The Relativistic Heavy Ion Collider high-intensity polarized H- ion source

The Relativistic Heavy Ion Collider high-intensity polarized H- ion source

A.Zelenski, G.Atoian, D.Raparia, J.Ritter, D.Steski Brookhaven National Laboratory

ICIS 2015, August 28, 2015

• Optical pumping polarization technique• Charge-exchange collisions• High-brightness atomic beam source• He-ionizer cell• Sodium-jet ionizer cell• Summary

Summary

• The old RHIC OPPIS based on ECR primary proton source retired after successful operation in Runs 2000-2012.

• The new source with atomic beam hydrogen injector and He-ionizer was developed in 2010-12 and commissioned for operation in Run-2013.

• It produces significantly higher brightness primary proton beam which resulted in higher polarized beam intensity and polarization delivered for injection to Linac-Booster-AGS-RHIC accelerator chain.

• Practically all OPPIS systems were modified (in addition to the ECR-source): a new superconducting solenoid; new He-ionizer cell with a pulsed He-injection and new pulsed electro-magnetic gas valve; beam energy separation system developed for un-polarized residual beam suppression; new vacuum system with turbo-molecular pumps for He-pumping; laser control, diagnostics and transport systems.

The RHIC OPPIS upgrade with atomic hydrogen injector, Run-2013-15

BNL - BINP, Novosibisk -INR, Moscow collaboration

STARPHENIX

AGS, 24GeVLINAC

BOOSTER, 2.5 GeV

Pol. H- ion source

Spin Rotators Siberian Snakes

200 MeV polarimeter

RHIC pC “CNI” polarimeters

RHIC

Absolute H-jet

polarimeter

L max = 1.6 1032 s-1cm-2 50 < √s < 510 GeV

AGS pC “CNI” polarimeter

Polarization facilities at RHIC

OPPIS

LINAC

Booster

AGS

RHIC

(2.0-2.5) 10∙ 11 p/bunch

1.0 mA x 300us→18 10∙ 11 polarized H- /pulse.

9.0 10∙ 11 polarized H- /pulse at 200 MeVroutinely in Run-15

(2.5-3.0) 10∙ 11 protons /pulse at 2.3 GeV

~1.8∙1011 p/bunch, P~60-65% at 100 GeV P ~ 58% at 255 GeV

RHIC Polarized beam in Run 2013-15

It is expected, that use of Electron Lenswill allow increase of the bunch intensity to ~2.5∙1011 p/bunch.

What can we learn about “swiss” watches from watches collisions?

Actually a lot!In particular, if protons are polarized!

Intermediate bozons W± - can be produced directly in electroweak processes in collisions of polarized proton beams of a 250 GeV energy at RHIC.

In this case parity-violation can be as large as 50% and spin-correlation can be used for studies of different flavor quark contribution to the proton spin.

SPIN -TRANSFER POLARIZATION IN PROTON-Rb COLLISIONSSPIN -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 fieldCharge-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

~50 mA, 2.8keV

Rb+

Optical Pumping polarization technique. A. Kastler, Nobel prize 1966

5S1/2

5P1/2

λ = 795 nm

Circularly

Polarized lig

ht

MJ = -1/2 MJ = +1/2

Spontaneous

decays.

nLJ

~ 100% polarized Rb

atoms!

1.56 eV

relaxation

Optical pumping application is limited by available laser power!?Recent progress in laser technology is very promising for new applications.

MJ = +1/2MJ = -1/2

Pulsed OPPIS with the atomic hydrogen injector at

INR, Moscow, 1982-1990. First generation

Atomic H0 injector

Helium ionizer cell~80% ionizationefficiency.

Lamb-shift polarimeterH- current- 0.4mA

H+ current- 4.0 mA, P=65%, 1986

New generation OPPIS with atomic H0 injector

Atomic Hinjector He-cell

H-

High-brightness proton beam inside strong 2.5 T solenoid field produced by atomic H beam ionization in the He-gas ionizer cell

The proton beam intensity is about 1.0 A !

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

“Fast Atomic Beam Source”, BINP, Novosibirsk, 2012

Plasmatron 4-grid protonextraction system

H2 Neutralization cell

~ 3.5 AequivalentH0 beam

FABS produces 200-300 mA equivalent H0 beam intensityWithin the Na-jet ionizer acceptance.

FABS 4-grid spherical Ion Optical System

3-5 A of proton beamAt 6-8 keVenergy

1820 holes , 1.0 mm in diameter

FABS and neutralizer cell.

Neutral hydrogen beam intensity profile at 250 cm distance from the

source.

FWHM

~ 20 mm

Residual un-polarized H0 beam component suppression by the energy separation

H+(70%)

H0(6.5 keV)

H0(2.5 keV)

-4.0 kV-4.1 kV -4.1 kV

H0(6.5keV)

He-ionizer cell Rb -cell

H0(30%)

DecelerationH0 + He → H+ + He + e

-2-3 kV +0.1kV

He-ionizer cell and 3-grid energy separation system.

He-pulsedvalve

3-grid beamdecelerationsystem

“Electro-magnetic” valve operation principle.

Force to the conducting plate in the (high ~ 3 T) magnetic field.

For I=100 A, L=5 cm, F=15 N).

I

B

F

New OPPIS with atomic H0 injector layout, 2013

Rb-cell

H+H0 H+ H0 H-

H2 He Rb Na

CP1

Na-jetcell

Atomic Hinjector

He-ionizercell

Neutralizer H2-cell

TMP1

Rb-cell Sonatransition

H- yield vs. H0 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,

%

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

39 keV

-28 keV -15 keV

3 keV7 kev

H0

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

Low Energy Beam Transport line.

Variable collimatorIn DB2 to improveEnergy resolution.

Lamb Shift Polarimeter

FC435.0 keV

FC-Tk1,750keV

OPPIS

23.7 deg bender

RFQ

Energy separation of decelerated

(“polarized”) H- ion beam in LEBT.

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 kV

31.5 + (7.5 – 4.0) = 35 keV

1400/30=47

06 Dec, 2013Note#31,page75

BeamEnergy=6.5keV; IONZ=220A; Polarized H-current at 750 keV energy(after RFQ) vs. Rb-cell temperature

NL~10×1013

atoms/cm2

Rb cell temperature, deg. C

1.0 mA × 300 us =18×1011 ions/pulse

12uA

Polarized H- current-1.05 mA, after RFQ 750 keV Rb-98º

100 us/div

200 uA/div

Rb-90, 200 MeV, T9-620uA

600 µA × 400 µs →14.4 ∙1011 protons/pulse

Polarization (at 200 MeV) vs. SCS magnetic field in He and Rb-cells

Magnetic field ,kG

Source intensity and polarization.

Rb-cell thickness-NL 4.5 5.5 7.5 10.4

Linac Current, μA 500 560 680 750

Booster Input ×1011 9.0 10.0 12.2 13.5

Pol. %, at 200 MeV 84 83 80.5 78

• 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 thickness ,NL ×1013 atoms/cm2

H- beam current and polarization at 200 MeV vs. Rb vapor thickness

Rb-vapor thickness –nL –atoms/cm2

H- ion beamcurrent (mA)

Polarization in 200 MeV polarimeter

Equal 12 deg and 16 deg polarization numbers

Polarization at 200 MeV -85.2%

Long-term polarization stability, April 14-23, 2014

86%

Polarization in AGS, 23 GeV

Polarization measurements at 255 GeV in H-jet polarimeter, Run-2013, April-25-30

<

~ 62% in collisions

High intensity polarized proton sources makes feasible the high luminosity RHIC operation to study:

spin proton structure,

fundamental tests of QCD and electro-weak interaction.

Summary

• The old RHIC OPPIS based on ECR primary proton source was retired after successful operation in Runs 2000-2012.

• The new source with atomic beam hydrogen injector and He-ionizer was developed in 2010-12 and commissioned for operation in Run-2013.

• It produces significantly higher brightness primary proton beam which resulted in higher polarized beam intensity and polarization delivered for injection to Linac-Booster-AGS-RHIC accelerator chain.

• Practically all OPPIS systems were modified (in addition to the ECR-source): a new superconducting solenoid; new He-ionizer cell with a pulsed He-injection and new pulsed electro-dynamic gas valve; beam energy separation system developed for un-polarized residual beam suppression; new vacuum system with turbo-molecular pumps for He-pumping; laser control, diagnostics and transport systems.