(1)with gradient coil current 0 A, target
polarization (in pumping chamber) dropped from 31% to 23% in 25 minutes,
stayed there for 3 hours, then slowly went back up. See Figure 1.
This shows that masing threshold without field gradient is 23%.
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![](masing/masing-5A.jpg) |
(2) with gradient coil current 5 A, polarization dropped from 43% to
39% in 20 minutes, stayed there for 3 hours, then slowly went back up.
See Figure 2. This indicates that masing threshold with field
gradient 5 A is 39%.
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(3) with gradient coil current 7 A, polarization dropped linearly as
EPRs were performed, which can be explained by normal AFP loss due to
EPR measurements. See Figure 3. Polarization was continuously
dropping because only two lasers (compared to thress) were used during
this test.
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- Comments: These 3 tests show typical masing effect on GORE. By
applying a gradient current of 7 Amp (corresponds to field gradient
??? mG/cm) masing was gone.
- Notes: By NMR we also did a few tests to study masing effect.
But the masing we observed on GORE probablly starts from pumping
chamber then slowly transfers to target chamber. Since EPR measures
the polarization inside pumping chamber while NMR is for target
chamber, so EPR is more sensitive to masing effect here.