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 mirror assembly of the ESA New -Advanced Telescope for High-ENergy Astrophysics (New-ATHENA) will be the largest X-ray optics ever built. Indeed, its unprecedented size, mass and focal length create great difficulties for the ground calibration. The VERT-X project aims at developing an innovative calibration facility which will be able to accomplish to this extremely challenging task. The design is based on a 2.5 cm 2 parallel beam produced by an X-ray source positioned in the focus of a highly performing collimator. In order to cover the whole mirror, the beam will be accurately moved by a raster-scan with the capability to tilt up to 3 degrees in order to test the off-axis performance and the out of field stray-light. The whole system is enclosed in a cylindrical vacuum chamber about 20m high and with a diameter ranging from 7 to 4m. By design, VERT-X will be able to measure the New-ATHENA mirror half energy width (HEW) with a precision of 0.1", all over the field of view, with the source size, the collimator error and the raster scan tracking accuracy being the most important terms of the error budget. The VERT-X project, started in 2018, is financed by ESA and conducted by a consortium that includes INAF together with EIE, Media Lario, BCV Progetti and Apogeo Space. This paper presents the current state of the development and manufacturing of the most critical systems of the facility, namely the raster-scan mechanism and the source-collimator vertical assembly.
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 bestperforming 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.
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