CPC G02B 6/3538 (2013.01) [H01J 37/244 (2013.01); H01J 37/3045 (2013.01); H01J 2237/28 (2013.01)] | 13 Claims |
1. An adjustable attenuation optical unit, comprising:
a lightguide having an input, an output and an exterior surface extending between the input and output that surrounds a core, wherein the light guide is configured such that light received at the input propagates through the core of the lightguide and exits from the output;
a photomultiplier tube operatively coupled to receive light that propagates through the lightguide; and
an adjustable attenuator coupled between the input of the lightguide and the photomultiplier tube and configured to reduce an intensity of light that propagates through the lightguide prior to the light reaching the photomultiplier tube.
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