Winter Workshop, San Diego Mar 16, 2006Angelika Drees Short- and Long-term Future of RHIC Introduction Luminosity, Luminosity Limitations Runs so far and Run 06 Short and intermediate Term Future Long Term Future

Winter Workshop, San Diego Mar 16, 2006Angelika Drees The Roadmap Enhanced Design 2008 RHIC design Achieved 2005 RHIC II ≥ 2012 eRHIC e-p, e-Au, Au-Au? ≥ 2017 other options: d-Au Si-Si, ?-? low energy p, Si, Au, Cu …. (almost) anything else Au-Au during eRHIC aera at practically no additional cost! depending on … construction could begin 2013

Winter Workshop, San Diego Mar 16, 2006Angelika Drees Luminosity The luminosity can be increased if: o There is more beam/bunch in the two rings (N B,N Y ) o There are more bunches colliding (k b ) o The beam profiles, the size of the beam, at the interaction point, is small (  x,  y ) ->  * To reach RHIC enhanced and RHIC II luminosities, there are several luminosity limitations to overcome (IBS, beam-beam, instabilities, pressure rise ….)

Winter Workshop, San Diego Mar 16, 2006Angelika Drees Intra-Beam Scattering (IBS) in RHIC Longitudinal emittance growth causes debunching (bunched beam lifetime) => stochastic cooling will allow up to 50% more beam/bunch Main contribution to transverse IBS in RHIC comes from the arcs (FODO lattice) l Longitudinal and transverse emittance growth agrees well with model l Some additional source of transverse emittance growth l IBS determines/limits RHIC Au and HI performance l Eventually will need electron cooling

Winter Workshop, San Diego Mar 16, 2006Angelika Drees Emittance Growth during the Ramp beginning of ramp transition end of ramp Two ramps during the 05 Cu- Cu run bottom: before chromaticity adjustment top: after chromaticity adjustment emittance growth of up to 100% still remains (not understood yet) chromaticity: dq/q=  dp/p (tune change as a function of momentum change)

Winter Workshop, San Diego Mar 16, 2006Angelika Drees Beam Growth during a Store blue and yellow emittances during 3 Cu stores, Jan. 30, 2005 Norm. emittances between 15 and 20  mm mrad grow up to 35  mm mrad at the end of store => IBS + beam-beam bunch by bunch emittance measured during a Cu store Jan 31, Bunch1 is affected by the gap cleaning procedure, bunch 19,37,121 have 4 collision points, bunch 100 has only 3 => beam- beam causes additional emittance growth.

Winter Workshop, San Diego Mar 16, 2006Angelika Drees What did we do so far? species # bunches Ions/bunch [10 9 ]  * [m] Emittance [  m] L peak [cm -2 s -1 ] L store avg. [cm -2 s -1 ] L week [cm -2 s -1 ] Au-Au  b -1 Cu-Cu nb -1 dAu55110d/0.7Au nb -1 pp pb -1 target

Winter Workshop, San Diego Mar 16, 2006Angelika Drees Run 05 Cu-Cu Summary Accomplishments in Run05 (Cu-Cu) –250 m NEG coated pipes Installed –start-up & ramp-up in 2.5 weeks –running at beam-beam limit with 4 IRs –b* reduced by 10% to 0.9 m at STAR –74% and 82 % of calendar time in store (31.5 and 11.2 GeV)

Winter Workshop, San Diego Mar 16, 2006Angelika Drees Run 05 pp Summary 100 GeV: –polarized source upgraded –60% pol. at AGS extraction –1 st acc. of pol. protons in AGS with cold snake –up to 111 bunches/ring –store pol. up 5% 205 GeV: –setup in 3 days –1 st acc. and stor. of pp > 100 GeV –30% pol. at this energy AGS cold snake: –10 11 protons/bunch, 50% pol.

Winter Workshop, San Diego Mar 16, 2006Angelika Drees Run06 Predictions and Plans 20 cryo weeks (14 ½ weeks of physics) pp at 100 GeV, 31.2 GeV, (250 GeV, 11 GeV) Improvements : –further AGS cold snake commissioning -> polarization –430 m of NEG coated beam pipes -> intensity –arc vacuum now Torr before cool down -> intensity –IR triplets disconnected from ceiling -> reproducibility –10 Hz orbit feedback under construction -> luminosity projected maximum projected minimum achieved in run 05 p/bunch: 0.9 → number of bunches: 106 → 111 polarization: 47 % → 60 %

Winter Workshop, San Diego Mar 16, 2006Angelika Drees RHIC these days … 30% more emittance blow up in 84x84 stores (?) normalized luminosity 56x556 84x84

Winter Workshop, San Diego Mar 16, 2006Angelika Drees RHIC’s ramp efficiency this week …. Transmission efficiency: 97.5% (blue), 97.5 % (yellow) polarization at store: 50% (blue), 54% (yellow) emittances: ~35  mm mrad in both rings 108x108 ramp Thursday night

Winter Workshop, San Diego Mar 16, 2006Angelika Drees RHIC Low-Energy Options Why? We like challenges and you search for the critical point on the QCD phase diagram (somewhere between √s 5-50 GeV, E beam GeV) challenges: –below injection: field quality, IBS, emittance, cooling, injection kickers at low voltage … luminosity scaling and monitoring –above injection energy: transition energy modification, ramps can’t run close to transition! 2.5 GeV min. E inj. 9.8 GeV current RHIC E inj. 12 GeV max. RHIC E inj GeV mod. p  T from GeV nom. Au  T ~25 GeV max. E store rampinject 1 GeV AGS E inj. 8 GeV AGS Au E T

Winter Workshop, San Diego Mar 16, 2006Angelika Drees Luminosity and b 2 scaling ( GeV)  2 scaling applies above injection energies no obvious scaling below –injected beam fills aperture –magnetic field quality degrades strawman model:  3 -  4 magnet currents scale with  we don’t have magnet measurements at very low currents (field quality deteriorates quickly!) –extrapolate field for simulations –low-current magnet measurements are necessary uncertain

Winter Workshop, San Diego Mar 16, 2006Angelika Drees Machine projections for low energy assume  3 luminosity scaling below 10 GeV study  * benefits vs. aperture problems projections do not include potential improvements –cooling: stochastic or electron –IBS minimizing lattice –vacuum improvements allow higher bunch intensity ModeBeam Energy [GeV/u] N bunches Ions/bunch [  9 ]  * [m] Emittance [  m] L peak [cm -2 s -1 ] Au-Au  Au-Au  Au-Au  Au-Au  Au-Au  T. Satogata

Winter Workshop, San Diego Mar 16, 2006Angelika Drees Luminosity Monitoring BBC ZDC Data from the 10 GeV run in Expect 30 min. 5 GeV. Statistically the ZDCs are already at their limits. Light production depends on n-energy, not enough at 2.5 GeV! The BBC statistic still ok but BBC location not optimal for low energies. Neither BBC nor ZDC seem suitable for very low energy monitoring => need new detector?

Winter Workshop, San Diego Mar 16, 2006Angelika Drees Can we do Low Energy? Yes, but … no obvious show stoppers below 10 GeV but we need some dedicated studies: –study IBS suppression lattice (growth time 250 s – 5000 s) –measure field for low currents –install special luminosity monitors ramping required above 12 GeV –study transition energy modifications –similar to normal HI operation, 2-3 days setup per energy point cooling at low energies –low energies likely require cooling or different lattice! –electron cooling promising (cooling times of ~200 s), use electron-gun developped for e-cooling –stochastic cooling under consideration & investigation

Winter Workshop, San Diego Mar 16, 2006Angelika Drees RHIC II: Luminosity upgrades need ecooling for this!

Winter Workshop, San Diego Mar 16, 2006Angelika Drees RHIC II upgrade: e-cooling 3 h luminosity lifetime increase luminosity by overcoming IBS and reducing emittance growth –increase the integrated HI luminosity by x10, also higher pp luminosity (feasibility studied by BINP) –increase e-Au and e-p luminosity, shorten ion bunches requires high power, high brightness energy recovering linac (ERL) 10x more cooling than current record (FNAL) Bunched electron beam requirements for 100 GeV/u gold beams: E = 54 MeV, ~ A, electron beam power: ~ 5 MW!

Winter Workshop, San Diego Mar 16, 2006Angelika Drees RHIC II Luminosities with e-Cooling LinacRf Gun Buncher Cavity Cooling Solenoid (~ 60 m, ~ 1 T) Debuncher Cavity e-Beam Dump Gold beam Gold collisions (100 GeV/n x 100 GeV/n): w/o e-coolingwith e-cooling Emittance (95%)  m15   3 Beta function at IR [m]  0.5 Number of bunches Bunch population [10 9 ]11  0.3 Beam-beam parameter per IR Peak luminosity [10 26 cm -2 s -1 ]3290 Average luminosity [10 26 cm -2 s -1 ]870 First linac based, bunched electron beam cooling system used at a collider First high p t electron cooler to avoid recombination of e- and Au79+ Maintains present bunch spacing (~ 100 ns) and available IR length magnetized design outdated!

Winter Workshop, San Diego Mar 16, 2006Angelika Drees e-cooling subsystems and status Infrastructure RF systems Magnets SRF gun 5-cell cavity Injection, supports, beam-dump, RHIC lattice close to completion in or on their way 80% designed and send for quotes advanced design phase in preparation for assembly preliminary design stage system status

Winter Workshop, San Diego Mar 16, 2006Angelika Drees e-cooling parameters both, classical and magnetized cooling will work for RHIC classical cooling allows to use one ERL for both rings, lower cost, prevents dense core, easier significant number of reserves in the system (IBS suppression lattice, ….)

Winter Workshop, San Diego Mar 16, 2006Angelika Drees eRHIC Project Scope two possible designs –ring-ring (main design) –ring-linac (under consideration) should provide –5-10 GeV 70%  e - –10 GeV 70%  e+ – GeV 70%  p –100 GeV Au (+ 3 He, +?) -> EBIS luminosities – cm -2 s -1 for e-p – cm -2 s -1 for e-Au ion ring upgrades –increase I ion, # bunches –injection & abort kicker –long range beam-beam –RF upgrades, cryogenic load –cooling for Au and p BNL, MIT-Bates, BINP, DESY provide e-ion, e-p collision in 1 IR allow ion-ion collisions in 2 IRs IR design crucial and difficult!

Winter Workshop, San Diego Mar 16, 2006Angelika Drees EBIS/Linac RHIC Pre-Injector Highly successful development of Electron Beam Ion Source (EBIS) at BNL EBIS allows for a reliable, low maintenance Linac-based pre-injector replacing the Tandem Van de Graaffs Produces beams of all ion species including Uranium and polarized 3 He (for eRHIC) Ready to start construction; Cost: 16.1 M$; Schedule: 2005/6 – 2008/9 EBIS test stand

Winter Workshop, San Diego Mar 16, 2006Angelika Drees Basic Beam Parameters for e-p collisions no cooling 2 p-p IPs assumed cooling needed no p-p IPs allowed V. Ptitsyn

Winter Workshop, San Diego Mar 16, 2006Angelika Drees Basic Beam Parameters for e-Au collisions e-cooling for the Au beam is required to achieve and maintain the promised emittance values. Au-Au collisions are allowed in 2 IPs at the same time. V. Ptitsyn

Winter Workshop, San Diego Mar 16, 2006Angelika Drees Design Issues need flexible emittance control to match energy range – mm mrad synchrotron radiation power accommodation –5 MW total power –9.5 kW/m load variable ring circumference –about 20 cm  C needed to match f rev at different p- energies polarization optimization –22 min self-polarization time for positrons e-beam is brought to collision directly from sc energy recovering linac –500 mA e current –10 GeV fixed energy no beam-beam limitation simpler polarization handling simpler IR design development of high current polarized electron source needed development of energy recovery technology for high energy and high current needed ring-ring ring-linac

Winter Workshop, San Diego Mar 16, 2006Angelika Drees RHIC demonstrated consistently satisfying performance in previous runs we are on track with the timeline and the predicted luminosities a low energy run between GeV is challenging but feasible within the next few years RHIC II luminosity upgrade requires e-cooling with high power and high current electron beams (x10 more than current record) choice of classical instead of magnetized cooling e-cooling R&D, design and construction in progress eRHIC main design is based on 5-10GeV e-ring and 10 GeV linac √s between GeV luminosities > cm -2 s -1 (e-p), cm -2 s -1 (e-Au) allows parallel operation of Au-Au IRs major challenges are increasing number of bunches for RHIC and synchrotron power load can be realized with present level of accelerator technology alternative designs are discussed (ERL only, ramping selfpolarizing e-ring) Summary

Winter Workshop, San Diego Mar 16, 2006Angelika Drees supplemental

Winter Workshop, San Diego Mar 16, 2006Angelika Drees IR design

Winter Workshop, San Diego Mar 16, 2006Angelika Drees Low IBS lattice and cooling

Winter Workshop, San Diego Mar 16, 2006Angelika Drees

Winter Workshop, San Diego Mar 16, 2006Angelika Drees Transition energy crossing RHIC is the first super conducting, slow ramping accelerator to cross transition energy  t (~ 23 GeV): What is “transition” ? ¯below transition fast particles arrive early at the RF ¯with increasing energy fast particles go more and more to the outside (Dispersion!) ¯above transition fast particles arrive late at the RF ¯at transition all particles arrive at the same time: short and unstable bunches! Cross unstable transition energy  t by rapidly changing transition energy (2001) using special quadrupoles: Beam energy RF t t

Winter Workshop, San Diego Mar 16, 2006Angelika Drees Linac Ring

Winter Workshop, San Diego Mar 16, 2006Angelika Drees EBIS layout