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 No crossing angles Standard tune swing at 100Gev:

(.72;.73) -> (0.69, 0.68) No rotators H Jets off at injection and during ramp.

Machine configuration

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.

ps workWeather related down time

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Overview of the development

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

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 co

upling 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.

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

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

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.

Future goals of RHIC polarized protons --- 70% store average

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

Acknowledgement

After yi2-tq6 and ring2ring synchro problems were fixed

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Beam Energy [GeV]

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Yellow sextupole ramp too fast at the end of ramp

1st ring2ring synchro problem, fixed on Sunday evening

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