RHIC II

1
RHIC II Ion Operation

• Wolfram Fischer
• RHIC II Workshop, BNL Working Group Equation
  of State27 April 2005

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EBIS Test Stand (50 of EBIS)
J. Alessi
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Planned location at the end of the 200 MeV linac
J. Alessi
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RHIC II Luminosities with Electron Cooling

• Gold collisions (100 GeV/n ? 100 GeV/n) w/o
  e-cooling with e-cooling
• Emittance (95) mm 15 ? 40 15 ? 10
• Beta function at IR m 1.0 1.0
• Number of bunches 112 112
• Bunch population 109 1 1 ? 0.3
• Beam-beam parameter per IR 0.0016 0.004
• Peak luminosity 1026 cm-2 s-1 32 90
• Ave. store luminosity 1026 cm-2 s-1 8 70
• Polarized proton collision (250 GeV ? 250 GeV)
• Emittance (95) mm 20 12
• Beta function at IR m 1.0 0.5
• Number of bunches 112 112
• Bunch population 1011 2 2
• Beam-beam parameter per IR 0.007 0.012
• Ave. store luminosity 1030 cm-2 s-1 150 500

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Intrabeam scattering short luminosity lifetime
Beam andluminositylifetime for Au
Au dominated by IBS
Factor 10 between Au an p

• Debunching requires continuous abort gap
  cleaning
• Luminosity lifetime requires frequent refills
• Ultimately need cooling at full energy

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Intrabeam scattering RHIC luminosity with
electron cooling
Luminosity leveling through continuously
adjusted cooling Store length limited to 4
hours by burn-off Four IRs with two at high
luminosity
with e-cooling without e-cooling
Transverse beam profile during store Also may be
able to pre-cool polarized protons at injection
energy
5 hours
2 mm
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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
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Maximum luminosity estimates p-p and Au-Au
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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 (?g)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

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Luminosity at different energies

• L ? g2 for ?s ? 200 GeV/n without cooling
  projections document
• g from energy dependent beam size
• g from from aperture limited in triplets

No operation possible near transition.
Light ions at low energies can be cooled. Gain
over above scalingdepends on species, energy,
and probably running time per mode.
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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 g 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

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RHIC polarized proton accelerator complex
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RHIC II Luminosities with Electron Cooling

• Gold collisions (100 GeV/n ? 100 GeV/n) w/o
  e-cooling with e-cooling
• Emittance (95) mm 15 ? 40 15 ? 10
• Beta function at IR m 1.0 1.0
• Number of bunches 112 112
• Bunch population 109 1 1 ? 0.3
• Beam-beam parameter per IR 0.0016 0.004
• Peak luminosity 1026 cm-2 s-1 32 90
• Ave. store luminosity 1026 cm-2 s-1 8 70
• Polarized proton collision (250 GeV ? 250 GeV)
• Emittance (95) mm 20 12
• Beta function at IR m 1.0 0.5
• Number of bunches 112 112
• Bunch population 1011 2 2
• Beam-beam parameter per IR 0.007 0.012
• Ave. store luminosity 1030 cm-2 s-1 150 500

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RHIC II pp luminosities with Electron Cooling

• Notes
• pp luminosity limited by beam-beam effect ?
  Cannot exceed certain brightness Nb/eN
• 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 ? g2 for ?s ? 500 GeV b0.5m at ?s ? 500
  GeV
• g from energy dependent beam size
• g from from aperture limited in triplets

2 for ?s 63GeV (b3.5m)
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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 dont 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 g-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 1?1011/bunch
• Polarization needs study,
  longitudinal difficult
• Luminosity scale factor 0.5?Lpp
• Polarized 3He2
• Intensity up to 2?1011/bunch
• Polarization 15 lt than p
• Luminosity scale factor 1?Lpp

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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 g2
• Operation at 20-30 higher energy possible
• Can have polarized 3He2 and d (difficult) beams