Neutron dosimetry with a water calorimeter

In certain situations neutron radiotherapy has potential advantages over conventional X-ray therapy. It has yet to be conclusively proven that neutron therapy is more efficacious than X-ray therapy, and in many institutions worldwide neutron therapy is currently being evaluated. It is important that the dosimetry of neutron beams is consistent so that clinical results from different centres can be compared. Due to the relatively large uncertainties in the measurement of absorbed dose in neutron beams this consistency is difficult to achieve. This work describes the application of a recently developed dosimetry method, namely water calorimetry, to the field of neutron dosimetry. The concept of absorbed dose and its measurement are discussed. The theory behind radiation calorimetry in general, and specifically water calorimetry, is outlined followed by a review of water calorimetry and calorimeters for neutron dosimetry. The calorimeter, which consists simply of a thermally insulated tank of water, and its construction are described. The temperature rise in the water was detected by a thermistor which was incorporated in a Wheatstone bridge circuit. The merits of different configurations of bridge circuit are discussed and the literature on the subject is reviewed. The circuit employed was an AC bridge having asymmetric, inductive ratio arms. The output of the bridge was detected by a lock-in amplifier and the signal was fed directly to a microcomputer which stored and analysed the data.

Grantor dc:publisher

The University of Edinburgh

Year dc:date.issued

1986

Author dc:creator

• Galloway, Gordon.

Handle dc:identifier.uri

http://hdl.handle.net/1842/34284

OAI identifier oai:identifier

oai:era.ed.ac.uk:1842/34284