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Bunched-Beam Phase Rotation for a Neutrino Factory. David Neuffer Fermilab. 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

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Presentation Transcript
outline
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
Neutrino Factory Baseline Design
  • Feasible, but expensive
  • Find ways to reduce costs …
study 2 system
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 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
Adiabatic buncher + Vernier  Rotation
  • Drift (90m)
    •  decay;

beam develops  correlation

  • Buncher(60m)(~333200MHz)
    • 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
Longitudinal Motion (1-D simulations)

Drift

Bunch

E rotate

Cool

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

buncher overview
Buncher overview
  • Adiabatic buncher
  • Set T0, :
    • 125 MeV/c, 0.01
  • In buncher:
  • Match torf=1.5m at end:
  • zero-phase with 1/ at integer intervals of  :
  • Adiabatically increase rf gradient:

rf : 0.901.5m

vernier rotation
“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 : 1.4851.517m in rotation;

rf = ct/10 at end

(rf  1.532m)

Nonlinearities cancel:

T(1/) ; Sin()

1 d 3 d simulations a van ginneken
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:
      • 384233 MHz
      • Linear ramp in voltage 0 to 6.5MV/m, 60m long
    •  Rotator:
      • “vernier” frequency (20 + ) wavelengths between reference bunches (234220 MHz), 10MV/m,   0.16
      • 30m long
      • Obtains ~0.4 /p
bunching and rotation
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
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
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

compare with study ii capture cooling
Compare with Study II (Capture + Cooling)

x: –20 to 100m; y: 0 to 400 MeV

caveats not properly matched
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
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
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
slide19

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
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
Hardware/Cost For Buncher/Rotator
  • Rf requirements:
    • Buncher: ~300~210 MHz; 0.14.8MV/m (60m)

(~10 frequencies; ~10MHz intervals)

    •  Rotator: ~210200 MHz; 10MV/m (~10m)
  • 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
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
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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