He Zhang 03182014 EIC 14 Newport News VA H e Zhang 2 Outline Introduction MEIC Multiphased Cooling Scheme MEIC Cooling Simulation Studies Case 1 Nominal Design ThreeStage Cooling ID: 716431
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Slide1
MEIC Electron Cooling Simulation
He Zhang
03/18/2014, EIC 14
Newport News, VASlide2
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Outline
Introduction
MEIC Multi-phased Cooling Scheme
MEIC Cooling Simulation Studies
Case 1: Nominal Design (Three-Stage Cooling)
Case 2: No Electron Cooling in the Collider Ring
Case 3: With “Weak cooling” in the collider ring
Conclusion and discussionsSlide3
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Introduction
The MEIC
conceptual design aims for reaching ultra high luminosity up to 10
34
cm
-2
s
-1
per interaction point
The MEIC luminosity concept is based on high repetition rate crab- crossing colliding beams.
This design concept relies on strong cooling of protons & ions
Achieving small transverse
emittance
(small spot size at IP)
Achieving short
bunch (with strong SRF)
Enabling
ultra strong final focusing
(low
β
*) and
crab crossing
Suppressing
IBS, expanding high luminosity
lifetime
MEIC
design adopts
traditional electron
cooling
MEIC design adopts a multi-phase cooling scheme for high cooling efficiency
We use computer simulations to validity the cooling design concept and beam parameters Slide4
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MEIC Three-Step Cooling Scheme
Multi-phased scheme takes advantages of high
electron cooling efficiency
at low energy
and/or
small 6D
emittance
Step 1: Low energy DC cooling at the pre-booster
Step 2: Bunched cooling at the ion injection energy (25
GeV
) of the collider ring
Step 3: Bunched cooling at the top ion energy (100 GeV) of the collider ring
MEIC ion complex
Yaroslav
Derbenev
Talk on Tuesday Slide5
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DC and ERL-Circulator Cooler for MEIC
ion bunch
electron bunch
circulator ring
Cooling section
solenoid
Fast kicker
Fast kicker
SRF Linac
dump
injector
MEIC needs two electron coolers
DC
cooler
(
within state-of-art
,
a 2 MeV cooler is in commissioning at COSY
)
ERL circulator cooler need significant R&D
High energy cooler
–
beyond state-of-the-art – there are significant challenges
Cooling by a bunched electron beam
Making and transport of high current
/
intensity magnetized electron beam
Present design concept
ERL + circulator ring
To meet following challenges
High RF power (up to 81 MW)
High current ERL (up to 1.5 A)
High current source (short lifetime)
Yaroslav
Derbenev
Talk on Tuesday Slide6
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MEIC Cooling Simulation
Assumptions for simulation
Ion beam has Gaussian distribution.
Electron beam is
magnetized.
Electron beam has uniform distribution in the DC cooler (pre-booster) and Gaussian distribution in the ERL circulator cooler (Collider ring).
The shape and distribution of electron beam does NOT change during cooling.
Misalignment is not considered.
Cooler is modeled as thin lens.
BETACOOL is used for the simulation. Slide7
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Simulation Parameters
Key parameters for MEIC three-step cooling scheme
Pre-Booster
Collider Ring
Collider Ring
Proton Energy
GeV
3
25
60/100
Proton
Number
2.52×10
12
1.26×10
13
4.16×10
9
/bunch
Proton
Bunch Length
cm
Coasting
Coasting
1
Cooler
Type
DC
ERL circulator
ERL circulator
Magnetic Field
in Cooler
T
1
2
2
Cooler Length
m
10
2×302×30Electron Beam Current
A
31.51.5
Electron Bunch Lengthcm1
1Slide8
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Step 1: Cooling in Pre-Booster (3
GeV
)
IBS
ECOOL
IBS+ECOOL
R
H
1/s
0.0009
-0.0073
-0.0064
R
V
1/s
0.0002
-0.0072
-0.0070
R
L
1/s
0.0003
-0.0128
-0.0125Slide9
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Step 2: Cooling in Collider Ring (25
GeV
)
IBS
ECOOL
IBS+ECOOL
R
H
1/s
0.0005
-0.0169
-0.0164
R
V
1/s
3.47×10
-5
-0.0118
-0.0118
R
L
1/s
0.0009
-0.0242
-0.0233Slide10
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Step 3: Cooling
in Collider Ring
(60
GeV
)
IBS
no coupling
IBS
ECOOL
IBS+ECOOL
R
H
1/s
0.0214
0.0204
-0.0221
-0.0017
R
V
1/s
0.0002
0.0015
-0.0079
-0.0064
R
L
1/s
0.0069
0.0069
-0.0086
-0.0016Slide11
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Step 3: Cooling
in Collider Ring
(
100
GeV
)
IBS
no coupling
IBS
ECOOL
IBS+ECOOL
R
H
1/s
0.0156
0.0078
-0.0087
-0.0009
R
V
1/s
4.99×10
-5
0.0094
-0.0107
-0.0013
R
L
1/s
0.0035
0.0035
-0.0043
-0.0007Slide12
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No Cooling in The Collider Ring:
Emittance
Growth and Luminosity Decay Due to IBS
The DC cooling in pre-booster (3
GeV
) provides an initial
emittance
reduction to 0.8 and 0.55 mm
mrad
Slide13
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No Cooling in The Collider Ring:
Emittance
Growth and Luminosity Decay Due to IBS
The DC cooling in pre-booster (3
GeV
) provides an initial
emittance
reduction to 0.8 and 0.55 mm
mrad
Slide14
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No Cooling in The Collider Ring:
Emittance
Growth and Luminosity Decay Due to IBS
The DC cooling in pre-booster (3
GeV
) provides an initial
emittance
reduction to 0.8 and 0.55 mm
mrad
Slide15
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No Cooling in The Collider Ring:
Emittance
Growth and Luminosity Decay Due to IBS
The DC cooling in pre-booster (3
GeV
) provides an initial
emittance
reduction to 0.8 and 0.55 mm
mrad
Slide16
Cooling at High Energy w/ Existing Technologies
Only for
heavy ions
Bandwidth: 4~9 GHz
Lead ions: 5.1x107 per bunchBunch length: 2 cm effective ions in the ring: 1.37x1012 Cooling time: ~ 14 min
ion bunch
electron bunch
circulator ring
Cooling section
solenoid
Fast kicker
Fast kicker
SRF Linac
dump
injector
“Weak”
ERL Cooler
Bunched Stochastic Cooling
RHIC
No circulating ring (no fast kicker)
Electron current:
~
100
mA
Electron bunch charge:
0.133
nC
Electron beam power: 2.75 to 5.5 MW
Needs ERLSlide17
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With “Weak” Cooling in Collider Ring (25
GeV
)
IBS
ECOOL
IBS+ECOOL
R
H
1/s
0.0004
-0.0048
-0.0044
R
V
1/s3.47×10
-5
-0.0034
-0.0033
R
L
1/s
0.0009
-0.0069
-0.0060
At 25
GeV
, a “weak” cooling by 330 mA electron beam is strong enough to cool the coasting proton beam.Slide18
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With “Weak” Cooling in Collider Ring
(60
GeV
)
At 60
GeV
, reduce proton charge number to 3×10
9
/bunch to reduce IBS
Luminosity is about 3×10
33
cm
-2
s
-1Slide19
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With “Weak” Cooling in Collider Ring
(100
GeV
)
At 100
GeV
,
reduce proton charge number to 3×10
9
/bunch to reduce
IBS
Luminosity is aboutSlide20
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Luminosity of Strong
C
ooling, Weak Cooling and No
C
ooling in Collider Ring
60
GeV
100
GeV
Nominal design: 6.5
×10
33
cm-2
s-1Weak cooling: 3
×10
33
cm
-2
s
-1
No cooling: above 2
×10
33
cm
-2
s
-1
in two hours.
Nominal design: 5.4
×10
33
cm-2s
-1Weak cooling: 1.5
×1033cm
-2s-1
No cooling: above 1.6
×10
33cm-2s-1 in two hours.Slide21
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Conclusions
Under ideal condition
In Pre-booster,
KE
p
=3GeV,
ε
reduced from 1.75
μ
m to 0.8/0.55
μ
m. (Similar with the DC cooler in COSY)
In collider ring, KEp
=25GeV, ERL circulator cooler, ε reduced to 0.3/0.25 μm.In collider ring, KEp=60~100GeV, ERL circulator cooler, maintain or further reduce
ε.Design
parameters of MEIC cooling system is
achievable
.
Even without the cooling in the collider ring, the luminosity is above 10
33
cm
-2
s
-1
in two hours
A weak cooling (state of art) in the collider ring can keep the luminosity
above 10
33
cm
-2
s-1
Slide22
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Future Works
Gaussian distribution of the ion beam is assumed during the cooling process, which is not necessarily true.
Analytical formulas are used to calculate the friction force, and their accuracy in MEIC parameter range needs to be checked.
How electron bunch distribution
changes during the cooling process
and the effects on cooling due to the changes need to be studied, since they are repeatedly used.
More accurate models may need to be developed and applied.Slide23
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