The XMM-Newton Observatory is a cornerstone mission of the European Space Agency's Horizon 2000 programme, and is the largest scientific satellite it has launched to date. This paper summarises the principal characteristics of the Observatory which are pertinent to scientific operations. The scientific results appearing in this issue have been enabled by the unprecedentedly large effective area of the three mirror modules, which are briefly described. The in-orbit performance and preliminary calibrations of the observatory are briefly summarised. The observations from the XMM-Newton calibration and performance verification phase, which are public and from which most papers in this issue have been derived, are listed. The flow of data from the spacecraft, through the ground segment, to the production of preliminary science products supplied to users is also discussed.

XMM-Newton observatory*: I. The spacecraft and operations. Commentary

In this paper we present the "Characterization Universal Profilometer" (CUP), a new metrological instrument developed
at the Brera Observatory for the 3D surface figure mapping of X-ray segmented mirrors. The CUP working principle is
based on the measure of the the distance between the surface under test from a rigid reference dish. This approach is
made possible by the coupled use of two sensors, the CHRocodile® optical device and the SIOS triple beam
interferometer, mounted onto a proper system of x-y-z stage of translators. In this paper we describe the working
principle of the new instrument. We will also present the results of the commissioning performed for a CUP breadboard
developed at the Brera Observatory. The CUP offers the possibility to perform an high accuracy metrology of thin glass
segments produced via hot slumping, to be used in future segmented X-ray mirrors like those foreseen aboard IXO or
other projects that will make use of active X-ray mirrors.

3D characterization of thin glass x-ray mirrors via optical profilometry

The use of evolutionary algorithms (EA s) for solving multiobjective optimization problems has been very active in the last few years. The main reasons for this popularity are their ease of use with respect to classical mathematical programming techniques, their scalability, and their suitability for finding trade-off solutions in a single run. However, these algorithms may be computationally expensive because (1) many real-world optimization problems typically involve tasks demanding high computational resources and (2) they are aimed at finding a whole front of optimal solutions instead of searching for a single optimum. Parallelizing EAs emerges as a possible way of reducing the CPU time down to affordable values, but it also allows researchers to use an advanced search engine – the parallel model – that provides the algorithms with an improved population diversity and enable them to cooperate with other (eventually nonevolutionary) techniques. The goal of this chapter is to provide the reader with an up-to-date review of the recent literature on parallel EAs for multiobjective optimization.

Parallel Multiobjective Evolutionary Algorithms

Fundamental needs for future x-ray telescopes: a) Sharp images => excellent angular resolution b) High throughput => large aperture areas Generation-X optics technical challenges: a) High resolution => precision mirrors & alignment b) Large apertures => lots of lightweight mirrors Innovation needed for technical readiness: a) 4 top-level error terms contribute to image size b) There are approaches to controlling those errors Innovation needed for manufacturing readiness Programmatic issues are comparably challenging

High-Resolution X-Ray Telescopes

In the production of integrated circuits (e.g. computer chips), optical lithography is used to transfer a pattern onto a semiconductor substrate (wafer). For lithographic systems using light in the ultraviolet band (EUV) with a 13.5nm nm wavelength, only reflective optics with multi-layers can reflect that light by means of interlayer interference, but these mirrors absorb around 30% of the incident light. Depending on pattern and beam shape, there is a nonuniform light distribution over the surface of the mirrors. This causes temperature gradients and therefore local deformations, due to different thermal expansions. To improve the throughput (wafers per hour), there is a demand to increase the source power, that will increase these deformations even further. Active mirrors are a solution to correct these deformations by reshaping the surface. This thesis addresses the challenges to accurate deform a mirror with high repeatability, meeting the requirements for implementation in a lithographic illumination machine. The main design criteria are vacuum compatibility, actuator stroke and the distance between actuators. Four different experimental mirrors, with increasing complexity, are successfully designed, realized and validated. All mirrors are equipped with thermomechanical actuators to either bend, or axially deform them. These actuators are free from mechanical hysteresis and therefore have a high position resolution with high reproducibility. Extensive finite element analysis is done, to maximize actuator stroke and minimize input power. All mirrors are tested and validated with interferometer surface measurements and thermocouple temperature measurements. The first experimental mirror with one thermo-mechanical bending actuator is successfully built and tested (chapter 2). To obtain a high mirror deflection at a given inserted actuator power, aluminum is chosen as the actuator material. The mirror is made from Zerodur® like the mirrors in the first EUV lithographic demonstration machines. A mirror deformation of 4:7 nm/C is achieved, where the inserted actuator power is 0.044 C/mW, meaning 0:21 nm/mW. The measured characteristic time constant is 10 s, meaning that for a given input, 63% of the steady state stroke is reached within that time scale. All values are close to the predicted ones from the models and also meet the requirements for implementation. To further investigate the concept and to measure the mechanical and thermal actuator coupling, an experimental mirror with four actuators is designed, developed and validated (chapter 3). It is an extension of the mirror with one actuator. In a single actuator step-response, a mirror deflection of 3.4 nm/C is achieved. A design optimization is proposed and successfully tested which reduces the actuator coupling from 30% to 10%, while the mirror deflection at the same input is reduced to 55%. Actuator speed is demonstrated while simultaneously heating all actuators with 3mW, which correspond with a mirror deformation of 33 pm/s. When using an adaptive mirror in an EUV lithography system, actuator strokes of 1 nm/min are required. The demonstrated actuator speed of 33 pm/s = 2 nm/min meets that requirement. The third and fourth mirror have actuators placed perpendicular to the surface (chapter 4). By placing the actuators on a thin back plate, the force loop is localized and therefore a lower actuator coupling is achieved. The results obtained from the third mirror with 7 actuators are close to the predicted values from the static and thermal models. Based on these good results, this actuation principle is implemented in a smaller deformable mirror with 19 actuators inside a 25mm beam diameter. A linear relation between actuator power and temperature of 0.190 C/mW and between power and averaged interactuator stroke of 0.13 nm/mW is achieved. So, the successfully realized mirror deflection is 0:68 nm/ C and no hysteresis is observed. For both mirrors a support frame is developed, that minimizes introduced surface deformations by temperature variations. Thermal step responses are fitted and both heating and cooling characteristic time constants are 2:5 s. The thermal actuator coupling from an energized actuator to its direct neighbor is 6:0, to their neighbors it is 1:3%. The total actuator coupling is approximated around 10%, based on the good agreement between simulated and measured inter-actuator stroke. Finally, chapter 5 summarizes the main findings from the different deformable mirrors and compares them. Also, suggestions for future research are given for implementation into a lithographic machine.

https://pure.tue.nl/ws/files/3733662/732113.pdf

Adaptive optics for extreme ultraviolet lithography : actuator design and validation for deformable mirror concepts

The Smart X-ray Optics (SXO) programme is developing advanced active-adaptive optics for X-rays. There are two
main themes: large optics for applications in astronomy and small scale optics for micro-probing of biological cells and
tissue samples using Ti or Cr Kα radiation (4.5keV and 5.4keV, respectively) in studies related to radiation induced
cancers. For the latter objective, microstructured optical arrays (MOAs) have been proposed. These consist of an array of
channels deep etched in silicon. They use grazing incidence reflection to focus the X-rays through consecutive aligned
arrays of channels, ideally reflecting once off a channel wall in each array. Bending the arrays allows variable focal
length. The adaptivity is achieved by flexing the arrays using PZT (Lead Zirconate Titanate)-based piezo actuators.
The array bending has been modelled using finite element analysis (FEA) and the results showed that for reasonable
efficiency, the wall roughness of the channels should not exceed 2nm.
This paper describes two techniques of fabrication the MOAs: dry etching and wet etching. The first method requires a
special equipment called "inductively coupled plasma" (ICP) using Bosch processes that are designed to produce
features with a high aspect ratio with vertical walls. The second method involves using an alkaline solution for etching
 silicon wafers. This type of wafer was selected because of the large wet etch ratio between the (111) and (100)
planes that leads to smooth vertical walls. For our application tetra-methyl-ammonium hydroxide (TMAH) was used as it
is fully compatible with CMOS integrated circuit processes.

Microstructured Optical Arrays for Smart X-ray Optics

This paper describes two fabrication techniques-dry and wet etching- for microstructured optical arrays (MOAs). The MOAs consist of arrays of channels deep etched in silicon. They use grazing incidence reflection to focus the X-rays through the consecutive aligned arrays of channels, ideally reflecting once off a vertical and smooth channel wall in each array. The MOAs were proposed by the Smart X-ray Optics (SXO) programme as small scale optics for micro-probing of biological cells and tissues. The first fabrication method requires inductively coupled plasma (ICP) using Bosch processes. The second one involves etching silicon wafers in alkaline solutions.

Micromachining optical arrays

This paper describes reflective adaptive/active optics for applications including studies of biological radiation damage. The optics work on the polycapillary principle, but use arrays of channels in thin silicon. For optimum performance the x-rays should reflect once off a channel wall in each of two successive arrays. This reduces aberrations since then the Abbe sine condition is approximately satisfied. Adaptivity is achieved by flexing the arrays via piezo actuation, providing further aberration reduction and controllable focal length.

http://iopscience.iop.org/article/10.1088/1742-6596/186/1/012067/pdf

Smart X-Ray Optics

Aperiodic molybdenum/silicon broadband multilayer analyzers with constant reflectivity over a wide spectral range for a fixed incidence angle have been designed using a combined analytical/numerical method. The analyzers were fabricated using direct current magnetron sputtering and characterized using the soft X-ray polarimeter at the BESSY facility. Nearly constant s-reflectivity, up to 37%, is observed over the 15–17 nm wavelength range at a grazing incidence angle of 50°, and the degree of polarization is over 98%. Furthermore, the analyzer also exhibits high sreflectivity and polarization over a broad angular range, 43–53°, at a fixed wavelength of 15.5 nm. This kind of broadband multilayer analyzer can be used in extreme ultraviolet polarization measurements, and will greatly simplify experimental arrangements.

Hongchang Wang

Papers

Microstructured Optical Arrays for Smart X-ray Optics

Micromachining optical arrays

Smart X-Ray Optics

Short communication Broadband Mo/Si multilayer analyzers for the 15-17 nm wavelength range