1. The Study of Polarized 3
He Target Cell lifetime
Author: Peibo An1
Adviser: Todd Averett1
Sponsor: National Science Foundation
1Department of Physics, College of William & Mary, Williamsburg, VA 23187, USA
Abstract
The 3
He target cell polarized by spin-exchange optical pumping(SEOP) is
used as a neutron substitute to study the inner structure of the neutron
via electron scattering experiment. However once polarized, 3
He target cell
depolarizes itself exponentially. The lifetime of a cell is the decay constant
of the polarization. The typical lifetime of cells produced in our lab is about
22 hours. Longer lifetime indicates higher electron beam effective time and
thus reduces uncertainty. My work presents the study of cell lifetime
improvement. With a newly designed vacuum system where the base
pressure is as low as 10−8
torr and the new vacuum alkali ampoule that
promises alkali purity for cell production, we hope to see a longer cell
lifetime.
Experimental Setup
Cell Production
Spin-up&down Measurements
Conclusion
Given that the life time of cell Tom(tau) equals 2.69 hours and the average cell
lifetime in our lab is 22 hours, I successfully increase the cell lifetime by -88%. The
reason for such an absurd result is not well known. Possibly the polarization of my
cell was affected when we installed and tested our new EPR amplifier since
running EPR measurements will depolarize the cell for a moment. Also we do
suspect that the glass we used is not the best choice.
Acknowledgements
I would like to thank my adviser Dr. Todd Averett for mentoring me and sponsoring my trip. I’d like also to thank Dr. Wouter Deconinck , W&M physics
department and APS for covering my flight expense and lodging expense. This poster is based upon work supported by the National Science Foundation
under Grant No. PHY-1359364.
We use Nuclear Magnetic Resonance (NMR) to measure the
relative polarization of 3
He as a way to determine the time
constant as the polarization decays.[1] The lifetime or relaxation
time (tau) of 3
He is defined as the amount of time it needs to
decay its polarization by 63%.
The fitting equations we use are:
𝑆𝑝𝑖𝑛 − 𝑢𝑝: 𝑝 = 𝑝 𝑚𝑎𝑥 ∗ (1 − 𝑒
𝑡−𝑡0
−𝜏 )
𝑆𝑝𝑖𝑛 − 𝑑𝑜𝑤𝑛: 𝑝 = 𝑝 𝑚𝑎𝑥 ∗ (𝑒
𝑡−𝑡0
−𝜏 )
Theory
Oven baked to 180℃
The Pyrex tubing setup is above. We flow in nitrogen and helium separately. Once
a cell is filled we use liquid helium to cool it down to 4 kelvin.
Newly made vacuum system Rubidium ampoule.
Cell Tom placed inside the oven in the middle Rb 85 is also inside cell Tom but is not
included in the plot because my measurement
focuses on Rb 87. Cell Tom contains fewer Rb
compared to cell Jerry. However, cell Jerry
sacrificed himself during my first experiment.
Thus all my result is from cell Tom.
Reference
[1] K. Kluttz, Studies Of Polarized and Unpolarized 3
𝐻𝑒 In The Presence Of Alkali Vapor. Ph.D. Thesis, The College of William and Mary, 2012.