Optically erasable samarium-doped fluorophosphate glasses for high-dose measurements in microbeam radiation therapy

Previous work has demonstrated that fluorophosphate (FP) glasses doped with trivalent samarium (Sm3+) can be used as a dosimetric detector in microbeam radiation therapy (MRT) to measure high radiation doses and large dose variations with a resolution in the micrometer range. The present work addres...

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Bibliographic Details
Published in:Journal of applied physics 2014-02, Vol.115 (6)
Main Authors: Morrell, B., Okada, G., Vahedi, S., Koughia, C., Edgar, A., Varoy, C., Belev, G., Wysokinski, T., Chapman, D., Sammynaiken, R., Kasap, S. O.
Format: Article
Language:English
Subjects:
Absorbance
Applied physics
Conversion
DOPED MATERIALS
Dosimetry
Electron paramagnetic resonance
Electron spin
ELECTRON SPIN RESONANCE
ELECTRONS
FLUORINE COMPOUNDS
Glass plates
HOLES
Illumination
Light sources
MATERIALS SCIENCE
Microbeams
Optical radiation
PHOSPHATE GLASS
Radiation dosage
RADIATION DOSES
RADIATION MONITORING
RADIATION PROTECTION AND DOSIMETRY
Radiation therapy
RADIOLOGY AND NUCLEAR MEDICINE
RADIOTHERAPY
SAMARIUM
SAMARIUM IONS
Spin resonance
X RADIATION
X-RAY DOSIMETRY
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Summary:Previous work has demonstrated that fluorophosphate (FP) glasses doped with trivalent samarium (Sm3+) can be used as a dosimetric detector in microbeam radiation therapy (MRT) to measure high radiation doses and large dose variations with a resolution in the micrometer range. The present work addresses the use of intense optical radiation at 405 nm to erase the recorded dose information in Sm3+-doped FP glass plates and examines the underlying physics. We have evaluated both the conversion and optical erasure of Sm3+-doped FP glasses using synchrotron-generated high-dose x-rays at the Canadian Light Source. The Sm-ion valency conversion is accompanied by the appearance of x-ray induced optical absorbance due to the trapping of holes and electrons into phosphorus-oxygen hole (POHC) and electron (POEC) capture centers. Nearly complete Sm2+ to Sm3+ reconversion (erasure) may be achieved by intense optical illumination. Combined analysis of absorbance and electron spin resonance measurements indicates that the optical illumination causes partial disappearance of the POHC and the appearance of new POEC. The suggested model for the observed phenomena is based on the release of electrons during the Sm2+ to Sm3+ reconversion process, the capture of these electrons by POHC (and hence their disappearance), or by PO groups, with the appearance of new and/or additional POEC. Optical erasure may be used as a practical means to erase the recorded data and permits the reuse of these Sm-doped FP glasses in monitoring dose in MRT.
ISSN:0021-8979
1089-7550
DOI:10.1063/1.4864424