Photon Factory Activity Report 2004 #22 Part B (2005)
Instrumentation and Technique

12A/2004G023

ABSOLUTE CALIBRATION OF SPACE-RESOLVINGSOFT X-RAY SPECTROGRAPH FOR PLASMA DIAGNOSTICS
Masayuki YOSHIKAWA*, Yuusuke KUBOTA, Takayuki KOBAYASHI, and Ken MATAMA
Plasma Research Center, University of Tsukuba, Tsukuba, Ibaraki 305-8755, Japan
Introduction
Measurements of spatial and temporal variationof spectra in the wavelength range from vacuum
ultraviolet (VUV) to soft x-ray (SX) are necessary todetermine radiation power losses and ion density profiles
which directly relate to the impurity transport,
confinement and sources in magnetically confinedplasmas. We developed space- and time-resolving VUV(150-1050 Å) [1, 2] and SX (20-350 Å) [3, 4]
spectrographs and applied for impurity diagnostics in thetandem mirror GAMMA 10.
For quantitative analyses of emission lines, it isimportant to characterize the absolute sensitivity of these
spectrograph systems throughout their wavelength ranges.
Previously we measured the absolute sensitivities of VUVspectrograph with changing the incident light angle into
the VUV spectrograph. By changing the incident angleof the VUV spectrograph, we can change the observing
spectral range of the VUV spectrograph. [1, 2] In thisreport, we show the spectra of the spectrograph when wechanged the incident light angle into the SX spectrographin a beam line 12A (BL-12A).
Experiments
In the space- and time-resolving SX
spectrograph, a concave grating ruled with varied spacing(Hitachi P/N001-0266) is used, which has a nominal
groove density of 1200 g/mm and a ruled area of 50 × 302mm . The incident angle is 87 ° and the effective braze
wavelength is 100 Å. The entrance slit is a 6-mm inheight and 100 µm in width. A MCP intensified detector2(Hamamatsu F2814-23P) having 50 × 50 mm active area
is set on the flat field output plane. The recording
system of spectral image is a high-speed solid state
camera (Reticon MC9256) with a fast scanning controller.
The resolution of video image is eight bit. The frame
rate with full image size, 256 × 256 pixels, can bechanged from 4 to 106 frame/s.
The experiments have been carried out at
BL-12A. The incident photon intensity was monitored
just behind the entrance slit by using an absolutely
calibrated XUV silicon photodiode (IRD AXUV-100G).
The output spectral image was recorded using ahigh-speed camera. Measurements are repeated forwavelength range from 2 nm to 39 nm at the BL-12A
with 1 nm intervals. We changed the incident lightangle into the spectrograph by changing the entrance slit
position of the spectrograph. Nominal entrance slit
position is 32.0 mm (87.0 ˚). We changed the incident

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Users' Reportslit position as 31.0 (87.3 ˚) and 33.0 mm (86.7 ˚) in orderto study characteristics of the SX spectrograph.
Results
Fig. 1 shows the spectra observed in the SX
spectrograph with the incident angles of 87.0 ˚ (red solidline), 87.3 ˚(blue dotted line), and 86.7 ˚ (green dottedline) for the incident beam wavelength of 15 nm. The
sensitivity of the SX spectrograph depends on the incident
beam angle. The observable spectral position in thedetection system is changed about 0.3 nm with theincident angle. We plan to carry out the more precise
experiments for diffraction efficiency against the incident
angle of the SX spectrograph.

Fig. 1 Spectra observed in SX spectrograph with
the incident angles of 87.0 ° (red solid line), 87.3 ° (bluedotted line), and 86.7 ° (green dotted line) for the incident
beam wavelength of 15 nm.

References[1] M. Yoshikawa et al., Photon Factory Activity Report#21, 2004, Proposal No.2002G033.
[2] M. Yoshikawa et al., Rev. Sci. Instrum. 75,4088 (2004).
[3] N. Yamaguchi et al., J. Plasma and Fusion Res. 71,867(1995).
[4] M. Yoshikawa et al., Nucl. Instrum. Methods Phys.
Res. A 467-468, 1533 (2001).
* yosikawa@prc.tsukuba.ac.jp