Author: Mahner, E.
Paper Title Page
WEPPD072 Frequency Fine-tuning of a Spin-flip Cavity for Antihydrogen Atoms 2690
  • S. Federmann, F. Caspers, E. Mahner
    CERN, Geneva, Switzerland
  • B. Juhasz, E. Widmann
    SMI, Vienna, Austria
  As part of the ASACUSA collaboration physics program a spin-flip cavity for measurements of the ground-state hyperfine transition frequency of anti-hydrogen atoms is needed. The purpose of the cavity is to excite anti-hydrogen atoms depending on their polarisation by a microwave field operating at 1.42 GHz. The delicacy of designing such a cavity lies in achieving and maintaining the required properties of this field over a large aperture of 10cm and for a long period of time (required amplitude stability is 1% within 12h). The present paper presents the frequency fine tuning techniques to obtain the desired centre frequency of 1.42 GHz with a Q value below 500 as well as the tuning circuit used for the frequency sweep over the desired bandwidth of 6 MHz.  
WEPPR010 Comparison between Electron Cloud Build-Up Measurements and Simulations at the CERN PS 2955
  • G. Iadarola
    Naples University Federico II, Science and Technology Pole, Napoli, Italy
  • F. Caspers, S.S. Gilardoni, G. Iadarola, E. Mahner, G. Rumolo, C. Yin Vallgren
    CERN, Geneva, Switzerland
  The build up of an Electron Cloud (EC) has been observed at the CERN Proton Synchrotron (PS) during the last stages of the LHC high intensity beam preparation, especially after the bunch shortening before extraction. A dedicated EC experiment, equipped with two button pick-ups, a pressure gauge, a clearing electrode, and a small dipole magnet, is available in one of the straight sections of the machine. A measurement campaign has been carried out in order to scan the EC build-up of LHC-type beams with different bunch spacing, bunch intensity, and bunch length. Such information, combined with the results from build up simulations, is of relevance for the characterization in terms of Secondary Emission Yield (SEY) of the chamber inner surface. The interest is twofold: this will enable us to predict the EC build up distribution in the PS for higher intensity beams in the frame of the upgrade program, and it will provide validation of the EC simulation models and codes.