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SU-E-T-157: Reproducibility of CVD Diamond Detectors for Radiotherapy Dosimetry.
G Betzel1,2,3, S Lansley1,2,3, D McKay1,2,3
1University of Maryland School of Medicine, Baltimore, MD.
Medical Physics
|May 19, 2017
Summary
Performance variations were observed in chemical vapor deposition (CVD) diamond x-ray detectors, even when using films from the same batch. These differences, mainly due to film thickness, may necessitate correction factors for accurate clinical measurements.
Area of Science:
- Medical Physics
- Materials Science
- Radiation Detection
Background:
- Chemical vapor deposition (CVD) diamond is a promising material for radiation detectors.
- Ensuring inter-comparability of detectors fabricated from the same material batch is crucial for reliable applications.
Purpose of the Study:
- To investigate the performance inter-comparability of three in-house fabricated CVD diamond x-ray detectors.
- To evaluate detector performance under clinically relevant conditions using a water phantom and a medical linear accelerator.
Main Methods:
- Three single-crystal CVD diamond detectors with 0.4 mm^3 sensitive volumes were tested.
- Measurements included leakage current, priming dose, response dynamics, dose linearity, dose rate, and angular dependence.
- A PTW water phantom and a six-MV photon beam from an Elekta Synergy linac were used.
Main Results:
- Detectors showed variations in leakage current and sensitivity (up to 10%).
- All detectors exhibited a priming dose of ~7 Gy and 2s rise/fall times.
- Dose rate dependence was similar, while angular dependence was minimal; film thickness was identified as the primary cause of performance differences.
Conclusions:
- Deviations in performance between CVD diamond detectors from the same batch were observed.
- Correction factors may be needed, similar to natural diamond detectors.
- Variations in film thickness due to manufacturing tolerances are likely the cause; preselecting films by thickness is recommended to minimize detector response variability.
