1. Status of the Production Ring for Beta Beams Studies
ICE Section Meeting,
22/10/10
Status of the Production Ring for Beta Beams Studies
E. Benedetto
(CERN & NTU Athens)
Acknowledgements: G. Arduini, J. Barranco, C. Bracco, M. Chanel, P. Chiggiato, C. Hansen, R. Garoby, B. Holzer, V. Previtali, V. Vlauchoudis, E. Wildner (CERN), D. Neuffer (FNAL), O. Boine-Frankenheim (GSI), Y. Mori (KURRI), M. Schaumann (RWTH Aachen), …

2. Outline Introduction Status of the studies Next steps
Beta-beams and the Production Ring
Ionization cooling
Status of the studies
Preliminary lattice design
Tracking simulations
Technological challenges
Next steps

3. ISOL target, Collection
b beams
Aim: production of electron (anti-)neutrino beams from the b decay of radioactive ions circulating in a storage ring
ISOL target, Collection
Ion production PR
Ion Linac 20 MeV
8B/8Li .
Radioactive
ion production
8Li, 8B
6He, 18Ne

4. stripper, target & absorber
Production Ring
7Li(d,p)8Li
6Li(3He,n)8B
7Li
6Li
stripper, target & absorber
RF cavity
C. Rubbia, A. Ferrari, Y. Kadi, V. Vlachoudis, Beam cooling with ionization losses, NIM A 568 (2006)
→ see also Y.Mori, NIM A 562 (2006) 591, proton FFAG with internal Be target for neutron production (but no need of (dp/p) cooling)
Compact ring & thin internal target
Enhance production 8Li/8B (~1014/s) by multi passages trough the target
Inverse kinematics: Li ~25MeV and D or 3He supersonic gas-jet target
Multi Coulomb Scattering + energy target
Ionization cooling

5. Ionization cooling
Energy losses (dE/ds) in the target material (Bethe-Bloch)
Only longitudinal component recovered in RF cavities
→ Transverse emittance shrinks
Cooling in 6D
(dE/ds) ~ b-2 smaller at higher energies → cooling not effective in longitudinal
need coupling between transverse and longitudinal:
→ Dispersion & wedge-shaped target
Faster ions will travel on an outer orbit and see a larger target thickness → they will get more (dE/ds)
Target:
closed orbit = 5 cm
t = mg/cm2
If angle = 20o → Dx> 24 cm

6. The proposed lattice 25 MeV 7Li (br ~0.6) C = 12m
5 quadrupole families
Normal-conducting magnets
2-fold mirror symmetry
Target → Dx~50cm
RF cavity → in region Dx=0 m
M. Schaumann, CERN-THESIS
RF cavity
Target
NOT OPTIMIZED YET

7. Tracking simulations SixTrack Adapted to the Production Ring needs
Fully 6D, symplectic, reads lattice form MADX output,…
Collimation version
Tracking large # of particles,
Interaction w. collimators
Adapted to the Production Ring needs
Target implemented as a special collimator element:
Random transverse kick Dx’, Dy’ due to Multiple Coulomb scattering
(Gaussian distribution, <sc2>)
Random energy losses DE :
mean value → Bethe-Bloch
energy straggling → gaussian distribution assumed
Rms emittances & Intensity evolution diagnostics
We have Lithium ions, Sixtrack is for protons
→ need proton equivalent ring (same Br & Dp/p recovered in RF cavity)

8. Tracking simulations: zero wedge angle
From analytical considerations:
ex~90 mm
ey~11 mm
t ~ 170 turns

9. Tracking simulations: choice of the angle

10. Tracking simulations: wedge-angle =6o

11. Technological challenges (1)
Production of stable Li in ECR-source
if we want 1014 ions/s of 8Li
→ we need ~1015/s 7Li
(since s7Li(d,p)8Li=0.1 stot)
“standard” ECR source produces ~30 mA (Li1+)
→ = Li1+/s x 50% (transmission through LINAC) =~ /s → factor >10 missing

12. Technological challenges (2)
Collection device
2mm Tantalum foils
extraction by heating-up
Issues:
diffusion/effusion efficiency
small angle (q~10o) of products → need collection device close to the beam, but it can intercept it!!!
Rutherford scattered particles
8B-ions
Collection on axis
S. Mitrofanov

13. Technological challenges (3)
Supersonic gas jet target
Wedge shape (larger thickness for larger Dp/p)
Parameters
Thickness
(mg/ cm2)
(atoms/cm2)
0.27
5 1019
Diameter
(cm) 5
Density
(mg/cm3)
~0.06
Pressure
(Torr)
250
Mach n. - 4
Nozzle throat
(mm)
3.26
P_plenum
(atm)
~3.5
Length
~30
from C.Rubbia’s:
existing cluster-jet targets reach up to 1015 atoms/cm2
→ factor 104 missing

14. Cluster supersonic-jet target
A. Koukaz
Meeting at GSI, 29/10/09

15. Cluster supersonic-jet target
We need ~ 50x50 mm
50 mm
20o
Cluster supersonic-jet target
A. Koukaz
Meeting at GSI, 29/10/09
Target density = /cm2
We need ~ 1019 /cm2

16. Technological challenges (4)
Possible solutions:
Increase injected beam intensity → already at limit of stable 7Li ion source (~160mA required from the LINAC)
Run with poor vacuum (as long as the residual gas is thin compared to the target) → NO!, causes problems to the RF cavity (capacitive-loaded cavity)
Lower target density = less ion productions, but also = better lifetime & higher intensity circulating → more detailed studies are needed, another regime since Multiple Coulomb Scattering not valid any longer… → but gaining a factor 104, hmm…
Other possibility: use D or 3He beam & Lithium target (solid, waterfall, droplets,…?)
set-up lattice for cooling
study feasibility (power dissipation on target, collection,…)

17. Conclusions
Tracking tools for i-cooling studies fully in place and agree with analytical considerations
Lattice need to be optimized (reduce the target, compensate large natural Qp,…)
BUT Still a lot of work have a feasible solution to produce enough flux of isotopes for Beta-Beams Neutrino physics.
e.g. Existing gas-jet targets cannot reach the densities proposed in [C.Rubbia, et. al] in a vacuum environment

18. Next steps & ongoing work (1)
Conclude work on Li-beam & gas-jet target
TO DO: lattice optimization for i-cooling (e.g. reduce b*, eventually compensate large Q’,…)
Injection scheme to be studied in more details
Collective effects
BUT, since gas-jet density maybe a show-stopper...
→ Started working on an alternative solution: D (or 3He) beam + Li target:
technological feasibility !!!, lattice and i-cooling
Torsten Weber (RWTH Aachen U.) helping us

19. Next steps & ongoing work (2)
Beam-target interaction:
Range of validity of Bethe-Bloch & Multiple Coulomb Scattering formulas
for low density target
to use correct model inside tracking simulations (since we are at the limits of ionization cooling capabilities)
Collaboration with V. Vlachoudis + D. Sinuela
Integration of FLUKA in SixTrack
Production cross-section (& collection efficiency)
Measurements at INFN Legnaro and Napoli ongoing
Will have a meeting next week

20. Next steps & ongoing work (3)
Contacts with Y.Mori (KURRI, Osaka)
proton FFAG with internal Be target for BNCT
They have a running machine!
Scaling FFAG (Q’~0)
Large acceptance for both
horiz.(10-3) and longit.(10%)
no need of (dp/p) cooling
Similar parameters than ours
→ Y.Mori, NIM A 562 (2006) 591
→ K.Okabe et al, IPAC10, EPAC08,…

21. Back-up slides

22. Cooling rates and equilibrium emittance (1)
Damping time
Equilibrium emittances
ex~90 mm
ey~11 mm

23. Cooling rates and equilibrium emittance (2)
straggling
<0 → blow-up
<0 !!!!
If now we introduce Dispersion (and a triangular target shape):
at a different orbit Dx=D Dp/p

24. Cooling rates and equilibrium emittance (3)
If now we introduce Dispersion (and a triangular target shape):..
Cooling can be transferred from transverse to longitudinal thanks to
Dispersion + triangular target
can also introduce coupling x-y
Since sum of the three partition number is always the same, is computed for Dx=0:
0.4 for 6Li
0.01 for 7Li
Due to Bethe-Bloch shape, NO possibility to effectively cool → but only to keep a constant emittance or not to heat it “too much”

25. FFAG-ERIT
Courtesy Y.Mori, K.Okabe

26. Courtesy Y.Mori, K.Okabe

27. Courtesy Y.Mori, K.Okabe