Solid Polarized Target Opportunities at JLab

Possibilities for Future Experiments

Introduction

• 4He, 3He and 3He/ 4He dilution refrigerators used over ~ 40 years.

• Divergence to using either 4He or dilution fridges• At same time – improvement in magnets• DNP process used over range of 2 T to 7 T and 100 mK

to ~1 K.• Modern Systems High power in high intensity beams

Moderate power in low intensity or

neutral beams• Most recent progress in materials

Requirements for DNP• Target material doped with paramagnetic

centers

• Cryogenic system to reach temperatures of < 1K

• Magnetic field > ~ 2 Tesla

• Microwave system – 140 GHz at 5 T

• NMR to measure polarization

Major Polarized Target Systems

UVA/SLAC/JLAB Target

SMCryostat_95.ps

DNP

• TE Polarization

• PTE = exp[uB/kT]

• Enhanced Polarization

• Penh = exp[uB/kTS]

The Conventional Hall B Polarized Target

Protons (and deuterons) in 15NH3 (15ND3) are continuously polarized

by 140 GHz microwaves at 5 Tesla, 1 Kelvin

Used for several experiments (beam current ~ 2 nA – 7 nA)Currently running eg1 dvcs

Proton polarization: ~75 – 90%Deuteron polarization: ~25 - >45%

1.5 cm

Microwaves• EIO “standard” especially at higher frequencies – eg. 140 GHz 10 –

15 W. Tuning range ~ 1.5%

• But can now obtain ~3 to 5 W close to 200GHz ~6W at 183GHz and 2.5 Wat 211 GHz

• But no mechanical tuning – electrical tuning range ~200 MHz . Move magnetic field to reach both polarization signs.

Do not buy microwave tube until magnetic field is known!

Materials

Standard at JLab:

Radiation doped NH3 and ND3

Butanol doped with TEMPO

Investigate:

Radiation doped alcohols and other materials with high proton or deuteron content.

Have looked at CH2 , CD2 , BH3NH3 , butanol, d-butanol,d-pentanol etc.

Future: Ethane and Methane

Table of polarized Target Materials

Ammonia Polarization

Acrobat Document

Performance and ExperienceTarget materials

Polarization growth, radiation damage, decay of material

NH3

Performance and ExperienceTarget materials

ND3

6LiD

• 6Li ~ d + alpha 50% Dilution Factor• Actual Dilution factor ~ 40%

• PLi ~ Pd

• Irradiation: at 180 K for ~2. 1017 e- cm-2

• Used in SLAC experiments E155 and E155X (g1

and g2 for proton and neutron). E143 used 15ND3

• Agreement at ~ 5% to 10% level

• JLab experiment 6LiD/ND3 to ~1%

Acrobat Document

6dcool.eps

Acrobat Document

1 10-60

-40

-20

0

20

40

60

Deu

tero

n P

olar

izat

ion

%

1015electrons cm-2Incident

CD2

d-butanol d-butanol 1-d-pentanol

Results on trityl doped hydrocarbons

The deuteron NMR signal with quadrupole interaction

The maximum polarizations at B = 2.5 T !!

CONCLUSIONS

• Repair 5 T magnet depending on cost.• Construct new 1 K refrigerator• New magnet for g2p experiment in Hall A Design to accommodate existing and new refrigerators Existing magnet a spare for experiment

• For 12 GeV more complicated transverse magnet .

• Horizontal 1 K fridge for Hall B• Frozen Spin Refrigerator – internal polarizing

magnet?• Material Development. - DNP of HD?