• A. Facco, P. Modanese, F. Scarpa
  INFN/LNL, Legnaro (PD)
• Y. Ma
  CIAE, Beijing

The low-beta section of the ALPI linac at Laboratori Nazionali di Legnaro is being upgraded in order to double its energy gain from about 10 MV to 20 MV. This upgrade, performed with a rather limited investment in the background of the standard accelerator activities, is based on the replacement of some rf system components and minor modifications to the cryostats. The cavities, working at 80 MHz, require a 3 dB rf bandwidth of 15 Hz (obtained by means of strong overcoupling) to be locked in the presence of the large Helium pressure fluctuations of ALPI. Their average gradient, although exceeding 6 MV/m at the nominal 7 W power, is presently kept around 3 MV/m during operation, limited by the maximum available rf power in the linac. The ongoing upgrade requires the modification of all low-beta cryomodules to allow new, liquid Nitrogen cooled rf couplers and new, 1 kW amplifiers. A fully equipped prototype cryostat with four, beta=0.047 QWRs has been constructed and tested on line, and operated at 6 MV/m reaching or exceeding all the design goals. The test results will be reported and discussed and the project status will be presented.

• Y. Ma
  CIAE, Beijing
• A. Facco, F. Scarpa
  INFN/LNL, Legnaro (PD)

The low-beta section of the EURISOL driver linac is based on 176 MHz superconducting half-wave resonators (HWR) with beta=0.09 and 0.16. These cavities are an evolution of the 352 MHz ones, previously developed in the same framework, having similar dimensions and components except for their length and rf frequency. They are characterized by a double wall, all niobium structure with light weight, good mechanical stability and a side tuner cooled by thermal conduction. The new 176 MHz Half-wave cavities design includes a removable tuner, which allows to improve tuning range, mechanical stability and accessibility to the cavity interior. A beta=0.13 cavity, which could be suitable for linacs like the SARAF one, was also designed with the same concepts. Design characteristics and expected performance will be presented and discussed.

• Y. He, W. Chang, X. Du, Y. Ma, L.P. Sun, Z.J. Wang, J.W. Xia, C. Xiao, Y.Q. Yang, S.H. Zhang, Z.L. Zhang, H.W. Zhao
  IMP, Lanzhou
• J.E. Chen, M. Kang, Y.R. Lu, Q.F. Zhou, K. Zhu
  PKU/IHIP, Beijing

Heavy Ion Research Facility at Lanzhou (HIRFL) consists of two cyclotrons (SFC and SSC), one synchrotron (CSRm), and one storage ring (CSRe). The two cyclotrons are in series as the injector of the synchrotron. An additional LINAC injector for SSC is considered to increase the beam time at targets. The new injector consists of an RFQ and four IH-DTL tanks. A pre-buncher in the front of RFQ is 13 MHz to match the RF frequency of SSC. The LINAC can operate in two modes. In the first mode, the middle-mass ions output with energy of 0.54 MeV/u, and then SSC accelerates them up to the energy of 5.62 MeV/u. The beam is used to do the Super Heavy Elements (SHE) experiments. In the second mode, the very heavy ions output with energy of 0.97 MeV/u, and then SSC accelerates them up to energy of 10.06 MeV/u. The beam is injected into CSRm after stripped. Code LINREV and DAKOTA are used to design and optimize the acceleration structures of DTLs. The energy spread less than ±0.5% and bunch length less than 2.6 ns are achieved at the exit of the last tank. These can match the ideal acceptance of SSC. A simulation from LEBT to exit of DTL is done by Beampath to benchmark the design.

* All authors belong to PKU-IMP RF LINAC Research Center for Heavy Ions.