Photoneutron spectrum measured with a Bonner sphere spectrometer in planetary method mode

Area of Science:

• Medical Physics
• Radiation Detection and Measurement

Background:

• Medical linear accelerators (LINACs) are widely used in radiotherapy.
• Understanding the photoneutron spectrum is essential for radiation safety and accurate dose calculations.
• Bremsstrahlung radiation from LINACs can produce photoneutrons, impacting the radiation field.

Purpose of the Study:

• To characterize the photoneutron energy spectrum produced by a 15 MV VARIAN iX LINAC.
• To evaluate the utility of a Bonner spheres spectrometer for in-beam measurements.
• To provide data for improving radiation shielding and treatment planning in clinical settings.

Main Methods:

• Photoneutron spectrum measurement using a Bonner spheres spectrometer.
• Utilized pairs of thermoluminescent dosimeters (TLDs) as thermal neutron detectors.
• Employed the planetary method for spectrometer positioning, requiring a single LINAC beam exposure.

Main Results:

• Successfully measured the photoneutron spectrum at 100 cm from the ionization chamber (IC) within a solid water phantom.
• The spectrum was obtained at a depth of 5 cm in the phantom.
• The planetary method allowed for efficient measurement with minimal LINAC beam time.

Conclusions:

• The study successfully characterized the photoneutron spectrum from a 15 MV LINAC.
• Bonner spheres with TLDs are effective for in-beam photoneutron spectrum measurements.
• The obtained spectral data are valuable for radiation protection and dosimetry in radiotherapy.