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September 12, 2013 PSTP 2013

Polarization optimization studying in the RHIC OPPIS. 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. September 12, 2013 PSTP 2013.

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September 12, 2013 PSTP 2013

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  1. Polarization optimization studying in the RHIC OPPIS G. Atoiana*,V. Klenovb,J. Rittera, D. Steskia, A. Zelenskia, V. Zubetsb aBrookhaven National Laboratory, Upton, NY 11973, USA bInstitute of Nuclear Researches, Moscow, Russia September 12, 2013 PSTP 2013

  2. In Run-13 the upgraded polarized proton source was used 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. G.Atoian

  3. Polarization transfer technique Polarized light Polarized electron Polarized proton (Quarks? Gluons ? Sea quarks? 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 Ionization of hydrogen atoms by capture of second electron in Na-jet for acceleration G.Atoian

  4. OPPIS with FABS-injector layout (Run-13) • OPPIS produces 3-5mA polarized H- ion pulse current • Polarization at 200MeV polarimeter ~81-84 % TMP2 TMP1 4-grids extractor (6-8keV) CP3 CP4 CP1 Beam SCS Pump-laser He-cell Ionizer & decelerator CP2 Plasmatron H-injector Neutralizer H-cell Sona- shield Na-jet Ionizer Extractor to 35KeV Rb-cell 5-10mA H- Rb-cell H-cell He-cell Na-jet G.Atoian H+ H0 H+ H0

  5. Low Energy Beam Transport line 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. Variable collimators to improvement of energy separation EL-tandem Is “off” EL-tandem Is “off”. Add Vert. and Horiz. steering LINAC RFG Laser Room Moveable optic prism The LEBT is tuned for 35keV beam Energy transport. SCS New FC FABS EL2-replaced with Quad triplet transformation of the longitudinal to the transverse polarization Probe laser Pump-laser G.Atoian

  6. In FABS-source Inside of the SCS Ionizer & Extractor H+ 7keV >90% 0.72% 2% 40% H0 7keV H- 7keV H2-cell H-39keV H0 7keV Neutralize Na-jet Extr. Ionize Accelerate 32keV 60% He-cell Ionize H+ 7keV He-cell H+ 3keV Decelerate, ΔE=4.0keV 70% Rb-cell H0 3keV Polarization dilution due H0 in the new source Neutralize 8% Na-jet H- 3keV Ionize 3% 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~ 0.01 H- 35keV Extr. Accelerate 32keV G.Atoian

  7. 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-valve • Operating in high magnetic field ~1-3T He-ionizer cell with three-grid energy separation system He-cell He-pulsed valve 3-grid beam Deceleration system G.Atoian

  8. Only a portion of the beam is ionized in the He-cell (~60%) can be further polarized. H0 + He → H+ + He + e- Ionization in He-cell Deceleration by 3-grids system Neutralization in Rb-cell He-cell Rb -cell H+(60%) H+(3keV) H0(3keV) H0(7keV) H0(40%) H0(7keV) H0(7keV) Energy separation a residual un-polarized H0 component -4.1 kV -4.0 kV -3.9 kV -2.4 kV +0.1 kV Polarized part of the beam separates from un-polarized by the bending magnet and collimators. Energy separation is better than 25-30 times. G.Atoian

  9. Depolarization factors P = EH2 ∙ PRb∙ S ∙ BRG∙ ELS∙ EES ∙ ESona∙ Eion ~ 85-90% G.Atoian Total: 0.85 - 0.90

  10. In FABS-source Inside of the SCS Ionizer & Extractor <10% x 0.2=2% (Attenuate due to larger angular divergence ~ 0.2) H2+ 7keV 0.03% 8% H2-cell 20% H0 3.5keV H-3.5keV H-35.5keV H0 3.5keV Neutralize Na-jet Extr. Ionize Accelerate 32keV 80% He-cell Ionize H+ 3.5keV Decelerate (ΔE=4.0keV)  Rejected He-cell 0% Rb-cell 0% Na-jet Ionize 0% Extr. H- 0% Dilution of polarization due H2+ component- 0.03/3 ~ 0.01 Accelerate 32keV G.Atoian

  11. 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. Control the laser parameters Before By quality of the probe-laser pulse Now By measured frequency and line width of pump-laser G.Atoian

  12. We can create a time-chart of frequency and line width and store data for analyzing. Time-chart of frequency of the laser Time-chart of line width G.Atoian

  13. Beam profile out of Linac Polarization profile out of Linac G.Atoian

  14. G.Atoian

  15. G.Atoian

  16. Dilution of polarization due residual gas at Rb thickness ~5*1013 atoms/cm2 (~350mkA) is 3.7/350 < 1.5% P~1/AN*[(IL-0.5iRG)-(IR- 0.5iRG)] / [(IL-0.5iRG)+(IR- 0.5iRG)] P= 1/AN*(IL- IR)/(IL+ IR +iRG) IM=IL+IR+iRG , if IR= a*IL P= 1/AN* (IM-iRG)(1-a) / IM*(1+a)  iRG~3.7mkA iRG~3.7mkA; IL/IR ~0.315 G.Atoian

  17. G.Atoian

  18. Ratio: 3000/30 ~100 31.5 + (7.5 – 4.0) = 35keV He-valve ‘OFF’ He-valve ‘ON’ 27.5 +7.5 =35keV G.Atoian

  19. 2 corr. coils between SCS and Sona-shield H0 Na-jet & Solenoid H- He-cell Rb-cell SC-solenoid Sona-transition with 3 corr. coils in it G.Atoian

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

  21. 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 fine scan LCC scan G.Atoian

  22. G.Atoian

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

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

  25. Summary 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. G.Atoian

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