Diffusion rate
email from Jin
I am writing to propose another possible quick target lab measurement to extract the diffusion rate.
As introduction, for two chamber dynamic model, polarization VS time in both chambers are imposition of two exponential curves, fast and slow ones.
· The slow time constant (~4 hour) is sensitive to spin exchange rate and pumping chamber spin destruction rate, which we have good data from production data. However, it is not directly related to the polarization difference between two chambers.
· The fast time constant (~<1hour) is sensitive to the diffusion rate and polarization difference between two chambers. However, our online data usually do not contain good constrain to this, due to the reasons such as unknown initial polarization for spin up curves.
Therefore, I am proposing a fast time constant measurement at target lab, which do not require an good calibration of absolute polarization at target chamber. This measurement require a working cell in the oven and working target chamber NMR setup (NMR signal on pumping chamber is a plus).
The procedure (~24 hour total) are
1. Heat a Transversity cell or a similar cell to 230C @ oven. Turn on laser wait for equilibrium.
2. complete destruction of cell polarization
a. reduce NMR RF power to ~1% (Yi Qiang have the magic number) of normal used one.
b. Perform field sweep couple time to ensure complete destruction of NMR signal
3. spin up curve
a. perform a NMR field sweep every 30min
b. measure spin up curve for 3 spin up time (~15 hour total?)
4. Optional: perform EPR polarimetry on pumping chamber. This will help determine spin exchange rate, which is a correction term to diffusion rate when calculated from fast time constant. A cross calibration between EPR AFP and field NMR sweep is necessary.
5. An AFP loss test
a. Set identical NMR field sweep as spin up curve
b. Perform 5 NMR field sweep, 30 second apart.
After lots of email exchange with Georgios Laskaris at Duke, I found they have performed a spin up measurement from 0 polarization. And I was able to extract the diffusion rate from their data with a 20% stat. precision which is consist with my model calculation to same level.
email from George
Please check the Results and Discussion part and the Appendix B where we proved the time dependent equations for the polarization for the two volume cell taking into account the diffusion rates Gt and Gp. Actually, we measured also the diffusion rate from pumping to target chamber and it was ~50 min much shorter than the pumping time or the relaxation time.
http://www.jlab.org/~zwzhao/polhe3/doc/epja101183-offprints.pdf
measurement
test coil
230C oven, 230C pumping, 87.8, 48.3C, 37.8C target cell
4 ohm coil, 1-2w output, 0.5V source, 10cm close to target cell
Due to oven control PID setting is aggressive at P=??? , so the oven temperature is not very stable, fluctuate about 0.5C
1. NMR_He_20110709_132050, 10x120m, spin up
- before NMR_He_20110711_175209
- applying NMR_He_20110711_175520 (one way field sweep)
- after NMR_He_20110711_175635,NMR_He_20110711_175754,NMR_He_20110711_180036,NMR_He_20110711_181703 (12 times every 10 mins, with laser on)
test RF power
use different RF Power (Vrms) to do NMR, calculate H1 from resonance width, derive what the magic field H1 which destroys pol of Boris completely at 0.07Vrms
temperature: oven 210, pumping 212.7, target 81.7,38.2,45.1
- 3.2 NMR_He_20110713_182419
- 2.0 NMR_He_20110713_182547
- 1.0 NMR_He_20110713_182641
- 0.5 NMR_He_20110713_182748
- 0.2 NMR_He_20110713_182829
- 0.1 NMR_He_20110713_182925
- 3.2 NMR_He_20110713_183006
- 3.2 NMR_He_20110713_183041
