Zamorano Labbé, Felipe E. (2019) Detector de neutrones basado en silicio con alto nivel de rechazo a fotones gamma y aplicación en radioterapia / Silicon-based neutron detector with high level of gamma rejection and radiotherapy application. Maestría en Física Médica, Universidad Nacional de Cuyo, Instituto Balseiro.
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Resumen en español
La demanda por instrumentos de detección y dosimetría de neutrones en campos mixtos de radiación es cada vez mayor. En el ambiente clínico, para los tratamientos de radioterapia con aceleradores lineales con energía sobre 10 MV, se producen neutrones vía reacciones (y,n) . Es importante estudiar el impacto de estos desde un punto de vista de la protección radiológica del paciente y las dosis secundarias que aumentan la posibilidades de desarrollar cáncer radioinducido. Usando la tecnología de semiconductores 3D ultra delgados recientemente desarrollados por el Instituto de Microelectrónica de Barcelona (IMB-CNM), el Laboratorio de Bajas Temperaturas del CAB (Centro Atómico Bariloche, Argentina), fabricó una cadena de detección compuesto por un detector U3DTHIN 20 µm, capa convertidora de neutrones BE-10 [Dosirad, 2019] enriquecida al 90%>, un amplificador compuesto por un Cremat CR-110-R2 Charge-sensitive-preamplifier, un Cremat CR-200-2 µs Gaussian-shapingamplifier, y un Cremat CR-210 Baseline-restoration-module [Cremat, 2019]; y un analizador de señales Amptek MCA 8000A [Amptek, 2019]. Se realizan varios experimentos para caracterizar la respuesta del detector ante fuentes conocidas como: una fuente 137"Cs, una fuente de 241"Am-Be moderado con distintos espesor de polietileno y un haz de neutrografía del CAB. La eficiencia de detección obtenida para fotones de 662 keV fue del orden de 10"-9. La eficiencia de detección para neutrones térmicos fue de 2,87± 0,15%, mientras que el factor de discriminación n/y fue de 2,2x10"7. Finalmente se hizo un mapeo de la distribución de flujo de neutrones térmicos por la sala de tratamientos y se evidenció como los neutrones forman “un mar” de neutrones térmicos que se comportan como un gas que se expande y distribuye homogéneamente. La tasa de dosis estimada en el interior de la sala de tratamientos fue de 28 µSv cada 100UM, mientras que en la puerta de entrada fue de 0,08 µSv cada 100UM.
Resumen en inglés
The demand for alternative neutron detection and dosimetry instruments has increased recently due to 3"He commercial restriction policys. In hospital environments, where radiation therapy treatments are done with linacs using beam energy above 10 MeV, neutrons are produced through reactions. From a radiological protection point of view, this is important to study because there is a growing concern of secondary cancer risk for patients undergoing treatments. Using the ultra-thin silicon 3D detector (U3DTHIN) technology recently developed by the Institute of Microelectronics of Barcelona (IMB-CNM), the Low Temperatures Laboratory of the Bariloche Atomic Center (CAB), developed a detection chain consisting of an U3DTHIN 20 m detector, neutron conversion layer BE-10 [Dosirad, 2019] enriched 90%>, an amplifier composed of a Cremat CR-110-R2 Charge-sensitive-preamplifier, a Cremat CR-200-2s Gaussianshaping- amplifier, and a Cremat CR-210 Baseline-restoration-module [Cremat,2019]; and an Amptek MCA 8000A signal analyzer. Several experiments were carried out to characterize the response of the detector to known sources as: a 137"Cs source, a 241"Am-Be source with different polyethylene moderator thicknesses and in the Neutron Imaging Facility of the RA6 Nuclear Research Reactor. The detection efficiency obtained for 662 keV photons was in the order of magnitud of 10"-9. The detection efficiency for thermal neutrons was 2,87±0.15%, while the discrimination factor n/y was 2,2x10"7. . Finally, a mapping of the thermal neutron flux distribution through the treatment room was accomplished and it was shown that thermal neutrons behave like a gas that expands and is homogeneously distributed. The estimated dose rate inside the treatment room was 28 µSv per 100MU, while at the entrance door it was 0,08 µSv per 100MU.
| Tipo de objeto: | Tesis (Maestría en Física Médica) |
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| Palabras Clave: | Radiotherapy; Radioterapia; Silicon; Silicio; Neutrons; Neutrones; Thermal neutrons; Neutrones térmicos; Linear accelerators; Aceleradores lineales; Neutron detectors; Detectores de neutrones |
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| Materias: | Medicina > Detección de neutrones en radioterapia |
| Divisiones: | Gcia. de área de Investigación y aplicaciones no nucleares > Gcia. de Física > Física médica |
| Código ID: | 889 |
| Depositado Por: | Tamara Cárcamo |
| Depositado En: | 12 Abr 2021 08:53 |
| Última Modificación: | 12 Abr 2021 08:56 |
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