NDTnet 1998 Aug, Vol.3 No.8

Abstract

Real Time Radiography (RTR) finds extensive applications for inspection of objects on assembly lines for rapid inspection. A typical RTR widely used includes a image intensifier, CCD camera, image processor and high resolution TV monitor in addition to radiographic source. Image intensifiers used in X-radiography employ CsI as the input detector. With the increased use of neutrons as radiation source, real time neutron radiography is also being practised widely. Image intensifiers used in neutron radiography employ gadolinium as the input screen. It is well known that rare earth screens such as gadolinium oxysulphide are sensitive to photons as well. While such screens have been used in fluoroscopy, no systematic study has been made to evaluate their potential usage for real time applications using X-rays. One possible reason for this could be due to their non-linear response over the X-ray energy range.

The neutron image intensifier system at the authors laboratory (model Andrex Truvision) essentially consists of a 9" Trifield image intensifier tube, motorised zoom lens, CCD camera and a high resolution TV monitor. RTR systems are best characterised using modulation transfer functions (MTF). In simplified terms MTF can be defined as the ratio of the image contrast to the object contrast.

A systematic study was undertaken by the authors to establish the MTF of the neutron image intensifier system. Comparison of the MTF of this system with that of a X-ray image intensifier with similar configuration revealed very little differences. Detailed experiments using a series of step wedges were then undertaken which indicated good similarities in the contrast response of Gd based and CsI based systems In the photon energy range of 100 - 4 10 kV. The results are quite interesting as a single system can be used for simultaneous real time neutron and X- / ray applications where both neutron and X-/ radiography facilities are available resulting in tremendous cost savings and complementary imaging information. One such facility dedicated for neutron radiography (KAMINI) is coming up at the authors laboratory. This paper would also highlight the salient features of this facility and the use of this equipment for simultaneous neutron and gamma radiography applications.

Abstract Source:
Book of Abstracts, 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN: 87-986898-0-00

Full-Text Source:
Proceedings of the 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN:

Publication Contact:
7th ECNDT, Park Alle 345, DK-2605 Broendby, Denmark, Fax: +45 46 26 70 11, Email: 101373.3414@compuserve.com