A Beam intensity monitor for the evaluation beamline for soft X-ray optical elements
軟X線光学素子評価ビームラインのビーム強度モニタ
今園 孝志; 森谷 直司*; 原田 善寿*; 佐野 一雄*; 小池 雅人
Imazono, Takashi; Moriya, Naoji*; Harada, Yoshihisa*; Sano, Kazuo*; Koike, Masato
Since 2000, the evaluation beamline for soft X-ray optical elements, BL-11, at SR Center of Ritsumeikan University, has been operated to measure the wavelength and angular characteristics of absolute reflectivity (or diffraction efficiency) of soft X-ray (SX) optical devices in a wavelength range of 0.65-25 nm. It is important to calibrate and assign wavelength, intensity, and polarization of the light introduced into a reflecto-diffractometer (RD) at BL-11 along with the evaluation of the characteristics of optical element samples. Not the beam intensity of the zero-th order light (BM0) but that of the monochromatized first order light (BM1) should be measured for the normalization of the incident beam intensity. It is because there should be an obvious linear relationship between the two values of BM1 and the signal intensity (ID) from a detector equipped in the RD. A new beam intensity monitor based on total electron yield (TEY) method has been installed just before the RD. It has been found out that the correlation coefficient between the signals obtained by the beam monitor and that by the detector (a photodiode) of RD has been estimated to be 0.989. It indicates that the new beam intensity monitor provides accurate real time measurement of the incident beam intensity.