The Joint astrophysical Plasmadynamic EXperiment (J-PEX) is a high-resolution extreme ultraviolet (EUV)
spectrometer (220-245 Å) used for the study of white dwarf atmospheres. Significant improvements have been achieved
in both the normal-incidence gratings and the focal-plane detector since its first successful sounding rocket flight in
2001. The spherical laminar gratings have been replaced by paraboloidal gratings. The substrates of the new gratings
have measured slope errors less than 0.35 arcsec. The gratings were recorded holographically and the rulings transferred
into the silica substrates by ion etching. This procedure was followed by polymer overcoat to reduce the blaze angle of
the groove profile. The detector uses microchannel plates with 6 μm pores and a cross-strip anode, providing 17.9 μm
resolution in the dispersion direction. The detector employs a KBr photocathode with a projected efficiency of 0.24 at
256 Å. Using ray tracing simulations, we predict the resolving power expected from the spectrometer during upcoming
EUV calibrations with a He II discharge source.
We have fabricated five new holographic ion-etched polymer-coated gratings for a reflight on a sounding rocket of the J-PEX high-resolution EUV spectrometer. The gratings are parabolic (nominal 2000-mm focal length), large (160 mm x 90 mm), and have a blazed groove profile of high density (3600 grooves/mm at the vertex). They have been coated with a high-reflectance multilayer of Mo/Si/C. Using an atomic force microscope, we examined grating topography before multilayer coating. The surface roughness is 2 angstrom rms and the blaze angle is near the target value of 2.4°. Using synchrotron radiation, we completed an efficiency calibration map of each multilayer-coated grating over the wavelength range 220-245 angstrom. At an angle of incidence of 5°, the average efficiency in the first inside order peaks near 234 angstrom. The average peak efficiency is 12.3 ± 1.0% for Grating 1, 12.6 ± 2.4% for Grating 2, 12.6 ± 1.8% for Grating 3, 14.1 ± 3.0% for Grating 4, and 13.0 ± 1.0% for Grating 5. The derived groove efficiency averaged over all gratings is approximately
50%, which meets our goals. Refined models of the multilayer gratings are required to resolve remaining issues.
The development of hard X-ray focusing optics is widely recognized as
one of key technologies for future X-ray observatory missions such as
NeXT(Japan), Constellation-X(US) and possibly XEUS(Europe). We have developed hard X-ray telescope employing depth-graded multilayers, so-called supermirrors. Its benefit is to reflect hard X-rays by Bragg reflection at incidence angles larger than the critical angle of total external reflection. We are now continuously fabricating platinum-carbon(Pt/C) supermirror reflectors for hard X-ray observations. In this paper we focus on our development of the
hard X-ray telescope for the first balloon flight observation
(InFOCuS) and its results. InFOCuS is an international balloon-borne hard X-ray observation experiment initiated by NASA/GSFC. InFOCuS hard X-ray telescope have been jointly developed by Nagoya University and GSFC. The telescope is conical approximation of Wolter-I optics with 8m focal length and 40cm diameter. It consists of 255 nested ultra-thin reflector pairs with incidence angles of 0.10 to 0.36deg. Reflectors are coated with Pt/C supermirrors with periodic length of 2.9 to 10nm and bi-layer number of 25 to 60, depending on incidence angles. The effective area and imaging quality are expected as 100 cm<sup>2</sup> at 30 keV and 2 arcmin in half power diameter, respectively. The InFOCuS experiment was launched on July 5, 2001, from National Scientific Balloon Facility in Texas, USA. We successfully observed Cyg X-1, chosen for a calibration target, in 20-40keV energy band. We are planning to carry out next flight for scientific observations as soon as additional telescopes, detectors, and upgraded gondola system are implemented.
The CZT detector on the Infocus hard X-ray telescope is a pixellated
solid-state device capable of imaging spectroscopy by measuring the
position and energy of each incoming photon. The detector sits at the
focal point of an 8m focal length multilayered grazing incidence
X-ray mirror which has significant effective area between 20-40 keV.
The detector has an energy resolution of 4.0 keV at 32 keV, and the
Infocus telescope has an angular resolution of 2.2 arcminute and a
field of view of about 10 arcminutes. Infocus flew on a balloon
mission in July 2001 and observed Cygnus X-1. We present results from
laboratory testing of the detector to measure the uniformity of
response across the detector, to determine the spectral resolution,
and to perform a simple noise decomposition. We also present a hard
X-ray spectrum and image of Cygnus X-1, and measurements of the hard
X-ray CZT background obtained with the SWIN detector on Infocus.
We have been developing the high throughput hard X-ray telescope, using reflectors coated with the depth graded multilayer known as supermirror, which is considered to be a key technology for future satellite hard X-ray imaging missions. InFOC(mu) $S, the International Focusing Optics Collaboration for (mu) -Crab Sensitivity is the project of the balloon observation of a cosmic hard X-ray source with this type of hard X-ray telescope and CdZnTe pixel detector as a focal plane imager. For the fist InFOC(mu) S balloon experiment, we developed the hard X-ray telescope with outermost diameter of 40cm, focal length of 8m and energy band pass of 20-40 keV, for which Pt/C multilayer was used. From the pre-flight X-ray calibration, we confirmed its energy band and imaging capability of 2 arcmin HPD and 10 arcmin FOV of FWHM, and a effective area of 50 cm<SUP>2</SUP> for 20-40 keV X-ray. We report the current status of our balloon borne experiment and performance of our hard X-ray telescope.
Mass production of replicated thin aluminum x-ray reflecting foils for the InFOC(mu) S (International Focusing Optics Collaboration for Micro-Crab Sensitivity) balloon payload is complete, and the full mirror has been assembled. InFOC(mu) S is an 8-meter focal length hard x-ray telescope scheduled for first launch in July 2001 and will be the first instrument to focus and image x-rays at high energies (20-40 keV) using multilayer-based reflectors. The individual reflecting elements are replicated thin aluminum foils, in a conical approximation Wolter-I system similar to those built for ASCA and ASTRO-E. These previous imaging systems achieved half-power-diameters of 3.5 and 1.7-2.1 arcminutes respectively. The InFOC(mu) S mirror is expected to have angular resolution similar to the ASTRO-E mirror. The reflecting foils for InFOC(mu) S, however, utilize a vertically graded Pt/C multilayer to provide broad-band high-energy focusing. We present the results of our pre-flight characterization of the full mirror, including imaging and sensitivity evaluations. If possible, we will include imaging results from the first flight of a multilayer-based high-energy focusing telescope.
High sensitivity hard X-ray data by means of focusing optics is crucially important to investigate active galaxies and cluster of galaxies. We have developed focusing telescopes with platinum-carbon multilayer coatings. The energy band is broadened by multilayers with graded periodic length, so called `Supermirrors'. We were successful to obtain hard X- ray images in the energy band from 25 to 40 keV with a demonstration model of telescope with 20 mirror shells of supermirrors. The flight model of supermirror telescope is now in production for balloon flight in the summer of 2000. The current status of the balloon mission and future application of supermirror technology is discussed.
The ability of periodic and aperiodic multilayer structures to diffract x-rays at grazing angles has long been understood, and has been successfully exploited in the x-ray region, primarily on flat substrates. We have recently begun producing Pt/C multilayer coated thin foil mirrors for the InFOC(mu) S balloon mission. The mirrors are made by depositing the multilayer on glass mandrels and transferring the multilayer to the thin foil substrates using a replication process similar to that used for production of the recently lost ASTRO-E mirrors. Both periodic and broadband versions have been successfully replicated onto thin foils and characterized by grazing incidence x-ray scattering. Initial comparisons between mirrors deposited on flat float glass substrates and mirrors replicated onto thin foils indicate that the reflection properties of the multilayer are not damaged by the transfer from mandrel to foil. We describe the production and characterization facilities that have been developed in our lab, and the performance of our multilayer mirrors, with particular emphasis on the characterization of interfaces in the Pt/C system.