CYCLOTRONS 2010 - List of Authors (Schippers, J.M.)

Paper

Title

Page

Activation of a 250 MeV SC-cyclotron for Protontherapy

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.

FRM1CIO04

Fast Scanning Techniques for Cancer Therapy with Hadrons - a Domain of Cyclotrons

410

J.M. Schippers
PSI, Villigen, Switzerland

In protontherapy fast 3D pencil beam scanning is regarded as the most optimal dose delivery method. The two transverse directions are covered by magnetic scanning and fast depth variations are achieved by changing beam energy with a degrader in the beam line. During the transversal scan the beam intensity is varied with kHz speed. This performance has a big impact on the accelerator concept. Routinely a very stable, reproducible and accurate beam intensity is needed, which is adjustable within a ms. Quick changes of the maximum intensity from the cyclotron are also needed when changing treatment room. The eye treatment room at PSI, for example, needs a 5-7 times higher intensity as the Gantry. Dedicated tools and setup procedures are used to switch area within a few seconds. Typical energy variations must be performed within 50-80 ms. In order to compensate the energy dependent variation (factor 100) of the transmission through the degrader it is convenient to compensate this, e.g. with an adjustable beam transport transmission or with Dee voltage. It will be shown that a cyclotron offers the most advantageous possibilities to achieve this ambitious performance.

Slides FRM1CIO04 [9.164 MB]

Paper	Title	Page
MOPCP014	Activation of a 250 MeV SC-cyclotron for Protontherapy	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.

FRM1CIO04	Fast Scanning Techniques for Cancer Therapy with Hadrons - a Domain of Cyclotrons	410
	J.M. Schippers PSI, Villigen, Switzerland
	In protontherapy fast 3D pencil beam scanning is regarded as the most optimal dose delivery method. The two transverse directions are covered by magnetic scanning and fast depth variations are achieved by changing beam energy with a degrader in the beam line. During the transversal scan the beam intensity is varied with kHz speed. This performance has a big impact on the accelerator concept. Routinely a very stable, reproducible and accurate beam intensity is needed, which is adjustable within a ms. Quick changes of the maximum intensity from the cyclotron are also needed when changing treatment room. The eye treatment room at PSI, for example, needs a 5-7 times higher intensity as the Gantry. Dedicated tools and setup procedures are used to switch area within a few seconds. Typical energy variations must be performed within 50-80 ms. In order to compensate the energy dependent variation (factor 100) of the transmission through the degrader it is convenient to compensate this, e.g. with an adjustable beam transport transmission or with Dee voltage. It will be shown that a cyclotron offers the most advantageous possibilities to achieve this ambitious performance.
	Slides FRM1CIO04 [9.164 MB]