[ { "id": "https://authors.library.caltech.edu/records/5qznw-5mm08", "eprint_id": 100195, "eprint_status": "archive", "datestamp": "2023-08-19 03:12:38", "lastmod": "2024-01-14 22:03:50", "type": "monograph", "metadata_visibility": "show", "creators": { "items": [ { "id": "George-N-A", "name": { "family": "George", "given": "Nick" } } ] }, "title": "Radiation Patterns of the Noise Emission from a Gaseous Discharge", "ispublished": "unpub", "full_text_status": "public", "note": "This research was supported by the U. S. Air Force through the Air Force Office of Scientific Research of the Air Research and Development Command, under Contract No. AF18(600)-1113. \n\nThe author wishes to acknowledge the many helpful discussions with C. H. Papas throughout the course of this work. Valuable consultation was also given by G. J. Stanley on radiometer principles and practices during the design of the equipment for the experiments. \n\nThe author wishes to express his appreciation to G. F. Smith who encouraged this work. This research was supported in part by a fellowship grant from the Hughes Aircraft Company.\n\n
Submitted - TR000403.pdf
", "abstract": "Theoretical and experimental radiation patterns are given in spectral form for the thermal radiation from a cylindrical discharge column which is adjacent to a long thin slot in a metallic plane. A spatial distribution is predicted which exhibits interference minima and maxima when the length of the slot and the wavelength of the emission are the same order of magnitude. The analysis is based on Maxwell's equations and the Leontovich-Rytov distributed-source generalization of Nyquist's noise formula.\n\nFraunhofer pattern measurements are presented in which an argon source is used to excite slots of 7.3\u03c0 and 9.5\u03c0 radians in length. Data are also presented to show the effects of variations in the pressure and the d-c current of the discharge. The pattern measuring apparatus is a Dicke radiometer having the following characteristics: frequency 9200 mc/s, bandwidth to the detector 16 mc/s, modulation frequency 1000 c/s, and residual noise level 0.3 rms\u00b0K.\n\nAn interference phenomenon is predicted by the theory and demonstrated by an experiment, even though the source excitation is spatially distributed and essentially uncorrelated in time and in space. The patterns are not even approximately Lambertian, e.g., a thin slot of 9.5\u03c0 radians exhibits a pattern having nine relative maxima in 180\u00b0 with the maximum emission at 63\u00b0 from the normal.", "date": "2019-12-06", "date_type": "published", "publisher": "California Institute of Technology", "id_number": "CaltechAUTHORS:20191204-174344884", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20191204-174344884", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "Air Force Office of Scientific Research (AFOSR)", "grant_number": "AF18(600)-1113" }, { "agency": "Hughes Aircraft Company" } ] }, "other_numbering_system": { "items": [ { "id": "TN-59-1101", "name": "AFOSR" } ] }, "local_group": { "items": [ { "id": "Caltech-Antenna-Laboratory" } ] }, "doi": "10.7907/BEXE-6F44", "primary_object": { "basename": "TR000403.pdf", "url": "https://authors.library.caltech.edu/records/5qznw-5mm08/files/TR000403.pdf" }, "resource_type": "monograph", "pub_year": "2019", "author_list": "George, Nick" }, { "id": "https://authors.library.caltech.edu/records/g9hn4-vdt86", "eprint_id": 99228, "eprint_status": "archive", "datestamp": "2023-08-19 03:18:01", "lastmod": "2024-01-14 21:59:39", "type": "monograph", "metadata_visibility": "show", "creators": { "items": [ { "id": "George-N-A", "name": { "family": "George", "given": "Nicholas" } } ] }, "title": "Spatial Distribution of Thermal Radiation at Microwave Frequencies", "ispublished": "unpub", "full_text_status": "public", "note": "Research supported by the U. S. Air Force Office of Scientific Research. \n\nThe author wishes to express his indebtedness to his advisor, Professor C. H. Papas, for his helpful suggestions, his stimulating criticisms, and his encouragement throughout all phases of this investigation. \n\nThe author wishes to acknowledge the following helpful discussions of specific topics. \n\nMr. G. D. Boyd, on gaseous discharge tubes Mr. H. H. Kuehl, on antenna theory Professor R. V. Langmuir, on experimental techniques Professor T. Lauritsen, on thermal radiation Professor H. C. Martel, on noise theory Dr. G. F. Smith, on experimental techniques Dr. G. J. Stanley, on radiometer design Mr. C. H. Wilcox, on noise theory. \n\nThanks are also extended to a colleague, H. Feiveson, who read the manuscript; Miss Benita von Klingspor, who prepared the figures; and Mrs. Ruth Stratton, who typed the text. The author is grateful for the generous financial support afforded him under the Howard Hughes Fellowship Program of the Hughes Aircraft Company.\n\nSubmitted - TR000399.pdf
", "abstract": "Theoretical and experimental radiation patterns are given in spectral form for the thermal radiation from thin slots or heated wires having dimensions of the order of the comparison wavelength. Maxwell's equations and noise theory form the basis of the analyses in which three independent methods are used to predict a spatial distribution which exhibits interference minima and maxima. In the first, the wave equation is solved for a noise-excited transmission line which is suddenly short- and open-circuited at alternate ends. By a study of the trapped noise currents, it is found that the radiation pattern has an interference structure which is smoothed as the loss is increased. Secondly, a formula is derived for the radiation pattern of a heated wire by a computation of its absorption in an isothermal enclosure and by an application of the principle of detailed balancing. Finally, the pattern of a long thin slot is computed directly using the Leontovich-Rytov distributed source generalization of Nyquist's noise formula.\n\nFraunhofer pattern measurements are taken for a thin slot excited by a gaseous discharge at 10,100 \u00b1 200\u00b0K. The pattern measuring apparatus is a Dicke radiometer having the following characteristics: frequency 9200 mc/s, bandwidth to the detector 16 mc/s, modulation frequency 1000 c/s, and residual noise level 0.3 rms\u00b0K.\n\nThe theory and the experiment demonstrate an interference phenomenon even though the source excitation is spatially extended and uncorrelated in time and space. The patterns are not even approximately Lambertian, e.g., a thin slot of 9.5\u03c0 radians length exhibits a pattern having nine relative maxima in 180\u00b0 with the maximum emission at 63\u00b0 from the normal.", "date": "2019-10-11", "date_type": "published", "publisher": "California Institute of Technology", "id_number": "CaltechAUTHORS:20191010-160710398", "official_url": "https://resolver.caltech.edu/CaltechAUTHORS:20191010-160710398", "rights": "No commercial reproduction, distribution, display or performance rights in this work are provided.", "funders": { "items": [ { "agency": "Air Force Office of Scientific Research (AFOSR)" }, { "agency": "Hughes Aircraft Company" } ] }, "other_numbering_system": { "items": [ { "id": "AD 217 179", "name": "ASTIA" } ] }, "local_group": { "items": [ { "id": "Caltech-Antenna-Laboratory" } ] }, "doi": "10.7907/RA1K-D737", "primary_object": { "basename": "TR000399.pdf", "url": "https://authors.library.caltech.edu/records/g9hn4-vdt86/files/TR000399.pdf" }, "resource_type": "monograph", "pub_year": "2019", "author_list": "George, Nicholas" } ]