High-Intensity Polarized H - Beam production in Charge-exchange Collisions A.Zelenski, BNL PSTP...
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Transcript of High-Intensity Polarized H - Beam production in Charge-exchange Collisions A.Zelenski, BNL PSTP...
High-Intensity Polarized H- Beam production in Charge-exchange Collisions
A.Zelenski, BNL
PSTP 2011, September 14, St.Petersburg
RHIC: the “Polarized” Collider
STARPHENIX
AGS, 24GeVLINAC
BOOSTER, 2.5 GeV
Pol. H- ion source
Spin Rotators
20% Snake
Siberian Snakes
200 MeV polarimeter
RHIC pC “CNI” polarimeters
RHIC
Absolute H-jetpolarimeter
Design goal: P=70%, L max = 1.6 1032 s-1cm-2 50 < √s < 500 GeV
AGS pC “CNI” polarimeter
5% Snake
Polarization facilities at RHIC.Polarization facilities at RHIC.
Operational Polarized H- Source at RHIC. Operational Polarized H- Source at RHIC.
RHIC OPPIS produces reliably 0.5-1.0mApolarized H- ion current.Polarization at 200 MeV: P = 80-85%.Beam intensity (ion/pulse)routine operation:Source - 1012 H-/pulseLinac - 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 .
Polarized beams at RHIC.Polarized beams at RHIC.
OPPIS
LINAC
Booster
AGS
RHIC
1.7 10∙ 11 p/bunch
10 10∙ 11(maximum 40 10∙ 11) polarized H- /pulse.
5 10∙ 11 polarized H- /pulse at 200 MeV, P=85-90%
2 10∙ 11 protons /pulse at 2.3 GeV
~1.5∙1011 p/bunch, P~60-65% at 100 GeV P ~ 53% at 250 GeV
SPIN -TRANSFER POLARIZATION IN PROTON-Rb COLLISIONS.SPIN -TRANSFER POLARIZATION IN PROTON-Rb COLLISIONS.
Rb+
H+ H+Proton source
Proton source
Laser-795 nmOptical pumpingRb: NL(Rb) ~1014 cm-2
Sonatransition
Sonatransition
Ionizercell
Ionizercell
H-
Laser beam is a primary source of angular momentum:
10 W (795 nm) 4•1019 h/sec 2 A, H0 equivalent intensity.
Supperconducting solenoid 25 кГс
1.5 kG field
Charge-exchange
collisions: ~10-14 cm2
Na-jet ionizer cell:
NL(Na)~ 3•1015 cm-2
Electron to proton polarization transfer
ECR-29 GHz Н+ source
Rb+
Schematic Layout of the RHIC OPPISSchematic Layout of the RHIC OPPIS
29.2 GHz ECR proton source29.2 GHz ECR proton source
SCS solenoidSCS solenoid
Probelaser
Na-jetIonizer
cell
Na-jetIonizer
cell
Pumpinglaser
CryopumpsCryopumps
Sona-transition
Rb-cellSCS -solenoid
Pulsed OPPIS with the atomic hydrogen injector
at INR, Moscow, 1982-1990. The First-Generation.
Atomic H injector
Helium ionizer cell~80% ionizationefficiency. Lamb-shift
polarimeter
H- current 0.4mA, P=65%, 1986
Hydrogen atomic beam ionization efficiency in the He- cell.
Hydrogen atomic beam ionization efficiency in the He- cell.
10 keV
80%
H0 + He → H+ + He + e
OPPIS upgrade with the Fast Atomic Beam Source (FABS). The Third- Generation.
OPPIS upgrade with the Fast Atomic Beam Source (FABS). The Third- Generation.
He – ionizer cell serves as a proton source in the high magnetic field.
H+H0 H-
H0
H+
The source produces ~ 5.0 A ! (peak) proton current at 5.0 keV.
~ 10 mA H- current, P = 85-90%.~ 300 mA (high-brightness) unpolarized H- ion current.
Feasibility studies with Atomic Beam Injector at TRIUMF, 1997-99.
The Second Generation.
Feasibility studies with Atomic Beam Injector at TRIUMF, 1997-99.
The Second Generation.
A pulsed H- ion current of a 10 mA was obtained in 1999.
Pulsed OPPIS at TRIUMF, 1997-99.Pulsed OPPIS at TRIUMF, 1997-99.
A pulsed H- ion current of a 10 mA was obtained in 1999.
Atomic H
Injector.
Small diameter beam in the FABS.
• Atomic H0 injector produces an order of magnitude higher brightness beam. A 5-10 mA H- ion current can be obtained with the smaller, (about 15 mm in diameter) beam.
• Higher Sona-transition efficiency for the smaller beam radius.
• Smaller beam emittance : εn ~ B × R 2
The Atomic Hydrogen Injector
Collaboration agreement with BINP, Novosibirsk
on polarized source upgrade. • Contract with BINP, Novosibirsk. Delivery: May, 2011.• Two sets of sources and power supplies, local control
system.• 4- sets of spherical extraction grids (focal length
~150 cm) for polarized source.• 2- sets of shorter focal length (~ 50cm) grids for
studies of basic limitation of high-brightness H- ion beam production in the charge-exchange process.
BINP design for the “Atomic Beam Injector”.
Plasmatron 4-grid protonextraction system
H2 Neutralization cell
~ 5.0AequivalentH0 beam
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, H0→ 16 mA, H-
Residual unpolarized H0 beam component suppression by the energy separation.
H+(60%)H0(10keV) H0(3.0keV)
-7.0 kV-7.1 kV
-7.1 kV
-7.0 kV
H0(10.0keV)
He-ionizer cell Rb -cell
H0(40%)
DecelerationH0 + He → H+ + He + e
Polarization dilution in the FABS.
H0 (10keV)
H+ (10keV)
H+ (3.0keV)
H0 (3.0keV)
H- (3.0keV)
H- (35keV)
He-cell60%
?
50%
8.5%
2.7%
H0(10keV) H-(10keV) H-(42keV)40% 2% 0.8%
H+ (10keV)
H2-cell
0.8/2.7 =0.3- polarization dilution.7.0 keV energy separation would allow dilution reduction to less than 0.1%.
Deceleration, ΔE = - 7.0 keV
Acceleration, - 32 keV
95%
Polarization dilution by H2+ in the FABS.
H0 (5.0keV)
H+ (5.0keV)
H+ (3.0keV)
H0 (3.0keV)
H- (3.0keV)
H- (35.0keV)
He-cell80%
Beam loss at deceleration ?
50%
8.5%
3%
H0(5.0keV) H-(5.0keV) H-(37keV)20% 6% 0.12%
H+2(10ke
V) H2-cell
Deceleration, ΔE=7.0 keV
Acceleration, 32 keV
~10%
0.12/3.0 =0.04- polarization dilution.2.0 keV energy separation reduces dilution to less than 0.4%
LEBT upgrades for the Run 2010-11.
“Tandem” Einzel Lens
A new Spin Rotator Solenoid
New stirrers, Buncher, (Quads?)
Molecular component suppression by the double Einzel lens in the LEBT.
Deepak simulations.
Molecular component suppression by the double Einzel lens in the LEBT.
Extractor Voltage, kV
1.4 kV
~10-15% beam intensity losses
32.2 +2.8 =35.0 keV
Tk 9, current, 200 MeV
2.0 kV
Primary proton beam energy (~ 10.0 keV) choice.
• Higher energy gives higher beam intensity.• Lower ionization efficiency in the He-cell (~60%).• Larger deceleration (~7.0 keV) after the He-cell is
required.• H- yield reduction for 10 keV residual unpolarized
H0.
• Higher energy increases the energy separation efficiency.
• At least 10 keV energy is required for molecular H2+
beam component suppression.
Contract with Cryomagnetics, Tennesi. Delivery: December, 2011. Higher 30 kG field. Better field shape. Cold iron yoke. He- re-condenser, low maintenance cost. Two mode of operations. Atomic beam mode –long flattop. ECR- mode provides field shape for the conventional
ECR-mode operation.
A new superconducting solenoid.
Magnetic field maps for Oxford Instr. and Toshiba
solenoids. Magnetic field maps for Oxford Instr. and Toshiba
solenoids.
0
5
10
15
20
25
30
0 10 20 30 40 50 60 70 80 90 100 110 120
Position, cm
Mag
net
ic f
ield
, kG
Toshiba solenoid
Oxford solenoid
Bz -field component at the solenoid axis.
Z-
RF-power input
Rb-cell
ECR-grids
Sona-transition
Correction coil
0
5000
10000
15000
20000
25000
30000
35000
-30.0 -20.0 -10.0 0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 110.0 120.0
z (cm)
B (
Ga
uss
)
Atomic Mode (G)
OPPIS Mode (G)
Flat_Xiaofeng
ERC_Xiaofeng
A new superconducting solenoid. ECR-mode.
Contract with Cryomagnetics, Tennesi. Delivery: May, 2011
30 kG
Depolarization caused by spin-orbital (LS) interaction in excited 2P states.
Depolarization caused by spin-orbital (LS) interaction in excited 2P states.
~92% at 20 kG –low limit
Most of the H aoms are producedin excited n=2 states.
A high magnetic field has to beApplied in the optically-pumpedvapor cell to avoid depolarizationdue to spin-orbital interaction.
H- yield vs beam energy
0
1
2
3
4
5
6
7
8
9
10
0 2 4 6 8 10 12
Beam energy, keV
H-
ion
yie
ld,
%
~ 8.4 % at 3.0 keV beam energy
• An application of conventional “hot-pipe” sodium vapor cell for high-intensity H- ion beam production in charge-exchange collisions is limited by the fast increase of the sodium losses, which are proportional: ~ n3 / L ,
where n is vapor density and L- is the cell length.
The solution is the Jet-ionizer cell.
Sodium-jet ionizer cellSodium-jet ionizer cell
Sodium-jet ionizer cellSodium-jet ionizer cell
Reservoir– operational temperature. Tres. ~500 оС.Nozzle – Tn ~500 оС.Collector- Na-vapor condensation: Tcoll.~120оСTrap- return line. T ~ 120 – 180 оС.
Transversal vapor flow in the N-jet cell.Reduces sodium vapor losses for 3-4 ordersof magnitude, which allow the cell aperture increase up to 3.0 cm .
Transversal vapor flow in the N-jet cell.Reduces sodium vapor losses for 3-4 ordersof magnitude, which allow the cell aperture increase up to 3.0 cm .
Nozzle500deg.C
Collector~150 deg.C
Reservoir~500 deg.C
NL ~2·1015 atoms/cm2
L ~ 2-3 cm
H- beam acceleration to 35 keV at the exit of Na-jet ionizer cell
H- beam acceleration to 35 keV at the exit of Na-jet ionizer cell
Na-jet cell is isolated and biased to – 32 keV. The H- beam is accelerated in a two-stage acceleration system.
-32 kV
H-
35 keV
-28 keV -15 keV
H- beam acceleration to 35 keV at the exit of Na-jet ionizer cell
H- beam acceleration to 35 keV at the exit of Na-jet ionizer cell
Na-jet cell is isolated and biased to – 32 keV. The H- beam is accelerated in a two-stage acceleration system.
-32 kV
H-
35 keV
-28 keV -15 keV
Small diameter beam in the FABS.
• Atomic H injector produces an order of magnitude higher brightness beam. A 5-10 mA H- ion current can be obtained with the smaller, (about 15 mm in diameter) beam.
• Higher Sona-transition efficiency for the smaller beam radius.
• Smaller beam emittance : ε ~ B × R 2
• High-brightness source (FABS) will deliver at least 10 times more beam intensity then ECR-proton source
within the small ionizer aperture.
200 MeV Polarization CC Scan on 4/4/07
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5
Correction Coil Current (x25 = Amps)
Pol
ariz
atio
n at
200
MeV
200 MeV Polarization
11 mm radius
5 mm radius
After Sona-transition upgrade, Run 07Simulations and field measurements.A new diam. 4.0” Sona-shieldA new Correction CoilOptimized positions for shield and CC
97.5%
x x x
x
Polarization vs. ionizer solenoid current with the 12mm collimator.
80
81
82
83
84
85
86
87
88
89
90
150 160 170 180 190 200 210 220 230 240 250 260
Ionizer solenoid current, A
Po
lari
zatio
n a
t 2
00
Me
V,
%
Maximum polarization from the correction coil scans, collim. -12 mm.
160 A ↔1.16 kG, 81.6%, (95.9%)
200 A ↔1.45 kG, 84.9%, (97.0%)
250 A ↔1.81 kG , 88.1%, (98.1%) Expected:
Maximum polarization from the correction coil scans, collim. -12 mm.
160 A ↔1.16 kG, 81.6%, (95.9%)
200 A ↔1.45 kG, 84.9%, (97.0%)
250 A ↔1.81 kG , 88.1%, (98.1%) Expected:
23 mm collimator.
200 A ↔1.45 kG, 82.5% (97.0%)
250 A ↔1.81 kG , 84.5% (98.1%) A new ionizer solenoid:250 A ↔1.98 kG , 90.0% (98.4%)
23 mm collimator.
200 A ↔1.45 kG, 82.5% (97.0%)
250 A ↔1.81 kG , 84.5% (98.1%) A new ionizer solenoid:250 A ↔1.98 kG , 90.0% (98.4%)
Expected
Basic limitation on the intensity of H- beam production in the Na-jet cell.
• According to paper: A.I.Krylov, V.V.Kuznetsov. Fizika Plasmy, 11, p.1508 (1985), influence of secondary plasma on a Na-jet stable operation is determined by parameter :
α = Jσion / ev0
where: J - beam current (per cm) of jet-target length; σion – cross-section of ionization of atoms of a target, v0 – atoms velocity in the Jet.
Critical value (Jet instability) of α is ~ 0.06.• The cross section of charge exchange of protons on sodium atom has
value of: 1.2·10-14 cm2.• The electron capture cross section for hydrogen atoms in Na-jet is of: 5·10-16 cm2.
The separation of neutralization and H- production cells should allow current density increase to: J ~1.5 A/cm2,
without impact on the Na-jet operation.
High- brighthess un-polarized H- ion beam production
~ 300 mAH- ion beamH+
3.0 keV
H2 –gas neutralizer cell
H0
Na-jet ionizer cell
~ 4.0 A equivalent H0 currentthrough 2.0 cm (Diameter)Na –jet cell.
εn ~ 0.1π mm mrad
A new FABS test bench.
TMP for He pumping
FABS operation
H- current, 12 mA
Arc current, 650A
Beam energy, 7.0 keV
H- ion beam current vs beam energy (within 25 mm ionizer acceptance).
0
50
100
150
200
250
300
0 2 4 6 8
Beam energy, keV
Be
am
cu
rre
nt,
mA
H- current, (× 10)
H0-intensity
A new BINP neutral H-injector installed at the test-bench
Neutral hydrogen beam intensity profile at 250 cm distance from the
source.
20 mm
Depolarization factors in the OPPIS.Depolarization factors in the OPPIS.Depol. Factor
Process Estimate
PRb Rb polarization 0.99
S Rb polarization spatial distribution 0.97-0.99
BH2 Proton neutralization in residual gas. 0.95-0.99
+ ELS Depolarization due to spin-orbital
interaction.0.95-0.99 +
ES Sona-transition efficiency 0.98-1.00 +
E ioniz. Incomplete hyperfine interaction breaking in the ionizer magnetic field.
0.95-0.99 +
X Polarization dilution by molecular hydrogen ions in the ECR source.
X
Total: 0.81-0.95(0.9/0.8)4 ~1.6
OPPIS current and polarization vs. Rb –cell vapor thickness.
5∙1013
Rb-cell thickness, atoms/cm^2
X 1013
Higher ~105 deg Rb cell temperature
Summary I
• Atomic H injector produces an order of magnitude higher brightness beam than present ECR source.
• A 5-10 mA polarized H- ion current (50-100 mA proton current) can be obtained for the smaller (higher brightness) beam.
• The basic limitation on the production of the high-intensity (~300 mA) , high-brightness unpolarized H- ion beam in charge – exchange collisions will be also studied.
• Higher polarization is expected with the fast atomic beam source due to:
a) elimination of neutralization in residual hydrogen;
b) better Sona-transition efficiency for the smaller diameter beam;
c) use of higher ionizer field (up to 3.0 kG), while still keeping the beam emittance below 2.0 π mm∙mrad, due to the smaller beam diameter.
• All these factors combined will further increase polarization in the pulsed OPPIS to over 85%.
Summary II
LSP Polarization vs. ionizer current.
Polarized beams in RHIC.Polarized beams in RHIC.
OPPIS
LINAC
Booster
AGS
RHIC
2.2 10∙ 11 p/bunch, P ~65%
6.3 10∙ 11(maximum 40 10∙ 11) polarized H- /pulse.
3.6 10∙ 11 polarized H- /pulse at 200 MeV, P=80-82%
2.5 10∙ 11 protons /pulse at 2.3 GeV
~1.7∙1011 p/bunch, P~60-65% at 100GeV P ~ 53% at 250 GeV
200 uA X300us
Scraping in Booster