Showing papers by "Stephen W.S. McKeever published in 2004"

Recent advances in dosimetry using the optically stimulated luminescence of Al2O3:C.

Abstract: This paper presents an overview of some very recent developments in optically stimulated luminescence (OSL) dosimetry using aluminium oxide (Al 2 O 3 :C), with special emphasis given to the work of the research group at Oklahoma State University. Some of the advances are: (i) the development of a real-time optical fibre system for in viva dosimetry applied to radiotherapy; (ii) the development of a fibre dosimetry system for remote detection of radiological contaminants in soil; (iii) the characterisation of Al 2 O 3 :C in heavy charged particle fields and the study of ionisation density dependence of the OSL from Al 2 O 3 :C; and (iv) fast and separate assessment of beta and gamma components of the natural dose rate in natural sediments. These achievements highlight the versatility of the OSL technique associated with the high-sensitivity of Al 2 O 3 :C for the development of new dosimetry applications.

Optically stimulated luminescence radiation dosimetry method to determine dose rates during radiotherapy procedures

Abstract: There is provided a system and method for estimating radiation exposure in real time or in near-real time while a dosimeter is being irradiated. In the preferred arrangement, OSL will be used to calculate estimates of the radiation dose rate, preferably by using comparisons between illumination values measured during and after lighting the dosimeter with a laser light of a predetermined frequency. A first preferred embodiment utilizes quasi-equilibrium OSL intensity with periodic stimulation during continuous irradiation. Another preferred embodiment utilizes the amplitude of the transient OSL signal during periodic stimulation. Another preferred embodiment utilizes the difference between the OSL intensity at the end of one stimulation period and the beginning of the next. Finally, another preferred monitors the time constant for the return of the transient OSL signal to equilibrium, following either a change in dose rate or during a periodic optical stimulation.

Optically stimulated luminescence radiation dosimetry method to determine integrated doses and dose rates and a method to extend the upper limit of measurable absorbed radiation doses during irradiation

Abstract: There is provided herein a system and method for obtaining measurements of radiation exposure in real time using OSL and for obtaining improved accurate OSL measurements over a greater range of radiation exposures. In a preferred embodiment a signal-versus-dose response is obtained from an OSL dosimeter that is linear over all doses and does not exhibit saturation effects. The desired response is preferably calculated from the measured OSL-versus-time response from a suitable dosimeter obtained during irradiation. To obtain the desired response from the measured OSL data each measured OSL point has to be corrected for the depletion of the trapped electron concentration that occurs during each illumination period.

Discrimination of Heavy Charged Particles in a Mixed Irradiation Using Optically Stimulated Luminescence Methods

Abstract: Introduction: Astronauts are subjected to many different types of radiation In an effort to keep track of the dose an astronaut receives, they wear dosimeters that can be read by different means The newest method, termed Optically Stimulated Luminescence, entails using a known wavelength of light to stimulate the dosimeter material causing it to emit light of a different wavelength By measuring the amount of light emitted, we can infer the dose received The material we used for OSL dosimetry is aluminum oxide, Al2O3 In this study, we investigated the potential of Al2O3 for discrimination of different types of radiation (alpha and beta in this study) Heavy charged particles (HCP), such as alpha particles, deposit energy in a different way than do other forms of radiation, such as beta, gamma, or Xray Where non-HCP’s deposit most of their energy uniformly across the material, HCP’s deposit most of their energy along linear tracks following the path of the particle This results in a possible low dose averaged over the entire material, but very high dose in small volumes along the particle track HCP’s are more prone to cause radiobiological damage [1] By discriminating between how much dose was from HCP’s, we can determine more accurately the health risk to an astronaut This study is also applicable to airline pilots subjected to cosmic rays, since this is the ma in source of HCP radiation