RHIC Operations and Plans
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Transcript of RHIC Operations and Plans
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BROOKHAVEN SCIENCE ASSOCIATES
Electron Cooling at RHIC
Enhancement of Average Luminosity for Heavy Ion Collisions at RHIC
R&D Plans and Simulation Studies
8th ICFA SeminarKyungpook Natioanl University
Daegu, Korea, September 29, 2005
Satoshi Ozaki for the RHIC e-Cool TeamBrookhaven National Laboratory
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BROOKHAVEN SCIENCE ASSOCIATES
RHIC Operations and Plans
• Run 1: FY 2000 28 wks Au-Au (130 GeV/A)• Run 2:FY 2001-02 40 wks Au-Au (200 GeV/A) p↑-p↑ (200 GeV)• Run 3:FY 2003 29 wks d-Au (200 GeV/A) p↑-p↑ (200 GeV) ~30% Pol.• Run 4:FY 2004 27 wks Au-Au (200, 62 GeV/A) p↑-p↑ (200 GeV)• Run 5:FY 2005 32 wks Cu-Cu (200, 62 GeV/A) p↑-p↑ (200 GeV) ~50% Pol
Near term improvements in progress• Superconducting helical snakes in the AGS for higher polarization for FY 2006 Runs• Development of EBIS ion source for flexibility of ion operation
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BROOKHAVEN SCIENCE ASSOCIATES
First Five Years of RHIC Experiments
• The luminosity performance of RHIC for Au-Au & Cu-Cu collisions exceeded the design values.
• We observed creation of a new state of matter in Au-Au collisions at 200 GeV/A collision energy: – hot, dense and strongly coupled, – behaving like perfect fluid.
• Next stage of the program:– Study properties of the new state of matter– Study of rare processes Requires much higher
average/integrated luminosity
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BROOKHAVEN SCIENCE ASSOCIATES
Typical Au-Au Operation on Feb. 23, 2004
Au Beam Intensity vs. Time
Au-Au Luminosity vs. Time
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BROOKHAVEN SCIENCE ASSOCIATES
Control of Emittance Growth: Cooling
• The Au-Au luminosity life-time is only a few hours• Strong intra-beam scatterings cause emittance growth:
– Longitudinal: loss of ions from colliding buckets– Transverse: larger crossing beam spot size
• Cooling of ion beams: the key to a longer luminosity life-time: i.e., a higher average luminosity
• Cooling:– Stochastic cooling: more effective for hot beam
• Difficult for bunched Proton beams but it appears that it can work for heavy ion beams in RHIC
• Longitudinal cooling test in preparation– Electron cooling: more effective for cool beam
• It has been successful at lower energies but has not been demonstrated at high energy like RHIC
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BROOKHAVEN SCIENCE ASSOCIATES
The Objectives of RHIC e-Cooling and Challenges
• ~10 times Increase of RHIC average luminosity for Au-Au at 100 GeV/A
• Reduce background due to beam loss
• Keep short collision diamond by maintaining short bunch length to match detector’s acceptance
• Cooling rate slows in proportion to 7/2.
• Energy of electrons needed (54 MeV) is well above DC accelerators.
• Requires bunched e beam.
• Need exceptionally high electron bunch charge and low emittance.
• Need ERL to provide low emittance e-beam while maintaining a reasonable power demand.
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BROOKHAVEN SCIENCE ASSOCIATES
R&D: Theory Issues
• We must understand cooling physics in a new regime:
– understanding IBS, recombination, disintegration– binary collision simulations for benchmarking– experimental benchmarking of the magnetized cooling
efficiency issues
• Cooling dynamics simulations with precision
• A good estimate of the luminosity gain is essential.
• Simulations show that:10X increase in the average luminosity can be
achieved(from 7x1026 to ~7x1027 cm-2s-1)
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BROOKHAVEN SCIENCE ASSOCIATES
Parameters for of RHIC Magnetized e-cooling
Key e-beam parameters:– Bunch charge: q = 20nC– E-Beam Energy = 54MeV E/E < 3x10-4 – Emittance: 50m-rad– Magnetization: 380mm.mr
Energy Recovery Linac– fSRF: 703.5 MHz– Repetition rate: 9.4 MHz
Cooling solenoids:
2 x 40m long
B = 5T, B/B < 10-5
Collider operation:
Collisions at 3 IPs,
*=0.5m,
112 bunches
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BROOKHAVEN SCIENCE ASSOCIATES
Ne/bunch=3*1011
w/ cooling. *=0.5m
w/o cooling, *=1m
Simulation for Au-Au at 100 GeV/A
Luminosities per IP in cm-2sec-1 vs. time in seconds
The luminosity gain may be limited either by the collision beam burn out or the beam-beam parameter
X, Y, Z Distribution ()
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BROOKHAVEN SCIENCE ASSOCIATES
R&D: ERL and Cooling Hardware Issues
– Development of a high current low emittance RF Gun:– photocathode, laser, etc.
– Design of a high current & very low emittance ERL
– Development of beam diagnostics
– Beam dynamics studies
– Further refinements of simulation codes
– Development of high field solenoid with B/B<105
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BROOKHAVEN SCIENCE ASSOCIATES
Laser Photocathode S/C RF Gun: Key to performance
1 ½ cell gun designed for cooler
½ cell gun prototype: Under construction
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BROOKHAVEN SCIENCE ASSOCIATES
Diamond Amplified Photocathode
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0 5 10
Gradient (MV/m)
Ele
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5keV
4keV
3keV
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Electron Amplifying Diamond Window•Less demanding on laser power•Longer cathode life•Protect SC cavities from contamination
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BROOKHAVEN SCIENCE ASSOCIATES
Schematics for Magnetized Beam ERL Lattice
←Compressor Stretcher→
Gun Z-bend merger
Cooling solenoids in RHIC ring
ERL Beam Dump
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BROOKHAVEN SCIENCE ASSOCIATES
The Possibility of Non-magnetized Electron Cooling
• Handling of magnetized beams is not easy, and the system is complex and expensive.
• At high , achievable solenoid error limits the cooling speed of the magnetized cooling.
Another way is the non-magnetized e-cooling:• A study showed that sufficient cooling rates can be achieved
with non-magnetized cooling.• Recombination beam loss is a concern but can be managed
to be small enough to assure a long luminosity life-time– By reduced bunch charge– By larger beam size
• Helical undulator can further reduce recombination**Suggested by Derbenev, and independently by Litvinenko
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BROOKHAVEN SCIENCE ASSOCIATES
Non-magnetized Cooling: Parameters Beam Parameters:• Rms momentum spread of electrons =10-3
• Rms normalized emittance: 2.5 µmrad• Rms radius of electron beam in cooling section: 2.5 mm• Rms bunch length: 5 cm• Charge per bunch: 5nC (cf. 20nC for magnetized case)• Cooling sections: 2x30 m• Large ion beam in the cooling section: β* = 200 m
All ERL technology developments for mag-cool applies here but• without complex magnetized electron beam gun, • without bunch stretcher and compressor, and• without complex beam optics to preserve magnetization
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BROOKHAVEN SCIENCE ASSOCIATES
Non-magnetized Cooling: SimulationAu-Au at 100 GeV/A
Magnetized CoolingNon-magnetized Cooling: Luminosity
Non-magnetized Cooling: Emittance
Non-magnetized Cooling: Bunch Length
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BROOKHAVEN SCIENCE ASSOCIATES
Beam Loss Comparison: Simulation
Recombination: OffUndulators: Off
Recombination: ONUndulators: OFF
Recombination: ONUndulators: ON
Undulator parameters:50 Gauss, 5 cm period,Radius of rotation 1.7 m
Beam Intensity
Time (sec)
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BROOKHAVEN SCIENCE ASSOCIATES
R&D ERL Under Construction
To study the issues of high-brightness, high-current electron beams as needed for RHIC II and eRHIC.
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BROOKHAVEN SCIENCE ASSOCIATES
SRF Cavity for High Current (Ampere Class) ERL
703.5 MHz 5 Cell Cavity with Beam Tune HOM Damping:
Built by Advanced Energy Systems Inc. of Long Island
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BROOKHAVEN SCIENCE ASSOCIATES
RHIC e-Cooling Project Milestones & Collaborations
• 2005 Dec: Electron cooling simulation completed• 2006 Jan: Decision on the cooling method• 2006 Feb: High power rf system for the gun in place• 2006 Apr: 5-cell superconducting cavity delivered• 2006: Beam dynamics simulation• 2006: Cost and Schedule of e-cooling system for CD0• 2007 Mar: Begin testing S/C gun,
hopefully with the diamond cathode• 2008: Hope to begin testing of ERL hardware
• The Milestones subject to the future funding level
• Collaborators: BINP, JINR, Celsius, GSI. US Jefferson Lab, Fermilab, Indiana Univ., and industry (AES and Tech-X)
• Supported by: the U.S. DOE, Division of Nuclear Physics, and partially bythe U.S. DOD HE Laser Joint Tech Office and ONR