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BPM Upgrade

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. Outline. BPM Upgrade project overview 2005 upgrade/testing LER Arc BPM’s IR2 BPM’s Summary. BPM Upgrade Overview.

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BPM Upgrade

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  1. 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

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

  3. BPM Upgrade Overview • 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 • 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). • 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.3

  4. Current Upgrades - 2005 Downtime (cont.) • 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. • 50-150 lbs, • average was ~ 60 lbs (excluding outliers). • Pressed molybdenum buttons • 100-600 lbs • 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. • Laser welded SS insert Vacuum System p.4

  5. short Current Upgrades - 2005 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 • resistance welded • 0.25 mm of copper for thermal conductivity. • T increase by ~ 23 X • For, Q = 10W, T = 200C • Issues • Overheated the attenuators that were added for the additional HOM power that would be coming out of the transmission line. • Resistance welds may fail and lead to arcing. • Does not appear to be a viable solution. Vacuum System p.5

  6. 2006 LER Arc BPM Upgrade • 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. • 50-150 lbs, • average was ~ 60 lbs (excluding outliers). • Pressed molybdenum buttons • 100-600 lbs • 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.6

  7. Design – BPM Retrofit • Current Plan • Re-design press fit to reduce force and increase tolerance band. • Taper and reduce press fit region. • Pros • Does not require significant design effort. • 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). • Cost Estimate (N. Reeck) – consistent with AIP budget • Retrofit of the BPM • Indirect Cost: $339.65 each including 28% contingency • Installation • Indirect Cost: $168 each • Cost does not include helicoflex seal Vacuum System p.7

  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 • design exists • Alumina – better thermal conductivity • 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 • Needs testing • Dielectric constant 2 X higher than glass. • New vendor – not much reliability data. • Not electrically equivalent to remaining BPMs • Schedule Vacuum System p.8

  9. Alumina Feedthru Layout Drawing Vacuum System p.9

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

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

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

  13. IR2 BPM Upgrade Plan • Remove 15 mm button and leave 2.4 mm center pin as button. • Attempt to remove buttons in situ without removing chambers if possible. • Buttons will be leak checked from the reverse side if space permits. • 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.13

  14. BPM Removal Tool Vacuum System p.14

  15. Summary • HER arcs and LER/HER straights BPM’s do not require an upgrade at this time. • 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. • Will need full support from physicists for RF/HOM analysis because the design & procurement cycle is long for new BPMs. Vacuum System p.15

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