A REAL-TIME PULSED PHOTON DOSIMETER

Radiation sources producing short pulses of photon radiation are now w idespread. Such sources include election and proton linear accelerator s, betatrons, synchrotrons, and field-emission impulse generators. It is often desirable to measure leakage and skyshine radiation from such sources in real time, on a single-pulse basis as low as 8.7 nGy (1 mu R) per pulse. This paper describes the design and performance of a pr ototype, real-time, pulsed photon dosimeter (PPD) capable of single-pu lse dose measurements over the range from 3.5 nGy to 3.5 mu Gy (0.4 to 400 mu R). The PPD may also be operated in a multiple-pulse mode that integrates the dose from a train of radiation pulses over a 3-s perio d. A pulse repetition rate of up to 300 Hz is accommodated. The design is eminently suitable for packaging as a lightweight, portable, surve y meter. The PPD uses a CdWO4 scintillator optically coupled to a phot odiode to generate a charge at the diode output. A pulse amplifier con verts the char ge to a voltage pulse. A digitizer circuit generates a burst of logic pulses whose number is proportional to the peak value o f the voltage pulse. The digitizer output is recorded by a pulse count er and suitably displayed. A prototype PPD was built for testing and e valuation purposes. The performance of the PPD was evaluated with a va riety of pulsed photon sources. The dynamic range, energy response, an d response to multiple pulses were characterized. The experimental dat a confirm the viability of the PPD for pulsed photon dosimetry.