• 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.