A tandem‐double‐slit optical system was constructed to evaluate the practical beam emittance of undulator radiation. The optical system was a combination of an upstream slit (S1) and downstream slit (S2) aligned on the optical axis with an appropriate separation. The intensity distribution after the double slits, I(x1, x2), was measured by scanning S1 and S2 in the horizontal direction. Coordinates having intensity were extracted from I(x1, x2), whose contour provided the standard deviation ellipse in the x1–x2 space. I(x1, x2) was converted to the corresponding distribution in the phase space, I(x1, x1′). The horizontal beam emittance was evaluated to be 3.1 nm rad, which was larger than the value of 2.4 nm rad estimated by using ray‐tracing. It was found that the increase was mainly due to an increase in beam divergence rather than size.

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size upstream slit beam divergence intensity distribution phase space ix1 optical system slits ix1 x2 deviation ellipse raytracing x1x2 emittance of undulator

Takumi Ikeda, Motoki Kawashima,Yasushi Kagoshima, Yuki Aoi, Tatsuki Akada, Yuki Takayama,.Measurement of the horizontal beam emittance of undulator radiation by tandem‐double‐slit optical system. (),.

Takumi Ikeda, et al."Measurement of the horizontal beam emittance of undulator radiation by tandem‐double‐slit optical system"

Takumi Ikeda, Motoki Kawashima,Yasushi Kagoshima, Yuki Aoi, Tatsuki Akada, Yuki Takayama,"Measurement of the horizontal beam emittance of undulator radiation by tandem‐double‐slit optical system"