Transcript Collimation of accelerated radioisotopes for beta-beams

Design Study
Collimation of accelerated
radioisotopes for beta-beams
P. Delahaye, AB-ATB-EET
FLUKA user meeting 27/11/08
Generation of n beams by postaccelerating radioisotopes
• A pure beam of ne to study the nenm oscillation
– A beam of ne, ne from b-decaying nuclides
• A Lorentz boost for a collimated beam (high g)
For a boost in an arbitrary direction with velocity , it is convenient to
decompose the spatial vector into components perpendicular and parallel to
the velocity :
… . Then only the component in the direction of
is 'warped' by the gamma factor:
where now
Lorentz boost
q
q1/g
P. Delahaye, FLUKA user meeting, 27/11/08
FP6 baseline scenario
Design Study
2.9 1018 n/year
18Ne: 1.1 1018n/year
6He:
TOP – DOWN APPROACH
6He: 2. 1013 /s
18Ne: 2. 1013/s
A year of exploitation: 107 s
What I won’t talk about…
• 6He and 18Ne as first candidates (FP6)
9Be(n,a)
Converter technology:
(J. Nolen, NPA 701 (2002) 312c)
T. Stora et al, EURISOL-TN03-25-2006-0003
07/07/2015
CEA Saclay Optimized Geometry
N Thollieres et al. EURISOL-TN03-25-2006-0004
4
Production
•
18Ne
– 2GeV p on 100kW MgO target: factor 24 missing
– Low energy 3He beam on LiF target and on 16O
gaseous target, tests at LLN
– Multiple targets and cooling and accumulating
target
rings
FC
60 cm diameter
target MgO
2MW 3He beam (14.8MeV, 130mA)
1013 18Ne/sp beam
Ge detector
M. Loiselet and S. Mitrofanov,
LLN
FP7: novel ideas
Beam cooling with ionisation losses – C. Rubbia, A Ferrari, Y. Kadi and V.
Vlachoudis in NIM A, 568 (2006) 475
7Li
6Li
IGISOL
Gas inlet
Gas cell
BEAM
7Li(d,p)8Li
6Li(3He,n)8B
ISOL or IGISOL extraction
M. Lindroos et al, NIC-IX
proceedings,
P. Delahaye and U. Koester,
Nufact08 proceedings
Extraction
See also: Development of FFAG accelerators and their applications for
intense secondary particle production, Y. Mori, NIM A562(2006)591
8Li, 8B:
higher Q value
Longer baseline scenario
C. Rubbia arxiv.org/pdf/hep-ph/0609235
6
Collimation for beta-beams
• Stacking mechanism in the decay ring:
asymetric bunch merging
Steady –state stack amounts to:
•8.9 shots accumulated for 6He
•14.0 for 18Ne
Last step:
Symmetric merging
S. Hancock, ESME simulations
M. Benedikt, S. Hancock, A novel scheme for
injection and stacking of radioactive ions at
high energy, NIM A 550 (2005) 1–5
S. Hancock et al., Stacking Simulations in the
Beta-beam Decay Ring, EPAC 2006
Stacking benefit
07/07/2015
8
Momentum collimation
50% of 1013/s
75% of 4.3 1012/s
18Ne
6He
Momentum
collimation
Momentum
collimation
A. Fabich,
EURISOL town
meeting 2007
Arc
Arcs
Arc
Arc
Straight sections
injection
merging
merging
1.6MW in 0.3s
p-collimation
2.8MW in 0.3s
p-collimation
injection
Straight section
Asymetric bunch merging
Steady –state stack amounts to:
•8.9 shots accumulated for 6He
•14.0 for 18Ne
Last step:
Symmetric merging
S. Hancock, ESME simulations
M. Benedikt, S. Hancock, A novel scheme for
injection and stacking of radioactive ions at
high energy, NIM A 550 (2005) 1–5
S. Hancock et al., Stacking Simulations in the
Beta-beam Decay Ring, EPAC 2006
P. Delahaye, FLUKA user meeting, 27/11/08
Momentum collimation
• The collimation duration
can be tuned according to
the RF program
• Energy distribution of
the stack halo was
calculated with ESME for
6He and 18Ne
Bunch shortening
when raising the
second harmonics
6He
Shaving off when d>2.5‰
Recently Fred Jones implemented the bunch shortening step into ACCSIM for 6He starting
from a longitunal distribution generated by ESME (when second harmonics=0)
P. Delahaye, FLUKA user meeting, 27/11/08
ACCSIM calculation
• Longitudinal phase space before bunch
shortening from Steve
• Shortened RF program – 12ms instead of typically
300ms (~2 synchrotron periods)
P. Delahaye, FLUKA user meeting, 27/11/08
ACCSIM calculation
• Repeated for 18Ne
« Taking care that the longitdunal emittance doesn’t filament »
P. Delahaye, FLUKA user meeting, 27/11/08
Results
• Placement of the primary collimator as
defined by A. Chancé in the lattice
• Condition (B. Jeanneret et al.)
Has been verified
• Collimator element +-X under ACCSIM
has been modified/corrected and validated
• Loss maps were created and adapted for
an easy use under FLUKA
•Number of element where lost,
number of turn, X, Y, Z(S), TX,TY, TZ
direction cosinuses and Tk
Cut after bunch shortening
P. Delahaye, FLUKA user meeting, 27/11/08
Total deposited power
From ESME (S. Hancock):
Number of scraped ions increases linearly
with time = quite constant power
ACCSIM
18Ne
Oscillations:
Probably non physical!!
Avg power
Variation +-50% according to average
Similar pattern for 6He
P. Delahaye, FLUKA user meeting, 27/11/08
FLUKA simulations
• « Minimal » collimation section
– Straight section + 2nd bump
– Magnetic fields, beam pipe and collimators
ACCSIM??
ACCSIM
P. Delahaye, FLUKA user meeting, 27/11/08
Placement of the collimators
• Primary and « secondary » collimators placed
according to the beam enveloppe at d=2.5‰
• In blue:
Negative energies
• Beam enveloppe:
•dmax=-2.5‰
•e=2.6p.mm.mrad
(100%)
1) Only horizontal collimation
2) Not so much effect of the secondary if too far away from the beam enveloppe!!
P. Delahaye, FLUKA user meeting, 27/11/08
Different sets of conditions
• Thickness of the primary collimator (10, 20,
30, 50 and 100cm blocks)
• Distance from the beam enveloppe for the
secondary collimators
• Material of the collimators (12C as for LHC,
Copper)
P. Delahaye, FLUKA user meeting, 27/11/08
Loss map for a typical set-up
• 6He
GeV/pr/cm3
GeV/pr/cm3
Primary collimator 30cm
P. Delahaye, FLUKA user meeting, 27/11/08
Results
• ACCSIM (primary collimator)
– Primary collimator on the beam enveloppe as
defined above
– 6He: ~5.6% of the bunch is collimated
ESME: 6.3%
– 18Ne: ~6.0% of the bunch is collimated
ESME: 5.4%
P. Delahaye, FLUKA user meeting, 27/11/08
Average power 6He
12C
collimators, secondaries 1m long at 4mm from beam enveloppe
6He:
Average power (W)
5 1012 particles lost/cycle
1s collimation time (300ms:3X more!!)
25000
20000
15000
Col1
Usual limit
10000
Col2
Col3
5000
0
0
20
40
60
80
100
120
Thickness primary (cm)
P. Delahaye, FLUKA user meeting, 27/11/08
Average power 18Ne
12C
collimators, secondaries 1m long at 4mm from beam enveloppe
18Ne:
Average power (W)
3.4 1012 particles lost/cycle
1s collimation time (300ms:3X more!!)
16000
14000
12000
Usual limit 10kW
10000
col1
8000
col2
col3
6000
4000
2000
0
0
10
20
30
40
50
60
Thickness primary (cm)
P. Delahaye, FLUKA user meeting, 27/11/08
Energy balance
• Taking 30 cm as the reference case, only 27%
(32%) of energy is dissipated in the system
(mainly collimators and beam pipe) for 6He
(18Ne)
• In reality the rest will be dumped in the
surrounding materials, and in the bump
P. Delahaye, FLUKA user meeting, 27/11/08
Escaping energy
6He
30 cm primary collimator
3%
0.1%
3%
53%
13%
Mainly 6He or 18Ne with
• no interaction
• small scattering angles
Corrected for in the
calculation of the
deposited power!!
P. Delahaye, FLUKA user meeting, 27/11/08
More collimation and less dump…
• 3 primaries (30cm) instead of 2 secondaries
– 2nd and 3rd Collimators are placed on the beam
enveloppe
18Ne
Average power (W)
16000
14000
12000
Less deposited power on the 2nd
and 3rd collimator!
col1
col2
Due to thickness
mainly
10000
8000
6000
col3
4000
2000
0
0
10
20
30
40
50
60
Thickness primary (cm)
P. Delahaye, FLUKA user meeting, 27/11/08
More collimation and less dump…
• Trying another material: 29Cu
– 1 primary 30 cm 2 secondaries 100cm
Primary 112kW!!
16000
14000
12000
10000
col1
8000
col2
6000
col3
4000
Secondaries more efficient!
2000
0
0
10
20
30
40
50
60
P. Delahaye, FLUKA user meeting, 27/11/08
Conclusions
• A primary collimator of 30cm will probably stand the
deposited power for 6He and 18Ne
• Efficient collimation on the secondaries implies
probably the use of other material (Cu?)
• Absorber materials after the primary collimator
• A detailed study of the losses in the surrounding
material (magnets in particular!) is absolutely needed
• The losses at the bump might be quite critical
• Not so many fragments passing the bump (3H: 5‰ per
primary 6He)
P. Delahaye, FLUKA user meeting, 27/11/08