Haruhiko Ohashi

New micro-beam beamline at SPring-8, targeting at protein micro-crystallography

A new protein micro‐crystallography beamline BL32XU at SPring‐8 is under construction and scheduled to start operation in 2010. The beamline is designed to provide the stabilized and brilliant micro‐beam to collect high‐quality data from micro‐crystals. The beamline consists of a hybrid in‐vacuum undulator, a liquid‐nitrogen cooled double crystal monochromator, and K‐B focusing mirrors with large magnification factor. Development of data acquisition system and end station consists of high‐precision diffractometer, high‐efficiency area detector, sample auto‐changer etc. are also in progress.

Global High‐Accuracy Intercomparison of Slope Measuring Instruments

The upcoming generation of high accuracy synchrotron radiation (SR) optics will be characterized by a slope deviation from ideal shape in the range of some 0.05μrad rms at a sampling interval of about 1mm. To certify and improve the measurement capabilities of metrology tools to inspect these stringent specifications, an essential step is a worldwide intercomparison of these measurements based on a set of transfer standards. It is the aim of these cross measurements to verify the “absolute” correctness and comparability of the measurement results obtained by the cooperating partners when measuring the topography of specific reference optics (ROs) using their latest metrology tools and methods. Organized by members of the SR‐optics community, new national and international cross measurement comparisons of typical synchrotron radiation mirrors have been realized during the last few years: A round robin test by the European COST‐program (BESSY, Elettra, ESRF, Soleil) during the years 2004–2005 and a similar ...

Improvement in stability of SPring-8 X-ray monochromators with cryogenic-cooled silicon crystals

SPring-8 standard double-crystal monochromators cooled with liquid nitrogen are being improved for providing a stable supply of intense nanometer-focused X-ray beams. The instability originates from the vibration and thermal deformations of the various stages of the monochromators: the former is caused by turbulent flow of the liquid nitrogen, and the latter is mainly due to unwanted cooling from the liquid nitrogen. A low-vibration flexible tube was devised to stabilize the coolant flow by covering the corrugations of the flexible tube with an alumina fiber textile. To achieve thermal insulation, we inserted a machinable ceramic block and a copper plate between the cooled crystal holder and the stages; the temperature of the copper plate was controlled to within ±0.01 °C using a sheet heater and a proportional-integral-derivative current controller. As a result, the vibration was reduced from 1 to 0.15 in terms of the misalignment angle between the two crystals, and a vertical focus size of 230 nm was achieved by demagnification projection of the real light source onto the focal plane. The angular instability due to the thermal deformation was suppressed to a rate of less than 0.2/h. Furthermore, we discuss ongoing improvements for further stabilization.

Wave-optical assessment of alignment tolerances in nano-focusing with ellipsoidal mirror

High-precision ellipsoidal mirrors, which can efficiently focus X-rays to the nanometer dimension with a mirror, have not been realized because of the difficulties in the fabrication process. The purpose of our study was to develop nano-focusing ellipsoidal mirrors in the hard X-ray region. We developed a wave-optical focusing simulator for investigating alignment tolerances in nano-focusing with a designed ellipsoidal mirror, which produce a diffraction-limited focus size of 30 × 35u2005nm2 in full width at half maximum at an X-ray energy of 7 keV. The simulator can calculate focusing intensity distributions around the focal point under conditions of misalignment. The wave-optical simulator enabled the calculation of interference intensity distributions, which cannot be predicted by the conventional ray-trace method. The alignment conditions with a focal length error of ≲ ±10u2005µm, incident angle error of ≲ ±0.5u2005µrad, and in-plane rotation angle error of ≲ ±0.25u2005µrad must be satisfied for nano-focusing.

Stable delivery of nano-beams for advanced nano-scale analyses

Advanced nano-scale analyses such as x-ray absorption fine structure (XAFS), x-ray magnetic circular dichroism (XMCD) spectroscopy and x-ray fluorescence (XRF) with a ~100 nm spatial resolution have been routinely conducted by upgrading two x-ray beamlines BL37XU and BL39XU at SPring-8. The focusing beam size can be varied from 50 nm to 2 μm and high flux achieved at 1012 photons/s/0.01% b.w. with the beam size of 300 × 300 nm2 (full width at half maximum) at 12 keV.

Improvement in Stability of SPring‐8 Standard X‐Ray Monochromators with Water‐Cooled Crystals

SPring‐8 standard double‐crystal monochromators containing water‐cooled crystals were stabilized to a sufficient level to function as a part of optics components to supply stable microfocused x‐ray beams, by determining causes of the instability and then removing them. The instability was caused by two factors—thermal deformation of fine stepper stages in the monochromator, which resulted in reduction in beam intensity with time, and vibrations of coolant supply units and vacuum pumps, which resulted in fluctuation in beam intensity. We remodeled the crystal holders to maintain the stage temperatures constant with water, attached x‐ray and electron shields to the stages in order to prevent their warming up, introduced accumulators in the water circuits to absorb pressure pulsation, used polyurethane tubes to stabilize water flow, and placed rubber cushions un der scroll vacuum pumps. As a result, the intensity reduction rate of the beam decreased from 26% to 1% per hour and the intensity fluctuation from 13% to 1%. The monochromators were also modified to prevent radiation damage to the crystals, materials used as a water seal, and motor cables.

Development of contamination-free x-ray optics for next-generation light sources

We studied typical forms of contamination on X-ray mirrors that cause degradation of beam quality, investigated techniques to remove the contaminants, and propose methods to eliminate the sources of the contamination. The total amount of carbon-containing substances on various materials in the vicinity of a mirror was measured by thermal desorption-gas chromatography/mass spectrometry and thermal desorption spectroscopy. It was found that cleanliness and ultra-high vacuum techniques are required to produce the contamination-free surfaces that are essential for the propagation of high-quality X-ray beams. The reduction of carbonaceous residue adsorbed on the surfaces, and absorbed into the bulk, of the materials in the vicinity of the mirrors is a key step toward achieving contamination-free X-ray optics.

Ptychography simulations for precisely measuring wavefront profiles in soft x-ray focusing system based on ellipsoidal mirror

In synchrotron radiation facilities, soft X-ray nanofocusing with mirrors remains a hurdle due to difficulties in mirror fabrication. We have been researching the use of ellipsoidal mirrors for soft X-ray nanofocusing. Information on the wavefront errors of focused beams is helpful for improving the focusing system. This study presents ptychographic wavefront measurements for a nanofocusing system with an ellipsoidal mirror. We developed a ptychography program and performed several simulations at 300 eV to investigate the theoretical accuracy of the wavefront measurements. The simulation results indicate that wavefront measurements with high accuracy are possible.

Optical design of a sub-1-μm focusing system for soft x-ray free electron lasers

We present an optical design of a new focusing system for soft x-ray free electron lasers. The system is based on a two-staged focusing configuration that combines a Kirkpatrick-Baez focusing system with an ellipsoidal mirror so as to produce a sub-1-μm focal spot. A wave-optical simulation indicates that the power density at the focus exceeds 1018 W/cm2, which enables us to access exotic interactions between soft x-rays and matters.

Current status and future plan of the soft x-ray beamline at SACLA (Conference Presentation)

SACLA was inaugurated in March 2012 with two beamlines: BL3 for hard X-ray FEL and BL1 for wide range spontaneous emission. To enhance the research opportunities in soft X-ray region, the SCSS test accelerator, which was a prototype linac of SACLA and decommissioned in 2013, was upgraded, relocated to the SACLA undulator hall, and connected to BL1. The commissioning of this upgraded BL1 had been started from September in 2015, and user operation was started from June 2016. Currently, SASE-FEL pulses in the photon energy range of 20 to 150 eV are available and average pulse energy is about 70 μJ at 100 eV. We are developing beam diagnostic systems such as an arrival timing diagnostics between the SXFEL and the synchronized optical laser. We have further upgrade plans of the accelerator and the beamline. In this presentation, I will report the latest status and future upgrade plans of this beamline.