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Collimation of accelerated radioisotopes for beta-beams

Collimation of accelerated radioisotopes for beta-beams . P. Delahaye, AB-ATB-EET FLUKA user meeting 27/11/08.

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Collimation of accelerated radioisotopes for beta-beams

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  1. Collimation of accelerated radioisotopes for beta-beams P. Delahaye, AB-ATB-EET FLUKA user meeting 27/11/08

  2. For a boost in an arbitrary direction withvelocity , itisconvenient to decompose the spatial vectorinto components perpendicular and parallel to the velocity : … . Thenonly the component in the direction of is 'warped' by the gamma factor: wherenow q1/g q Lorentz boost Generation of nbeams by post-acceleratingradioisotopes • 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)

  3. FP6 baseline scenario TOP – DOWN APPROACH 6He: 2.9 1018n/year 18Ne: 1.1 1018n/year 6He: 2. 1013 /s 18Ne: 2. 1013/s A year of exploitation: 107 s

  4. What I won’t talk about… Converter technology: (J. Nolen, NPA 701 (2002) 312c) CEA Saclay OptimizedGeometry 9Be(n,a) T. Stora et al, EURISOL-TN03-25-2006-0003 N Thollieres et al. EURISOL-TN03-25-2006-0004 6He and 18Ne as first candidates (FP6)

  5. Production • 18Ne • 2GeV p on 100kW MgOtarget: factor 24 missing • Lowenergy3He beam on LiFtarget and on 16O gaseoustarget, tests at LLN • Multiple targets and cooling and accumulating rings 60 cm diametertargetMgO 2MW 3He beam (14.8MeV, 130mA) 101318Ne/s M. Loiselet and S. Mitrofanov, LLN • 18Ne • 2GeV p on 100kW MgOtarget: factor 24 missing • Lowenergy3He beam on LiFtarget and on 16O gaseoustarget, tests at LLN

  6. Gas inlet Gas cell BEAM Extraction FP7: novelideas Beam cooling with ionisation losses – C. Rubbia, A Ferrari, Y. Kadi and V. Vlachoudis in NIM A,568(2006) 475 7Li(d,p)8Li 6Li(3He,n)8B 7Li 6Li IGISOL ISOL or IGISOL extraction M. Lindroos et al, NIC-IX proceedings, P. Delahaye and U. Koester, Nufact08 proceedings 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

  7. Collimation for beta-beams • Steady –state stackamountsto: • 8.9 shotsaccumulated for 6He • 14.0 for 18Ne Last step: Symmetricmerging 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 • Stackingmechanism in the decay ring: asymetricbunchmerging

  8. Stackingbenefit

  9. Momentum collimation Arcs Arc Arc Straight section Arc Straight section Momentum collimation 50% of 1013/s 75% of 4.3 1012/s Momentum collimation 18Ne 6He Fabich, EURISOL town meeting 2007 Straight sections merging p-collimation injection 1.6MW in 0.3s 2.8MW in 0.3s merging p-collimation decay losses injection decay losses

  10. Asymetricbunchmerging • Steady –state stackamountsto: • 8.9 shotsaccumulated for 6He • 14.0 for 18Ne Last step: Symmetricmerging 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

  11. Momentum collimation • The collimation durationcanbetunedaccording to the RF program • Energy distribution of the stack halo wascalculatedwith ESME for 6He and 18Ne Bunchshorteningwhenraising the second harmonics 6He Shaving off whend>2.5‰ Recently Fred Jones implemented the bunchshorteningstepinto ACCSIM for 6He startingfrom a longitunal distribution generated by ESME (when second harmonics=0)

  12. ACCSIM calculation • Longitudinal phase spacebeforebunchshorteningfrom Steve • Shortened RF program – 12ms instead of typically 300ms (~2 synchrotron periods)

  13. ACCSIM calculation • Repeated for 18Ne « Taking care that the longitdunal emittance doesn’t filament »

  14. Results • Placement of the primarycollimator as defined by A. Chancé in the lattice • Condition (B. Jeanneret et al.) • Has been verified • Collimatorelement +-X under ACCSIM has been modified/corrected and validated • Lossmapswerecreated and adapted for an easy use under FLUKA • Number of elementwherelost, number of turn, X, Y, Z(S), TX,TY, TZ direction cosinuses and Tk Cutafterbunchshortening

  15. Total deposited power From ESME (S. Hancock): Number of scraped ions increaseslinearlywith time = quite constant power ACCSIM 18Ne Avgpower Oscillations: Probably non physical!! Variation +-50% according to average Similar pattern for 6He

  16. FLUKA simulations • « Minimal » collimation section • Straight section + 2ndbump • Magneticfields, beam pipe and collimators ACCSIM?? ACCSIM

  17. Placement of the collimators • Primary and « secondary » collimatorsplacedaccording to the beam enveloppe atd=2.5‰ • In blue: • Negativeenergies • Beam enveloppe: • dmax=-2.5‰ • e=2.6p.mm.mrad • (100%) 1) Only horizontal collimation 2) Not somucheffect of the secondary if too far awayfrom the beam enveloppe!!

  18. Different sets of conditions • Thickness of the primarycollimator (10, 20, 30, 50 and 100cm blocks) • Distance from the beam enveloppe for the secondarycollimators • Material of the collimators (12C as for LHC, Copper)

  19. Lossmap for a typicalset-up • 6He GeV/pr/cm3 GeV/pr/cm3 Primarycollimator 30cm

  20. Results • ACCSIM (primarycollimator) • Primarycollimator on the beam enveloppe as definedabove • 6He: ~5.6% of the bunchiscollimated • 18Ne: ~6.0% of the bunchiscollimated ESME: 6.3% ESME: 5.4%

  21. Average power 6He 12C collimators, secondaries 1m long at 4mm frombeam enveloppe 6He: 5 1012particleslost/cycle Average power (W) 1s collimation time (300ms:3X more!!) Usuallimit Thicknessprimary (cm)

  22. Average power 18Ne 12C collimators, secondaries 1m long at 4mm frombeam enveloppe 18Ne: 3.4 1012particleslost/cycle Average power (W) 1s collimation time (300ms:3X more!!) Usuallimit 10kW Thicknessprimary (cm)

  23. Energy balance • Taking 30 cm as the reference case, only 27% (32%) of energyisdissipated in the system (mainlycollimators and beam pipe) for 6He (18Ne) • In reality the restwillbedumped in the surroundingmaterials, and in the bump

  24. Escapingenergy 3% 6He 30 cm primarycollimator 0.1% 3% 53% 13% • Mainly6He or 18Ne with • no interaction • smallscattering angles Corrected for in the calculation of the deposited power!!

  25. More collimation and less dump… • 3 primaries (30cm) instead of 2 secondaries • 2nd and 3rd Collimators are placed on the beam enveloppe Average power (W) 18Ne Lessdeposited power on the 2nd and 3rd collimator! Due to thicknessmainly Thicknessprimary (cm)

  26. More collimation and less dump… • Tryinganothermaterial: 29Cu • 1 primary 30 cm 2 secondaries 100cm Primary 112kW!! Secondaries more efficient!

  27. Conclusions • A primarycollimator of 30cm willprobably stand the deposited power for 6He and 18Ne • Efficient collimation on the secondariesimpliesprobably the use of othermaterial (Cu?) • Absorber materialsafter the primarycollimator • A detailedstudy of the losses in the surroundingmaterial (magnets in particular!) isabsolutelyneeded • The lossesat the bumpmightbequitecritical • Not somany fragments passing the bump (3H: 5‰ per primary6He)

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