Emissive sheath measurements in the afterglow of a radio frequency plasma

The difference between the plasma potential and the floating potential of a highly emissive planar surface was measured in the afterglow of a radio frequency discharge. A Langmuir probe was used to measure the electron temperature and an emissive probe was used to measure the spatial distribution of the potential using the inflection point in the limit of zero emission technique. Time-resolved measurements were made using the slow-sweep method, a technique for measuring time-resolved current-voltage traces. This was the first time the inflection point in the limit of zero emission was used to make time-resolved measurements. Measurements of the potential profile of the presheath indicate that the potential penetrated approximately 50% farther into the plasma when a surface was emitting electrons. The experiments confirmed a recent kinetic theory of emissive sheaths, demonstrating that late in the afterglow as the plasma electron temperature approached the emitted electron temperature, the emissive sheath ...

[1]  U. Czarnetzki,et al.  Electron cooling in decaying low-pressure plasmas. , 2012, Physical review. E, Statistical, nonlinear, and soft matter physics.

[2]  Shuichi Takamura,et al.  Effect of space-charge limited emission on measurements of plasma potential using emissive probes , 2000 .

[3]  A. Kudryavtsev,et al.  Modeling of nonlocal electron kinetics in a low-pressure afterglow plasma , 1998 .

[4]  N. Peacock,et al.  Plasma Diagnostics , 1972, Nature.

[5]  N. Hershkowitz,et al.  Kinetic theory of plasma sheaths surrounding electron-emitting surfaces. , 2013, Physical review letters.

[6]  L. A. Schwager.  Effects of secondary and thermionic electron emission on the collector and source sheaths of a finite ion temperature plasma using kinetic theory and numerical simulation , 1993 .

[7]  L. A. Schwager,et al.  Effects of cold electron emission on the plasma sheath , 1993 .

[8]  P. Kelly,et al.  Space and time resolved Langmuir probe measurements in a 100 kHz pulsed rectangular magnetron system , 2001 .

[9]  Yevgeny Raitses,et al.  Temperature gradient in Hall thrusters , 2003 .

[10]  T. Gyergyek,et al.  Fluid Model of a Sheath Formed in Front of an Electron Emitting Electrode Immersed in a Plasma with Two Electron Temperatures , 2005 .

[11]  P. Harbour,et al.  The influence of electron emission at the divertor target of a tokamak fusion reactor , 1978 .

[12]  J. K. Olthoff,et al.  The Gaseous Electronics Conference RF Reference Cell—An Introduction , 1995, Journal of research of the National Institute of Standards and Technology.

[13]  N. Hershkowitz,et al.  Mackenzie's Demon with instabilities , 2013 .

[14]  N. Hershkowitz,et al.  First experimental measurements of the plasma potential throughout the presheath and sheath at a boundary in a weakly collisional plasma. , 2002, Physical review letters.

[15]  Noah Hershkowitz,et al.  3 – How Langmuir Probes Work , 1989 .

[16]  J. Alami,et al.  Spatial and temporal behavior of the plasma parameters in a pulsed magnetron discharge , 2002 .

[17]  N. Hershkowitz,et al.  Inflection-point method of interpreting emissive probe characteristics. , 1979, The Review of scientific instruments.

[18]  J. P. Sheehan,et al.  Negative plasma potential in a multidipole chamber with a dielectric coated plasma boundary , 2012 .

[19]  H. Seiler,et al.  Secondary electron emission in the scanning electron microscope , 1983 .

[20]  J. P. Sheehan,et al.  A comparison of emissive probe techniques for electric potential measurements in a complex plasma , 2011, 2011 Abstracts IEEE International Conference on Plasma Science.

[21]  Alec D. Gallimore,et al.  Temporal limits of a rapidly swept Langmuir probe , 2010 .

[22]  N. Hershkowitz,et al.  The virtual cathode as a transient double sheath , 1988 .

[23]  A. Smolyakov,et al.  Breakdown of a space charge limited regime of a sheath in a weakly collisional plasma bounded by walls with secondary electron emission. , 2009, Physical review letters.

[24]  K. Riemann,et al.  The Bohm criterion and sheath formation , 1991 .

[25]  M. Endler,et al.  Density, temperature, and potential fluctuation measurements by the swept Langmuir probe technique in Wendelstein 7‐AS , 1994 .

[26]  R. K. Wakerling,et al.  The characteristics of electrical discharges in magnetic fields , 1949 .

[27]  Uwe Kortshagen,et al.  Experimental study of diffusive cooling of electrons in a pulsed inductively coupled plasma. , 2002, Physical review. E, Statistical, nonlinear, and soft matter physics.

[28]  David B. Graves,et al.  The Gaseous Electronics Conference radio‐frequency reference cell: A defined parallel‐plate radio‐frequency system for experimental and theoretical studies of plasma‐processing discharges , 1994 .

[29]  G. Chiodini,et al.  A 400 kHz, fast-sweep Langmuir probe for measuring plasma fluctuations , 1999 .

[30]  J. Wesson,et al.  RESEARCH NOTES: Heat flow through a Langmuir sheath in the presence of electron emission , 1967 .

[31]  M. Tan,et al.  Measurement of virtual cathode structures in a plasma sheath caused by secondary electrons , 2012 .

[32]  J. M. Sellen,et al.  Plasma Potential Measurements by Electron Emissive Probes , 1966 .