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The neutron back scattering technique is used to search for land mines. Advantages of this technique are: the speed of detection, the ability to detect metal free mines, and the insensitivity to metal and pebbles. The method is sensitive to soft moisture, therefore a desert environment is perfectly suited for application of the neutron backscattering technique. Tests were performed using various dummy mines and real defused mines in the Egyptian desert. Index Terms--Land mine detection, neutron generator, neutron scattering.

Uranium doping and thermal neutron irradiation effects on flux-pinning of silver Bi-Sr-Ca-Cu-O tapes were studied.

A study was conducted to examine the effects of neutron irradiation to phase-pure (Hg(sub 1-x)Bix)Ba2Ca2Cu3Oy superconductor. By measuring the magnetization and thermal conductivity of neutron-irradiated-superconductor, it was found that the inclusion of point-defects form irradiation diminishes transition temperature and destroys the coupling between neighboring superconducting grains.

We have developed a near field coded aperture imaging system for use with fast neutron techniques as a tool for the detection of contraband and hidden explosives through nuclear elemental analysis. The technique relies on the prompt gamma rays produced by fast neutron interactions with the object being examined. The position of the nuclear elements is determined by the location of the gamma emitters. For existing fast neutron techniques, in Pulsed Fast Neutron Analysis (PFNA), neutrons are used with very low efficiency; in Fast Neutron Analysis (FNA), the sensitivity for detection of the signature gamma rays is very low. For the Coded Aperture Fast Neutron Analysis (CAFNA[R]) we have developed, the efficiency for both using the probing fast neutrons and detecting the prompt gamma rays is high. For a probed volume of [n.sup.3] volume elements (voxels) in a cube of n resolution elements on a side, we can compare the sensitivity with other neutron probing techniques. As compared to PFNA, the improvement for neutron utilization is [n.sup.2], where the total number of voxels in the object being examined is [n.sup.3]. Compared to FNA, the improvement for gamma-ray imaging is proportional to the total open area of the coded aperture plane; a typical value is [n.sup.2]/2, where [n.sup.2] is the number of total detector resolution elements or the number of pixels in an object layer. It should be noted that the actual signal to noise ratio of a system depends also on the nature and distribution of background events and this comparison may reduce somewhat the effective sensitivity of CAFNA. We have performed analysis, Monte Carlo simulations, and preliminary experiments using low and high energy gamma-ray sources. The results show that a high sensitivity 3-D contraband imaging and detection system can be realized by using CAFNA.

A new position-sensitive detector is being developed for protein crystallography studies at a spallation source. Based on eight, independent, wire proportional chamber segments housed in a curved pressure vessel, the device covers a scattering angle of 120 degrees, and has a collecting area of 1.5m by 20cm. The position resolution will be about 1.3 mm FWHM, with a total counting rate in excess of one million per second. Timing resolution, essential for a spallation source application, is of order 1[micro]s and provides neutron energy determination that is well suited for crystallography. Advanced features of this device include a digital centroid finding scheme, a seamless readout between segments, and a wire array design that minimizes anode modulation. Details of the mechanical design are given, together with digital centroid measurements that illustrate accurate, uniform response.