Run Coordinator report: Fall 2021 w13

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RC report November 10-17

This was the first full week of running the SRC/CT experiment, which started November 8. The harp scans done at the beginning of the week showed a factor of two wider (than the spec) photon beam in the horizontal direction, while in vertical it was narrower. The optics people advice to reduce the focusing of the last quad at 5C11. After that was done, the beam extrapolation tool showed improvement of the focusing, however the transmission went down by ~15%. Hovanes did collimator scan that showed x/y asymmetry and was not able to improve the transmission. We restored the old parameters of the quad, the results of the collimator scan were much more symmetric and the transmission was restored. Even more, a little repositioning of the beam on the AC increased the transmission by 10%. A discussion within the GlueX collaboration was initiated by Richard J. on how to improve the photon beam characterization and what tools are needed for that. We suspect that the extrapolation was not accurate in predicting the vertical width of the beam. It turned out the emittance has not been measured this year and we recommended to the accelerator people to do this for every running period.

Apart from the beam focusing exercise, the week was very productive in data taking on diamond radiator with some small fraction on amorphous one. Due to the high ABU (68%) the experiment collected ~40% of the data while using ~30% of their time. Over the weekend the writing on tape stopped, however, this was not critical due to the high disk capacity. On Monday the copying to tapes was resumed.