A measurement of the fast-neutron sensitivity of a Geiger-Müller detector in the pulsed neutron beam from a superconducting cyclotron.
The kU value of a commercially available miniature energy compensated Geiger-Müller (GM) detector has been determined using the modified lead attenuation method of Hough. The measurements were made in a d(48.5)-Be neutron beam produced by the superconducting cyclotron based neutron therapy facility at Harper Hospital. The unique problems associated with making measurements in a 2 ms duration pulsed beam with a 20% duty cycle are discussed. The beam monitoring system, which allows the beam pulse shape at low beam intensities to be measured, is described. By gating the GM output with a discriminator pulse derived from the beam pulse shape, the gamma-ray count rates and dead-time corrections within the 2 ms pulse and between pulses can be measured separately. The kU value of (0.0245 +/- 0.0015) determined for this GM detector is consistent with the values measured by other workers with identical and similar detectors in neutron beams with comparable, but not identical, neutron spectra.
Maughan
R L
RL
Gershenson Radiation Oncology Center, Harper Hospital, Detroit, MI, USA.
Yudelev
M
M
Kota
C
C
D055592:Biophysical Phenomena; D001703:Biophysics; D017357:Cyclotrons / Q000706:statistics & numerical data; D005214:Fast Neutrons / Q000627:therapeutic use*; D006801:Humans; D019047:Phantoms, Imaging; D011874:Radiometry / Q000295:instrumentation* / Q000706:statistics & numerical data; D011880:Radiotherapy Planning, Computer-Assisted / Q000706:statistics & numerical data; D012680:Sensitivity and Specificity