Polarized Deuterium/Hydrogen Molecules in Nuclear Fusion: Key Questions and Discoveries

1. on the LEAP conference Polarized Deuterium/Hydrogen Molecules Possible Fuel for Nuclear Fusion Reactors? • by Ralf Engels • JCHP / Institut für Kernphysik, FZ Jülich • 14.11.2013

2. Important Questions for Polarized Fusion • Can the total crosssectionsofthefusionreactionsbe increasedbyuseofpolarizedparticles? (See talksbyPaetz gen. Schieck, Deltuva, Kravchenko, Kravtsov) • Will polarizationsurvive in a plasma? (See talksby Holler andDidelez) • What will happen in the different typesoffusionreactors? (See talksby Temporal andSandorfi) • Howtogetandhowto handle polarizedfuel?

3. p, p, d, d with momenta up to 3.7 GeV/c PIT@ANKE • internal experiments – with the circulating beam • external experiments – with the extracted beam

4. PIT @ ANKE/COSY Main parts of a PIT: • Atomic Beam Source • Target gas hydrogenordeuterium • H beam intensity (2 hyperfine states) 8.2 . 1016 atoms / s • Beam size at the interaction point σ = 2.85 ± 0.42 mm • Polarization for hydrogen atom PZ = 0.89 ± 0.01 (HFS 1) PZ = -0.96 ± 0.01 (HFS 3) • Polarization for deuterium atoms atom PZ = 0.88 / PZZ = 0.88 (HFS 1/6) PZ = 0.005 / PZZ = -1.71 (HFS 2/5) • Lamb-Shift Polarimeter • Storage Cell • M. Mikirtychyants et al.; NIM A 721 (0) 83 (2013)

5. ABS and Lamb-shift polarimeter 6-pole magnet rf-transition 6-pole magnet

6. Polarized H2 Molecules • Eley-Rideal Mechanism • Pm = 0.5 • Pa • Is there a way to increase Pm P • (surface material, T, B etc)?

7. Polarized H2 Molecules • Measurements from NIKHEF, IUCF, HERMES show that recombined molecules retain a fraction of initial nuclear polarization of atoms! • The HERMES Collaboration; Eur. Phys. J. D 29, 21–26 (2004) • DOI: 10.1140/epjd/e2004-00023-5

8. Theory Abragam: The PrinciplesofNuclearMagnetism Hamiltoniantodescribethenuclearspinrelaxationof H2molecules H = ωI ( I1z + I2z) + ωJJz + ω‘ (I1 + I2)·J + ω‘‘ { I1· I2– 3(I1· n)(I2 · n)} I1andI2arethespinsofthetwoprotons I1 + I2 = I J istherotational angular momentumofthemolecule ωI = - γI H0istheprotonLamorfrequency in theappliedfield H0 ωJ = - γJ H0istheLamorfrequencyoftherotationalmagneticmomentofthe H2 ω‘ = - γI H‘ isthestrengthofthecouplingbetweenthemagneticmomentofthe protonsandthemagneticfieldproducedattheirpositionsbythe rotationofthemolecule ( H‘ = 2.7 mT) ω‘‘ = 2 γI H‘‘ = γI2 ħ/ b3isthestrengthofthedipolarcouplingbetweentheprotons, b istheirdistance, andnistheunitvectorb/b (H‘‘ = 3.4 mT). • Bc (Hz) ≠ Bc (Dz) ≠ Bc (Dzz)

9. Polarized H2 Molecules • Polarization losses of the molecules • A. Abragam: The Principles of Nuclear Magnetism (1961) • Spin Relaxation of H2/D2 Molecules The polarizationlossesduring a single wall collisiondepend on: • Nuclear Spin I • PolarizationPm • Temperature • Magneticfield in thecell • n ≈ 1000 • 2 • Bc • ( ) • - n • B • P(B,n) = Pm · e • Nuclear Polarization of Hydrogen Molecules from • Recombination of Polarized Atoms • T.Wise et al., Phys. Rev. Lett. 87, 042701 (2001). • Bc = 6.1 mT

10. The idea • B ~ 1T • polarized • cell wall • Recombination of polarized atoms • into molecules • Conversion of polarized atoms and • molecules into ions • Separation of protons and H2 by • energy with the Wienfilter • Measurement of proton and H2 • polarization in LSP • + • +

11. The Setup • ISTC Project # 1861 PNPI, FZJ, Uni. Cologne • DFG Project: 436 RUS 113/977/0-1

12. The Ionization Processes • + • H + e → H + 2e • (Ee = 150 eV: σ = 0.46 · 10-16 cm2) • (www.nist.gov) • + • H2 + e → H2 + 2e • (Ee = 150 eV: σ = 0.88 · 10-16 cm2) • + • H2 + e → H + 2e + … • (Ee = 150 eV: σ = 0.082 · 10-16 cm2)

13. Experimental results • Mass separation with the Wienfilter • Fel = FB • E • q = - q • v • B

14. Recombination

15. Experimental results • Wienfilter function of the protons in the LSP • Ekin(p) = 1 keV

16. Experimental results • + • Wienfilter function of the H2 ions in the LSP

17. Experimental results • + • How are the polarized H2S produced from H2? • 2-step process (Stripping at the Cs + H2S production) • + • 1-step process: Direct production: H2 + Cs → H2S + Cs+… • Cross section: • σ(p→H2S) ≈ 35·σ(H2→H2S) • +

18. Theory + H2 Pm = 0.5 Bc = 6.1 mT

19. Theory

20. Theory

21. Experimental results • Protons: • See Talk by A. Nass on Friday

22. Experimental results • Polarization of the Protons • (HFS 1, Ep = 4 keV, Gold Surface, B=0.28 T) • 0.6 • 0.5 • 0.4 • 0.3 • 0.2 • 0.1 • 0

23. Experimental results • Measurements on Fomblin (Perfluorpolyether PFPE) • HFS 3 • TCell = 100 K • Protons: • Pm = - 0.81 ± 0.02 • n = 136 ± 15 • c = 0.993 ± 0.005 • + • H2 : • Pm = - 0.84 ± 0.02 • n = 217 ± 24

24. Experimental results • J.S. Price and W. Haeberli, • “Measurement of cell wall • depolarization of polarized • hydrogen gas targets in a weak • magnetic field” • Nuclear Instruments and Methods • in Physics Research A 349 (1994) • 321-333

25. Experimental results • Measurements on Fomblin Oil (Perfluorpolyether PFPE) • HFS 3: Next day • TCell = 100 K • Protons: • Pm = - 0.80 ± 0.02 • n = 336 ± 104 • c = 0.526 ± 0.015 • Pa = - 0.80 ± 0.02 • + • H2 : • Pm = - 0.80 ± 0.02 • n = 110 ± 47

26. Experimental results • Measurements on Fomblin (Perfluorpolyether PFPE) • HFS 2+3: Next day • TCell = 100 K • Protons: • Pm = - 0.68 ± 0.02 • n = 409 ± 87 • c = 0.88 ± 0.02 • Pa = -0.68 ± 0.02 • + • H2 : • Pm = - 0.68 ± 0.02 • n = 184 ± 29

27. Experimental results • Measurements on Fomblin (Perfluorpolyether PFPE) • + • Bcell = 0.4 T , H2 only • HFS 3 • HFS 2+3

28. Experimental results • Very first results on water (Fomblin): (3. day) • p • HFS3 • Very Preliminary • + • H2

29. Experimental results • Very first results on water (Gold): Tcell = 100 K • Pm = 0.28 ±0.01 • n = 317 ± 16 • Pm = - 0.25 ±0.01 • n = 330 ± 26 • Pm = - 0.27 ±0.01 • n = 605 ± 27 • -0,44

30. Experimental results • Measurements on Fused Quartz Glass after several days • Deuterium: HFS 3+4 (Vector and Tensorpolarized) • (Pa,z = - 0.91 ± 0.01 / Pa,zz = + 0.85 ± 0.02) • TCell = 100 K • Pm,zz = 0.24 ± 0.03 • n = 1590 ± 590 • c = 0.980 ± 0.006 • Pm,zz = 0.24 ± 0.03 • n = 950 ± 246 • Pm,z = - 0.40 ±0.01 • n = 701 ± 180 • c = 0.984 ± 0.008 • Pm,z = - 0.40 ±0.01 • n = 686 ± 75

31. Conclusion Wecanmeasure: • therecombinationof hydrogen/deuteriumatoms on different surfacesandfor different HFS. • thepolarizationofatomsandmoleculesin a storagecell. • thenumberofwall collisionsofthemolecules in thecell. At least, wecanseethedifferencebetween „hard“ and „soft“ materials(elasticscatteringorcosx-distribution). • theBcforvector- andtensor-polarizedDeuterium. • Wecanincreasethetargetdensitywithrecombinedmolecules. => Bc (Dz) = 7 ±1 mT / Bc (Dzz) = 10 ±1 mT

32. To-do List • CalculationofBcforvector- andtensor-polarized Deuterium - Additional cryo-catcherbetween ABS and ISTC-chamber • Measurements on different surfaces: - Aluminium - Teflon - … • More measurements on a watersurface (Maybethesurfacebelowhassomeinfluence …) • Development of a newopenablestoragecellfor ANKE • Polarized Deuterium Fuel forpolarizedfusionreactors

33. Polarized H2 Molecules para-Deuterium • - orto-Deuterium