Electron Cloud Issues

A.Kulikov

SLAC

MAC review October 2003

Electron multipacting in the LER straight sections.

Current, mA Current, mA

Current, mA Current, mA

Feb. 2000 25 nTorr @ 1.1AFeb. 2000 50 nTorr @ 1 A

Oct. 2003 5.5 nTorr @ 1.5 A Oct. 2003 1.2nTorr @ 1.5 A

Electrons in the HER.

All HER holding vac. pumps HER distributed ion pumps

Electrons in the LER arcs

VP4031 09_29_03

VP4031 (6-8)-Jul-01Solenoid OFF

VP4031 15-Aug-01Solenoid ON 14-Aug-01

Elec4031 09-29-03

3.1E12

Electron multipacting and luminosity

2-May-2000Before 17:00: 10 sections of solenoids ON (Str. 12)After 18:15: 23 sections ON (Str. 12, Str. 4, Str. 8)

July 200029 sections ON

The last section in the straights was energized 16-Mar-01 (54 total)

Solenoids in the LER arcs: the first - 23-Apr-01, the last - 9-Feb-02

Positron beam sizes driven by the electron cloud effect

31-Jul-2000

Str.12 solenoids effect on the beam sizes.All other solenoids in the ring are ON, single ring.

28-Aug-01

Lifetime Horizontal beam size Vertical beam size

1.46 A

450 mA

ON

OFF

Solenoids Arc-3 effect on the beam sizes.All other solenoids are ON, single beam.

Lifetime Horizontal beam size Vertical beam size

ON

OFF

1.5 A

0.5 A

28-Aug-01

Solenoid field scan (Bmax = 30Gauss)4” round SS chamber, colliding beams

Bunch pattern - by 3 LER current - (1.45 - 1.25) A Number of bunches - 1078

Summer 2003 improvements:

Additional 50 Gauss solenoids for all straight sections drift chambers.

Double the field at pumping T-s, transitions and small drift chambers for all LER straight sections.

Additional solenoids for “no sexstupole” girders in all LER arcs.

50 Gauss solenoid section

Pumping T

Double the field at the pumping T-s

“No sextupole” chamber