X-, γ, β-ray detector windows of composite material replacing beryllium in the 4.2–420 K temperature range

Abstract

A new multilayer composite material has been elaborated to produce windows with a good vacuum tightness and high nuclear radiation transmission. This material can advantageously substitute beryllium, because of the difficulties associated with the fabrication of thin laminated beryllium windows without chemical impurities, because of the lack of resistance to atmospheric corrosion and the high cost of these windows. The composite windows are made of thin high purity aluminium barriers (0.15–0.56 μm total thickness) interleaved in structural polyimid films (down to 56 μm total thickness). Its main physical properties are: yield stress (1.2×10 8 Pa), temperature range ( 1 ̌ K to 420 K) . helium gas porosity (10 −3 cm 3(STP) m −2 atm −1 d −1), optically opaque. The X or γ-ray transmission performance tests have been compared with those for beryllium. They show that the standard multi-interlaminar barrier (MIB) material of 168 μm thickness is equivalent to 500 μm Be for energies lower than 10 keV and to 200 μm Be for energies higher than 100 keV. The windows thus developed have a modular aspect and adapt themselves to various specifications (cryostats, scintillation detectors, semiconductor detectors, X-ray proportional counters, etc.).