Characterization and Control of an Ion-Acoustic Plasma Instability Downstream of a Diverging Magnetic Nozzle
The study and control of resonant instabilities in magnetized plasmas is of fundamental interest over a wide range of applications from industrially relevant plasmas to plasma sources for spacecraft propulsion. In this work electrostatic probes were employed to measure a 4–20 kHz instability in the...
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Frontiers Media S.A.
2020-02-01
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| Series: | Frontiers in Physics |
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| Online Access: | https://www.frontiersin.org/article/10.3389/fphy.2020.00024/full |
| _version_ | 1818313639127416832 |
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| author | Scott J. Doyle Alex Bennet Dimitrios Tsifakis James P. Dedrick Rod W. Boswell Christine Charles |
| author_facet | Scott J. Doyle Alex Bennet Dimitrios Tsifakis James P. Dedrick Rod W. Boswell Christine Charles |
| author_sort | Scott J. Doyle |
| collection | DOAJ |
| description | The study and control of resonant instabilities in magnetized plasmas is of fundamental interest over a wide range of applications from industrially relevant plasmas to plasma sources for spacecraft propulsion. In this work electrostatic probes were employed to measure a 4–20 kHz instability in the ion saturation current downstream of an electric double layer (DL) in an expanding helicon plasma source. The amplitude and frequency of the instability were found to vary in inverse proportion to the operating argon gas pressure (0.2–0.6 mTorr) and in direct proportion to the applied rf power (100–600 W) and applied solenoid current (3–8 A). A spatially resolved characterization of the maximum instability amplitude determined two radial maxima, corresponding to the locations of most positive radial ion density gradient. Control and inhibition of the instability were achieved through the application of a kHz voltage amplitude modulation to the 13.56 MHz radio-frequency (rf) power supplied to the helicon antenna. Through the application of voltage amplitude modulations in the frequency range 2–12 kHz the instability was reduced by up to 65%, exhibiting a greater reduction at higher applied modulation frequencies. This effect is described through a variation in the radial ion density gradient via asymmetrically attenuated ion acoustic density perturbations induced by the applied voltage modulation. The application of voltage amplitude modulations has been demonstrated as a potential control mechanism for density gradient driven instabilities in magnetized plasmas. |
| first_indexed | 2024-12-13T08:36:56Z |
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| issn | 2296-424X |
| language | English |
| last_indexed | 2024-12-13T08:36:56Z |
| publishDate | 2020-02-01 |
| publisher | Frontiers Media S.A. |
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| series | Frontiers in Physics |
| spelling | doaj.art-44c5aee4f2b54ed594852c913b7c5d1c2022-12-21T23:53:37ZengFrontiers Media S.A.Frontiers in Physics2296-424X2020-02-01810.3389/fphy.2020.00024513519Characterization and Control of an Ion-Acoustic Plasma Instability Downstream of a Diverging Magnetic NozzleScott J. Doyle0Alex Bennet1Dimitrios Tsifakis2James P. Dedrick3Rod W. Boswell4Christine Charles5Department of Physics, York Plasma Institute, University of York, York, United KingdomSpace Plasma, Power and Propulsion Laboratory, Research School of Physics and Engineering, The Australian National University, Canberra, ACT, AustraliaSpace Plasma, Power and Propulsion Laboratory, Research School of Physics and Engineering, The Australian National University, Canberra, ACT, AustraliaDepartment of Physics, York Plasma Institute, University of York, York, United KingdomSpace Plasma, Power and Propulsion Laboratory, Research School of Physics and Engineering, The Australian National University, Canberra, ACT, AustraliaSpace Plasma, Power and Propulsion Laboratory, Research School of Physics and Engineering, The Australian National University, Canberra, ACT, AustraliaThe study and control of resonant instabilities in magnetized plasmas is of fundamental interest over a wide range of applications from industrially relevant plasmas to plasma sources for spacecraft propulsion. In this work electrostatic probes were employed to measure a 4–20 kHz instability in the ion saturation current downstream of an electric double layer (DL) in an expanding helicon plasma source. The amplitude and frequency of the instability were found to vary in inverse proportion to the operating argon gas pressure (0.2–0.6 mTorr) and in direct proportion to the applied rf power (100–600 W) and applied solenoid current (3–8 A). A spatially resolved characterization of the maximum instability amplitude determined two radial maxima, corresponding to the locations of most positive radial ion density gradient. Control and inhibition of the instability were achieved through the application of a kHz voltage amplitude modulation to the 13.56 MHz radio-frequency (rf) power supplied to the helicon antenna. Through the application of voltage amplitude modulations in the frequency range 2–12 kHz the instability was reduced by up to 65%, exhibiting a greater reduction at higher applied modulation frequencies. This effect is described through a variation in the radial ion density gradient via asymmetrically attenuated ion acoustic density perturbations induced by the applied voltage modulation. The application of voltage amplitude modulations has been demonstrated as a potential control mechanism for density gradient driven instabilities in magnetized plasmas.https://www.frontiersin.org/article/10.3389/fphy.2020.00024/fullheliconmagnetized plasmasdouble-layerion-acoustic instabilityradio-frequency |
| spellingShingle | Scott J. Doyle Alex Bennet Dimitrios Tsifakis James P. Dedrick Rod W. Boswell Christine Charles Characterization and Control of an Ion-Acoustic Plasma Instability Downstream of a Diverging Magnetic Nozzle Frontiers in Physics helicon magnetized plasmas double-layer ion-acoustic instability radio-frequency |
| title | Characterization and Control of an Ion-Acoustic Plasma Instability Downstream of a Diverging Magnetic Nozzle |
| title_full | Characterization and Control of an Ion-Acoustic Plasma Instability Downstream of a Diverging Magnetic Nozzle |
| title_fullStr | Characterization and Control of an Ion-Acoustic Plasma Instability Downstream of a Diverging Magnetic Nozzle |
| title_full_unstemmed | Characterization and Control of an Ion-Acoustic Plasma Instability Downstream of a Diverging Magnetic Nozzle |
| title_short | Characterization and Control of an Ion-Acoustic Plasma Instability Downstream of a Diverging Magnetic Nozzle |
| title_sort | characterization and control of an ion acoustic plasma instability downstream of a diverging magnetic nozzle |
| topic | helicon magnetized plasmas double-layer ion-acoustic instability radio-frequency |
| url | https://www.frontiersin.org/article/10.3389/fphy.2020.00024/full |
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