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This thesis aims to characterise the accuracy of a new active CMOS pad detector for dosimetry in HDR Brachytherapy. A 1x1x1 mm3 detector is doped with high resistivity n-type silicon, thickness of 100 μm (Wafer10) and 48 μm (Wafer20) epitaxial substrate and built in standard CMOS along with a transimpedance amplifier. This work investigates and examine this detector’s sensitivity and signal to noise ratio in air for use in High Dose Rate Brachytherapy (HDR BT) dosimetry. To understand operational characteristics of the detector, a current-voltage (I-V) characteristic curve was created, and the depletion voltage of the junction observed by using a Keithley Programmable Voltage Source to sweep the voltage and measure the current collected at the pad. Applying the established depleted voltage, the detector sensitive volume was tested by irradiating 5.5 MeV alpha beam with field size 1 mm x 1 mm at 1000 Hz event rate to observe the impact of radiation on the electronic and collection e
We assessed the accuracy of a prototype radiation detector with a built in CMOS amplifier for use in dosimetry for high dose rate brachytherapy. The detectors were fabricated on two substrates of epitaxial high resistivity silicon. The radiation detection performance of prototypes has been tested by ion beam induced charge (IBIC) microscopy using a 5.5 MeV alpha particle microbeam. We also carried out the HDR Ir-192 radiation source tracking at different depths and angular dose dependence in a water equivalent phantom. The detectors show sensitivities spanning from (5.8 ± 0.021) × 10−8 to (3.6 ± 0.14) × 10−8 nC Gy−1 mCi−1 mm−2. The depth variation of the dose is within 5% with that calculated by TG-43. Higher discrepancies are recorded for 2 mm and 7 mm depths due to the scattering of secondary particles and the perturbation of the radiation field induced in the ceramic/golden package. Dwell positions and dwell time are reconstructed within ±1 mm and 20 ms, respectively.