Developments on FRIB separator ion-transport simulations Mauricio Portillo 2010 Dec 16

1. Developments on FRIB separator ion-transport simulationsMauricio Portillo2010 Dec 16

2. Outline • Short intro to the codes being used to develop and evaluate FRIB separator designs • Short review of the current FRIB separator design • multiple stage separation • momentum compression in preseparator • position of beam dump • Examples of calculations that are being used in the design • Higher order correction • Higher order wedge shaping • Power distribution for beam dump design Slide 2

3. Overview of Codes • Ion Optics • GICOSY (map calculation up to 5th order) • COSY (map calculation to arbitrary order, in principal) • Map-based particle transport • COSY (transport and interaction with matter, Monte Carlo) • LISE++ (1st order convolution & projectile transport via Taylor maps, higher order Monte Carlo) • MOCADI (Up to 3rd order projectile transport and interaction with matter, Monte Carlo) • Beam/matter interaction • Atomic interactions (ATIMA, GLOBAL) • Nuclear interactions (EPAX, MCNPX, various reaction kinematics and cross section models in LISE++) note: Production in wedge is selectable by flag in LISE++ and COSY (MOCADI?)

4. Primary Beam Comparison: NSCL to FRIB Note: NSCL rates taken from NSCL beam list.

5. FRIB 3 Stage Separator Concept Acceptance goal am, bm = ±40 mrad 10% dp/p

6. First Order Ion-Optical Layout of Three Stage Separator 90º rot Wedge2 Wedge1 Wedge3 Order1 Ray properties xm, ym = ±0.5 mrad am, bm = ±40 mrad dPm = +5%, 0, -5% Order 1

7. Preseparator (Stage1) Design:Optimizing for Momentum-compression Maximum rigidity: 8 T-m x vs s y vs s Ray properties xm, ym = ±0.5 mrad am, bm = ±40 mrad dPm = +5%, 0, -5% Wedge1 position 1:3 ratio in dispersion for 1/3 dp-compression 40 ft

8. Effect of Momentum Compression in the Preseparator • LISE and COSY calculations of compression of a 160 MeV/u 77Ni beam A1900 with no compression Counts [arb.units] FRIB Stage1 momentum spread reduced by ~3 x’=±100 mrad Resulting emittance growth in dispersive plane by ~3 x=±20 mm L. Bandura, B. Erdelyi, M. Hausmann, T. Kubo, J. Nolen, M. Portillo, B.M. Sherrill, “Fragment separator momentum compression schemes, NIMA (under publication) Slide 8

9. Stage1: 5th order ray calculations COSY LISE with ±5% dp/p slit at beam dump x vs s ±100 mm y vs s ±100 mm Slide 9

10. Stage1: Transmission Efficiencies Slide 10

11. Stage1 focal plane: 5th order COSY wedge correction Effect of turning wedge shape correction Minimizing (x,d), (x,dd) and (x,ddd) with w1, w2, w3, ... dp/p% vs x Plot limits: ±3% dp/p mrad vs ±100 mm Slide 11

12. 5th order LISE wedge correction x-rms = 14 mm Effect of turning on Order 2 wedge shaping correction x-rms = 11 mm dp/p% vs x Plot limits: ±3% dp/p mrad vs ±100 mm Slide 12

13. 3rd order MOCADI wedge correction x-rms = 17 mm Effect of turning on Order 2 wedge shaping correction x-rms = 13 mm dp/p% vs x Slide 13

14. Comparison of wedge optimization results • All three codes are in reasonable agreement after optimization * both LISE and MOCADI required slight adjustments • Going beyond second order shaping offers little benefit • Question1: Is it necessary and/or worth the cost to do second order shaping? • Question2: Is it practical to shape (x,d) and (x,dd) by magnet optical tuning? 0.3 micron @ 64 mm Slide 14

15. Controlled dumping of the primary beam First dipole magnet spreads beam according to magnetic rigidity Bρ = p/q Rigidity of primary beam can differ from that of the desired exotic nucleus by ±40% beam Target Deflection range of primary beam trajectories

16. Primary Beam on Beam Dump -38% dp/p • LISE Monte Carlo calculations are aiding in beam dump design • The power distribution plots at right illustrate an extreme case in terms of phase space and position range • Units of power are in Watts/cm2 -4% dp/p Example: Products from 287 MeV/u 18O -> C-4000 at beam dump region for various dp/p offset settings +38% dp/p

17. Stages 2 and 3 • Post separation stages use existing A1900 magnets • A mirror symmetric arrangement is being considered • Matching in the non-dispersive plane accounts for emittance growth x vs s Maximum rigidity: 7 T-m y vs s Wedge2 Wedge2 Stage 3 Stage 3 Wedge2’ Stage 2 - Alternative

18. Mass separation in both x- and y- planes Applying A and Z separation with at least on second wedge enhances mass separation FRIB A1900 • 78Ni 77Ni 76Ni Example y vs x mass separation plots illustrates this point

19. Summary • Codes have been developed further in response to challenges found during FRIB work • Further developments can make design and on-line use better • Tolerance of wedge shaping will be more critical for higher dp/p acceptances

20. Acknowlegements • Matt Amthor, Laura Bandura, Georg Bollen, Marc Hausmann, Dave Morrissey, Brad M. Sherrill, O. Tarasov and the rest of the FRIB team • Toshi Kubo, RIKEN • Jerry Nolen, ANL

21. Vielen dank

22. FRIB separator ray plots: Order 1 x vs s ±100 mrad vs ±10 mm a vs x y vs s b vs y

23. FRIB separator ray plots: Order 3 x vs s ±100 mrad vs ±10 mm a vs x y vs s b vs y

24. FRIB separator ray plots: Order 5 x vs s ±100 mrad vs ±10 mm a vs x y vs s b vs y