Retuning and Recovery of Polarized Ammonia Target Magnet for Advanced Microwave Operations

Polarized Target “Issues” Magnet Microwaves Target Ammonia

UVA/SLAC/JLAB Target

Magnet

After SANE, and operation over 20 years in sometimes extreme conditions, magnet returned to Oxford Instruments for retuning. • Diagnosis was that magnet had become unstable over the years because of relaxation of the clamping of the coils. • At Oxford Instr. Coils reclamped to original specifications. • Magnet retested: • 1) Ramped at higher than original specified rate to 5.1 T Quenched after 15 mins in persistent mode ( training quench)

2) Ramped at specified rate to 5.0 T Stayed at field in persistent mode for 105 minutes before ramping down • 3) Ramped to 5.1 T at same rate as Test 1 Stayed at field for 105 minutes in persistent mode before ramping down. Ready to operate again in extreme conditions.

Microwaves • 140 GHz/5 T EIO – have several NH3 Polarization > 90% • 70 GHz/2.5 T Carcinotron (have several) or EIO (borrow one from Duke University). EIO has higher power output than Carcinotron. Polarization ~40% Changing EIOs easiest to do – use same power supply.

Microwaves (contd.) • Microwave guides at 70GHz. (Have at UVA) • Frequency and power read-outs at 70 GHz (Have at UVA ) • EIO power supplies ~ four, between UVA and JLab • Carcinotron Power supplies: one at UVA, one somewhere in Germany on way to UVA

NMR • Have all the necessary equipment, many Q –meters, several signal generators and power supplies. • Only need to retune system at 106.5 MHz (2.5 T) from 213 MHz (5 T)

Ammonia Targets • All the polarized material will be irradiated ammonia (14NH3).

Ammonia Targets (contd.) • Ammonia irradiated at the MIRF facility at NIST • Use 19 MeV electrons at 10 – 15 μA • Irradiate to the level of ~1017 e-.cm-2 One irrad. Load ~ 2.5 target loads • Need ~ 18 target loads

Ammonia Targets (contd.) • Current inventory: ~ 16 target loads – checking further. • Unirradiated inventory: 3 target loads – checking further • Previously used material: ???? • Next irradiation (probably June) • Last Irradiation: October 2009

NH3 (2nd Batch)

Participation • Faculty Level Don Crabb, Donal Day, Oscar Rondon • Post Docs HovannesBaghdasaryan, NarbeKalantarians Jonathan Mulholland? • Students • “Stache” Kvaltine, ZihongJi, Mikhail Yurov

Retuning and Recovery of Polarized Ammonia Target Magnet for Advanced Microwave Operations

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