Front End Capture/Phase Rotation & Cooling Studies

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1 Front End Front End Capture/Phase Rotation Capture/Phase Rotation & Cooling Studies & Cooling Studies David Neuffer Cary Yoshikawa December 2008

description

Front End Capture/Phase Rotation & Cooling Studies. David Neuffer Cary Yoshikawa December 2008. 0utline. Introduction ν -Factory Front end Capture and Φ -E rotation High Frequency buncher/rotation Study 2B ν -Factory Shorter version ν -Factory → μ + - μ - Collider Discussion. - PowerPoint PPT Presentation

Transcript of Front End Capture/Phase Rotation & Cooling Studies

Page 1: Front End Capture/Phase Rotation & Cooling Studies

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Front EndFront EndCapture/Phase RotationCapture/Phase Rotation

& Cooling Studies & Cooling Studies

David NeufferCary Yoshikawa

December 2008

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0utline0utline

Introduction ν-Factory Front end

Capture and Φ-E rotation High Frequency

buncher/rotation •Study 2B ν-Factory

Shorter version ν-Factory→μ+-μ- Collider

Discussion

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Variations tried …Variations tried …

Study 2A – ISS baseline Shorter bunch train example

nB= 10

Better for Collider; as good for ν-Factory ICOOL/G4Beamline simulations Study of “accepted” particles

Rf cavities in solenoids? Use “magnetic insulation” ASOL lattice Not too bad Variations Higher energy capture ??

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Study2B June 2004 scenario (ISS)Study2B June 2004 scenario (ISS)

Drift –110.7m Bunch -51m

(1/) =0.008 12 rf freq., 110MV 330 MHz 230MHz

-E Rotate – 54m – (416MV total) 15 rf freq. 230 202 MHz P1=280 , P2=154 NV = 18.032

Match and cool (80m) 0.75 m cells, 0.02m LiH

Captures both μ+ and μ-

~0.2 μ/(24 GeV p)

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Study 2B ICOOL simulation (NStudy 2B ICOOL simulation (NBB=18)=18)

s = 1m s=109m

s=166m s= 216m

-40 60

500MeV/c

0

Drift

Bunch

Rotate

500MeV/c

0

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Features/Flaws of Study 2B Front EndFeatures/Flaws of Study 2B Front End

Fairly long system ~300m long (217 in B/R) Produces long trains of ~200 MHz bunches

~80m long (~50 bunches) Transverse cooling is ~2½ in x and y, no longitudinal

cooling Initial Cooling is relatively weak ? -

Requires rf within magnetic fields in current lattice, rf design; 12 MV/m at B = ~2T, 200MHz MTA/MICE experiments to determine if practical

For Collider (Palmer)

Select peak 21 bunches Recombine after cooling ~1/2 lost

-40 60m

500 MeV/c

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Shorter Bunch train example Shorter Bunch train example

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 Slightly better ?

• ~0.24 μ/p for Study 2B baseline

80+ m bunchtrain reduced to < 50m Δn: 18 -> 10

-30 40m

500MeV/c

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Further iteration/optimizationFurther iteration/optimization

Match to 201.25 MHz cooling channel

Reoptimize phase, frequency f = 201.25 MHz, φ = 30º,

Obtain shorter bunch train

Choose ~best 12 bunches ~ 21 bunch train for Collider

at NB= 18 case

~12 bunches (~18m) ~0.2 μ/pref in best 12 bunches Densest bunches are ~twice

as dense as NB = 18 case0

20

40

60

80

100

120

1 6 11 16 21 26 31 36

Series1

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Details of ICOOL model (NDetails of ICOOL model (NBB=10)=10)

Drift– 56.4m B=2T

Bunch- 31.5m Pref,1=280MeV/c, Pref,2 =154 MeV/c, nrf = 10

Vrf 0 to 15MV/m (0.5m rf, 0.25m drift) cells

360 MHz 240MHz

-E Rotate – 36m – Vrf = 15MV/m (0.5m rf, 0.25m drift) cells

NV = 10.07 (240 -> 201.5 MHz)

Match and cool (80m) Old ICOOL transverse match to ASOL (should redo)

Pref= 220MeV/c, frf = 201.25 MHz

• 0.75 m cells, 0.02m LiH, 0.5m rf, 16.00MV/m, φrf =30°

Better cooling possible (H2, stronger focussing)

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Simulations (NSimulations (NBB=10)=10)

-30m 30m

500 MeV/c

0

Drift andBunch

s = 89ms = 1m

Rotate

s = 125m s = 219m

Cool

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Front end simulationsFront end simulations

Initial beam is 8GeV protons, 1ns bunch length

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Comparisons of ICOOL and G4BLComparisons of ICOOL and G4BL

Simulations of front end and cooling agree ICOOL and G4Beamline results can be matched

Buncher – rotator – cooler sequence can be developed in both codes

Method Captures both μ+ and μ-

But some differences dE/dx is larger in ICOOL Phasing of rf cavities uses different model

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12.9 m 43.5 m 31.5 m 36 m

drift buncher rotatorcapture

MC Front End Layout in G4beamline

“Cool and Match” 3 m (4x75 cm cells) “Cool” 90 m of 75 cm cells

Rotator 36 m long

75 cm cell 1 cm LiH

23 cm vacuum

50 cm 201.25 MHz

RF cavity

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G4Beamline ICOOLP

i+/M

u+

Pi-

/Mu

-Rotator End

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G4Beamline ICOOLP

i+/M

u+

Pi-

/Mu

-Cool End

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Reduce number of independent Reduce number of independent frequenciesfrequencies

Initial example had different

rf frequency for each cavity Buncher- 42 cavities -31.5m

• 360to 240 MHz Rotator- 48 cavities -36m

• 240 to 202 MHz

Reduce # by 1/3 14 in buncher; 16 in rotator Nearly as good capture

(<5%less) Similar to study 2B

discreteness Reduce by 1/6

7 in buncher, 8 in rotator Significantly worse (~20%)

Acceptance of Mu+'s Within Atrans<0.030 m-rad & Along<0.15 m (sigma6.0, To=475.5ns, phase=25.8deg)

0

1000

2000

3000

4000

5000

6000

0 20 40 60 80 100 120 140 160 180 200 220

z (m)

Nu

mb

er

of

Mu

+'s

pe

r 1

00

k P

OT

Benchmark

Grp3RF

Grp6RF

Grp3&6RF

Grp6&3RF

Longitudinal Emittance in Study 2A-like Front End (sigma6.0, phase=25.8deg, To=475.5ns)

0.05

0.07

0.09

0.11

0.13

0.15

0.17

0.19

0.21

0.23

0.25

0 20 40 60 80 100 120 140 160 180 200 220

z (m)

Em

itta

nc

e (

m-r

ad

)

a: Tapered Solenoid

b: Drift

c: Buncher

d: Rotator

e: Match & Cool (4m)

f: Cooler (opposing solenoids)

ba c d e f

(a)

(b)

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Accepted particlesAccepted particles

Accepted particles fit final beam cuts: AX + Ay < 0.03m

AL < 0.2m

Initial beam has momenta from ~75 to ~600 MeV/c Final beam is ~200 to

300 MeV/c

Transverse emittance is cooled from ~0.014 to ~0.0036

600 MeV/c

600MeV/c

0 MeV/c

0 MeV/c

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Accepted Longitudinal distrosAccepted Longitudinal distros

1m 135m

135m 196m

196m

-30m 40m

600 MeV/c

600 MeV/c

0 MeV/c

0 MeV/c

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““Accepted” Beam propertiesAccepted” Beam properties

For study 2A acceptance means several cuts: AX + Ay < 0.03m

AL < 0.2m

For beam within acceptances, εt, N,rms = 0.0036m (from

~0.007) εL, N,rms = ~0.04m (from

~0.09)

Emittances are much smaller than the full-beam emittances … xrms = 6cm (all-beam)

xrms = 3.6cm (accepted-beam)-30cm +30cm

-30cm

+30cm

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Variations - focusing Variations - focusing

Buncher and Rotator have rf within 2T fields Field too strong for rf field ?? Axial field within “pill-box”

cavities

Solutions ?? Open-cell cavities ?? “magnetically insulated”

cavities• Alternating Solenoid lattice is

approximately magnetically insulated

• Use ASOL throughout buncher/rotator/cooler

Use gas-filled rf cavitiesASOL lattice

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Use ASOL lattice rather than 2TUse ASOL lattice rather than 2T

Study 2A ASOL Bmax= 2.8T, β*=0.7m,

Pmin= 81MeV/c 2T for initial drift Low energy beam is lost

• (P < 100MeV/c)

• Bunch train is truncated OK for collider

Also tried weaker focusing ASOL Bmax= 1.83T, β*=1.1m,

Pmax = 54 MeV/c 1.33 T for initial drift Match scaled from 2A match

+ -

B(z)

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2T -> ASOL2T -> ASOL

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ASOL-1.33T ASOL-1.33T

56m62m

133m 193m

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First ASOL results First ASOL results

Simulation results 2.8T ASOL 0.18 μ/24 GeV p 0.059 μ/8 GeV p Cools to 0.0075m

1.8T ASOL 0.198 μ/24 GeV p 0.064 μ/8 GeV p ~10% more than stronger

focussing Cools to 0.0085m

Baseline (2T -> ASOL) had ~0.25 μ/24 GeV p ~0.08 μ/8 GeV p

Weaker-focusing ASOL has ~10% better acceptance than 2.8T lattice Longer bunch train

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Variant-capture at 0.28 GeV/cVariant-capture at 0.28 GeV/c

0.0

1.0GeV/c

1.0GeV/c

0.0

2T → 2.8T ASOL

-30m +40m -30m +40m

1.0GeV/c

s=59m s=66m

s=126ms=200m

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Capture at 280 MeV/cCapture at 280 MeV/c

Captures more muons than 220 MeV/c For 2.T -> 2.8T lattice But in larger phase space area Less cooling for given dE/ds Δs

Better for collider Shorter, more dense bunch train If followed by longitudinal cooling

220 MeV/c 280 MeV/c

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Higher-Energy Simulation resultsHigher-Energy Simulation results

Higher energy capture improves capture for high-field lattice Cooling is slower

Not as good for low-field lattice Weaker focusing reduces

cooling

For High field lattice: 2.8T ASOL

8GeV beam 0.065 μ/p in εt <0.03, εL <0.2

0.093 μ/p in εt <0.045, εL <0.3

24 GeV beam 0.19 μ/p in εt <0.03, εL <0.2

0.26 μ/p in εt <0.045, εL <0.3

For Low-field lattice• 1.8T ASOL

8GeV beam

• 0.053 μ/p in εt <0.03, εL <0.2

• 0.083 μ/p in εt <0.045, εL <0.3

• cools only to ~0.010m

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DiscussionDiscussion

High frequency phase-energy rotation + cooling has been explored

Shorter system better for Collider Shorter bunch train; denser bunches

“magnetic insulated” lattice could be used rather than B = 2 or 1.75 T lattice Slightly worse performance (?)

•~10 to 20% worse for neutrino factory Ok for Collider

•Particles lost are at end of bunch train

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Any Questions?Any Questions?

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Project X Status Project X Status

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High-frequency Buncher and High-frequency Buncher and φφ-E -E RotatorRotator

Form bunches first

Φ-E rotate bunches