The Jülich Setup for Storage Cell Characterisation

1. The Jülich Setup for Storage Cell Characterisation • by Ralf Engels • JCHP / Institut für Kernphysik, FZ Jülich • 16.07.2019

2. 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

3. 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 atoms PZ = 0.89 ± 0.01 (HFS 1) PZ = -0.96 ± 0.01 (HFS 3) • Lamb-Shift Polarimeter • Storage Cell • M. Mikirtychyants et al.; NIM A 721 (0) 83 (2013)

4. ABS and Lamb-shift polarimeter 6-pole magnet N- rf-transition 6-pole magnet N+

5. Polarized H2 Molecules • Measurements from NIKHEF, IUCF, HERMES show that recombined molecules retain fraction of initial nuclear polarization of atoms! Pm Pa β= Pm = ½ Pa • The HERMES Collaboration; Eur. Phys. J. D 29, 21–26 (2004) • DOI: 10.1140/epjd/e2004-00023-5

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. Pol. Molecules: The Experimental Setup • ISTC Project # 1861 PNPI, FZJ, Uni. Cologne • DFG Project: 436 RUS 113/977/0-1 H2+, D2+ HD+, H3+ p, d

8. The experimental Setup • 500 mm • Superconducting Solenoid • SC wire NiTi+Cu (Ø 0.5 mm) • Nominal current 50 A  B ~ 1 T • Degradation of frozen field ≤ 0.1% per 5 hrs • LHe consumption ~ 8 l/h

9. The experimental Setup • +11 kV • -10 kV • 200 mm • 200 mm • 0 kV • e―-gun and ion optics

10. The Experimental Setup • The Lamb-shift Polarimeter • mI = +1/2 N+1/2 – N-1/2 N+1/2 + N-1/2 P= • mI = -1/2 R. Engels et al., Rev. Sci. Instr. 74 4607 (2003) R. Engels et al., Rev. Sci. Instr. 85 103505 (2014)

11. The experimental Setup • + • The Lamb-shift Polarimeter works for H2 → H2 H2 → → + + H(2S) Rev. Sci. Instr. 85, 103505 (2014)

12. The Wienfiter: Separation of the different Particles Mass 1: Protons [ from hydrogen atoms : H + e -> p + 2e or from molecules: H2 + e -> p + H + 2e ] Mass 2: H2+ ions [ all from H2 molecules H2 + e -> H2+ + 2e (dominant reaction) ] Deuterons [ can be separated from Protons by the Spinfilter ! ] Mass 3: HD+ ions [ from HD molecules only ] (H3+ ions [H2+ + H2 -> H3+ + H]) Mass 4: D2+ ions [ all from D2 molecules ]

13. Lyman-α Spectra Mass 2: Deuterons

14. Lyman-α Spectra Mass 3: HD+ ions

15. Lyman-α Spectra Mass 3: H3+ ions P = - 0.35 Preliminary P = 0.37

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

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

18. The Jülich Setup: We can measure : 1.) The polarization of H, D, H2, D2, and HD in a storage cell. 2.) The recombination rate of hydrogen/deuterium atoms due to the ion beam intensities for mass 1 and 2 (or mass 2 and 4 for deuterium)

19. The Ionisation process

20. 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)

21. Recombination • Storage cell filled with H2 gas with different fluxes

22. Polarized H2 Molecules • Polarization losses of the molecules • A. Abragam: The Principles of Nuclear Magnetism (1961) • Spin Relaxation of H2/D2 Molecules The polarizationlossesduring wall collisiondepend on: • Nuclear Spin I • J = J(T) -> Bc • Magneticfield B in thecell • n • 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 = 5.4 mT • (For T < 200 K -> J=1)

23. Theory

24. Theory

25. Theory Polarization of the Protons produced from Atoms and/or Molecules

26. Experimental results • Measurements on Fomblin Oil (Perfluoropolyether PFPE) • HFS 3 • TCell = 100 K • Pm = -0.87 • Pm = - 0.81 ± 0.02 • n = 174 ± 19 • c = 0.993 ± 0.005 • p • Pm = - 0.84 ± 0.02 • n = 277 ± 31 • + • H • 2 R. Engels et al., Phys. Rev. Lett. 115 113007 (2015)

27. . . Recombination on Fomblin (?) . . Bext . F F F F C - O - C - O - C O --C Fused Quarz

28. The Jülich Setup: We can measure : 1.) The polarization of H, D, H2, D2, and HD in a storage cell. 2.) The recombination rate of hydrogen atoms due to the ion beam intensities for mass 1 and 2 (or mass 2 and 4 for deuterium) and by the polarization measurements of protons and H2+ ions 3.) The influence of different surfaces on the recombination process and the polarization preservation

29. Results on a Nickel Surface Protons Saturation of Nickel at ~0.7 T

30. HD Molecules

31. HD Molecules

32. HD Molecules D H H D Brot Brot First Order Approximation: Distance Brot <-> H increased by 1/3 Distance Brot <-> D decreased by 1/3 Bc ~ Brot / r3 2/3 1/3 H D Brot Bc (H2) Bc (HD) = 2.4 = 3.4

33. The Jülich Setup: We can measure : 1.) The polarization of H, D, H2, D2, and HD in a storage cell. 2.) The recombination rate of hydrogen atoms due to the ion beam intensities for mass 1 and 2 (or mass 2 and 4 for deuterium) and by the polarization measurements of protons and H2+ ions 3.) The influence of different surfaces on the recombination process and the polarization preservation 4.) The coupling strength of the rotational magnetic moment J and the nuclear spins I - the number of wall collisions n

34. Conclusion: • Limitations: • - Temperaturerange: 40 – 120 K • (roomtemperature not possible) • Cell design fixed (Quartzcell: 400 mm long, inner • diameter 10 mm, outerdiameter 14 mm) Who can cover such a cell inside with carbon ?

35. Conclusion We can produce polarized H2, D2 and HD molecules with large vector- and tensor-polarization (~ 0.8) in many spin combinations. For what it is usefull? 1.) More dense polarized targets (?). 2.) Spectroscopy of the molecules or molecular ions (Contact with the University of Düsseldorf). 3.) New insights in chemical reactions / surface physics. 4.) Polarized fuel to increase the energy output of Fusion reactors. 5.) Polarized targets for laser acceleration. 6.) EDM measurements ? • 7.) An option to produce polarized molecules for medical application ?