September 12, 2013 PSTP 2013 G. Atoian a *, V. Klenov b, J. Ritter a, D. Steski a, A. Zelenski a, V. Zubets b a Brookhaven National Laboratory, Upton, NY 11973, USA b Institute of Nuclear Researches, Moscow, Russia Polarization optimization studying in the RHIC OPPIS

OPPIS (Optically Pumped Polarized Ion Source) H - ion source had been upgraded to a higher intensity and polarization. Up until Run-13 a ECR-type source was used for primary proton beam generation. The source was originally developed for DC operation and placed inside of the super conductive solenoid (SCS). A tenfold intensity increase was demonstrated in pulsed operation by using a high-brightness Fast Atomic Beam Source (FABS) instead of the ECR proton source. FABS was developed at Budker Institute of Nuclear Physics (BINP), Novosibirsk to improve the source parameters such as beam current density, angular divergence, and stability. In Run-13 the upgraded polarized proton source was used 9/12/2013G.Atoian 2

Production of circular polarized tunable wavelength (~795nm) laser beam Polarization transfer from laser beam to electron in Rb atoms by optical pumping technique Production of electron spin polarized hydrogen atoms when protons capture polarized electrons from Rb atoms Polarization transfer from electron to proton by “Sona- transition” technique Polarization transfer technique Ionization of hydrogen atoms by capture of second electron in Na-jet for acceleration Polarized light Polarized electron Polarized proton (Quarks? Gluons ? Sea quarks? 9/12/2013G.Atoian 3

Plasmatron H-injector Neutralizer H-cell He-cell Ionizer & decelerator Rb-cell Na-jet Ionizer H+H+ H0H0 H+H+ H0H0 5-10mA H - H-cellHe-cell Rb-cell Na-jet TMP1 CP2 CP4CP3 CP1 TMP2 SCS Sona- shield Extractor to 35KeV OPPIS with FABS-injector layout (Run-13)  OPPIS produces 3-5mA polarized H - ion pulse current  Polarization at 200MeV polarimeter ~81-84 % 4-grids extractor (6-8keV) Pump -laser Beam 9/12/2013G.Atoian 4

Low Energy Beam Transport line EL-tandem Is “off” EL2-replaced with Quad triplet Variable collimators to improvement of energy separation New FC The LEBT is tuned for 35keV beam Energy transport. Add Vert. and Horiz. steering EL-tandem Is “off”. Laser Room Moveable optic prism Pump-laser Probe laser The entire LEBT line has been modified for: an additional space for the new source (more then 1.5m); to transport more intense beam; energy separation of polarized component of the beam. 9/12/2013G.Atoian 5 transformation of the longitudinal to the transverse polarization RFG LINAC FABS SCS

Polarization dilution due H 0 in the new source Ionize H 0 7keV 40% Rb-cell 60% He-cell H 2 -cell Neutralize In FABS-sourceInside of the SCS Ionizer & Extractor H - 39keV 0.72% Accelerate 32keV 3% H - 7keV Na-jet 8% Decelerate, ΔE=4.0keV He-cell 70% 2% Na-jet >90% Ionize Extr. Accelerate 32keV Extr. Ionize H 0 7keV H + 7keV H + 7keV H + 3keV Neutralize H 0 3keV H - 3keV H - 35keV Dilution of polarization (0.72/3 =0.24) can be reduced by the energy separation of the H - beam (~25-30 times) to 0.24/25~ /12/2013G.Atoian 6

Two functions of the new He-cell with pulsed valve: Ionization of the injected neutral beam Deceleration of the ionized part of the beam to separate from the no-ionized part He-ionizer cell with three-grid energy separation system He-valve  Operating in high magnetic field ~1-3T He-pulsed valve 3-grid beam Deceleration system He-cell 9/12/2013G.Atoian 7

Energy separation a residual un-polarized H 0 component H + (60%) H 0 (7keV) -4.0 kV-4.1 kV-2.4 kV H 0 (7keV) He-cellRb -cell H 0 (40%) Deceleration by 3-grids system H 0 + He → H + + He + e - H 0 (3keV) +0.1 kV-3.9 kV H + (3keV) H 0 (7keV) Ionization in He-cell Neutralization in Rb-cell Only a portion of the beam is ionized in the He-cell (~60%) can be further polarized. Polarized part of the beam separates from un-polarized by the bending magnet and collimators. Energy separation is better than times. 9/12/2013G.Atoian 8

Total: P = E H2 ∙ P Rb ∙ S ∙ B RG ∙ E LS ∙ E ES ∙ E Sona ∙ E ion ~ 85-90% Depolarization factors Depol. factorProcessEstimate 1E H2 Dilution due H 2 + in the new source (LEBT) P Rb Rb-optical pumping (Laser system) SRb polarization spatial distribution (Collimators) B RG Proton neutralization in residual gas (Vacuum) E LS Depolarization due to spin-orbital interaction E ES Dilution due to incomplete energy separation not polarized component of the beam (LEBT) E Sona Sona-transition efficiency (Adjustment) E ion Incomplete hyperfine interaction breaking in the ionizer magnetic field /12/2013G.Atoian 9

Dilution of polarization due H 2 + component- 0.03/3 ~ 0.01 Ionize H 0 3.5keV 20% Rb-cell 80% He-cell H 2 + 7keV H 2 -cell Neutralize In FABS-sourceInside of the SCS H keV 0.03% Accelerate 32keV H-H- 0% H - 3.5keV Na-jet 0% Decelerate (ΔE=4.0keV)  Rejected He-cell 0% 8% Na-jet <10% x 0.2=2% (Attenuate due to larger angular divergence ~ 0.2) Ionize Extr. Accelerate 32keV Extr. Ionize Ionizer & Extractor H 0 3.5keV H + 3.5keV 9/12/2013G.Atoian 10 1E H2 Dilution due H 2 + in the new source (LEBT)

Polarization strongly depends on the power, frequency, and the line width of the pumping laser. After upgrade a laser system we: adjust of power, frequency, and line width of pumping laser; monitor and control frequency, and line width with new wave-meter. Before By quality of the probe-laser pulse Now By measured frequency and line width of pump-laser Control the laser parameters 9/12/2013G.Atoian 11 2P Rb Rb-optical pumping (Laser system)

Time-chart of line width Time-chart of frequency of the laser We can create a time-chart of frequency and line width and store data for analyzing. 9/12/2013G.Atoian 12 2P Rb Rb-optical pumping (Laser system)

3SRb polarization spatial distribution (Collimators) /12/2013G.Atoian 13 Beam profile out of LinacPolarization profile out of Linac

3SRb polarization spatial distribution (Collimators) /12/2013G.Atoian 14

4B RG Proton neutralization in residual gas (Vacuum) /12/2013G.Atoian 15

4B RG Proton neutralization in residual gas (Vacuum) /12/2013G.Atoian 16 P~1/A N *[(I L -0.5i RG )-(I R - 0.5i RG )] / [(I L -0.5i RG )+(I R - 0.5i RG )] P= 1/A N *(I L - I R )/(I L + I R +i RG ) I M =I L +I R +i RG, if I R = a*I L P= 1/A N * (I M -i RG )(1-a) / I M *(1+a)  i RG ~3.7mkA Dilution of polarization due residual gas at Rb thickness ~5*10 13 atoms/cm 2 (~350mkA) is 3.7/350 < 1.5% i RG ~3.7mkA; I L /I R ~0.315

5E LS Depolarization due to spin-orbital interaction /12/2013G.Atoian 17

(7.5 – 4.0) = 35keV Ratio: 3000/30 ~ =35keV 6E ES Dilution due to incomplete energy separation not polarized component of the beam (LEBT) /12/2013G.Atoian 18 He-valve ‘OFF’ He-valve ‘ON’

He-cellRb-cell SC-solenoid Sona-transition with 3 corr. coils in it Na-jet & Solenoid 2 corr. coils between SCS and Sona-shield H0H0 H-H- 9/12/2013G.Atoian 19 7E Sona Sona-transition efficiency (Adjustment)

9/12/2013G.Atoian 20 7E Sona Sona-transition efficiency (Adjustment) ICC-2 ICC-3ICC-1 5 correction coils (LCC, SCC, ICC1, ICC2 and ICC3) used for optimized magnetic field in Sona-shield to achieve maximum polarization. No adiabatic passage to weak field region Spin rotator region Sona transition region Sona shield

9/12/2013G.Atoian 21 7E Sona Sona-transition efficiency (Adjustment) For maximum polarization must be accurate selection of settings all correction coils. Any change in the magnetic field of coils, SCS or ionizer as well as their position requires a new settings. LCC scan LCC fine scan

9/12/2013G.Atoian 22 8E ion Incomplete hyperfine interaction breaking in the ionizer magnetic field

Beam performance during RHIC fill #17472 (May 7, 2013) 9/12/2013G.Atoian 23

T(Rb)=81  C, I(T9)=295mkA (4.9*10^11) 83.9+/0.7% 84.2+/-0.5% 15 min 9/12/2013G.Atoian 24

Polarization is an average about 2-3% higher than ECR- based source. It is expected that polarization can be further improved to 85%. Higher polarization is expected due to reduce depolarization factors: Rb polarization spatial distribution; reduce residual gas; Sona-transition efficiency; incomplete energy separation and Incomplete hyperfine interaction breaking in the ionizer magnetic field. Summary 9/12/2013G.Atoian 25