A proposal for a polarized 3 he ion source with the ebis ionizer for rhic
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A proposal for a polarized 3 He ++ ion source with the EBIS ionizer for RHIC. A.Zelenski, J,Alessi, E.Beebe, A.Pikin BNL M.Farkhondeh, W.Franklin, A. Kocoloski, R.Milner, C. Tschalaer, E.Tsentalovich MIT-Bates E.Hughes Caltech SPIN 2004, Trieste. Motivation.

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A proposal for a polarized 3 he ion source with the ebis ionizer for rhic

A proposal for a polarized 3He++ ion source with the EBIS ionizer for RHIC.

A.Zelenski, J,Alessi, E.Beebe, A.PikinBNL

M.Farkhondeh, W.Franklin, A. Kocoloski, R.Milner, C. Tschalaer, E.TsentalovichMIT-Bates

E.HughesCaltech

SPIN 2004, Trieste


Motivation
Motivation

  • Polarized 3He ~ polarized neutron => compatible with existing spin manipulation capability in RHIC

  • In all previous experimental study of the spin structure of the nucleon, measurements on the neutron have been essential

  • For eRHIC, polarized neutron as well as polarized proton allows tests of the fundamental Bjorken Sum Rule


3 he basic properties
3He - basic properties.

  • 3He magnetic moment - 2.13 μN

  • Critical fields to break hyperfine interaction:

  • 3He(1S0) - B = 10 G-holding field

  • 3He(23S1) - Bc = 2.407 kG

  • 3He+(1S) - Bc= 3.087kG

  • 3He+(2S) - Bc= 0.386 kG


Polarized 3 he sources status 1984
Polarized 3He sources. Status 1984.

No new operational 3He ion sources were built.A number of new ideas were proposed and tested (not successfully).

Spin-exchange and “metastability-exchange” techniques for 3He atoms polarization were greatly improved due to laser development and demanding applications.


State of the art performance from

Mainz group using new fiber lasers

50 bar liters/day = 1.3 x 1020 atoms/sec


Rise texas a m polarized 3 he source
Rise/Texas A&M polarized 3He+ source.

The source was operated at Texas A&M cyclotron during the 1976-78.


Monte-Carlo simulations for 3He++ polarization in ECR ionizer. Excitation cross-section is an order of magnitude larger than ionization to He++. There will be a polarization loss in excited states in <10 kG field ECR source. Polarization 10-20%.

ECR-ionizer for the 3He++ ions. RCNP, Osaka.

3He polarizer

ECR

ionizer


Ebis ionizer for polarized 3 he gas proposal
EBIS ionizer for polarized 3He gas (proposal).

  • Polarized 3He gas is produced by a “metastability exchange” technique. P ~ 70-80% (pressure ~ 1 torr).

  • 3He gas is injected in the EBIS ionizer.

  • The ionization in EBIS is produced in a 50 kG field.

  • This field will greatly suppress the depolarization in the intermediate He+ single charge state, Bc(He+) = 3.1 kG

  • The charge ratio He++/He+>> 1.

  • The number of He++ ions is limited to the maximum charge which can be confined in EBIS (about 2.5 ·1011 of 3He++/store).

  • It is sufficient to obtain ~1011 He++/bunch in RHIC.


Ebis ionizer for polarized 3 he gas proposal1
EBIS ionizer for polarized 3He gas (proposal).

He-3 metastability-exchange polarized cell.

2.5·1011 He++/pulse

He(2S)

RFQ

EBIS-ionizer,

B~ 50 kG

Pumping laser 1083 nm.

He-transfer line.

~50·1011 , 3He/pulse. P=70-80%.


Polarized 3 he gas injection into the ebis ionizer
Polarized 3He gas injection into the EBIS-ionizer.

  • Polarized 3He gas can be transported without depolarization through glass and coated metal tubes.

  • There is a limitation due to the magnetic field gradient from the strong EBIS field in the transport line. Calculations show that there is no significant depolarization with the real magnetic field of the EBIS superconducting solenoid. A. Kocoloski (MIT)


Direct optical pumping of the fast 3 he 2s beam proposal
Direct optical pumping of the “fast” 3He(2S) beam (proposal).

He(2S)

He++

  • After Cs-neutralizer cell almost 100% of He-atoms are in (23S1) state. Energy defect-0.38 ev.

  • Direct optical pumping can produce near 100% nuclear polarization in He(2S) states. P( He++) ~80-90%.

He(2S)

EBIS

ionizer

He+ source

Cs-vapor cell

100 mA of a 1.0 keV energy He+ ion beam

4He-gas

Ionizer cell

He++

EBIS

ionizer

Optical pumping

at 1083 nm

He+

~3 kG field


3 he nuclear polarization measurements
3He++ nuclear polarization measurements.

  • After acceleration to 300 keV/amu in RFQ a nuclear reaction like

    3He +D p + 4He + 18.35 MeV.

  • Lamb-shift polarimeter technique can be used after He++ conversion to He+(2S) in the alkali-vapor cell. This polarimeter operates at the source energy of a 10-20 keV.


Summary
Summary.

  • There exist several possible techniques to produce a required polarized 3He beam pulse intensity of about 2·1011 He++/pulse.

  • We propose a feasibility study of a polarized 3He++ source using the operational BNL EBIS ionizer and a metastability –exchange polarized 3He gas cell.

  • The expected beam intensity is about 2.5·1011

    3He++/pulse with nuclear polarization: P >70 %.


Birmingham lamb shift polarized 3 he ion source 1974
Birmingham Lamb-shift polarized 3He ion source,1974.

This source was operated at the cyclotron in 1970-80 s .


Double charge exchange polarized 3 he ion source inr moscow proposal
Double charge-exchange polarized 3He++ ion source INR, Moscow (proposal).

1015 3He/cm2,

P ~ 70-80%

Cross-section: σ (4He++ +3He →4He + 3He++) = 4·10-16 cm2 at 50 eV beam energy.

Estimated current 100 uA polarized 3He++.


Ionization rates for he and 3 he by electron bombardment
Ionization rates for He+ and 3He++ by electron bombardment


Spin exchange polarization in proton rb collisions
SPIN-EXCHANGE POLARIZATION IN PROTON-Rb COLLISIONS.

Laser-795 nm

Optical pumping

Rb: NL(Rb) ~1014 cm-2

Stripper at 150kev,

or EBIS

Rb+

Rb0

He+

He+ source

He+

He+

Sona

transition

Ionizer

cell

He++

1.5 kG field

Supperconducting solenoid 25 кГс

Spin-exchange collisions:~0.6·10-14 cm2

Electron to proton polarization transfer

Laser beam is a primary source of angular momentum:

10 W (795 nm) 4•1019 h/sec



Spin exchange polarization cross sections
Spin-exchange polarization cross-sections.

Spin-exchange cross-sections lower than expected?

Higher Rb thickness is required (~1015 at./cm2) to obtain high polarization.


M tanaka s conclusions
M.Tanaka’s conclusions.

Very high Rb thickness is required!


3 he production in spin exchange source
3He++ production in spin-exchange source


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