• S.M. Pattalwar, R. Bate, R.K. Buckley, B.D. Fell, A.R. Goulden, P.A. McIntosh
  STFC/DL/ASTeC, Daresbury, Warrington, Cheshire

The su­per­con­duct­ing LINAC for the pro­posed New Light Source (NLS) pro­ject in the UK, will con­sist of 18 cry­omod­ules op­er­at­ing at 1.8 K, each hav­ing 8, 1.3 GHz cav­i­ties op­er­at­ing in CW mode. The cry­omod­ule de­sign and cryo­genic dis­tri­bu­tion scheme will be one of the key el­e­ments to achieve the de­sired per­for­mance from the su­per­con­duct­ing RF (SRF) linac. Around the world, sev­er­al large scale fa­cil­i­ties (based on SRF linacs) are al­ready op­er­at­ing (for ex­am­ple: CEBAF, SNS, FLASH) and sev­er­al more have been pro­posed (XFEL, ILC, Cor­nell ERL, etc.). In this paper we de­fine the re­quire­ments for an ap­pro­pri­ate cry­omod­ule, adopt­ing proven L-band tech­nol­o­gy sys­tems and also de­scribe the cryo­genic dis­tri­bu­tion scheme, in order to de­vel­op an ef­fec­tive and eco­nom­ic so­lu­tion for the NLS.

• B.L. Militsyn, B.D. Fell, L.B. Jones, J.W. McKenzie, K.J. Middleman
  STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
• I. Burrows, R.J. Cash
  STFC/DL, Daresbury, Warrington, Cheshire
• H.E. Scheibler, A.S. Terekhov
  ISP, Novosibirsk

ALICE is an En­er­gy Re­cov­ery Linac built at STFC Dares­bury Lab­o­ra­to­ry to in­ves­ti­gate the pro­cess of en­er­gy re­cov­ery. The pro­ject is an ac­cel­er­a­tor re­search fa­cil­i­ty in­tend­ed to de­vel­op the tech­nol­o­gy and ex­per­tise re­quired to build a New Light Source (NLS) in the UK based on a suite of Free-Elec­tron Lasers. Cur­rent­ly the ALICE gun ac­com­mo­dates only a sin­gle pho­to­cath­ode at any one time, and the sys­tem must be vent­ed to at­mo­spher­ic pres­sure for pho­to­cath­ode re­place­ment. To meet the strin­gent vac­u­um de­mands for good pho­to­cath­ode life­time, the sys­tem then re­quires bak­ing for up to three weeks. A new load-lock cath­ode prepa­ra­tion sys­tem has been de­signed as an up­grade to the ALICE gun. The load-lock can ac­com­mo­date up to six pho­to­cath­odes, and per­mits rapid trans­fer of pho­to­cath­odes be­tween the load-lock ac­ti­va­tion cham­ber and the gun, thus main­tain­ing the vac­u­um. The pho­to­cath­ode prepa­ra­tion fa­cil­i­ty was suc­cess­ful­ly com­mis­sioned in spring 2009, and has since per­mit­ted a quan­tum yield of 15% to be achieved at a wave­length of 635 nm. Present­ly, a new gun ves­sel and pho­to­cath­ode trans­port sys­tem is under man­u­fac­ture, with a view to this being ful­ly-in­stalled on ALICE in Spring 2012.