1 rhic ii – ion operation wolfram fischer rhic ii workshop, bnl – working group: equation of...
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Wolfram Fischer 3 Planned location at the end of the 200 MeV linac J. AlessiTRANSCRIPT
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RHIC II – Ion Operation
Wolfram Fischer
RHIC II Workshop, BNL – Working Group: Equation of State27 April 2005
Wolfram Fischer 2
EBIS Test Stand (~50% of EBIS)
J. Alessi
Wolfram Fischer 3
Planned location at the end of the 200 MeV linac
J. Alessi
Wolfram Fischer 4
Gold collisions (100 GeV/n 100 GeV/n): w/o e-cooling with e-coolingEmittance (95%) m 15 40 15 10Beta function at IR [m] 1.0 1.0Number of bunches 112 112Bunch population [109] 1 1 0.3Beam-beam parameter per IR 0.0016 0.004Peak luminosity [1026 cm-2 s-1] 32 90Ave. store luminosity [1026 cm-2 s-1] 8 70
Polarized proton collision (250 GeV 250 GeV):Emittance (95%) m 20 12Beta function at IR [m] 1.0 0.5Number of bunches 112 112Bunch population [1011] 2 2Beam-beam parameter per IR 0.007 0.012Ave. store luminosity [1030 cm-2 s-1] 150 500
RHIC II Luminosities with Electron Cooling
Wolfram Fischer 5
Intrabeam scattering: short luminosity lifetime
• Debunching requires continuous abort gap cleaning• Luminosity lifetime requires frequent refills• Ultimately need cooling at full energy
Intensities
Luminosities 2.5h
0.5h 1.5h
Beam andluminositylifetime for Au – Audominatedby IBS
nAZ
2
41
[Factor 10 between Au an p]
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Intrabeam scattering: RHIC luminosity with electron cooling
0
20
40
60
80
100
0 1 2 3 4 5
Time, hours
Lum
inos
ity, 1
026 c
m-2
s-1
Transverse beam profile during store
Also may be able to pre-cool polarized protons at injection energy
with e-coolingwithout e-cooling
Luminosity leveling through continuously adjusted cooling
Store length limited to 4 hours by “burn-off”
Four IRs with two at high luminosity
2 mm
5 hours
Wolfram Fischer 7
Setup times
Setup times for different modes• Achieved initial ion setup in 2.5 weeks
may reach 1-1.5 weeks (excluding major downtime)
• Achieved reduction in energy in 2-3 days may reach 1 day (excluding major downtime)
• Achieved polarized pp setup in 3 weeks may reach 1-2 weeks (excluding major downtime)
• Achieved ramp-up to maximum luminosity in physics in 4-5 weeks some improvement possible
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Maximum luminosity estimates: p-p, Au-Au, U-U
Maximum Luminosity Estimates for RHIC IIBeams unit p p Au UCharge number Z … 1 1 79 92Mass number A … 1 1 197 238Relativistic … 108 271 107 107Revolution frequency kHz 78.2 78.2 78.2 78.2Normalised emittance, 95%, min mm mrad 12 12 10 10
Ions/bunch, initial 109 200 200 1.0 0.9
Charges per bunch 109e 200 200 80 80No of bunches … 110 110 110 110Average beam current/ring mA 275 275 110 110Luminosity at one IP unit p-p p-p Au-Au U-UBeam-beam parameter per IP … 0.0123 0.0123 0.0024 0.0023
m 1.0 0.5 0.5 0.5
Peak luminosity 1030 cm-2s -1 150 750 90 67Peak / average luminosity … 1.5 1.5 1.3 1.3
Average store luminosity 1030 cm-2s -1 100 500 70 52Time in store % 55 55 60 60
Luminosity/week pb-133 166 2.5 1.9
Luminosity/week, achieved pb-10.9 0.16
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Maximum luminosity estimates: p-p and Au-Au
Maximum Luminosity Estimates for RHIC IIBeams unit Si Cu d p AuCharge number Z … 14 29 1 1 79Mass number A … 28 63 2 1 197Relativistic … 108 108 107 108 107Revolution frequency kHz 78.2 78.2 78.2 78 78.2Normalised emittance, 95%, min mm mrad 12 12 12 12 12
Ions/bunch, initial 109 10.7 5.2 150 200 1.0
Charges per bunch 109e 150 150 150 200 80No of bunches … 110 110 110 110 110Average beam current/ring mA 206 206 206 275 110Luminosity at one IP unit Si-Si Cu-Cu d-Au p-Au Au-AuBeam-beam parameter per IP … 0.0046 0.0043 0.0024 0.0048
0.0036 0.0048 m 1.0 1.0 2.0 2.0
Peak luminosity 1028 cm-2s -1 42 10 28 37Peak / average luminosity … 1.3 1.3 1.5 1.5
Average store luminosity 1028 cm-2s -1 32 8 19 25Time in store % 55 55 55 55
Luminosity/week nb-1108 25 62 83
Luminosity/week, achieved nb-12.4 4.5
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Comments on asymmetric collisions
Asymmetric species:• For p-Au collisions need to move DX magnets,
not necessary for d-Au collisions• Need to have same revolution frequencies ()
for both beamsinjection/ramp: no modulated beam-beam (problem for LHC)store : maintains luminosity and vertex
• 250GeV p on 100GeV/n Au: not possibleequal frev not possible, expect luminosity reduction of at least 1000
• Can possibly collide 120GeV p on 100GeV/n Auexpect considerable operational difficulties
Wolfram Fischer 11
Luminosity at different energies
L 2 for s 200 GeV/n without cooling [projections document]
– from energy dependent beam size– from from aperture limited in triplets
Light ions at low energies can be cooled. Gain over above scalingdepends on species, energy, and probably running time per mode.
No operation possible near transition.
Wolfram Fischer 12
Summary RHIC II
• Cooling aims for 10x heavy ion luminosity increase– Smaller increases for lighter ions
• Setup times– Species 1-2 weeks– New energy 1-2 days (energy reduction)
• EBIS (2009+) will allow – more efficient operation– new species (U, 3He)
• Asymmetric collisions need same for both beams– Easiest for d-A
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RHIC II – Polarized Proton Operation
Wolfram Fischer
RHIC II Workshop, BNL – Working Group: Spin and pp27 April 2005
Wolfram Fischer 14
RHIC polarized proton accelerator complex
Wolfram Fischer 15
Gold collisions (100 GeV/n 100 GeV/n): w/o e-cooling with e-coolingEmittance (95%) m 15 40 15 10Beta function at IR [m] 1.0 1.0Number of bunches 112 112Bunch population [109] 1 1 0.3Beam-beam parameter per IR 0.0016 0.004Peak luminosity [1026 cm-2 s-1] 32 90Ave. store luminosity [1026 cm-2 s-1] 8 70
Polarized proton collision (250 GeV 250 GeV):Emittance (95%) m 20 12Beta function at IR [m] 1.0 0.5Number of bunches 112 112Bunch population [1011] 2 2Beam-beam parameter per IR 0.007 0.012Ave. store luminosity [1030 cm-2 s-1] 150 500
RHIC II Luminosities with Electron Cooling
Wolfram Fischer 16
RHIC II pp luminosities with Electron Cooling
Notes:• pp luminosity limited by beam-beam effect
Cannot exceed certain brightness Nb/N
• Cooling at store not effective Pre-cooling at injection to increase brightness
• Expect only small improvements in polarization after AGS cold snake fully operational 70%+ average polarization at store
• Expect improvements in – Setup-time 3 weeks 1-2 weeks– Time in store 53% 60%
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Luminosity at different energies
L 2 for s 500 GeV [*=0.5m at s 500 GeV]
– from energy dependent beam size– from from aperture limited in triplets
2% for s = 63GeV (*=3.5m)
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Luminosities at different energies
• Dipoles have margin of up to 30% (may be only 20%) Operation may be possible up to s = 650 GeV
• Most of magnets (quadrupoles, snakes, …) also have margin• DX magnets don’t have margin
– 1.3 mrad crossing angle with current strength– 18 mrad crossing angle without DX
• Luminosity close to luminosity for s = 500 GeV (gain 30% with increase, loose about same amount with small crossing angle)
[W.W. MacKay et al., “Feasibility of increasing the energy of RHIC”, PAC 2001]
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Polarized species other then protons (with EBIS options)
• Polarized d+
– Would need new RFQ or source (~$0.5m)– Intensity : 11011/bunch– Polarization : needs study,
longitudinal difficult
– Luminosity scale factor : 0.5Lpp
• Polarized 3He2+
– Intensity : up to 21011/bunch– Polarization : ~ 15% < than p– Luminosity scale factor : 1Lpp
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Summary
With the RHIC-II luminosity upgrade:
• Expect factor 2-3 increase in pp luminosity • Expect only small improvements in polarization• Luminosity at lower energies scales with 2
• Operation at 20-30% higher energy possible• Can have polarized 3He2+ and d+ (difficult) beams