A 2450 Mhz Slab-Loaded Direct Contact Applicator with Choke
A Teflon-slab-loaded, direct contact microwave diathermy applicator has been developed. It produces minimal leakage radiation during effective heating of simulated planar tissue models. Because of TEM mode excitation, heating patterns are relatively uniform.
A comparative heating‐pattern study of direct‐contact applicators in microwave diathermy
Heating patterns, induced in planar and limb phantoms of simulated fat and muscle tissue by large and by small, direct-contact microwave diathermy applicators operating at 2.45 GHz, were studied. Teflon slab-loaded rectangular waveguides, circularly polarized horns, and other large radiators were investigated as well as the only two low-power direct-contact emitters presently in noninvasive clinical use. The integrity of temperature measurements by a thermographic camera was established and probe thermometry was used to compare polyethelene with a silk screen as the midplane phantom film. The width and depth of penetration of microwave heating were determined to evaluate energy deposition inside simulated muscle tissue. The results of temperature profiles show that a Teflon slab-loaded rectangular waveguide and a circularly polarized horn provide uniform heating in the center of the phantom's midplane and that the focusing effects of limb phantoms enhance depth of penetration. Measurements of the electric field demonstrated that direct-contact applicators can be designed to maintain leakage levels below 5 mW/cm2 per 100 watts of forward power for large applicators, and below 5 mW/cm2 per 10 watts of forward power for small applicators at a distance of 5 cm. Leakage of a circular aperture horn can be minimized with an output flange choke.
5.63 and 5.80 MeV levels of Ne20; de-excitation branching
Abstract The ratio Г γ /Г for the 5.63 and 5.80 MeV levels of Ne 20 has been determined to be 0.077 (±0.008) and −4 , respectively, by using the C 12 (C 12 , α)Ne 20 reaction and determining the fraction of the events in which the alpha-particle and the Ne 20 recoil are present in coincidence at the kinematically correct angles. In both cases these results in themselves are shown to imply radiative E1 transition (5.63→1.63 and 5.80→0, respectively) probabilities ⪡5 × 10 −5 Weisskopf units. When taken together with the life-time for the 5.63 MeV level measured by Evans et al . values of Г( E1 ) ≲ 5 × 10 −6 and Г α ≈ 6% of the particle estimate are obtained for this state.