1. Tracking and particle-matter interaction studies in the beta-beam decay ring
E.Wildner, A. Fabich (CERN)
Common EURISOL DS - EURONS Town Meeting Helsinki, Finland, September 2007

2. Beta Beam - Loss Deposition, EURONS/EURISOL, E.Wildner
EURISOL Scenario
Aim: production of (anti-)neutrino beams from the beta decay of radio-active ions circulating in a storage ring
Similar concept to the neutrino factory, but parent particle is a beta-active isotope instead of a muon.
Accelerate parent ion to relativistic gmax
Boosted neutrino energy spectrum: En2gQ
Forward focusing of neutrinos: 1/g
EURISOL scenario
Ion choice: 6He and 18Ne
Based on existing technology and machines
Study of a beta-beam implementation at CERN
Once we have thoroughly studied the EURISOL scenario, we can “easily” extrapolate to other cases. EURISOL study could serve as a reference.
Neutrino detector
Ions move almost at the speed of light
EURISOL scenario
Beta Beam - Loss Deposition, EURONS/EURISOL, E.Wildner

3. Possible Beta Beam Complex
High-energy part
Low-energy part
Ion production
Acceleration
Neutrino source
Beam to experiment
Proton Driver SPL
Acceleration to final energy
PS & SPS
Ion production ISOL target & Ion source
Decay ring
Br = 1500 Tm B = ~6 T C = ~6900 m Lss= ~2500 m
6He: g = Ne: g = 100
SPS
Neutrino Source
Decay Ring
Existing!!!
Beam preparation ECR pulsed
Ion acceleration Linac, 0.4 GeV
93 GeV PS
Acceleration to medium energy RCS, 1.5 GeV .
8.7 GeV
Detector in the Frejus tunnel
Beta Beam - Loss Deposition, EURONS/EURISOL, E.Wildner 3 3

4. Beta-beam tasks (Eurisol Design Study)
From ”Overview” by M. Benedikt, Beta Beam Task Meeting in May 2007
Beta Beam - Loss Deposition, EURONS/EURISOL, E.Wildner 4 4

5. Beta Beam - Loss Deposition, EURONS/EURISOL, E.Wildner
Particle Turnover
~1 MJ beam energy/cycle injected
 equivalent ion number to be removed
~25 W/m average
Momentum collimation: ~5*1012 6He ions to be collimated per cycle
Decay: ~5*1012 6Li ions to be removed per cycle per meter
p-collimation
merging
decay losses
injection
Straight section
Arc
Momentum
collimation
Beta Beam - Loss Deposition, EURONS/EURISOL, E.Wildner

6. Beta Beam - Loss Deposition, EURONS/EURISOL, E.Wildner
The Decay Ring Optics
A. Chance et al., CEA Saclay
Decay ring:
C~7km
LSS~2.5 km
s (m)
Optical functions (m)
primary collimator
One straight section used for momentum collimation.
Beta Beam - Loss Deposition, EURONS/EURISOL, E.Wildner

7. Particle removal & loss
Arcs
Decay products
Straight section
Merging increases longitudinal beam size
Momentum collimation
Primarily accumulated and extracted at end with first dipole to external dump.
Not treated yet:
Betatron-Collimation
Emergency cases (failure modes)
Beta Beam - Loss Deposition, EURONS/EURISOL, E.Wildner

8. Large Aperture Requirements
Dipole
6Li 3+
Absorber
18F 9+
Beam Pipe
8 cm radius needed for the horizontal plane where the decay products cause daughter beams + 1 cm for the sagitta (no curved magnet)
4 cm for the vertical plane
Beta Beam - Loss Deposition, EURONS/EURISOL, E.Wildner

9. The Large Aperture Dipole, first feasibility study
Courtesy Christine Vollinger
high tip field, non-critical
6 T
LHC ”costheta” design
Good-field requirements only apply to about half the horizontal aperture.
Beta Beam - Loss Deposition, EURONS/EURISOL, E.Wildner

10. The Decay Products in the arcs
Courtesy: A. Chancé
Dipole
Deposited Power (W/m)
s (m)
Arc, repetitive pattern
Beta Beam - Loss Deposition, EURONS/EURISOL, E.Wildner

11. Heat Deposition Calculations
Need to interface beam code and code for tracking particles in matter
Choice:
Beam Code: ACCIM (Developed at TRIUMF, many options developed specifically for the decay simulations,
responsible Frederick Jones, TRIUMF)
Particle Tracking in Matter: FLUKA
"FLUKA: a multi-particle transport code", A. Fasso`, A. Ferrari, J. Ranft, and P.R. Sala, CERN (2005), INFN/TC_05/11, SLAC-R-773
"The physics models of FLUKA: status and recent developments", A. Fasso`, A. Ferrari, S. Roesler, P.R. Sala, G. Battistoni, F. Cerutti, E. Gadioli, M.V. Garzelli, F. Ballarini, A. Ottolenghi, A. Empl and J. Ranft, Computing in High Energy and Nuclear Physics 2003 Conference (CHEP2003), La Jolla, CA, USA, March 24-28, 2003
Beta Beam - Loss Deposition, EURONS/EURISOL, E.Wildner 11 11

12. Beta Beam - Loss Deposition, EURONS/EURISOL, E.Wildner
The beam code ACCSIM
Accsim, developed at TRIUMF, is a multiparticle tracking and simulation code for synchrotrons and storage rings.
Some applications: CERN (S)PS(B), KEK PS, J-PARC, SNS, ...
Incorporates simulation tools for injection, orbit manipulations, rf programs, foil, target & collimator interactions, longitudinal and transverse space charge, loss detection and accounting.
Interest for Betabeam: to provide a comprehensive model of decay ring operation including injection (orbit bumps, septum, rf bunch merging), space charge effects, and losses (100% !)
Needed developments for Betabeam:
Arbitrary ion species, decay, secondary ions.
More powerful and flexible aperture definitions (for absorbers)
Tracking of secondary ions off-momentum by >30% (unheard of in conventional fast-tracking codes)
Detection of ion losses: exactly where did the ion hit the wall?
-- a challenge for tracking with the usual ”element transfer maps”
Beta Beam - Loss Deposition, EURONS/EURISOL, E.Wildner

13. Beta Beam - Loss Deposition, EURONS/EURISOL, E.Wildner
Accsim and Fluka
Accsim as event generator for FLUKA
Identify “region of interest”: sequence of Accsim elements corresponding to the representative arc cell modeled in FLUKA.
Tracking macro-particles representing fully populated ring (9.66×1013 He or 7.42×1013 Ne), with decay.
Detect and record two types of events:
Ions that decayed upstream of the cell and have survived to enter the cell.
Ions that decay in the cell.
For each event the ion coordinates and reference data are recorded for use as source particles in FLUKA.
Beta Beam - Loss Deposition, EURONS/EURISOL, E.Wildner

14. Heat Deposition Model, one cellQ
Absorbers B B
”Overlapping” Quad to check repeatability of pattern
Q (ISR model)
B (new design) B
No Beampipe (angle large)
Concentric cylinders, copper (coil), iron (yoke) Q
Beta Beam - Loss Deposition, EURONS/EURISOL, E.Wildner

15. Coordinate transformation
ACCSIM/FLUKA and inverse
We used Mathematica based on the survey options of ”BeamOptics” * to generate FLUKA Particle file
Useful if ACCSIM could integrate the transformation code y
ACCSIM x y
FLUKA
[cm] x
[cm]
* ”Beam Optics : a program for analytical beam optics”
Autin, Bruno; Carli, Christian; D'Amico, Tommaso Eric; Gröbner, Oswald; Martini, Michel; Wildner, Elena; CERN-98-06
Beta Beam - Loss Deposition, EURONS/EURISOL, E.Wildner

16. Particle generation and treatment
1. ACCSIM tracks 6Li and 18F particle decaying in the ring up to cell entry
2. ACCSIM gives coordinates and momentum vectors of particles just decayed in cell
3. Particles escaping the vacuum pipe are treated by Fluka
End of cell
Decayed in cell
Escaping
Decayed in machine with absorbers inserted in ACCSIM
Start of cell
Beta Beam - Loss Deposition, EURONS/EURISOL, E.Wildner

17. Overall Power Deposition
Normalized to a decay rate in cell:
He: decays/s
Ne: decays/s
6Li
18F
Compare to technical limits (10W/m)
not exceeding for either ion
Beta Beam - Loss Deposition, EURONS/EURISOL, E.Wildner

18. Local Power Deposition
Local power deposition concentrated around the mid plane.
Limit for quench 4.3mW/cm3
(LHC cable data including margin)
Situation fine for 6Li
18F: 12 mW/cm3
Beta Beam - Loss Deposition, EURONS/EURISOL, E.Wildner

19. Alternative solutions
Open Mid Plane Magnet a better solution?
Profit of work ongoing at CERN
Use this model in simulations
Introduce a “Beam Screen”
Courtesy Erk Jensen, CERN
Beta Beam - Loss Deposition, EURONS/EURISOL, E.Wildner

20. Beta Beam - Loss Deposition, EURONS/EURISOL, E.Wildner
Conclusion and Future
A protocol between the beam code Accsim and the material tracking code (FLUKA) has ben developed for the beta beam studies. ACCSIM to be used for the whole accelerator chain, for decay data production.
Accsim now to be complemented with the packages made for model creation and for coordinate transformation
(Accsim->FLUKA->Accsim)
First results indicate that the deposited power is exceeding the limits locally, but not globally. Optimisation or another magnet design needed.
The structure with absorbers would need special arrangements for the impedance induced. A thick liner inside the dipole could be an alternative
Alternative dipole design with VERY large aperture or open mid-plane (new development, ongoing).
Apply simulation tools for momentum collimation.
Beta Beam - Loss Deposition, EURONS/EURISOL, E.Wildner