JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken
A 3GeV Rapid-Cycling Synchrotron (RCS) in Japan Proton Accelerator Research Complex (J-PARC) has been commissioned since September 2007. The most important issue in the beam study is to reduce unnecessary beam loss and to keep the beam line clean for the sake of maintenance and upgrade of the machines. From experience of the former accelerators, the average beam loss should be kept at an order of 1 watt per meter for hands-on maintenance. Since it is very difficult to control the beam loss at such a low level, the only measure we can take is to localize any of the losses in a restricted area, where deliberate modules should be provided for quick coupling and remote handling in order to mitigate the personal doses. Accordingly, we have designed the beam collimation system for the purpose of the beam loss localization. We report the performance of the beam collimation system of RCS through the first commissioning results and the residual doses around RCS components.
PSI, Villigen
The ring cyclotron at the PSI accelerator facility accelerates protons to 590MeV with a current of 2 mA at present. The stepwise increase to 3 mA is planned. During normal operation there are main beam loss points at targets, beam dumps and collimators. If the beam strikes material particles are lost due to multiple scattering. Subsequent nuclear reactions lead to the production of activated materials in the components itself and their surroundings. During shutdown radioactive components have to be removed for disposal or repair. To some extent the removal requires operations done by personnel nearby the activated components. To estimate the personal dose and to plan working procedures, a way to calculate the expected dose is essential. In addition, for later disposal of the radioactive components the nuclide inventory is required by the authorities. The Monte Carlo particle transport code MCNPX coupled to the build-up and decay codes SP-FISPACT, Orihet3 and Cinder’90, as well as the bookkeeping system PWWMBS developed at PSI, are used to calculate the required quantities. Both methods will be presented and the results are compared to measurements of different activated components.