DEVELOPMENT OF COMPOSITE FLUORESCENT SCREENS FOR HIGH ENERGY X- RAY IMAGING APPLICATIONS
P. K. Chaturvedi, K. M. Reddy, V. N. Rao, C. Subbaiah, R. N. Battacharya, K. Viswanathan and S. K. Athithan SHAR Centre, ISRO, Sriharikota
Keywords: Fluorescent screen, X-ray Imaging, High Energy Imaging, Rocket Motor Inspection, Industrial Application
ABSTRACT
X-ray imaging technique is an important tool for the real time radiographic inspection and it is commonly used in the medical and industrial application. These systems can be classified for the low and high X-ray energy applications. High energy X-ray imaging system are mainly used in the Solid Propellant Rocket Motor inspection and large metallic structures like pressure vessels etc. Development of a high energy X-ray imaging screen is a high tech. area and this component is made by very few companies in the world and its import is not ensured due to various reasons. This paper deals with the indigenous development of a high energy X-ray imaging screen using a new concept of composite screen made up of Gadolinium Oxy Sulphide. Interaction of high energy X-rays with the matter is a complex phenomena and it becomes extremely difficult task to obtain a quality image when the High Energy X-ray environment becomes extremely noisy due to unwanted photons of varying energy. Therefore while designing a fluorescent screen for high energy X- ray imaging applications, one has to carefully select front end converter and filter, phosphor, material purity and other parameters such as optimum thickness, particle size, homogeneity etc. This paper deals with the design and development aspect of the Tungsten backed Gadolinium Oxy Sulphide (GOS) fluorescent screen made for the 15 MeV X-ray and 9 MeV X-ray photon energies. Criteria for the selection of materials, optimisation of the illumination level with respect to particle size of the phosphor material, thickness of the GOS material and Tungsten material, processing details of the fluorescent screens, etc are also discussed in this paper. A special technique was developed for directly depositing the phosphor material on the Tungsten sheet so that the requirement of intimate contact between them is achieved. These composite fluorescent screens were successfully tested with 15 MeV Linear Accelerator and 9 MeV Linear Accelerator machines of SPROB using standard penetrameters placed on the test articles. Test results of these screens are discussed in this paper.
Publication Source: Trends in NDE Science & Technology; Proceedings of the 14th World Conference on Non-Destructive Testing, New Delhi, 8-13 December 1996.Vol. 3, pages 1309 - 1312 Publisher:Ashgate Publishing Company
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