1

Front EndFront EndCapture/Phase RotationCapture/Phase Rotation

& Cooling Studies & Cooling Studies

David NeufferCary Yoshikawa

December 2008

2

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

3

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 ??

4

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)

5

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

6

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

7

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

8

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

9

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)

10

Simulations (NSimulations (NBB=10)=10)

-30m 30m

500 MeV/c

0

Drift andBunch

s = 89ms = 1m

Rotate

s = 125m s = 219m

Cool

11

Front end simulationsFront end simulations

Initial beam is 8GeV protons, 1ns bunch length

12

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

13

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

14

G4Beamline ICOOLP

i+/M

u+

Pi-

/Mu

-Rotator End

15

G4Beamline ICOOLP

i+/M

u+

Pi-

/Mu

-Cool End

16

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)

17

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

18

Accepted Longitudinal distrosAccepted Longitudinal distros

1m 135m

135m 196m

196m

-30m 40m

600 MeV/c

600 MeV/c

0 MeV/c

0 MeV/c

19

““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

20

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

21

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)

22

2T -> ASOL2T -> ASOL

23

ASOL-1.33T ASOL-1.33T

56m62m

133m 193m

24

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

25

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

26

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

27

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

28

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

29

Any Questions?Any Questions?

30

Project X Status Project X Status

31

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

Form bunches first

Φ-E rotate bunches