Mechanical Vibration Measurements on TTF Cryomodules

Few of the TTF cryomodules have been equipped with Wire Position Monitors (WPM) for the on line monitoring of cold mass movements during cool-down, warm-up and operation. Each sensor can be used as a detector for mechanical vibrations of the cryostat. A Digital Receiver board is used to sample and analyze with high frequency resolution, the WPM picked up signals, looking to its amplitude modulation in the microphonic frequency range. Here we describe the new acquisition system and show the first vibration spectra detected during normal operation of the TTF cryomodules # 4 and # 5.