Transcript Electron Cooling of the Relativistic Heavy Ion Collider: Overview Ilan Ben-Zvi Collider-Accelerator Department Brookhaven National Laboratory I.

Electron Cooling of the
Relativistic Heavy Ion Collider:
Overview
Ilan Ben-Zvi
Collider-Accelerator Department
Brookhaven National Laboratory
I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004
Motivation
• The motivation for electron
cooling of RHIC is to increase
luminosity by reducing
emittance and overcoming
IBS.
– Increase the integrated
luminosity for gold on gold
collisions by an order of
magnitude, also higher P-P
luminosity (RHIC II).
– Increase the luminosity of
protons and ions on electrons
and shorten ion bunches
(eRHIC)
• Both RHIC II and eRHIC are
on the DOE’s 20 years
facilities plan.
RHIC luminosity decay (3.5 hours)
I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004
IP#12 - main
IP#10 - optional
Linac-ring eRHIC:
IP#2 - optional
Main-stream - 5-10 GeV eUp-gradable to 20+ GeV e-
Luminosity up to 1 x 1034 cm-2 sec-1 per nucleon
IP#4- optional
RHIC
Booster
AGS
I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004
What is special about cooling RHIC
The cooling takes place in the co-moving frame, where the ions and
electrons experience only their relative motion.
RHIC ion are ~100 times more energetic than a typical cooler ring.
Relativistic factors slow the cooling by at least factor of 2. So, first and
foremost, we must provide a factor of 2 more cooling power than typical.
Other points: Cooling of a bunched beam, cooling of a collider,
recombination and disintegration, use of a high-temperature electron
beam. Transport of a magnetized (angular momentum dominated) beam
without a continuous solenoid.
We cannot use conventional accelerator techniques. We require a highenergy (54 MeV), high-current (0.1 to 0.3 A) electron beam for the cooler,
based on an Energy Recovery Linac.
I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004
R&D issues
• High current, energetic, magnetized, cold
electron beam. Not done before
– Photoinjector (inc. photocathode, laser, etc.)
– ERL, at x100 the current of current JLAB ERL
– Beam dynamics study (magnetized beam AND
space-charge AND discontinuous solenoid)
• Understanding the cooling physics in a new
regime, must reduce uncertainty
– bunched beam, recombination, IBS, disintegration
– electron cooling simulations with some precision
• A very long, super-precise solenoid (30 m long,
1-2 Tesla, 8x10-6 error)
I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004
Structure of the
RHIC Electron Cooling R&D
Electron cooling R&D
Experimental R&D
Theory / simulations
ERL
Linac cavity
Guns
Laser,
photocathodes
Benchmarking
experiments
Beam dynamics
Also: Cost and schedule.
Work in progress.
I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004
Electron cooling
Friction, IBS
Dynamics
Electron cooling group (Reporting to
Thomas Roser) and collaborators.
Ilan Ben-Zvi, Vladimir Litvinenko, Andrew Burrill, Rama Calaga, Xiangyun
Chang, Alexei Fedotov, Dmitry Kairan, Joerg Kewisch, David Pate,
Mike Blaskiewicz, Yuri Eidelman, Harald Hahn, Ady Hershcovitch, Gary
McIntyre, Christoph Montag, Anthony Nicoletti, George Parzen, James
Rank, Joseph Scaduto, Alex Zaltsman,
Animesh Jain, Triveni Rao, Kuo-Chen Wu, Vitaly Yakimenko, Yongxiang Zhao.
GSI/INTAS collaboration: O. Boine-Frankenheim, others.
JLAB: J. Delayen, Ya. Derbenev, P. Kneisel, L. Merminga.
JINR (Dubna), Russia: I. Meshkov, A. Sidorin, A. Smirnov, G. Trubnikov
BINP, Russia: V. Parkhomchuk, A. Skrinsky, many others.
FNAL: A. Burov, S. Nagaitsev.
SLAC: D. Dowell.
Advanced Energy Systems: M. Cole, A. Burger, A. Favale, D. Holmes,
A. Todd, J. Rathke, T. Schultheiss.
Tech-X, Colorado: D. Abell, D. Bruhwiler, R. Busby, J. Cary.
I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004
Electron cooling theory, simulations
and benchmarking experiments
• Lead – Alexei Fedotov
Objective: Reduce the extremely large
uncertainty in calculating cooling rates,
develop new software tools and
benchmark them.
Status: Three software tools in various
stages of development. Expect solid
results in FY05.
I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004
Outstanding issues
1. Complete development of code and benchmarking, obtain
accurate estimates for cooling times.
2. Cooling with bunched electron beam.
3. Cooling with “hot” electrons: RHIC
Typical coolers
transverse :
1000 eV
0.1-1 eV
longitudinal :
50 meV
0.1 meV
4. Do we have sufficient magnetized cooling?
5. What are the optimum parameters for electron beam?
6. Detailed IBS.
7. Dynamics of the cooled ion beam, such as the impact on
threshold of collective instabilities.
I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004
Cooling gold at 100 GeV/A
Transverse
profile
Luminosity increase
I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004
Longitudinal
profile
Two-stage cooling
Pre-cooling protons at 27 GeV, Np=1x1011,
Betacool with Derbenev-Skrinsky formula.
Ne=5x1010 and 1x1011
Ne=1x1011
Subsequent emittance growth
at 250 GeV of initially
pre-cooled protons
I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004
Electron dynamics R&D
• Lead - Joerg Kewisch
The objective is a complete design of the electron
accelerator, including start-to-end simulation.
Understanding emittance growth under high
space-charge forces is important as well
transport and matching of magnetized electrons.
Status: Basic simulation tools at hand, initial startto-end simulation done, new understanding of
physics gained. To be completed in FY2006 with
a test.
I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004
Layout of RHIC electron cooler
Gun
ERL cavities
Beam
dump
Solenoid
Stretcher
Each electron bunch is used just once.
I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004
Layout
I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004
Parameters
Cooling Section:
Arcs:
Energy:
55 Mev
Energy spread: 1· 10-4
Bunch length:
15 cm
Bunch radius:
1mm
Emittance: 50 mm mrad
Solenoid:
1
Tesla
Linac:
700 MHz Cavities:
4
Gradient:
15 MV/m
2100 MHz Cavities:
3
Gradient:
7.5 MV/m
Power amplifiers: 50 kW
Max.Dispersion:
6m
Max. Beam Size (rms): 5 cm
Stretch factor:
33 m
Gun:
Normal Conducting
700 MHz
2½ Cell
Bunch charge:
10 nC
Bunch frequency:
9.8 MHz
Beam Energy:
2.5 MeV
Power:
1MW
I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004
Front to End Simulation: Beam
Size
alpha=6,Mag.Cath.100G,Fld=9Mv/m,Charge=10nc,phs=30,R=15mm,FWHM=4deg,B1=2.1
x vs distance
10.00
5.00
0.
-5.00
-10.000.
1600.00 3200.00 4800.00 6400.00 8000.00 9600.00 11200.00 12800.00 14400.00 16000.00
y vs distance
10.0
5.0
0.
-5.0
-10.00
1600
3200
4800
6400
8000
9600
11200
12800
I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004
14400
16000
Front to End Simulation:
Emittance
2

T [eV ]  me c 2  n2  0.511* ( n [mm mrad.])2

Method:
•Track electrons using
PARMELA including
space charge
•Apply linear
transformation to make
transport axial
symmetric, remove
dispersion
•Apply solenoid fringe
field matrix
•Measure emittance
I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004
Development of complete ERL
• Lead - Vladimir Litvinenko
The objective is to build an ERL comprising
a CW photoinjector, superconducting
cavity and beam transport and test it for
the RHIC/eRHIC current limits.
Status: Basic beam optics design done for
up to 0.5 amperes. Testing system in
2006.
I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004
ERL - Bldg. 912
e- 30-40 MeV
e- 15-20 MeV
Controls &
Diagnostics
Magnets, vacuum
Cryo-module
Vacuum system
Laser
e2.5MeV
Gun
SRF cavity
e2.5MeV
1 MW 700 MHz
Klystron
Klystron PS
50 kW 700 MHz
I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004
Beam dump
I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004
Goals for ERLs
e-cooler
prototype
• Generate and accelerate • Generate and accelerate
bright (n < 50 mrad)
bright (n < 50 mrad)
intense (i.e. 150+ mA)
intense (i.e. 150+ mA)
magnetized (i.e. with
electron beam with
angular momentum)
energy ~ 20-40 MeV
electron beam to the
• Decelerated the electron
energy of 54.677 MeV
beam to few MeV and to
• Cool the ion beam(s)
recover its energy back
into the RF field
• Decelerated the electron
beam to few MeV and to • Test the concepts and
recover its energy back
stability criteria for very
into the RF field
high current ERLs
I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004
Photocathode and laser
• Lead – Triveni Rao
The objective: Develop a photocathode
material that has a high quantum
efficiency in the green and long life.
Develop suitable laser technology.
Status: UHV deposition chamber
operational, CsK2Sb cathode depositions
started. Cathode will be provided for
photoinjector in FY05.
I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004
CW - Photoinjector Glidcop, 703.75 MHz
Solenoid
RF input
coupler
LANL and Advanced Energy Systems
New 703 MHz
CW Photoinjector
Under construction
I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004
Superconducting gun
1
2
8
7
AES – BNL – JLAB gun
4
6
5
Preparation Chamber
Beamline
(1) Niobium Cavity
(2) Choke Flange Filter
(3) Cooling Insert
(4) Liquid Nitrogen Tube
3
(5) Ceramic Insulation
(6) Thermal Insulation
(7) 3 Stage Coaxial Filter
(8) Cathode Stem
Possible direction?
Rossendorf like gun with
CsK2Sb or similar cathode
I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004
CsK2Sb Photocathode
UHV photocathode
preparation system
I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004
Q.E. as a function of Cs deposition
20
3
18
2.5
14
2
12
10
1.5
8
1
6
4
0.5
2
0
0
50
100
150
200
250
300
350
time (sec)
I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004
0
400
QE (%)
Current (uA)
16
Current
QE %
High current ERL SRF cavity
See presentation by Ram Calaga in WG
• Lead – Ilan Ben-Zvi
Objective: Develop a cavity for high average
current (about 100 times the JLAB ERL),
with large-charge bunches (difficult HOM
power handling)
Status: Design successfully finished,
contract for manufacturing in place. Cold
test June 2004, cavity delivered for tests in
May 2005.
I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004
HOM calculated By MAFIA.
All HOMs are extremely well damped.
E_2
E_4
E_5
E_6
Ferrite
HOM damper
Cryomodule
E_7
E_8
E_9
E_13
Copper cavity parts
I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004
Low impedance:
6 times smaller than TESLA cavity
I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004
Cavity quality:
• Ep / Ea ~2
• R/Q = 807 
•  = 225 
• Hp/Ea = 5.8 mT/MV/m
Qualities important for ERL service:
• Loss factor 1.2 V/pC (less HOM power)
• BBU threshold about 1.5 to 2 amperes
• Mechanically very stiff cavity, lowest mechanical
resonance over 100 Hz
I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004
Superconducting solenoid
• Lead –Animesh Jain
Objective: Develop a prototype superconducting
solenoid and its measurement system,
demonstrate ability to deliver ultra-high precision
in two 13 m long sections, 1 T superconducting
solenoid.
Status: Solenoid principles established, Prototype
design under way. Correction system under
tests.
I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004
Conceptual Design of Solenoid
Dipole Corrector
Copper Solenoid
20 mT; 1.83 m long
I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004
Simulated Correction
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
B_y Error data;20 harmonics; Lambda=100mm to 2 meters; 6.5m long solenoid; ~6.6m long corrector
2 families; Dipole06a;b; 150mm patterns. 160mm spacing; 80mm offset for second layer; No extra gaps.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1.0E-05
Net Field after
correction from
10-4 initial error
8.0E-06
Residual By (Tesla)
6.0E-06
4.0E-06
2.0E-06
0.0E+00
-2.0E-06
-4.0E-06
-6.0E-06
-8.0E-06
-1.0E-05
-4000
-3000
-2000
-1000
0
1000
2000
Z Position (mm)
I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004
3000
4000
Conclusions
• High energy electron cooling looks
feasible, but requires R&D.
• An aggressive and comprehensive R&D
program is in place.
• We recognize the challenges, but we are
confident that cooling RHIC will work well.
• In about three years we expect to resolve
all outstanding R&D issues.
I. Ben-Zvi, 2nd EIC Workshop, March 15-17, 2004