In some applications this protection is accomplished mechanically by electrical interlocks or shutters that protect the tube when the photomultiplier compartment is opened.
The spectrometer consists of a suitable scintillator crystal, a photomultiplier tube, and a circuit for measuring the height of the pulses produced by the photomultiplier.
The emission is also either passed through a filter or a monochromator before being detected by a photomultiplier tube, photodiode, or charge-coupled device detector.