Masaki Koshiishi

Micropore x-ray optics using anisotropic wet etching of (110) silicon wafers

To develop x-ray mirrors for micropore optics, smooth silicon (111) sidewalls obtained after anisotropic wet etching of a silicon (110) wafer were studied. A sample device with 19 microm wide (111) sidewalls was fabricated using a 220 microm thick silicon (110) wafer and potassium hydroxide solution. For what we believe to be the first time, x-ray reflection on the (111) sidewalls was detected in the angular response measurement. Compared to ray-tracing simulations, the surface roughness of the sidewalls was estimated to be 3-5 nm, which is consistent with the atomic force microscope and the surface profiler measurements.

Evaluation of the soft x-ray reflectivity of micropore optics using anisotropic wet etching of silicon wafers

The x-ray reflectivity of an ultralightweight and low-cost x-ray optic using anisotropic wet etching of Si (110) wafers is evaluated at two energies, C K(alpha)0.28 keV and Al K(alpha)1.49 keV. The obtained reflectivities at both energies are not represented by a simple planar mirror model considering surface roughness. Hence, an geometrical occultation effect due to step structures upon the etched mirror surface is taken into account. Then, the reflectivities are represented by the theoretical model. The estimated surface roughness at C K(alpha) (approximately 6 nm rms) is significantly larger than approximately 1 nm at Al K(alpha). This can be explained by different coherent lengths at two energies.

Design and Fabrication of a MEMS X-ray Optic using Anisotropic Wet Etching of Si Wafers

In this paper, we report on the development of X-ray optics using anisotropic wet etching of silicon wafers. Both X-ray mirrors and an optics mount are fabricated fully using the MEMS technologies

A Micromachined X-Ray Collector for Space Astronomy

A novel micromachined X-ray collector using anisotropically etched Si (111) planes as X-ray mirrors for future astronomical missions is reported. Mirrors, fabricated using dynashock-type ultrasonic waves, have very smooth surfaces with an rms roughness of nm or less. After the etching, mirror chips were cut from the wafer with a dicing machine and adhered to a mount formed by deep reactive ion etching, in order to collect parallel X-ray beam (0100 mm) on a tiny focus (phi 4 mm). The first light image was successfully obtained at Al Kalpha 1.49 keV in a ISAS 30 m-long beam line.

The first light of a single-stage MEMS x-ray optic

The first light of a ultra-lightweight and low-cost micro-pore X-ray optic utilizing MEMS (Micro Electro Mechanical Systems) technologies is reported. Our idea is to use silicon (111) planes appeared after anisotropic wet etching of silicon wafers. As a first step to Wolter type-1 optics, a single-stage optic with a focal length of 750 mm and a diameter of 100 mm was designed for energies below 2 keV. The optic consists of 218 mirror chips for X-ray reflection and an optic mount for packing these chips. Design parameters and required fabrication accuracies were determined with numerical simulations. The fabricated optic satisfied these accuracies and its imaging quality was measured at the ISAS X-ray beam line at Al Kα 1.49 keV. A focused image was successfully obtained. The measured image size of ~4 mm was consistent with the chip sizes. The estimated X-ray reflectivity also could be explained by micro-roughness of less than 3 nm and geometrical occulting effect due to large obstacle structures on the reflection surface.

Research and development of MEMS x-ray optics

Development of a new light-weight and low-cost micro pore optics is reported. Utilizing anisotropic chemical wet etching of MEMS (Micro Electro Mechanical System) technology, a number of smooth sidewalls are obtained at once. These sidewalls are potential X-ray mirrors. As a first step of R&D, basic characters of sidewalls such as surface roughness and X-ray reflectivity are experimentally studied. Rms-roughness of 10 ~ 20Å is confirmed in a KOH-etched wafer. Furthermore, the X-ray reflection is for the first time detected at Mg Kα 1.25 keV. Based on the obtained results, numerical simulations of four-stage MEMS X-ray optics are performed for future satellite mission.

Evaluation of X-ray reflectivity of a MEMS X-ray optic

X-ray reflectivity of an ultra light-weight X-ray optic using MEMS technologies was measured in two different energies (0.28 keV and 1.49 keV). The obtained reflectivities can be understood by considering the mirror surface structures.

Recent development of micropore optics using MEMS technologies

Recent development of the extremely light-weight micro pore optics based on the semiconductor MEMS (Micro Electro Mechanical System) technologies is reported. Anisotropic chemical wet etching of silicon (110) wafers were utilized, in order to obtain a row of smooth (111) side walls vertical to the wafer face and to use them as X-ray mirrors. To obtain high performance mirrors with smooth surfaces and a high aspect ratio, several modifications were made to our previous manufacturing process shown in Ezoe et al. (2005). After these improvements, smooth surfaces with rms roughness of the order of angstroms and also a high aspect ratio of 20 were achieved. Furthermore, a single-stage optic was designed as a first step to multi-stage optics. A mounting device and a slit device for the sample optic were fabricated fully using the MEMS technologies and evaluated.

Simulation-based design of a MEMS X-ray optic for X-ray astronomy

An ultra light-weight X-ray optic using MEMS technologies was designed for X-ray astronomy. Numerical simulation was utilized to estimate allowable fabrication accuracies. Obtained X-ray images with a fabricated optic were consistent with the design.

An analog baseband feedback circuit for TES signals in frequency domain multiplexing

Multiplexed readout of TES (Transition Edge Sensor) signals is one of the key technologies needed to realize large format arrays of microcalorimeters in future X-ray missions. In the FDM (Frequency-Domain Multiplexing) approach using MHz biasing frequencies, a wide band-width FLL (Flux Locked Loop) circuit is essential to compensate the phase delay between the TES sensor and the room temperature circuits. An analog feedback circuit using a lock-in amplifier technique and phase shifters with a very low noise pre-amplifier is being developed. This circuit will be tested with an actual TES array and an 8-input SQUID in the EURECA project.