BPM Upgrade Presented by: Nadine Kurita Contributors: S. Smith, S. Ecklund, J. Sebek, D. Martin, R. Hettel, R. Johnson, N. Reeck, M. Kosovsky, D. Arnett

Vacuum System p.2 Outline m BPM Upgrade project overview m 2005 upgrade/testing m LER Arc BPM’s m IR2 BPM’s m Summary

Vacuum System p.3 BPM Upgrade Overview m There are 3 styles of BPM’s in the PEP-II machine.  LER Arc BPM’s  Helicoflex sealed, SS housing  HER Arc BPM’s  Welded, CuNi housing  LER/HER Straight BPM’s  Welded, SS housing m Thermal and experimental models show that the BPM buttons could be approaching temperatures around 800 to 1000 C from HOM heating.  HOM heating has numerous parameters (i.e. bunch current, total current, beam position, chamber geometry). m Two areas are of major concern due to the high current and BPM position relative to beam.  LER arc BPM’s  IR2 BPM’s

Vacuum System p.4 Current Upgrades Downtime (cont.) m Four sets of modified LER Arc BPM’s at ARC 1,  Goal – to reduce HOM power.   7 mm molybdenum button  Welded tabs on buttons and pressed them off. l lbs, l average was ~ 60 lbs (excluding outliers).  Pressed molybdenum buttons l lbs l Test push ~850 lbs  leak tight.  One set has a 5 mm gap between button and housing.  One set has a 1 mm gap between button and housing. l Laser welded SS insert

Vacuum System p.5 Current Upgrades Downtime (cont.)  7mm button reduces power dissipated and transmitted by the BPM’s. (S. Ecklund)  Factor of 2 – 4?  Data indicate that the 7mm button with the 1mm gap absorbs the least amount of power.  Shorted button to housing  3 mm wide x 6.3 mm long,.4 mm thick Inconel strip l resistance welded l 0.25 mm of copper for thermal conductivity.   T increase by ~ 23 X l For, Q = 10W,  T = 200  C  Issues l Overheated the attenuators that were added for the additional HOM power that would be coming out of the transmission line. l Resistance welds may fail and lead to arcing.  Does not appear to be a viable solution. short

Vacuum System p LER Arc BPM Upgrade m Option 1 – Retrofit existing Borosilicate Glass BPM’s.  Successfully completed this downtime.  7mm button reduces power dissipated and transmitted.  Signal meets precision/accuracy requirements for stored beam at high current.  Signal is sufficient for single turn high current beam.  Downtime experience  Welded tabs on buttons and pressed them off. l lbs, l average was ~ 60 lbs (excluding outliers).  Pressed molybdenum buttons l lbs l Test push ~850 lbs  leak tight.  Pin diameter tolerance +/-.002”  Press fit tolerance is +/-.0001”  Pins were measured and buttons were match machined – forces were still larger than anticipated.  Errors in QC data lead to failures. Button partially pressed on.  Fit tolerance on small diameters make this task difficult & costly.

Vacuum System p.7 Design – BPM Retrofit m Current Plan  Re-design press fit to reduce force and increase tolerance band.  Taper and reduce press fit region. m Pros  Does not require significant design effort. m Cons  Requires manufacturing downtime work.  Could encounter difficulties and failures  Buttons diffusion welded from high temperatures?  Glass seal failing from removing buttons or pressing buttons (low risk – from tests).  Partially pressed on buttons – difficult to recover BPM if this occurs.  Thermal conductivity – 8 to 20 X worse than alumina.  Contingency cost could run higher (SLAC labor versus fixed cost). m Cost Estimate (N. Reeck) – consistent with AIP budget  Retrofit of the BPM  Indirect Cost: $ each including 28% contingency  Installation  Indirect Cost: $168 each l Cost does not include helicoflex seal

Vacuum System p.8 Design – Alumina BPM  Option 2 Saint Gobain Feedthru  SSRL/SPEAR3 – working on purchasing these for a small gap undulator chamber.  Preliminary cost estimate $245 each for 20 pieces.  Bake out/leak check - +$60 each.  Specification and drawings near completion 90%.  Pros l design exists l Alumina – better thermal conductivity l Cost is competitive with retrofitting.  New - $305, does not include destructive & electrical testing cost.  Total cost within AIP budget – potential less risk of overrun due to fix cost.  Retrofit - $340  Cons l Needs testing l Dielectric constant 2 X higher than glass. l New vendor – not much reliability data. l Not electrically equivalent to remaining BPMs l Schedule

Vacuum System p.9 Alumina Feedthru Layout Drawing

Vacuum System p.10 Major Milestones – option 1 - Retrofit m Dec ’05-Complete scope of project – critical decision. m Jan ’05-Complete new design m Feb ‘05-Push pull tests m Mar ‘06-Order Parts m May ’06-Receive buttons m Aug ’06-Remove & modify 200 feedthrus, 2-3 people/month m Sep ’06-Remove & modify 200 feedthrus m Oct ’06-Remove & modify 200 feedthrus m Nov ’06-Remove & modify 200 feedthrus m Dec ’06-Complete re-installation

Vacuum System p.11 Major Milestones – option 2 m Dec ’05-Complete scope of project – critical decision. m Dec ’05-Complete design specification m Dec ‘05-Order Prototype m Feb ‘06-MAFIA/RF simulations m Mar ’06-Receive Prototypes m May ‘06-Destructively test m May ‘06-Order production units m Aug ‘06-Receive 1 st lot (100 units) m Nov ’06-Receive last lot (200 units/month?) m Sep ’06- Install 1 st lot m Dec ’06-Install last lot

Vacuum System p.12 Major Milestones m Dec ’05-Complete scope of project. m Dec ’05-Complete design specification m Dec ‘05-Order Prototype m Feb ‘06-MAFIA/RF simulations m Mar ’06-Receive Prototypes m May ‘06-Destructively test m May ‘06-Order production units m Aug ‘06-Receive 1 st lot (100 units) m Nov ’06-Receive last lot (200 units/month?) m Sep ’06- Install 1 st lot m Dec ’06-Install last lot

Vacuum System p.13 IR2 BPM Upgrade Plan m Remove 15 mm button and leave 2.4 mm center pin as button. m Attempt to remove buttons in situ without removing chambers if possible. m Buttons will be leak checked from the reverse side if space permits. m If failure occurs during attempt (leak or failure to remove button).  Replace with copper blank.  Replace with new helicoflex sealed BPM similar to the new LER arc BPM.

Vacuum System p.14 BPM Removal Tool

Vacuum System p.15 Summary m HER arcs and LER/HER straights BPM’s do not require an upgrade at this time. m There is an upgrade plan for LER arcs and IR2.  Need to determine if BPM’s can be pulled in-situ. If not a decision to remove the chambers or leave the BPMs “as is” will have to be made. m Will need full support from physicists for RF/HOM analysis because the design & procurement cycle is long for new BPMs.