Development of a prototype nickel optic for the Constellation-X hard x-ray telescope

Abstract

bOsservatorio Astronomico di Brera -23808 Merate(Lc) -Italy CNASA/Marshall Space Flight Center dUSRA, AL eUnjversjty of AL 1BCV Progetti, Milano Raytheon, ITSS, AL ABSTRACT The Constellation-X mission, planned for launch in 2013, will feature an array of hard-x-ray telescopes (HXT) with a total collecting area of greater than 1500 cm2 at 40 keY. Two technologies are currently being investigated for the optics of these telescopes including multilayer-coated Eletroformed-Nickel-Replicated (ENR) shells. The attraction of the ENR process is that the resulting full-shell optics are inherently stable and offer the prospect of better angular resolution which results in lower background and higher instrument sensitivity. The challenge for this process is to meet a relatively tight weight budget with a relatively dense material (pnjckel 9 g/cm3.)To demonstrate the viability of the ENR process we are fabricating a prototype HXT mirror module to be tested against a competing segmented-glass-shell optic. The ENR prototype will consist of 5 shells of diameters from 150 mm to 280 mm with a length of 426 mm. To meet the stringent weight budget for Con-X, the shells will range in thickness from 100 microns to 150 microns. The innermost of these will be coated with Iridium, while the remainder will be coated with graded-dspaced W/Si multilayers.Mandrels for these shells are in the fabrication stage, the first test shells have been produced and are currently undergoing tests for figure and microroughness. A tentative date of June '04 has been set for the prototype X-ray testing at MSFC. Issues currently being addressed are the control of stresses in the multiplayer coating and ways of mitigating their effects on the figure of the necessarily thin shells. The fabrication, handling and mounting of these shells must be accomplished without inducing permanent figure distortions.A full status report on the prototype optic will be presented along with test results as available.

Analysis of microroughness evolution in X-ray astronomical multilayer mirrors by surface topography with the MPES program and by X-ray scattering

“…table 1). The deposition facility 15 used to coat the sample allowed to limit the microroughness evolution at a very low level (σ ML = 1.95 Å): more precisely, the growth of microroughness amounts to only 1 Å rms with respect to the initial substrate level (see tab. 11).…”

“…The sample E is a multilayer deposited on a superpolished fused silica substrate with a DC magnetron sputtering facility 15 installed at the Smithsonian Astrophysical Observatory (SAO): this facility is specifically conceived to deposit multilayer coatings on mirror shells preformed by Ni electroforming. The research is aimed to manufacture the hard Xray optics of Constellation-X 16 .…”

Improved release coatings for electroformed x-ray optics

“…Multilayer coatings such as W/Si are used to broaden the energy response for hard X-ray astronomy optics beyond the ~ 10 keV limit of single layer metallic coatings such as iridium and gold. Current methods of depositing such coatings use dc magnetron sputtering to directly apply the multilayer coating to the optic [8,9,10]. To deposit a multilayer on the inside of a closed shell optic, the magnetrons must be inserted inside the shell, hence there is a limit to the smallest diameter optic that can be coated using this technique.…”

Calibration of hard x-ray (15 - 50 keV) optics at the MPE test facility PANTER

“…The PANTER facility has been recently (November 2002) used for the characterization of a single-cone multilayer mirror shell prototype realized in the context of the development of the Hard X-ray Telescope for the Constellation-X mission 21,22 . The prototype was realized in two different steps: a) a gold-coated mirror shell was produced by Ni electroforming replication, making use of a supersmooth mandrel realized at OAB (Milano, Italy); b) a multilayer coating was then applied to the internal surface of the shell by magnetron sputtering at the Harvard-Smithsonian CfA (Cambridge, MA, USA) by means of a coating facility specifically developed for making hard X-ray mirrors 23 .…”