Development and performance of a 129-GHz dynamic nuclear polarizer in an ultra-wide bore superconducting magnet

  • Lloyd L. Lumata
  • Richard Martin
  • Ashish K. Jindal
  • Zoltan Kovacs
  • Mark S. Conradi
  • Matthew E. Merritt
Research Article

DOI: 10.1007/s10334-014-0455-2

Cite this article as:
Lumata, L.L., Martin, R., Jindal, A.K. et al. Magn Reson Mater Phy (2015) 28: 195. doi:10.1007/s10334-014-0455-2

Abstract

Objective

We sought to build a dynamic nuclear polarization system for operation at 4.6 T (129 GHz) and evaluate its efficiency in terms of 13C polarization levels using free radicals that span a range of ESR linewidths.

Materials and methods

A liquid helium cryostat was placed in a 4.6 T superconducting magnet with a 150-mm warm bore diameter. A 129-GHz microwave source was used to irradiate 13C enriched samples. Temperatures close to 1 K were achieved using a vacuum pump with a 453-m3/h roots blower. A hyperpolarized 13C nuclear magnetic resonance (NMR) signal was detected using a saddle coil and a Varian VNMRS console operating at 49.208 MHz. Samples doped with free radicals BDPA (1,3-bisdiphenylene-2-phenylallyl), trityl OX063 (tris{8-carboxyl-2,2,6,6-benzo(1,2-d:4,5-d)-bis(1,3)dithiole-4-yl}methyl sodium salt), galvinoxyl ((2,6-di-tert-butyl-α-(3,5-di-tert-butyl-4-oxo-2,5-cyclohexadien-1-ylidene)-p-tolyloxy), 2,2-diphenylpicrylhydrazyl (DPPH) and 4-oxo-TEMPO (4-Oxo-2,2,6,6-tetramethyl-1-piperidinyloxy) were assayed. Microwave dynamic nuclear polarization (DNP) spectra and solid-state 13C polarization levels for these samples were determined.

Results

13C polarization levels close to 50 % were achieved for [1-13C]pyruvic acid at 1.15 K using the narrow electron spin resonance (ESR) linewidth free radicals trityl OX063 and BDPA, while 10–20 % 13C polarizations were achieved using galvinoxyl, DPPH and 4-oxo-TEMPO.

Conclusion

At this field strength free radicals with smaller ESR linewidths are still superior for DNP of 13C as opposed to those with linewidths that exceed that of the 1H Larmor frequency.

Keywords

Nuclear magnetic resonance Electron spin resonance Free radicals Hyperpolarization 

Copyright information

© ESMRMB 2014

Authors and Affiliations

  • Lloyd L. Lumata
    • 1
  • Richard Martin
    • 1
  • Ashish K. Jindal
    • 1
  • Zoltan Kovacs
    • 1
  • Mark S. Conradi
    • 2
  • Matthew E. Merritt
    • 1
    • 3
    • 4
  1. 1.Advanced Imaging Research CenterUniversity of Texas Southwestern Medical CenterDallasUSA
  2. 2.Department of PhysicsWashington UniversitySt. LouisUSA
  3. 3.Departments of Biomedical Engineering and Molecular BiophysicsUniversity of Texas Southwestern Medical CenterDallasUSA
  4. 4.Department of BioengineeringUniversity of Texas at DallasRichardsonUSA

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