RISING beamline (BL28XU) for rechargeable battery analysis.

The newly installed BL28XU beamline at SPring-8 is dedicated to in situ structural and electronic analysis of rechargeable batteries. It supports the time range (1 ms to 100 s) and spatial range (1 µm to 1 mm) needed for battery analysis. Electrochemical apparatus for battery charging and discharging are available in experimental hutches and in a preparation room. Battery analysis can be carried out efficiently and effectively using X-ray diffraction, X-ray absorption fine-structure analysis and hard X-ray photoelectron spectroscopy. Here, the design and performance of the beamline are described, and preliminary results are presented.

Tissue-equivalent TL sheet dosimetry system for X- and gamma-ray dose mapping.

To measure dose distribution for X- and gamma rays simply and accurately, a tissue-equivalent thermoluminescent (TL) sheet-type dosemeter and reader system were developed. The TL sheet is composed of LiF:Mg,Cu,P and ETFE polymer, and the thickness is 0.2 mm. For the TL reading, a square heating plate, 20 cm on each side, was developed, and the temperature distribution was measured with an infrared thermal imaging camera. As a result, linearity within 2% and the homogeneity within 3% were confirmed. The TL signal emitted is detected using a CCD camera and displayed as a spatial dose distribution. Irradiation using synchrotron radiation between 10 and 100 keV and (60)Co gamma rays showed that the TL sheet dosimetry system was promising for radiation dose mapping for various purposes.

Energy response of LiF and Mg2SiO4 TLDs to 10-150 keV monoenergetic photons.

Energy response of LiF:Mg,Ti, LiF:Mg,Cu,P and Mg2SiO4:Tb thermoluminescence dosemeters (TLDs) was measured in the range 10-150 keV for monoenergetic photons at SPring-8 of an 8-GeV synchrotron radiation facility. The photon beam was monitored by a parallel-plate free-air ionisation chamber calibrated with an uncertainty of 3%. Owing to the small dimension of the beam, a rotating holder was designed in order to irradiate TLDs uniformly. The measured responses of LiF to energy were approximately in agreement with the calculated dose absorption dependence in the soft tissue. However, two types of LiF TLDs presented the different luminescent responses to the photon energy. The response of LiF:Mg,Ti had a smooth curve, and that of LiF:Mg,Cu,P presented a local maximum at 30 keV and a local minimum at 100 keV. The Mg2SiO4:Tb response was nearly bone equivalent. Linearity of dose responses was also confirmed up to 2 Gy on each TL material.

Comparison of in-phantom dose distributions for coronary angiography using an x-ray machine and synchrotron radiation.

Coronary cineangiography using synchrotron radiation is anticipated, owing to the high intensity and availability of monoenergy. To investigate allowable dose levels in clinical application, absorbed dose distribution in a tissue substitute phantom for a conventional x-ray machine was measured with thermoluminescent dosimeters at the University of Tsukuba under the practical conditions used for digital angiography. The dose rate at a 0.5-cm depth was 0.145 Gy/s, and the dose per frame was 0.725 mGy for the irradiation period of 5 ms per frame. For synchrotron radiation, the dose distribution measurement was made at a 5-GeV AR (Accumulation Ring) of the High Energy Accelerator Research Organization, in which a polymethylmethacrylate (PMMA) phantom was irradiated with the strongest beam available at the facility, which was 33.32 keV, 5.2 x 6.2 cm2 beam. Using this beam, a 1-mm-diameter coronary artery has been visualized at 1% iodine concentration at the AR. Nonhomogeneous strength distribution in the beam was observed in the vertical direction. The maximum dose rate was 0.556 Gy/s, and it attenuated to 1/3000 at a 30-cm depth in the beam center. At the deep positions, the doses were influenced by the high harmonics, which was confirmed with an EGS4 Monte Carlo calculation. Outside the beam, beam contamination on both sides of the main beam affected the doses. For comparison to the x-ray machine, the measured dose was analytically converted to that needed for a 5.2 x 16 cm2 beam that is used for clinical application. The dose rate at 0.5-cm depth was found to be 0.215 Gy/s, which is 1.48 times larger than that for x-rays. Moreover, the attenuation rate in the phantom was significantly greater than that of the x-ray machine, because of the difference of the energy spectra between the x-rays and synchrotron radiation used.

Dose measurements in inhomogeneous bone/tissue and lung/tissue phantoms for angiography using synchrotron radiation.

For angiography using synchrotron radiation we measured the absorbed dose distribution in inhomogeneous phantoms with thin LiF:Mg, Cu, P, LiF:Mg, Ti thermoluminescent dosimeters (TLDs) in tissue and lung substitutes, and with Mg2SiO4:Tb TLDs in bone substitute for 33.32 keV monoenergetic photons from synchrotron radiation. The energy responses of the TLDs were measured in air for 10-40 keV monoenergetic photons. The values at 30 keV became smaller by 30% for LiF:Mg, Cu, P and larger by 22% for Mg2SiO4:Tb than the ratio of the mass energy absorption coefficients of the TLDs to that of air. These values were used to modify the calculated response of the TLDs in each phantom material. The absorbed dose distribution obtained was compared with that calculated using the Monte Carlo transport code EGS4 expanded to a low-energy region, and their agreement was confirmed taking linear polarization into account. In the bone substitute the dose increased by a factor of 3.9, while behind the bone the dose decreased drastically because of photon attenuation. In the lung substitute a slight dose difference from that in soft tissue was observed because of its different density. The LiF:Mg, Cu, P TLDs exhibited a better energy response, higher sensitivity and wider linear regions than did the other tissue-equivalent TLDs in the low-energy region.

Absorbed dose measurements and calculations in phantoms for 1.5 to 50 keV photons.

A Monte Carlo code EGS4 expanded for low energy photon transport was validated by measuring absorbed doses in a phantom for 30 and 10 keV monoenergetic photons from synchrotron radiation. Using the EGS4 code, depth doses at 0.07 mm, 0.02 to 0.1 mm, and 10 mm in the ICRU slab phantoms were calculated for 1.5 to 50 keV photons using the updated photon cross section data PHOTX. The results show that the doses at 0.02 to 0.1 mm below 10 keV are practical indices of effective dose as calculated by others, based on the 1990 ICRP recommendations (1991).

Analysis of localised dose distribution in human body by Monte Carlo code system for photon irradiation.

In usual personal dosimetry, whole body irradiation is assumed. However, the opportunity of partial irradiation is increasing and the tendencies of protection quantities caused under those irradiation conditions are different. The code system has been developed and effective dose and organ absorbed doses have been calculated in the case of horizontal narrow photon beam irradiated from various directions at three representative body sections, 40, 50 and 60 cm originating from the top of the head. This work covers 24 beam directions, each 15 degrees angle ranging from 0 degrees to 345 degrees, three energy levels, 45 keV, 90 keV and 1.25 MeV, and three beam diameters of 1, 2 and 4 cm. These results show that the beam injected from diagonally front or other specific direction causes peak dose in the case of partial irradiation.

Response of GafChromic MD-55 radiochromic film to synchrotron radiation.

Synchrotron radiation has been increasingly and extensively used for materials science, biology and medical research. For measurement of high dose from the low energy photons, tissue-equivalent dosemeters having linearity in the Gy region are required. In this study, energy and dose responses of double-layer Gafchromic film MD-55 were measured using 10-40 keV monoenergetic photons from synchrotron radiation. The result showed that the energy responses normalised at 60Co gamma rays were 0.58-0.59 at 10-20 keV, 0.66 at 30 keV and 0.72 at 40 keV in air. The linearity was confirmed to extend from 2 Gy to 100 Gy.

Luminescence of CsGd2F7 crystals.

Optical and dosimetric properties of nominally pure CsGd2F7 crystals and of CsGd2F7 crystals doped with various concentrations of Pr3+ ions were investigated. Effects of X, beta and UV irradiation on these crystals were studied. Methods of optical absorption, X and UV excited luminescence, thermoluminescence (TL), phototransferred thermoluminescence and optically stimulated luminescence were used in these investigations. The dependence of the TL efficiency on the radiation dose was found to be linear up to 6 kGy for the 3 at.% Pr3+ doped samples. The crystals containing from 0.3 at.% to 1.0 at.% of Pr3+ ions were found to have the best TL sensitivity and the intensity of the main TL peak in these samples was more than two orders of magnitude higher than that of the pure crystals. The TL sensitivity of the CsGd,F7:Pr3+ crystals was also compared with that of other commonly used TLD materials.