1. Pre-Linac simulations in G4beamline Alex Bogacz & Yves Roblin
Kevin B. Beard
Muons,Inc.
&
Alex Bogacz & Yves Roblin
Jefferson Lab
LEMC2009 workshop 8-12 Jun 2009

2. pre-accelerator linac - not very relativistic
Morteza Aslaninejad, Cristian Bontoiu
Jürgen Pozimski, Ajit Kurup
Imperial College, London, UK
0.6 GeV/pass
3.6 GeV
0.9 GeV
244 MeV
146 m
79 m
2 GeV/pass
264 m
12.6 GeV
Mm = MeV
Etotal: 244 MeV → 900 MeV
P: MeV/c → 894 MeV/c
KE: MeV → 794 MeV

3. Longitudinal phase-space tracking
IDS
erms
A = (2.5)2 e
normalized emittance: ex/ey
mmrad
4.8 30
longitudinal emittance: el
(el = sDp sz/mmc)
momentum spread: sDp/p
bunch length: sz mm 27
0.07
176
150
0.17
442
ELEGANT (Fieldmap)
OptiM (Matrix)

4. Solenoid Linac ( MeV)
6 short cryos
15 MV/m
8 medium cryos
17 MV/m
11 long cryos
1.1 Tesla solenoid
1.4 Tesla solenoid
2.4 Tesla solenoid
Transverse acceptance (normalized): (2.5)2eN = 30 mm rad
Longitudinal acceptance: (2.5)2 sDpsz/mmc = 150 mm
146
Sat Dec 13 22:36: OptiM - MAIN: - D:\IDS\PreLinac\Sol\Linac_sol.opt 12 5
BETA_X&Y[m]
DISP_X&Y[m]
BETA_X
BETA_Y
DISP_X
DISP_Y

5. Why another simulation?
OptiM – fast, interactive, design, matrix based 0th order design tool, symplectic soft edge solenoids, very good at tuning (free)
GPT – good at tracking ($)
G4beamline – tracking, Geant4 particle decays & interactions, energy depositions, showers, etc., not so good at tuning (free & open source)

6. Solenoid Model (Superfish)
outer coil
shield
inner coil
‘Soft-edge’ Solenoid

7. Two-cell cavity (201 MHz) – COMSOL
Morteza Aslaninejad
Cristian Bontoiu
Jürgen Pozimski

8. Field maps
solenoid Bz
single RF cell Ez
double RF cell Ez

9. g4beamline 2.08 counterwound solenoid RF cell valve assembly
flux return shield
conductors
stainless
pipe
RF cell
Virtual detectors
LEMC2009 workshop 8-12 Jun 2009

10. upper
middle
lower
LEMC2009 workshop 8-12 Jun 2009

11. Simple Phasing via spreadsheet
0o≡on crest
L=2λ c=λf z=cβt
Ez(z,t) ≈ qEzo cos(2πf t + φ) cos(π z/L)
+L/2
ΔE ≈ ∫ Ez(z,z/cβ) dz
-L/2
ΔE ≈ -2qEzo L cos(π/ 2β) cos(φ) β2/(π (1-β2)
ΔE ≈ -2qEzo L cos(π/ 2β) cos(φ) β2/(π (1-β2)
Ti ≈ Ti-1+ (zi - zi-1)/(cβi-1)
LEMC2009 workshop 8-12 Jun 2009
Muons, Inc.
ΔE ≈ ∫ Ez(z,z/cβ) dz
Ez(z,t) ≈ qEzo cos(2πf t + φ) cos(π z/L)
Ti ≈ Ti-1+ (zi - zi-1)/(cβi-1)

12. Linac parameters
Muons, Inc.

13. phases partially adjusted
Longitudinal
phases partially adjusted
phases from spreadsheet
LEMC2009 workshop 8-12 Jun 2009
Muons, Inc.

14. Comparison of GPT, OptiM, g4beamline
KE[MeV]
z[cm]
G4beamline w/adj. φ's
OptiM
G4beamline
w/OptiM's φ's
KE[MeV]
LEMC2009 workshop 8-12 Jun 2009
z[cm]
Muons, Inc.

15. Ez Ez
LEMC2009 workshop 8-12 Jun 2009
Muons, Inc.

16. LEMC2009 workshop 8-12 Jun 2009
Sep 14, 2010
Muons, Inc.

17. Fine tuning is still in progress
Synchrotron motion
~ oncrest Pz
~ 1 synch period
LEMC2009 workshop 8-12 Jun 2009 t t
Muons, Inc.
G4beamline model is working well and in general agreement with other simulations
Essential step toward our long term goal of complete end-to-end simulations
Fine tuning is still in progress
Will soon begin particle interactions with the hardware

18. Transverse motion GPT G4beamline y[m] LEMC2009 workshop 8-12 Jun 2009
z[m]
z[m]
Muons, Inc.

19. G4beamline improvements from this work:
fieldmap timeOffset fixed
(simple bug fix)
pillbox autoTune being added
(tune for max,min ΔE or Δt rather than assume Δv=0)
LEMC2009 workshop 8-12 Jun 2009
Muons, Inc.

20. Linac – near term plans optical rematch of linac to cooling channel
greatly improve RF phasing capability of G4beamline
optical rematch of linac to cooling channel
optimize longitudinal and transverse acceptance
determine energy deposition in components
prepare the transfer line to RLA I

21. LEMC2009 workshop 8-12 Jun 2009
Sep 14, 2010
Muons, Inc.