The Study of Polarized Target Cell lifetimeAuthor: Peibo An1

Adviser: Todd Averett1

Sponsor: National Science Foundation1Department of Physics, College of William & Mary, Williamsburg, VA 23187, USA

AbstractThe 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, 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 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 ProductionSpin-up&down Measurements

ConclusionGiven 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.

AcknowledgementsI 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 as a way to determine the time constant as the polarization decays.[1] The lifetime or relaxation time (tau) of is defined as the amount of time it needs to decay its polarization by 63%.

The fitting equations we use are:))

Theory

Oven baked to

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 In The Presence Of Alkali Vapor. Ph.D. Thesis, The College of William and Mary, 2012.