Present status of liquid rare gas scintillation detectors and their new application to gamma-ray calorimeters

Scintillation from liquid rare gases has a fast decay component with a high photon yield which is comparable to that of NaI(T1), although the wavelength is in the vacuum ultraviolet. On the basis of these properties, many investigators have tried to realize liquid rare gas scintillation detector. In particular, liquid Xe is expected to be an excellent detector medium for gamma-rays because of its fast response, its large atomic number, and high density. However, it is very difficult to achieve sufficient light collection as scintillator, because the light emission is in the vacuum ultraviolet. Recently, some groups have reported liquid Xe/Kr homogeneous scintillation calorimeters for high-energy gamma-rays using reflectors method, but their energy resolution was not as high as expected. In this situation it seems that the realization of liquid rare gas detectors may not be easy. In this paper, we review the physical properties of scintillation from liquid rare gas, the scintillation yields, the decay time constants and attenuation lengths. We summarize the results obtained with liquid rare gas scintillation detector. The present status of development of liquid Kr/Xe homogeneous scintillation calorimeters by using reflected light is described. A new device which observes only direct light is proposed as high-energy gamma-ray detector or homogeneous electromagnetic shower calorimeters for gamma-rays. (C) 1999 Elsevier Science B.V. All rights reserved.