A measuring system with a recombination chamber for neutron dosimetry around medical accelerators

Abstract

A measuring system for dosimetry of neutrons generated around medical electron accelerators is proposed. The system consists of an in-phantom tissue-equivalent recombination chamber and associated electronics for automated control and data acquisition. A second ionization chamber serves as a monitor of photon radiation. Two quantities are determined by the recombination chamber--the total absorbed dose and the recombination index of radiation quality. The ambient dose equivalent, H*(10), or neutron absorbed dose in an appropriate phantom, can be then derived from the measured values. Tests of the system showed that a 0.5% dose contribution of neutrons to the absorbed dose of photons could be detected and estimated under laboratory conditions. Preliminary tests at the 15 MV Varian Clinac 2300C/D medical accelerator confirmed that the measuring system could be used under clinical conditions. The H*(10) of the mixed radiation was determined with an accuracy of approximately 10%.

Ionisation Chambers Containing Boron as Neutron Detectors in Mixed Radiation Fields

“…The second chamber denoted as B3 is a large, ca 2000 cm 3 , recombination chamber of REM-2 type [6,7]. It has been filled with natural BF 3 and placed in one of the changeable moderators.…”

“…Gas-filled radiation detectors cannot detect neutrons directly but there are several nuclear reactions producing energetic charged particles that ionize atoms. These reactions include: n + 6 Li ® 3 T + a , n + 3 He ® 3 T + a and n + 10 B ® 7 Li + a .…”

“…Proportional counters, filled with either 3 He or gas compounds made with 10 BF 3 are the most frequently used neutron detectors. The technology of manufacturing such devices is well established, but there are several disadvantages of the proportional counters.…”

A review on photoneutrons characteristics in radiation therapy with high-energy photon beams

“…8,[12][13][14][15][16][17][18][19][20][21][22] However, the experimental methods have not been able to analyze the origin of neutrons reaching the dosimeter. The proposed method of choice to tackle this problem have been the Monte Carlo methods.…”

Research on angle sensitivity of the boron-lined multilayer converter neutron detector

“…Neutron detectors have been widely used in the fields of homeland security [1,2], industrial applications [3,4], medical treatment [5,6], and neutron spectroscopy [7][8][9], accelerating 5 Joint first authors. * Author to whom any correspondence should be addressed.…”