W. T. Lin

Focusing mirror for x-ray free-electron lasers

We present the design, fabrication, and evaluation of a large total-reflection mirror for focusing x-ray free-electron laser beams to nanometer dimensions. We used an elliptical focusing mirror made of silicon that was 400 mm long and had a focal length of 550 mm. Electrolytic in-process dressing grinding was used for initial-step figuring and elastic emission machining was employed for final figuring and surface smoothing. A figure accuracy with a peak-to-valley height of 2 nm was achieved across the entire area. Characterization of the focused beam was performed at BL29XUL of SPring-8. The focused beam size was 75 nm at 15 keV, which is almost equal to the theoretical size.

Development and Evaluation of a Non-Contact On-Machine Profile Measurement System Using a Compact Laser Probe

A non-contact on-machine measurement system has been developed since various precise machines are getting lighter and smaller; therefore, processing with nano-precision is demanded recently. This system makes possible to measure with high precision without any damages and it is unnecessary for workpieces to attach or detach from a machine tool. Moreover, this system achieves on-machine form error compensation with high precision. On the other hand, the details of the system performances are still unknown. This study focuses on evaluating the performances by the comparison of the results that measured by this system and an existing measurement instrument under various conditions. As a result, this system shows an equivalent capability of measurement with high precision as the existing measurement instrument.

Fabrication of a 400-mm-long mirror for focusing x-ray free-electron lasers to sub-100 nm

We describe the fabrication of a long mirror for focusing X-ray free electron lasers to nanometer dimension, for the production of high photon density beams. The focusing mirror has an elliptical curved shape with a length of 400 mm and focal length of 550 mm. Electrolytic in-process dressing grinding is used for first-step figuring and elastic emission machining is employed for final figuring and surface smoothing. Figure accuracy with a peak-to-valley height of 2 nm is achieved. A focusing test was performed at BL29XUL of SPring-8 and found the focused beam size to be approximately 75 nm at 15 keV, very similar to the theoretical value.

R&D of Ray Tracing Simulation Software and Fabrication Technologies Based on VCAD (Volume-CAD) Concept for GRIN Lens

We have been developing an intellectual manufacturing process applying IT (V-Cam system fabrication processes) based on Volume-CAD (VCAD) system which can express internal information of materials. This paper introduces the ultra-precision grinding, ray tracing (optical path) simulation software ‘V-Opt’ and the measurement of actual optical functions in the development of optical element taking gradient refractive index (GRIN) lens with functionally graded material properties as a model. In finish ground GRIN lens using SD#8000 wheel, the P-V (Peek to Value) of 27.07 nm, surface roughness (Ra) of 1.83 nm is obtained. ‘V-Opt’ developed for GRIN lens have two main functions; one is the visualizations of ray tracing and the other is the evaluation of spot diagram and focal length.

Development of X-ray mirrors manufacturing process with ELID-grinding and polishing methods

A large ultraprecision aspheric grinding system with Electrolytic In-process Dressing (ELID) has been developed for the fabrication of large optical elements and components, which can be used in Synchrotron radiation facilities. An ELID-grinding unit is equipped on the machine, and long-term stabilised grinding performance was successfully achieved for SiC, Si, fused silica mirrors and many other hard material mirrors. This paper introduces the major specifications of the developed machine, and discusses certain representative applications in the R&D of special optical elements and components such as X-ray reflective optics, and use of a new feed method to improve the surface roughness of X-ray mirrors with ELID-grinding to obtain nanosurface. The polishing was implemented in two processes: preparing polishing and final polishing. In the final polishing process, the polyethyleneterephthalate fibres felt sheet was used and a very good surface roughness was obtained.