Post on 28-Dec-2015
transcript
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Near-term machine performance— The next 5 years, before e-cooling —
Wolfram FischerRun Coordinator for RHIC Run-4
Open Meeting on RHIC PlanningBerkner Hall
3 December 2003
Wolfram Fischer 2
Enhanced luminosity
• Enhanced Luminosity Goals (before e-cooling)
– For Au-Au, average per store (4 design)
L = 81026cm-2s-1 at 100GeV/u
– For p-p average per store, 2 IRs (16 design)
L = 61031cm-2s-1 at 100GeV
L = 1.51032cm-2s-1 at 250GeV
with 70% polarization
Wolfram Fischer 3
Contents
1. Assumptions for projections
2. Limitations and improvements• Injectors• Luminosity and background• Time at store
3. Run-4
4. 5-year projections
5. Summary
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RHIC Collider Projections
[annual updates based on experience gained in the previous run]
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Assumptions for projections
• 2 weeks for cool-down, 1 week for warm-up• For each mode (Au-Au, p-p, d-Au, etc.)
– 2 weeks of set-up [only machine operation]
– 3 weeks of ramp-up [machine operation with experimental set-up during owl shift]
– Continuous luminosity development in production[over 14 weeks during the day]
• Minimum and maximum projections– Minimum repeats demonstrated performance– Maximum requires completion of improvement projects– Maxima ambitious, likely outcome between min and max
• For 5-year luminosity projections– 5+14 weeks of operation in each mode– Only 2 collisions in p-p operation
Large penalty for frequent mode switches
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Collider performance comparisons
14 wks
14 wks
M. Lamont
14 wks
Common features - long runs (>14 wks/yr)- non-linear increase after shut-downs- many years for substantial increases
RHIC is of comparable complexity!
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Limitations (1) – injectors
• Bunch intensity and polarization– Achieved: Au 0.7109/bunch 10m 0.3eV·s
• Booster low level rf upgrade
• Additional bunch merge 1.3 109/bunch
– Achieved: p 0.81011/bunch 10m 0.3eV·s 40% pol.
– Achieved: p 2.01011/bunch 20m 0.5eV·s 20% pol. ?
• AGS warm helical snake in Run-4 40% pol. in RHIC
• AGS cold helical snake in Run-5 70% pol. in RHIC
• Later– New solenoid for polarized source
– 2nd AGS cold helical snake?
• EBIS (Electron Beam Ion Source)
– Earliest 2008, see presentation by J. Alessi
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Limitations (2) – luminosity and background
• Vacuum problems with high intensities Test of NEG coated beam pipes (low SEY, pumping) Solenoids
• Losses during ramp Better orbit, tune, coupling, chromaticity control PLL tune meter, tune feedback
• Experimental background Secondary collimators (½ this year, ½ next) Shielding (PHENIX, BRAHMS this year)
• Instabilities Improved chromaticity control, coherence monitor Transverse damper
• Intra-beam scattering (Au-Au) Stochastic cooling development e-cooling for RHIC II
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Limitations (3) – time in store
• Reduction of quench occurrences Reduce abort kicker pre-fires Avoid excessive beam losses
• Improve operational efficiency Faster down ramps (gain about 2 days/run) More automation at beginning of store (steering, collimation, gap cleaning) Better software tools for ramp tuning Faster injection set-up
• Reduce system downtime Eliminate ice ball maintenance at current leads Improve corrector power supply reliability Improve AtR reliability
• …
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Run-4 goals
• President’s budget allows for 27 weeks of cryogenic operation (need 3 weeks for cool-down and warm-up)
• Run-4 modes:
1. 5+14 weeks Au-Au at 100GeV/u beam energy,target luminosity of 300(b)-1 delivered
2. 5 weeks p development(partial warm AGS snake, gas jet, working point)
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Current status RHIC Run-4
• 5-week start-up/ramp-up period started on Monday 12/1/03
• Reached 0.8·109/bunch in Blue on Monday
• Blue: Injected 111 bunches with 0.5·109/bunch (pressure rise in bi8 and bo2, up to 10-6 Torr)
• Yellow: Injected 111 bunches with 0.1·109/bunch (no pressure rise observed)
• First ramps this morning– 6 bunches each
– 50% Blue transmission
– 40% Yellow transmission
Today at noon
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Projected 5-year Au-Au luminosity evolution
Assume- 14 weeks production in every year- linear luminosity increase during run- 4 experiments- completion of improvements
achieved projectedmaximum
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Projected 5-year p-p luminosity evolution
Assume- 14 weeks production in every year- linear luminosity increase during run- only 2 experiments- completion of improvements
achieved projectedmaximum
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Major RHIC improvements
Injectors
Luminosity and background
Time in store
New things to be filled in as we understand the machine better
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Summary
• Enhanced Luminosity Goals (before e-cooling)
– For Au-Au, average per store (4 design)
L = 81026cm-2s-1 at 100GeV/u
– For p-p average per store, 2 IRs (16 design)
L = 61031cm-2s-1 at 100GeV
L = 1.51032cm-2s-1 at 250GeV
with 70% polarization
• Required– Sufficient running time in each mode [many weeks/year]
– Resources to carry out improvement projects