Dose rate measurements with a ruby-based fiber optic radioluminescent probe

• Ruby based probes qualify for fiber optical dose rate measurements.
• Detection limit of the system is 2.6 mGy/h.
• The additional stem signal can be modeled by a linear function below and above the Cherenkov threshold.
• Decay characteristics enable time-selective discrimination of the stem effect.
• The behavior in a pulsed radiation field is simulated.

Fiber optic radioluminescence dosimetry allows real-time dose rate measurements in complex, narrow geometries and at places of high dose rates, without exposing the operator or the susceptible electronics. The keys are the spatial separation of radiation sensitive probe and electronic processing system and their optical connection by a flexible light guide. The small probes are capable of measuring fields of high dose rate gradients and the sealed probe-tip qualifies for applications in the fluid milieu and even for in-vivo-dosimetry. One problem of fiber optic dosimetry is the generation of Cherenkov radiation and fiber luminescence in the irradiated light guide, the so called stem effect. Ruby (Al2O3:Cr) has a narrow radioluminescent emission at 694 nm and is a potential luminophor for fiber optic radioluminescence dosimetry. In this work the influence of the stem effect on our ruby-based fiber optic dosimetry system is examined. The behavior of ruby probes under irradiation up to 0.5 kGy, as well as their luminescence decay characteristics and the applicability for measurements in radiotherapeutic fields are investigated.