{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/100910"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/100910","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Physics of the helicon antenna on the prototype materials exposure experiment","abstract":"\"Proto-MPEX has been operating in a high-density “helicon-mode” of operation. The helicon mode of operation is classified by an increase in target on-axis electron density (6e19 m^-3) and a decrease in electron temperature (2 – 3 eV) during a helicon pulse. This transition is observed when Deuterium gas is puffed into the device and is dependent on operating configurations. The Proto-MPEX helicon antenna is a quarter turn right handed helical twist antenna powered by RF at 13.56 MHz and > 110 kW of power. Establishing plasma densities and magnetic field strengths under the antenna that suppress non-resonant mode conversion to the slow-wave are thought to be responsible for operating in the \"\"helicon-mode\"\". Evidence for this phenomena to be responsible for the \"\"helicon-mode\"\" of operation is presented. The experimental results showing evidence of this phenomena are presented here. First, we present time-resolved measurements of an edge-to-core power transition during a \"\"helicon-mode\"\" plasma pulse in the form of infra-red camera imaging of a thin stainless steel target plate. The time-resolved images measure the two-dimensional distribution of power deposition in the helicon discharge. The discharge displays a mode transition characterized by a significant increase in the on-axis electron density and core power coupling, suppression of edge power coupling and the formation of a fast-wave radial normal mode. Although the self-consistent mechanism that drives this transition is not yet understood, the edge-to-core power transition displays characteristics that are consistent with the discharge entering a slow-wave anti-resonant regime. RF magnetic field measurements made across the plasma column, together with the power deposition results, provide direct evidence to support the suppression of the slow-wave in favour of core plasma production by the fast-wave in a light-ion helicon source. A full wave model of the helicon antenna has been made in the finite element analysis software, COMSOL Multiphysics, to investigate the wave fields produced and the power deposition inside the Proto-MPEX device. Core electron density and magnetic field under the helicon is scanned while tracking core power deposition. The peaks of core power deposition in this parameter space are then investigated and the propagating modes are analyzed. These areas of increased core power deposition are then identified as helicon normal modes that are predicted to decrease edge coupling of power and increase core power coupling by suppressing the non-resonant mode conversion of the fast-wave to the slow-wave in the periphery of the plasma.\"","abstract_html":""Proto-MPEX has been operating in a high-density “helicon-mode” of operation. The helicon mode of operation is classified by an increase in target on-axis electron density (6e19 m^-3) and a decrease in electron temperature (2 – 3 eV) during a helicon pulse. This transition is observed when Deuterium gas is puffed into the device and is dependent on operating configurations. The Proto-MPEX helicon antenna is a quarter turn right handed helical twist antenna powered by RF at 13.56 MHz and > 110 kW of power. Establishing plasma densities and magnetic field strengths under the antenna that suppress non-resonant mode conversion to the slow-wave are thought to be responsible for operating in the ""helicon-mode"". Evidence for this phenomena to be responsible for the ""helicon-mode"" of operation is presented. The experimental results showing evidence of this phenomena are presented here. First, we present time-resolved measurements of an edge-to-core power transition during a ""helicon-mode"" plasma pulse in the form of infra-red camera imaging of a thin stainless steel target plate. The time-resolved images measure the two-dimensional distribution of power deposition in the helicon discharge. The discharge displays a mode transition characterized by a significant increase in the on-axis electron density and core power coupling, suppression of edge power coupling and the formation of a fast-wave radial normal mode. Although the self-consistent mechanism that drives this transition is not yet understood, the edge-to-core power transition displays characteristics that are consistent with the discharge entering a slow-wave anti-resonant regime. RF magnetic field measurements made across the plasma column, together with the power deposition results, provide direct evidence to support the suppression of the slow-wave in favour of core plasma production by the fast-wave in a light-ion helicon source. A full wave model of the helicon antenna has been made in the finite element analysis software, COMSOL Multiphysics, to investigate the wave fields produced and the power deposition inside the Proto-MPEX device. Core electron density and magnetic field under the helicon is scanned while tracking core power deposition. The peaks of core power deposition in this parameter space are then investigated and the propagating modes are analyzed. These areas of increased core power deposition are then identified as helicon normal modes that are predicted to decrease edge coupling of power and increase core power coupling by suppressing the non-resonant mode conversion of the fast-wave to the slow-wave in the periphery of the plasma."","abstract_has_math":false,"creators":["Piotrowicz, Pawel A."],"institution":"University of Illinois at Urbana-Champaign","degree_name":"M.S.","degree_level":"Thesis","degree_discipline":"Nuclear, Plasma, Radiolgc Engr","degree_department":null,"school":null,"contributors":["Ruzic, David N.","Curreli, Davide"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2018,"date_issued":"2018-09-04T20:26:43Z","date_published":"2018-09-04T20:26:43Z","updated_at":"2026-07-22T22:24:38Z","subjects":["helicon","plasma","radio-frequency","antenna"],"languages":["en"],"rights":["Copyright 2018 Pawel A. Piotrowicz"],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/2142/100910","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Ruzic, David N.","Curreli, Davide"]},{"key":"dc:creator","label":"Author","values":["Piotrowicz, Pawel A."]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2018-09-04T20:26:43Z","2018-03-26","2018-05"]},{"key":"dc:type","label":"Dc Type","values":["text"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Nuclear, Plasma, Radiolgc Engr"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Thesis"]},{"key":"thesis:degree_name","label":"Degree Name","values":["M.S."]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["University of Illinois at Urbana-Champaign"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["helicon","plasma","radio-frequency","antenna"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["en"]},{"key":"dc:rights","label":"Dc Rights","values":["Copyright 2018 Pawel A. Piotrowicz"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://hdl.handle.net/2142/100910"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["\"Proto-MPEX has been operating in a high-density “helicon-mode” of operation. The helicon mode of operation is classified by an increase in target on-axis electron density (6e19 m^-3) and a decrease in electron temperature (2 – 3 eV) during a helicon pulse. This transition is observed when Deuterium gas is puffed into the device and is dependent on operating configurations. The Proto-MPEX helicon antenna is a quarter turn right handed helical twist antenna powered by RF at 13.56 MHz and > 110 kW of power. Establishing plasma densities and magnetic field strengths under the antenna that suppress non-resonant mode conversion to the slow-wave are thought to be responsible for operating in the \"\"helicon-mode\"\". Evidence for this phenomena to be responsible for the \"\"helicon-mode\"\" of operation is presented. The experimental results showing evidence of this phenomena are presented here. First, we present time-resolved measurements of an edge-to-core power transition during a \"\"helicon-mode\"\" plasma pulse in the form of infra-red camera imaging of a thin stainless steel target plate. The time-resolved images measure the two-dimensional distribution of power deposition in the helicon discharge. The discharge displays a mode transition characterized by a significant increase in the on-axis electron density and core power coupling, suppression of edge power coupling and the formation of a fast-wave radial normal mode. Although the self-consistent mechanism that drives this transition is not yet understood, the edge-to-core power transition displays characteristics that are consistent with the discharge entering a slow-wave anti-resonant regime. RF magnetic field measurements made across the plasma column, together with the power deposition results, provide direct evidence to support the suppression of the slow-wave in favour of core plasma production by the fast-wave in a light-ion helicon source. A full wave model of the helicon antenna has been made in the finite element analysis software, COMSOL Multiphysics, to investigate the wave fields produced and the power deposition inside the Proto-MPEX device. Core electron density and magnetic field under the helicon is scanned while tracking core power deposition. The peaks of core power deposition in this parameter space are then investigated and the propagating modes are analyzed. These areas of increased core power deposition are then identified as helicon normal modes that are predicted to decrease edge coupling of power and increase core power coupling by suppressing the non-resonant mode conversion of the fast-wave to the slow-wave in the periphery of the plasma.\"","Submission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2018-08-31 without embargo terms","The student, Pawel Piotrowicz, accepted the attached license on 2018-03-19 at 14:38.","The student, Pawel Piotrowicz, submitted this Thesis for approval on 2018-03-19 at 14:49.","This Thesis was approved for publication on 2018-03-26 at 13:54.","DSpace SAF Submission Ingestion Package generated from Vireo submission #12072 on 2018-08-31 at 17:10:05","Made available in DSpace on 2018-09-04T20:26:43Z (GMT). No. of bitstreams: 6 PIOTROWICZ-THESIS-2018.pdf: 4399470 bytes, checksum: 2b6ebce64e8468a30c0657902afbc00b (MD5) Figures.zip: 6617502 bytes, checksum: 0059a830fb7da14f95fc1e086da30d94 (MD5) citations.bib: 434507 bytes, checksum: cb04743c7de9ad389a6d5046564c041f (MD5) thesis-ex.tex: 129216 bytes, checksum: c8086b77337f46fb022028494c499fbe (MD5) uiucthesis2014.cls: 16987 bytes, checksum: 77ebb07ddd664ade2c1d17883c88ef2f (MD5) LICENSE.txt: 4213 bytes, checksum: e6003a0af960cbc0c04a0eb6c44c8462 (MD5) Previous issue date: 2018-03-26"]},{"key":"dc:format","label":"Dc Format","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Physics of the helicon antenna on the prototype materials exposure experiment"]}]}],"canonical_facts":{"dc:contributor":["Ruzic, David N.","Curreli, Davide"],"dc:creator":["Piotrowicz, Pawel A."],"dc:date":["2018-09-04T20:26:43Z","2018-03-26","2018-05"],"dc:description":["\"Proto-MPEX has been operating in a high-density “helicon-mode” of operation. The helicon mode of operation is classified by an increase in target on-axis electron density (6e19 m^-3) and a decrease in electron temperature (2 – 3 eV) during a helicon pulse. This transition is observed when Deuterium gas is puffed into the device and is dependent on operating configurations. The Proto-MPEX helicon antenna is a quarter turn right handed helical twist antenna powered by RF at 13.56 MHz and > 110 kW of power. Establishing plasma densities and magnetic field strengths under the antenna that suppress non-resonant mode conversion to the slow-wave are thought to be responsible for operating in the \"\"helicon-mode\"\". Evidence for this phenomena to be responsible for the \"\"helicon-mode\"\" of operation is presented. The experimental results showing evidence of this phenomena are presented here. First, we present time-resolved measurements of an edge-to-core power transition during a \"\"helicon-mode\"\" plasma pulse in the form of infra-red camera imaging of a thin stainless steel target plate. The time-resolved images measure the two-dimensional distribution of power deposition in the helicon discharge. The discharge displays a mode transition characterized by a significant increase in the on-axis electron density and core power coupling, suppression of edge power coupling and the formation of a fast-wave radial normal mode. Although the self-consistent mechanism that drives this transition is not yet understood, the edge-to-core power transition displays characteristics that are consistent with the discharge entering a slow-wave anti-resonant regime. RF magnetic field measurements made across the plasma column, together with the power deposition results, provide direct evidence to support the suppression of the slow-wave in favour of core plasma production by the fast-wave in a light-ion helicon source. A full wave model of the helicon antenna has been made in the finite element analysis software, COMSOL Multiphysics, to investigate the wave fields produced and the power deposition inside the Proto-MPEX device. Core electron density and magnetic field under the helicon is scanned while tracking core power deposition. The peaks of core power deposition in this parameter space are then investigated and the propagating modes are analyzed. These areas of increased core power deposition are then identified as helicon normal modes that are predicted to decrease edge coupling of power and increase core power coupling by suppressing the non-resonant mode conversion of the fast-wave to the slow-wave in the periphery of the plasma.\"","Submission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2018-08-31 without embargo terms","The student, Pawel Piotrowicz, accepted the attached license on 2018-03-19 at 14:38.","The student, Pawel Piotrowicz, submitted this Thesis for approval on 2018-03-19 at 14:49.","This Thesis was approved for publication on 2018-03-26 at 13:54.","DSpace SAF Submission Ingestion Package generated from Vireo submission #12072 on 2018-08-31 at 17:10:05","Made available in DSpace on 2018-09-04T20:26:43Z (GMT). No. of bitstreams: 6 PIOTROWICZ-THESIS-2018.pdf: 4399470 bytes, checksum: 2b6ebce64e8468a30c0657902afbc00b (MD5) Figures.zip: 6617502 bytes, checksum: 0059a830fb7da14f95fc1e086da30d94 (MD5) citations.bib: 434507 bytes, checksum: cb04743c7de9ad389a6d5046564c041f (MD5) thesis-ex.tex: 129216 bytes, checksum: c8086b77337f46fb022028494c499fbe (MD5) uiucthesis2014.cls: 16987 bytes, checksum: 77ebb07ddd664ade2c1d17883c88ef2f (MD5) LICENSE.txt: 4213 bytes, checksum: e6003a0af960cbc0c04a0eb6c44c8462 (MD5) Previous issue date: 2018-03-26"],"dc:format":["application/pdf"],"dc:identifier":["http://hdl.handle.net/2142/100910"],"dc:language":["en"],"dc:rights":["Copyright 2018 Pawel A. Piotrowicz"],"dc:subject":["helicon","plasma","radio-frequency","antenna"],"dc:title":["Physics of the helicon antenna on the prototype materials exposure experiment"],"dc:type":["text"],"thesis:degree_discipline":["Nuclear, Plasma, Radiolgc Engr"],"thesis:degree_level":["Thesis"],"thesis:degree_name":["M.S."],"thesis:institution_name":["University of Illinois at Urbana-Champaign"]},"updated_at":"2026-07-22T22:24:38Z"}