1. High-Intensity Polarized H - Beam production in Charge-exchange Collisions A.Zelenski, BNL PSTP 2011, September 14, St.Petersburg

2. RHIC: the “Polarized” Collider STAR PHENIX AGS, 24GeV LINAC BOOSTER, 2.5 GeV Pol. H - ion source Spin Rotators 20% Snake Siberian Snakes 200 MeV polarimeter RHIC pC “CNI” polarimeters RHIC Absolute H-jet polarimeter Design goal: P=70%, L max = 1.6  10 32 s -1 cm -2 50 < √s < 500 GeV AGS pC “CNI” polarimeter 5% Snake Polarization facilities at RHIC.

3. Operational Polarized H - Source at RHIC. RHIC OPPIS produces reliably 0.5-1.0mA polarized H - ion current. Polarization at 200 MeV: P = 80-85%. Beam intensity (ion/pulse) routine operation: Source - 10 12 H - /pulse Linac - 5∙10 11 AGS - 1.5-2.0 ∙ 10 11 RHIC - 1.5∙10 11 (protons/bunch). A 29.2 GHz ECR-type source is used for primary proton beam generation. The source was originally developed for dc operation. A ten-fold intensity increase was demonstrated in a pulsed operation by using a very high-brightness Fast Atomic Beam Source instead of the ECR proton source.

4. Polarized beams at RHIC. OPPIS LINAC Booster AGS RHIC 1.7∙10 11 p/bunch 10∙10 11 (maximum 40∙10 11 ) polarized H - /pulse. 5∙10 11 polarized H - /pulse at 200 MeV, P=85-90% 2∙10 11 protons /pulse at 2.3 GeV ~1.5∙10 11 p/bunch, P~60-65% at 100 GeV P ~ 53% at 250 GeV

5. SPIN -TRANSFER POLARIZATION IN PROTON-Rb COLLISIONS. Rb + H+H+ H+H+ Proton source Proton source Laser-795 nm Optical pumping Rb: NL(Rb) ~10 14 cm -2 Sona transition Sona transition Ionizer cell Ionizer cell H-H- Laser beam is a primary source of angular momentum: 10 W (795 nm) 410 19 h /sec 2 A, H 0 equivalent intensity. Supperconducting solenoid 25 кГс 1.5 kG field Charge-exchange collisions:  ~10 -14 cm 2 Na-jet ionizer cell: NL(Na)~ 310 15 cm -2 Electron to proton polarization transfer ECR-29 GHz Н + source Rb +

6. Schematic Layout of the RHIC OPPIS 29.2 GHz ECR proton source 29.2 GHz ECR proton source SCS solenoid Probe laser Na-jet Ionizer cell Na-jet Ionizer cell Pumping laser Cryopumps Sona-transition Rb-cell SCS -solenoid

7. Pulsed OPPIS with the atomic hydrogen injector at INR, Moscow, 1982-1990. The First-Generation. Atomic H injector Helium ionizer cell ~80% ionization efficiency. Lamb-shift polarimeter H - current 0.4mA, P=65%, 1986

8. Hydrogen atomic beam ionization efficiency in the He- cell. 10 keV 80% H 0 + He → H + + He + e

9. OPPIS upgrade with the Fast Atomic Beam Source (FABS). The Third- Generation. He – ionizer cell serves as a proton source in the high magnetic field. H+H+ H0H0 H-H- H0H0 H+H+ The source produces ~ 5.0 A ! (peak) proton current at 5.0 keV. ~ 10 mA H - current, P = 85-90%. ~ 300 mA (high-brightness) unpolarized H - ion current.

10. Feasibility studies with Atomic Beam Injector at TRIUMF, 1997-99. The Second Generation. A pulsed H - ion current of a 10 mA was obtained in 1999.

11. Pulsed OPPIS at TRIUMF, 1997-99. A pulsed H - ion current of a 10 mA was obtained in 1999. Atomic H Injector.

12. Small diameter beam in the FABS. Atomic H 0 injector produces an order of magnitude higher brightness beam. A 5-10 mA H - ion current can be obtained with the smaller, (about 15 mm in diameter) beam. Higher Sona-transition efficiency for the smaller beam radius. Smaller beam emittance : ε n ~ B × R 2

13. The Atomic Hydrogen Injector Collaboration agreement with BINP, Novosibirsk on polarized source upgrade. Contract with BINP, Novosibirsk. Delivery: May, 2011. Two sets of sources and power supplies, local control system. 4- sets of spherical extraction grids (focal length ~150 cm) for polarized source. 2- sets of shorter focal length (~ 50cm) grids for studies of basic limitation of high-brightness H - ion beam production in the charge-exchange process.

14. BINP design for the “Atomic Beam Injector”. Plasmatron 4-grid proton extraction system H2 Neutralization cell ~ 5.0A equivalent H 0 beam

15. Ratio of the target to the emitter current density vs spherical grids focal length. Fig. 8. Ratio of the target current to the emitter current vs focal distance: 1 – without magnetic field, 2 – with magnetic field. 5A, H + → 200mA, H 0 → 16 mA, H -

16. Residual unpolarized H 0 beam component suppression by the energy separation. H + (60%) H 0 (10keV) H 0 (3.0keV) -7.0 kV -7.1 kV -7.0 kV H 0 (10.0keV) He-ionizer cell Rb -cell H 0 (40%) Deceleration H 0 + He → H + + He + e

17. Polarization dilution in the FABS. H 0 (10keV ) H + (10keV) H + (3.0keV) H 0 (3.0keV) H - (3.0keV) H - (35keV) He-cell 60% ? 50% 8.5% 2.7% H 0 (10keV)H - (10keV)H - (42keV) 40%2% 0.8% H + (10keV ) H2-cell 0.8/2.7 =0.3- polarization dilution. 7.0 keV energy separation would allow dilution reduction to less than 0.1%. Deceleration, ΔE = - 7.0 keV Acceleration, - 32 keV 95%

18. Polarization dilution by H 2 + in the FABS. H 0 (5.0keV ) H + (5.0keV) H + (3.0keV) H 0 (3.0keV) H - (3.0keV) H - (35.0keV) He-cell 80% Beam loss at deceleration ? 50% 8.5% 3% H 0 (5.0keV)H - (5.0keV)H - (37keV) 20%6% 0.12% H + 2 (10keV ) H2-cell Deceleration, ΔE=7.0 keV Acceleration, 32 keV ~10% 0.12/3.0 =0.04- polarization dilution. 2.0 keV energy separation reduces dilution to less than 0.4%

19. LEBT upgrades for the Run 2010-11. “Tandem” Einzel Lens A new Spin Rotator Solenoid New stirrers, Buncher, (Quads?)

20. Molecular component suppression by the double Einzel lens in the LEBT. Deepak simulations.

21. Molecular component suppression by the double Einzel lens in the LEBT. Extractor Voltage, kV 1.4 kV ~10-15% beam intensity losses 32.2 +2.8 =35.0 keV Tk 9, current, 200 MeV 2.0 kV

22. Primary proton beam energy (~ 10.0 keV) choice. Higher energy gives higher beam intensity. Lower ionization efficiency in the He-cell (~60%). Larger deceleration (~7.0 keV) after the He-cell is required. H - yield reduction for 10 keV residual unpolarized H 0. Higher energy increases the energy separation efficiency. At least 10 keV energy is required for molecular H 2 + beam component suppression.

23.  Contract with Cryomagnetics, Tennesi.  Delivery: December, 2011.  Higher 30 kG field. Better field shape. Cold iron yoke.  He- re-condenser, low maintenance cost.  Two mode of operations. Atomic beam mode –long flattop.  ECR- mode provides field shape for the conventional ECR-mode operation. A new superconducting solenoid.

24. Magnetic field maps for Oxford Instr. and Toshiba solenoids. Toshiba solenoid Oxford solenoid Bz -field component at the solenoid axis. Z- RF-power input Rb-cell ECR-grids Sona-transition Correction coil

25. A new superconducting solenoid. ECR-mode. Contract with Cryomagnetics, Tennesi. Delivery: May, 2011 30 kG

26. Depolarization caused by spin-orbital (LS) interaction in excited 2P states. ~92% at 20 kG –low limit Most of the H aoms are produced in excited n=2 states. A high magnetic field has to be Applied in the optically-pumped vapor cell to avoid depolarization due to spin-orbital interaction.

27. H - yield vs beam energy ~ 8.4 % at 3.0 keV beam energy

28. An application of conventional “hot-pipe” sodium vapor cell for high-intensity H - ion beam production in charge-exchange collisions is limited by the fast increase of the sodium losses, which are proportional: ~ n 3 / L, where n is vapor density and L- is the cell length. The solution is the Jet-ionizer cell. Sodium-jet ionizer cell

29. Reservoir– operational temperature. Tres. ~500 о С. Nozzle – Tn ~500 о С. Collector- Na-vapor condensation: Tcoll.~120 о С Trap- return line. T ~ 120 – 180 о С. Transversal vapor flow in the N-jet cell. Reduces sodium vapor losses for 3-4 orders of magnitude, which allow the cell aperture increase up to 3.0 cm. Transversal vapor flow in the N-jet cell. Reduces sodium vapor losses for 3-4 orders of magnitude, which allow the cell aperture increase up to 3.0 cm. Nozzle 500deg.C Collector ~150 deg.C Reservoir ~500 deg.C NL ~2·10 15 atoms/cm 2 L ~ 2-3 cm

30. H - beam acceleration to 35 keV at the exit of Na-jet ionizer cell Na-jet cell is isolated and biased to – 32 keV. The H - beam is accelerated in a two-stage acceleration system. -32 kV H - 35 keV -28 keV-15 keV

31. H - beam acceleration to 35 keV at the exit of Na-jet ionizer cell Na-jet cell is isolated and biased to – 32 keV. The H - beam is accelerated in a two-stage acceleration system. -32 kV H - 35 keV -28 keV-15 keV

32. Small diameter beam in the FABS. Atomic H injector produces an order of magnitude higher brightness beam. A 5-10 mA H - ion current can be obtained with the smaller, (about 15 mm in diameter) beam. Higher Sona-transition efficiency for the smaller beam radius. Smaller beam emittance : ε ~ B × R 2 High-brightness source (FABS) will deliver at least 10 times more beam intensity then ECR-proton source within the small ionizer aperture.

33. After Sona-transition upgrade, Run 07 Simulations and field measurements. A new diam. 4.0” Sona-shield A new Correction Coil Optimized positions for shield and CC 97.5% x x x x

34. Polarization vs. ionizer solenoid current with the 12mm collimator. Maximum polarization from the correction coil scans, collim. -12 mm. 160 A ↔1.16 kG, 81.6%, (95.9%) 200 A ↔1.45 kG, 84.9%, (97.0%) 250 A ↔1.81 kG, 88.1%, (98.1%) Expected: Maximum polarization from the correction coil scans, collim. -12 mm. 160 A ↔1.16 kG, 81.6%, (95.9%) 200 A ↔1.45 kG, 84.9%, (97.0%) 250 A ↔1.81 kG, 88.1%, (98.1%) Expected: 23 mm collimator. 200 A ↔1.45 kG, 82.5% (97.0%) 250 A ↔1.81 kG, 84.5% (98.1%) A new ionizer solenoid: 250 A ↔1.98 kG, 90.0% (98.4%) 23 mm collimator. 200 A ↔1.45 kG, 82.5% (97.0%) 250 A ↔1.81 kG, 84.5% (98.1%) A new ionizer solenoid: 250 A ↔1.98 kG, 90.0% (98.4%) Expected

35. Basic limitation on the intensity of H - beam production in the Na-jet cell. According to paper: A.I.Krylov, V.V.Kuznetsov. Fizika Plasmy, 11, p.1508 (1985), influence of secondary plasma on a Na-jet stable operation is determined by parameter : α = Jσ ion / ev 0 where: J - beam current (per cm) of jet-target length; σ ion – cross-section of ionization of atoms of a target, v 0 – atoms velocity in the Jet. Critical value (Jet instability) of α is ~ 0.06. The cross section of charge exchange of protons on sodium atom has value of: 1.2·10 -14 cm 2. The electron capture cross section for hydrogen atoms in Na-jet is of: 5·10 -16 cm 2. The separation of neutralization and H - production cells should allow current density increase to: J ~1.5 A/cm 2, without impact on the Na-jet operation.

36. High- brighthess un-polarized H - ion beam production ~ 300 mA H - ion beam H + 3.0 keV H 2 –gas neutralizer cell H0H0 Na-jet ionizer cell ~ 4.0 A equivalent H 0 current through 2.0 cm (Diameter) Na –jet cell. ε n ~ 0.1π mm mrad

37. A new FABS test bench. TMP for He pumping

38. FABS operation H- current, 12 mA Arc current, 650A Beam energy, 7.0 keV

39. H - ion beam current vs beam energy (within 25 mm ionizer acceptance). H - current, (× 10) H 0 -intensity

40. A new BINP neutral H-injector installed at the test-bench

41. Neutral hydrogen beam intensity profile at 250 cm distance from the source. 20 mm

42. Depolarization factors in the OPPIS. Depol. Factor ProcessEstimate P Rb Rb polarization0.99 SRb polarization spatial distribution0.97-0.99 B H2 Proton neutralization in residual gas. 0.95-0.99 + E LS Depolarization due to spin-orbital interaction. 0.95-0.99 + E S Sona-transition efficiency 0.98-1.00 + E ioniz. Incomplete hyperfine interaction breaking in the ionizer magnetic field. 0.95-0.99 + XPolarization dilution by molecular hydrogen ions in the ECR source. X Total: 0.81-0.95 (0.9/0.8) 4 ~1.6

43. OPPIS current and polarization vs. Rb – cell vapor thickness. 5∙10 13 Rb-cell thickness, atoms/cm^2 X 10 13 Higher ~105 deg Rb cell temperature

44. Summary I Atomic H injector produces an order of magnitude higher brightness beam than present ECR source. A 5-10 mA polarized H - ion current (50-100 mA proton current) can be obtained for the smaller (higher brightness) beam. The basic limitation on the production of the high- intensity (~300 mA), high-brightness unpolarized H - ion beam in charge – exchange collisions will be also studied.

45. Higher polarization is expected with the fast atomic beam source due to: a) elimination of neutralization in residual hydrogen; b) better Sona-transition efficiency for the smaller diameter beam; c) use of higher ionizer field (up to 3.0 kG), while still keeping the beam emittance below 2.0 π mm∙mrad, due to the smaller beam diameter. All these factors combined will further increase polarization in the pulsed OPPIS to over 85%. Summary II

46. LSP Polarization vs. ionizer current.

47. Polarized beams in RHIC. OPPIS LINAC Booster AGS RHIC 2.2∙10 11 p/bunch, P ~65% 6.3∙10 11 (maximum 40∙10 11 ) polarized H - /pulse. 3.6∙10 11 polarized H - /pulse at 200 MeV, P=80-82% 2.5∙10 11 protons /pulse at 2.3 GeV ~1.7∙10 11 p/bunch, P~60-65% at 100GeV P ~ 53% at 250 GeV 200 uA X300us Scraping in Booster