G. Borghi

Design and development of the optics system for the NHXM Hard X-ray and Polarimetric Mission

The New Hard X-ray Mission (NHXM) Italian project will be operated by 2016. It is based on 4 hard X-ray optics modules, each formed by 60 evenly spaced multilayer coated Wolter I mirror shells. For the achievement of a long focal length (10 m) an extensible bench is used. The pseudo-cylindrical Wolter I monolithic substrates where the multilayer coating is applied will be produced using the Ni electroforming replica approach. For three of the four mirror modules the focal plane will host a hybrid a detector system, consisting in the combination of a Si-based low energy detector (efficient from 0.5 up to ~ 15 keV) , on top of a high energy CdTe pixellated detector (efficient from 10 keV up to ~ 80 keV); the two cameras will be surrounded by both a passive shield and an anticoincidence shield. The total on axis effective area of the three telescopes at 1 keV and at 30 kev is of 1500 cm2 and 350 cm2 respectively. The angular resolution requirement is better than 20 arcsec HEW at 30 keV, while the Field of View at 50% vignetting is 12 arcmin (diameter). The payload is finally completed with the fourth telescope module, that will have as a focal plane detector a high sensitivity imaging photoelectric polarimetric system, operating from 2 up to 35 keV. In this paper, after an overview of the mission configuration and its scientific goals, we report on the design and development of the multilayer optics of the mission, based on thin replicated Ni mirror shells.

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...

Electroformed off-axis toroidal aspheric three-mirror anastigmat multispectral imaging system

Abstract. A lightweight, single-aperture, and multispectral imaging system operating from visible to long wavelength infrared has been manufactured and tested based on an innovative three-mirror anastigmat optical design. The complex off-axis aspherical toroidal mirrors of the optics have been obtained by electroforming replication from masters having a shape opposite to the mirror shape and manufactured as stand-alone parts by using five-axis single-point diamond turning. The technology is extendible to full free-form optics without any process modification enabling affordability of complex optics since multiple identical copies of the mirrors can be produced from each master. Moreover, thin (∼1  mm) electroformed mirrors keep the imaging system mass less than 3  kg. With an effective focal length of 136 mm, the system is suitable for airborne surveillance applications and provides a full aperture F/# of 1.4, a field of view of 4.3×3.1  deg, and a nominal contrast better than 75% in the visible waveband at 25  cycles/mm. A beam splitter can be accommodated to provide two separated channels for two or more spectral wavebands. Stray light and thermostructural design has been performed to comply with airborne applications. Experimental results demonstrate the feasibility of the technology, although process improvements are required to reach the extremely demanding theoretical performance of the optical design.

Thin gold layer in NiCo and Ni electroforming process: optical surface characterization

Mandrel replication by NiCo electroforming is an upgrade of the well-suited X-ray mirrors manufacturing process with pure Nickel. In this process, a Gold layer deposited on the mandrel acts as release agent and, at the same time, as reflective coating. To increase the optical performances of X-ray mirrors, the replicated optical surface is meant to reproduce the smooth topography of the mandrel: a surface degradation is commonly observed, indeed. A factor leading to surface smoothness worsening can be the spontaneous roughness growth of the Gold layer itself; therefore, the optical quality of the reflecting surface might be improved by optimizing the Gold layer thickness. A preliminary study, aimed at investigating the effects of Gold thickness reduction (< 100 nm Vs. the usual 200 nm), had already been dealt in the spectral range 0.02-1000 μm: measurements performed on flat electroformed samples showed that the Gold thickness reduction chiefly affects the roughness around 1 μm. Here we presents a study of the effectiveness of a Gold layer with reduced (< 100 nm) thickness in the NiCo X-ray mirrors electroforming, aimed at surface micro-roughness mitigation. The characterization, in the spectral range 0.02-1000 μm, of 3 X-ray mirrors manufactured utilizing Gold layers with different thickness values from a flight mandrel is reported. The performed investigation is organized as follows: (a) characterization of the flight mandrel; (b) dependence of the micro-roughness from different Gold layers thicknesses supported by XRD study; (c) comparison of the micro-roughness of mirrors manufactured in NiCo in Ni, with the same Gold layer thickness. As a conclusive remark the effects of the Gold layer thinning on the angular degradation at high energy are reported.

Design and development of the SIMBOL-X hard x-ray optics

The SIMBOL-X formation-flight X-ray mission will be operated by ASI and CNES in 2014, with a large participation of the French and Italian high energy astrophysics scientific community. Also German and US Institutions are contributing in the implementation of the scientific payload. Thanks to the formation-flight architecture, it will be possible to operate a long (20 m) focal length grazing incidence mirror module, formed by 100 confocal multilayer-coated Wolter I shells. This system will allow us to focus X-rays over a very broad energy band, from 0.5 keV up to 80 keV and beyond, with more than two orders of magnitude improvement in angular resolution (20 arcsec HEW) and sensitivity (0.5 µCrab on axis @30 keV) compared to non focusing detectors used so far. The X-ray mirrors will be realized by Ni electroforming replication, already successfully used for BeppoSAX, XMM-Newton, and JET-X/SWIFT; the thickness trend will be about two times less than for XMM, in order to save mass. Multilayer reflecting coatings will be implemented, in order to improve the reflectivity beyond 10 keV and to increase the field of view 812 arcmin at 30 keV). In this paper, the SIMBOL-X optics design, technology and implementation challenges will be discussed; it will be also reported on recent results obtained in the context of the SIMBOL-X optics development activities.

MPR: Innovative 3D free-form optics profilometer

This paper presents the huge advance in metrology represented by a new free-form profilometer, the Profilometer/Rotondimeter (MPR-700). The MPR-700 is a 3D metrological machine capable to measure quasicylindrical and free-form normal incidence optics maintaining the 2D measuring error below 40 nm at 2σ up to a length of 700 mm. The key to success of MPR is its innovative detection system design that boasts remarkable advantages in the positioning error reduction and to the instantaneous subtraction of the dynamical error. These characteristics make the MPR extremely precise and accurate, insomuch that measurements can be acquired in flight at high speed maintaining the measuring performances. The main advantage of the MPR design is the capability to couple the measuring quality offered by one-dimensional profilometer to the opportunity to the three-dimensional motion of a 3D machines. Here we present the MPR design and the results obtained on single profiles measurements and 3D shape reconstruction for optics of different geometry.

The optics system of the New Hard X-ray Mission: status report

The New Hard X-ray Mission (NHXM) is a space X-ray telescope project focused on the 0.2 to 80 keV energy band, coupled to good imaging, spectroscopic and polarimetry detectors. The mission is currently undergoing the Phase B study and it has been proposed to ESA as a small-size mission to be further studied in the context of the M3 call; even if the mission was not downselected for this call, its study is being continued by ASI. The required performance is reached with a focal length of 10 m and with four mirror modules, each of them composed of 70 NiCo electroformed mirror shells. The reflecting coating is a broadband graded multilayer film, and the focal plane is mounted onto an extensible bench. Three of the four modules are equipped with a camera made of two detectors positioned in series, a Silicon low energy detector covering the range 0.2 to 15 keV and a high energy detector based on CdTe sensitive from 10 keV up to 120 keV. The fourth module is dedicated to the polarimetry to be performed with enhanced imaging capabilities. In this paper the latest development in the design and manufacturing of the optics is presented. The design has been optimized in order to increase as much as possible the effective area in the high-energy band. The manufacturing of the mirror shells benefits from the latest development in the mandrel production (figuring and polishing), in the multilayer deposition and in the integration improvements.

The optics system of the New Hard X-ray Mission: design and development

The New Hard X-ray Mission (NHXM) project will be operated by 2016 and is currently undergoing the Phase B study. It is based on 4 hard X-ray optics modules, each formed by 60 evenly spaced multilayer coated Wolter I mirror shells. An extensible bench is used to reach the 10 m focal length. The Wolter I monolithic substrates with multilayer coating are produced in NiCo by electroforming replication. Three of the mirror modules will host in the focal plane a hybrid a detector system (a soft X-ray Si DEPFET array plus a high energy CdTe detector). The detector of the fourth telescope will be a photoelectric polarimeter with imaging capabilities, operating from 2 up to 35 keV. The total on axis effective area of the three telescopes at 1 keV and 30 kev is of 1500 cm2 and 350 cm2 respectively, with an angular resolution of 20 arcsec HEW at 30 keV. In this paper we report on the design and development of the multilayer optics of the mission, based on thin replicated Ni mirror shells.

Technologies for manufacturing of high angular resolution multilayer coated optics for the New Hard X-ray Mission

In the frame of the technology development to be used for the Optical Payload of next future X-ray missions (such as e.g. New Hard X-ray Mission-ASI), a new set of manufacturing techniques were finalized by Media Lario Technologies (MLT), in collaboration with the Italian Space Agency (ASI) and the Brera Astronomical Observatory (INAF/OAB). The set of new technologies includes master manufacturing machines and processes, electroforming method, a vertical optical bench and metrology machines to support manufacturing and integration of mirrors. A magnetron sputtering PVD machine was upgraded and a Pt/C development study has been performed on the basis of the W/Si results obtained in the first phase of the study. New manufacturing technologies for highly accurate masters were developed and tested by mean of two full-size masters together with several dummies. A number of ultrathin Nickel-Cobalt focusing mirrors were manufactured via galvanic replication process from the masters and coated with Pt/C multilayer. Tests on substrate material, roughness and shape of the shell together with analysis on specimens were performed. Tests with AFM and XRR supported the development of the Pt/C multilayer which is the enabling technology for focusing high energy X-Rays. Several mirror shells were integrated into two demonstrator modules to assess the whole manufacturing process up to optical payload integration. The summary of the results from manufacturing and testing of specimens and mirror shells is reported in this paper together with a description of the technologies now available at MLT.

Design and development of the multilayer optics for the new hard x-ray mission

The New Hard X-ray Mission (NHXM) project will be operated by 2017 and is currently undergoing a Phase B study, under the coordination of the Italian Space Agency (ASI). The project is being proposed by an international team in the context of the ESA Call CV M3 as a Small Mission program, with a large Italian participation. It is based on 4 hard X-ray optics modules, each formed by 60 evenly spaced multilayer coated Wolter I mirror shells. An extensible bench is used to reach the 10 m focal length. The Wolter I monolithic substrates with multilayer coating are produced in NiCo by electroforming replication. Three of the mirror modules will host in the focal plane a hybrid a detector system (a soft X-ray Si DEPFET array plus a high energy CdTe detector). The detector of the fourth telescope will be a photoelectric polarimeter with imaging capabilities, operating from 2 up to 35 keV. The total on axis effective area of the three telescopes at 1 keV and 30 kev is of 1500 cm2 and 350 cm2 respectively, with an angular resolution of 20 arcsec HEW at 30 keV. In this paper we report on the design and development of the multilayer coated X-ray mirrors based on NiCo shells.