[Halla_running] [EXTERNAL] RC update

[Caryn Palatchi]

Last night Compton chicane tuning was attempted, rates were significantly
lowered, but the match into the hall was not right and spot sizes at Target
were untenable. We received 150uA this morning after OPS tuned all night
the match into the hall, as it was off design, and we could not place beam
on target due to spot size limitations and inability to adjust hall quads
to sufficiently correct spot size. This morning match into hall was
sufficiently good to deliver beam on target. We ran pseudo-production runs
for an hour or so, but the Aq width was 500-600ppm due to severe 10perecent
clipping on A2 in injector which eventually was high enough to make it
impossible to deliver 150uA without blm trips. Injector steering was done
to reduce clipping initially but other trips occured downstream. 150uA of
clipped beam was sent to the hall and a calibration run (pita scan) was
performed with the noisy beam. The beam Aq RMS is greater than 50ppm
increase due to clipping, its a 400ppm increase. This can lead to halo,
cross correlations between charge and position, and impare PBQ. So these
were not ABU's, but we still took data anyways. Injector folks came back
around 2 and did some aperture clipping reduction. 150uA was sent to the
Hall and Compton rates looked good until the beam tripped. There was an
extended down period of approximately an hour during which match at 5MeV
and injector chicane was assessed. PD informs that beam should be returning
to HallA imminently.

If Compton rates are decent through the chicane, we will perform Compton
commissioning followed by production. If Compton rates are not able to be
lowered in a reasonable amount of time, we will go straight through and
continue production until HallC takes away the 1pass beam at some point
this weekend, possibly Saturday Day-Swing.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://mailman.jlab.org/pipermail/halla_running/attachments/20200110/cba3d93a/attachment.html>