10 October 2003 S. DeBarger

PEP-II 2002-2003 Vacuum Failures

PEP-IIMachine Advisory Committee

S. DeBarger10 October 2003

Elliptical Vacuum Valve Failure On 23 Jan 03, LER elliptical vacuum valves,

PR02 VACV 1153 & PR02 VACV 3044 would not fully open following 2 Hour ROD.

Both valves had damage to their RF seals and actuating mechanisms.

The valves were removed and replaced with spool pieces.

Failure is attributed to deficiencies in the design of the RF shields, compounded by a workmanship defect in one valve.

Beam Time Lost 26.00 hours

Current Status Valves repaired by VAT using existing RF

seal design. Spare valve installed at VACV 3044 location.

Gap rings at this location have been replaced with gap rings of the correct size.

Existing elliptical and round valves show heating by the beam. This is not adequately measured.

S. DeBarger10 October 2003

LER Frangible Link On 19 Apr 03, pressure at the IP became elevated.

Beam was unrunnable due to high LER Backgrounds.

Leak discovered on upstream LER Frangible Link. Several attempts to VacSeal were short-lived; finally

the leaking bellows module was replaced. During replacement of the leaking bellows, a

second bellows module was found to have damaged RF fingers.

Both bellows were replaced with spares and reinstalled.

Failure is attributed to mishandling of the bellows during or after installation, causing the RF fingers to lose contact with the beampipe. It is possible that corrosion also played a part in the failure.

Beam Time Lost 47.50 hours

Current Status New spare modules being fabricated using existing

design New bellows restraints for transportation & for

normal operation to be designed and fabricated

S. DeBarger10 October 2003

Mystery Pressure Bump Near IP

On 26 Apr 03, pressure at the IP became elevated.

During leakchecking, pressure improved. No leak was located.

Lots of speculation … could this be the first appearance of a problem that would resurface?

Beam Time Lost

15.50 hours

S. DeBarger10 October 2003

LER Arc 1 Pumping Chamber

On 9 May 03, pressure near PR02 VP1151 rose.

Leakchecking revealed a leak in a weld prep on the pumping chamber aluminum extrusion.

Attempts to seal the leak with VacSeal or to establish a guard vacuum were unsuccessful.

Replaced the leaking chamber on 17 May 03.

Beam Time Lost 48.50 hours

Current Status Chamber to be repaired

S. DeBarger10 October 2003

Q2 Chamber On 27 Jun 03, pressure began to rise at the IP. Initial attempts to leakcheck did not locate a leak. By 4 Jul 03 , the pressure had risen to the 10-4

level. Additional leakchecking revealed a water-to-vacuum leak in the Forward Q2 chamber.

Radial Ion Pump PR02 VP3012 failed on the 29th, possibly related to leakchecking activities.

Failure traced to a crack in the water-cooled mask due to a material defect

Beam Time Lost 50.1 hoursCurrent Status Chamber replaced with older version of the same

chamber After removal, discovered that the NEG pump had

been overheated at some time, damaging the NEG material

Chamber repair appears not to be an option Evaluating the performance of the installed

chamber and comparing to future running scenarios