f AEM - 22 Jan 07 Separator Spark History Ron Moore Fermilab – Tevatron Dept.

f AEM - 22 Jan 07R. Moore - FNAL2 Overview Separator sparks can cause emittance growth and quenches via momentary orbit distortions –Beam separation decreases –Beam kicked into collimators History in HEP shots/stores since Nov 02 Based on spark counters –Confirmed with other effects: Schottky noise, emittance blow-up, vacuum in separator after spark Two groups –Flattop/squeeze: B17H and C17V run hardest –When colliding: everything else Click on link for Spark History on Tev Web SiteSpark History on Tev Web Site

f AEM - 22 Jan 07R. Moore - FNAL3 Separator Station Locations 27 separator modules – all stations have polarity switches B17 & C17 run hardest near flattop and in squeeze (120 kV/plate → 48 kV/cm) Units around IPs & D17 run hardest for collisions (≈100 kV/plate → 40 kV/cm) Horizontal# modulesVertical# modules A171 1 A491 2 B112 1 B174B481 C174 C491 2 D112 1 D481D172

71 entries 21 “store-killers” Thicker lines  sparks occurring closer together Shutdown

f AEM - 22 Jan 07R. Moore - FNAL5 B17H/C17V Run hardest on ramp and in squeeze No B17H-1, C17V-2, C17V-3 sparks C17V-1 most often –Shot 4084 quench Fewer sparks since Jan 05 – stopped ramping on pbar helix B17H-2 HEP spark 12/22/06 –Mistakenly on pbar flattop for short period before shot-setup

f AEM - 22 Jan 07R. Moore - FNAL6 B17H / C17V Shutdown Fewer sparks since Jan 05 – stopped ramping on pbar helix

f AEM - 22 Jan 07R. Moore - FNAL7 Dec 04 Startup During shutdown, polarity switches installed on all separators; C49/D11 aligned? After rash of sparks (trying larger helix) from normally OK seps (C49, D11), did another round of conditioning – some in wrong polarity - sparked next store This explains why we avoid changing polarities without reconditioning time

f AEM - 22 Jan 07R. Moore - FNAL8 B11H/V 13 incidents –11 “store killers” Note clumps… Spring 04 & Dec 04 –Trying larger collision helix –Start-up after 2004 shutdown Nov-Dec 05 –B11 separator RGA leak  higher cold beam tube + separator vacuum –Store 4515 spark led to B17 spool piece failure –Leaky feed-through replaced

f AEM - 22 Jan 07R. Moore - FNAL9 A49H/V A49V sparks when trying larger collision helix (Dec 04, spring 05) led us to replace A49 separators with better conditioned ones in 2006 New A49H-1 sparked 3 times soon after start-up…OK for few months Have not tried increasing voltage / enlarging helix since then 9 incidents 5 quenches 1 BIG emittance jump rendering store useless

f AEM - 22 Jan 07R. Moore - FNAL10 D17V D17V likely “contaminated” in October D32-5 failure - electrical arc through beam pipe  much of D sector had terrible vacuum for some time Sparked at low operating voltages, little impact on beam (fortunately) D17V was conditioned extensively during shutdown and subsequent E39 cryo leak repair Has finally settled down – no sparks in 2 months (insert kiss of death here)

f AEM - 22 Jan 07R. Moore - FNAL11 Summary 71 spark incidents in HEP operation in ≈4 years –Nearly 1/3 were “store-killers” = quenches or big lumi drop –≈40% were “self-inflicted” = higher voltages, poor vacuum, after conditioning in wrong polarity B17H and C17V separators spark less frequently up ramp/at flattop since stopping ramping on pbar helix (≈Jan 2005) Running with poor separator vacuum is not a good idea –See B11 incidents in Nov 05 –Take time to fix the problem right Be careful trying larger voltages and changing polarities –Don’t want store-killers becoming Tevatron-killers (avoid quenches)

f AEM - 22 Jan 07R. Moore - FNAL12 HV Electrode feedthru Titanium Sublimation Pump Flexible Support Rigid Support Heater Ion Pump Tevatron Electrostatic Separator Components This is a horizontal separator… …insulating blankets not shown

f AEM - 22 Jan 07R. Moore - FNAL13 Others 4 “store-killers” C49 mainly negative only D11 all but one during Dec 04 startup with larger helix