High-energy X-ray Source Research Articles

Short pulse, x-ray preionization of a high pressure XeCl gas discharge laser

A short pulse (35 ns), high energy X-ray source, driven by a coaxial Blumlein pulser, has been used to preionize a 2.5 × 3 × 30 cm 3 active volume XeCl avalanche discharge laser. A maximum output energy of 1 J has been extracted at 0.9% efficiency (including X-ray preionization). Measurements have been performed to investigate the influence of the X-ray pulse timing on laser output and discharge quality.

Balloon observations of galactic high-energy X-ray sources

view Abstract Citations (36) References (29) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Balloon observations of galactic high-energy X-ray sources. Maurer, G. S. ; Johnson, W. N. ; Kurfess, J. D. ; Strickman, M. S. Abstract A number of X-ray sources were observed with the Naval Research Laboratory hard X-ray observatory during balloon flights on 1976 May 11 and 1977 November 24. The primary objective of the observations was to characterize the temporal and spectral behavior of the sources in the energy range from 20 to 250 keV. Special emphasis was placed on the determination of spectrum versus phase for periodic sources and on the search for spectral features such as the reported 60 keV line in the X-ray spectrum of Her X-1. Results of the observations include: evidence for possible phase-dependent spectral variations in the emission from GX 1+4; flaring in the emission from GX 301-2; detection of unmodulated X-ray emission up to approximately 35 keV from GX 304-1; and an unexpectedly hard spectrum above 20 keV from Cyg X-2. Publication: The Astrophysical Journal Pub Date: March 1982 DOI: 10.1086/159730 Bibcode: 1982ApJ...254..271M Keywords: Balloon-Borne Instruments; Binary Stars; Light Curve; Spectrum Analysis; X Ray Sources; X Ray Spectra; Cosmic X Rays; Photon Density; Power Spectra; Pulsars; Pulsed Radiation; Scintillation Counters; Thermal Radiation; Astronomy full text sources ADS | data products SIMBAD (5)

Effects of gamma-ray, neutrino, and particle production on the energetics and dynamics of compact extragalactic radio sources

Consideration is given to particle production and high-energy radiation within apparently superluminal radio components of extragalactic radio sources forming within the apparent region of nuclear activity of a quasar or active galaxy. The physical conditions in compact components observed as radio emitters are derived for the quasars 3C 273 and 3C 345 and extrapolated to those of initial components of sizes on the order of 10 to the 15th cm on the basis of two-dimensional relativistic jet and relativistic three-dimensional models of component expansion. Probabilities that a given particle avoids an inelastic collision in the relativistic plasma are calculated for both cases which show that collisions which produce particles and radiation may be very important during the formation of a compact radio component. The consequences of electron-positron production, bremsstrahlung and proton-proton inelastic collisions ultimately giving rise to neutrinos and gamma rays for the development and energetics of the radio component are then examined, and upper limits to the amount of energy which can be channeled into radio components from an active region without giving rise to a high-energy X-ray source are derived.

CHESS: The New Synchrotron Radiation Facility at Cornell

A new synchrotron radiation laboratory, CHESS, will soon be completed at Cornell University. The facility will operate in a mode parasitic to high energy physics experiments on the new 8-billion-electron-volt electron-positron storage ring (CESR) at Cornell. Electron and positron beams have already been stored and the first photons have been extracted. When completed, the laboratory will be available to the scientific community nationally and will provide the most intense tunable source of high energy x-rays in the country.

Intensity transitions in Cyg XR-1 observed at high energies from OSO 8

THE high energy X-ray source, Cygnus XR-1, exhibits a variable intensity between states which differ in flux at lower energies (typically 3 to 6 keV) by a factor of three (refs 1–5). Although the transitions between these ‘high’ and ‘low’ flux states occur at irregular intervals, the transition itself usually takes no more than one day in either direction. We report here an observation of such a transition at energies above 20 keV which shows that the spectrum of Cyg XR-1 exhibits the pivoting effect during intensity transitions expected from two-temperature accretion disk models of the X-ray emitting region6,7.

Pulsed high intensity monoenergetic low energy X-ray source and absolute X-ray monitor

An X-ray source of 1.5, 4.5, or 8.0 keV with 10 ns durations has been produced utilizing a pulsed electron source to excite the characteristic K-line radiation of elemental targets. A parallel plate ionization chamber was calibrated in the NBS standard monoenergetic K X-ray beams and used with Ross filters to measure the pulsed source K X-ray fluence. Typical measured peak X-ray flux intensities are 10 18−10 19 K X-rays per sr per s. The pulsed source contains four identical ports for simultaneous measurements of the K X-ray intensity by the ionization chamber and detectors being calibrated. The pulsed K X-ray source and the NBS standard steady state K X-ray source, which differ in intensity by 10 orders of magnitude, have been utilized to determine the responses of a photoelectric diode, a scintillator-vacuum photodiode combination, and a silicon PIN diode.

Radiation treatment planning

Radiation treatment planning has developed into a substantial and effective component of the entire radiation treatment approach. Over the last 2 decades, with the development of high energy electron and x-ray sources, and also with the availability of new radionuclides and techniques for internally applied radiation, all of which permit a high degree of concentration of radiation, treatment planning has been developed to make best use of these modalities. The use of automatic computation has proved necessary in order to handle the large amounts of radiation data involved in treatment dose calculation. Tumor and anatomical localization has been carried out with increasing precision. Several cases are described which illustrate planning and in particular the use of computerized transverse tomography. The use of moving shadow-shields is also described. For internally applied radiation, the features of iodine-125 are illustrated.

Hard X-rays from Coma Constellation

THE region of the sky defined by RA=190° to 330° and δ= –20° to +50° has been scanned for high energy X-ray sources in a series of five balloon flights carried out from Hyderabad since April 1968 using oriented X-ray telescopes1–3. The sky map of hard X-ray intensity in the energy range 20 to 150 keV obtained from these flights is plotted in celestial coordinates in Fig. 1. Each circle in the figure represents one observation on a part of the sky in which the telescope axis passed through a celestial bin 10° × 10°/cos δ enveloping the circle. The different observations correspond to those made either at different times in the same flight or in different flights on different dates. The size of the circle represents the number of standard deviations σ by which the counting rate of the telescope is either greater than (filled circles) or less than (open circles) the background counting rate for that particular flight. The legend by the side of the figure gives the relation between the size of the circle and the σ value. Only those points for which the observation time was in excess of 40 s have been included in the plot; the positions of known X-ray sources are indicated by star symbols. The dotted circle represents the typical field of view of the telescope which corresponded to an FWHM of 18.5° in some flights-the circle slightly distorts into an ellipse for higher declinations. In other flights the field of view was 12°. The clustering of large diameter filled circles (high σ values) in the regions of known sources like Sco X-1, Cyg X-1 and GX 9+9 is clearly evident. There are two other regions, one enclosed by RA=200° to 225° and δ = +10° to −10° and another by RA= 195° to 215° and δ=25° to 50°, which also show significant clustering of high positive σ values. Details of the first region, which falls in the Virgo constellation, have been presented elsewhere3 together with results for the various known sources. We wish to present here the results for the second region of enhancement, which falls in the Coma constellation. This part of the sky was scanned on April 16, 1969 and May 5, 1970 and the evidence for enhanced emission has come from these two flights. The plots of the counting rates in celestial coordinates from these two flights for the relevant periods of observation are given in Figs. 2 and 3. (Complete azimuthal plots and celestial plots for the period of observation are available in the thesis of R. K. Manchanda, submitted to Bombay University.)

Basic radiography 11-dense metal castings

The author describes the preparation of the specimen; factors influencing its radiographic coverage; angles of view; number of aspects and exposures required; the selection of exposure conditions; double film techniques; the control of radiograph quality; and factors influencing the preparation of radiological techniques. He concludes with a brief summary of the place of high energy x-ray sources and multi-curie sources.

Angular Size of the High Energy X-ray Source in the Crab Nebula

THIS article reports new data on the spatial structure of the source of 25 to 100 keV X-rays in the Crab nebula, obtained with a balloon-borne X-ray modulation collimator. The angular diameter of the Crab for energies of 1.2 to 12 keV has been measured previously in two rocket experiments by lunar occultation1 and by modulation collimator2. Both measurements showed that the low energy X-rays come from an extended region one to two arc minutes in diameter centred on the visible nebula. Since then the radio3 and optical4 pulsar NP 0532 has been identified with a central star in the nebula5.

Balloon Observations of High Energy X-ray Sources in the Region of the Galactic Centre

IN an eight-hour balloon flight launched from Mildura, Australia, on October 15, 1967, we surveyed the X-ray emission above 20 keV from the region of the sky from declinations −70° to −5° and from right ascensions 150° to 280° (angular resolution 13° f.w.h.m.). We noted earlier1 that the data showed several sources in a region near the galactic centre. From a more detailed analysis of the data from this region we can now account for the bulk of the hard X-rays we observed in terms of four sources whose positions and spectra we report here.

Observation of CEN XR-2 and Other High-Energy X-Ray Sources in the Southern Sky

Observation of CEN XR-2 and Other High-Energy X-Ray Sources in the Southern Sky