Recycler Operation and studies Week Nov. 10- Nov Meiqin Xiao

Operations We had transverse emittance blow up several times, which were related to the damper System:  The A-B amplifiers where replaced and a low pass filter were removed from the vertical damper on Thursday  Without the low pass filter, some higher harmonics have the wrong phase for damping. This was verified at ( ) and ( )frot Friday. The low pass filter has been restored and the phase advance has been verified.

 The transverse emittance appears to be blowing up (from flying wire data) (Saturday)  A huge response on the damp output. This is more indicative of a damper problem than a real instability.  Both the horizontal and vertical damper phases were checked. No large errors were found to account for the transverse emittance blowups noted over the weekend.

 Beam loss and emittance growth just as we were starting shot setup (Wednesday)  It was decided to switch the damper to the new upgrade. However, there are some problems with the new damper system and had to revert back to the old system.  The new system can be repaired/modified. But it’s not ready yet to re-install till now.  Currently we are on the old system, we wrote a procedure on what to do if the event occurs again.

Poor Transfer efficiency problem (over the weekend) Shot # Transfer Time Accumulator (mA) Recycler (e10) Eff (%) Start End unstashed Start End Stashed /10/ : /10/ : /10/ : /11/2006 1: /11/2006 4: /11/2006 7: The only thing that is certain at this point is that the majority of the beam loss happens on the transfer from Main Injector to Recycler.  We looked at the trim settings and orbits (beamline and ring), they were O.K.  We also examined Main Injector flying wire data and found no relationship between the profile and the efficiency of the transfers. Even with lower emittance beam, we had reduced transfer efficiencies(80%). It turns out that it’s due to a large energy mismatch between the Accumulator and the MI.

Pelletron tripped during the weekend, and re-set unproperly.  This event happened at a low Pelletron voltage. The gun was never closed and was emitting a beam, keeping the gun (BIASV) voltage at 12 kV. Increase of the Pelletron voltage increased radiation, tripping the Pelletron.  We already wrote a procedure and pasted on the web to guide on-call person to do the resetting if the Pelletron tripped again

Studies we have done Rapid transfer attempt – Cons & Dave VANDER MEULEN First two regular transfer just as a normal shot setup, and then return the Pbar source to stacking for 15 min while leaving the recycler in the shot setup mode, then the rapid transfer of 1 parcel of beam to the recycler. Success!!!, able to transfer in 91 sec stacking to stacking, efficiency: ~87%

With the current mining waveforms the peak pbar density and energy spread is large – not good from the point of beam stability Schematic of Current Mining Improvements in Momentum Mining for Tevatron Shots – Chandra

Comparing current and proposed mining Current Mining Proposed Mining Mini-Bucket Sharp Rise Softer (190ns) 185E10pbars RF Waveform 245E10pbars

Comparison of WCM data 15.5E10 pbars  T(H,V)~(3.1,2.9)pi LT~1400 hrs (061010)* 27.2E10 pbars  T(H,V)~(8,8)pi LT~700 hrs (061113) Conclusions: For the same bunch intensity the peak density can be reduced by a factor of ~ 2 by using ( ) type bucket Total intensity normalized to unity Current Proposed 20.5E10 pbars  T(H,V)~(6, 7)pi (~5% reduction during cooling for about 30 min) LT~600hrs (060828)

Studies request Apply soft mining bucket for Tev shot – Chandra Boomerang study – Cons BPM response to local 3-bump at 702 BL22 to check QM702 – Cons, Meiqin