Pulseheight

Pulse height is the amplitude of an electrical pulse produced by a radiation detector when a quantum interacts with the detector material. In many detectors, such as scintillation counters and semiconductor detectors, the deposited energy is converted into a signal whose peak height is proportional to the energy deposited. The pulse height is typically measured with a pulse-height analyzer and recorded as a channel number in a multichannel analyzer after calibration.

Signal flow: incident radiation interacts in the detector and deposits energy; in scintillators this yields light, which photomultiplier tubes convert to electrical pulses, while in semiconductors the charge carriers produce current pulses. These pulses are shaped and amplified by a preamplifier and a shaping amplifier; the resulting peak is measured by a peak detector or an analog-to-digital converter. Digital systems may compute pulse height directly from sampled waveforms.

Calibration and spectrum: If the detector response is linear, pulse height is proportional to energy. Calibration with known gamma or X-ray lines maps pulse-height channels to energies. The pulse-height spectrum shows counts versus channel (or energy); peaks correspond to characteristic energies. The energy resolution, often expressed as full width at half maximum, depends on detector material, light yield, and electronics noise.

Applications and limitations: Pulse-height analysis is central to gamma-ray and X-ray spectroscopy, material analysis, dosimetry, and nuclear experiments. Common detectors include NaI(Tl) scintillators and HPGe detectors. Limitations include pile-up at high count rates, electronic noise, baseline drift, and nonlinearity; digital pulse processing can mitigate some issues.