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Title: A microwave resonator for limiting depth sensitivity for electron paramagnetic resonance spectroscopy of surfaces

A microwave Surface Resonator Array (SRA) structure is described for use in Electron Paramagnetic Resonance (EPR) spectroscopy. The SRA has a series of anti-parallel transmission line modes that provides a region of sensitivity equal to the cross-sectional area times its depth sensitivity, which is approximately half the distance between the transmission line centers. It is shown that the quarter-wave twin-lead transmission line can be a useful element for design of microwave resonators at frequencies as high as 10 GHz. The SRA geometry is presented as a novel resonator for use in surface spectroscopy where the region of interest is either surrounded by lossy material, or the spectroscopist wishes to minimize signal from surrounding materials. One such application is in vivo spectroscopy of human finger-nails at X-band (9.5 GHz) to measure ionizing radiation dosages. In order to reduce losses associated with tissues beneath the nail that yield no EPR signal, the SRA structure is designed to limit depth sensitivity to the thickness of the fingernail. Another application, due to the resonator geometry and limited depth penetration, is surface spectroscopy in coating or material science. To test this application, a spectrum of 1.44 μM of Mg{sup 2+} doped polystyrene 1.1 mm thickmore » on an aluminum surface is obtained. Modeling, design, and simulations were performed using Wolfram Mathematica (Champaign, IL; v. 9.0) and Ansys High Frequency Structure Simulator (HFSS; Canonsburg, PA; v. 15.0). A micro-strip coupling circuit is designed to suppress unwanted modes and provide a balanced impedance transformation to a 50 Ω coaxial input. Agreement between simulated and experimental results is shown.« less
Authors:
; ;  [1] ;  [1] ;  [2] ;  [3] ;  [4]
  1. Department of Biophysics, Medical College of Wisconsin, Milwaukee, Wisconsin 53211 (United States)
  2. (United States)
  3. Department of Radiation Oncology, University of Florida, Gainesville, Florida, 32610 (United States)
  4. Department of Radiology, Geisel Medical School at Dartmouth, Hanover, New Hampshire 03755 (United States)
Publication Date:
OSTI Identifier:
22305905
Resource Type:
Journal Article
Resource Relation:
Journal Name: Review of Scientific Instruments; Journal Volume: 85; Journal Issue: 10; Other Information: (c) 2014 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; ALUMINIUM; ANIMAL TISSUES; DOPED MATERIALS; ELECTRON SPIN RESONANCE; FINGERS; GHZ RANGE; IN VIVO; MICROWAVE RADIATION; POLYSTYRENE; RESONATORS; SENSITIVITY; SIMULATION; SPECTROSCOPY; SURFACE PROPERTIES; THICKNESS