An X-ray beam profile monitoring system at a beamline front-end combining a single-crystal diamond film and energy discrimination using droplet analysis.

This work has successfully demonstrated a system for monitoring pink-beam X-rays exiting from a beamline front-end, which has a specific spatial distribution based on each energy component. In this study, the X-rays scattered from a single-crystal chemical-vapor-deposited diamond film were converted into a cross-sectional image using pinhole optics, followed by digitization with a direct detection complementary metal-oxide-semiconductor 2D detector. By using single crystals instead of poly-crystals, good quality images were obtained with no diffraction bright spots. As a result of applying photon energy discrimination using the droplet analysis to the image information, the spatial distribution of each energy component of the undulator radiation was successfully visualized. The result was found to be in good agreement with the theoretically calculated result obtained using the synchrotron radiation calculation code SPECTRA. The new synchrotron radiation beam monitor proposed in this paper can serve as a powerful beam diagnostic tool for diffraction-limited rings that require strict light source stability.

Development and application of a tender X-ray ptychographic coherent diffraction imaging system on BL27SU at SPring-8.

Ptychographic coherent diffraction imaging (CDI) allows the visualization of both the structure and chemical state of materials on the nanoscale, and has been developed for use in the soft and hard X-ray regions. In this study, a ptychographic CDI system with pinhole or Fresnel zone-plate optics for use in the tender X-ray region (2-5 keV) was developed on beamline BL27SU at SPring-8, in which high-precision pinholes optimized for the tender energy range were used to obtain diffraction intensity patterns with a low background, and a temperature stabilization system was developed to reduce the drift of the sample position. A ptychography measurement of a 200 nm thick tantalum test chart was performed at an incident X-ray energy of 2.500 keV, and the phase image of the test chart was successfully reconstructed with approximately 50 nm resolution. As an application to practical materials, a sulfur polymer material was measured in the range of 2.465 to 2.500 keV including the sulfur K absorption edge, and the phase and absorption images were successfully reconstructed and the nanoscale absorption/phase spectra were derived from images at multiple energies. In 3 GeV synchrotron radiation facilities with a low-emittance storage ring, the use of the present system will allow the visualization on the nanoscale of the chemical states of various light elements that play important roles in materials science, biology and environmental science.

Energy-resolved beam-monitoring system for undulator radiation using scattering from a chemical-vapor-deposition diamond film.

With low-emittance synchrotron radiation rings, introducing accurate x-ray beams to a sample is difficult, and ensuring that the direction of the undulator beam is stable is essential. However, measuring the centroid of the undulator photon beam at the beamline front-end (FE) is difficult because the soft x-ray radiation is contaminated by the bending magnets upstream and downstream of the undulator. The x-ray beam position monitors (XBPMs), based on the interaction with the halo of undulator radiation, cannot estimate the centroid of the beam, and they cannot eliminate the effects of the bending magnets. To solve this problem, we have developed an energy-resolved beam-monitoring system for undulator radiation with the scattering from a diamond thin film deposited by chemical vapor deposition (CVD) in this study. An undulator x-ray beam is irradiated onto this film, and its elastic and Compton scattering are observed through a 50 µm-diameter pinhole. A beam spot is detected through a pinhole camera system using a direct-detection-type charge-coupled device camera with energy resolution. The peak of the first-order harmonic of the undulator radiation is selectively visualized to measure the centroid of the undulator radiation, as well as the spectrum. The proposed system using a CVD diamond film can provide accurate position information for a photon beam exiting the FE.

Development of an X-ray imaging detector to resolve 200 nm line-and-space patterns by using transparent ceramics layers bonded by solid-state diffusion.

A high-resolution lens-coupled X-ray imaging detector equipped with a thin-layer transparent ceramics scintillator has been developed. The scintillator consists of a 5 µm thick Ce-doped Lu3Al5O12 layer (LuAG:Ce) bonded onto the support substrate of the non-doped LuAG ceramics by using a solid-state diffusion technique. Secondary electron microscopy of the bonded interface indicated that the crystal grains were densely packed without any pores in the optical wavelength scale, indicating a quasi-uniform refractive index across the interface. This guarantees high transparency and minimum reflection, which are essential properties for X-ray imaging detectors. The LuAG:Ce scintillator was incorporated into an X-ray imaging detector coupled with an objective lens with a numerical aperture of 0.85 and an optical magnification of 100. The scintillation light was imaged onto a complementary metal-oxide-semiconductor image sensor. The effective pixel size on the scintillator plane was 65 nm. X-ray transmission images of 200 nm line-and-space patterns were successfully resolved. The high spatial resolution was demonstrated by X-ray transmission images of large integrated circuits with the wiring patterns clearly visualized.

Advancement of X-ray radiography using microfocus X-ray source in conjunction with amplitude grating and SOI pixel detector, SOPHIAS.

We show how to improve microfocus X-ray radiography by using the SOPHIAS silicon-on-insulator pixel detector in conjunction with an amplitude grating. Single-exposure multi-energy absorption and differential phase contrast imaging was performed using the single amplitude grating method. The sensitivity in differential phase contrast imaging in a two-pixel-pitch setup was enhanced by 39% in comparison with the previously reported method [Rev. Sci. Instrum. 81, 113702 (2010).] by analyzing charge-sharing effects. Small-angle-scattering imaging was also possible in the two-pixel-pitch setup by counting the number of X-ray photons passing the pixel boundaries.

New x-ray pink-beam profile monitor system for the SPring-8 beamline front-end.

A new beam profile monitoring system for the small X-ray beam exiting from the SPring-8 front-end was developed and tested at BL13XU. This system is intended as a screen monitor and also as a position monitor even at beam currents of 100 mA by using photoluminescence of a chemical vapor deposition-grown diamond film. To cope with the challenge that the spatial distribution of the photoluminescence in the vertical direction is too flat to detect the beam centroid within a limited narrow aperture, a filter was installed that absorbs the fundamental harmonic concentrated in the beam center, which resulted in "de-flattening" of the vertical distribution. For the measurement, the filter crossed the photon beam vertically at high speed to withstand the intense heat flux of the undulator pink-beam. A transient thermal analysis, which can simulate the movement of the irradiation position with time, was conducted to determine the appropriate configuration and the required moving speed of the filter to avoid accidental melting. In a demonstration experiment, the vertically separated beam profile could be successfully observed for a 0.8 × 0.8 mm(2) beam shaped by an XY slit and with a fundamental energy of 18.48 keV. The vertical beam centroid could be detected with a resolution of less than 0.1 mm.

Development of an X-ray pixel detector with multi-port charge-coupled device for X-ray free-electron laser experiments.

This paper presents development of an X-ray pixel detector with a multi-port charge-coupled device (MPCCD) for X-ray Free-Electron laser experiments. The fabrication process of the CCD was selected based on the X-ray radiation hardness against the estimated annual dose of 1.6 × 10(14) photon/mm(2). The sensor device was optimized by maximizing the full well capacity as high as 5 Me- within 50 µm square pixels while keeping the single photon detection capability for X-ray photons higher than 6 keV and a readout speed of 60 frames/s. The system development also included a detector system for the MPCCD sensor. This paper summarizes the performance, calibration methods, and operation status.

A photodiode amplifier system for pulse-by-pulse intensity measurement of an x-ray free electron laser.

We have developed a single-shot intensity-measurement system using a silicon positive-intrinsic-negative (PIN) photodiode for x-ray pulses from an x-ray free electron laser. A wide dynamic range (10(3)-10(11) photons/pulse) and long distance signal transmission (>100 m) were required for this measurement system. For this purpose, we developed charge-sensitive and shaping amplifiers, which can process charge pulses with a wide dynamic range and variable durations (ns-µs) and charge levels (pC-µC). Output signals from the amplifiers were transmitted to a data acquisition system through a long cable in the form of a differential signal. The x-ray pulse intensities were calculated from the peak values of the signals by a waveform fitting procedure. This system can measure 10(3)-10(9) photons/pulse of ~10 keV x-rays by direct irradiation of a silicon PIN photodiode, and from 10(7)-10(11) photons/pulse by detecting the x-rays scattered by a diamond film using the silicon PIN photodiode. This system gives a relative accuracy of ~10(-3) with a proper gain setting of the amplifiers for each measurement. Using this system, we succeeded in detecting weak light at the developmental phase of the light source, as well as intense light during lasing of the x-ray free electron laser.

Single-shot beam-position monitor for x-ray free electron laser.

We have developed an x-ray beam-position monitor for detecting the radiation properties of an x-ray free electron laser (FEL). It is composed of four PIN photodiodes that detect backscattered x-rays from a semitransparent diamond film placed in the beam path. The signal intensities from the photodiodes are used to compute the beam intensity and position. A proof-of-principle experiment at a synchrotron light source revealed that the error in the beam position is reduced to below 7 µm by using a nanocrystal diamond film prepared by plasma-enhanced chemical vapor deposition. Owing to high dose tolerance and transparency of the diamond film, the monitor is suitable for routine diagnostics of extremely intense x-ray pulses from the FEL.

Vacuum-compatible pulse selector for free-electron laser.

We developed a vacuum-compatible pulse selector for a free-electron laser. A rotating cylinder with eight apertures in a vacuum is driven by a closed-loop stepping motor system through a magnetically coupled rotary feedthrough. A field programmable gate array is used to synchronize the cylinder rotation with a trigger signal of the accelerator at a maximum repetition rate of 60 Hz. We achieved to select specific pulses from a continuous pulse train of the SPring-8 Compact SASE Source.

Feedback system for improving the performance of extended x-ray absorption fine structure measurements.

A rapid fine energy tuning method for a double-crystal monochromator (DCM) is developed by combining a feedback control system with a phase sensitive detector. This method maintains both a parallel angle between the first and second crystals of the DCM and the peak of the rocking curve. The method is used to perform a continuous energy scan of the DCM without readjustment of the angle between the two crystals. The time taken by this method to measure the extended x-ray absorption fine structure is 60% of that taken by a conventional procedure.