Electron Counting and Plasma Temperature Measurement with a Silicon Photomultiplier

The Berkeley nonneutral plasma trap uses a microchannel plate-phosphor screen assembly to detect plasma particles as they emerge from the strong magnetic field of a Penning-Malmberg trap. Until recently, charge was measured with a pickup capacitively coupled to a high voltage line. This method suffered from a sensitivity limit set by microphonic noise. We have employed a silicon photomultiplier (SiPM) to measure the charge via the light emitted by a fast (P47) phosphor, thus completely decoupling from measurable noise sources. The design and performance studies of the new SiPM diagnostic will be reported, including the achievement of single electron resolution.