  The temperature of a nonneutral plasma confined in a Penning-Malmberg trap
can be determined by slowly lowering one side of the trap's electrostatic axial
confinement barrier; the temperature is inferred from the rate at which
particles escape the trap as a function of the barrier height. Often, the
escaping particles are directed toward a microchannel plate (MCP), and the
resulting amplified charge is collected on a phosphor screen. The screen is
used for imaging the plasma, but can also be used as a Faraday cup FC for a
temperature measurement. The sensitivity limit is then set by microphonic noise
enhanced by the screen's high voltage bias. Alternately, a silicon
photomultiplier (SiPM) can be employed to measure the charge via the light
emitted from the phosphor screen. This decouples the signal from the
microphonic noise and allows the temperature of colder and smaller plasmas to
be measured than could be measured previously; this paper focusses on the
advantages of a SiPM over a FC.
