BEGIN:VCALENDAR VERSION:2.0 PRODID:IEEE vTools.Events//EN CALSCALE:GREGORIAN BEGIN:VTIMEZONE TZID:US/Eastern BEGIN:DAYLIGHT DTSTART:20200308T030000 TZOFFSETFROM:-0500 TZOFFSETTO:-0400 RRULE:FREQ=YEARLY;BYDAY=2SU;BYMONTH=3 TZNAME:EDT END:DAYLIGHT BEGIN:STANDARD DTSTART:20201101T010000 TZOFFSETFROM:-0400 TZOFFSETTO:-0500 RRULE:FREQ=YEARLY;BYDAY=1SU;BYMONTH=11 TZNAME:EST END:STANDARD END:VTIMEZONE BEGIN:VEVENT DTSTAMP:20201107T032052Z UID:5C127317-63B6-489B-B9A4-C3F176A7483A DTSTART;TZID=US/Eastern:20201027T090000 DTEND;TZID=US/Eastern:20201027T100000 DESCRIPTION:Sheaths are an essential aspect of most plasma-based technologi es because they determine how a plasma interacts with its surroundings. Th is talk will review a few recent advances in our understanding of how shea ths work [1]. Because sheath and presheath regions are often small compare d to collisional relaxation scales in low temperature plasmas\, the associ ated electric fields can cause a highly non-equilibrium state in which dif ferent species flow at dramatically different rates. Such differential flo ws provide an energy source that\, when strong enough\, can seed the excit ation of electrostatic instabilities. These waves have been shown to grow to large enough amplitude that they feedback and influence the overall tra nsport rates. Such behavior arises in a number of contexts. Ion-acoustic i nstabilities in the ion presheath have been observed to influence the ion velocity distribution function via wave- particle scattering. A similar in stability\, seeded directly by the electric field\, has been found to caus e the time-dependent Tonks-Langmuir problem to be unstable. Ion-ion two-st ream instabilities have been observed in the presheath of plasmas with ion ic mixtures\, and lead to an instability-enhanced friction force that infl uences the ion flow speeds. Flow-driven instabilities have also been found to play a prominent role in electron sheaths\, where an electron presheat h generates electron-ion two-stream instabilities that influence electron transport. Since these instabilities lead to observable changes in plasma transport\, they must be considered in order to accurately model plasma-bo undary interactions in a number of application areas.\n\n[1] S.D. Baalrud\ , B. Scheiner\, B.T. Yee\, M.M. Hopkins\, and E. Barnat\, Plasma Sources S cience and Technology 29\, 053001 (2020)\n\nCo-sponsored by: MIPSE\n\nSpea ker(s): Prof. Scott Baalrud\, \n\nAnn Arbor\, Michigan\, United States\, V irtual: https://events.vtools.ieee.org/m/245548 LOCATION:Ann Arbor\, Michigan\, United States\, Virtual: https://events.vto ols.ieee.org/m/245548 ORGANIZER:jordann@umich.edu SEQUENCE:1 SUMMARY:The Role of Plasma Instabilities in Sheath Physics URL;VALUE=URI:https://events.vtools.ieee.org/m/245548 X-ALT-DESC:Description: <br /><p>Sheaths are an essential aspect of most pl asma-based technologies because they determine how a plasma interacts with its surroundings. This talk will review a few recent advances in our unde rstanding of how sheaths work [1]. Because sheath and presheath regions ar e often small compared to collisional relaxation scales in low temperature plasmas\, the associated electric fields can cause a highly non-equilibri um state in which different species flow at dramatically different rates. Such differential flows provide an energy source that\, when strong enough \, can seed the excitation of electrostatic instabilities. These waves hav e been shown to grow to large enough amplitude that they feedback and infl uence the overall transport rates. Such behavior arises in a number of con texts. Ion-acoustic instabilities in the ion presheath have been observed to influence the ion velocity distribution function via wave- particle sca ttering. A similar instability\, seeded directly by the electric field\, h as been found to cause the time-dependent Tonks-Langmuir problem to be uns table. Ion-ion two-stream instabilities have been observed in the presheat h of plasmas with ionic mixtures\, and lead to an instability-enhanced fri ction force that influences the ion flow speeds. Flow-driven instabilities have also been found to play a prominent role in electron sheaths\, where an electron presheath generates electron-ion two-stream instabilities tha t influence electron transport. Since these instabilities lead to observab le changes in plasma transport\, they must be considered in order to accur ately model plasma-boundary interactions in a number of application areas. </p>\n<p>[1] S.D. Baalrud\, B. Scheiner\, B.T. Yee\, M.M. Hopkins\, and E. Barnat\, Plasma Sources Science and Technology 29\, 053001 (2020)</p> END:VEVENT END:VCALENDAR