Manabu Inagaki

Wavelength Dispersive X-ray Absorption Fine Structure Imaging by Parametric X-ray Radiation

The parametric X-ray radiation (PXR) generator system at Laboratory for Electron Beam Research and Application (LEBRA) in Nihon University is a monochromatic and coherent X-ray source with horizontal wavelength dispersion. The energy definition of the X-rays, which depends on the horizontal size of the incident electron beam on the generator target crystal, has been investigated experimentally by measuring the X-ray absorption near edge structure (XANES) spectra on Cu and CuO associated with conventional X-ray absorption imaging technique. The result demonstrated the controllability of the spectrum resolution of XANES by adjusting of the horizontal electron beam size on the target crystal. The XANES spectra were obtained with energy resolution of several eV at the narrowest case, which is in qualitative agreement with the energy definition of the PXR X-rays evaluated from geometrical consideration. The result also suggested that the wavelength dispersive X-ray absorption fine structure measurement associated with imaging technique is one of the promising applications of PXR.

Observation of intense terahertz-wave coherent synchrotron radiation at LEBRA

We observed intense coherent synchrotron radiation (CSR) in the terahertz region using an S-band linac at the Laboratory for Electron Beam Research and Application at Nihon University. The evolution of the CSR power was measured, and the CSR reflected in the vacuum chamber of the bending magnet could be extracted through the quartz window for a few tens of picoseconds. The long wave packet of the delayed CSR in the autocorrelation suggests that the delayed CSR was the non-resonant ring-down of the vacuum chamber of the bending magnet. To design a high-energy accelerator, it is necessary to decrease high-energy photons resulting from Compton backscattering with intense CSR.

Tunable Monochromatic X‐ray Source Based on Parametric X‐ray Radiation at LEBRA, Nihon University

The monochromatic X‐ray source based on parametric X‐ray radiation (PXR) was developed by using the electron beam from the 125‐MeV linac at Nihon University. The X‐ray generating system consists of two silicon perfect‐crystal plates to offer a wide tunability. The system has actually been providing the energy dispersive monochromatic X‐ray beam in the region of 6 to 20 keV, using Si(111)‐plane for the target and the second crystals. Since the X‐ray beam from the PXR generator has rather high energy resolution and coherency, X‐ray absorption fine structure (XAFS) measurement and phase‐contrast imaging are possible applications of PXR. Actually, preliminary experiments on energy dispersive XAFS measurement and refraction‐contrast imaging have been successfully carried out using the PXR beam.

GEOMETRICAL EFFECT OF TARGET CRYSTAL ON PXR GENERATION AS A COHERENT X-RAY SOURCE

The experiments of the PXR performance carried out for the target crystals with different cutting planes have shown significant difference in the PXR property, which suggests another way to increase the PXR intensity than by increasing the electron beam current. In order to investigate the effect of the geometrical condition of the crystal surface on the PXR property, the experiments have been carried out for the target crystal with a knife-edge-shaped cut surface. For the case with symmetric Bragg geometry on the front surface and asymmetric condition on the rear surface, the rather low intensity X-ray beam has shown considerably good spatial coherence. The X-ray beam with narrow line width has made it possible to obtain X-ray absorption spectra with a high resolution. In contrast, relatively high intensity, which enabled taking an absorption image with the exposure for several tens of seconds, has been obtained for the geometry with asymmetric front surface and symmetric rear surface. This configuration, however, has raised a problem of degradation in the spatial coherence of the X-rays due to the superposition of two different X-ray beams.

Performance and Application of FEL and PXR Sources at Nihon University

The infrared free electron laser (FEL) and the parametric X‐ray radiation (PXR) developed on the basis of the 125 MeV electron linac at Nihon University have been applied to studies in a variety of scientific fields. Primary users so far are the faculty members in the university, approximately 2000 hr/year of the machine time having been dedicated to the experiments since 2004. Currently the wavelength range of the FEL served for users’ experiments covers 1500 to 6000 nm at the optical power level of 10 to 30 mJ/macropulse. Combination of the fundamental infrared FEL with BBO non‐linear optical crystals yielded higher harmonics with good conversion efficiencies, which has extended the available wavelength range as short as approximately 400 nm. The PXR generator has employed a double‐crystal system so that the monochromatic X‐ray beam is available at a fixed output port independently of the X‐ray center energy. By using a Si(111) crystal as the PXR target the energy variable monochromatic X‐ray beam from ...

Development of ionization chamber for in-line intensity monitoring of large profile parametric X-ray beam

An in-line ionization chamber has been developed for the real-time measurement of the absolute intensity of the pulsed parametric X-ray (PXR) beam during irradiation experiments. The quasi-monochromatic PXR generating system was developed at the Laboratory for Electron Beam Research and Application (LEBRA) in Nihon University. In contrast to typical narrow X-ray beams in synchrotron radiation facilities, the PXR beam profile is as large as approximately 100 mm in diameter with rather uniform flux distribution at the X-ray output port in the experimental hall. The energy of the PXR beam ranges from 5 to 34 keV, which is specified by the PXR target crystal plane and its geometrical condition. The ionization chamber is of a plane parallel type employing 6-μm thick double-sided aluminum vapor-deposited polyester films for the plane electrodes through which the X-ray beam passes. The plane bias electrode has been placed at an equal distance of 25 mm from the two plane earth electrodes that act as the beam windows with an aperture diameter of 120 mm. Due to the pulsed property of the PXR beam and the geometrical configuration of the ionization chamber, the charge-sensitive preamplifier output pulse height represents an integral of the fast electron current, corresponding to a half of the total ionization charge produced by the beam. The intensity of the PXR beam has been measured for various X-ray energies by using nitrogen and argon, respectively, as the filling gas.