electron cloud issues

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