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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 - PowerPoint PPT Presentation
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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
225GeV
Pol
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45%
Pol
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atio
n vs
. tun
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45%
218k147k
143k36k
profile
profile
Orbit correction
Horizontal target
30
35
40
45
50
55
0 0.01 0.02 0.03 0.04 0.05 0.06
tune
Pola
rizat
ion
4Qx+Qy-3.5055 5Qx
0.002
0.003
0.004
0.005
0.006
0.007
0.008
0.009
0.01
0.011
20 40 60 80 100 120 140 160 180 200 220 240
Beam Energy [GeV]
Asym
met
ry
d
Resonance around 138 GeV
0
0.002
0.004
0.006
0.008
0.01
0.012
20 40 60 80 100 120 140 160 180 200 220 240
Beam Energy [GeV]
Asym
met
ry
d
Resonance around 138 GeV
Yellow sextupole ramp too fast at the end of ramp
1st ring2ring synchro problem, fixed on Sunday evening
Qy Qx pol( )