A Pulse Height Analyzer is an instrument used in nuclear and elementary particle physics

Particle physics

Particle physics is a branch of physics that studies the existence and interactions of particles that are the constituents of what is usually referred to as matter or radiation. In current understanding, particles are excitations of quantum fields and interact following their dynamics...

 research which accepts electronic pulses of varying heights from particle and event detectors, digitizes the pulse heights, and saves the number of pulses of each height in registers or channels for later spectral analysis. Synonymous terms for 'Pulse Height Analysis' are; "pulse height spectrum" or "pulse height distribution." A PHA is a specific modification to MultiChannel Analyzers os Spectrometer

Spectrometer

A spectrometer is an instrument used to measure properties of light over a specific portion of the electromagnetic spectrum, typically used in spectroscopic analysis to identify materials. The variable measured is most often the light's intensity but could also, for instance, be the polarization...

.

A pulse height analyzer is also used as integrated into particle counter

Particle counter

A particle counter is an instrument that detects and counts particles. By its very nature a particle counter is a single particle counter, meaning it detects and counts particles one at a time. The nature of particle counting is based upon either light scattering or light obscuration...

s, or as a discrete module to calibrate particle counters.