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RHIC pp 500 GeV development

RHIC pp 500 GeV development. M. Bai C-A Department. Goals. Explore polarization transmission to a beam energy of 250 GeV Inspect the luminosity aspects (with 2 collisions): store lifetime, total intensity limits. Machine configuration. Ramp file: pp29 Beta* (IP6,IP8): 1.5m

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RHIC pp 500 GeV development

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  1. RHIC pp 500 GeV development M. Bai C-A Department

  2. Goals • Explore polarization transmission to a beam energy of 250 GeV • Inspect the luminosity aspects (with 2 collisions): store lifetime, total intensity limits

  3. Machine configuration • Ramp file: pp29 • Beta* (IP6,IP8): 1.5m • No crossing angles • Standard tune swing at 100Gev: • (.72;.73) -> (0.69, 0.68) • No rotators • H Jets off at injection and during ramp.

  4. Machine configuration

  5. Run layout • Power supply preparations: 2 shifts • Ramp and polarization development: 8 shifts • Dedicated polarization studies: 2 shifts • Dedicated luminosity studies: 2 shifts • Contingency shifts: 2.5 shifts • Total required: 16.5 shifts or ( 5 days +1.5 shifts) Beam-beam studies, total intensity limit studies and 1 shift of polarization on ramp studies will be only possible using contingency shifts.

  6. Overview of the development Yellow ps lead flow problem Fix the rf ring to ring synchro Booster problem, ps problem Ps problem, access control problem Weather related down time ps problem, access control problem Quench recovery ps work Booster problem Booster problem

  7. Actual time usage • Power supply preparations: 1.5 shifts • Injection setup: 1.0 shift • Ramp and polarization development: 5 shifts • Down time: 72.5 hours • power dip and other weather related problems: 44 hours • System failures

  8. What did we achieve and learn • Successfully accelerated both beams up to 250 GeV • Both beam went beyond 200 GeV during the very first ramp • A great help from tune/decoupling feedback to attack the strong coupling about half way between 200 GeV and 250GeV • Tune/quad tune feedback can’t handle the tune swing • No problem injecting beam with tune sitting below 0.7 • Significant polarization was measured at 250 GeV in Blue ring • Studied the polarization as a function of beam tunes at 250 GeV • Measured polarization as a function of energy during the very last two ramps.

  9. What did we miss • Exam the polarization transmission efficiency in Yellow • Systematic study of polarization along the energy ramp as function of orbit distortion and beam tunes at depolarization resonances beyond 100 GeV • Establish collisions to study the luminosity aspects at 250 GeV • Study the polarization lifetime as a function of beam tunes at 250 Gev

  10. What prevented us from reaching our goals • An unexpected strong coupling between 200 GeV and 250 GeV • A lot of downtime due to system failures • Lost a total of 44 hours due to bad weather from Saturday midnight till 8:00pm Sunday evening • A combination of yellow trim quad ps problem and rf ring2ring synchro problem, both weather related, also prevented any polarization development in the Yellow ring

  11. Future goals of RHIC polarized protons --- 70% store average • Polarization transmission efficiency • Avoid depolarization during the ramp • Understand the sensitivity of depolarization on orbit distortion • Realistic simulations • Systematic beam studies • Improve orbit correction • Precise tune/decoupling control • Eliminate the emittance growth during the ramp • Polarization lifetime at store • Working point at (0.695,0.685) has shown infinite polarization lifetime at store during the 100GeV operation. • At 250 GeV, the polarization lifetime can be more sensitive to the horizontal betatron tune due to the rotators. Hence, a scan of polarization lifetime as a function of betatron tunes at store is needed to find desirable working point.

  12. Acknowledgement • Derek, Tony, George for the 12 hours extension • Shift leaders: • Joanne, Jorg, Angelika, Wolfram, Todd, Christoph, Yun, SY, Alexi • Operations • Greg, and all the operation coordinators and operators • System experts • Tune/decoupling feedback: • Pete, Al • PS: George, Don, Carl, Chris, … • RF: Tom, Joe, … • CNI polarimeter: Sandro, Ron • Many others

  13. After yi2-tq6 and ring2ring synchro problems were fixed

  14. 225GeV

  15. Polarization vs. tune scan 45%

  16. Polarization vs. tune scan 45%

  17. Orbit correction Horizontal target 218k profile 147k 143k profile 36k

  18. Resonance around 138 GeV

  19. Resonance around 138 GeV

  20. Yellow sextupole ramp too fast at the end of ramp

  21. 1st ring2ring synchro problem, fixed on Sunday evening

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