S. Romaine

Mirror Technology Development for the International X-ray Observatory Mission

The International X-ray Observatory mission is a collaborative effort of NASA, ESA, and JAXA. It will have unprecedented capabilities in spectroscopy, imaging, timing and polarization measurement. A key enabling element of the mission is a flight mirror assembly providing unprecedented large effective area (3 m2) and high angular resolution of (5 arcseconds half-power diameter). In this paper we outline the conceptual design of the mirror assembly and development of technology to enable its construction.

Development of a Prototype Nickel Optic for the Constellation-X Hard-X-Ray Telescope

The Constellation-X mission planned for launch in 2015-2020 timeframe, will feature an array of Hard X-ray telescopes (HXT) with a total collecting area greater than 1500 cm at 40 keV. Two technologies are being investigated for the optics of these telescopes, one of which is multilayer-coated Electroformed-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. We are building a prototype HXT mirror module using an ENR process to fabricate the individual shells.This prototype consists of 5 shells with diameters ranging from 15 cm to 28 cm with a length of 42.6 cm. The innermost of these will be coated with iridium, while the remainder will be coated with graded d-spaced W/Si multilayers. The assembly structure has been completed and last year we reported on full beam illumination results from the first test shell mounted in this structure. We have now fabricated and coated two (15 cm and 23 cm diameter) 100 micron thick shells which have been aligned and mounted. This paper presents the results of full beam illumination X-ray tests, taken at MPE-Panter. The HEW of the individual shells will be discussed, in addition to results from the full two shell optic test.

The Constellation-X Observatory

The Constellation-X Observatory is currently planned as NASAs next major X-ray observatory to be launched towards the end of the next decade. The driving science goals for the mission are to: 1) Trace the evolution of Black Holes with cosmic time and determine their contribution to the energy output of the Universe; 2) Observe matter spiraling into Black Holes to test the predictions of General Relativity; 3) Use galaxy clusters to trace the locations of Dark Matter and follow the formation of structure as a function of distance; 4) Search for the missing baryonic matter; 5) Directly observe the dynamics of Cosmic Feedback to test models for galaxy formation; 6) Observe the creation and dispersion of the elements in supernovae; and 7) Precisely constrain the equation of state of neutron stars. To achieve these science goals requires high resolution (R > 1250) X-ray spectroscopy with 100 times the throughput of the Chandra and XMMNewton. The Constellation-X Observatory will achieve this requirement with a combination of four large X-ray telescopes on a single satellite operating in the 0.25 to 10 keV range. These telescopes will feed X-ray micro-calorimeter arrays and grating spectrometers. A hard X-ray telescope system will provide coverage up to at least 40 keV. We describe the mission science drivers and the mission implementation approach.

NHXM: a New Hard X-ray imaging and polarimetric Mission

The New Hard X-ray Mission (NHXM) has been designed to provide a real breakthrough on a number of hot astrophysical issues that includes: black holes census, the physics of accretion, the particle acceleration mechanisms, the effects of radiative transfer in highly magnetized plasmas and strong gravitational fields. NHXM combines fine imaging capability up to 80 keV, today available only at E<10 keV, with sensitive photoelectric imaging polarimetry. It consists of four identical mirrors, with a 10 m focal length, achieved after launch by means of a deployable structure. Three of the four telescopes will have at their focus identical spectral-imaging cameras, while a X-ray imaging polarimeter will be placed at the focus of the fourth. In order to ensure a low and stable background, NHXM will be placed in a low Earth equatorial orbit. Here we will provide an overall description of this mission and of the developments that are currently occurring in Italy. In the meanwhile we are forming an international collaboration, with the goal to have a consortium of leading Institutes and people that are at the forefront of the scientific and technological developments that are relevant for this mission.

Technology development for the Constellation-X hard-x-ray telescope

In addition to high resolving power in the traditional x-ray band, the Constellation X-ray scientific goals require broad bandpass, with response extending to E >= 40 keV. To achieve this objective, Constellation-X will incorporate a hard x-ray telescope (HXT) based on depth graded multilayer- coated grazing incidence optics and position-sensitive solid state detectors. This paper describes the HXT performance requires, provides an overview of the HXT optics and detector technology development efforts, and present example designs.

Replication by Ni electroforming approach to produce the Con-X/HXT hard x-ray mirrors

The NASAs Constellation X-Ray Mission consists of a Soft X-Ray Telescope (SXT) based on large collecting area optics plus a focusing Hard X-Ray Telescope (HXT) operating between 8 and 70 keV and possibly at even higher energy. The Con-X HXT will have a focal length of 10 m and graze angles are small (0.25 - 0.1 deg). The substrates will be coated with multilayers to enhance the reflectivity but single heavy element coatings are an alternative for the small diameter substrates of the set. Twelve copies of the HXT are distributed evenly among the four Con-X spacecrafts. With multiple telescopes it is appropriate to consider electroforming, the replication process used successfully by Beppo-SAX, JET-X/SWIFT, and XMM-Newton, to produce their substrates. The important feature of the technique is that for mirrors with aperture diameters less than 40 cm also with thin substrates it is possible to achieve good angular resolution, which is important for obtaining high signal-to-noise ratios in deep observations and imaging extended sources. We review the main results of our development study devoted to proving the feasibility of the process for the Con-X/HXT, with particular stress on demonstrating, not only by theoretical considerations but also presenting an important experimental proof, that we can satisfy the severe mass constraints of the mission still maintaining good imaging capabilities.

Simbol-X hard X-ray focusing mirrors: results obtained during the phase A study

Simbol‐X will push grazing incidence imaging up to 80 keV, providing a strong improvement both in sensitivity and angular resolution compared to all instruments that have operated so far above 10 keV. The superb hard X‐ray imaging capability will be guaranteed by a mirror module of 100 electroformed Nickel shells with a multilayer reflecting coating. Here we will describe the technogical development and solutions adopted for the fabrication of the mirror module, that must guarantee an Half Energy Width (HEW) better than 20 arcsec from 0.5 up to 30 keV and a goal of 40 arcsec at 60 keV. During the phase A, terminated at the end of 2008, we have developed three engineering models with two, two and three shells, respectively. The most critical aspects in the development of the Simbol‐X mirrors are i) the production of the 100 mandrels with very good surface quality within the timeline of the mission, ii) the replication of shells that must be very thin (a factor of 2 thinner than those of XMM‐Newton) and sti...

X-ray monochromator for divergent beam radiography using conventional and laser-produced x-ray sources

We discuss technology that will produce a wide angle monochromatic beam of X-rays that appears to diverge from a virtual point source. Although our ideas are discussed in the context of dual energy subtraction angiography (DESA) that we are developing to operate in a clinical setting, they are widely adaptable to all applications of x-ray radiography. The best DESA analysis is obtained from X-ray images made in narrow energy bands just below and just above the I K-absorption edge. Our monochromator will be used to isolate these narrow bands to produce high contrast, high spatial resolution, ECG gated angiographic images. Emission lines, that have X-ray energies below (E-) and above (E+) the I K-absorption edge at 33.2 keV, are readily available. We have deposited variable d-spacing artificial crystals, called multilayers, on optically flat, very smooth substrates, to create narrow pass band X-ray monochromators centered on La and Ba K-emission lines. We will record (E-) and (E+) exposures on either photographic plates or, in the future, with energy sensitive pixelated arrays of solid state detectors. After a suitable normalization, the exposures will be subtracted to yield a high resolution, high contrast image of the I filled arteries. Although initial results will be obtained with conventional X-ray tubes, our goal is to couple the monochromators to a high intensity, laser produced, X-ray plasma. We will present early test data that shows the multilayer performance.

Hard x-ray multilayers: a study of different material systems

Multilayer structures with depth-graded spacing can show a high reflectivity in a broad energy passband for hard X-rays if the interface roughness/diffuseness is controlled and minimized. We present a study of several multilayer systems deposited by DC magnetron sputtering on <111> silicon wafers and superpolished fused silica substrates. The material combinations discussed are W/Si, WSi2/Si, W/C, Pt/C, Ni/C, Ni/B4C, and Mo/Si. The deposition method used was DC magnetron sputtering at low argon pressures (1.5 to 5 mT). The characterization methods used were: Atomic Force Microscopy in tapping mode, stylus profilometry, Rutherford backscattering, cross sectional TEM, and specular X-ray reflectivity (XRR) scans at 8.05 keV. Different process parameters were varied in order to optimize the interface roughness/diffuseness (sigma) that was measured by XRR scans.

X-ray optics made from thin plastic foils

New design concepts and materials can be used to produce very lightweight, thin foil approximations, to Wolter I and other x-ray optics. Structures are designed around a central hub and spacers that connect one spoked wheels. Figure defining, thin pins span the distance between the wheels. Thin, metal coated or multilayered, plastic foils can be formed into cones, cylinders or spirals for x-ray telescopes or lenses. Imaging and spectroscopic data obtained with x- ray lenses are presented and they indicate that a 60 cm diameter, 4.65 m focal length x-ray telescope can have a half power diameter of < 2 arcmin.