Study on beam spot size requirement in PES, BSRF and the beamline upgrade

Different photoelectron analyzer has different detectable area and acceptance angle, the experimental count rate is up to the photon flux density in the detected area, so the size of the X-ray source used for the analyzer is very important to get the best experimental result. Due to the experimental resolution and count rate of the analyzers is not so ideal, their relation to the beam spot of the beamline is studied. Result shows the size of beam spot at the sample position is too large, which helped to decide the upgrade project for beamline 4B9B and make the beam size much more smaller. A new design for high photon energy branch of the beamline upgrade with new post-focusing mirror is finished, meanwhile the focusing of low photon energy branch is also better designed.