SSNTD Technique in Photo-Neutron Applications

Abstract

Passive Solid State Nuclear Track Detectors (SSNTDs) are a versatile tool for neutron studies as has been shown long ago and several good quality materials are commercially available. They are useful for charged particle detection in the linear energy transfer (LET) range above the threshold value of ~10 keV μm-1. Linacs, operating above 6 MeV up to the energy region where radiotherapy is applied usually up to ~25MeV, induce unwanted photo-neutron field; their spectra shows two components due to reaction dynamics based on evaporation and knock-on mechanisms. Neutrons produced by Linacs are often neglected in health application; however, today it has become necessary to assess the effect on patient, staff and radiation workers. Radiation studies using SSNTDs play a major role in this case. Other fields also take advantage of the passive detectors properties; in fact they are employed with success to measure neutron signals relevant for plasma diagnostics as it was demonstrated at the RFX facility as part of the ITER project. The PADC-NTD techniques provide information on external neutron field values around the RFX-installation during pulsed operation. In any case, converter materials, as charged particles from (n, p) and (n, α) reactions, are required to produce neutron fingerprints through latent tracks. These once etched provide information on neutron fluence spatial values. Track histograms are then employed to determine photo-neutron induced damage in materials as well as radiation dose to both patient and professionally exposed workers. The estimated neutron fluence that can be determined by NTM covers a large range of values, the largest being above 1010(± 12%) neutrons/cm2.

Dosis equivalente ambiental H*(10) por neutrones producidos en un Varian Clinac 2300 mediante detectores tipo CR-39

“…El espectro de fotoneutrones en un LINAC es diferente al espectro de una fuente de 252 Cf, sin embargo, es considerado aceptable la calibración del detector tal y como lo recomienda la IAEA y la Comisión Nacional de Protección Radiológica (NCRP) [38,39]. Cabe destacar que Szydlowski y colaboradores, para un estudio en un Varian Clinac 2300 18 MV, expusieron los detectores CR-39 ante una fuente 252 Cf considerando que este procedimiento provee una calibración propia inclusive cuando el espectro en el LINAC es diferente del 252 Cf [40,41].…”

Photoneutron Flux Measurement via Neutron Activation Analysis in a Radiotherapy Bunker with an 18 MV Linear Accelerator

“…These unwanted doses and radiobiological activity also increase the risk of secondary cancer [7]. Products resulting from the photoactivation event also threaten the health of the employees and the people who are inside or outside facility [5,8,9]. Electronic devices in the treatment room are also adversely affected by the production of photoneutrons [9,10].…”

“…Products resulting from the photoactivation event also threaten the health of the employees and the people who are inside or outside facility [5,8,9]. Electronic devices in the treatment room are also adversely affected by the production of photoneutrons [9,10]. All of the materials found in the LINAC room are capable of doing neutron absorption reactions [11].…”