Upload
arva
View
83
Download
0
Tags:
Embed Size (px)
DESCRIPTION
MEIC Electron Cooling Simulation. He Zhang 03/18/2014, EIC 14 Newport News, VA. 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 - PowerPoint PPT Presentation
Citation preview
MEIC Electron Cooling Simulation
He Zhang03/18/2014, EIC 14 Newport News, VA
He Zhang ---2---
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 discussions
He Zhang ---3---
Introduction• The MEIC conceptual design aims for reaching ultra high luminosity
up to 1034 cm-2s-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
He Zhang ---4---
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-boosterStep 2: Bunched cooling at the ion injection energy (25 GeV) of the
collider ringStep 3: Bunched cooling at the top ion energy (100 GeV) of the
collider ring
MEIC ion complex
Yaroslav DerbenevTalk on Tuesday
He Zhang ---5---
DC and ERL-Circulator Cooler for MEIC
ion bunch
electron bunch
circulator ring
Cooling section
solenoid
Fast kickerFast kicker
SRF Linac dumpinjector
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 conceptERL + 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 DerbenevTalk on Tuesday
He Zhang ---6---
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.
He Zhang ---7---
Simulation ParametersKey parameters for MEIC three-step cooling scheme
Pre-Booster Collider Ring Collider RingProton Energy GeV 3 25 60/100 Proton Number 2.52×1012 1.26×1013 4.16×109/bunchProton Bunch Length cm Coasting Coasting 1
Cooler Type DC ERL circulator ERL circulatorMagnetic Field in Cooler T 1 2 2Cooler Length m 10 2×30 2×30Electron Beam Current A 3 1.5 1.5
Electron Bunch Length cm 1 1
He Zhang ---8---
Step 1: Cooling in Pre-Booster (3 GeV)
IBS ECOOL IBS+ECOOLRH 1/s 0.0009 -0.0073 -0.0064
RV 1/s 0.0002 -0.0072 -0.0070
RL 1/s 0.0003 -0.0128 -0.0125
He Zhang ---9---
Step 2: Cooling in Collider Ring (25 GeV)
IBS ECOOL IBS+ECOOLRH 1/s 0.0005 -0.0169 -0.0164
RV 1/s 3.47×10-5 -0.0118 -0.0118
RL 1/s 0.0009 -0.0242 -0.0233
He Zhang ---10---
Step 3: Cooling in Collider Ring (60 GeV)
IBS no coupling
IBS ECOOL IBS+ECOOL
RH 1/s 0.0214 0.0204 -0.0221 -0.0017
RV 1/s 0.0002 0.0015 -0.0079 -0.0064
RL 1/s 0.0069 0.0069 -0.0086 -0.0016
He Zhang ---11---
Step 3: Cooling in Collider Ring (100 GeV)
IBS no coupling
IBS ECOOL IBS+ECOOL
RH 1/s 0.0156 0.0078 -0.0087 -0.0009
RV 1/s 4.99×10-5 0.0094 -0.0107 -0.0013
RL 1/s 0.0035 0.0035 -0.0043 -0.0007
He Zhang ---12---
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
He Zhang ---13---
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
He Zhang ---14---
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
He Zhang ---15---
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
Cooling at High Energy w/ Existing Technologies
• Only for heavy ions• Bandwidth: 4~9 GHz• Lead ions: 5.1x107 per bunch• Bunch length: 2 cm effective ions in the ring: 1.37x1012 • Cooling time: ~ 14 min
ion bunch
electron bunch
circulator ring
Cooling section
solenoid
Fast kickerFast kicker
SRF Linac dumpinjector
“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 ERL
He Zhang ---17---
With “Weak” Cooling in Collider Ring (25 GeV)
IBS ECOOL IBS+ECOOLRH 1/s 0.0004 -0.0048 -0.0044
RV 1/s 3.47×10-5 -0.0034 -0.0033
RL 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.
He Zhang ---18---
With “Weak” Cooling in Collider Ring (60 GeV)• At 60 GeV, reduce proton charge number to 3×109/bunch to reduce IBS• Luminosity is about 3×1033cm-2s-1
He Zhang ---19---
With “Weak” Cooling in Collider Ring (100 GeV)• At 100 GeV, reduce proton charge number to 3×109/bunch to reduce IBS• Luminosity is about
He Zhang ---20---
Luminosity of Strong Cooling, Weak Cooling and No Cooling in Collider Ring
• 60 GeV • 100 GeV
• Nominal design: 6.5×1033cm-2s-1
• Weak cooling: 3×1033cm-2s-1
• No cooling: above 2×1033cm-2s-1
in two hours.
• Nominal design: 5.4×1033cm-2s-1
• Weak cooling: 1.5×1033cm-2s-1
• No cooling: above 1.6×1033cm-2s-1
in two hours.
He Zhang ---21---
ConclusionsUnder ideal condition
• In Pre-booster, KEp=3GeV, ε reduced from 1.75 μm to 0.8/0.55 μm. (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 1033 cm-2s-1 in two hours
• A weak cooling (state of art) in the collider ring can keep the luminosity above 1033 cm-2s-1
He Zhang ---22---
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.
He Zhang ---23---