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Operational improvements to pbar mining in Recycler

Operational improvements to pbar mining in Recycler. Chandra Bhat Recycler Department B. Chase and P. Joireman, RF Group C. Gattuso, Run Co. Group All Experimenters Meeting April 9, 2007.

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Operational improvements to pbar mining in Recycler

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  1. Operational improvements to pbar mining in Recycler Chandra BhatRecycler Department B. Chase and P. Joireman, RF Group C. Gattuso, Run Co. Group All Experimenters Meeting April 9, 2007

  2. Pbars are extracted from the Recycler for Tevatron shots using longitudinal momentum mining. implemented Feb. 20, 2004 • The mining is accomplished by RF manipulations of the beam using Recycler barrier rf buckets.

  3. 11sec Phase-space distribution of pbars in the RR Barrier Bucket & Beam In the bucket RF wave form Frequency Spectrum WCM data of pbars Cold Beam  High momentum tail Synchronous Particles Pbars cooled using E-cooling & Stochastic cooling

  4. Bucket Area=71eVs (Reserved for particles in the tail region) V (kV) V (kV) 9-Mining mini-buckets <10.25eVs <10.25eVs 36bkts 36bkts sec sec 2.5 2.5 m m sec sec 6.1 6.1 m m After Mining m m 11 11 sec (588 sec (588 bkts bkts ) ) These RF manipulations take ~170 sec. These RF manipulations take ~170 sec. Before Mining ~300E10 pbar 21-38E10 pbars/mini-bunch LE=6.0 eVs/mini-bunch e_T= 5 pi-mm-mr 10E10pbrs in HM bkt  0.7-1.2 ~300E10 pbar LE(initial)=67 eVs e_T = 5 pi-mm-mr RF Waveform  0.9 WCM Data of pbars Longitudinal Momentum Mining in the Recycler Goal: Extract equal intensity Equal emittance pbars Physics and first demo of long. momentum mining: C. M. Bhat, Phys. Lett. A 330 (2004) 481

  5. Issues • Poor Life-time and transverse emittance growth during mining caused by non-optimal tunes • Large peak density at low emittances and higher intensities  caused by hard mini-barriers • About 20% longitudinal emittance growth during the formation of four 2.5 MHz bunches for Tev shots  non-adiabatic bunch explanation • Distortions of the Recycler fan out signals due the HLRF amplifiers(Solved by adaptive RF Corrections since Oct. 2006, by Nathan Eddy, et al,All experimenter’s Meeting, Feb. 26, 2007) • Beam becoming unstable at higher stash sizes and low emittances  due to resistive wall instability(Solved by use of Transverse Dampers since Aug. 23, 2005, by J. Crisp, et al. ) Made improvements in all of these with a goal of reaching the Recycler stash size of >600E10 pbars

  6. 1. New tune operating pointssince Aug. 22, 2006(A. Burov, et al. from a theoretical study) Store=4917 New Tunes (0.456, 0.465) Store=4915 Old Tunes (0.414, 0.422) RR-Beam RR-Beam H V V H R:SHLIFE =2000 hr D=1.31 (xE10/mm/eVs) R:SHLIFE =112 hr D=2.12 (xE10/mm/eVs) Average Trans. Emit. Variation ~ 30% and an RMS spread <10% Average Trans. Emit. Variation > 200% and an RMS spread of 30% Result: Nearly constant transverse emittance pbars to the Tevatron

  7. 2. Issues with hard Barriers V 2kV t • Peak particle density is too high. • RF Voltage modulation • RF Phase-modulation  phase modulation can coherently perturb the particle motion. Lead to beam losses from the bucket boundary Conclusions: The rf voltage and phase modulations are detrimental to the beam stability in back to back barrier buckets. 2kV 2kV In 50 sec In 50 sec K. Y. Ng, PRST AB, V9, 064001 (2006)

  8. 2kV 2kV 0.2s 0.7s 0.7s RF Waveform WCM data Reduced peak density Implement Soft-mining buckets Mining looks like Hard mini-bucket Soft mini-bucket • Replaced the 9-mining buckets from Since Nov. 30, 2006 Expected:

  9. Before and After Soft-mining 5097 Hard mining Peak Intensity 5123 Soft-mining Peak Intensity RR-Beam RR-Beam V V H H Peak intensity got reduced by 35%

  10. 3. 2.5 MHz pbar bunches by Morphing Before March 20, 2007 2.5 MHz Bunches Mini-bunch after mining Stretch 20-30% longitudinal emittance growth; takes ~75 sec Since March 21, 2007 Morph 2kV 2kV 2kV 2kV 2kV 2kV 0.7 0.7 0.7 s s s m m m 2.5 MHz Bunches Mini-bunch after mining Capture in 7.5 MHz <10% longitudinal emittance growth and takes ~60 sec

  11. Extraction Reg. Pbar bunches for Tev shots by Morphing for 3rd transfer RF Waveform Extraction region WCM Data

  12. Accomplishments • Peak density is reduced by ~35%. • So, in future we can increase the bunch intensity • Better LE (<10% growth) pbar bunches to the Tevatron • The bunch by bunch transverse emittance variation is reduced from 200% to 30% • With the adaptive RF correction we can send nearly equal intensity pbars bunches to Tevatron The bunch-to-bunch luminosity variations in the Tevatron were routinely factors of 2-3. Sometimes >5. Recently, the luminosity variations are only 20-25%,

  13. Tevatron Bunch-by-bunch Luminosity variation PAST and PRESENT PAST Store 4915 Without improvements: Luminosity variation >200% PRESENT Store 5306 With Improvements: Luminosity variation <15%

  14. Backup

  15. Highest peak luminosity store (5245) Current performance

  16. Adaptive RF CorrectionsNathan Eddy, et al (All experimenter’s Meeting, Feb. 26, 2007) Distortions of the Recycler fan back signals were leading to Bunch intensity variation >200% & RMS intensity spread ~25% Developed a FPGA based adaptive RF correction system. Result: Bunch intensity variation >33% & RMS intensity spread ~6%

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