Y. Awaya

Correlative multielectron processes in K-shell photoionization of Ca, Ti and V in the energy range of 8-35 keV

The Kalpha satellite spectra arising from the correlative multielectron processes accompanying K-shell photoionization of Ca, Ti and V were measured using a broad range crystal spectrometer. Multiconfiguration Dirac-Fock calculations were performed to interpret the observed,x-ray energies and the spectral line shape., The calculations agree fairly well with the experimental results. The variation of the KalphaL(1) satellite and the Kalpha(1,2)(h) hypersatellite intensities was measured as a function, of excitation energy in the range of 8-35 keV. The KalphaL(1)/Kalpha(1,2) intensity ratio for each,element is already saturated in our energy range, and the asymptotic values of 1.58 +/- 0.08, 1.26 +/- 0.06 and 0.97 +/- 0.05% for Ca, Ti. and V were determined. By combining the present results and the previously measured values for various elements, we have found a Z(-3.5) scaling law for the KalphaL(1)/Kalpha(1,2) intensity ratio, The measured Kalpha(1,2)(h)/Kalpha(1,2) for each element, is found to increase smoothly from its onset and shows a long saturation range extending up to at least 25 keV above the threshold for Ti. The evolution of the Kalpha(1,2)(h)/Kalpha(1,2) intensity ratio is compared with the analytic Thomas model and with the theoretical calculation based on the screened hydrogenic model. (Less)

New readout technique for two-dimensional position-sensitive detectors

Abstract A new simple technique for two-dimensional position readout from one electrode plane is proposed, which is applicable to a wide range of detector types such as a gas-filled counter and a microchannel plate. Combining the “backgammon” method with the “weighted coupling capacitor” method, the present technique has a simpler electrode pattern than the “wedge and strip” method and is free from thermal noise from which the “resistive layer” method suffers. An application of this technique to a position-sensitive proportional counter is reported.

Application of the “MBWC” two-dimensional position readout technique to a multiwire proportional counter

Abstract A two-dimensional position readout technique named “modified backgammon method with weighted coupling capacitors (MBWC)” has been applied to a multiwire proportional counter, and its image linearity and position resolution have been investigated. One of two types of the technique, the three-output MBWC method, has shown several kinds of image deformations. The sources of the deformation and the way to avoid them are clarified. On the other hand, an essentially linear image has been readily obtained by adopting the other type (four-output MBWC method). The overall spatial resolution parallel to the wire direction and the spatial resolution of the position encoding cathode for the direction perpendicular to the wire have been investigated with Fe K X-rays. The best values obtained are 130 and 110 μm (FWHM), respectively, which correspond to ∼600 × 600 pixels.

Flux pinning and flux creep in La2−xSrxCuO4 with splayed columnar defects

The effects of columnar defects with splayed configurations on flux pinning and flux creep were investigated experimentally. Parallel columnar defects and splayed columnar defects were introduced into specimens of La2−xSrxCuO4 by high-energy heavy-ion irradiation. A large enhancement of the flux pinning and the critical current density Jc due to the splayed columnar defects was observed. At temperature T<15 K and a magnetic field H=0.1 T, the effective pinning potential U0 of a specimen with splayed columns was larger than that of a specimen with parallel columns. On the other hand, at 15 K≤T≤30 K and H=0.1 T, U0 of a specimen with splayed columns was smaller than that of a specimen with parallel columns.

Photoionization of 4d-electrons in singly charged Xe ions

Using a photon - ion merged-beam technique, we measured the relative yield spectra of and ions created by photoionization of ions as a function of the photon energy in the 4d ionization region. The ion production, i.e. the double-electron ionization process is found to be dominant throughout the energy range investigated. A broad structure of 4d excitation ionization around 100 eV photon energy was observed in the yield spectrum. A spectral shoulder was observed for at around 85 eV, which was absent in the photoionization of neutral Xe. Some discrete lines were observed for both the - and -yield spectra below 75 eV. The experimental spectra were analysed by a multiconfiguration Dirac - Fock calculation. The largest structure at around 100 eV is attributable to (n=6,7) two-electron transitions. The discrete lines were found to be due to , n f transitions. A serious 4f-orbital collapse is suspected in the 4 fn p two-electron excited states, whereas the collapse is moderate in the singly excited 4f-orbitals.

Storage and Lifetime Measurements of Multiply Charged Ions Produced by Synchrotron Radiation

Multiply charged ions of rare gases were produced through photoionization, using white synchrotron radiation from the accumulation ring of TRISTAN, and the ions were confined in an rf trap. Charge state distribution and lifetime of the stored ions were measured by time-of-flight detection. Confinement of Xe6+-Xe8+ was exhibited with the storage lifetime of several ms, which is limited by the high background pressure needed to accumulate sufficient ion intensity.

A two-dimensional position-sensitive anode for microchannel plates based on the “MBWC” technique

Abstract The modified backgammon method with weighted coupling capacitors (MBWC) has been applied to a tandemmicrochannel-plate charged-particle detector for two-dimensional position encoding. After some optimizing procedure a position resolution better than 40 μm (FWHM) is obtained for an avalanche size of ∼ 1 × 10 7 electrons. Individual microchannels with 15 μm spacing are clearly resolved at the avalanche size of ∼ 4 × 10 7 electrons. Acceptable image linearity over the whole MCP sensitive area of 20 mm ace gf is obtained.

High Rydberg and Auger electrons from fast projectile ions studied by zero-degree electron spectroscopy

Abstract Zero-degree electron spectra were measured with high resolution for 64 MeV S5+ ions on He and 64 MeV S12+ ions on He and C, and for 90 MeV Sc8+ ions on He. In 64 MeV S ion collisions, a series of intense lines have been observed, which are attributed to the Auger transitions from 1s22s22p53snl to 1s22s22p6 for S5+ ions on He, and to the Coster-Kronig transitions from 1 s 2 2 p nl to 1 s 2 2 s ϵ l l′ for S12+ ions on He or C foils. The angular-momentum (l) distribution of the S12+ ions in the Rydberg state with n = 9 has been obtained and it is found that the high-l components are significantly enhanced for the solid target. In 90 MeV Sc8+ +He collisions, three groups of intense lines have been observed, which are attributed to the transitions from 1s22s22p53s23p to 1s22s22p63s, 1s22s22p63p, and 1s22s22p63d. The last transition, in which three electrons are involved via electron correlation, is studied and compared with previous results for the isoelectronic ions Al+ and Ar6+.

Angular distribution measurement of various L3 X-ray transitions

The presence of the magnetic quadrupole term in addition to the electric dipole one in the multipole expansion of the radiation field is reflected in the angular distribution of the X-ray transition. To extend the previous works the authors studied the angular distribution of different L3 X-ray lines of Ba, Sm and Er experimentally for proton impact at 0.23, 0.28 and 0.35 MeV bombarding energies respectively, using a Si(Li) detector. The anisotropy parameter ratios of the Ll and L alpha transitions were found to be 5.2+or-2.8, 5.5+or-0.7 and 6.9+or-1.5. Angular distributions of Tb L-shell X-rays were also measured by a high resolution crystal spectrometer for 0.556 MeV amu-1 nitrogen ions, a value of 3.5+or-2.5 was obtained for the anisotropy parameter ratio. These ratios deviate significantly from the theoretical ones.

The Kα and Kβ X-ray spectra of Al, Ti, Cr, Fe and Ni induced by 84 MeV nitrogen ions

Abstract The K X-rays from the target elements due to N-ion bombardment are measured with a crystal spectrometer. Some aspects owing to high incident energy are discussed. The Kα satellite, Kα hypersatellite and Kβ satellite peak spacings are obtained.