Details of the design, fabrication, and ground and flight calibration of the High Energy Transmission Grating (HETG) on the Chandra X‐Ray Observatory are presented after 5 years of flight experience. Specifics include the theory of phased transmission gratings as applied to the HETG, the Rowland design of the spectrometer, details of the grating fabrication techniques, and the results of ground testing and calibration of the HETG. For nearly 6 years the HETG has operated essentially as designed, although it has presented some subtle flight calibration effects.

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The Chandra High-Energy Transmission Grating: Design, Fabrication, Ground Calibration, and 5 Years in Flight

We present a catalogue of low-mass X-ray binaries. The catalogue is an updated version of the catalogue of van Paradijs (1995). This new catalogue contains 150 sources, 31 new low-mass X-ray binaries in addition to the 119 sources listed in van Paradijs' catalogue. The aim of this catalogue is to help the reader gain easy access to the recent literature (up to about August 2000) on individual sources, and to provide of some basic information on the X-ray sources and their counterparts in other wavelength ranges (UV, optical, IR, and radio). In cases where there is some doubt about the low-mass nature of the X-ray binary, this is mentioned. In an appendix we list the Anomalous X-ray Pulsars (AXPs), which nowadays are no longer thought to be low-mass X-ray binaries.

/pdf/a-catalogue-of-low-mass-x-ray-binaries-tb6g9n68ps.pdf

A catalogue of low-mass X-ray binaries

United States. National Aeronautics and Space Administration. George C. Marshall Space Flight Center (Contract NAS8-38249)

The Chandra High Energy Transmission Grating: Design, Fabrication, Ground Calibration and Five Years in Flight

Experimental techniques and instrumentation for space plasma imaging in fluxes of energetic neutral atoms (ENAs) are reviewed. ENAs are born in charge exchange collisions between space plasma energetic ions and background neutral gas. ENAs are ubiquitous in the space environment and their energies are in the range from a few eV up to >100 keV. Contrary to charged particles, ENAs can travel large distances through space with minimal disturbance, and by recording ENA fluxes as a function of observational direction, one can reconstruct a global image of a planetary magnetosphere or the heliosphere. Plasma ion energy distribution and ion composition can be remotely established by measuring ENA energies and masses. ENA imaging opens a new window on various phenomena in space plasmas with a promise to qualitatively improve our understanding of global magnetospheric and heliospheric processes. At first we review ENA fluxes in space and their properties, and present a brief history of ENA experimental studies and...

Energetic neutral atom imaging of space plasmas

We report a simple but efficient nanofabrication method to create a dense (nanoscale pitch) array of silicon nanostructures (post and grate) of varying height and shape over a large sample area. By coupling interference lithography with deep reactive ion etching (DRIE) in one process flow, we?achieved silicon nanostructures of excellent regularity, currently with a pitch (i.e., period) of 230?nm, and uniform coverage, currently over 2 ? 2?cm2. The new nanofabrication practice of coupling interference lithography with DRIE not only simplified the nanofabrication process but also produced high-aspect-ratio (higher than 10) nanostructures. By regulating etching parameters, the nanoscopic scalloping problem typical in Bosch DRIE was not only controlled but also utilized to realize sophisticated sidewall profiles, such as tips with a pointed or a re-entrant profile. We showed the tips could be further sharpened by thermal oxidation and subsequent removal of the oxide. Well-defined nanostructures over a large area with controllable sidewall profiles and tip shapes open new application possibilities in areas beyond nanoelectronics, such as microfluidics and tissue engineering.

https://iopscience.iop.org/article/10.1088/0957-4484/17/21/007/pdf

Fabrication of a dense array of tall nanostructures over a large sample area with sidewall profile and tip sharpness control

The use of transmission gratings with grazing-incidence telescopes in celestial x-ray astronomy is reviewed. The basic properties of transmission grating spectrometers and the use of "phased" gratings to enhance the diffraction efficiency are outlined. Special attention is given to the AXAF high-energy transmission grating (HETG) being fabricated at MIT. The HETG operates over the range 0.4 to 8 keV, gives resolving powers of 100 to 1000, effective areas of 10 to 300 cm2, and a minimum detectable line flux of 1 to 10 x 10-6 photons cm-2 s-1. The instrument consists of a single array with two types of membrane-supported grating facets: medium-energy gratings (0.6-μm period, 0.5-μm-thick silver) mounted behind the outer three AXAF mirrors, and high-energy gratings (0.2-μm period, 1.0-μm-thick gold) mounted behind the inner three mirrors. The materials and thicknesses are selected to maximize efficiency throughout the energy band. The facets are fabricated at MIT using a process involving x-ray lithography. AXAF will also carry a low-energy transmission grating (LETG) supplied by the Laboratory for Space Research at Utrecht. It uses mesh-supported grating facets of 1.0-μm period and is optimized for operation down to 80 eV. Gratings are most effective for the study of point sources, but they also give moderate resolution spectra of slightly extended sources and can be used to map the spatial distribution of line-emitting regions.

Transmission grating spectroscopy and the Advanced X-Ray Astrophysics Facility

The Einstein Observatory Focal Plane Crystal Spectrometer (FPCS) used the technique of Bragg spectroscopy to study cosmic X-ray sources in the 0.2-3 keV energy range. The high spectral resolving power (E/Delta-E is approximately equal to 100-1000) of this instrument allowed it to resolve closely spaced lines and study the structure of individual features in the spectra of 41 cosmic X-ray sources. An archival summary of the results is presented as a concise record the FPCS observations and a source of information for future analysis by the general astrophysics community. For each observation, the instrument configuration, background rate, X-ray flux or upper limit within the energy band observed, and spectral histograms are given. Examples of the contributions the FPCS observations have made to the understanding of the objects observed are discussed.

Kenneth S. K. Lum

Papers

Transmission grating spectroscopy and the Advanced X-Ray Astrophysics Facility

The spectral archive of cosmic X-ray sources observed by the Einstein Observatory Focal Plane Crystal Spectrometer