Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Berlin
DESY, Hamburg
Local beam losses and beam profiles at particle accelerators are determined by measuring the ionizing radiation outside the vacuum chamber. Four different fiber optic radiation sensor systems will be presented. Two are based on the increase of radiation-induced attenuation of (Ge+P)-doped multimode graded index fibers, whereas with the third system detects the Cerenkov light generated by relativistic electrons in radiation hard fibers. The used fiber is an undoped multimode step-index fiber with 300 um core diameter. Dosimetry at high dose levels uses the radiation induced Bragg wavelength shift of Fiber Bragg Gratings. The selection of a suitable fiber for the individual application is an important requirement and depends on the type, doping, used wavelength and annealing behavior. In addition, the dose range, dose rate and temperature must be considered. At six accelerators all systems are used for in-situ beam optimization and dose measurement. This paper summarizes the basic of this measurement technology and the experience at linear accelerators and at storage rings.
