Tracking and particle-matter interaction studies in the beta-beam decay ring

1
Tracking and particle-matter interaction studies
in the beta-beam decay ring

• E.Wildner, A. Fabich (CERN)
• Common EURISOL DS - EURONS Town MeetingHelsinki,
  Finland, 17-19 September 2007

2
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.

3
Possible Beta Beam Complex
High-energy part
Low-energy part
Acceleration
Neutrino source
Ion production
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 100 18Ne 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
3
4
Beta-beam tasks (Eurisol Design Study)
From Overview by M. Benedikt, Beta Beam Task
Meeting in May 2007
4
5
Particle Turnover
1 MJ beam energy/cycle injected ?
equivalent ion number to be removed 25 W/m
average Momentum collimation
51012 6He ions to be collimated per
cycle Decay 51012 6Li ions to be removed per
cycle per meter
6
The Decay Ring Optics
A. Chance et al., CEA Saclay

• Decay ring
• C7km
• LSS2.5 km

One straight section used for momentum
collimation.
7
Particle removal loss

• Arcs
• Decay products
• Straight section
• Merging increases longitudinal beam size
• Momentum collimation
• Decay products
• Primarily accumulated and extracted at end with
  first dipole to external dump.
• Not treated yet
• Betatron-Collimation
• Emergency cases (failure modes)

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
9
The Large Aperture Dipole, first feasibility study
Courtesy Christine Vollinger
6 T
LHC costheta design
Good-field requirements only apply to about half
the horizontal aperture.
10
The Decay Products in the arcs
Courtesy A. Chancé
Deposited Power (W/m)
s (m)
Arc, repetitive pattern
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-2005-10 (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
11
12
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 gt30
  (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

13
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 100000 macro-particles representing
  fully populated ring (9.661013 He or 7.421013
  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.

14
Heat Deposition Model, one cell
Q
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
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
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
17
Overall Power Deposition
Normalized to a decay rate in cell He 5.37 109
decays/s Ne 1.99 109 decays/s
6Li
18F

• Compare to technical limits (10W/m)
• not exceeding for either ion

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

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
20
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-gtFLUKA-gtAccsim)
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.