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Production of polarized ions in nearly resonant charge-exchange collisions in plasma

Production of polarized ions in nearly resonant charge-exchange collisions in plasma. A. S. Belov Institute for Nuclear Research of Russian Academy of Sciences Moscow, Russia. The report is summary of work performed in collaboration with several laboratories since 1980th: INR, Moscow:

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Production of polarized ions in nearly resonant charge-exchange collisions in plasma

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  1. Production of polarized ions in nearly resonant charge-exchange collisions in plasma A. S. Belov Institute for Nuclear Research of Russian Academy of Sciences Moscow, Russia A.S. Belov, PSTP-2007, BNL, USA

  2. The report is summary of work performed in collaboration with several laboratories since 1980th: • INR, Moscow: S. K. Esin, V. E. Kuzik , S. A. Kubalov , L. P. Netchaeva , A. V. Turbabin , G. A. Vasil’ev , V. P. Yakushev • Novosibirsk Budker Institute of Nuclear Physics V. G. Dudnikov • IUCF, Bloomington V. P. Derenchuk A.S. Belov, PSTP-2007, BNL, USA

  3. Content: • Introduction • Nearly resonant charge-exchange reactions, cross-sections • Polarized H+/ D+ source • with free atomic hydrogen beam • with storage cell in a charge-exchange region • Source of polarized H/ D ions • Scheme of source for polarized 3He ++ ions • Pulsed atomic hydrogen beam study • Conclusions A.S. Belov, PSTP-2007, BNL, USA

  4. Introduction • Polarized ions are produced in polarized ion sources via several steps process: • polarization of neutral atoms (atomic beam method or optical pumping) • Conversion of polarized neutral atoms into polarized ions (ionization byelectron impact, electron impact + charge-exchange, charge exchange, nearly resonant charge-exchange ) • Nearly resonant charge-exchange processes have large cross sections. This is base for high efficiency of polarized atoms conversion into polarized ions. A.S. Belov, PSTP-2007, BNL, USA

  5. Resonant charge-exchange reaction is charge exchange between atom and ion of the same atom: A0 + A+  A+ + A0 • cross -section is of order of 10-14 cm2 at low collision energy • Charge-exchange between polarized atoms and ions of isotope relative the polarized atoms - to reduce unpolarized background • W. Haeberli proposed in 1968 an ionizer with colliding beams of ~1-2 keV D- ions and thermal polarized hydrogen atoms: H0 + DH + D 0 A.S. Belov, PSTP-2007, BNL, USA

  6. Nearly resonant charge-exchange reactions which can be used for polarized ion sources H0 + D+ H+ + D 0 D0 + H+ D+ + H0 H0 + DH + D 0 D0 + HD + H 0 3He0 + 4He+3He+ + 4He 0 3He0 + 4He++3He++ + 4He 0 T+, T-, Li+… A.S. Belov, PSTP-2007, BNL, USA

  7. Cross-section vs collision energy for process H+ + H0 H0 + H+ =510-15 cm2 at ~10eV collision energy A.S. Belov, PSTP-2007, BNL, USA

  8. Cross-section vs collision energy for process H+ H0 H0 + H =10-14 cm2 at ~10eV collision energy A.S. Belov, PSTP-2007, BNL, USA

  9. Cross-section vs collision energy for process He++ + He0 He0 + He++ =510-16 cm2 at ~10eV collision energy A.S. Belov, PSTP-2007, BNL, USA

  10. Low collision energy is achieved if ions are in plasma with ion temperature in eV region. • Space charge problem for transport of intense ion beam to charge-exchange region is eliminated if plasma is used • V. Nizhegorodtsev and V. Sokolov from IHEP, Russia proposed use of plasma from ion source for ionization of polarized atoms in 1971 • INR group in 1984 designed source of polarized protons with nearly resonant charge-exchange in plasma : synthesis of ideas of W. Haeberli and V. Nizhegorodtsev and V. Sokolov A.S. Belov, PSTP-2007, BNL, USA

  11. Scheme of polarized hydrogen ion source with nearly resonant charge-exchange plasma ionizer (INR , 1984) A.S. Belov, PSTP-2007, BNL, USA

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  13. Characteristics the INR polarized proton source • ABS: • peak intensity of polarized atomic hydrogen beam is 2 1017at/s • most probable velocity is 2 105 cm/s • Polarized proton beam: • peak current is 6 mA • polarization - 75-90 % • normalized emittance 2 mm mrad • rep. rate up to 10 Hz • Unpolarized deutron current density - 250 mA/cm2 A.S. Belov, PSTP-2007, BNL, USA

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  16. Storage cell in the charge-exchange region • Storage cell as a donor of polarized electrons in a polarized ion source - W. Haeberli, 1966 • Storage cell in a plasma ionizer of polarized ion source - V. Nizhegorodtsev and V. Sokolov, 1971 • Storage cell in colliding beam ionizer for polarized H- ion production - T. Clegg, 1995 A.S. Belov, PSTP-2007, BNL, USA

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  19. Intensity of polarized proton beam increased ~9 times due to storage cell.  • With 5 mA D+ ion current - 1 mA of H+ current • With 40 mA unpolarized D+ ion current in the storage cell - 8 mA of polarized proton current  • 50 mA of D+ ion current l - 11 mA polarized proton current has been obtained A.S. Belov, PSTP-2007, BNL, USA

  20. Proton polarization up to 95 % was measured with low plasma ion flux (5mA D+)  • Polarization of 80% has been recorded for high ion flux in the storage cell  A.S. Belov, PSTP-2007, BNL, USA

  21. Polarized deutron source for Dubna NUCLOTRON accelerator • New source with nearly resonant charge-exchange ionizer is developed • Project goal: • 10 mA D+ (Н+) • polarization ~ 90 % from nominal vector polarization + (-) 1 and tensor polarization + 1,-2 • Parts of CIPIOS source from IUCF (Bloomington, USA) will be used. Collaboration between JINR (Dubna) and INR of RAS (Troitsk). • Storage cell is planned to be used to reduce background current of H2+ ions A.S. Belov, PSTP-2007, BNL, USA

  22. Polarized negative hydrogen ion source • In order to produce polarized negative hydrogen ions it was necessary to have deuterium plasma consisting mainly from D+ and D- ions because slow polarized H- ions can be easily destroyed in collisions with plasma electrons • Plasma injector producing deuterium plasma enriched by D- ions with surface-plasma converter has been developed at INR A.S. Belov, PSTP-2007, BNL, USA

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  25. Expected H- ion current: • where IH0 = 21017 s-1 is intensity of the atomic hydrogen beam A.S. Belov, PSTP-2007, BNL, USA

  26. Destruction of negative hydrogen ions in plasma • H+ e  H0 + 2e  ~ 410-15 cm2 • H+ D+ H0 + D0  ~ 210-14 cm2 • H+ D0 H0 + D   ~ 10-14 cm2 • H+ D2 H0 + D2+ e  ~ 210-16 cm2 • H+ D0 HD0 + e  ~ 10-15 cm2 A.S. Belov, PSTP-2007, BNL, USA

  27. Oscillograms of polarized H- ion current(vertical scale-1mA/div) and unpolarized D- ion current(10mA/div) A.S. Belov, PSTP-2007, BNL, USA

  28. Characteristics of polarized H- ion beamof the INR source • Peak H- ion current 4 mA • Polarization 0.910.03 • Normalized emittance 2  mm mrad • Unpolarized D- ion current 60 mA (~20 mA/cm2) • Pulse duration (FWHM) 170 s • Rep. rate 5 Hz Source of polarized and unpolarized H-/D- ions of IUCF • Peak current of H-/D- ions 2 mA • Polarization up to 0.9 from nominal • Normalized emittance 1.2  mm mrad • Unpolarized H-/D- ion current 40/30 mA • Pulse duration up to 500 s • Rep. rate 2 Hz A.S. Belov, PSTP-2007, BNL, USA

  29. Schematic diagram of proposed polarized 3He++ ion source3He0 + 4He++3He++ + 4He 0 A.S. Belov, PSTP-2007, BNL, USA

  30. Study of polarized pulsed atomic hydrogen beam A.S. Belov, PSTP-2007, BNL, USA

  31. Time-of-flight mass-spectrometer with cross-beam ionizer A.S. Belov, PSTP-2007, BNL, USA

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  35. Beam-skimmer interference • Density of pulsed atomic hydrogen beam decreases with decrease of the nozzle-skimmer distance while simulation (which does not take into account scattering of atoms) forecasts increase of density  • Explanation: atomic beam forms gas “cloud” inside the skimmer and atomic beam attenuates due to scattering : beam-skimmer intereference A.S. Belov, PSTP-2007, BNL, USA

  36. Beam-skimmer interference simulation • When atomic beam passes through volume with restricted conductance - instability can arise for formation of gas “cloud” and attenuation of the beam A.S. Belov, PSTP-2007, BNL, USA

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  39. Noncomplete cooling of atomic hydrogen in nozzle at high gas densities A.S. Belov, PSTP-2007, BNL, USA

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  42. Conclusions • Polarized H+/D+ ion beam with peak current ~ 10 mA as well as H-/D- with current 4 mA and polarization of ~90% from nominal have been produced by atomic-beam type polarized ion source with nearly resonant charge-exchange plasma ionizer. • Generation of polarized 3He++ with high intensity and polarization seems to be possible using similar method. • Intensity of pulsed polarized atomic hydrogen beam is restricted by noncomplete cooling of atoms and scattering of atoms presumably in nozzle chamber. A.S. Belov, PSTP-2007, BNL, USA

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