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Title: Optical pumping production of spin polarized hydrogen

Abstract

There has been much interest recently in the production of large quantities of spin polarized hydrogen in various fields, including controlled fusion, quantum fluids, high energy, and nuclear physics. One promising method for the development of large quantities of spin polarized hydrogen is the utilization of optical pumping with a laser. Optical pumping is a process in which photon angular momentum is converted into electron and nuclear spin. The advent of tunable CW dye lasers (approx. 1 watt) allows the production of greater than 10/sup 18/ polarized atoms/sec. We have begun a program at Princeton to investigate the physics and technology of using optical pumping to produce large quantities of spin polarized hydrogen. Initial experiments have been done in small closed glass cells. Eventually, a flowing system, open target, or polarized ion source could be constructed.

Authors:
; ;
Publication Date:
Research Org.:
Princeton Univ., NJ (USA). Plasma Physics Lab.
OSTI Identifier:
6391479
Report Number(s):
PPPL-2125
ON: DE85002130
DOE Contract Number:
AC02-76CH03073
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; HYDROGEN; POLARIZATION; SPIN ORIENTATION; THERMONUCLEAR FUELS; DYE LASERS; OPTICAL PUMPING; ELEMENTS; FUELS; LASERS; LIQUID LASERS; NONMETALS; ORIENTATION; PUMPING; 700205* - Fusion Power Plant Technology- Fuel, Heating, & Injection Systems

Citation Formats

Knize, R.J., Happer, W., and Cecchi, J.L. Optical pumping production of spin polarized hydrogen. United States: N. p., 1984. Web. doi:10.2172/6391479.
Knize, R.J., Happer, W., & Cecchi, J.L. Optical pumping production of spin polarized hydrogen. United States. doi:10.2172/6391479.
Knize, R.J., Happer, W., and Cecchi, J.L. 1984. "Optical pumping production of spin polarized hydrogen". United States. doi:10.2172/6391479. https://www.osti.gov/servlets/purl/6391479.
@article{osti_6391479,
title = {Optical pumping production of spin polarized hydrogen},
author = {Knize, R.J. and Happer, W. and Cecchi, J.L.},
abstractNote = {There has been much interest recently in the production of large quantities of spin polarized hydrogen in various fields, including controlled fusion, quantum fluids, high energy, and nuclear physics. One promising method for the development of large quantities of spin polarized hydrogen is the utilization of optical pumping with a laser. Optical pumping is a process in which photon angular momentum is converted into electron and nuclear spin. The advent of tunable CW dye lasers (approx. 1 watt) allows the production of greater than 10/sup 18/ polarized atoms/sec. We have begun a program at Princeton to investigate the physics and technology of using optical pumping to produce large quantities of spin polarized hydrogen. Initial experiments have been done in small closed glass cells. Eventually, a flowing system, open target, or polarized ion source could be constructed.},
doi = {10.2172/6391479},
journal = {},
number = ,
volume = ,
place = {United States},
year = 1984,
month = 9
}

Technical Report:

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  • We have produced highly spin-polarized atomic hydrogen by spin-exchange optical pumping. A tunable ring dye laser is used to polarize rubidium atoms by optical pumping. The cell containing the rubidium vapor is coated with paraffin in order to reduce spin relaxation due to wall collisions. Hydrogen gas is dissociated in an inductive discharge and flows continuously through the cell, in which the hydrogen atoms are polarized by spin-exchange collisions with the polarized rubidium atoms. Atomic-hydrogen polarization as high as 2{l angle}{ital J}{sub {ital z}}{r angle}{sub H}=0.72(6) has been observed, which is the highest polarization yet produced by this method. However,more » the rubidium polarization may be limited to this value due to radiation trapping at higher rubidium densities. The spin-relaxation rate of atomic hydrogen on a paraffin-coated cell is also measured and corresponds to about 7600 wall bounces between wall relaxation.« less
  • The development and application of an optical pumping and photoluminescence experiment for electron spin polarization measurements on semiconductor photocathode materials are described. The spin polarization increase that is produced by applying a uniaxial compression to a gallium arsenide crystal and selectively optically pumping the transition between the upper strain-split valence band and the conduction band is discussed. The electron spin polarization is measured by analyzing the circular polarization of the photoluminescence. The relation between luminescence and spin polarizations is given by P/sub sigma/ = P/sub h/P/sub s//tau/sub s//tau/sub s/ + tau/sub r// where P/sub sigma/ is the luminescence circular polarization,more » P/sub s/ is the spin polarization, and P/sub h/ is the hole coupling factor. For band edge excitation P/sub h/ is identical to P/sub s/. In this expression, tau/sub s/ and tau/sub r/ are the spin relaxation and luminescence recombination times, respectively. From our data we infer an increase in P/sub s/ from 50% at zero stress to 70% for an applied (001) stress of 4.0 x 10/sup 9/ dyn cm/sup -2/ in a 1 x 10/sup 18/ p-type GaAs crystal at T = 100/sup 0/K. For comparison, the maximum theoretical polarization at infinite stress is 80%. Results show that the observed increase in polarization can be fit to a model function of the ratio delta/sub s//E/sub k/ where delta/sub s/ is the strain splitting energy and E/sub k/ is the energy of the initial valence state measured from the band edge. For band edge excitation the best-fit value for E/sub k/ of 0.017 eV agrees reasonably well with the calculated value of V/sub rms/, the rms potential energy fluctuation of the band edge due to the ionized impurity potentials. From the known dependence of V/sub rms/ on doping and temperature, device operating curves are proposed which predict the relation between spin polarization and applied stress for various values of impurity concentration p and temperature T.« less
  • A novel laser-driven polarized source of hydrogen and deuterium which is based on the principle of spin-exchange optical pumping has been developed at Argonne. The advantages of this method over conventional polarized sources for internal target experiments is discussed. At present, the laser-driven polarized source delivers hydrogen 8{times}10{sup 16} atoms/s with a polarization of 24% and deuterium at 6{times}10{sup 16} atoms/s with a polarization of 25%. A passive storage cell for polarized deuterium was tested in the VEPP-3 electron storage ring. The storage cell was found to increase the target thickness by approximately a factor of three and no lessmore » in polarization was observed.« less
  • A novel laser-driven polarized source of hydrogen and deuterium which is based on the principle of spin-exchange optical pumping has been developed at Argonne. The advantages of this method over conventional polarized sources for internal target experiments is discussed. At present, the laser-driven polarized source delivers hydrogen 8 x 10 W atoms/s with a polarization of 24% and deuterium at 6 x 10 W atoms/s with a polarization of 25%. A passive storage cell for polarized deuterium was tested in the VEPP-3 electron storage ring. The storage cell was found to increase the target thickness by approximately a factor ofmore » three and no loss in polarization was observed. 10 refs., 4 figs., 2 tabs.« less