A MINIATURE TISSUE-EQUIVALENT IONIZATION CHAMBER FOR PULSE DOSIMETRY.

Abstract : For radiobiological purposes it is desirable to measure the absorbed dose in the material of interest with a high degree of accuracy and precision. In regions of large spatial variation it is important that the detector be as small as possible. To meet both requirements a miniature three-terminal tissue-equivalent ionization chamber was designed. It was produced by using injection molding and ultrasonic welding techniques. The chamber has an outside diameter of 5.5 mm and an ionizing volume of approximately 0.01 cu cm. The chamber was exposed to pulses from the AFRRI-TRIGA reactor to evaluate its collection efficiency and precision. For 100,000-rad pulses with peak dose rates of 10 million rads per second the collection efficiency was measured to be 85 percent. For 7000-rad pulses the collection efficiency was 98 percent. The precision of the chamber for fifteen 1000-rad pulses gave a standard deviation of 0.2 percent. (Author)