1 RHIC II – Ion Operation Wolfram Fischer RHIC II Workshop, BNL – Working Group: Equation of State 27 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-coolingwith e-cooling Emittance (95%)  m15   10 Beta function at IR [m] Number of bunches Bunch population [10 9 ]11  0.3 Beam-beam parameter per IR Peak luminosity [10 26 cm -2 s -1 ]3290 Ave. store luminosity [10 26 cm -2 s -1 ]870 Polarized proton collision (250 GeV  250 GeV): Emittance (95%)  m2012 Beta function at IR [m] Number of bunches Bunch population [10 11 ]22 Beam-beam parameter per IR Ave. store luminosity [10 30 cm -2 s -1 ] 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 0.5h1.5h Beam and luminosity lifetime for Au – Au dominated by IBS [Factor 10 between Au an p]

Wolfram Fischer 6 Intrabeam scattering: RHIC luminosity with electron cooling Transverse beam profile during store Also may be able to pre-cool polarized protons at injection energy with e-cooling without 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 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

Wolfram Fischer 8 Maximum luminosity estimates: p-p, Au-Au, U-U

Wolfram Fischer 9 Maximum luminosity estimates: p-p and Au-Au

Wolfram Fischer 10 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 beams injection/ramp: no modulated beam-beam (problem for LHC) store : maintains luminosity and vertex 250GeV p on 100GeV/n Au: not possible equal f rev not possible, expect luminosity reduction of at least 1000  Can possibly collide 120GeV p on 100GeV/n Au expect 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 scaling depends 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, 3 He) Asymmetric collisions need same  for both beams –Easiest for d-A

13 RHIC II – Polarized Proton Operation Wolfram Fischer RHIC II Workshop, BNL – Working Group: Spin and pp 27 April 2005

Wolfram Fischer 14 RHIC polarized proton accelerator complex

Wolfram Fischer 15 Gold collisions (100 GeV/n  100 GeV/n): w/o e-coolingwith e-cooling Emittance (95%)  m15   10 Beta function at IR [m] Number of bunches Bunch population [10 9 ]11  0.3 Beam-beam parameter per IR Peak luminosity [10 26 cm -2 s -1 ]3290 Ave. store luminosity [10 26 cm -2 s -1 ]870 Polarized proton collision (250 GeV  250 GeV): Emittance (95%)  m2012 Beta function at IR [m] Number of bunches Bunch population [10 11 ]22 Beam-beam parameter per IR Ave. store luminosity [10 30 cm -2 s -1 ] 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 N b /  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%

Wolfram Fischer 17 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)

Wolfram Fischer 18 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]

Wolfram Fischer 19 Polarized species other then protons (with EBIS options) Polarized d + –Would need new RFQ or source (~$0.5m) –Intensity: 1  /bunch –Polarization: needs study, longitudinal difficult –Luminosity scale factor: 0.5  L pp Polarized 3 He 2+ –Intensity: up to 2  /bunch –Polarization: ~ 15% < than p –Luminosity scale factor: 1  L pp

Wolfram Fischer 20 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 3 He 2+ and d + (difficult) beams