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
-1cm-2 50 < √s < 500 GeV
= 1.6  the
1032 s“Polarized”
RHIC:
Collider
max
RHIC pC “CNI”
polarimeters
Absolute H-jet
polarimeter
RHIC
PHENIX
STAR
Siberian Snakes
Spin Rotators
Pol. H- ion source
5% Snake
LINAC
AGS, 24GeV
200 MeV polarimeter
BOOSTER, 2.5 GeV
AGS pC “CNI” polarimeter
20% Snake
Operational Polarized H- Source at RHIC.
RHIC OPPIS produces
reliably 0.5-1.0mA
polarized H- ion current.
Polarization at 200 MeV:
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 kG field
ECR-29 GHz
Н+ source
Supperconducting
solenoid 25 кГс
Charge-exchange
collisions: ~10-14 cm2
Electron to proton
polarization transfer
Laser beam is a primary source of angular momentum:
10 W (795 nm)
4•1019 h/sec
2 A, H0 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 0.4mA, P=65%
Lamb-shift
polarimeter
Pulsed OPPIS at TRIUMF, 1997-99.
Second generation.
Atomic H
Injector.
A pulsed H- ion current of a 10 mA was obtained in 19
OPPIS with atomic H injector layout. RHIC 2012.
The third generation.
OPPIS with atomic H injector layout.
CP1
TMP1
Neutralizer
cell
Atomic
H injector
H+
H2
He-ionizer
cell
He
H0
Na-jet
cell
Rb-cell
H+
Rb
H0
Na
H-
Hydrogen atomic beam ionization efficiency in the He- cell.
H0 + He → H+ + He + e
80%
10 keV
H- yield vs beam energy
10
~ 8.4 % at 3.0 keV beam energy
9
H- ion yield, %
8
7
6
5
4
3
2
1
0
0
2
4
6
8
Beam energy, keV
10
12
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 MeV 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
H0 beam
H2 Neutralization cell
FABS produces 200-300 mA equivalent H0 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 kG
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
500deg.C
Collector
~150 deg.C
NL ~2·1015 atoms/cm2
L ~ 2-3 cm
Reservoir
~500 deg.C
Reservoir– operational temperature. Tres. ~500 оС.
Nozzle – Tn ~500 оС.
Collector- Na-vapor condensation: Tcoll.~120оС
Trap- return line. T ~ 120 – 180 оС.
H- beam acceleration to 35 keV at the exit
of Na-jet ionizer cell
H-
35 keV
-32 kV
-28 keV
-15 keV
Na-jet cell is isolated and biased to – 32 keV. The H- beam is
accelerated in a two-stage acceleration system.
H- beam acceleration to 35 keV at the exit
of Na-jet ionizer cell
H-
35 keV
-32 kV
-28 keV
-15 keV
Na-jet cell is isolated and biased to – 32 keV. 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 uA
at 200 MeV, Rb-96 deg, May 3, 2013
H- ion beam current-700 uA
at injection to RFQ
Polarized injector, 200 MeV linac and injection lines.
Polarization direction is
adjusted vertically in
the 750 keV beamline
by the solenoidal spin rotator.
200 MeV
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 MeV.
Rb-cell, Temp., deg. C
Linac Current, μA
81
295
86
370
91
430
96
570
Booster Input ×1011
4.9
6.2
7.3
9.0
Pol. %, at 200 MeV
84
83
80.5
78
H- beam current and polarization at 200 MeV
vs. Rb vapor thickness
Polarization in 200 MeV polarimeter
H- current (uA)
Rb-vapor thickness –nL ( × 1013 atoms/cm2)
Polarization (at 200 MeV) vs. Superconducting Solenoid
magnetic field in He and Rb-cells.
Magnetic field in Rb-cell, kG
Depolarization caused by spin-orbital (LS) interaction in
excited 2P states.
~92% at 20 kG –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 GeV
in H-jet polarimeter, Run-2013, April-25-30
Rb-81, T9-current-295 uA, (Booster input-4.9×1011)
84.2+/-0.5%
83.9+/0.9%
Depolarization factors
P = EH2 ∙ PRb∙ S ∙ BRG∙ ELS∙ EES ∙ ESona∙ Eion ~ 85-90%
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 - 0.99
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
9/12/2013
Total: 0.85 - 0.90
G.Atoian
G.Atoian
32
9/12/2013
RHIC Polarized beam in Run 2012
OPPIS
0.6mA x 300us→11∙1011 polarized H- /pulse.
LINAC
(6.0-6.5) ∙1011 polarized H- /pulse at 200 MeV
Booster
(2.2-2.4) ∙1011 protons /pulse at 2.3 GeV
AGS
~1.8∙1011 p/bunch, P~60-65% at 100 GeV
P ~ 56% at 250 GeV
(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 mA. 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 MeV polarization
70%
Pf-fixed target
measurement
Fixed target measurements: Pf.
<P> = Pf / √(1 +R) ~ Pf (1- ½ Rh)
RHIC fill #
illNumber = 17417, sourcePol_run_fy13 = 82.5573
fillNumber = 17417, agsPolT1_run_fy13 = 71.3816