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PEP-II 2002-2003 Vacuum Failures

PEP-II 2002-2003 Vacuum Failures. PEP-II Machine Advisory Committee. 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.

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PEP-II 2002-2003 Vacuum Failures

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  1. PEP-II 2002-2003 Vacuum Failures PEP-IIMachine Advisory Committee S. DeBarger

  2. 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. DeBarger

  3. 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. DeBarger

  4. 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. DeBarger

  5. 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. DeBarger

  6. 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 hours Current 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 S. DeBarger

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