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Title: Theoretical Investigation of an Inversely Conic Focusing Geometry for Sound Beams.


Abstract not provided.

Publication Date:
Research Org.:
Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA)
OSTI Identifier:
Report Number(s):
DOE Contract Number:
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of the Acoustical Society of America; Related Information: Proposed for publication in Journal of the Acoustical Society of America.
Country of Publication:
United States

Citation Formats

Younghouse, Steven Joseph. Theoretical Investigation of an Inversely Conic Focusing Geometry for Sound Beams.. United States: N. p., 2007. Web.
Younghouse, Steven Joseph. Theoretical Investigation of an Inversely Conic Focusing Geometry for Sound Beams.. United States.
Younghouse, Steven Joseph. Fri . "Theoretical Investigation of an Inversely Conic Focusing Geometry for Sound Beams.". United States. doi:.
title = {Theoretical Investigation of an Inversely Conic Focusing Geometry for Sound Beams.},
author = {Younghouse, Steven Joseph},
abstractNote = {Abstract not provided.},
doi = {},
journal = {Journal of the Acoustical Society of America},
number = ,
volume = ,
place = {United States},
year = {Fri Jun 01 00:00:00 EDT 2007},
month = {Fri Jun 01 00:00:00 EDT 2007}
  • The feasibility of producing continuous laser sparks (CLSs) with a resistance per unit length of 100 - 400 {Omega} cm{sup -1} by focusing radiation from CO{sub 2} laser with a conic mirror is demonstrated. The laser energy input per unit length required for this is experimentally found to be equal to {approx}200 J m{sup -1}. The possibility to efficiently control the trajectory of an electric discharge by means of a CLS is demonstrated. A CLS is found to be an analogue of a high-conductivity metal rod during the electric breakdown and electric potential transfer. The effect of polarity in themore » electric breakdown of air gaps between the CLS plasma channel and a metal rod is discovered and interpreted. The transverse structure of the CLS conductivity is investigated. Most likely the CLS conductivity at the initial stage is due to the photoionisation of air by the radiation of primary nuclei of the optical breakdown. (control of laser radiation parameters)« less
  • Purpose: Because the small-radius photon beams shaped by cones in stereotactic radiosurgery (SRS) lack lateral electronic equilibrium and a detector's finite cross section, direct experimental measurement of dosimetric data for these beams can be subject to large uncertainties. As the dose calculation accuracy of a treatment planning system largely depends on how well the dosimetric data are measured during the machine's commissioning, there is a critical need for an independent method to validate measured results. Therefore, the authors studied the model-based calculation as an approach to validate measured off-axis ratios (OARs). Methods: The authors previously used a two-component analytical modelmore » to calculate central axis dose and associated dosimetric data (e.g., scatter factors and tissue-maximum ratio) in a water phantom and found excellent agreement between the calculated and the measured central axis doses for small 6 MV SRS conic beams. The model was based on that of Nizin and Mooij [''An approximation of central-axis absorbed dose in narrow photon beams,'' Med. Phys. 24, 1775-1780 (1997)] but was extended to account for apparent attenuation, spectral differences between broad and narrow beams, and the need for stricter scatter dose calculations for clinical beams. In this study, the authors applied Clarkson integration to this model to calculate OARs for conic beams. OARs were calculated for selected cones with radii from 0.2 to 1.0 cm. To allow comparisons, the authors also directly measured OARs using stereotactic diode (SFD), microchamber, and film dosimetry techniques. The calculated results were machine-specific and independent of direct measurement data for these beams. Results: For these conic beams, the calculated OARs were in excellent agreement with the data measured using an SFD. The discrepancies in radii and in 80%-20% penumbra were within 0.01 cm, respectively. Using SFD-measured OARs as the reference data, the authors found that the calculated OARs were more accurate than those measured with a microchamber or film dosimetry. Conclusions: The model produces sufficiently accurate conic beam dosimetric data that can be used to validate direct measurement results for such beams.« less
  • The theoretical model of Schmidt (neglect of the energy loss), which for the transmission T of the BETA particles at large layer thicknesses x yields the-exponential law T ~ exp(-- mu x), where mu is the practical absorption coefficient, was discussed. The assumptions of the theory are not fulfilled for small x in isotropic angular distribution of the source electrons. For this case calculations were carried out by a decomposition of the BETA radiation into a diffusion part,'' for which the assumptions are approximately valid, and a side scattering part.'' The theoretical model of 0deblad (consideration of energy losses. neglectmore » of the backscattering) was studied approximately. From the results for medium x a relation of the practical absorption coefficient exists with the (medium) actual R/sub w/ of the electrons at the maximum energy of the BETA spectrum E/sub max/ and with the detour factor U. At large x a binomial law was derived for the transmission T: T ~ (1 -- x/R=/sub max/)/sup 3.21/-(R/sub max/ is the maximum range and l is the dimension for the width of the distribution of the apparent ranges of the electrons with energy E/sub max/). The theoretical results are discussed on the basis of measurements of transmission and backscattering. (tr-auth)« less