07/23/98 Update

PEP-II Update July 23, 1998

PEP-II Commissioning Update July 23

The past week has been very busy. A five day California heat wave significantly slowed progress but much has been done.

The LER lattice has received most of the attention. R12 measurements were made both globally and locally. Most three corrector bumps were tried. Interaction region closed angle and position bumps were tested. Several position monitor problems were found and fixed. Tune measurements taken. The transverse tunes came out correctly to about 0.02 or so.

LER injection studies were done to improve efficiency. RF studies made beam capture better. As of this morning, 1.2 mA has been stored in a single bunch, which is the design value. 1.3 mA has been stored in 12 bunches. The beam lifetime is about 1 minute due partially to vacuum pressure (not all the pumps have been turned on).

Simultaneously, the HER crew has been doing beam studies working on chromaticity, interaction region steering, and beta measurements.

At 10 am July 23 a single bunch of electrons were timed longitudinally to a single bunch of positrons (to +/- 5 psec) at the interaction region using a nearby shared position monitor. Transversely, the two beams were steered near each other using these same monitors. At exactly 12 noon our first beam-beam signals were seen after careful transverse beam scans. The electron bunch destroyed the positron lifetime and prevented positron injection. By mid-afternoon we had seen beam-beam signals in transverse deflection scans and in tune coupling between the beams using spectrum analyzers. A small party followed celebrating first detected beam-beam interactions.

Our future plans are to work on each ring separately about 80% of the time and to collide about 20% until our run ends July 31.

Many, many people helped with making colliding beams happen. They all did a tremendous job. Congratulations.

Best regards, John Seeman

Suggestions to: John Seeman

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