Polarized 3He

++

ion source development for RHIC.

A.Zelenski. J.Alessi, E.Beebe, A.Pikin, A.Kponou, D.Steski

• Check the Bjorken Spin Sum Rule (the difference between the 1st moments of the proton and neutron spin structure function). Violation of that would be a very big deal. If we find the rule to be CONFIRMED, i.e. no violations, then these evaluation will give the BEST value of the strong coupling constant Alpha-S and its running. A.Deshpande

• Polarized 3He ++ ions can be accelerated in RHIC with the present “siberian snakes”.

• Electron Beam Ion Source is being constructed at CAD.

EBIS ionizer for polarized

3

He gas .

He-3 metastability -exchange polarized cell P - 80-90%.

2.5·10 11 He ++ /pulse RFQ Pumping laser 1083 nm.

He(2S)→ He(1S) EBIS-ionizer, B~ 50 kG

He-transfer line. Valve.

~50·10 11 , 3 He /pulse.

EBIS ionizer for polarized

3

He gas.

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

• 3 He gas is injected in the EBIS ionizer. Pulsed valve?

• 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, B c (He + ) = 3.1 kG • The charge ratio He ++ /He + >> 1.

• The number of He ++ ions is limited to maximum charge which can be confined in EBIS (about 2.5 ·10 11 of 3 He ++ /store).

• It is sufficient to obtain ~10 11 He ++ /bunch in RHIC.

E-Gun ( 10 A )

Electron Beam Ion Source at RHIC

Superconducting Solenoid ( 6 T ) Drift Tube Structure Electron Collector Acceleration Tube What intensity is expected?

Capacity will be 10 12  ~ 2-3 x 10 11 3 He ++ charges/pulse ions per pulse ?

EBIS Preinjector Layout in lower equipment bay of 200 MeV Linac Booster EBIS RFQ Linac 17 keV/u 300 keV/u 2 MeV/u 100 MHz

Ion Q/m Current Pulse Length Rep. Rate Time to switch species He - U ≥1/6 > 1.5 emA (for 1 turn inj) 10



s 5 Hz 1 second

SUMMARY

• Expected Results.

• Building of the He –3 polarizing setup.

• Study the limitation on the maximum attainable nuclear 3 polarization in the metastability-exchange technique.

• Study the possible depolarization effects during polarized He gas injection to EBIS and multi-step ionization process.

• 3He++ beam polarimeter development for polarization measurements and optimization.

• Requested budget: $545 k/ 3 years (2 years postdoc is included).