Recently a number of gas-filled detectors based on multiwire proportional chambers have been successfully applied to imaging systems with x rays from generators or synchrotron radiation sources and (gamma) rays for medical scientific or industrial applications. The good position resolution, the high rate capability, the intrinsic digital recording in the single photon counting mode, and the large size make them interesting candidates for a number of applications that are discussed. Furthermore, these detectors allow the recording and processing of more complex information. This is demonstrated by an imaging single quantum counting detector with scatter rejection for gamma rays resulting in high contrast and position resolution and an x-ray detector using the pulse height measurement for dual energy tomography for composite material investigation. Future developments including micro strip gas detectors are discussed.

We have constructed a modular detector for x-ray crystallography and made preliminary performance measurements. A single detector module consists of a large-area (100 X 100 mm square) fiberoptic taper with a phosphor x-ray converter deposited on the large end and a back-illuminated MPP-mode CCD bonded to the small end. Two or more of these modules can be used together to increase the detector area. The CCD can be operated at -55 degree(s)C when cooled with a two-stage thermo-electric cooler in a 1 atmosphere Xenon-filled chamber. The CCD readout noise is 9e^- when read out at a rate of 100 kpixels/second.

This paper presents a new structure of a 2-D imaging system devoted to radiology. The detection upper medium, made with bulk cadmium telluride, is connected to the electronic 2D readout circuit through indium bumps. The 60 X 60 micrometers ² electrodes, 100 micrometers pitch, are made on the CdTe:Cl detector with standard lithography and ion etching techniques. The silicon circuit is made of n X n independent integrated amplifiers with serial multiplexing readout. The feasibility of such arrangement is made with 64 X 64 pixels. The thickness of 900 micrometers is well suited for 100 keV x rays. Characterization is performed with 10 ms x-ray pulses. Due to electric field the charges are well channelled and high spatial resolution is available in addition with a very high absorption efficiency. The direct absorption of x ray in the readout circuit is negligible. It does not affect either the signal to noise ratio, or the lifetime of the silicon low level analogue ASIC. The presentation includes linearity, sensitivity, noise FTM, and dynamic image discussion.

A position-sensitive 1D x-ray detector with large dynamic range (> 2¹⁴:1) for high photon fluxes with fast image recording sequence has been developed for noninvasive subtraction coronary angiography. Detailed investigations of the basic physical processes in the detector allow the quantitative description of the important detector performance parameters. As an example a detector with a position resolution of 430 micrometers FWHM and a detective quantum efficiency (DQE) of at least 58% (for 20,000 photons/pixel) for 33 keV photons in a XeCO₂ gas mixture at 20 bars is described. A procedure has been developed for determination of the DQE from the data. Investigations at high beam intensities showed that only at a flux above 2.4 10¹⁰ photons/s pixel saturation effects become apparent. These observations are quantitatively explained by a newly developed dynamic ion chamber model. Recently a number of noninvasive angiographies from patients of diagnostic quality were obtained at HASYLAB, DESY.

A study concerning the use of a 1 cm² p-i-n (alpha) -Si:H structure coupled to a 1 cm³ CsI(Tl) scintillator is presented and discussed as a survey meter in the range from 20 to 125 keV x ray peak energy. A particular mesa etch, coupled with standard photolithography, lowers dark current in the pA region, allowing the use of the detector in the photovoltaic mode. In this work, we describe the details of detector fabrication, the various steps of detector simulation in order to look for detector performance improvements, and the different stages of detector testing in the reported energy range. For each energy, the linearity of the detector response as a function of the dose rate has been accurately measured and compared with standard ionization chambers of different volumes. Finally, the effective energy reconstruction and the instrument calibration is presented and discussed. Wearing-on applications, similar to film badges, are envisaged and possible solutions are introduced and discussed.

We have fabricated several monolithic x-ray detector arrays from Cd_0.9Zn_0.1Te material. The principle advantages of this material are its relatively high stopping power and room temperature operation. Recently fabricated linear arrays exhibit improved spatial and energy resolution as compared to our previous versions. Each array is 25.3 mm long with 32 independent detector elements, yielding a center-to-center spacing of 0.8 mm. Gaps of less than 100 micrometers , but with greater than 2 gigaohms of resistance, separate the pixel contacts. Our results indicate that smaller spacings and gap widths are possible with our current fabrication methods. The arrays have been operated in a pulse counting mode with photon energy discrimination. Results for energy resolution and spatial response are presented. Examples of low dose x ray transmission images obtained with a prototype linear scanner utilizing multiple arrays are shown here. By using the energy discrimination capability of the arrays and electronic readout, we have also been able to generate dual-energy images of various samples.

X-ray inspection systems have been used on airports for many years to check luggage in order to detect weapons and similar objects. In the meantime the requirements changed and the technology was improved concerning the detection of explosives. Even the requirement of automatic operation can be met. A step-by-step arrangement is described, consisting of two advanced devices: stage one is a new x ray luggage inspection system sensitive to the presence of explosives and other suspicious items, which also copes with the requirement of a high throughput; the second stage is based on x-ray diffraction and provides complementary information on the objects, thus ensuring high quality decisions.

Experimental measurements were made for the w-value for 5.9 keV x rays in pure argon, argon with 4% xenon, argon with 21% xenon, and pure xenon at pressures just above the atmospheric. The values obtained are 26.2 eV +/- 0.7 eV, 22.0 eV +/- 0.9 eV, 21.4 +/- 0.9 eV, and 21.7 eV +/- 0.5 eV, respectively. The importance of the 96% argon - 4% xenon mixture in gas proportional scintillation counters for the detection of soft x rays with reduced spectral distortion is discussed.

Siemens' ability to take the Vanguard^TM Industrial Linear Accelerator from the development stage to the market place in less than two years is described. Emphasis is on the development process, from the business plan through the shipment of the first commercial sale. Included are discussions on the evolution of the marketing specifications, with emphasis on imaging system requirements, as well as flexibility for expansion into other markets. Requirements used to create the engineering specifications, how they were incorporated into the design, and lessons learned from the demonstration system are covered. Some real-life examples of unanticipated problems are presented, as well as how they were resolved, including some discussion of the special problems encountered in developing a user interface and a training program for an international customer.

The detection and temporal dispersion of the x rays using x ray streak cameras has been limited to a resolution of 2 ps, primarily due to the transit time dispersion of the electrons between the photocathode and the acceleration grid. The transit time spread of the electrons traveling from the photocathode to the acceleration grid is inversely proportional to the accelerating field. By increasing the field by a factor of 7, we have minimized the effects of transit time dispersion in the photocathode/accelerating grid region and produce an x-ray streak camera with sub-picosecond temporal resolution (approximately equals 900 fs). The streak camera has been calibrated using a Michelson interferometer and 100 fs, 400 nm laser light. Time resolved x-ray data is shown from an aluminum target heated at 10¹⁸ W/cm² with a 100 fs, 400 nm laser.

The performance of a pair of thinned back-illuminated ion-implanted and laser annealed CCDs have been evaluated in the EUV spectral region. Both the devices have been manufactured by EEV and one of them was also treated with the new technique of anodic etching to improve its quantum efficiency. The measurements performed consist mainly of the determination of the CCD quantum efficiency in the 300 - 2500 angstrom region. These tests have been performed by means of a new vacuum test facility and a new CCd controller realized in our laboratories which is interfaced with a PC; moreover, to have a low noise, both the CCDs have worked in a slow scan mode and have been cryogenically cooled. The results show that a CCD quantum efficiency decreasing during the tests is present, but demonstrate also that these devices can have a lot of capabilities as EUV detectors.

An efficient photostimulated luminescence (PSL) with a peak at about 420 nm is observed by stimulating ultra-violet (UV)-ray-irradiated europium-doped potassium chloride (KCl:Eu) crystalline phosphor with 560 - 580 nm light. The excitation and emission mechanism for the 420 nm PSL in UV-ray irradiated KCl:Eu phosphors are proposed. It is found that the PSL intensity increased with increasing irradiation dose of UV-ray, which indicating that the KCl:Eu is one of the most attractive candidates for two-dimensional UV-ray imaging sensor utilizing PSL phenomenon.

Photoionization of excited states is the mechanism of detection in gas tube UV photon counting detectors of high sensitivity and variable spectral response. Because of bias to the prebreakdown region, noise current is on the order of only 10^-14 A(DOT)Hz^-1/2. Spectral response varies according to gas quantum structure and pressure. High gas pressures shift spectral response to shorter wavelengths while lower pressures shift it to longer wavelengths and broaden it. One detector version is therefore almost solar blind. Another exhibits almost flat spectral response over most of the near UV band. In all cases, response falls off strongly with increasing wavelengths at longer UV wavelengths. Picowatt UV radiant powers yield about 1000 counts per minute. Response gamma is fairly constant up towards the microwatt radiant power range before falling off.

A 75 mm diameter microchannel plate (MCP) intensifier has been developed for astronomical applications. The intensifier incorporates a semi-transparent photocathode, three MCPs in a Z- stack configuration, and a P20 phosphor screen in a dual proximity focused arrangement. The input MCP is a thin 40:1 channel plate which is conditioned to run at low gain and hence act as an ion barrier for the succeeding 80:1 chevron pair. The intensifier has been incorporated into a CCD readout system and has undergone extensive laboratory testing. The preconditioning of these 75 mm diameter channel plates required a large area, highly uniform electron scrub beam, this has led to the development of a novel electron gun. The design of the 75 mm intensifier and the novel electron gun are described. Results from the laboratory evaluation of the intensifier are presented. Flat field illumination showed the existence of self- exciting channels in a hexagonal pattern. Finally, a future UV or x-ray detector based on this design and incorporating large area MCPs is discussed.

MAMA detector systems are under development for flight in the high-resolution EUV spectroheliometer sounding rocket instrument and in the NASA Goddard Space Flight Center's Hubble space telescope imaging spectrograph. Visible-light versions of the detector systems are also being evaluated at ground-based telescopes in a number of programs of speckle interferometry and speckle image reconstruction. In this paper the performance characteristics of the latest versions of the MAMA detector systems are summarized and the prospects for further significant improvements to the MAMA detector systems are outlined.

One of the most attractive and potentially useful applications of capillary optics for x rays is conversion of divergent x rays from intense point sources into quasi parallel beams for diffraction applications. This is particularly important for investigation of small samples such as protein crystals. This report reviews the current status of development of monolithic tapered Kumakhov optics for protein structure analysis. Even at this early stage of development, gains of more than 30 compared to optimized systems without the optics have been achieved.

The Center for X-Ray Optics at the University at Albany, New York founded to pursue the development of capillary x-ray and neutron optics, has grown rapidly since its establishment less than four years ago. Quantitative characterization of these optics from 1 keV to 45 keV was reported here in 1993. In this report, a summary of the current status of this effort is described in the context of activities at the Center for X-Ray Optics.

Differential formalism gives a rapid convergence of accurate results even under conditions of propagation of several hundred spectral orders and grazing angles of incidence for the gratings with low groove-depth-to-groove-spacing ratio (h/d << 1) which are typical for this wavelength region. In the same way it was found that the rigorous results on the region of low (delta) /d ratios under the short time of computation may also be done through the modified integral method. By way of the programs created on the base of integral equations, the results done through the differential method were repeated and a good coincidence with them was found. These data allow us to speak about the equivalence of both methods -- integral and differential -- and about the convergence of algorithms.

It was found that grating efficiency in short spectral range has unpredictable changes both under the alterations in groove geometry, groove frequency, angle of incidence and wavelength; and under replacement of reflectance, i.e. under the use of another coating material with the stand point of scalar theory. As is shown, this non-scalar effect becomes greatly apparent only for high-frequency gratings (up to 3600 g/mm) and includes two aspects. They are: (1) it is impossible to predict grating efficiency under the changing of coating material (without changes of all the other parameters) by multiplication on the ratio of coating material Fresnel reflectance; (2) optimum parameters (angle of incidence, groove depth, groove width for lamellar grating) found for one kind of coating material are not optimum for another.

Existence of interference structures at the focal spot of regular x-ray capillary lenses and poles is discovered experimentally by our group. This effect was investigated by means of synchrotron and x-ray tube. We point out the possibility of use for capillaries twisting for control of polarizable characteristics, e.g., for rotation of a polarization plane of x ray, neutron radiation, etc. The possibility of radiation monochromatization on the level (lambda) /(Delta) (lambda) approximately equals 10³ by means of a lens is also shown. Features of image transfer using interference effects in capillary structures were investigated. General wave theory of these effects is proposed. A number of important applications based on the higher illumination of x-ray lenses as compared with zone plates are considered.

Results of experiments on focusing of synchrotron radiation by means of Kumakhov lens are presented. For explanation of observed interference structure the wave theory describing channeling radiation is applied.

New optics widely uses the possibility of controlling x rays during their transmission through systems of bent hollow glass capillaries. One of the main elements of new optics are concentrating devices which got the name `Kumakhov lenses.' Different types of Kumakhov lenses can be used for solving various problems: focusing radiation onto a small spot, forming quasiparallel beams, filtering radiation, reducing or increasing x-ray images, etc. The possibility of controlling x rays is based on the phenomenon of total external reflection which takes place only at grazing incidence angles. But Kumakhov lenses have large angular aperture because they operate on multiple reflections. In this work we investigate the properties of Kumakhov lenses operating on multiple reflections as well as more simple capillary systems which can also focus x rays but operate mainly on single reflections. The latter systems are capillary structures which have straight hollow mutually parallel channels.

The results of experimental investigations of image transfer by means of capillary optics elements are presented. The problems connected with designing elements that allow turning of the image and the possibilities of using an interference effect on image transfer are discussed.

A focus spot structure and form under focusing of the x-ray radiation in the 7 - 10 keV energy range by Kumakhov lenses were investigated. It is shown that following a focusing the radiation concentration abruptly increased. For the first time the interference structure of a focus spot came to light. Possibilities of Kumakhov lenses used as an analyzer with high spectral resolution and as a point source of x-ray radiation are discussed.

An x-ray lens designed to collimate x rays from a divergent source has been characterized. The lens is 10 cm long and consists of 919 polycapillary fibers. The diameter of each fiber is 400 microns with a channel size of 15 microns. The solid angle of collection of the lens is 40 msterad. The focal distance of the lens is 57 mm. The transmission and divergence properties of the lens are discussed for different x-ray energies and source conditions.

A large area, high resolution detector containing microchannel plates (MCPs) and a helical wire wound delay line anode is currently being fabricated. We describe the performance of another recently constructed device with a similar design, and discuss design modifications which will result in improved performance from the current detector. In particular, we describe a modified delay line anode designed to read out the same size MCPs (100 mm X 100 mm) as in the earlier tube, but with more compact size, lower attenuation, and less dispersion. Results are presented of measurements of pulse risetimes and attenuation, and of anode geometric linearity and resolution as a function of MCP charge.

We have developed two sources of high flux radiation: one, designated as SPX II, exploits the principle of spherical convergence of a strong shock wave in a noble gas to generate a plasma at the center of a sphere hot enough to emit broadband radiation from the UV to the soft x-ray region of the spectrum; the other is based on the principle of vacuum spark, whereby accelerated electrons in a strong electric field in vacuum bombard an aluminum anode surface, leading to K-alpha line emission (1.7 keV). Typical measured outputs from the SPX II are: 186 W in the visible range (3500 - 2800 angstrom); 754 W in the UV range (2800 - 1800 angstrom); 650 W in the deep UV (1800 - 600 angstrom), and 5 W in the soft x ray (15 - 10 angstrom) for an operating repetition rate of the machine of 1 Hz. Typical measured output from the vacuum spark source is 30 W in the K-alpha line (7 angstrom) for a few kilowatt machine. The above are all powers measured beyond the pertinent filter used to select the radiation of interest, such as beryllium, aluminum, or other filters.

The ratio method, in which the elastic x-ray scatter signal I_e from a localized region of bulk material is normalized against the Compton scatter I_c, has been widely evaluated as a densitometric technique for evaluating mean atomic number. An analysis is presented of two major error sources influencing the ratio method. It is shown that a forward scattering geometry minimizes errors of both types for substances composed of low and medium Z elements. We describe a novel technique in which a K edge filter is used to separate small angle elastic and Compton scatter induced in a sample on irradiation with the FLUOREX fluorescent x-ray source. The feasibility of this method is demonstrated by first experimental results. The potential application of this technique to the problem of explosives detection is briefly discussed.

Thin, backside-illuminated CCDs are modified by growing a delta-doped silicon layer on the back surface using molecular beam epitaxy. Delta-doped CCDs exhibit stable and uniform 100% internal quantum efficiency. The process consists of growth of an epitaxial silicon layer on a fully processed commercial CCD die in which 30% of a monolayer of boron atoms are incorporated into the lattice nominally in a single atomic layer. Long term stability was tested and showed no degradation of the device quantum efficiency over sixteen months. Reduction of the reflectivity of the Si surface by deposition of HfO₂ on the CCD back surface further increased the QE, with measured QE over 80% in some regions of the spectrum. We discuss these results as well as the delta-doped CCD concept and process.