CYCLOTRONS 2010 - List of Keywords (radioactivity)

Paper	Title	Other Keywords	Page
MOPCP014	Activation of a 250 MeV SC-cyclotron for Protontherapy	cyclotron, proton, extraction, beam-losses	72
	J.M. Schippers, D.C. Kiselev, R. Lüscher, O. Morath, M. Wohlmuther PSI, Villigen, Switzerland B. Amrein, P. Frey, M. Kostezer, A. Schmidt, G. Steen PSI-LRF, Villigen, PSI, Switzerland
	Dedicated Cyclotrons of 230-250 MeV are used at protontherapy facilities since ~12 years. Beam losses at acceleration and extraction cause buildup of radioactivity in the cyclotron, having consequences for accessibility, service and decommissioning. At PSI a dedicated 250 MeV SC-cyclotron is used for proton therapy since 2007. The machine has been optimized to obtain a high extraction efficiency of over 80%. Apart from these losses, most other losses occur at a pair of phase slits at 21 cm radius. Here we report on a systematic study of the radioactivity at selected locations in the pole, the RF system and of some screws located near the median plane. The spectra of gamma rays emitted from iron plugs in the pole, copper disks in the liner and several screws have been measured with HPGe detectors. From these spectra the isotopic compositions have been derived and compared with activities calculated with the Monte Carlo transport code MCNPX. Dose rate measurements have been made as a function of time. The data and beam history of the cyclotron allow us predictions of the dose rate during service activities shortly after beam interruption as well as after a specified life time.

Paper

Title

Other Keywords

Page

MOPCP014

Activation of a 250 MeV SC-cyclotron for Protontherapy

cyclotron, proton, extraction, beam-losses

72

J.M. Schippers, D.C. Kiselev, R. Lüscher, O. Morath, M. Wohlmuther
PSI, Villigen, Switzerland
B. Amrein, P. Frey, M. Kostezer, A. Schmidt, G. Steen
PSI-LRF, Villigen, PSI, Switzerland

Dedicated Cyclotrons of 230-250 MeV are used at protontherapy facilities since ~12 years. Beam losses at acceleration and extraction cause buildup of radioactivity in the cyclotron, having consequences for accessibility, service and decommissioning. At PSI a dedicated 250 MeV SC-cyclotron is used for proton therapy since 2007. The machine has been optimized to obtain a high extraction efficiency of over 80%. Apart from these losses, most other losses occur at a pair of phase slits at 21 cm radius. Here we report on a systematic study of the radioactivity at selected locations in the pole, the RF system and of some screws located near the median plane. The spectra of gamma rays emitted from iron plugs in the pole, copper disks in the liner and several screws have been measured with HPGe detectors. From these spectra the isotopic compositions have been derived and compared with activities calculated with the Monte Carlo transport code MCNPX. Dose rate measurements have been made as a function of time. The data and beam history of the cyclotron allow us predictions of the dose rate during service activities shortly after beam interruption as well as after a specified life time.