The next generation x-ray observatory ATHENA (advanced telescope for high energy astrophysics) requires an optics with unprecedented performance. It is the combination of low mass, large effective area and good angular resolution that is the challenge of the x-ray optics of such a mission. ATHENA is the second large class mission in the science programme of ESA, and is currently in a reformulation process, following a design-to-cost approach to meet the cost limit of an ESA L-class mission.

The silicon pore optics (SPO) is the mission enabler being specifically developed for ATHENA, in a joint effort by industry, research institutions and ESA. All aspects of the optics are being addressed, from the mirror plates and their coatings, over the mirror modules and their assembly into the ATHENA telescope, to the facilities required to build and test the flight optics, demonstrating performance, robustness, and programmatic compliance.

Background: To ensure consistent and high-quality semiconductor production at future logic nodes, additional metrology tools are needed. For this purpose, grazing-incidence small-angle x-ray scattering (GISAXS) is being considered because measurements are fast with a proven capability to reconstruct average grating line profiles with high accuracy.

Aim: GISAXS measurements of grating line shapes should be extended to samples with pitches smaller than 50 nm and their defects. The method’s performance should be evaluated.

Approach: A series of gratings with 32-nm pitch and deliberately introduced pitchwalk is measured using GISAXS. The grating line profiles with associated uncertainties are reconstructed using a Maxwell solver and Markov-chain Monte Carlo sampling combined with a simulation library approach.

Results: The line shape and the pitchwalk are generally in agreement with previously published transmission small-angle x-ray scattering (SAXS) results. However, the line height and line width show deviations of   (  1.0  ±  0.2  )    nm and   (  2.0  ±  0.7  )    nm, respectively. The complex data evaluation leads to relatively high pitchwalk uncertainties between 0.5 and 2 nm.

Conclusions: GISAXS shows great potential as a metrology tool for small-pitch line gratings with complex line profiles. Faster simulation methods would enable more accurate results.

Future high energy astrophysics missions will require high performance novel X-ray optics to explore the Universe beyond the limits of the currently operating Chandra and Newton observatories. Innovative optics technologies are therefore being developed and matured by the European Space Agency (ESA) in collaboration with research institutions and industry, enabling leading-edge future science missions.

Silicon Pore Optics (SPO) [1 to 21] and Slumped Glass Optics (SGO) [22 to 29] are lightweight high performance X-ray optics technologies being developed in Europe, driven by applications in observatory class high energy astrophysics missions, aiming at angular resolutions of 5” and providing effective areas of one or more square meters at a few keV.

This paper reports on the development activities led by ESA, and the status of the SPO and SGO technologies, including progress on high performance multilayer reflective coatings [30 to 35]. In addition, the progress with the X-ray test facilities and associated beam-lines is discussed [36].

Silicon Pore Optics is an enabling technology for future L- and M-class astrophysics X-ray missions, which require high angular resolution (~5 arc seconds) and large effective area (1 to 2 m² at a few keV). The technology exploits the high-quality of super-polished 300 mm silicon wafers and the associated industrial mass production processes, which are readily available in the semiconductor industry. The plan-parallel wafers have a surface roughness better than 0.1 nm rms and are diced, structured, wedged, coated, bent and stacked to form modular Silicon Pore Optics, which can be grouped into a larger optic. The modules are assembled from silicon alone, with all the mechanical advantages, and form an intrinsically stiff pore structure.

The optics design was initially based on long (25 to 50 m) focal length X-ray telescopes, which could achieve several arc second angular resolution by curving the silicon mirror in only one direction (conical approximation).

Recently shorter focal length missions (10 to 20 m) have been discussed, for which we started to develop Silicon Pore Optics having a secondary curvature in the mirror, allowing the production of Wolter-I type optics, which are on axis aberration-free.

In this paper we will present the new manufacturing process, the results achieved and the lessons learned.

The characterization of large aperture (> 2 meters), long focal length (> 10 meters) X-ray mirrors for X-ray astronomy with synchrotron radiation poses signi cant problems related to the available space at synchrotron radiation facilities. Intrafocal pencil beam characterization of part of the optics is advantageous if its results can be shown to have predictive capabilities with respect to the full system.

In this paper we present the routine characterization of silicon pore optics at the X-ray Pencil Beam Facility of the Physikalisch-Technische Bundesanstalt, located at the synchrotron radiation facility BESSY II (Berlin, Germany). In particular we show how measurements taken in the standard beamline con guration (detector at ve meters from the optics) can e ectively be used to predict the optical performance of the optics at their design focal length by comparing data taken on 20-meter focal length Silicon Pore Optics unit in the 20-meter beamline con guration (available only for a few weeks every year) with extrapolated 5-meter measurements.

Silicon Pore Optics (SPO) is a lightweight high performance X-ray optics technology being developed in Europe, driven by applications in observatory class high energy astrophysics missions. An example of such application is the former ESA science mission candidate ATHENA (Advanced Telescope for High Energy Astrophysics), which uses the SPO technology for its two telescopes, in order to provide an effective area exceeding 1 m² at 1 keV, and 0.5 m² at 6 keV, featuring an angular resolution of 10” or better [1 to 24].

This paper reports on the development activities led by ESA, and the status of the SPO technology. The technology development programme has succeeded in maturing the SPO further and achieving important milestones, in each of the main activity streams: environmental compatibility, industrial production and optical performance. In order to accurately characterise the increasing performance of this innovative optical technology, the associated X-ray test facilities and beam-lines have been refined and upgraded.