Journal of X-Ray Science and Technology - Volume 7, issue 3-4

Authors: Hintz, Maureen L. | Olsen, Daniel S. | Moody, J. Ward | Madsen, David W.

Article Type: Research Article

Abstract: The GOLDHELOX Project is a student run project to construct a robotic solar telescope that will be used to take images of the sun in the soft X-ray region (171181Å) of the spectrum. The optical system uses a microchannel plate (MCP) detector. We tested the MCP to familiarize ourselves with and verify that MCP's can be used to image soft X-rays. Soft X-rays were created by a Manson source attached to a proportional counter to determine the …amount of emitted X-rays detected by the MCP. The voltages on the MCP were varied to observe responses of varying voltage differences. Most of the observations were visible observations along with images made by a 35 mm camera with a telephoto lens. We found the 1000 V difference to produce the strongest and clearest images. Show more

Citation: Journal of X-Ray Science and Technology, vol. 7, no. 3-4, pp. 211-214, 1997

Authors: Spute, M.K. | Hintz, M.L. | Roming, P.W.A. | Lloyd, T. | Turley, R.S. | Moody, J.W. | Raines, A. | Utley, Jr., T.J. | Eastman, P.F. | Jensen, V.

Article Type: Research Article

Abstract: NASA G-133, also known as the "GoldHelox Project", is a fully autonomous, soft X-ray, solar telescope designed for use on board the space shuttle. Conceived, designed and built by students at Brigham Young University, it will image the sun with a spatial resolution of 2.5 arc-seconds with a temporal resolution of one second. The instrument will image X-rays with wavelengths between 171Å and 181Å coming from highly ionized Fe lines in the sun's corona. Data will …consist of several hundred high resolution photographs that will help in understanding the initial phases of solar flares, and the relationship between solar flares and the physics of the coronal-chromospheric transition region. This paper briefly outlines the project's goals, gives a brief overview of the construction and operation of the instrument and addresses the unique aspects of running a predominantly undergraduate research project. It summarizes the lessons learned to date, and the current project status. Show more

Citation: Journal of X-Ray Science and Technology, vol. 7, no. 3-4, pp. 215-223, 1997

Authors: Mears, C. A. | Frank, M. | Labov, S. E. | Hiller, L. J. | le Grand, J. B. | Chow, D. | Lindeman, M. A. | Netel, H. | Barfknecht, A. T.

Article Type: Research Article

Abstract: We are developing high-resolution, broad-band, superconducting X-ray spectrometers for applications in materials science, astrophysics and biophysics. These spectrometers are superconducting microcalorimeters based on superconducting tunnel junction sensors made from thin films of niobium and aluminum. The energy resolution of these spectrometers can be more than an order of magnitude better than that of the best Si(Li) or Ge(Li) detectors. We present results of recent measurements characterizing the performance of these detectors for …X-ray energies from 70 eV to 500 eV, where the energy resolution ranged from 4 eV FWHM (at 70 eV) to 12 eV FWHM (at 500 eV). Show more

Citation: Journal of X-Ray Science and Technology, vol. 7, no. 3-4, pp. 225-232, 1997

Authors: Kuzin, Sergey V. | Zhitnik, Igor A. | Pertsov, Andrey A. | Slemzin, Vladimir A. | Mitrofanov, Alexander V. | Ignatiev, Alexander P. | Korneev, Vjacheslav V. | Krutov, Viktor V. | Sobelman, Igor I. | Ragozin, Evgeny N. | Thomas, Roger J.

Article Type: Research Article

Abstract: The RES-C grazing incidence XUV spectroheliograph has been developed in the P. N. Lebedev Physical Institute (FIAN) as a part of the CORONAS-I project. Its objective is to obtain images of the full Sun in monochromatic lines over the spectral range of 180210Å, which includes prominent emission from ions of Fe VIIIFe~XIII, O VI, and Fe XXIV. Here, we describe the optical scheme of the spectroheliograph, and show results of XUV testing of its individual component …elements as well as of the complete assembled instrument. XUV measurements were made of the absolute diffraction efficiency and stray-light level for both holographic and mechanically ruled gratings, the spectral reflectivity of the multilayer-coated mirrors, the transmittance of the thin aluminum blocking filters, and the combined spectral efficiency of the whole instrument. The spectral and spatial resolutions of the spectroheliograph were measured by recording spectrally dispersed images of a laser plasma source in monochromatic lines of fluorine ions between 185200Å. For comparison, we also present spectral images of the Sun obtained with the spectroheliograph as flown on the CORONAS-I satellite mission. Show more

Citation: Journal of X-Ray Science and Technology, vol. 7, no. 3-4, pp. 233-247, 1997

Authors: Schühle, Udo

Article Type: Research Article

Abstract: The Solar and Heliospheric Observatory (SOHO) spacecraft was launched on December 2, 1995, into a halo orbit around the first Lagrangian Point L1 between Sun and Earth, carrying into space a payload of twelve Sun observing instruments. Among them is a set of four complementary telescope/spectrometers to study phenomena and dynamics of the Sun's atmosphere in the far or extreme ultraviolet: The Extreme-Ultraviolet Imaging Telescope (EIT), the Coronal Diagnostic Spectrometer (CDS), the Solar Ultraviolet …Measurements of Emitted Radiation (SUMER), and the Ultraviolet Coronagraph Spectrometer (UVCS). The spectral coverage of these instruments, which extents from 151 to 1610Å, allows remote sensing investigations of the solar atmosphere by means of spectroscopic and imaging techniques with a spatial resolution down to 1~arcsec. Each one of these instruments by itself is a technological achievement making use of normal incidence, grazing incidence, or multilayer optical techniques to cover the appropriate spectral ranges for each scientific objective. Many of the plasma diagnostic studies have been carried out during the first months of the mission, and this contribution will give an overview of the capabilities of each instrument and the types of observations being made by individual and joint operations. Show more

Citation: Journal of X-Ray Science and Technology, vol. 7, no. 3-4, pp. 249-255, 1997

Authors: Brytov, I. A. | Dmitriev, G. D. | Ivanov, V. N. | Klevtsov, S. A.

Article Type: Research Article

Abstract: We have studied the possibilities to determine precisely the lattice constants of quartz using an X-ray diffractometer-comparator. This device has double-crystal optical scheme, continuously swinging crystal-monochromator and an original angular reference system. The measurement strategy uses the difference in angular positions of two different Bragg planes relative the third one. On assumption that the wavelength of the used radiation is known with accuracy of ± 1.2,ppm, the accuracy of determined lattice constants is …estimated in ± 5×10-5 Å. The described measurement strategy proves to be efficient in measuring the changes of the lattice constants with temperature and in precision testing of a quartz single-crystal homogeneity. We discuss also the features of other instruments for the automatic sorting of quartz blanks in groups by the cut angle, which use the same monochromator pendulum system. Show more

Citation: Journal of X-Ray Science and Technology, vol. 7, no. 3-4, pp. 257-264, 1997

Authors: Lund, Mark W.

Article Type: Research Article

Abstract: An X-ray lens using refraction has been proposed by Tomie, and demonstrated for 14 keV X-rays by Snigirev et al. This type of lens is made from a series of very weak lens elements. I calculate the properties of such lenses constructed of various chemical elements and compounds over the range of 1 to 30 keV. In general, I find that X-ray optics made from low density, low Z materials have the widest useful apertures, but require more lens elements …than denser and higher Z materials. Show more

Citation: Journal of X-Ray Science and Technology, vol. 7, no. 3-4, pp. 265-270, 1997

Authors: Leguern, F. | André, J-M. | Lebreton, J-P. | Dutrannoy, J-L. | Chauvineau, J-P. | Krastev, K. | Larcade, J-L. | Friart, D. | Nazet, C. | Barchewitz, R.

Article Type: Research Article

Abstract: The damage induced to various multilayer interferential mirrors (MIMs) by intense soft X-ray plasma-laser sources are studied both experimentally and theoretically. The mirrors consist of periodic bilayers made up with C/W, Si/Mo, Si/W\. One set of Si/W MIMs is coated with a 100 nm Si film devised to protect the multilayer structure. In the experiment, one resolves in time the evolution of the diffraction pattern of a MIM illuminated by the radiation of a NaCl probing …laser-plasma and exposed to the heating radiation emitted by a gold laser-plasma. One measures the damage threshold time and the damage threshold fluence. Simulations are performed by combining an optical code with a Lagrangian thermomechanical code giving at each time the density and the thickness of each layer in the MIM. Show more

Citation: Journal of X-Ray Science and Technology, vol. 7, no. 3-4, pp. 271-283, 1997

Authors: Pacherová, Oliva

Article Type: Research Article

Abstract: We tested the X-ray monochromatic single crystal imaging method proposed by Fraenkel and Kalman (B. S. Fraenkel and Z. H. Kalman, Physica Scripta 41, 400 (1990)) on the basis of combined polarization factors. We performed dynamical calculation of the angular distribution of intensity of the imaging reflection. It was verified that the polarization of the incident wave has really a decisive role for an applicability of the method. An integrated intensity procedure was developed for simulating …the conditions during practical imaging. Its applicability is examined in detail for three cases of multiple diffraction with the primary reflection 420 in Ge crystal. Only two cases of the three mentioned showed to be adjustable, producing sufficiently sharp image. A contrast of the image of the adjusted crystal on background level was calculated for those two cases. Show more

Citation: Journal of X-Ray Science and Technology, vol. 7, no. 3-4, pp. 285-293, 1997

Authors: Giakos, G.C. | Vedantham, S. | Pillai, B. | Chowdhury, S. | Sheffer, D.B. | Dasgupta, A. | Endorf, R.J. | Passalaqua, A. | Kollipara, S.

Article Type: Research Article

Abstract: CdZnTe is one of the most promising semiconductor material in the field of digital X-ray imaging, and may be operated at room temperature. To improve the detector characteristics, ternary systems such as Cd1-x Znx Te were grown by the high pressure Bridgman (HPG) technique. The signal performance characteristics of quasi-resistive Cd1-x Znx Te semiconductor detectors, was studied at different directions of irradiation, within the X-ray diagnostic energy range. The experimental results suggest …that the total efficiency of these semiconductor detectors depends upon the energy absorption efficiency as well as the charge collection efficiency. This imaging detector allows one to investigate methods to improve the detection and imaging performance parameters as part of the development of an X-ray imaging system. Show more

Citation: Journal of X-Ray Science and Technology, vol. 7, no. 3-4, pp. 295-304, 1997

Authors: Giakos, G.C. | Pillai, B. | Chowdhury, S. | Vedantham, S. | Dasgupta, A. | Kollipara, S. | Passalaqua, A. | Endorf, R. J.

Article Type: Research Article

Abstract: Radiographic studies with the aim of optimizing the imaging potential of Cd1-x Znx Te detectors for digital chest radiography have been performed. A geometrical chest phantom has been designed, and the dependence of both the signal-to-noise ratio and contrast resolution of a planar Cd1-x Znx Te detector on the phantom thickness has been experimentally determined. Specifically, the detected signal and noise contributions were measured and related to phantom thickness. The results of …this study indicate that Cd1-x Znx Te detectors exhibit both high signal-to-noise ratio and contrast resolution. At present time, several studies are in process to experimentally identify and quantify the imaging potential of Cd1-x Znx Te detectors for digital radiographic applications. Show more

Citation: Journal of X-Ray Science and Technology, vol. 7, no. 3-4, pp. 305-315, 1997

Authors: Giakos, G. C. | Pillai, B. | Chowdhury, S. | Vedantham, S. | Dasgupta, A. | Sheffer, D.B. | Davros, W. J. | Passalaqua, A. | Endorf, R. J.

Article Type: Research Article

Abstract: Experiments have been performed with the aim of optimizing the image quality parameters of CdZnTe detectors for digital mammography. A geometrical breast phantom has been designed, and the dependence of the contrast resolution of a planar CdZnTe detector on the phantom thickness has been experimentally determined. Specifically, the detected signal and noise contributions were measured and related to phantom thickness. The results of this study indicate that the CdZnTe detectors exhibit a high contrast resolution. On …the other hand, the dynamic range of this detector can be improved significantly by further implementation of the data acquisition electronics. Show more

Citation: Journal of X-Ray Science and Technology, vol. 7, no. 3-4, pp. 317-326, 1997

Authors: Linlor, William

Article Type: Research Article

Abstract: A new action constant for bremsstrahlung has been derived and published by the author. This paper provides experimental confirmation of that action constant by measurements of the intensity of bremsstrahlung from pure metal elements. Such measurements must be taken under the condition that essentially all of the kinetic energy of an incident electron is converted into the energy of an emergent photon. The dependence of the intensity on the exponent of the atomic number, Z, of …the target element (measured to be 4/3) shows that the new constant is valid. Show more

Citation: Journal of X-Ray Science and Technology, vol. 7, no. 3-4, pp. 327-330, 1997

Authors: Goel, S. K. | Shanker, R.

Article Type: Research Article

Abstract: The first experimental data are presented for the absolute doubly differential cross section (DDCS) for non-characteristics (bremsstrahlung) X-ray spectra produced by 7.0 keV electron bombardment of (semi-thick) targets of silver and gold at a photon detection angle of 90 degree. The bremsstrahlung spectra are corrected for detector's efficiency as well as for target effects; namely, electron energy loss, backscattering and photon-attenuation in the target. The DDCS values so obtained are compared with the predictions of a …thin target bremsstrahlung theory. The agreement between experiment and theory for DDCS both in magnitude and shape is found to be satisfactory within the systematic experimental uncertainty of about 27%. penetrating electrons into the thick targets and the depth distribution of photons generated inside the targets are expected to be also present in the interaction. However, the contributions of these effects to the DDCS have not been taken into consideration. Various possible reasons for the existing discrepancy between experiment and theory are pointed out. Show more

Citation: Journal of X-Ray Science and Technology, vol. 7, no. 3-4, pp. 331-337, 1997

Authors: Ivanova, E. P. | Knight, L. V.

Article Type: Research Article

Abstract: A Ne-like laser scheme is considered for a pure silver plasma. Level populations and gain coefficients are calculated with an atomic-kinetics model. It is shown that large gain values (GL>100) are achievable in a hot dense quasi-steady-state silver plasma at λ=10.038 nm (2-1 transition) and λ=12.298 nm (0-1 transition). Lasing is also possible at λ=2.75 nm (2s-2p transition). The plasma conditions needed are: electron temperature 35& keV and density 5 × 1022 < ne …< 1023 ;cm-3 ;. These plasma conditions can be created with a high-contrast, high-intensity short-pulse visible light laser driver. Show more

Citation: Journal of X-Ray Science and Technology, vol. 7, no. 3-4, pp. 339-347, 1997