Neutron measurements in a Varian 2,100C LINAC facility using a Bonner sphere system based on passive gold activation detectors.
The use of high-energy linear electron accelerators (LINACs) for medical cancer treatments is widespread on an international scale. The associated bremsstrahlung X rays may produce neutrons as a result of subsequent photonuclear reactions with the different materials constituting the accelerator head. The generated neutron field is highly variable and depends strongly on the beam energy, on the accelerator shielding, on the flattering filter as well as on the movable collimators (jaws) design and on the irradiation field geometry. An estimate of this photoneutron component is, thus, of practical interest to quantify the radiological risk for the working staff and patients. Due to high frequency electromagnetic fields, and also to the presence of abundant leaked and scattered photons in these installations, measurements of the corresponding neutron fields by active dosemeters are extremely difficult. A modified version of the Bonner sphere system, based on passive gold activation detectors, has been used to perform neutron measurements at two points in a Varian 2,100C LINAC facility. A home-made unfolding procedure (CDM) has been utilised to determine the neutron spectra present at the measurement points. Results indicate that the giant dipole resonance process is the most adequate model to explain neutron production in the LINAC and that a thermal component is present at the measurement points.
Fernández
F
F
Grup de Física de les Radiacions, Departament de Física, Universitat Autónoma de Barcelona, E-08193 Bellaterra, Spain.
Domingo
C
C
Amgarou
K
K
Castelo
J
J
Bouassoule
T
T
Garcia
M J
MJ
Luguera
E
E
D004867:Equipment Design; D019544:Equipment Failure Analysis; D006046:Gold / Q000737:chemistry* / Q000528:radiation effects*; D009502:Neutrons; D016273:Occupational Exposure / Q000032:analysis*; D010315:Particle Accelerators / Q000295:instrumentation*; D011829:Radiation Dosage; D011834:Radiation Monitoring / Q000295:instrumentation* / Q000379:methods; D011835:Radiation Protection / Q000295:instrumentation* / Q000379:methods; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013030:Spain
D006046:Gold