Electrostatic shield for cryostat dewar

摘要

Coolant gas pumped into the inner flask (3) of a cryostat dewar (2) causes an unwanted electrostatic charge on the inner surface (34) of the inner flask (3). This electrostatic charge can put an unwanted noise into the electrical output from an electromagnetic detector (16) cooled by the cryostat (2). The invention comprises a foraminous metallic screen (7) interposed between coolant coils (5) of the cryostat (2) and said inner surface (34). The screen (7) siphons off unwanted electrostatic charge from said surface (34) while allowing coolant to contact said surface (34) and thus allow cooling of the detector (16).