CONTROL OF ELECTRON ENERGY DISTRIBUTIONS IN INDUCTIVELY COUPLED PLASMAS USING TA

CONTROL OF ELECTRON ENERGY DISTRIBUTIONS IN INDUCTIVELY COUPLED PLASMAS USING TA www.phwiki.com

CONTROL OF ELECTRON ENERGY DISTRIBUTIONS IN INDUCTIVELY COUPLED PLASMAS USING TA

Beamish, Jeff, Meteorologist has reference to this Academic Journal, PHwiki organized this Journal CONTROL OF ELECTRON ENERGY DISTRIBUTIONS IN INDUCTIVELY COUPLED PLASMAS USING TANDEM SOURCESMichael D. Logue (a), Mark J. Kushner(a), Weiye Zhu(b), Hyungjoo Shin(c), Lei Liu(b), Shyam Sridhar(b), Vincent M. Donnelly(b), Demetre Economou(b) (a) University of Michigan, Ann Arbor, MI 48109mdlogue@umich.edu, mjkush@umich.edu(b) University of Houston, Houston, TX 77204(c) Lam Research Corporation Fremont, CA 94538June 2013 Work supported by the DOE Office of Fusion Energy Science, SRC in addition to NSF.ICOPS-2013Control of electron energy distributions (EEDs)T in addition to em inductively coupled plasma (ICP) sourcesDescription of model in addition to geometryPlasma Parameters (Te, ne) during pulse periodfe() during pulse period fe() vs. position Concluding RemarksAGENDAICOPS-2013CONTROL OF EEDs – TANDEM SOURCESExternally sustained discharges, such as electron beam sustained discharges as long as high pressure lasers, control fe() by augmenting ionization so that fe() can be better matched to lower threshold processes. ICOPS-2013Based on this principle, the t in addition to em (dual) ICP source has been developed, T-ICPIn the T-ICP, the secondary source is coupled to the primary source through a grid to control the transfer of species between sources.The intent is to control fe() in the primary source.Computational results as long as a t in addition to em ICP system will be compared with experimental data under cw in addition to pulsed power conditions.

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DESCRIPTION OF HPEMModular simulator that combines fluid in addition to kinetic approaches.Resolves cycle-dependent phenomena while using time-slicing techniques to advance to the steady state.Electron energy distributions are obtained as a function of space, time using a Monte Carlo simulation.ICOPS-2013T-ICP has separately powered coils with a biasable grid separating the two source regions.Primary ICP is the lower source, secondary ICP is upper source.A biasable boundary electrode is at the top boundary.Electron, ion densities, temperatures: Langmuir probeArgon, 10 mTorr, 80 sccmTANDEM ICP (T-ICP): EXPERIMENTDimensions in cmICOPS-2013Cylindrically symmetric (mesh 8.7 cm x 58.5 cm)Operating conditions: Primary (lower): 90 W (CW)100 W (pulse average), Duty cycle = 20%, PRF = 10 kHzSecondary (top)Power = 100 W or 500 W (CW)Grounded grid.Argon, 10 mTorr, 80 sccmICOPS-2013TANDEM ICP (T-ICP): MODEL

ne, Se, Te (TOP 500 W, CW;BOTTOM 90 W, CW)With CW power top in addition to bottom in addition to grounded grid, the characteristics of the plasmas are determined by local coils.Dominant ionization regions are well separated, though high thermal conductivity of plasma spreads Te between sources.Grid Spacing: 3.12 mmArgon, 10 mTorr, 80 sccmICOPS-2013TeneElectron Source Presence of grid has noticeable influence on spatial profiles of ne, Te, in addition to VP near grid area.Grid Spacing: 3.12 mmICOPS-2013Te, ne, VP (TOP 500 W, CW; BOTTOM 90 W, CW)fe() (TOP 500 W, CW; BOTTOM 90 W, CW): H=10.8 cmfe() in middle of bottom ICP is substantially the same with or without top source. Perhaps some lifting of the tail of fe() with top source With only top source, high energy tail of fe() persists due to long mean free path of high energy electrons.Grid Spacing: 3.12 mm ICOPS-2013ExperimentICP (Bottom)ICP (Top)ICP (Both)Model

fe() (TOP 500 W, CW; BOTTOM 90 W, CW): H=14.8 cmICOPS-2013As height increases, tail of fe() rises as flux of high energy electrons from top source is larger.Grid Spacing: 3.12 mm Ar, 10 mTorrModelExperimentICP (Bottom)ICP (Top)ICP (Both)Te increases slightly in main ICP area late in the afterglow periodGrid Spacing: 3.12 mm ICOPS-201320s24s50s98s20s24s50s98sTe, ne, (TOP 500 W, CW; BOTTOM 100 W, PULSED)ANIMATION SLIDE-GIFTe (TOP 500 W, CW; BOTTOM 100 W, PULSED)With top ICP, Te increases in late afterglow. As plasma decays in bottom ICP, the constant flux of high energy electrons from top ICP has more influence. Result is sensitive to presence of grid, which would affect the transport of high energy electrons.Grid Spacing: 3.12 mm ; 5.46 mm Ar, 10 mTorr, H = 10.8 cm ExperimentICP (Bottom)ICP (Both)ICOPS-2013Model

In model ne = nine is little affected by presence of top ICP – changes occur dominantly in fe().Grid Spacing: 3.12 mm Ar, 10 mTorr, H = 10.8 cmne (TOP 500 W, CW; BOTTOM 100 W, PULSED)ExperimentICP (Bottom) neICP (Bottom) NiICP (Both) neICP (Both) NiICOPS-2013ModelICOPS-2013Top: 0 WBot: 90 W, CWfe() (TOP: 0 W, 500 W, CW; BOTTOM: 90 W, CW; 100 W PULSEDTop: 500 WBot: 90 W, CWTop: 0 WBot: 100 W, PulsedTop: 500 WBot: 100 W, PulsedEffect of top ICP on fe() has some height dependence, with the tail of fe() being raised higher as you move toward the top ICP.Grid Spacing: 5.46 mm fe() (TOP 0 W; BOTTOM 100 W, PULSED)Ar, 10 mTorr, H = 10.8 cm, PRF = 10 kHz, DC = 20%.Grid Spacing: 3.12 mm Modelfe() show expected time dependent behavior as long as a pulsed, single source systemfe() has long tail at t = 20 s near the end of the pulse on periodTail of fe() rapidly lowers in afterglow as high energy electrons are lost.Little change in fe() in late afterglow between t = 50 s in addition to t = 98 sICOPS-2013

Top ICP lifts the tail of the bottom fe() during afterglow with effect greatest late in the afterglow.Threshold of about 100 W in top ICP. (fe() as long as 100 W top ICP are not that different from 0 W. Some statistical noise at t = 50s)Ar, 10 mTorr, H = 10.8 cm, R = 0.5 cm, PRF = 10 kHz, DC = 20%.Grid Spacing: 3.12 mm Top 100 Wfe() (TOP CW; BOTTOM 100 W, PULSED): H=10.8 cmTop 500 WICOPS-2013As approach grid, significant lifting of the tail of the fe() tail as long as both top ICP 100 W in addition to 500 W Te of tail of distribution is larger at all times. Ar, 10 mTorr, H = 18.0 cm, R = 0.5 cm, PRF = 10 kHz, DC = 20%.Grid Spacing: 3.12 mm Top 100 WTop 500 Wfe() (TOP CW; BOTTOM 100 W, PULSED): H=18 cmICOPS-2013fe() (TOP 500 W, CW; BOTTOM ICP 100 W, PULSED)Similar trends in model in addition to experiment. Top ICP has little effect when bottom ICP is on but significant effect in afterglowAr, 10 mTorr, H = 10.8 cm, R = 0.5 cm, PRF = 10 kHz, DC = 20%.Grid Spacing: 3.12 mm ICOPS-2013ModelExperimentICP (Bottom) 24 sICP (Bottom) 98 sICP (Both) 24 sICP (Both) 98 s

CONCLUDING REMARKSThe use of a remote (top) ICP in t in addition to em with a primary ICP to modify the electron energy distributions in the primary source was investigated.When both sources have CW power (>90 W) the EEDs are dominated by the local power deposition. Top ICP power has little effect.The top ICP is able to modify the EEDs in a pulsed afterglow. The tail of the EED is lifted in the afterglow.The Te of the tail can be larger than the bulk – perhaps due to transport of less collisional, high energy electrons from the top ICP. These are also the electrons able to overcome the plasma potential of the top ICP in addition to penetrate the grid.ICOPS-2013Grid spacing has negligible effect on plasma parameters.Grid Spacing: 3.12 mm ; 5.46 mmICOPS-2013Te, ne, VP (TOP 500 W, CW; BOTTOM 90 W, CW)

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