06/12/99 Update

PEP-II Update June 12, 1999

During the past week we concentrated on compensation of the solenoid and raising the luminosity.

A week ago the BaBar solenoid was at full strength but both rings had significant problems with the skew quadrupole compensation. Orbit oscillation data showed coupling errors near the detector and the global ring coupling was difficult to control.

During a two day repair period for both PEP-II and BaBar work we found several problems with the skew quadrupoles including polarity, coil, database and strength errors. Also, the on-line accelerator models including the solenoid were loaded for the first time in the control system. These models are difficult to make as fields from the solenoid, quadrupoles, and dipoles are superimposed at the interaction region.

After recovery both rings showed significant improvement. The HER orbit data through the interaction point are nearly ideal. The LER oscillation data are much improved but one skew quadrupole near the detector had to be adjusted.

Collision studies started about 1 am Friday June 11. A luminosity of 5x10**31/cm**2/s with 174 bunches was achieved by 8:00 AM. Energy Secretary Bill Richardson (DOE) and his staff helped us take some collision and event data around 3 PM Friday.

During the evening the luminosity was raised by increasing the currents and working on the tunes and overlap issues. By 8:00 am Saturday June 12, the luminosity had reached 1.8x10**32/cm**2/s with 300 mA in the LER and 90 mA in the HER in 174 bunches. The luminosity and LER lifetimes are equal at about 35 minutes at peak luminosity. Topping off the currents takes about 10 minutes. The spot sizes at the collision point are about 230 microns by 16 microns (cap-sigmas). In the past 24 hours PEP-II has delivered about 5000/nb and BaBar has logged about 1400/nb. The BaBar backgrounds are manageable. The recently installed collimators are helping reduce these backgrounds.

We are preparing for an energy scan starting early this week.

John Seeman  12-June-1999

Suggestions to: John Seeman

[PEP-II Commissioning Updates] [PEP-II Home Page] [BABAR Detector Home Page] [SLAC Home Page]

Page owner: achan