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,

September 12, 2013PSTP 2013

G. Atoiana*, V. Klenovb, J. Rittera, D. Steskia, A. Zelenskia, V. Zubetsb

aBrookhaven National Laboratory, Upton, NY 11973, USAbInstitute 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

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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?

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Plasmatron H-injector

Neutralizer H-cell

He-cellIonizer &

decelerator Rb-cellNa-jetIonizer

H+ H0 H+ H0

5-10mAH-H-cell He-cell Rb-cell Na-jet

TMP1

CP2

CP4CP3CP1

TMP2

SCS

Sona- shield

Extractorto 35KeV

OPPIS with FABS-injector layout (Run-13) OPPIS produces 3-5mA polarized H- ion pulse current

Polarization at 200MeV polarimeter ~81-84 %

4-gridsextractor(6-8keV)

Pump-laser

Beam

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Low Energy Beam Transport line

EL-tandemIs “off”

EL2-replaced with Quad triplet

Variable collimatorsto improvement ofenergy separation

New FC

The LEBT is tuned for 35keV beamEnergy transport.

Add Vert. and Horiz. steering

EL-tandemIs “off”.

Moveable optic prism

Pump-laserProbe 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.

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transformation of the longitudinal to the transverse polarization

RFG

LIN

AC

FABSSCS

Polarization dilution due H0 in the new source

Ionize

H0

7keV

40%

Rb-cell

60%He-cell

H2 -cellNeutralize

In FABS-source Inside of the SCS Ionizer & Extractor

H-

39keV

0.72%

Accelerate32keV

3%

H-

7keV

Na-jet

8%

Decelerate, ΔE=4.0keV

He-cell70%

2%

Na-jet

>90%

IonizeExtr.

Accelerate 32keV

Extr.

Ionize

H0

7keV

H+

7keV

H+

7keV

H+

3keV

Neutralize H0

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~ 0.01

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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-valveOperating in high

magnetic field ~1-3T

He-pulsedvalve

3-grid beamDeceleration system

He-cell

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Energy separation a residual un-polarized H0 component

H+(60%)H0(7keV)

-4.0 kV-4.1 kV -2.4 kV

H0(7keV)

He-cell Rb -cell

H0(40%)

Decelerationby 3-grids system

H0 + He → H+ + He + e-

H0(3keV)

+0.1 kV-3.9 kV

H+(3keV)

H0(7keV)

Ionizationin He-cell

Neutralizationin 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 25-30 times.

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Total: 0.85 - 0.90

P = EH2 ∙ PRb∙ S ∙ BRG∙ ELS∙ EES ∙ ESona∙ Eion ~ 85-90%

Depolarization factors

Depol. factor Process Estimate

1 EH2 Dilution due H2+ 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 - 0.98

6 EES Dilution due to incomplete energy separation not polarized component of the beam (LEBT)

0.98 - 0.99

7 ESona Sona-transition efficiency (Adjustment) 0.96 - 0.98

8 Eion Incomplete hyperfine interaction breaking in the ionizer magnetic field

0.98 - 0.99

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Dilution of polarization due H2

+ component- 0.03/3 ~ 0.01

Ionize

H0

3.5keV20%

Rb-cell

80%He-cell

H2+

7keVH2 -cell

Neutralize

In FABS-source Inside of the SCS

H-

35.5keV

0.03%

Accelerate32keV

H- 0%

0%

H-

3.5keV

Na-jet

0%

Decelerate (ΔE=4.0keV) RejectedHe-cell 0%

8%

Na-jet

<10% x 0.2=2% (Attenuate due to larger angular divergence ~ 0.2)

IonizeExtr.

Accelerate32keV

Extr.

Ionize

Ionizer & Extractor

H0

3.5keV

H+

3.5keV

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1 EH2 Dilution due H2+ in the new source (LEBT) 0.99 - 0.99

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.

BeforeBy quality of the probe-laser pulse

NowBy measured frequency and line width of pump-laser

Control the laser parameters

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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.

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Beam profile out of Linac Polarization profile out of Linac


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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

Dilution of polarization due residual gas at Rb thickness ~5*1013 atoms/cm2 (~350mkA) is 3.7/350 < 1.5%

iRG~3.7mkA; IL/IR ~0.315

5 ELS Depolarization due to spin-orbital interaction 0.98 - 0.98

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0

0.5

1

1.5

2

2.5

3

3.5

20 22 24 26 28 30 32 34 36

Acceleration voltage, kV

H-

ion

be

am

cu

rre

nt,

mA

31.5 + (7.5 – 4.0) = 35keV

Ratio: 3000/30 ~100

27.5 +7.5 =35keV

6 EES Dilution due to incomplete energy separation not polarized component of the beam (LEBT)

0.98 - 0.99

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He-valve ‘OFF’

He-valve ‘ON’

He-cell Rb-cell

SC-solenoidSona-transition with 3 corr. coils in it

Na-jet&

Solenoid

2 corr. coils between SCS and Sona-shield

H0 H-

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ICC-2ICC-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

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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

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8 Eion Incomplete hyperfine interaction breaking in the ionizer magnetic field

0.98 - 0.99

Beam performance during RHIC fill #17472 (May 7, 2013)

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T(Rb)=81C, I(T9)=295mkA (4.9*10^11)

83.9+/0.7%

84.2+/-0.5%

15 min

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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

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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,

Documents

h beam

atomic beam source fabs

ecr proton source

source parameters

polarized electrons

polarized hydrogen atoms

primary proton beam

ecrtype source