Showing papers by "Gordon P. Garmire published in 1993"
TL;DR: In this article, the authors present soft X-ray, N(H) and IR maps of the Eridanus soft Xray enhancement, which shows that the enhancement consists of two distinct components: a large hook-shaped component and a small circular component at different temperatures.
Abstract: We present soft X-ray, N(H), and IR maps of the Eridanus soft X-ray enhancement. Soft X-ray maps from the HEAO 1 A-2 LED experiment, processed with a maximum entropy method (MEM) algorithm, show that the enhancement consists of two distinct components: a large hook-shaped component and a small circular component at different temperatures. Both of these are located in 'holes' in the IR emission, and they correspond to N(H) features at very different velocities. The dust surrounding the X-ray enhancements appears to be associated with several high-latitude molecular clouds, which allow us to obtain a probable distance of about 130 pc to the near edge of the main enhancement. The total power emitted by the hot gas is then about 10 exp 35 to 10 exp 36 ergs/s. We consider alternative interpretations of these objects as adiabatic supernova remnants or as stellar wind bubbles and conclude that they are more likely to be stellar wind bubbles, possibly reheated by a SN explosion in the case of the main, hook-shaped object.
102 citations
19 Nov 1993
TL;DR: The recent restructuring of the AXAF program has necessitated a review of the design of the ACIS instrument as discussed by the authors, and the current status of these design activities is reported in this paper, focusing on changes to the baseline CCD and its impact on aspects such as the operating modes.
Abstract: The recent restructuring of the AXAF program has necessitated a review of the design of the ACIS instrument. In this paper we report on the current status of these design activities. We concentrate on changes to the baseline CCD and its impact on aspects such as the operating modes. Also we review changes to the mechanical design with respect to the passive cooling scheme facilitated by the change to a highly eccentric deep earth orbit.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
6 citations
TL;DR: In this paper, the effects of radiation damage in low Earth orbit in order to predict CCD lifetimes over which good charge transfer is maintained is presented. But the model presented here considers damage mechanisms within the CCD, environmental conditions in which the CCS operates, and experiment shielding.
Abstract: The first generation of X-ray telescopes to use Charge-Coupled Devices (CCDs) is being launched this decade. With a read noise of a few electrons, CCDs provide Fano-limited spectral resolution across the soft X-ray band (0.1 – 10 keV). However, degradation of resolution due to charge transfer losses becomes noticeable as Charge Transfer Inefficiency (CTI) increases to 10−5. In this paper, we present a model which calculates the effects of radiation damage in low Earth orbit in order to predict CCD lifetimes over which good charge transfer is maintained. The model presented here considers damage mechanisms within the CCD, environmental conditions in which the CCD operates, and experiment shielding. We find that the predicted CTI approaches 10−5 after a one to two year mission for the flight instruments considered here.
3 citations
19 Nov 1993
TL;DR: The CUBIC CCDs as mentioned in this paper use a thin poly gate structure designed to maximize low energy quantum efficiency, while still retaining the advantages of front-side illumination and the high charge transfer efficiency of a three-phase device.
Abstract: CUBIC, the Cosmic Unresolved X-ray Background Instrument Using CCDs, is designed to make moderate resolution X-ray spectral measurements at spatial scales of a few degrees. While the energy range is nominally 200 eV - 10 keV, the CCDs have been designed to maximize the soft X-ray performance by using novel structures. The CUBIC CCDs, fabricated by Loral Fairchild, are 1024 X 1024 pixels in size, with 18 micrometers X 18 micrometers pixels. The CCDs use a new `thin poly' gate structure designed to maximize low energy quantum efficiency, while still retaining the advantages of front-side illumination and the high Charge Transfer Efficiency of a three-phase device. Being front-side illuminated, the design avoids the surface stability problems of backside illuminated devices. Fabrication of the first lot of CCDs and test structures has been completed, and we report laboratory camera testing of the CCDs at Penn State.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
2 citations