Transcript Solid Polarized Target Opportunities at JLab

Solid Polarized Target
Opportunities at JLab
Possibilities for Future
Experiments
Introduction
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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
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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
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
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EIO “standard” especially at higher frequencies – eg. 140 GHz 10 –
15 W. Tuning range ~ 1.5%
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But can now obtain ~3 to 5 W close to 200GHz ~6W at 183GHz
and 2.5 Wat 211 GHz
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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
Target materials
Performance and Experience
NH3
Polarization growth, radiation damage, decay of material
Target materials
Performance and Experience
ND3
6LiD
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~ 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%
6Li
CD2
d-butanol
d-butanol
1-d-pentanol
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Deuteron Polarization %
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-60
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10 electrons cm Incident
Results
on
trityl
doped
The deuteron NMR signal with quadrupole interaction
hydrocarbons
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?