• M.C.L. Buzio, P. Galbraith, S.S. Gilardoni, D. Giloteaux, G. Golluccio, C. Petrone, L. Walckiers
  CERN, Geneva
• A. Beaumont
  EBG MedAustron, Wr. Neustadt

At CERN, the con­trol of five of the ac­cel­er­a­tors in the in­jec­tor chain (i.e. PS, PS Boost­er, SPS, LEIR and AD) is based upon re­al-time mag­net­ic mea­sure­ments in a ref­er­ence mag­net. These sys­tems ("B-trains") in­clude usu­al­ly a field mark­er to sig­nal the achieve­ment of a given field value, com­ple­ment­ed by one or more pick-up coils to in­te­grate flux changes. Re­cent­ly, some is­sues have been raised con­cern­ing long-term re­li­a­bil­i­ty and pos­si­ble per­for­mance im­prove­ments, in terms of both res­o­lu­tion and op­er­a­tional flex­i­bil­i­ty, for these sys­tems. This paper re­ports the re­sults of R&D ac­tiv­i­ties launched to ad­dress these con­cerns, name­ly: the de­vel­op­ment of a novel fer­rite gra­di­ent com­pen­sator to en­able dy­nam­ic NMR field mark­ing in the PS' com­bined func­tion mag­nets; and the pre­lim­i­nary de­sign of a stan­dard­ized elec­tron­ic ac­qui­si­tion and con­di­tion­ing sys­tem aimed at en­abling the re­quest­ed im­prove­ments and at fa­cil­i­tat­ing rapid main­te­nance in­ter­ven­tions.

• M.C.L. Buzio, P. Arpaia, O. Dunkel, D. Giloteaux, G. Golluccio, A.M. Lombardi, F. Mateo Jimenez, S. Ramberger
  CERN, Geneva

Linac 4 is the in­jec­tor up­grade cur­rent­ly under con­struc­tion at CERN to im­prove lu­mi­nos­i­ty and re­li­a­bil­i­ty for the whole ac­cel­er­a­tor chain. This ma­chine will in­clude about 120 high-gra­di­ent, 20 mm aper­ture Hal­bach-ar­ray per­ma­nent quadrupoles (PMQ) housed in the Drift Tube tanks, as well as about 80 elec­tro­mag­net­ic quadrupoles (EMQ) with power cy­cles ap­prox. 2 ms long. This paper is con­cerned with the mag­net­ic mea­sure­ments car­ried out at CERN on the first batch of PMQ, in­clud­ing sev­er­al pro­to­types from dif­fer­ent man­u­fac­tur­ers, as well as those done on sev­er­al spare Linac 2 EMQs reused in Linac 4's 3 MeV test stand. We first de­scribe the test setup, fo­cus­ing our at­ten­tion on a pro­to­type test bench based on tech­nol­o­gy de­vel­oped for the LHC and able to carry out high-pre­ci­sion har­mon­ic mea­sure­ments in both con­tin­u­ous­ly-ro­tat­ing and step­ping-coil mode (FAME*). Next we pre­sent the re­sults ob­tained in terms of in­te­gral field strength and qual­i­ty, with spe­cial em­pha­sis on the anal­y­sis of very fast eddy cur­rent tran­sients in the EMQs. Fi­nal­ly, we dis­cuss the ex­pect­ed im­pact of these find­ings on the op­er­a­tion of the ma­chine.

* N. R. Brooks et al, "Estimation Of Mechanical Vibration Of The LHC Fast Magnetic Measurement System", IEEE Transactions on Applied Superconductivity, vol. 18, No. 2 , 2008.