A new type of x-ray real time still image detector named `X ray to Visible Light PROM (XTV-PROM)' has been developed. XTV-PROM consists of a thin Bi₁₂SiO₂₀ (BSO) single crystal plate, transparent insulating layers, and two electrodes on both faces of the crystal plate. One electrode is transparent and the other refracts readout lights and lets in x rays. Several tens of keV x rays generate electron-hole pairs in the crystal and an x-ray image is recorded as a charge pattern. A voltage pattern generated from the charge pattern causes the Pockels effect and the recorded x-ray image is converted to the visible light image using the effect of the crystal. The recorded image can be erased and the device can be used repeatedly. The XTV-PROM with a large active area (18 X 18 mm²) and high resolution (25 micrometers ) has been made by a new process for polishing BSO crystal thinly. The XTV-PROM has a good response for bremsstrahlung x rays higher than 30 keV.

Intense photostimulated luminescence (PSL) is observed, for the first time, in x-ray irradiated europium-doped potassium chloride (KCL:Eu) single crystals. The intensity of PSL with a peak at about 420 nm, which is emitted by stimulation with 560 nm light, is proportional to the optical density of the F centers, which are created by x-ray irradiation, over the wide range of the x-ray absorbed dose. This suggests that KCl:Eu is one of the most attractive candidates for a two-dimensional x-ray imaging sensor utilizing the PSL phenomenon.

In order to improve the MTF of x-ray image intensifiers we have studied a new type of input phosphor screen. The input phosphor screen is made up of cesium iodide (CsI) columns that contain the ingredient that absorbs light. The ingredient reduces light dispersion in the input phosphor screen. It can make the MTF higher. We made the image intensifier that has the input phosphor screen with the light absorbing ingredient. The MTF characteristics of this image intensifier are higher than that of the conventional image intensifiers.

Photoemissive photon counting tubes of 40 mm diameter are routinely made, and 75 mm tubes are in development. When these tubes are coupled to a suitable scintillator, substantial quantum efficiency can be achieved from soft rays through to gamma energies. Available scintillators and their performance are described in this paper. The advent of fast PC compatible computers has enabled the electronics readout to be improved, simplified, and reduced in cost. The new electronic readout system is described, and the image processing capability outlined. The pulse height distribution is available to the user, and to a limited extent, this allows the user to measure the energy of the input photons to the system. Systems of this type are used for x-ray crystallography, and could find wider applications in nuclear medicine and gamma ray photography.

There is little information in the literature on the performance of working micro-channel plate (MCP) detectors at high x-ray energies. We have measured the absolute efficiency of a microchannel-plate-intensified, subnanosecond, one dimensional imaging x-ray detector developed at LLNL in the 1 to 100 keV range and at 1.25 MeV. The detector consists of a gold photocathode deposited on the front surface of the MCP (optimized for Ni K_(alpha ) x rays) to convert x rays to electrons, an MCP to amplify the electrons, and a fast In:CdS phosphor that converts the electron's kinetic energy to light. The phosphor is coated on a fiber-optic faceplate to transmit the light out of the vacuum system. Electrostatic focusing electrodes compress the electron current out of the MCP in one dimension while preserving spatial resolution in the other. The calibration geometry, dictated by a recent experiment, required grazing incidence x rays (15.6 degree(s)) onto the MCP detector in order to maximize deliverable current. The experiment also used a second detector made up of 0.071 in. thick BC422 plastic scintillator material from the Bicron Corporation. We compare the absolute efficiencies of these two detectors in units of optical W/cm² into 4 (pi) per x ray W/cm² incident. At 7.47 keV and 900 volts MCP bias, the MCP detector delivers approximately 1400 times more light than the scintillator detector.

Current approaches to digital radiography and tomography are dominated by the use of Scintillator-Photodiode arrays as detectors. To improve the quality of the data for such measurements it is desirable to increase the efficiency of the device both for the absorption of incoming x rays as well as the ratio of current produced per unit dose. In order to be of practical use, such detectors must maintain a high signal to noise performance and level of dark current stability in the presence of large radiation fluxes. In this laboratory, we are exploring the use of monolithic linear arrays that directly convert ionizing radiation into charge without the intervening photo-emission step. We have evaluated detectors made from CdTe as well as CdZnTe intrinsic material with a variety of contact methods. Our studies have shown that the relative efficiency of charge collection of the holes within the pulse shaping time is the most significant parameter governing their use. Data have been collected on this property from several devices. CdZnTe solid state devices produce over ten times the current per absorbed dose than a typical scintillator-photodiode. Recent advances in raw material production and contact technology provide detectors which can maintain their operating characteristics over kilo-rad of dose. Readout methods that use pulse counting mode operation have been evaluated. Results are shown on the sensitivity and spatial resolution of these detectors. Examples of results taken with multi-element, monolithic devices fabricated thus far are demonstrated with some estimates on the possibility for the production of larger arrays.

Experimental results are presented on the effects of x-ray radiation on superconducting samples of polycrystalline YBaCuO and BiSrCaCuO. The radiation effects are detected at 4.2 K by changes of the magnetization of the sample using a SQUID magnetometer. In the presence of ionizing radiation, the changes in magnetization correspond to release of trapped flux, fluxon destruction, and low frequency noise due to flux flow.

Low temperature (4.2 K) photoluminescence spectroscopy (PL) measurements were performed on mercuric iodide (HgI₂) crystals that were surface-doped with either iodine or mercury. Two methods of treatment were used to achieve the surface doping. The first is the direct immersion of HgI₂ samples into potassium iodide (KI) aqueous solution saturated with iodine or immersion into elemental mercury liquid. The second is the storage of HgI₂ crystals under either iodine or mercury vapor. Certain features in the PL spectra were correlated with the stoichiometry of the HgI_{2/ crystals modified by the surface doping. It was also found that if HgI(subscript 2} was exposed to air, an iodine deficient surface layer would form within a one-day period due to the preferential loss of iodine. Finally, the behavior of a broad emission band in the PL spectra and its implication in the fabrication of high quality HgI₂ nuclear detector is discussed.

The Vanderbilt University Free-Electron Laser Program is developing the capability to create near-monochromatic x rays for medical imaging and other purposes. For this experiment we feed-back the normal infrared FEL light to collide with the electron beam. This causes Compton backscattering of the incident photons which creates x rays. These x rays cannot feed an x-ray laser, but they have a collimated intensity and tunability which make them highly suitable for medical imaging. This paper is particularly focused on the x-ray beam transport to be used with this experiment. This transport must collimate the x-ray beam and re-direct it to match a beam chase located in the vault ceiling at a 40 degree angle to the electron beam axis. A brief description of the creation mechanism and x-ray beam properties are included.

A study is made of transmission of straight and curved thin-film gamma-waveguides. It is shown that in curved waveguides maintaining the limited number of waveguide modes a radiation flux may be appreciably attenuated due to radiation of photons into the medium surrounding a waveguide. Measurement was made of the angular distribution of photons passed through the x-ray guide.

We have developed a comparatively small soft x-ray source for application in our test facilities, which are used at present to support the developments of the astrophysical space projects XMM and AXAF. The instrument comprises a commercially available color television tube for generation of the electron beam, which is focused on exchangeable metal films serving as targets. The x rays are taken off after having transversed the foil target and have a sufficient spectral purity with regard to the experimental requirements. The maximum electric operating parameters correspond to an emission current of 100 (mu) A generated by a filament heating power of 6.6 watt at an accelerating voltage of 25 kV. The technical advantages of the instrument are lightweight construction, no water cooling, small size electric supply, cost efficient manufacturing, small sized focus, and quick access to the desired characteristic spectral line by exchange of a complete tube. We describe the measurements on the local x-ray intensity profile of the focus, the spectral features of the beam, and present the resulting performance data. A special development could be used as calibration sources in x-ray telescopes.

We have developed a moveable, multi-anode, electron-induced x-ray source for calibrating x-ray imaging detector systems. The source features four water-cooled, copper-based anodes that are easily replaced and interchangeable under vacuum. A spherically symmetric filament and anode configuration yields very symmetrical source spot sizes variable from 1 to 5 mm diam. The source is coupled to vacuum by means of a triple-axis translator with x and z motions computer controlled to better than +/- 13 micrometers step accuracy. Absolute source flux is continuously monitored with a proportional counter. We characterize the source spot in detail by aiming the anode towards a pin-hole imaging x-ray detector system. To date we have used Co, Fe, Mg, and Ge vapor-deposited on copper anodes. When filtered with Ni or Mg foils, these emitting materials provide sets of four moderately pure x-ray lines below 1.5 keV. High deposition purity as well as 1E-7 torr source chamber pressures help reduce source degradation. Source translation and data acquisition are computer controlled using a Macintosh/LabVIEW software system. We discuss the application of our source configuration to spatial calibrations of extended pinhole and slit imaging detector systems. In addition, our multi-anode capability is useful for calibrating x-ray spectrograph response versus wavelength.

A number of nuclear techniques have been utilized or considered for detecting concealed explosives. These techniques range from those utilizing multi-energetic x rays to those relying on high energy photons or neutrons. The physical principles behind these methods are reviewed. Each technique is critically examined, in view of its ability to distinguish explosive materials from other common materials of similar composition. The suitability of each method for use in airport security also is discussed.

We present a description of Monte Carlo simulations of the pulse height energy response of CCD x-ray detectors. Effects of event charge splitting between pixels are accounted for, and the variation of energy resolution and detection efficiency with event selection criteria are discussed. We show that there are important implications for background rejection efficiency, on-board calibration, and ground-based data reduction. In orbit energy resolution may become degraded by traps created by radiation damage. We present an analysis of trapping and emission time scales, which allows us to predict the energy resolution for a wide range of device operating conditions.

A system is described for calibrating high flux (10¹¹ W) x-ray detectors using moderate flux (10^-4 W) synchrotron and low flux (10^-7 W) conventional x-ray producing machines. The detectors have been designed for output currents of one milliampere to 100 amperes which results in output currents during calibration of approximately 10^-16 to 10^-12 amperes. The small calibration output currents led to the development of statistical methods to reduce the calibration measurement errors to acceptable levels. A personal computer is used to acquire, analyze, store, and display the calibration data in real time to allow the scientist to explore and correct the calibration technique or eliminate external noise sources.

Discovery that wide energy and angular control of x ray and neutron trajectories can be achieved with high efficiency by the use of shaped arrays of hollow capillaries has made possible important new applications in science, medicine, and industry. These include medical diagnostic imaging, medical therapy, analysis of the composition and structure of materials, x-ray microscopy, x-ray astronomy, industrial process and fault analysis, and x-ray lithography. The status and prospects for this remarkable range of possibilities is summarized in this report.

X-ray fiber optics are bundles of hollow tubes which transmit x rays by multiple grazing incidence reflections. They provide a means of shielding XUV and x-ray instruments used for plasma diagnostics of magnetic confinement devices from the adverse effects of energetic neutrons and neutron induced gamma radiation. We have designed and built x-ray transmitting fiber optic bundles for instruments covering the ranges 60 to 200 eV and 3 to 10 keV. We have measured the performance of such bundles in the laboratory at 280 eV and at 6.4, 8, an 10 keV and compared it with simple computer models of x-ray fiber transmission.

The surface finishing of X-ray grazing incidence optics is the most demanding area of optical processing. both in terms of metrology and application of optical finishing techniques.This paper discusses the application of specialized metrology and finishing techniques in producing a low x-ray scatter grazing incidence telescope.

A numerical simulation for the transmission of x rays through glass capillaries of different geometries is described. The simulation includes corrections for surface roughness and absorption losses of the glass. These calculations are compared with experimental measurements of the transmission and exit divergence of the x rays. By fitting the experimental results with the calculations, the surface roughness of a capillary is estimated.

All focussing x-ray telescopes that have been in orbit (Einstein, EXOSAT, and ROSAT) or are currently being developed (e.g., ASTRO-D, SAX, AXAF, and XMM) are based upon the same type of optics, the Wolter Type I system or a conical approximation of it. With funding, weight, and volume now being severely limited, new investigations in x-ray astronomy will have to specialize on a particular study, e.g., wide field surveys, spectroscopy, broad band measurements, and should have significantly more capability than the current missions in that study. Several novel approaches to broad band and wide field optics have been described in the literature that may be able to satisfy certain specific objectives better than the Wolter I.

We present a concept of continuously graded multilayer structures for medium-sized x-ray telescopes which is based on several material combinations. We show that the theoretical reflectivity characteristics of these structures make them very advantageous when applied to high energy x-ray grazing incidence telescopes. We consider the performance of continuously graded Ni/C multilayers in a multi-focus, Kirkpatrick-Baez geometry and show a significant improvement when compared to standard coatings of gold. For a total length of 3.3 m, a total aperture of 48 cm by 48 cm, and 64 foci, we obtain an effective area of 250 cm² at 60 keV and a FWHM field of view of 6 feet. We also show that a modular array of conical telescopes (conical approximation to a Wolter-I geometry), with the same length and aperture provides similar effective areas. Energy-dispersive x-ray reflectivity data (15 - 70 keV) is presented for the first continuously graded multilayer of this kind.

The problems of maximizing probability of detection (P_D) while minimizing the probability of false alarms (P_F) in the explosives device detection problem for aviation security is addressed for x-ray explosive detection systems (XREDS). Difficulties with currently available detection systems are reviewed. The basic problem lies in the use of single-hit, single-phenomenology sensor systems, where to keep P_F below 10^-4, the equipment threshold V_T for a detection system must be so low that, at the signal-to-noise ratios (S/N) expected, we find that P_D lies between 0.4 and 0.6 regardless of phenomenology or sensor. We examine the choices of signature and discriminant features for XREDS, to achieve high discrimination with few leakers (high P_D) and little asset damage (low P_F). That applies to low signal-to-clutter (S/C) and signal-to-jamming (S/J) ratios. We discuss choices and combinations of x-ray energies, spectral purity, direction of scattering, imaging techniques, and others. Cluster analysis, factor analysis, and principal component analysis are applied to provide effective discrimination between explosive devices and false alarm objects, thereby enhancing P_D while keeping P_F <EQ 10^-4. A key analysis is the incorporation of binary cumulative probability of detection to combine the data from several sensors or signatures and avoid a cumulative increase in P_F (which is caused by a single direct cumulative P_D). We finish with some explicit examples and suggestions for further research into these x-ray methods.

This is a facility report of the J. Bennett Johnston, Sr., Center for Advanced Microstructures and Devices, a new synchrotron-radiation laboratory at Louisiana State University. The accelerator system is described and the radiation characteristics are presented and compared with hypothetical ultra-bright synchrotron sources. The comparison is made to demonstrate the utility of a second-generation `work horse' in the world of the new very-low-emittance machines. In addition to these technical parameters, a brief history of the Center and an overview of the program are presented.