, superconducting 360 MHz CH-prototype has been developed and successfully tested. Gradients of up to 7 MV/m, corresponding to an effective voltage gain of 5.6 MV were reached [3]. For future operations a new design proposal for high power ap- plications has been investigated. The new cavity will be operated at 325.224 MHz, consists of 7 cells, β = 0.1545 and has an effective length of 505 mm (see g. ). Novel components compared to the CH-prototype are: • inclined end stems • additional flange at the end caps for cleaning proce- dures ∗ Work supported by HIM, GSI, BMBF Contr. No. 06FY161I † busch@iap.uni-frankfurt.de Figure 1: Layout of the superconducting 7-cell CH-Cavity (325.224 MHz, β = 0.1545) [4]. • two bellow tuners inside the cavity • two ports for large power couplers through the girders Table 1: Specification of the 325 MHz CH-cavity. β 0.1545 frequency [MHz] 325.224 no. of cells 7 length (βλ-def.) [mm] 505 diameter [mm] 347.4 E a [MV/m] 5 E p /E a 5.1 B p /E a [mT/(MV/m)] 13 G[Ω] 64 R a /Q 0 1248 R a R s [kΩ 2 ] 80 Inclined end stems yield a more homogeneous fiel dis- tribution along the beam axis compared to straight stems because the magnetic high fiel volume and therefore the inductance is increased [5]. At the same time the longi- tudinal dimensions of the cavity can be reduced by about 20%-25% since an extended end cell is not needed for Proceedings of IPAC2011, San Sebastián, Spain MOPC082 07 Accelerator Technology T07 Superconducting RF 265 Copyright c ○ 2011 by IPAC’11/EPS-AG — cc Creative Commons Attribution 3.0 (CC BY 3.0)