CaSO₄:Tm thermoluminescent semi-spherical-shaped pellets for improved angular dependence dosimeters

Area of Science:

• Medical Physics
• Radiation Detection and Measurement

Background:

• Angular dependence of thermoluminescent (TL) pellets poses challenges in thermoluminescent dosimetry (TLD), particularly for personal dosimetry.
• Conventional cylindrical pellets exhibit significant angular dependency, impacting dose accuracy.

Purpose of the Study:

• To develop and evaluate semi-spherical CaSO4:Tm pellets for personal dosimetry.
• To improve angular dependence and assess dosimetric properties compared to cylindrical pellets.

Main Methods:

• Semi-spherical CaSO4:Tm pellets (27 mg, 2:1 PTFE to phosphor ratio) were fabricated.
• Pellets were irradiated with 137Cs source (0.5-50 mGy) to study sensitivity and dose response.
• Angular dependence was evaluated by comparing readings at different angles relative to 0°.

Main Results:

• Pellets showed dosimetric peaks at ~300°C and ~200°C.
• Linear dose-response observed from 0.5 to 50 mGy.
• Sensitivity: (58.8 ± 2.0) nC/mGy; Lower Detection Limit: (0.037 ± 0.001) mGy.
• Semi-spherical pellets exhibited significantly better angular dependence (max 4.6% difference) than cylindrical ones (max 32% difference) up to 90°.

Conclusions:

• Semi-spherical CaSO4:Tm (2:1) pellets show promise as TL detectors for personal monitoring.
• Improved angular dependence enhances accuracy in personal dosimetry applications.
• The developed pellets offer a viable alternative to conventional cylindrical TLDs.