Polarized source upgrade RSC, January 11, 2013

OPPIS LINAC Booster AGS RHIC ( ) ∙10 11 p/bunch 0.6mA x 300us→11∙10 11 polarized H - /pulse. ( ) ∙10 11 polarized H - /pulse at 200 MeV ( ) ∙10 11 protons /pulse at 2.3 GeV ~1.8∙10 11 p/bunch, P~60-65% at 100 GeV P ~ 56% at 250 GeV RHIC Polarized beam in Run 2012

OPPIS with neutral H injector layout. Atomic H injector Neutralizer cell He-ionizer cell Rb-cell Na-jet cell H+H+ H0H0 H+H+ H0H0 H-H- H2 HeRbNa TMP1 CP1

The FABS and new SCS at operational OPPIS bench.

The FABS and new SCS at operational OPPIS bench

“Fast Atomic Beam Source”, BINP 2011 Plasmatron 4-grid proton extraction system H2 Neutralization cell ~ 3.5 A equivalent H 0 beam FABS produces mA equivalent H0 beam intensity Within the Na-jet ionizer acceptance.

Residual un-polarized H 0 beam component suppression by the energy separation. H + (70%) H 0 (7 keV) H 0 (3.0keV) -4.0 kV-4.1 kV H 0 (7.0keV) He-ionizer cell Rb -cell H 0 (30%) Deceleration H 0 + He → H + + He + e -2-3 kV+0.1kV

Polarization dilution in the FABS. H 0 (7 keV ) H + (7 keV) H + (3.0keV) H 0 (3.0keV) H - (3.0keV) H - (35keV) Ionization in He-cell ~70% Neutralization in Rb, ~70% Na-jet, 8.0% Polarized ~ 4.0 % H 0 (7 keV)H - (7 keV)H - (39 keV) 40%2% H + (7 keV ) H2-cell 0.8 / 4.0 ~ 20% - polarization dilution. 4.0 keV energy separation would allow dilution reduction to less than 0.5%. Losses at Deceleration, ΔE = keV, ??? Acceleration - 32 keV 95% Un-polarized ~ 0.8 %

He-ionizer cell assembly with electro-dynamic valve and proton deceleration system. Electro-dynamic valve Three-grid Energy-separation system

He-ionizer cell assembly with electro-dynamic valve and proton deceleration system. Grid heater to reduce Rb deposition

Electro-dynamic valve operation principle. Electro-dynamic valve. Force to the conducting plate in the (high ~ 3 T) magnetic field. For I=100 A, L=5 cm, F=15 N).

Electro-dynamic valve. 1 – body, 2 – current vacuum feed-through, 3 – gas supply, 4 – flexible springing plate, 5 – “O” -ring.

Changes in the Low Energy Beam Transport Line. EL2-replaced with the Quad doublet Variable collimator In DB2 to improve Energy resolution. New FC The LEBT is tuned for 35 keV beam Energy transport.

Energy separation of decelerated (“polarized”) H - ion beam in LEBT (7.5 – 4.0) = 35 keV I (He-”on”)/ I(He –”off”) ~50

535 uA in FC after RFQ, Rb-91 deg. I=200 A

Energy separated beam vs. Rb – cell temperature 30 uA- He-off 1400 uA- He-cell “on” ( )= 35 keV E0 =7.5 keV ΔE=4.0 kV FC4, uA

Beam production and transport vs. Rb-temperature at different primary beam intensities.

Rb-91 deg, T9-current-525 uA, I=200A

T9-current-600 uA, Rb-96 deg, I=200 A,

Superconducting Solenoid Sona transition Ionizer solenoid Large Correction Coil OPPIS magnetic field, Sona-transition field shape control. Internal Correction Coils

Higher residual field with the new solenoid. Use of iron shield and four correction coils allowed of field gradients control to the required level. Still there is a room for improvements. 80 %

Laser system upgrade. New wavelength meter.

Optical pumping of Rb-85 (72.7%), Rb-87(27.8%) natural mixture.. Effective width of Rb natural mixture including hyperfine Splitting and Doppler broadening is ~ 3.2 GHz Δν ~ 8 GHz

Laser frequency scan. 200 MeV polarization vs. laser frequency. ~ 12 GHz Spin “up”

Spin “down”

Dec.16, T9-current 220 uA, Pol-78.7+/-0.7%

Polarization vs. Rb –temperature. 90 deg 80 %

Polarization measurements in Lamb-shift polarimeter. Rb-cell vapor thickness

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

Recent progress. The new solenoid works well. Both atomic H sources are in operation. Plasmatron operation is quite stable and reliable. High –intensity H- ion beam production, acceleration to 35 keV, transportation in LEBT were studied. 4 mA H - ion beam was obtained out of Linac. He-ionizer cell works well with a new pulsed magneto-dynamic He gas valve. Reliable deceleration of proton beam was demonstrated. Very good beam energy separation (Suppression of the “wrong” energy un-polarized beam component) was demonstrated. A uA energy separated H - ion beam was produced for injection to RFQ. Beam polarization measurement are in progress in 200 MeV polarimeter % polarization was obtained so far.

Recent tests at 200 MeV. Goals: Reliability studies. Polarization and intensity optimization. MCR operator training.

Reliable operation Intensity Polarization

Results so far. Reliable long-term ∙operation of the source was demonstrated. Very good suppression of un-polarized beam component was demonstrated. Small beam emittance (after collimation for energy separation) and high transmission to 200 MeV uA beam intensity was obtained at 200 MeV ( ) ∙10 11 H - /pulse at Rb –vapor thicknes ~6 ∙10 13 atoms/cm 2, (90 deg. cell temperature). ~ 78-80% polarization was measured in 200 MeV polarimeter at beam intensity uA. ~ 80-82% polarization at 150 uA. ~ 74-76% at intensity uA. After a new set of magnetic field measurements the Rb-cell position was moved ~ 100 mm upstream in a field flattop part. Hopefully, it will improve polarization.

Summary  It looks like the source reliability is acceptable for the use in the RHIC Run 13.  The beam intensity and polarization is comparable with the best ECR-based OPPIS operation.  Beam intensity of ~10 ∙10 11 was obtained (Booster input).  Polarization measurements and optimization will be continued. There is a room for improvements.

LINAC (T9) H - beam current 4.0 mA at 200 MeV E inj = kV=35 keV, May 14, /0.03 ~33 Suppression factor for Un-polarized beam component 4.0 mA

Linac current vs. Rb vapor thickness. 400 uA at 200 MeV 7.4∙10 11 H - /pulse at Rb thickness 13∙10 13 Rb/cm 2

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 -