Performance with various diffraction gratings:

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Select Publications

A photoion–photoelectron coincidence study of (N2)2 and (N2)3

Abstract: The photoion–photoelectron coincidence (PIPECO) spectra for (N2)+ 2 in the wavelength range 650–866 Å have been measured at different nozzle stagnation pressures. The formation of stable (N2)+ 2 from fragmentation of excited (N2)+ n cluster ions initially produced by photoionization of (N2) n , n≥3, is efficient. For nozzle expansion conditions which minimize the production of (N2) n , n≥3, the intensities for the N+ 2(Ã,B̃)⋅N2 PIPECO bands are found to be negligibly small compared to that of the N+ 2(X̃)⋅N2 PIPECO band, indicating that the electronically excited N+ 2(Ã,B̃)⋅N2 dimer ions are dissociative in temporal ranges < 42 μs. Assuming that the radiative lifetimes for N+ 2(Ã,B̃) and N+ 2(Ã,B̃)⋅N2 are identical, we estimate that the dissociative lifetimes for N+ 2(Ã)⋅N2 and N+ 2(B̃)⋅N2 are ≲10 μs and ≲60 ns, respectively. The ionization energy for (N2)2 is determined to be 14.50±0.08 eV (855±5 Å), suggesting that N+ 2(X̃)⋅N2 is bound by 1.09±0.08 eV. The PIPECO data for (N2)+ 2 presented here and those for (CO)+ 2 reported previously support the perturbed monomer ion model for the photoionization of a van der Waals cluster. Namely, the formation of N+ 2⋅(N2) n−1 by photoionization of (N2) n , n≥2, can be viewed as a photoionization process of N2 perturbed by the presence of other N2 molecules in the clusters. We suggest that the rapid dissociation of electronically and vibrationally excited dimer ions is a general mechanism for the suppression of autoionization features in the photoionization efficiency spectrum for an ionized van der Waals dimer.

K. Norwood, G. Luo and C. Y. Ng

Ion temperature and radial profile of CII-CV located in the edge and divertor plasmas of large helical device

Abstract: Space-resolved vacuum ultraviolet (VUV) spectroscopy using a 3-m normal incidence spectrometer is utilized to measure the impurity emission profile in the edge and divertor plasmas of the Large Helical Device (LHD). It measures the vertical profile of VUV lines emitted in the wavelength range of 300–3200 °A. CII, CIII, CIV, and CV lines emitted from carbon ions are successfully measured, and their ion temperatures are derived from the Doppler broadening. Vertical profiles of the emission intensity and the ion temperature are measured simultaneously for the CIV line. The emission intensity profile, which has several peak structures, is reasonably explained by considering the relation between the C3+ ion distribution and the geometry used for the observations.

Tetsutarou Oishi, Shigeru Morita, Chunfeng Dong, Motoshi Goto, Erhui Wang, Xianli Huang

Line spectrum and ion temperature measurements from tungsten ions at low ionization stages in large helical device based on vacuum ultraviolet spectroscopy in wavelength range of 500–2200 Angstroms

Abstract: Vacuum ultraviolet spectra of emissions released from tungsten ions at lower ionization stages were measured in the Large Helical Device (LHD) in the wavelength range of 500–2200 Å using a 3 m normal incidence spectrometer. Tungsten ions were distributed in the LHD plasma by injecting a pellet consisting of a small piece of tungsten metal and polyethylene tube. Many lines having different wavelengths from intrinsic impurity ions were observed just after the tungsten pellet injection. Doppler broadening of a tungsten candidate line was successfully measured and the ion temperature was obtained.

T. Oishi, S. Morita, X. L. Huang, H. M. Zhang and M. Goto

VUV wall stabilized argon arc discharge source

Abstract: 10 kW and 2kw wall stabilized argon arc sources have been developed in this institute as VUV spectroradiometric standard sources. The stability and reproducibility are better than 0. 2. Plasma spectroscopic diagnostics shows that the plasma temperature is 12759 K and the electron density is 1. 36x1023 m3 when the arc current is 40 A and argon pressure is 1. 75x10S'' Pa. Richter method absolute method relative method and computer spectral line reconstruction technique were used for plasma diagnostics. Based on McPherson 2253 M5 normal incidence VUV monochromator a computer controlled VUV spectroradiometer was set up. Impurity gases such as N1COKr Owere put into 10 kW arc and several black body limited lines (BBLL) were produced from 100 to 250 nm. These lines were used to calibrate deuterium lamp as transfer standard

Futian Li, Jianlin Cao, Bo Chen, Limin Qian, Lei Jin, Xingdan Chen

Performance of IR-VUV normal incidence monochromator beamline at UVSOR

Abstract: The beamline BL7B at the UVSOR facility for solid-state spectroscopy has been opening for users after reconstruction. This beamline consists of a 3 m normal incidence monochromator and covers the spectral range from the vacuum ultraviolet to the infrared region. The optical configuration and the performance, such as photon number, purity and resolving power, are reported.

K Fukuia, H Miurab, H Nakagawab, I Shimoyamac, K Nakagawad, H Okamurae, T Nanbae, M Hasumotoa, T Kinoshitaf

Space-resolved VUV spectroscopy using the 3 m normal incidence spectrometer with back-illuminated CCD detector in the LHD

Abstract: Space-resolved VUV (300–3100 Å) spectroscopy using the 3 m normal incidence spectrometer has been developed for the study of edge plasmas in the Large Helical Device(LHD). The radial (vertical) profile is obtained with a space-resolved slit placed horizontally between the entrance slit and the grating of the spectrometer. Using a cylindrical mirror placed in the front of the entrance slit, which magnifies the vertical image five times, a full vertical distribution of the LHD plasma is projected on the back-illuminated CCDdetector. The two-dimensional distribution can be measured by scanning a toroidal slit placed vertically between the spectrometer and LHD during a single discharge. Recently, first results were successfully obtained. Some examples of the vertical profile and temporal behaviors of the ion temperature are presented with a description of the instrumentation. Unfortunately, the poloidal rotation could not be measured, because the data from the CCD operated in room temperature included a lot of thermal noise. After repairing the cooling system, the S/N ratio can be much improved. The simultaneous measurement of the vertical profiles of VUV line emissions, ion temperature, and poloidal rotation will become possible.

Shigeru Morita and Motoshi Goto