Summary of the Spring 2015 GlueX Run

Spring 2015 GlueX Run

Dear collaborators,

This morning at 7am, the beam was terminated, concluding the Spring 2015 commissioning run. During this last weekend, we had planned to look for physics asymmetries using the diamond radiator. Production runs on the amorphous radiator and with the solenoid magnet at 1300A was done until Saturday morning. Then, Hovanes successfully set-up the 50 um diamond and we started to take polarized photon data around noon. As you know from Eugene's mail, 3 hour and half later, the magnet quenched. The rest of the weekend was dedicated to trigger and DAQ studies, and to take more straight track data for drift chamber alignment.

Apart from the magnet quench, this second commissioning was again successful, given the small amount of time we ran (we had a little less than 5 days of solid beam available) and that the energy was only 5.5 GeV. After the power failure took out one of the CHL plants, we had revised our original nominal goals, now assuming 10 calendar days of beam time. All but one of the revised goals were achieved. The most important was to characterize the diamond radiators and produce a polarized photon beam. This was done. Other critical goals were to set-up efficient triggers and fast DAQ. This was also achieved. In addition, the hydrogen cryotarget was commissioned and behaved very reliably. Good data were taken for drift chamber alignment and for target alignment check. The fast feedback was mostly commissioned. The slow feedback is able to improve the beam stability to the level required. Nice pi0 peaks were seen, as well as the rho peak, although there is not enough of these data to calibrate the calorimeters. The RF timing data were gathered. The photon beam polarimeter started its commissioning. Another important fact is that most of the subsystems had been improved in many respects compared to the Fall run and demonstrated their reliability. The goal that was not achieved was to establish that we can run the solenoid at 1300A. Correlated to this, we have also not achieved taking enough polarized data to look at physics asymmetry (but this was not a formal goal of the Spring commissioning).

Some of the goals that were part of the initial 12 GeV Spring commissioning could not be reached given the amount of time and/or the low beam energy: those are the pi0 calibration of the calorimeters, the total absorption counter commissioning, and running on the collimator 3.4mm hole.

We are now taking cosmic data and have powered down the beam line equipment. The hall and tagger are in restricted access.

Thank you,

Alexandre Deur, Hall D Run Coordinator.