RHIC polarized source upgrade A Zelenski BNL Workshop
RHIC polarized source upgrade. A. Zelenski, BNL
Workshop on high–energy spin physics, IHEP, Protvino, September 1983 Yaroslav Derbenev “Siberian snakes” Anatoli Zelenski A new polarization technique. Equal intensity for polarized and unpolarized proton beams.
Polarization facilities at RHIC. Design goal - L -1 cm-2 50 < √s < 500 Ge. V = 1. 6 the 1032 s“Polarized” RHIC: Collider max RHIC p. C “CNI” polarimeters Absolute H-jet polarimeter PHENIX RHIC STAR Siberian Snakes Spin Rotators 5% Snake Pol. H- ion source LINAC AGS, 24 Ge. V 200 Me. V polarimeter BOOSTER, 2. 5 Ge. V AGS p. C “CNI” polarimeter 20% Snake
Operational Polarized H- Source at RHIC OPPIS produces reliably 0. 5 -1. 0 m. A polarized H- ion current. Polarization at 200 Me. V: P = 80%. Beam intensity (ion/pulse) routine operation: Source - 1012 H-/pulse Linac - 5∙ 1011 AGS - 1. 5 -2. 0 ∙ 1011 RHIC - 1. 5∙ 1011 (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.
SPIN -TRANSFER POLARIZATION IN PROTON-Rb COLLISIONS. Laser-795 nm Optical pumping Rb: NL(Rb) ~1014 cm-2 Rb+ Proton source Na-jet ionizer cell: NL(Na)~ 3 • 1015 cm-2 Rb+ H+ H+ Sona transition Ionizer cell H- 1. 5 k. G field ECR-29 GHz Н+ source Supperconducting solenoid 25 к. Гс Charge-exchange collisions: ~10 -14 cm 2 Electron to proton polarization transfer Laser beam is a primary source of angular momentum: 10 W (795 nm) 4 • 1019 h /sec 2 A, H 0 equivalent intensity.
Schematic layout of the RHIC OPPIS. Cryopumps SCS solenoid SCS -solenoid Rb-cell Probe laser Pumping laser 29. 2 GHz ECR proton source Na-jet Ionizer cell Sona-transition
Pulsed OPPIS with the atomic hydrogen injector at INR, Moscow, 1982 -1990. First generation. Atomic H injector Helium ionizer cell ~80% ionization efficiency. H- current 0. 4 m. A, P=65% Lamb-shift polarimeter
Pulsed OPPIS at TRIUMF, 1997 -99. Second generation. Atomic H Injector. A pulsed H- ion current of a 10 m. A was obtained in 19
OPPIS with atomic H injector layout. RHIC 2012. The third generation.
OPPIS with atomic H injector layout. CP 1 TMP 1 Neutralizer cell Atomic H injector H+ H 2 He-ionizer cell H 0 He Na-jet cell Rb-cell H+ Rb H 0 Na H-
Hydrogen atomic beam ionization efficiency in the He- cell. H 0 + He → H+ + He + e 80% 10 ke. V
H- yield vs beam energy ~ 8. 4 % at 3. 0 ke. V beam energy
A result of this “upgrade” is practically a new source. • • • A new superconducting solenoid. A new atomic hydrogen injector. A new vacuum system. A new H-ionizer cell, energy separation system and pulsed PS system. A new control and interlock system. Major upgrades of laser system. Major modifications of the Low Energy Beam Transport system. Major upgrades in 200 Me. V polarimeter. A new test-bench for atomic injector studies. Many other upgrades…
“Fast Atomic Beam Source”, BINP 2011 Plasmatron 4 -grid proton extraction system ~ 3. 5 A equivalent H 0 beam H 2 Neutralization cell FABS produces 200 -300 m. A equivalent H 0 beam intensity Within the Na-jet ionizer acceptance.
FABS and neutralizer cell.
FABS 4 -grid spherical Ion Optical System (IOS).
OPPIS magnetic field, Sona-transition field shape control. Internal Correction Coils Superconducting Solenoid Large Correction Coil Sona transition Ionizer solenoid
Atomic Beam Mode, flattop. 65 cm flattop 30 k. G
He-ionizer cell and three-grid energy separation system. He-pulsed valve 3 -grid beam deceleration system
Sodium-jet ionizer cell 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 500 deg. C Collector ~150 deg. C NL ~2· 1015 atoms/cm 2 L ~ 2 -3 cm Reservoir ~500 deg. C 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.
H- beam acceleration to 35 ke. V at the exit of Na-jet ionizer cell H 35 ke. V -32 k. V -28 ke. V -15 ke. V Na-jet cell is isolated and biased to – 32 ke. V. The H- beam is accelerated in a two-stage acceleration system.
H- beam acceleration to 35 ke. V at the exit of Na-jet ionizer cell H 35 ke. V -32 k. V -28 ke. V -15 ke. V Na-jet cell is isolated and biased to – 32 ke. V. The H- beam is accelerated in a two-stage acceleration system.
New PLC interlock and monitoring system. Graphics by Yuri Bezpalko
H- ion beam current pulse -560 u. A at 200 Me. V, Rb-96 deg, May 3, 2013 H- ion beam current-700 u. A at injection to RFQ
Polarized injector, 200 Me. V linac and injection lines. Polarization direction is adjusted vertically in the 750 ke. V beamline by the solenoidal spin rotator. 200 Me. V polarimeter OPPIS
Source intensity and polarization. • Reliable long-term ∙operation of the source was demonstrated. • Very high suppression of un-polarized beam component was demonstrated. • Small beam emittance (after collimation for energy separation) and high transmission to 200 Me. V. Rb-cell, Temp. , deg. C 81 Linac Current, μA 295 86 370 91 430 96 570 Booster Input × 1011 4. 9 6. 2 7. 3 9. 0 Pol. %, at 200 Me. V 84 83 80. 5 78
H- beam current and polarization at 200 Me. V vs. Rb vapor thickness Polarization in 200 Me. V polarimeter H- current (u. A) Rb-vapor thickness –n. L ( × 1013 atoms/cm 2)
Polarization (at 200 Me. V) vs. Superconducting Solenoid magnetic field in He and Rb-cells. Magnetic field in Rb-cell, k. G
Depolarization caused by spin-orbital (LS) interaction in excited 2 P states. ~92% at 20 k. G –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.
Polarization measurements at 255 Ge. V in H-jet polarimeter, Run-2013, April-25 -30
Rb-81, T 9 -current-295 u. A, (Booster input-4. 9× 1011) 84. 2+/-0. 5% 83. 9+/0. 9%
Depolarization factors P = EH 2 ∙ PRb∙ S ∙ BRG∙ ELS∙ EES ∙ ESona∙ Eion ~ 85 -90% Depol. factor Process Estimate 1 EH 2 Dilution due H 2+ in the new source (LEBT) 0. 99 - 0. 99 2 PRb Rb-optical pumping (Laser system) 0. 99 - 0. 99 3 S Rb polarization spatial distribution (Collimators) 0. 97 - 0. 98 4 BRG Proton neutralization in residual gas (Vacuum) 0. 98 - 0. 99 5 ELS Depolarization due to spin-orbital interaction 0. 98 - 0. 99 6 EES Dilution due to incomplete energy separation not polarized component of the beam (LEBT) 0. 98 - 0. 99 7 ESona-transition efficiency (Adjustment) 0. 96 - 0. 98 8 Eion Incomplete hyperfine interaction breaking in the ionizer magnetic field 0. 98 - 0. 99 Total: 0. 85 - 9/12/2013 0. 90 G. Atoian 32 9/12/2013
RHIC Polarized beam in Run 2012 OPPIS 0. 6 m. A x 300 us→ 11∙ 1011 polarized H- /pulse. LINAC (6. 0 -6. 5) ∙ 1011 polarized H- /pulse at 200 Me. V Booster (2. 2 -2. 4) ∙ 1011 protons /pulse at 2. 3 Ge. V AGS ~1. 8∙ 1011 p/bunch, P~60 -65% at 100 Ge. V P ~ 56% at 250 Ge. V (2. 0 -2. 2) ∙ 1011 p/bunch RHIC
Summary • The new source is working. Reliable long-term operation at steady current and polarization. • The maintenance time is significantly reduced. • Polarization is 80 -84%, which is 3 -5% higher then ECR-based source. It is expected that polarization can be further improved to over 85%. • The source intensity is about 3 -5 m. A. Due to strong spacecharge effects only fraction of this current is transported and accelerated in RFQ and Linac. These losses can be reduced.
Optical pumping of Rb-85 (72. 7%), Rb-87(27. 8%) natural mixture. . Effective width of Rb 85 -87 natural mixture including hyperfine Splitting and Doppler broadening is ~ 3. 2 GHz Δν ~ 8 GHz
Beam intensity and polarization vs. He-valve setpoint
Reference polarization measurements in AGS for RHIC fills. Beam intensity ~ 2*10^11 200 Me. V polarization 70% Pf-fixed target measurement Fixed target measurements: Pf. <P> = Pf / √(1 +R) ~ Pf (1 - ½ Rh) RHIC fill # ill. Number = 17417, source. Pol_run_fy 13 = 82. 5573 fill. Number = 17417, ags. Pol. T 1_run_fy 13 = 71. 3816
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