Instrumentation
Alpha particles, beta particles, gamma
rays, and X-rays
are measured using
the par- ticle’s energy
to produce an amplified pulse
of electric current
in a detector. These
pulses are counted to give the rate of disintegration. Three types of detectors com- monly are encountered: gas-filled detectors, scintillation counters, and semiconduc-
tor detectors. The gas-filled detector
consists of a tube filled with an inert gas, such
as Ar. When radioactive particles enter the tube,
they ionize the inert gas, producing
a large number of Ar+/e– ion pairs. Movement of the electrons
toward an anode and
the Ar+ toward a cathode generates
a measurable electric
current. A Geiger counter is one example of a gas-filled detector. A scintillation counter
uses a fluorescent material to convert radioactive particles into easily measurable photons.
For exam- ple, one solid-state scintillation counter, consisting of a crystal
of NaI with 0.2% TlI, produces several thousand photons
for each radioactive particle. Finally, in a semi- conductor detector the adsorption of a radioactive particle promotes thousands of electrons to the semiconductor’s conduction band, leading to an increase
in its con- ductivity. Further details
about radiation detectors, and the signal
processors used to count
particles.
Related Topics
Privacy Policy, Terms and Conditions, DMCA Policy and Compliant
Copyright © 2018-2024 BrainKart.com; All Rights Reserved. Developed by Therithal info, Chennai.