Hiroaki Sakurabata

Beam commissioning of the new proton therapy system for University of Tsukuba

Beam commissioning of the new proton therapy system for University of Tsukuba was started in September 2000. The present system employs a synchrotron with a maximum energy of 250 MeV and two rotating gantries. The beam was successfully accelerated up to 250 MeV and transported to the irradiation nozzles. The position of the beam extracted from the synchrotron was confirmed to be very stable and sufficient flatness for the irradiation area was realized by using the dual ring double scattering method developed at University of Tsukuba. Furthermore, synchrotron operation triggered by patient respiration signal was succeeded.

Fabrication of a copper chamber for a storage ring with broached inner surface

Abstract There have been several reports that photodesorption due to synchroton radiation from OFC copper chambers with machined surfaces is far lower than in stainless steel or aluminum alloy chambers. However, it is difficult to process machined surfaces for the inner surfaces of beam chambers. A surface treatment using broaching has been developed to cut the inner surface of the chamber. Tests of the photodesorption caused by synchrotron radiation in a small, broached, cylindrical cross-section chamber with a length of 30 cm have been reported. To adapt the broaching method to long chambers, prototype copper vacuum chambers with lengths of 1.8 m and 2 m have been fabricated. A chamber consists of a beam channel, a cooling channel, and a NEG pump channel. The beam channel, which has a hexagonal cross section, is broached. An ultimate pressure of 1 × 10 −8 Pa was obtained after bakeout at 200 °C for 24 h and NEG activation.