Experimental Demonstration of a Tunable Energy-Selective Gamma-Ray Imaging System Based on Recoil Electrons.

The domain of gamma-ray imaging necessitates technological advancements to surmount the challenge of energy-selective imaging. Conventional systems are constrained in their dynamic focus on specific energy ranges, a capability imperative for differentiating gamma-ray emissions from diverse sources. This investigation introduces an innovative imaging system predicated on the detection of recoil electrons, addressing the demand for adjustable energy selectivity. Our methodology encompasses the design of a gamma-ray imaging system that leverages recoil electron detection to execute energy-selective imaging. The system's efficacy was investigated experimentally, with emphasis on the adaptability of the energy selection window. The experimental outcomes underscore the system's adeptness at modulating the energy selection window, adeptly discriminating gamma rays across a stipulated energy spectrum. The results corroborate the system's adaptability, with an adjustable energy resolution that coincides with theoretical projections and satisfies the established criteria. This study affirms the viability and merits of utilizing recoil electrons for tunable energy-selective gamma-ray imaging. The system's conceptualization and empirical validation represent a notable progress in gamma-ray imaging technology, with prospective applications extending from medical imaging to astrophysics. This research sets a solid foundation for subsequent inquiries and advancements in this domain.

The development of a rapid and highly sensitive monitoring system for radioxenon isotopes.

The rapid monitoring of radioactive gas is one of the most direct and sensitive methods used to characterize the leakage of nuclear installations, and its technical difficulty lies in achieving the goals of rapid and high sensitivity as much as possible. Several techniques, including adsorption at ultralow temperatures, impurity removal with hollow fiber membranes, and on-site measurements with low background, were used to develop a rapid and highly sensitive monitoring system for radioxenon isotope. This system could simultaneously separate xenon from air and measure radioxenon isotopes in a rapid and efficient way. The technical specifications of this system are as follows: the recovery of stable xenon is greater than 70%; and the MDCs of 133Xe and 135Xe are 4.3 Bq/m3 and 0.4 Bq/m3 within a 30 min cycle of sampling and testing, respectively. It is worth noting that the MDC of 133Xe here is only approximately 1/18000 to 1/800 of those obtained with other similar equipment, and the monitoring period of this system is one fortieth of that of noble gas equipment for OSI, for example, XESPM-III. As a result, the standard uncertainties are less than 16%. The system developed in this paper can be applied in leakage monitoring of nuclear facilities and can also provide instructive technical support for other tests, such as nuclear safety monitoring and evaluation.

Measurement of the gamma-ray sensitivity and signal-to-noise ratio of a new scattered-electron detector.

A new detector suitable for measuring high intensity pulsed gamma-ray sources and based upon scattered-electron method is proposed. The detector has a relatively flat energy response in the range of 0.4-5 MeV and works in current mode. The performances of the detector under several conditions were studied by Monte Carlo simulation using the MCNP code. A comparison between calculations and measurements performed using the 1.25 MeV line of Co-60 is also addressed. The experimental signal produced by the detector was thus studied and decomposed into its main components in order to establish the signal-to-noise ratio (SNR). The latter is compared to SNR calculated for other type of detectors.

On-line beam diagnostic method for high energy laser with large beam profile.

A novel on-line beam diagnostic method for continuous-wave high energy laser (HEL) is presented. The system based on this method is mainly consisted of a scanning circular reflector and a photodetector array disposed spatially. Laser beam passes through the system except a little part of whole beam is sampled and reflected into the detector array by the circular reflector. Through the arithmetic of spatial mapping and image restoration with the output signal of detector array, the spatial-temporal distribution parameters of the laser beam are obtained. The HEL beam of several hundred millimeters in diameter can be on-line measured with spatial resolution of 2 mm and temporal resolution of 30~50ms.