Gaseous Xe scintillator as a new particle-identification detector for high-intensity heavy RI beams*

RIKEN RIBF is one of the accelerator facilities which can provide high-intensity and heavy-ion unstable beams in the world. Because the unstable nuclei are produced by in-flight method in RIBF, particle identification should be performed event by event. However, beam intensity is limited by the radiation hardness and pile-up events of the particle-identification (PID) detectors. Especially, an ion chamber, which is a standard delta E detector in RIBF, is bottleneck due to the slow response.  Therefore, we have been developing a gaseous Xe scintillator. The reason for using a gas detector is that it is good radiation hardness since a gas state is structureless. The scintillation process of Xe gas is about 100 ns which is much faster than the response of the IC (decay time : ~100ns vs ~mu{}s order).  The averaged energy to emit one scintillation photon is about 20 eV. and the gas requires small energy to produce one scintillation photon (~20eV). Thus, the gaseous Xe scintillator is promising as a new standard beam-PID detector, especially as a delta{}E detector.

We have performed beam irradiation tests for the gaseous Xe scintillator several times until now. We have evaluated the performance by performing PID of cocktail beams. As a result, it was found that the Xe scintillator has a good energy resolution and makes it possible to separate atomic number Z of beams in a broad region of Z=20 to around Z=55. In addition, we found that it also has good timing and position resolutions.

In this presentation, we report the details of the test experiments and future prospects.