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PIN diode array x-ray imaging. Final Technical report

Description: We have completed constructing an x-ray camera based on a solid state imaging device and have obtained images of Omega laser targets. A Si PIN diode array is used. Objective of this project is to investigate the use of a PIN diode array readout device for obtaining images of 1-20 keV x-ray emission from laser targets. The PIN array detector was successfully used for obtaining hard x-ray images in the high powered laser environment and real time images of the x-ray emission from laser targets.
Date: September 1, 1996
Creator: Jernigan, J.G.
Partner: UNT Libraries Government Documents Department

Public Release of a One Dimensional Version of the Photon Clean Method (PCM1D)

Description: We announce the public release of a one dimensional version of the Photon Clean Method (PCM1D). This code is in the general class of 'inverse Monte Carlo' methods and is specifically designed to interoperate with the public analysis tools available from the Chandra Science Center and the HEASARC. The tool produces models of event based data on a photon by photon basis. The instrument models are based on the standard ARF and RMF fits files. The resulting models have a high number of degrees of freedom of order the number of photons detected providing an alternative analysis compared to the usual method of fitting models with only a few parameters. The original work on this method is described in ADASS 1996 (Jernigan and Vezie).
Date: October 17, 2006
Creator: Carpenter, M H & Jernigan, J G
Partner: UNT Libraries Government Documents Department

Final Report of B548129: Spectral Analysis of Soft X-Ray Data from NSTX

Description: We present a summary of work performed under subcontract B548129 'Spectral Analysis of Soft X-Ray Data from NSTX'. This summary is comprised of papers and poster presentations prepared under this subcontract. The X-ray and Extreme Ultraviolet Spectrometer (XEUS) has been used to monitor the line emission from various impurity ions on NSTX, in particular the K-shell emission of helium-like and hydrogen-like B, C, N, and O. While C VI typically dominates the spectrum, unusually strong emission from N VII has been observed in multiple discharges during the past run campaign. In this case, the nitrogen concentration can exceed that of carbon by an order of magnitude. Time-dependent measurements show that the nitrogen concentration builds up over the course of the discharge and coincides with a build up of boron. In a few cases we observed several unknown lines. These are clearly lines from heavy impurities, possibly molybdenum. Some of these lines can be explained by the emission from Ti XIII.
Date: November 9, 2007
Creator: Lepson, J K; Jernigan, J G & Beiersdorfer, P
Partner: UNT Libraries Government Documents Department

Silicon PIN diode hybrid arrays for charged particle detection: Building blocks for vertex detectors at the SSC

Description: Two-dimensional arrays of solid state detectors have long been used in visible and infrared systems. Hybrid arrays with separately optimized detector and readout substrates have been extensively developed for infrared sensors. The characteristics and use of these infrared readout chips with silicon PIN diode arrays produced by MICRON SEMICONDUCTOR for detecting high-energy particles are reported. Some of these arrays have been produced in formats as large as 512 /times/ 512 pixels; others have been radiation hardened to total dose levels beyond 1 Mrad. Data generation rates of 380 megasamples/second have been achieved. Analog and digital signal transmission and processing techniques have also been developed to accept and reduce these high data rates. 9 refs., 15 figs., 2 tabs.
Date: May 1, 1989
Creator: Kramer, G.; Gaalema, S.; Shapiro, S.L.; Dunwoodie, W.M.; Arens, J.F. & Jernigan, J.G.
Partner: UNT Libraries Government Documents Department

Comparison of observed and theoretical Fe L emission from CIE plasmas

Description: We analyze data from the Lawrence Livermore National Lab (LLNL) Electron Beam Ion Trap (EBIT) that simulates a CIE plasma by sweeping the electron beam to approximate a Maxwellian velocity distribution. These results are compared to spectra of confirmed astronomical CIE plasmas (e.g. outer regions of x-ray clusters) observed by XMM/RGS. We utilize the Photon Clean Method (PCM) to quantify these spectra (EBIT and XMM/RGS) in the form of ratios of Fe L lines in the emission complex near 1 keV. The variances of line fluxes are measured with bootstrap methods (Efron 1979). Both of these observations are further compared with theoretical predictions of Fe L line fluxes from APED and similar atomic databases.
Date: November 8, 2007
Creator: Carpenter, M; Beiersdorfer, P; Brown, G V; Chen, H C; Gu, M F & Jernigan, J G
Partner: UNT Libraries Government Documents Department

Long wavelength infrared camera (LWIRC): a 10 micron camera for the Keck Telescope

Description: The Long Wavelength Infrared Camera (LWIRC) is a facility instrument for the Keck Observatory designed to operate at the f/25 forward Cassegrain focus of the Keck I telescope. The camera operates over the wavelength band 7-13 {micro}m using ZnSe transmissive optics. A set of filters, a circular variable filter (CVF), and a mid-infrared polarizer are available, as are three plate scales: 0.05``, 0.10``, 0.21`` per pixel. The camera focal plane array and optics are cooled using liquid helium. The system has been refurbished with a 128 x 128 pixel Si:As detector array. The electronics readout system used to clock the array is compatible with both the hardware and software of the other Keck infrared instruments NIRC and LWS. A new pre-amplifier/A-D converter has been designed and constructed which decreases greatly the system susceptibility to noise.
Date: May 1, 1998
Creator: Wishnow, E.H.; Danchi, W.C.; Tuthill, P.; Wurtz, R.; Jernigan, J.G. & Arens, J.F.
Partner: UNT Libraries Government Documents Department

Discovery of kHz fluctuations in Centaurus X-3: Evidence for photon bubble oscillations (PBO) and turbulence in a high mass x-ray binary pulsar

Description: The authors report the discovery of kHz fluctuations, including quasi-periodic oscillations (QPO) at {approximately}330 Hz and {approximately}760 Hz and a broadband kHz continuum in the power density spectrum of the high mass X-ray binary pulsar Centaurus X-3 (Jernigan, Klein and Arons 2000). These observations of Cen X-3 were carried out with the Rossi X-ray Timing Explorer (RXTE). The fluctuation spectrum is flat from mHz to a few Hz, then steepens to f{sup {minus}2} behavior between a few Hz and {approximately}100 Hz. Above a hundred Hz, the spectrum shows the QPO features, plus a flat continuum extending to {approximately}1200 Hz and then falling out to {approximately}1800 Hz. Multi-dimensional radiation hydrodynamics simulations of optically thick plasma flow onto a magnetized neutron star show that the fluctuations at frequencies above 100 Hz are the likely consequence of the photon bubble turbulence and oscillations (PBO) previously predicted (Klein et al. 1996) to be observable in this source. The authors show that previous observations of Cen X-3 constrain the models to depend on only one parameter, the size of the polar cap. For a polar cap opening angle of 0.25 radians (polar cap radius {approximately}2.5 km and area {approximately}20 km{sup 2}, for a neutron star radius of 10 km), the authors show that the spectral form above 100 Hz is reproduced by the simulations, including the frequencies of the QPO and the relative power in the QPO and the kHz continuum. This has resulted in the first measurement of the polar cap size of an X-ray pulsar.
Date: September 1, 1999
Creator: Klein, R I; Jernigan, J G & Arons, J
Partner: UNT Libraries Government Documents Department

Atmospheric PSF Interpolation for Weak Lensing in Short Exposure Imaging Data

Description: A main science goal for the Large Synoptic Survey Telescope (LSST) is to measure the cosmic shear signal from weak lensing to extreme accuracy. One difficulty, however, is that with the short exposure time ({approx_equal}15 seconds) proposed, the spatial variation of the Point Spread Function (PSF) shapes may be dominated by the atmosphere, in addition to optics errors. While optics errors mainly cause the PSF to vary on angular scales similar or larger than a single CCD sensor, the atmosphere generates stochastic structures on a wide range of angular scales. It thus becomes a challenge to infer the multi-scale, complex atmospheric PSF patterns by interpolating the sparsely sampled stars in the field. In this paper we present a new method, psfent, for interpolating the PSF shape parameters, based on reconstructing underlying shape parameter maps with a multi-scale maximum entropy algorithm. We demonstrate, using images from the LSST Photon Simulator, the performance of our approach relative to a 5th-order polynomial fit (representing the current standard) and a simple boxcar smoothing technique. Quantitatively, psfent predicts more accurate PSF models in all scenarios and the residual PSF errors are spatially less correlated. This improvement in PSF interpolation leads to a factor of 3.5 lower systematic errors in the shear power spectrum on scales smaller than {approx} 13, compared to polynomial fitting. We estimate that with psfent and for stellar densities greater than {approx_equal}1/arcmin{sup 2}, the spurious shear correlation from PSF interpolation, after combining a complete 10-year dataset from LSST, is lower than the corresponding statistical uncertainties on the cosmic shear power spectrum, even under a conservative scenario.
Date: September 19, 2012
Creator: Chang, C.; Marshall, P.J.; Jernigan, J.G.; Peterson, J.R.; Kahn, S.M.; Gull, S.F. et al.
Partner: UNT Libraries Government Documents Department

Spurious Shear in Weak Lensing with LSST

Description: The complete 10-year survey from the Large Synoptic Survey Telescope (LSST) will image {approx} 20,000 square degrees of sky in six filter bands every few nights, bringing the final survey depth to r {approx} 27.5, with over 4 billion well measured galaxies. To take full advantage of this unprecedented statistical power, the systematic errors associated with weak lensing measurements need to be controlled to a level similar to the statistical errors. This work is the first attempt to quantitatively estimate the absolute level and statistical properties of the systematic errors on weak lensing shear measurements due to the most important physical effects in the LSST system via high fidelity ray-tracing simulations. We identify and isolate the different sources of algorithm-independent, additive systematic errors on shear measurements for LSST and predict their impact on the final cosmic shear measurements using conventional weak lensing analysis techniques. We find that the main source of the errors comes from an inability to adequately characterise the atmospheric point spread function (PSF) due to its high frequency spatial variation on angular scales smaller than {approx} 10{prime} in the single short exposures, which propagates into a spurious shear correlation function at the 10{sup -4}-10{sup -3} level on these scales. With the large multi-epoch dataset that will be acquired by LSST, the stochastic errors average out, bringing the final spurious shear correlation function to a level very close to the statistical errors. Our results imply that the cosmological constraints from LSST will not be severely limited by these algorithm-independent, additive systematic effects.
Date: September 19, 2012
Creator: Chang, C.; Kahn, S.M.; Jernigan, J.G.; Peterson, J.R.; AlSayyad, Y.; Ahmad, Z. et al.
Partner: UNT Libraries Government Documents Department

Development of pixel detectors for SSC vertex tracking

Description: A description of hybrid PIN diode arrays and a readout architecture for their use as a vertex detector in the SSC environment is presented. Test results obtained with arrays having 256 {times} 256 pixels, each 30 {mu}m square, are also presented. The development of a custom readout for the SSC will be discussed, which supports a mechanism for time stamping hit pixels, storing their xy coordinates, and storing the analog information within the pixel. The peripheral logic located on the array, permits the selection of those pixels containing interesting data and their coordinates to be selectively read out. This same logic also resolves ambiguous pixel ghost locations and controls the pixel neighbor read out necessary to achieve high spatial resolution. The thermal design of the vertex tracker and the proposed signal processing architecture will also be discussed. 5 refs., 13 figs., 3 tabs.
Date: April 1, 1991
Creator: Kramer, G. (Hughes Aircraft Co., El Segundo, CA (USA). Electro-Optical and Data Systems Group); Atlas, E.L.; Augustine, F.; Barken, O.; Collins, T.; Marking, W.L. et al.
Partner: UNT Libraries Government Documents Department