Search

SPIE Optical Engineering + Applications, San Diego, United States, 11 Aug 2019 - 15 Aug 2019; Journal of astronomical telescopes, instruments, and systems 8, 014005 (2022). doi:10.1117/1.JATIS.8.1.014005, The Cherenkov Telescope Array (CTA) is the next ground-based γ-ray observatory in the TeV γ-ray spectral region operating with the Imaging Atmospheric Cherenkov Technique. It is based on almost 70 telescopes of different class diameters - LST, MST and SST of 23, 12, and 4 m, respectively - to be installed in two sites in the two hemispheres (at La Palma, Canary Islands, and near Paranal, Chile). Several thousands of reflecting mirror tiles larger than 1 m$^2$ will be produced for realizing the segmented primary mirrors of a so large number of telescopes. Almost in parallel, the ASTRI Mini-Array (MA) is being implemented in Tenerife (Canary Islands), composed of nine 4 m diameter dual-mirror Cherenkov telescopes (very similar to the SSTs). We completed the mirror production for all nine telescopes of the ASTRI MA and two MST telescopes (400 segments in total) using the cold glass slumping replication technology. The results related to the quality achieved with a so large-scale production are presented, also discussing the adopted testing methods and approaches. They will be very useful for the adoption and optimization of the quality assurance process for the huge production (almost 3000 m$^2$ of reflecting surface) of the MST and SST CTA telescopes., Published by SPIE, [Bellingham, Wash.]

The VERT-X X-ray calibration facility, currently in prototypal realization phase supported by ESA, will be a vertical X-ray beamline able to test and calibrate the entire optical assembly of the ATHENA X-ray telescope. Owing to its long focal length (12 m), a full-illumination test of the entire focusing system would require a parallel and uniform X-ray beam as large as the optical assembly itself (2.5 m). Moreover, the module should better be laid parallel to the ground in order to minimize the effects of gravity deformations. Therefore, the ideal calibration facility would consist of a vertical beam, with the source placed at very large distance (>> 500 m) under high vacuum (10-6 mbar). Since such calibration systems do not exist, and also appear to be very hard to manufacture, VERT-X will be based on a different concept, i.e., the raster scan of a tightly (≈ 1 arcsec) collimated X-ray beam, generated by a microfocus source and made parallel via a precisely shaped Wolter-I mirror. In this design, the mirror will be made of two segments (paraboloid + hyperboloid) that, for the X-ray beam collimation to be preserved, will have to be accurately finished and maintain their mutual alignment to high accuracy during the scan. In this paper, we show simulations of the reflected wavefront based on physical optics and the expected final imaging quality, for different polishing levels and misalignments for the two segments of the VERT-X collimator.

Several hundreds of Silicon Pore Optics (SPO) mirror modules will be integrated and co-aligned onto the ATHENA (Advanced Telescope for High-ENergy Astrophysics) Mirror Assembly Module (MAM). The selected integration process, developed by Media Lario, exploits a full size optical bench to capture the focal plane image of each mirror module when illuminated by an UV plane wavefront at 218 nm. Each mirror module, handled by a manipulator, focuses the collimated beam onto a CCD camera placed at the 12 m focal position of the ATHENA telescope. The image is processed in real time to calculate the centroid position and overlap it to the centroid of the already integrated Mirror modules. Media Lario has designed the ATHENA Assembly Integration and Testing facility to realize the integration process for the flight telescope and has started its construction. The facility consists of a vertical optical bench installed inside a tower with controlled cleanroom conditions. The MAM axis is aligned along gravity and supported on actuators to compensate for gravity deformations. A robot device above the MAM is used for aligning the SPO Mirror modules. The 2.6 m paraboloid mirror that collects the light emitted by a UV source is in final polishing. The alignment system, the cell support and the metrology system for the UV collimator have been qualified and accepted for installation. Details about the optical bench and the status of the facility construction will be presented.

The ATHENA X-ray telescope will be the largest X-ray optics ever built. The ground calibration of this mirror assembly raises significant difficulties due to its unprecedented size, mass and focal length. The VERT-X project aims at developing an innovative calibration system which will be able to accomplish to this extremely challenging task.The design is based on an X-ray parallel beam produced by an X-ray source positioned in the focus of a highly performing X-ray collimator; the beam will be accurately moved by a raster-scan mechanism covering all the ATHENA optics at different off-axis angles. The main driving factor in the VERT-X design is the ATHENA calibration requirement on the accuracy in the HEW measure which is 0.1”, all over the field of view. The VERT-X project, started in January 2019, is financed by ESA and conducted by a consortium that includes INAF together with EIE, Media Lario, BCV Progetti and GPAP.

The optics of ATHENA (Advanced Telescope for High-ENergy Astrophysics) consists of several hundreds of Silicon Pore Optics mirror modules integrated and co-aligned onto a Mirror Assembly Module (MAM). The selected integration process exploits an optical bench to capture the focal plane image of each mirror module when illuminated by an UV plane wave at 218 nm. Each mirror module focuses the collimated beam onto a CCD camera placed at the 12 m focal position of the ATHENA telescope and the acquired point spread function is processed in real time to calculate the centroid position and intensity parameters. This information is used to guide the robot-assisted alignment sequence of the mirror modules. The ATHENA Assembly Integration and Testing (AIT) facility has been designed and is now under construction. It consists of a vertical tower, in which clean room conditions are maintained. Inside the tower, the MAM is supported at ground level on a gravity release system and a robot device above the MAM is used for alignment of the SPO Mirror modules. A paraboloid mirror that collects the light from an ultraviolet point source and generates a single reference plane wave large enough to illuminate the 2.6 m aperture of the X-ray telescope is placed 6 m below the MAM, whereas a CCD camera for the detection of the focused beam is placed at the top of the tower, 12 m above the MAM.

The optics of ATHENA (Advanced Telescope for High-ENergy Astrophysics) – the next high-energy astrophysical mission of the European Space Agency – consists of 678 Silicon Pore Optics mirror modules integrated and co-aligned onto a common supporting structure. The integration process, already proved, exploits an optical bench to capture the focal plane image of each mirror module when illuminated by an ultra-violet plane wave at 218 nm. Each mirror module focuses the collimated beam onto a CCD camera placed at the 12 m focal position of the ATHENA telescope and the acquired point spread function is processed in real time to calculate the centroid position and intensity parameters. This information is used to guide the robot-assisted alignment sequence of the mirror modules. To implement the above process for the entire ATHENA optics, a dedicated vertical optical bench is being designed. The facility consists of a paraboloid mirror that collects the light from an ultraviolet point source and generates a single reference plane wave large enough to illuminate the 2.6 m aperture of the X-ray telescope; at 12 m from the ATHENA optics (focal plane position) a tower will support the CCD camera, where the light from each mirror module is focused. The facility must also allow an alignment accuracy of 1 arcsec for the integration of two mirror modules per day in any arbitrary integration sequence, including the option of removing, re-aligning, or replacing any mirror module. The detailed design of the optical bench and the status of the construction activities are presented.

ATHENA (Advanced Telescope for High-ENergy Astrophysics) is the next high-energy astrophysical mission of the European Space Agency currently planned to be launched in the early 2030s, as part of its Cosmic Vision program, on the scientific topic of “Hot and Energetic Universe”. The optics technology is based on the Silicon Pore Optics (SPO). About 678 SPO mirror modules will have to be integrated and co-aligned onto the optical bench of the Mirror Assembly Module (MAM) of ATHENA. This activity will have to be completed in about two years. Media Lario leads an industrial and scientific team that has developed the process to align and integrate the SPO Mirror module with an accuracy better than 1 arcsec. The process is based on position of the centroid of the point spread function produced by each mirror module when illuminated by a collimated planewave at 218 nm taken at 12 m focal length. Experimental tests, using two SPO mirror modules, and correlation with X-ray measurement at the PANTER test facility in Munich have demonstrated that this process meets the accuracy requirement. It was also demonstrated, that a mirror module can be removed again from the MAM, and re-installed, without compromising the adjacent mirror modules. This technique allows arbitrary integration sequence and integration of two Mirror Modules per day. Moreover, it enables monitoring the telescope point spread function during the whole integration phase.

FLORIS (FLuorescence Imaging Spectrometer) is the single High-Resolution Spectrometer instrument of the FLEX (FLuorescence EXplorer) mission, currently under development by the European Space Agency as the eighth Earth Explorer Mission. The goal of the mission is the monitoring of the chlorophyll fluorescence of plants giving information about their photosynthetic activity. Leonardo Avionics & Space System Division is the prime contractor for the FLORIS Instrument for which Media Lario is manufacturing the QM unit of the spherical mirror included in the High-Resolution Spectrometer (HRSPE), hereafter called HRM mirror. The High-Resolution Mirror is a 250-mm diameter spherical mirror with a radius of curvature of approximately 440 mm. For the mirror substrate, Leonardo has selected the Aluminium alloy AlSi40, a special alloy with 40% Silicon content, coated with a hard polishing layer of Nickel Phosphorus (NiP), deposited by electroless chemical process. The Silicon content allows this special Aluminium alloy to have the same coefficient of thermal expansion (CTE) of the NiP layer, therefore preventing thermal deformations deriving from the bimetallic effect. The mirror structure is light-weighted to approximately 2.8 kg. The required wave-front error of the mirror is better than 0.5 fringes PV, while the surface microroughness has been specified at 0.5 nm RMS due to stringent straylight requirements of the FLORIS instrument. Media Lario has been selected for the mirror development phase because of their experience in the design and manufacturing of AlSi/NiP mirrors demonstrated in the development of the Earth Observation optical payload for small satellites (called STREEGO), based on an AlSi40 TMA telescope. The manufacturing process includes precision diamond turning, optical figuring and super-polishing. The optical coating will be done by Leonardo at their thin-films facility of Carsoli, Italy. Since the recipe prescribes to pre-heat the mirror surface at 100° C, Media Lario will qualify the mirror substrate with -25/+110°C thermal cycles to ensure adequate thermal stability for the coating process.

The ATHENA X-ray observatory is a large-class ESA approved mission, with launch scheduled in 2028. The technology of Silicon Pore Optics (SPO) was selected since 2004 as the baseline for making the X-ray Mirror Assembly. Up to 700 mirror modules to obtain a nested Wolter like optics. The maximum diameter of the shells will be 2.5 m while the focal length is 12 m. The requirements for on-axis angular resolution and effective area at 1 keV are 5 arcsec HEW and 1.4 m2, while the field of view will be 40 arcmin in diameter (50 % vignetting). While in this moment there an on-going effort aiming at demonstrating the feasibility of a so large optics with so stringent scientific requirements, an important aspect to be considered regards the scientific calibrations of the X-ray optics. In this respect, the Point Spread Function and effective area have to be correctly measured and calibrated on-ground at different energies across the entire field of view, with a low vignetting. The approach considered so far foresees the use of a long (several hundreds of meters) facility to allow a full illumination with low divergence of the entire optics module (or at least of large sections of it). The implementation of similar configurations in a completely new facility to be realized in Europe (friendly called "super Panter") or the retrofitting existing facilities like the XRCF at NASA/MSFC are being considered. In both cases the costs and the programmatic risks related to the implementation of these huge facilities, with their special jigs for the alignment of the ATHENA optics, represent important aspects to be considered. Moreover, the horizontal position of the optics to be used in full illumination facilities would determine gravitational deformations, not easy to be removed with actuators or by modeling. In this talk we will discuss a completely different concept, based on the mount of the optics in vertical position and the use of a raster scan of the ATHENA optics with a small (a few cm2 wide) highly collimated (1 arcsec or so) white beam X-ray. This system will allow us to operate a much compact system. The use of a vertical configuration will imply smaller gravitational deformations, that can be controlled with actuators able to compensate them. A proper camera system with a sufficient energy resolution will be able to grant a correct measurement of both PSF and effective area of the Mirror Assembly within the calibration requirements and in a reasonable integration time. Moreover, it may allow us also to perform end-to-end tests using the two flight focal plane instruments of ATHENA. The cost and risks for the implementation would be much lower than for the full illumination systems. The conceptual configuration and preliminary expected performance of the facility will be discussed.

ARIEL (Atmospheric Remote-sensing Infrared Exoplanet Large-survey) has been selected by ESA as the next mediumclass science mission (M4) to be launched in 2028. The aim of the ARIEL mission is to study the atmospheres of a selected sample of exoplanets. The payload is based on a 1-m class telescope ahead of a suite of instruments: two spectrometric channels covering the band 1.95 to 7.80 μm and four photometric channels working in the range 0.5 to 1.9 μm. The production of the primary mirror (M1) is one of the main technical challenges of the mission. A trade-off on the material to be used for manufacturing the 1-m diameter M1 was carried out, and aluminium alloys have been selected as the baseline materials both for the telescope mirrors and structure. Aluminium alloys have demonstrated excellent performances both for IR small size mirrors and structural components, but the manufacturing and thermo-mechanical stability of large metallic optics still have to be demonstrated especially at cryogenic temperatures. The ARIEL telescope will be realized on-ground (1 g and room temperature), but it shall operate in space at about 50 K. For this reason a detailed tolerance analysis was performed to assess the telescope expected performance. M1 is an off-axis section of a paraboloidal mirror and will be machined from a single blank as a stand-alone part. To prove the feasibility of such a large aluminium mirror, a pathfinder mirror program has been started. The prototype has been realized and tested, so far at room temperature, by Media Lario S.r.l.. Cryogenic testing of the prototype will be performed during Phase B1.

Optics for EUV, X-Ray, and Gamma-Ray Astronomy IX : [Proceedings] - SPIE, 2019. - ISBN 97815106293189781510629325 - doi:10.1117/12.2531157 Optics for EUV, X-Ray, and Gamma-Ray Astronomy IX, San Diego, United States, 11 Aug 2019 - 15 Aug 2019; SPIE 9 pp. (2019). doi:10.1117/12.2531157, The Cherenkov Telescope Array (CTA) will be the next generation ground-based observatory for gamma-ray astronomyat very-high energies. It will consist of over a hundred telescopes of different sizes (small, medium, and large) located inthe northern and southern hemispheres. The Italian National Institute of Astrophysics (INAF) contributes to CTAthrough the ASTRI project (Astrofisica con Specchi a Tecnologia Replicante Italiana), whose main aim is to provide aseries of dual-mirror small-sized telescopes (SST-2M ASTRI) and the mirrors for the single-mirror design of themedium-sized telescopes (MST). Both the primary mirror of the SST-2M ASTRI and the mirror of the MST aresegmented, and such segments are realized with cold-slumping technology already used for the mirror facets of MAGIC,a system of two Cherenkov telescopes operating on the Canary Island of La Palma. On the other hand, the secondarymirror of the SST-2M ASTRI is monolithic and is realized with hot-slumping technology. Currently, we have completedthe mirror production for nine SST-2M ASTRI telescopes, which will form the so-called ASTRI Mini-Array. Moreover,we have almost completed also the production of mirrors for two MSTs. In this paper, we present the mirror designs anddescribe the qualification activities that were performed to assess and consolidate the production process. Moreover, wereport on the quality assurance approach we adopted to monitor and verify the production reliability. Finally, we presentthe performance of the produced mirrors and discuss their compliance with the CTA requirements., Published by SPIE

In this paper the design, analysis and development of an aluminum 1-m diameter prototype mirror for the telescope of the ARIEL (Atmospheric Remote-sensing Infrared Exoplanet Large-survey) mission are described. ARIEL has been selected by the European Space Agency (ESA) as the next medium-class science mission (M4) to be launched in 2028. The aim of the ARIEL mission is to study the atmospheres of a selected sample of exoplanets. The payload is based on a 1-m class telescope ahead of a suite of instruments: two spectrometric channels covering the band 1.95 to 7.80 μm without gaps, three photometric channels working in the range 0.5 to 1.2 μm, and a low-resolution spectrometer in the range 1.25 to 1.95 μm. The telescope layout is conceived as an eccentric pupil two-mirror classic Cassegrain configuration coupled to a tertiary off-axis paraboloidal mirror. The telescope will be realized on-ground, i.e. subjected to gravity and at room temperature, but it shall operate in space, at 0 g, and at a temperature of about 50 K. For this reason, the telescope expected “as-built” in-flight performance has to be determined via a detailed thermo-elastic analysis. A trade-off on the material to be used for manufacturing the 1-m diameter primary mirror (M1) was carried out, and aluminum alloys have been selected as the baseline materials for both the telescope mirrors and structure. The use of metals, like aluminum alloys, is nowadays frequently considered for the fabrication of space telescopes observing in the infrared wavelength range. Small-size aluminum parts have been proved to be popular both for IR mirrors and structural components, but the manufacturing and stability of large metallic optics still have to be demonstrated. The production of a large aluminum mirror such as that of ARIEL is a challenge, and to prove its feasibility a dedicated study and development program has been started. A prototype, with the same size of the M1 flight model but a simpler surface profile, has been realized and tested.

A manufacturing technology of mirrors for free-space optical communication is presented: a thin layer of Nickel is deposited on a master and bonded on a light-weighted structure by adhesive. After separation, the master is ready for another cycle. The process is cost-effective because only the master needs to be of optical quality. The structure is machined by traditional tooling, with figure errors compensated by the adhesive. Its curing time defines the process throughput to one mirror per day per master. Several 200 mm-aperture Ritchey-Chretien telescopes have been manufactured and tested.

ATHENA (Advanced Telescope for High-ENergy Astrophysics) is the next high-energy astrophysical mission of the European Space Agency. Media Lario leads an industrial and scientific team that has developed a process to align and integrate more than 700 silicon pore optics mirror modules into the ATHENA X-ray telescope. The process is based on the ultra-violet imaging at 218 nm of each mirror module on the focal plane of a 12 m focal length optical bench. Specifically, the position of the centroid of the point spread function produced by each mirror module when illuminated by a collimated plane is used to align each mirror module. Experimental integration tests and correlation with X-ray measurement at the PANTER test facility in Munich have demonstrated that this process meets the accuracy requirement. This technique allows arbitrary integration sequence and mirror module exchangeability. Moreover, it enables monitoring the telescope point spread function during the integration phase.

A mid-to-high resolution optical payload, named STREEGO, featuring a compact envelope, reduced mass, and competitive cost has been designed to address Earth Observation applications from low Earth orbit (LEO) small satellites. STREEGO is a fully reflective telescope designed for operation at a nominal altitude of 600 km to provide a ground sampling distance (GSD) of 2.75 m, a field of view of about 1° and a modulation transfer function (MTF) greater than 10p at Nyquist frequency (91 cy/mm) with a telescope aperture of 200 mm. A large two-dimensional CMOS sensor with a pixel size of 5.5 μm has been selected in order to obtain the requested GSD with a focal length of 1.2 m, and a signal-to-noise ratio equal to 75. A demonstration model is in the detailed design phase and will be developed, with completion planned by end of 2015. We present a detailed description of the instrument, which, by leveraging on aspheric surfaces and light-weight solutions, achieves remarkable performance in terms of compactness and image quality with less than 25 kg in mass. The optical design is based on a three mirror anastigmat (TMA) configuration whereby the mirrors are realized in metal with the same coefficient of thermal expansion of the structure in order to obtain an athermal design.

The increasing number of Earth Observation missions launched over the last decade has stimulated the development of a large number of satellite instruments able to acquire and deliver rich imageries suitable to support many different applications. Recent advances in electronics, optical manufacturing and remote sensing are now enabling the conception of smaller instruments that could enable new mission concepts at lower costs such as the adoption of satellite constellations for improved temporal resolution. In this paper we present the development of an innovative optical payload named STREEGO suitable for Earth Observation from Low Earth Orbit (LEO) microsatellites. STREEGO is an athermal, fully reflective telescope based on a three mirror anastigmat (TMA) design which features a 200 mm aperture, a focal length of 1.2 m and an across-track Field of View (FoV) of about 2°. Leveraging on a large format two-dimensional CMOS sensor with a pixel size of 5.5 μm, it delivers a nominal modulation transfer function (MTF) of 64% at Nyquist frequency and a ground sampling distance of 2.75 m from an altitude of 600 km. In the design of the instrument detailed stray-light and tolerance analyses were performed and a worst-case thermal model was also developed to ensure that optimal image quality is achieved under operational conditions. After preliminary tests on a Demonstrator Model (DM), an Engineering Model (EM) of the payload with a mass of 20 kg including its electronics and mounting interfaces has been integrated and tested in laboratory and it is now ready to start an environmental test campaign to increase its Technology Readiness Level (TRL). The qualification of the instrument and the results achieved are presented in detail.

ATHENA (Advanced Telescope for High-ENergy Astrophysics) is the next high-energy astrophysical mission selected by the European Space Agency for launch in 2028. The X-ray telescope consists of 1062 silicon pore optics mirror modules with a target angular resolution of 5 arcsec. Each module must be integrated on a 3 m structure with an accuracy of 1.5 arcsec for alignment and assembly. This industrial and scientific team is developing the alignment and integration process of the SPO mirror modules based on ultra-violet imaging at the 12 m focal plane. This technique promises to meet the accuracy requirement while, at the same time, allowing arbitrary integration sequence and mirror module exchangeability. Moreover, it enables monitoring the telescope point spread function during the planned 3-year integration phase.

The Large Millimeter Telescope (LMT) Alfonso Serrano is a 50 m diameter single-dish radio telescope optimized for astronomical observations at wavelengths of about a millimeter. Built and operated by the Instituto Nacional de Astrofisica, Optica y Electronica (INAOE) in collaboration with the University of Massachusetts (UMASS), the telescope is located at the 4600 m summit of volcano Sierra Negra, Mexico. Anticipating the completion of the main reflector, currently operating over a 32 m subaperture, INAOE has contracted Media Lario for the design and manufacturing of a new 2.63 m subreflector that will enable higher efficiency astronomical observations with the entire main reflector surface. The new subreflector manufactured by Media Lario is segmented in 9 smaller panels, one central dome and eight identical petals, assembled and precisely aligned on a steel truss structure that will be connected to the hexapod mounted on the tetrapod head. Each panel was fabricated with Media Lario’s unique laminated technology consisting of front and rear Nickel skins, electroformed from precise molds and bonded to a lightweight Aluminum honeycomb core. The reflecting surface of each panel was given a thin galvanic Rhodium coating that ensures that the reflector survives the harsh environmental conditions at the summit of Sierra Negra during the 30 year lifetime of the telescope. Finally, the 2.63 m subreflector produced by Media Lario was qualified for typical cold night through hot day observation conditions with a maximum RMS error of 24.8 μm, which meets INAOE’s requirements.

The effect of charge recombination on the noise associated with the signal current at the anode of a semiconductor drift detector is studied for both time and amplitude measurements. The analysis is performed by fully taking into account the diffusion of electrons in the semiconductor, the electrostatic induction process that gives rise to the signal, and the correct boundary condition at the anode for the electron density. Both the time variance and the amplitude noise-to-signal ratio are calculated as a function of the filter width for different values of the time constant of the recombination process. A comparison with previous results based on more simplified treatments is also given.

In the framework of an European Space Agency contract, Media Lario Technologies is developing an optical payload for Earth Observation targeted to small satellites. In this paper we present a detailed description of the imager which, by leveraging on aspheric surfaces, bonnet polishing, lightweight materials, an off-the-shelf large format CMOS detector and multispectral filters integrated in the FPA, achieves remarkable image quality with compact volume claim and mass of only 15 kg. The instrument is based on a three mirror anastigmat (TMA) design with an aperture of 200 mm and an F/number of 6. The payload is designed to provide a ground sampling distance (GSD) of 2.75 m for the panchromatic channel at a reference altitude of 600 km, a field of view of 1° and a nominal MTF greater than 60% at Nyquist frequency with a Signal to Noise Ratio (SNR) greater than 100.

The power spectral density of generation–recombination noise in finite-length semiconductors is calculated under the drift–diffusion approximation taking into full account the effect of diffusion on the single-particle correlation. The result is compared with the prediction of the usual approach in which such an effect is not considered. The low frequency behaviour of the power spectral density, its cut-off frequency and the noise variance are studied as a function of the applied voltage and the generation–recombination time constant.

A simplified analytical model for the analysis of the performances of an adaptive optics system is described for application to direct detection free-space optical communication in the atmosphere. The transfer function of the adaptive optics control loop is calculated in the Zernike and Fourier domains for temporal and spatial dependence, respectively, and is used to determine the power spectrum of the corrected wavefront. To illustrate the model, an adaptive optics system is studied for the downlink channel of the free-space optical link operated by the European Space Agency between the ARTEMIS satellite and the Optical Ground Station in Tenerife Island, Spain.

The noise associated with the signal current at the anode of a semiconductor drift detector is evaluated when the electrostatic induction giving rise to the signal is fully taken into account and the correct boundary condition at the anode for the electron density is considered. The consequent signal-to-noise ratio for both time and amplitude measurements is calculated as a function of the filter width and compared with previous results based on more simplified treatments.

One of the approaches that is being tested for the integration of the mirror modules of the advanced telescope for high-energy astrophysics x-ray mission of the European Space Agency consists in aligning each module on an optical bench operated at an ultraviolet wavelength. The mirror module is illuminated by a plane wave and, in order to overcome diffraction effects, the centroid of the image produced by the module is used as a reference to assess the accuracy of the optical alignment of the mirror module itself. Among other sources of uncertainty, the wave-front error of the plane wave also introduces an error in the position of the centroid, thus affecting the quality of the mirror module alignment. The power spectral density of the position of the point spread function centroid is here derived from the power spectral density of the wave-front error of the plane wave in the framework of the scalar theory of Fourier diffraction. This allows the defining of a specification on the collimator quality used for generating the plane wave starting from the contribution to the error budget allocated for the uncertainty of the centroid position. The theory generally applies whenever Fourier diffraction is a valid approximation, in which case the obtained result is identical to that derived by geometrical optics considerations.

A lightweight single-aperture and multi-spectral sensor operating from Visible to LWIR has been designed, manufactured and tested exploiting a Three Mirror Anastigmat (TMA) telescope featuring thin free-form mirrors electroformed from negative masters. Manufacturing complexity is in place only for the master realization, the contribution of which to the sensor cost decreases with the number of replicas. The TMA, suitable for airborne surveillance applications, has F/no. 1.4, focal length 136 mm and field of view 4.3° × 3.1°, and provides two channels, in the MWIR-LWIR and in the visible waveband. The nominal contrast is better than 75% in the visible at 25 cycles/mm. Electroformed 1 mm thick mirrors keep the sensor mass below 3 kg. Stray light and thermo-structural design has been done to comply with airborne conditions.

Media Lario Technologies (MLT) uses its proprietary replication by electroforming technology to manufacture grazing incidence collectors in support of the EUVL technology roadmap. With the experience of more than 20 alpha and preproduction collectors installed to date, and with the development results of the Advanced Cooling Architecture (ACA) for High Volume Manufacturing (HVM) collector generation, we present optical, lifetime, and thermo-optical performance of the grazing incidence collectors, meeting the requirements of HVM scanners for a throughput target of more than 100 wafers per hour. The ruthenium reflective layer of the grazing incidence collector is very forgiving to the hostile environment of the plasma sources, as proven by the installed base with 1-year lifetime expectancy. On the contrary, the multilayer-based collector is vulnerable to Sn deposition and ion bombardment, and the need to mitigate this issue has led to a steady increase of the complexity of the LPP source architecture. With the awareness that the source and collector module is the major risk against the timely adoption of EUVL in HVM, we propose a new paradigm that, by using the field-proven design simplicity and robustness of the grazing incidence collector in both LDP and LPP sources, effectively reduces the risk of both source architectures and improves their reliability.

Media Lario Technologies (MLT) has enabled the Extreme Ultraviolet Lithography (EUVL) roadmap with its grazing incidence collectors installed in all DPP sources since 2006. Furthermore, with several 100 WIF capable production grazing incidence collectors shipped in 2010, MLT is ready to support the start of High Volume Manufacturing (HVM). With a point-source collection efficiency of 25% and 6 kW power loading capability, the 9-shell collector design is capable of delivering 100 W in-band EUV power through the intermediate focus aperture. The customized reflective layer and the debris mitigation technology enable the 1-year lifetime objective under full production operating conditions. Integration of the grazing incidence collector in XTREME technologies' (XT) DPP source attached to ASML's NXE:3100 scanner has provided initial validation of the optical, thermal, and lifetime design objectives. In full HVM regime, we anticipate that the collector power loading will progressively reach 20 kW to enable 500 W inband EUV peak power at intermediate focus. We have started the development of a thermal management design maintaining the current optical stability with a collector power loading of 30 kW, thus meeting the aggressive HVM requirements.

Media Lario Technologies (MLT), leveraging off its unique in-field collector experience, has designed the Grazing Incidence Collector (GIC) for the Sn-fueled Discharge Produced Plasma (DPP) source developed by Philips Extreme UV (PEUV) and XTREME technologies (XT) for High Volume Manufacturing (HVM) deployment. The performance of the HVM GIC described in this work shows a point-source collection efficiency of 24%, and is enabled by an integrated thermal control system designed to ensure optical stability for an absorbed thermal load of 6 kW. The GIC reflective layer has been custom tailored to match the debris mitigation strategy developed and characterized by PEUV and XT, supporting at least a 1-year lifetime proposition of the source-collector module. Leveraging off the experience gained in GIC, MLT is developing the processes to manufacture the Normal Incidence Collector (NIC) for Laser Produced Plasma (LPP) sources. Using its proprietary disruptive replication technology by electroforming, MLT is developing thermal management designs for NIC enabling stable operation at room temperature. This work reports on the performance of (symbol) 150 mm thermally managed NIC demonstrators. The mirror substrates have been integrated with new proprietary thermal management designs that are well suited to the electroformed mirrors. We also report on the reflectivity of the Mo/Si multilayer coated mirror, achieving maximum reflectivity values of 62% and a center wavelength (FWHM) of 13.52 nm, which demonstrates acceptable performance in an LPP NIC application.

The power roadmap for EUVL high volume manufacturing (HVM) exceeds the 200W EUV in-band power at intermediate focus, thus posing more demanding requirements on HVM sources, debris suppression systems and collectors. Starting from the lessons learned in the design and fabrication of the grazing incidence collectors for the Alpha EUVL scanners, Media Lario Technologies is developing HVM optical solutions that enable designed-in lifetime improvements, such as larger source-collector distances, optimized collection efficiency through larger collected solid angles, and customized EUV reflective layers. The optical design of an HVM collector is described together with the selection of the sacrificial ruthenium reflective layer. The water cooling layout of the collector is evolved from the integrated cooling technology developed at Alpha level into an innovative cooling layout that minimizes the thermal gradients across the mirrors and allows controlling the optical performance at the far-field plane. Finally, the evolution of the collector's manufacturing technologies for HVM is discussed. XTREME technologies and Philips Extreme UV support this work by integrating the collector in the complete source collector module (SoCoMo). At system level, each component of the SoCoMo is part of a development and improvement plan leading to a comprehensive system that will fulfill the 200+ W EUV in-band power at intermediate focus.

A number of future X-ray astronomy missions (e.g. Simbol-X, eROSITA) plan to utilize high throughput grazing incidence optics with very lightweight mirrors. The severe mass specifications require a further optimization of the existing technology with the consequent need of proper optical numerical modeling capabilities for both the masters and the mirrors. A ray tracing code has been developed for the simulation of the optical performance of type I Wolter masters and mirrors starting from 2D and 3D metrology data. In particular, in the case of 2D measurements, a 3D data set is reconstructed on the basis of dimensional references and used for the optical analysis by ray tracing. In this approach, the actual 3D shape is used for the optical analysis, thus avoiding the need of combining the separate contributions of different 2D measurements that require the knowledge of their interactions which is not normally available. The paper describes the proposed approach and presents examples of application on a prototype engineering master in the frame of ongoing activities carried out for present and future X-ray missions.

The paper presents the results of an investigation into the thermal and optical characteristics of alpha-type dual-mirror grazing incidence collectors for Extreme Ultra-violet Lithography integrated into a tin-fueled discharge produced plasma source. The performance of the system is assessed at various power levels and temperature conditions. The thermal and the optical data, in particular images at extra-focal planes behind the intermediate focus, are compared to the predictions of the thermo-optical model of the system. The data we present provide verification of the models used to design the collector and validation of the thermo-optical modeling approach for design of future generations of collectors.

A two-reflection optical design for nested X-ray telescopes is described in which the two grazing incidence angles are equal for each ray collected by each mirror, so that the total reflectivity is maximized. A specific design is discussed and its optical performances are compared to a reference type I Wolter optics. In the selected design scenario, a 16% reduction in the number of mirror shells and a 6% increase of the effective area between 1 keV and 10 keV is achieved, along with a small 2.6% decrease of the angular resolution over 12 armin field of view.

Two designs of grazing incidence collectors for EUV lithography are described as alternative solutions to the type I Wolter configuration. The main purposes of the designs are the improvement of collection efficiency and the increase in the flexibility with which the design can be adapted and adjusted to the boundary specifications set by the source and the illuminator. With reference to a specific scenario, examples of these designs and their performances are presented, discussed, and compared to what can be achieved with a Wolter collector. In this scenario, one of the designs offers the possibility to achieve large collection efficiency with a limited number of mirrors as opposed to the Wolter case where high values of the collection efficiency are possible provided the number of mirrors is increased.

A dual-mirror grazing incidence collector produced by Media Lario Technologies was integrated into a high-power, Xefueled gas discharge produced plasma (GDPP) source test stand at XTREME technologies, and tested at power levels responding to the productivity demands of the extreme ultra-violet (EUV) lithography beta exposure systems. The test campaign conducted at different source repetition rates in steady state and transient operating modes provided data for the verification and improvement of the thermo-optical model of the source-DMT-collector system used for the thermooptical design of the collector. The final thermo-optical model of the steady state regime was cross-validated by the numerical solution of the transient tests, which is solely based on the experimental temperature readings. Among the salient results, the cooling system integrated on the collector removed the 1 kW heat load absorbed by the dual-mirror optics, maintaining the temperature of the optics within 20-25 °C temperature range, with an input cooling water temperature of 18.6 °C. Additional validation came from tests performed on a single-mirror collector in a vacuum based, thermo-optical visible test bench installed at Media Lario Technologies, which provided a closed loop validation of the thermal budget, finite element model, and Monte Carlo ray tracing optical prediction.

A design of a two-reflection mirror for nested grazing-incidence optics is proposed in which maximum overall reflectivity is achieved by making the two grazing-incidence angles equal for each ray. The design is proposed mainly for application to nonimaging collector optics for extreme-ultraviolet microlithography where the radiation emitted from a hot plasma source needs to be collected and focused on the illuminator optics. For completeness, the design of a double- reflection mirror with equal reflection angles is also briefly outlined for the case of an object at infinity for possible use in x-ray applications.

The design and optimization of nested grazing incidence collectors for extreme ultra-violet lithography is discussed taking into account the boundary conditions set by optical, mechanical, thermal, and manufacturing requirements. The trend of the collection efficiency as a function of numerical the aperture at the intermediate focus, the source-optics distance and the focal length is presented. The effect of the thickness of the mirrors on the optical performance and stability under thermal load is also discussed as a specific example involving optical, thermal and manufacturing issues. As an introduction to the discussion of the design and optimization of the collector, a theoretical maximum limit for the collection efficiency is studied as a function of collected solid angle and system etendue.

A simple genetic algorithm for global optimisation of the reflectivity of multilayer coatings in the extreme ultra-violet and X-ray wavelength ranges has been implemented as a software tool. The genetic algorithm identifies the best-performing multilayer among a population of solutions that evolves while random mutations are applied to the thickness of the layers. The tool is designed for maximising the reflectivity either over a wavelength range at fixed incident angle or over a range of incident directions at fixed energy. The algorithm has been preliminarily tested on two specific applications: a Pt/C multilayer for hard X-rays applications in astrophysics and cosmology and a Mo/Si coating prominent to next generation lithography at 13.5 nm. The results of the analyses are compared to the performances achievable with periodic multilayers and traditional supermirrors.© (2004) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A 2.5 Gb/s optical link at 1550 nm over a distance of 1.1 km has been demonstrated between two identical terminals by using standard commercial optoelectronic devices without any optical amplification and with direct optical coupling into the receiver fiber optics pigtail. Each terminal consists of one 200 mm diameter light-weight Ritchey-Chretien telescope, obtained through electroformed nickel replication technology and used for both reception and transmission. The terminal is a first phase demonstrator towards lean and cost effective design for low and medium distance inter-satellite links at high data rate. Although a tracking system has not yet been implemented, the system can work continuously up to several hours with a cumulative bit error rate lower than 10 -9 , even in heavy rain conditions.

The adaptive secondary for the MMT is the first mirror of its kind. It was designed to allow the application of wavefront corrections (including tip-tilt) directly at the secondary mirror location. Among the advantages of such a choice for adaptive optics operation are higher throughput, lower emissivity, and simpler optical setup. Furthermore, this specific implementation provides capabilities that are not found in most correctors including internal position feedback, large stroke (to allow chopping) and provision for absolute position calibration. The mirror has now been used at the MMT during several runs where it has performed reliably. In this paper we discuss the mirror operation and AO performance achieved during these runs in which the adaptive secondary has been operating in conjunction with a Shack-Hartmann wavefront sensor as part of the MMT adaptive optics system. In particular we mention a residual mirror position error due to wind buffeting and other errors of ≈ 15 nm rms surface and a stable closed loop operation with a 0dB point of the error transfer function in the range 20-30 Hz limited mainly by the wavefront sensor maximum frame rate. Because of the location of the adaptive secondary with respect to the wavefront sensor camera, reimaging optics are required in order to perform the optical interaction matrix measurements needed to run the AO loop. This optical setup has been used in the lab but not replicated at the telescope so far. We will discuss the effects of the lack of such an internal calibration on the AO loop performances and a possible alternative to the lab calibration technique that uses directly light from sky objects.

The adaptive secondary for the MMT (called MMT336) is the first mirror of its kind. It was designed to allow the application of wavefront corrections (including tip-tilt) directly at the secondary mirror location. Among the advantages of such a choice for adaptive optics operation are higher throughput, lower emissivity, and simpler optical setup. The mirror also has capabilities that are not found in most correctors including internal position feedback, large stroke (to allow chopping) and provision for absolute position calibration. The 336 actuator adaptive secondary for MMT has been used daily for over one year in our adaptive optics testing facility which has built confidence in the mirror operation and allowed us to interface it to the MMT adaptive optics system. Here we present the most recent data acquired in the lab on the mirror performance. By using interferometer measurements we were able to achieve a residual surface error of approximately 40nm rms. Coupling the mirror with a Shack-Hartmann wavefront sensor we obtained a stable closed loop operation with a -3dB closed loop bandwidth of approximately 30Hz limited by the wavefront sensor frame rate. We also present some preliminary results that show a 5Hz, 90% duty cycle, ±5 arcsec chopping of the mirror. Finally the experience gained and the problems encountered during the first light adaptive optics run at the telescope will be briefly summarized. A more extensive report can be found in another paper also presented at this conference.

Massimiliano RossiGiuseppe BorghiMedia Lario TechnologiesLocalita PascoloI-23842 Bosisio Parini (LC), ItalyIain A. NeilScotOptixChemin du Martinet 4CCH-1291 Commugny (Vaud), SwitzerlandGiuseppe ValsecchiPaolo ZagoFabio E. ZocchiMedia Lario TechnologiesLocalita PascoloI-23842 Bosisio Parini (LC), ItalyE-mail: fabio.zocchi@media-lario.comAbstract. A lightweight, single-aperture, and multispectral imaging sys-tem operating from visible to long wavelength infrared has been manufac-tured and tested based on an innovative three-mirror anastigmat opticaldesign. The complex off-axis aspherical toroidal mirrors of the opticshave been obtained by electroforming replication from masters havinga shape opposite to the mirror shape and manufactured as stand-aloneparts by using five-axis single-point diamond turning. The technology isextendible to full free-form optics without any process modificationenabling affordability of complex optics since multiple identical copies ofthe mirrors can be produced from each master. Moreover, thin (∼1 mm)electroformed mirrors keep the imaging system mass less than 3 kg. Withan effective focal length of 136 mm, the system is suitable for airbornesurveillance applications and provides a full aperture F∕ of 1.4, a fieldof view of 4.3×3.1 deg, and a nominal contrast better than 75% in thevisible waveband at 25 cycles∕mm. A beam splitter can be accommo-dated to provide two separated channels for two or more spectral wave-bands. Stray light and thermostructural design has been performed tocomply with airborne applications. Experimental results demonstratethe feasibility of the technology, although process improvements arerequired to reach the extremely demanding theoretical performance ofthe optical design.

A formula is derived for the total width of the angle spread function in an imaging optical system, the performance of which is degraded by surface roughness. The derivation is done in the framework of the scalar theory of diffraction, but it does not rely on the small roughness approximation. The contribution of scattering from surface roughness to the total width of the angle spread function is found to depend only on the variance of the roughness slope. It is also shown that the common rule of obtaining the total width of the angle spread function as a square sum of the pure scattering component and the pure specular component is actually incorrect and does not fully account for the contribution of the specular component.

Two designs of grazing incidence collectors for extreme ultraviolet (EUV) lithography are described as alternative solutions to the type-I Wolter configuration. The main purposes of the designs are the improvement of collection efficiency and the increase in flexibility with which the design can be adapted and adjusted to the boundary specifications set by the source and the illuminator. With reference to a specific scenario, examples of these designs and their performances are presented, discussed, and compared to what can be achieved with a Wolter collector. In this scenario, one of the designs offers the possibility to achieve large collection efficiency with a limited number of mirrors, as opposed to the Wolter case where high values of the collection efficiency are possible, provided the number of mirrors is increased.

Industrial applications require suitable monitoring systems able to identify any decrement in the production efficiency involving economical losses. The information coming from a general purpose monitoring system can be usefully exploited to implement a sensorless instrument monitoring an AC motor drive and a diagnostic tool providing useful risk coefficients. The method is based on a complex digital processing of the line signals acquired by means of a virtual instrument. In this paper a genetic algorithm, implemented in a Mathcad environment, performs the evaluation of the risk indexes from the processed line signals. The combination of genetic algorithms and neural network is also investigated as a promising possibility for the development of a reliable diagnostic tool. The risk coefficients derived from this approach are evaluated, discussed and compared to other indexes - in particular fuzzy indexes - introduced by the authors in previous papers.