Ultra light-weight and high-resolution X-ray mirrors using DRIE and X-ray LIGA techniques for space X-ray telescopes

Ezoe, Yuichiro; Mitsuishi, Ikuyuki; Takagi, Utako; Koshiishi, Masaki; Mitsuda, Kazuhisa; Yamasaki, Noriko Y.; Ohashi, T.; Kato, Fumiki; Saito, Susumu; Riveros, Raul E.; Yamaguchi, Hitomi; Fujihira, Shinya; Kanamori, Yoshiaki; Morishita, Kohei; Nakajima, Kazuo; Maeda, Ryutaro

doi:10.1007/s00542-009-0981-4

Cited by 54 publications

(43 citation statements)

References 14 publications

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“…Figure 45 (right panel) shows a micrograph picture of the channel structure of a square-packed MPO plate. Ezoe et al (2009) reported using micromachining technologies to etch the curvilinear micropore sidewalls through a thin silicon wafer for use as reflecting surfaces. As with the MPOs, two such wafers deformed to different curvatures of radii can be stacked to work in the Wolter geometry.…”

Section: Optical Elementsmentioning

confidence: 99%

Imaging Plasma Density Structures in the Soft X-Rays Generated by Solar Wind Charge Exchange with Neutrals

et al. 2018

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Both heliophysics and planetary physics seek to understand the complex nature of the solar wind's interaction with solar system obstacles like Earth's magnetosphere, the ionospheres of Venus and Mars, and comets. Studies with this objective are frequently conducted with the help of single or multipoint in situ electromagnetic field and particle observations, guided by the predictions of both local and global numerical simulations, and placed in con- text by observations from far and extreme ultraviolet (FUV, EUV), hard X-ray, and energetic neutral atom imagers (ENA). Each proposed interaction mechanism (e.g., steady or transient magnetic reconnection, local or global magnetic reconnection, ion pick-up, or the KelvinHelmholtz instability) generates diagnostic plasma density structures. The significance of each mechanism to the overall interaction (as measured in terms of atmospheric/ionospheric loss at comets, Venus, and Mars or global magnetospheric/ionospheric convection at Earth) remains to be determined but can be evaluated on the basis of how often the density signatures that it generates are observed as a function of solar wind conditions. This paper reviews efforts to image the diagnostic plasma density structures in the soft (low energy, 0.1-2.0 keV) X-rays produced when high charge state solar wind ions exchange electrons with the exospheric neutrals surrounding solar system obstacles. The introduction notes that theory, local, and global simulations predict the characteristics of plasma boundaries such the bow shock and magnetopause (including location, density gradient, and motion) and regions such as the magnetosheath (including density and width) as a function of location, solar wind conditions, and the particular mechanism operating. In situ measurements confirm the existence of time-and spatial-dependent plasma density structures like the bow shock, magnetosheath, and magnetopause/ionopause at Venus, Mars, comets, and the Earth. However, in situ measurements rarely suffice to determine the global extent of these density structures or their global variation as a function of solar wind conditions, except in the form of empirical studies based on observations from many different times and solar wind conditions. Remote sensing observations provide global information about auroral ovals (FUV and hard X-ray), the terrestrial plasmasphere (EUV), and the terrestrial ring current (ENA). ENA instruments with low energy thresholds (∼ 1 keV) have recently been used to obtain important information concerning the magnetosheaths of Venus, Mars, and the Earth. Recent technological developments make these magnetosheaths valuable potential targets for high-cadence wide-field-of-view soft X-ray imagers.Section 2 describes proposed dayside interaction mechanisms, including reconnection, the Kelvin-Helmholtz instability, and other processes in greater detail with an emphasis on the plasma density structures that they generate. It focuses upon the questions that remain as yet unanswered, such as the significanc...

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Section: Optical Elementsmentioning

confidence: 99%

Imaging Plasma Density Structures in the Soft X-Rays Generated by Solar Wind Charge Exchange with Neutrals

et al. 2018

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“…, that is, structures with a large height/width ratio, have found many applications 1,2 such as X-ray gratings 3 , gas chromatography columns 4 , magnetic coils 5 , X-ray telescopes 6 , micro-gears 7 , micro-capacitors with highaspect-ratio (HAR) cantilevers 8 , and micromechanical and microoptical elements 9,10 . These structures exhibit aspect ratios (ARs) of over 10 and almost vertical sidewalls, making them much more challenging to develop than the structures typically used in planar technology with moderate ARs of 1 to 2.…”

Section: High-aspect-ratio Microstructures (Harms)mentioning

confidence: 99%

“…Furthermore, it will also result in an increase in optical losses in the development of the proposed PNFs. To prevent this, silicon cryo-etch has been used with an SF 6 :O 2 plasma 16 . This method uses low temperatures (typically below − 100°C) at which a passivating layer of SiO x F y is formed.…”

Section: Silicon-based Masters and Mouldsmentioning

confidence: 99%

“…Positive slope sidewalls were obtained in order to facilitate the later demoulding of the structures. A sidewall angle of 88.1°± 0.6°was obtained by controlling the process parameters (mainly temperature and SF 6 :O 2 ratio). Defects were not observed at the boundary between the two etching steps at the nanostructures or in the transition between the microand nanostructures (Figure 5e).…”

Section: Cryo-etchmentioning

confidence: 99%

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High-aspect-ratio nanoimprint process chains

et al. 2017

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Different methods capable of developing complex structures and building elements with high-aspect-ratio nanostructures combined with microstructures, which are of interest in nanophotonics, are presented. As originals for subsequent replication steps, two families of masters were developed: (i) 3.2 μm deep, 180 nm wide trenches were fabricated by silicon cryo-etching and (ii) 9.8 μm high, 350 nm wide ridges were fabricated using 2-photon polymerization direct laser writing. Both emerging technologies enable the vertical smooth sidewalls needed for a successful imprint into thin layers of polymers with aspect ratios exceeding 15. Nanoridges with high aspect ratios of up to 28 and no residual layer were produced in Ormocers using the micromoulding into capillaries (MIMIC) process with subsequent ultraviolet-curing. This work presents and balances the different fabrication routes and the subsequent generation of working tools from masters with inverted tones and the combination of hard and soft materials. This provides these techniques with a proof of concept for their compatibility with high volume manufacturing of complex micro-and nanostructures.Keywords: cryo-etching; direct 6 write laser lithography; high aspect ratio; moulding; nanoimprint lithography; Ormocer; photonic nanofences; 2-photon polymerization INTRODUCTION High-aspect-ratio microstructures (HARMS), that is, structures with a large height/width ratio, have found many applications 1,2 such as X-ray gratings 3 , gas chromatography columns 4 , magnetic coils 5 , X-ray telescopes 6 , micro-gears 7 , micro-capacitors with highaspect-ratio (HAR) cantilevers 8 , and micromechanical and microoptical elements 9,10 . These structures exhibit aspect ratios (ARs) of over 10 and almost vertical sidewalls, making them much more challenging to develop than the structures typically used in planar technology with moderate ARs of 1 to 2. They are therefore characterized by an intermediate state between two-and threedimensional (2D and 3D), that is, a 2D planar design that is extended into the vertical dimension and often called . There are several methods to produce HAR structures on typical planar substrates, most of them relying on the anisotropy of subtractive pattern transfer of a low AR masking layer into an underlying resist or substrate, that is, by using mask based ultraviolet (UV)-photolithography (PL) with an AR up to 5, silicon etching (for example, dry etching) with an AR up to 20, and direct write laser lithography (DWL) and X-ray lithography with ARs 420 (Refs. 12-15). These methods are continually being improved to produce a higher AR and smaller lateral dimensions. Furthermore, they are enlarged by new techniques that are often subsets of etching processes with different advantages and disadvantages. One of those challenges is the suitability for submicron and nanopatterning, that is, structures with lateral sizes much smaller than 1 μm and the possibility to combine micro-with nanostructures in the same material.There are three main approaches: (1)...

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“…The final type is our micromachined X-ray optics, which utilizes tiny micro pores through a thin silicon wafer for X-ray mirrors (Ezoe et al 2010). Because the narrow micro pores enabled by the microelectromechanical systems (MEMS) technologies, this can be one of the lightest X-ray telescopes ever achieved.…”

Section: Introductionmentioning

confidence: 99%

First X-ray imaging with a micromachined Wolter type-I telescope

et al. 2016

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be a new probe to investigate chemical compositions of planetary atmospheres, surfaces of planets, moons or asteroids and high energy particles in planetary magnetospheres. A potential future Japanese exploration to Jupiter needs a light-weight (<10 kg) X-ray imager in order to capture X-ray auroras from Jupiter . However, limited resources, i.e., mass, power, size, have hindered exploration satellites from carrying a good angular resolution and large effective area X-ray telescope.Wolter type-I telescopes have been widely used in X-ray astronomy. X-rays are doubly reflected upon paraboloid and hyperboloid mirrors, to minimize aberrations (Wolter 1952). A few to hundreds of mirrors are conically nested to increase the effective area. Each mirror is fabricated individually with either polishing of thick mirror substrates, replication of precisely fabricated mandrels, or thermal forming of thin aluminum foils. However, these mirrors have to be heavy when a high angular resolution is sought for Bavdaz et al. (2004). Furthermore, the lightest aluminum foil mirror approximates ideal mirror surfaces with cones, which degrades the angular resolution to 10 arcmin under a short focal length less than 1 m. Therefore, a new mirror fabrication technology is needed for future X-ray astronomy missions as well as planetary explorations.A possible solution is micropore optics (Frazer 1997). Sidewalls of micro pores whose width is typically of the order of 10 to 100 µm are used for X-ray mirrors. The mirror thickness can be extremely thin, of the order of 100 µm to 10 mm. The micropore optics can thus be ultralight weight. Three types of micropore optics are proposed and being developed.The first type is silicon pore optics (SPO) (Bavdaz et al. 2004(Bavdaz et al. , 2010 which is composed of flat silicon wafers with groove structures as mirrors. The wafers are stacked and elastically bent into a conical shape. This type is being developed aiming at an angular resolution of ∼10 arcsec for the future gigantic X-ray astronomy satellite Athena. 1 1 http://www.the-athena-x-ray-observatory.eu.Abstract A light-weight Wolter type-I telescope for future space X-ray observations is prototyped by using micromachining technologies. Curvilinear micro pores with a width of 20 µ m are fabricated with deep reactive ion etching. Sidewalls of the pores are smoothed with high temperature annealing. Then, two wafers are deformed to different curvature radii, 1000 and 333 mm. The two wafers are aligned using parallel X-ray beams which are dominated by Al-K α line at 1.49 keV. High angular and positional accuracies of the order of arcsec and µm are achieved using movable stages. The first clear X-ray focusing is confirmed. Its angular resolution is 4.1 arcmin in full width half maximum while it is at least 92 arcmin in half power width. The effective area is 19.0 mm 2 which is ∼5 times smaller than a model calculation. We discuss causes of the degraded angular resolution and effective area and also future improvements.

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Ultra light-weight and high-resolution X-ray mirrors using DRIE and X-ray LIGA techniques for space X-ray telescopes

Cited by 54 publications

References 14 publications

Imaging Plasma Density Structures in the Soft X-Rays Generated by Solar Wind Charge Exchange with Neutrals

Imaging Plasma Density Structures in the Soft X-Rays Generated by Solar Wind Charge Exchange with Neutrals

High-aspect-ratio nanoimprint process chains

First X-ray imaging with a micromachined Wolter type-I telescope

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