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Bunched-Beam Phase Rotation for a Neutrino Factory PowerPoint Presentation

Bunched-Beam Phase Rotation for a Neutrino Factory

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Presentation Transcript

Outline

- Introduction
- Study 2 scenario
- Induction linac phase rotation + 200 MHz buncher

- “High-frequency” Buncher and Rotation
- Concept
- 1-D simulation
- 3-D simulations – Simucool, ICOOL
- Mismatch into cooling channel

- Toward “realistic” implementation
- Elvira, Keuss Geant4 simulations
- Cost guesstimates …

- Future Studies
- Variations
- Matching, Optimization Study 3

Neutrino Factory Baseline Design

- Feasible, but expensive
- Find ways to reduce costs …

Study 2 system

- Drift to develop Energy- phase correlation
- Accelerate tail; decelerate head of beam (280m induction linacs (!))
- Bunch at 200 MHz
- Inject into 200 MHz cooling system

Study 2 Scenario – induction linacs

- Study II scenario uses
- ~ 280m of induction
- linacs to capture muons.
- Cost is very high
- Technology is difficult

Adiabatic buncher + Vernier Rotation

- Drift (90m)
- decay;
beam develops correlation

- decay;
- Buncher(60m)(~333200MHz)
- Forms beam into string of bunches

- Rotation(~10m)(~200MHz)
- Lines bunches into equal energies

- Cooler(~100m long)(~200 MHz)
- fixed frequency transverse cooling system

Replaces Induction Linacs with medium-frequency rf (~200MHz) !

Longitudinal Motion (1-D simulations)

Drift

Bunch

E rotate

Cool

System would capture both signs (+, -) !!

Buncher overview

- Adiabatic buncher
- Set T0, :
- 125 MeV/c, 0.01

- In buncher:
- Match torf=1.5m at end:
- zero-phase with 1/ at integer intervals of :
- Adiabatically increase rf gradient:

rf : 0.901.5m

“Vernier” Rotation

- At end of bunch, choose:
- Fixed-energy particle T0
- Second reference bunch TN
- Vernier offset

- Example:
- T0 = 125 MeV
- Choose N= 10, =0.1
- T10 starts at 77.28 MeV

- Along rotator, keep reference particles at (N + ) rf spacing
- 10 = 36° at =0.1
- Bunch centroids change:

- Use Erf = 10MV/m; LRt=8.74m
- High gradient not needed …
- Bunches rotate to ~equal energies.

rf : 1.4851.517m in rotation;

rf = ct/10 at end

(rf 1.532m)

Nonlinearities cancel:

T(1/) ; Sin()

1-D 3-D Simulations (A. van Ginneken)

- Initial examples are 1-D
- Add transverse focusing (1.25T solenoid); initial beam from MARS simulations (Mokhov) of target production
- Use Large statistics tracking code (SIMUCOOL, A. Van Ginneken)
Reoptimize all parameters–

- Drift to 76m,
- Buncher parameters:
- 384233 MHz
- Linear ramp in voltage 0 to 6.5MV/m, 60m long

- Rotator:
- “vernier” frequency (20 + ) wavelengths between reference bunches (234220 MHz), 10MV/m, 0.16
- 30m long
- Obtains ~0.4 /p

Bunching and Rotation

Beam after ~200MHz rf rotation;

Beam is formed into

string of equal-energy bunches;

matched to cooling rf acceptance

Beam after drift plus

adiabatic buncher –

Beam is formed into

string of ~ 200MHz bunches

System would capture both signs (+, -) !!

Next step: match into cooling channel !

- Need to design a new cooling channel, matched to bunched/rotated beam
- Do not (yet) have redesigned/matched cooling channel
- Use (for initial tries):
- ICOOL beam from end of AVG simulations
- Study 2 cooling channel
- Direct transfer of beam (no matching section)

Results (~ICOOL)

- In first ~10m, 40% of ’s from buncher are lost,
0.020m 0.012m

- Remaining ’s continue down channel and are cooled and scraped, ~0.0022m, similar to Study 2 simulation.
- Best energy, phase gives ~0.22 ’s /24 GeV p
- Study 2 baseline ICOOL results is ~0.23 ’s/p

GeV

m

ICOOL simulation –Buncher, , Cool

Compare with Study II (Capture + Cooling)

x: –20 to 100m; y: 0 to 400 MeV

Caveats: Not properly matched

- This is not the way to design a neutrino factory
- Not properly matched in phase space
- Cooling channel acceptance is too small (add precooler ?)
- Correlation factors “wrong”
- “Cooling” channel collimates as much as it cools …

To do

- Move to more realistic models
- Continuous changes in rf frequencies to stepped changes …
- 3-D fields (not solenoid + sinusoidal rf)
- Match into realistic cooling channels …
- Estimate/Optimize Cost/performance

GEANT4 simulations (D. Elvira)

- Fully “realistic” transverse and longitudinal fields
- Magnetic fields formed by current coils
- Rf fields from pillbox cavities (within solenoidal coils)

- Studied varying number of different rf cavities in Buncher
- (60 (1/m) to 20 to 10) … 20 was “better”, 10 only a bit worse

- Simulations of -δE rotation
- Will (?) extend simulations + optimization through cooling channel

10-frequencyBuncher

Only 10 frequencies

and voltages.

(10 equidistant

linacs made of 6 cells)

62.2% of the particles survive at the end of the buncher.

GEANT4 Phase Rotation (D. Elvira, N. Keuss)

Phase rotation successful

Agrees with simplified models/simulations

NOT optimized; Need to continue with simulation into cooling channel

Hardware/Cost For Buncher/Rotator

- Rf requirements:
- Buncher: ~300~210 MHz; 0.14.8MV/m (60m)
(~10 frequencies; ~10MHz intervals)

- Rotator: ~210200 MHz; 10MV/m (~10m)

- Buncher: ~300~210 MHz; 0.14.8MV/m (60m)
- Transverse focussing
- B=1.25T solenoidal focusing;R=0.30m transport

- System Replaces Study 2:
(Decay(20m, 5M$); Induction Linacs(350m, 320M$); Buncher(50m,70M$))

- with:
- Drift (100m); Buncher (60m);Rf Rotator (10m)
- (Rf =30M$ (Moretti); magnets =40M$(M. Green);conv. fac.,misc.20M$)
(400M$ ?? 100M$ )

- needs more R&D …

Variations/ Optimizations …

- Many possible variations and optimizations
- But possible variations will be reduced after design/construction

- Shorter bunch trains ?? For ring Coolers ??
- Can do this with shorter buncher/rotator
- ( with same total rf voltage …)

- Other frequencies ??
- 200 MHz(FNAL) 88 MHz ?? (CERN) ??? (JNF)

- Cost/performance optima for neutrino factory (Study 3?)
- Collider ??both signs (+, -) !
- Graduate students (MSU) (Alexiy Poklonskiy, Pavel Snopok) will study these variations; optimizations;
- First task would be putting buncher into MSU code COSY

Summary

- High-frequency Buncher and E Rotator simpler and cheaper than induction linac system
- Performance as good (or almost …) as study 2,
But

- System will capture both signs (+, -) !
(Twice as good ??)

- Method should (?) be baseline capture and phase-energy rotation for anyneutrino factory …
To do:

- Complete simulations with matched cooling channel!
- Optimizations, Scenario reoptimization

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