65 research outputs found
High-energy astronomy from a lunar base
A discussion is presented of the advantages of the Moon for X-ray astronomy. It is concluded that large area detectors connected to long focal length telescopes will provide superior signal to noise ratios and resolution compared to any high energy photon observatories that can be practically placed in Earth orbit
Large-angle OBServaTory with Energy Resolution for Synoptic X-ray Studies (LOBSTER-SXS)
The soft X-ray band hosts a larger, more diverse range of variable sources
than any other region of the electromagnetic spectrum. They are stars, compact
binaries, SMBH's, the X-ray components of Gamma-Ray Bursts, their X-ray
afterglows, and soft X-ray flares from supernova. We describe a concept for a
very wide field (~ 4 ster) modular hybrid X-ray telescope system that can
measure positions of bursts and fast transients with as good as arc second
accuracy, the precision required to identify fainter and increasingly more
distant events. The dimensions and materials of all telescope modules are
identical. All but two are part of a cylindrical lobster-eye telescope with
flat double sided mirrors that focus in one dimension and utilize a coded mask
for resolution in the other. Their positioning accuracy is about an arc minute.
The two remaining modules are made from the same materials but configured as a
Kirkpatrick-Baez telescope with longer focal length that focuses in two
dimensions. When pointed it refines the hybrid telescope's arc minute positions
to an arc second and provides larger effective area for spectral and temporal
measurements. Above 10 keV the mirrors act as an imaging collimator with
positioning capability. For short duration events this hybrid focusing/coded
mask system is more sensitive and versatile than either a 2D coded mask or a 2D
lobster-eye telescope. Very wide field X-ray telescopes have become feasible as
the ability to fabricate large area arrays of CCD and CMOS detectors has
improved. This instrument's function in the soft X-ray band is similar to that
of Swift in hard X-ray band and there are a greater variety of fast transients
in the soft X-ray band. An instrument with considerably more sensitivity than
current wide field X-ray detectors would be compatible with a modest NASA
Explorer mission.Comment: 15 pages, 5 figures, To be presented at SPIE Conference 8147 "Optics
for EUV, X-Ray, and Gamma-Ray Astronomy V", Aug.21-25, 201
Research with Large Area Imaging X-Ray Telescope Sounding Rocket Program
We are engaged in a program to develop focussing hard X-ray telescopes in a double conical or Wolter 1 geometry that function up to 100 keV by employing small graze angles and multilayer coatings. Directly polished substrates are not an option because they are too thick to be nested efficiently. The only alternative is to fabricate the very thin substrates by replication. Our objective is the production of integral cylindrical substrates because they should result in better angular resolution than segmented foil geometries. In addition, integral cylinders would be more resistant to possible stress from deep multilayer coatings than segmented ones. Both electroforming of nickel (method of SkX, JET-X, and XMM) and epoxy replication are under consideration. Both processes can utilize the same types of mandrels and separation agents- While electroforming can produce substrates that are thin, the high density of the nickel may result in high weight optics for some missions. For convenience, experimentation with replication and coating is being carried out initially on flats. Our replication studies include trials with gold and carbon separation agents. This paper reports on our efforts with epoxy replicated optics
Hard X-Ray and Wide Focusing Telescopes
Studies are being carried out to compare the performance of several different separation materials used in the replication process. This report presents the results obtained during the second year of a program which consists of replicating smooth, thin substrates, depositing multilayer coatings upon them, and evaluating their performance. Replication and multilayer coatings are both critically important to the development of focussing hard X-ray telescopes that function up to 100 keV. The activities of the current year include extending the comparison between sputtered amorphous carbon and evaporated gold to include sputtered as well as evaporated gold. The figure of merit being the smoothness of the replica which has a direct effect on the specular reflectivity. These results were obtained with epoxy replication, but they should be applicable to electroformed nickel, the process we expect to use for the ultimate replicated optics
The large area modular array of reflections (LAMAR)
The Large Area Modular Array of Reflectors (LAMAR) was selected as an attached payload for the Space Station Freedom in June 1989. It is a high throughput multiple X-ray telescope system that was capable of performing both imaging and dispersive spectroscopy measurements simultaneously. The LAMAR program was halted in 1990 when attached payloads were removed from the Space Station. A technical description of LAMAR is the main body of this report
A Hard X-Ray Telescope Science Enhancement Package for the Constellation X-Ray Mission
Details of a hard-x-ray science enhancement package for the Constellation-X mission are presented. A scientific case is made for the inclusion of such an instrument on the planned mission and a detailed design is presented that will satisfy science requirements yet fall within the ground rules for enhancement packages: a cost of less than $100M and a mass of no more than 100 kg
Astronomical Signatures of Dark Matter
Several independent astronomical observations in different wavelength bands reveal the existence of much larger quantities of matter than what we would deduce from assuming a solar mass to light ratio. They are very high velocities of individual galaxies within clusters of galaxies, higher than expected rotation rates of stars in the outer regions of galaxies, 21 cm line studies indicative of increasing mass to light ratios with radius in the halos of spiral galaxies, hot gaseous X-ray emitting halos around many elliptical galaxies, and clusters of galaxies requiring a much larger component of unseen mass for the hot gas to be bound. The level of gravitational attraction needed for the spatial distribution of galaxies to evolve from the small perturbations implied by the very slightly anisotropic cosmic microwave background radiation to its current web-like configuration requires much more mass than is observed across the entire electromagnetic spectrum. Distorted shapes of galaxies and other features created by gravitational lensing in the images of many astronomical objects require an amount of dark matter consistent with other estimates. The unambiguous detection of dark matter and more recently evidence for dark energy has positioned astronomy at the frontier of fundamental physics as it was in the 17th century
Materials and structures
Materials and structures technology covers a wide range of technical areas. Some of the most pertinent issues for the Astrotech 21 missions include dimensionally stable structural materials, advanced composites, dielectric coatings, optical metallic coatings for low scattered light applications, low scattered light surfaces, deployable and inflatable structures (including optical), support structures in 0-g and 1-g environments, cryogenic optics, optical blacks, contamination hardened surfaces, radiation hardened glasses and crystals, mono-metallic telescopes and instruments, and materials characterization. Some specific examples include low coefficients of thermal expansion (CTE) structures (0.01 ppm/K), lightweight thermally stable mirror materials, thermally stable optical assemblies, high reliability/accuracy (1 micron) deployable structures, and characterization of nanometer level behavior of materials/structures for interferometry concepts. Large filled-aperture concepts will require materials with CTE's of 10(exp 9) at 80 K, anti-contamination coatings, deployable and erectable structures, composite materials with CTE's less than 0.01 ppm/K and thermal hysteresis, 0.001 ppm/K. Gravitational detection systems such as LAGOS will require rigid/deployable structures, dimensionally stable components, lightweight materials with low conductivity, and high stability optics. The Materials and Structures panel addressed these issues and the relevance of the Astrotech 21 mission requirements by dividing materials and structures technology into five categories. These categories, the necessary development, and applicable mission/program development phasing are summarized. For each of these areas, technology assessments were made and development plans were defined
What Have We Learned from RHIC?
In this talk, I present what I believe we have learned from the recent RHIC
heavy ion experiments. The goal of these experiments is to make and study
matter at very high energy densities, greater than an order of magnitude larger
than that of nuclear matter. Have we made such matter? What have we learned
about the properties of this matter? What do we hope and expect to learn in the
future?Comment: 34 figure
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