01/22/98 Update

PEP-II Commissioning Update January 22, 1998

PEP-II Commissioning Update January 22, 1998.

We have been commissioning the PEP-II HER with stored beam and the LER with injected beam for the past week. Each ring gets a 1 Hz injection rate with the rest of the linac pulses going to the SLC/SLD.

The feedback loops have received most of the effort recently:
The transverse feedback system under Walter Barry's direction has worked very reliably and almost continuously over the past week. It has damped all the transverse oscillations allowing us to get to high currents.

The longitudinal feedback system is under John Fox, Dmitry Teytelman, and others. They have been tuning their system and measuring longitudinal coupled bunch modes. We will put this system to the test when all the repaired power amplifiers arrive later this month.

The RF feedback loops have received much effort from Paul Corredoura, Rich Tighe, and Stephanie Allison. The new clock modules are now working and the local master oscillator is installed and commissioned. The main and ripple loops are working on all of the five HER RF stations and the comb loops on three stations. The remaining comb loops will be made to work in a few days.

With these feedback loops on in three RF stations and the other stations in park, Uli Wienands, Tom Himel, and the HER crew stored 410 mA of electrons in 1658 bunches at 9.0 GeV. The bunches were completely stable to over 300 mA but with some oscillations at 400 mA. The beam lifetime at 300 mA is 3 hours. A 300 mA beam was allowed to coast for 45 minutes. At an injection rate of1 Hz the 410 mA beam was injected in about 25 minutes.

The 1024 turn BPM measurement program which allows precise betatron phase measurements between BPMs has been made to work by Michael Saleski, Tom Himel, Linda Hendrickson and Tony Gromme. These measurements can be taken and analyzed in a few seconds online. The results of these measurements have been used to fix the betatron functions around the ring to a few percent in real time (James Safranek and Martin Donald). Additional adjustment of the betatron functions in the interaction region (at the 30% level) is needed.

We have also successfully tested the bunch-by-bunch injection controller which fills each bunch to the correct level. The bunch-by-bunch measurement hardware under Jim Hinkson and Mike Chen and the software under Ron Chestnut now work in concert to fill all the desired bunches uniformly. This system by itself refills missing holes in the fill from low linac pulses and, then, automatically stops when finished. The results is a very satisfying uniform fill.

The interaction region background group with Tom Mattison, Witold Kozanecki, and many people from the BaBar collaboration have been making measurements under varied beam conditions. We are actively studying the results and planning additional measurements.

Congratulations to all for the new beam current record of 410 mA.

For the PEP-II team-----John Seeman

Suggestions to: John Seeman

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