View
231
Download
2
Category
Preview:
Citation preview
1
Ionization Cooling – neutrinos, Ionization Cooling – neutrinos, colliders and beta-beamscolliders and beta-beams
David Neuffer
July 2009
2
OutlineOutline
Front End and Cooling – IDS neutrino factory Study 2A – ISS baseline example
•Target-capture, Buncher, Rotator. Cooler Shorter bunch train example(s)
•nB= 10, Better for Collider; as good for ν-Factory
Variation – 88 MHz
Rf cavities in solenoids – major constraint? up to 15MV/m, ~2T Alternatives
•Use lower fields (B, V’), use “magnetic insulation” ASOL lattice, use gas-filled rf cavities
Large Emittance Muon Collider option Low-Energy Cooling discussion
ERIT results Ion cooling for Beta-beams
3
Official IDS layoutOfficial IDS layout
4
Neutrino Factory-IDS
For IDS need baseline for engineering
5
ISS Study 2B baselineISS Study 2B baseline
Base lattice has B=1.75T throughout buncher and rotator rf cavities are pillbox grouped in same-frequency
clusters• 7 to 10 MV/m Buncher; 12.5 Rotator
with 200μ to 395μ Be “windows”,• 750μ windows in “Rotator”
Cooling Lattice is alternating-solenoid with 0.75 half-period 0.5m pillbox rf cavity 1cm LiH absorbers 15.25MV/m cavities
6
IDS - Shorter VersionIDS - Shorter Version
Reduce drift, buncher, rotator to get shorter bunch train:
217m ⇒ 125m 57m drift, 31m buncher, 36m rotator Rf voltages up to 15MV/m (×2/3)
Obtains ~0.26 μ/p24 in ref. acceptance Similar or better than Study 2B
baseline Better for Muon Collider
80+ m bunchtrain reduced to < 50m Δn: 18 -> 10
-30 40m
500MeV/c
7
Shorter Buncher-Rotator settings Shorter Buncher-Rotator settings
Buncher and Rotator have rf within ~2T fields rf cavity/drift spacing same
throughout (0.5m, 0.25) rf gradient goes from 0 to 15
MV/m in buncher cavities Cooling same as baseline
ASOL lattice 1 cm LiH slabs (3.6MeV/cell) ~15MV/m cavities also considered H2 cooling
Simulated in G4Beamline optimized to reduce # of
frequencies Has 20% higher gradient
ASOL lattice
8
Rf in magnetic fields?Rf in magnetic fields?
Baseline has up to 12 MV/m in B=1.75T (in 0.75m cells)
short version has up to 15MV/m in B=2.0T
Experiments have shown reduced gradient with magnetic field
Results show close to needed ? 14MV/m at 0.75T on cavity wall half-full or half-empty ?
Future experiments will explore these limits will not have 200 MHz in constant
magnetic field until summer 2010 Open cell cavities in solenoids?
did not show V’ /B limitation
9
Solutions to possible rf cavity Solutions to possible rf cavity limitationslimitations
For IDS, we need an rf cavity + lattice that can work
Potential strategies: Use lower fields (V’, B) Use Open-cell cavities?
Use non-B = constant lattices• alternating solenoid
Magnetically insulated cavities• Is it really better ???
• Alternating solenoid is similar to magnetically insulated lattice
Shielded rf lattices• low B-field throughout rf -
Rogers Use gas-filled rf cavities
• but electron effects?
10
Lower-field (?) VariantLower-field (?) Variant
Use B=const for drift + buncher Low-gradient rf ( < 6 MV/m) B= 1.5 to 2.0 T ?
Use ASOL for rotator + Cooler (and/or H2 cavities) 12 MV/m rf Rotator 15 MV/m cooler 0.75 half-cells
Simulation: fairly good acceptance Lose some low energy mu’s
• bunch train shortened
~0.25 μ/24p after 60m H2 cooling
~0.19 μ/24p after 60m LiH cooling
11
Change cavity material-PalmerChange cavity material-Palmer
Be windows do not show damage at MTA no breakdown?
Model: Energy deposition by electrons crossing the rf cavity causes reemission on the other side
less energy deposition in Be higher rf gradient threshold
~2× gradient possible with Be cavities ?? calculated in model extrapolation to 200MHz ?
B
electrons
2R
12
Variant: “88” MHz Front end Variant: “88” MHz Front end
Drift ~90m Buncher ~60m
166→100 MHz, 0→6MV/m
Rotator ~58.5m 100→86 MHz, 10.5 MV/m
Cooler ~100m 85.8MHz, 10 MV/m 1.4cm LiH/cell ASOL
10 m ~80 m
FE
Targ et
Solenoid Drift Buncher Rotator Cooler
~60m 60m ~100 m
p
π→μ
13
88 MHz example88 MHz example
Performance seems very good ~0.2 μ/p24
smaller number of bunches > ~80% in best 10 bunches
Gradients used are not huge, but probably a bit larger than practical up to ~10 MV/m ~2T magnetic fields
With 10 MV/m (0.75m cells) probably not free of breakdown problems
redo with realistic gradients 6MV/m ?
14
Plan for IDSPlan for IDS
Need one design likely to work for Vrf/B-field rf studies are likely to be inconclusive
Hold review to endorse a potential design for IDS – likely to be acceptable (Vrf/B-field)
April 2010 ?
Use reviewed design as basis for IDS engineering study
15
Cooling for first muon colliderCooling for first muon collider
Important physics may be obtained at “small” initial luminosity μ+μ- Collider
μ+ + μ- -> Z* , HS L > 1030 cm-2s-1
Start with muons fron neutrino factory front end:
3 × 1013 protons/bunch 1.5× 1011
μ/bunch• ~12 bunches – both
signs! εt,rms, normalized ≈ 0.003m
εL,rms, normalized≈ 0.034m Accelerate and store for
collisions Upgrade to high
luminosity
16
Proton Source: X -> Proton Source: X -> νν-Factory/-Factory/μμ-Collider-Collider
Project X based proton driver
8 GeV SRF linac , 15 Hz 1.2×1014/cycle
H- inject full linac pulse into new “Accumulator” “small” dp/p Large εN6π =120π mm-mrad
Bunch in harmonic 4 adiabatic OK !! (2kV)
Transfer into new “Buncher” 100kV h=4 1250 turns (2ms) short ~1 m bunches !! 3×1013/bunch
• BF = 0.005
• δν = 0.4
8GeV LinacAccumulator
Buncher
p tot
2F N
3r N
2 B
17
Large Emittance Muon ColliderLarge Emittance Muon Collider
Parameter Symbol Value
Proton Beam Power Pp 2.4 MW
Bunch frequency Fp 60 Hz
Protons per bunch Np 3×1013
Proton beam energy Ep 8 GeV
Number of bunches nB 12
+/-/ bunch N 1011
Transverse emittance t,N 0.003m
Collision * * 0.05m
Collision max * 10000m
Beam size at collision x,y 0.013cm
Beam size (arcs) x,y 0.55cm
Beam size IR quad max 5.4cm
Collision Beam Energy E+,E_ 1 TeV (2TeV total)
Storage turns Nt 1000
Luminosity L0 4×1030
Proton Linac 8 GeV
Accumulator,Buncher
Hg target
Linac
RLAs
Collider Ring
Drift, Bunch, Cool200m
Detector
Use only initial “front-end” coolingAccelerate front-end bunch train; collide in ring
18
Must be upgradeable to “high-Must be upgradeable to “high-luminosity”luminosity”
MEMC Upgrades reduce εt to 0.001m
• initial part of HCC 1300MHz rf combine 12 ->
1bunch L -> 3 1032
High luminosity Cool to 0.000025
Parameter Symbol HEMC MEMC LEMC Value
Proton Beam Power Pp 2.4 MW 4MW 4MW
Bunch frequency Fp 60 Hz 60Hz 15Hz
Protons per bunch Np 3×1013 5×1013 4×1013
Proton beam energy Ep 8 GeV 8 GeV 50 GeV
Number of bunches nB 12 1 1
+/-/ bunch N 1011 1.5×1012 2×1012
Transverse emittance t,N 0.003m 0.001m 0.000025
Collision * * 0.06m 0.04 0.01
Beam size at collision x,y 0.013cm 0.0063cm 0.0005cm
Beam size (arcs) x,y 0.55cm 0.32cm 0.05cm
Beam size IR quad max 5.4cm 3.2cm 0.87cm
Collision Energy E+,E_ 1 TeV (2TeV total)
1 TeV 1 TeV
Luminosity turns nt 1000 1000 1000
Luminosity cm-2s-1 L0 4×1030 2.7×1032 1.5×1034
19
Other cooling uses- not just high-energy Other cooling uses- not just high-energy muons!muons!
. Stopping beam (for 2e, etc.) C. Ankenbrandt, C. Yoshikawa
et al., Muons, Inc.
For BCNT neutron source Y. Mori - KURRI
For beta-beam source C. Rubbia et al
…
g
P (MeV/c)
gL
0
-1
(dE/ds)/E= gL(dp/ds)/p
20
Virtual detector
r = 3 m
end of NF/MC drift regionμ± & π± from 100k POT MERIT-like targetry
Revisit Use of NF/MC Front End to Stop Muons with Momentum-dependent HCC
HCC
…
matching (not done)100k Mu-’s w/ Bent Sol Spread at start of HCC.
Mu-’s midway to end of HCC (20,836/100,000)
Mu-’s at end of HCC. Displayed is 5398/100k, but stopping rate is 3519/100k.
170
25
P(MeV/c)
μ−’s stopped
Potential to enhance yield via P vs. y correlation in bent solenoid.
C Yoshikawa
21
FFAG-ERIT neutron source FFAG-ERIT neutron source (Mori, (Mori, KURRI)KURRI)
Ionization cooling of protons/ ions is unattractive because nuclear reaction rate energy-loss cooling rate
But can work if the goal is beam storage to obtain nuclear reactions Absorber is beam target, add rf
ERIT-P-storage ring to obtain neutron beam (Mori-Okabe, FFAG05)
10 MeV protons (β = v/c =0.145) 10Be target for neutrons 5µ Be absorber, wedge (possible) δEp=~36 keV/turn
Ionization cooling effects increase beam lifetime to ~ 1000 turns not actually cooling
22
Observations of “Cooling”-PAC09Observations of “Cooling”-PAC09
ERIT ring has been operated
Beam lifetime longer than without energy-recover rf agrees with ICOOL simulation
Beam blowup is in agreement with simulation multiple scattering heating in
agreement with ICOOL
23
ββ-beam Scenario -beam Scenario (Rubbia et al.)(Rubbia et al.)
β-beam – another e source Produce accelerate, and store unstable
nuclei for -decay Example: 8B8Be + e++ν or 8Li8Be + e-
+ ν*
Source production can use ionization cooling Produce Li and inject at 25 MeV nuclear interaction at gas jet target
produces 8Li or 8B• 7Li + 2H 8Li + n
• 6Li + 3He 8B + p Multiturn storage with ionization
“cooling” maximizes ion production 8Li or 8B is ion source for β-beam
accelerator• C. Rubbia, A. Ferrari, Y. Kadi, V.
Vlachoudis, Nucl. Inst. and Meth. A 568, 475 (2006).
• D. Neuffer, NIM A 583, p.109 (2008)
e
24
ββ-beams example: -beams example: 66LiLi + + 33HeHe 88BB + + n n
Beam: 25MeV 6Li+++ PLi =529.9 MeV/c Bρ = 0.59 T-m; v/c=0.094 Jz,0=-1.6
Absorber:3He -gas jet ? dE/ds = 110.6 MeV/cm ,
If gx,y,z = 0.13 (Σg = 0.4), β┴ =0.3m at absorber
Must mix both x and y with z εN,eq= ~ 0.000046 m-rad,
σx,rms= ~2 cm at β┴ =1m
σE,eq is ~ 0.4 MeV
Could use 3He as beam 6Li target ( foil or liquid)
,
2 2
, 22
z a
sN eq dE
x p R ds
z E
J am c L
22 2 4 3
e p β2E,eq 2
L
(m c )(am c )β γσ = 1-
2J ln[]
25
ββ-beams alternate: -beams alternate: 66LiLi++33HeHe 88BB + n + n
Beam: 12.5MeV 3He++ PLi =264 MeV/c Bρ = 0.44 T-m; v/c=0.094
Absorber: 6Li - foil or liquid jet dE/ds = 170 MeV/cm, LR=155cm
•at (ρLi-6= 0.46 gm/cm3)
Space charge 2 smaller If gx = 0.123 (Σg
= 0.37), β┴ =0.3m at absorber εN,eq= ~ 0.000133m-rad
σx,rms= 2.0 cm at β┴ =0.3m,
σx,rms= 5.3 cm at β┴ =2.0m
σE,eq is ~ 0.3 MeV ln[ ]=5.34
,
2 2
, 22
z a
sN eq dE
x p R ds
z E
g am c L
22 2 4 3
e p β2E,eq 2
L
(m c )(am c )β γσ = 1-
2g ln[]
26
Cooling Ring for Beta-BeamsCooling Ring for Beta-Beams
Assume He-3 beam Bρ=0.44T-m, β=0.094
Cooling ring parameters C =12m (?)
Absorber 0.01 cm Li wedge βt = ~0.3m, η= ~0.3m
rf needed 2 MV rf
Injection charge strip He+ to He++
(?) Extraction
kicker after wedge NuFACT09
miniworkshop: July27-29
Solenoid1.38T-m
Cooling wedgeβ=0.3m, η=0.3m
rf
27
SummarySummary
Rf in magnetic field problem must be addressed Need rf configuration that can work with high
confidence
Need to establish scenario Use as basis for engineering study
Further meetings/studies NuFACT 2009 miniworkshop at Fermilab (July 27-28) front end and beta-beam cooling
•9-11am WH3NE
•1:30-4PM Front End Review
•April 2010?
28
Future Funding … ??Future Funding … ??
Recommended