Measurement of laser heating in spin exchange optical pumping by NMR diffusion sensitization gradients

Journal Article · Sat May 15 00:00:00 EDT 2010 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.3371249· OSTI ID:21476198

Parnell, Steven R; Deppe, Martin H; Ajraoui, Salma; Parra-Robles, Juan; Wild, Jim M ^[1]; Boag, Stephen ^[2]

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1. Unit of Academic Radiology, University of Sheffield, Royal Hallamshire Hospital, Glossop Road, Sheffield, S10 2JF (United Kingdom)
2. ISIS, Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire, OX11 0QX (United Kingdom)

This paper details pulsed gradient NMR measurements of the {sup 3}He diffusion coefficient in sealed cells during spin exchange optical pumping. The potential of ultra low field magnetic resonance imgaing (MRI) and NMR for noninvasive measurement of cell pressure is demonstrated. Diffusion sensitization gradients allow measurement of the {sup 3}He diffusion coefficient from which the pressure and/or temperature of the gas can be determined during optical pumping. The pressure measurements were compared with neutron time of flight transmission measurements. Good agreement was observed between the temperature/pressure measurements and predictions based on Chapman-Enskog theory. The technique had sufficient sensitivity to observe the diffusion coefficient increasing with temperature in a sealed cell. With this method, evidence for laser heating of the {sup 3}He during optical pumping was found. The results show that NMR diffusion measurements allow noninvasive measurement of the cell temperature and/or pressure in an optical pumping setup. The method can be expanded using MRI to probe the spatial distribution of the diffusion coefficient. These techniques can be applied to the further investigation of polarization limiting effects such as laser heating.

• OSTI ID: 21476198
• Journal Information: Journal of Applied Physics, Vol. 107, Issue 9; Other Information: DOI: 10.1063/1.3371249; (c) 2010 American Institute of Physics; ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
CHAPMAN-ENSKOG THEORY
DIFFUSION
HELIUM 3
LASER-RADIATION HEATING
MAGNETIC FIELDS
NMR IMAGING
NUCLEAR MAGNETIC RESONANCE
OPTICAL PUMPING
POLARIZATION
POTENTIALS
PRESSURE MEASUREMENT
SENSITIVITY
SPATIAL DISTRIBUTION
SPIN EXCHANGE
TEMPERATURE MEASUREMENT
TIME-OF-FLIGHT METHOD
DIAGNOSTIC TECHNIQUES
DISTRIBUTION
EVEN-ODD NUCLEI
HEATING
HELIUM ISOTOPES
ISOTOPES
LIGHT NUCLEI
MAGNETIC RESONANCE
NUCLEI
PLASMA HEATING
PUMPING
RESONANCE
STABLE ISOTOPES