September 12, 2013 PSTP 2013 G. Atoian a *, V. Klenov b, J. Ritter a, D. Steski a, A. Zelenski a, V....
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Transcript of September 12, 2013 PSTP 2013 G. Atoian a *, V. Klenov b, J. Ritter a, D. Steski a, A. Zelenski a, V....
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
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?
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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.
9/12/2013G.Atoian 5
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
9/12/2013G.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-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.
9/12/2013G.Atoian 8
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
9/12/2013G.Atoian 9
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
9/12/2013G.Atoian 10
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
9/12/2013G.Atoian 11
2 PRb Rb-optical pumping (Laser system) 0.99 - 0.99
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
2 PRb Rb-optical pumping (Laser system) 0.99 - 0.99
3 S Rb polarization spatial distribution (Collimators) 0.97 - 0.98
9/12/2013G.Atoian 13
Beam profile out of Linac Polarization profile out of Linac
3 S Rb polarization spatial distribution (Collimators) 0.97 - 0.98
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4 BRG Proton neutralization in residual gas (Vacuum) 0.98 - 0.99
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4 BRG Proton neutralization in residual gas (Vacuum) 0.98 - 0.99
9/12/2013G.Atoian 16
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
9/12/2013G.Atoian 17
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
9/12/2013G.Atoian 18
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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7 ESona Sona-transition efficiency (Adjustment) 0.96 - 0.98
9/12/2013G.Atoian 20
7 ESona Sona-transition efficiency (Adjustment) 0.96 - 0.98
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
9/12/2013G.Atoian 21
7 ESona Sona-transition efficiency (Adjustment) 0.96 - 0.98
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
8 Eion Incomplete hyperfine interaction breaking in the ionizer magnetic field
0.98 - 0.99
Beam performance during RHIC fill #17472 (May 7, 2013)
9/12/2013G.Atoian 23
T(Rb)=81C, 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
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