[Halld_src] update on the beam transmission activity

[Lubomir Pentchev]

Hello all,

I just wanted to update you on the attempts to improve the beam convergence and transmission.

Hovanes did his best to scan the active collimator to find the best position. He used both diamond and amorphous radiator, found somewhat better spot (off by fractions of a mm), but this didn't improve the transmission noticeably.
The scan results also showed some asymmetries in the PS response when moving the collimator in x/y direction.
After ~3h hours of studies at 16:30 we decided to go back to the original settings of the 5C11 quadrupole (as of yesterday before 13:00).  After that Hovanes performed another collimator scan, the distributions looked much more symmetric, and most importantly the transmission was restored to the yesterday's values. Even more, based on the last scan, Hovanes found new values for the beam position on the active collimator (0.0,-0.1) that improved the transmission by about 5-10%. We have not performed the harp scans to check the convergence, as the Ops were busy with setting up Hall A. This can be done later if needed.

For more details look at https://logbooks.jlab.org/entry/3941683.

We started production running at 17:30.

Regards,
 Lubomir


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