1. Table Top Plasma Experiments
LANL Critical Skills Program
John Kline
July 10, 2002
P-24 Plasma Physics

2. Outline Why build small experiments? Different Table Top Experiments
Double Plasma Device
Waves and Instabilities
Non-Neutral Plasmas
Malmburg Penning Traps
RF Plasma
Capacitively Coupled
Inductively Coupled
Helicon Plasmas
Dusty Plasmas
Planetary Rings Experiments
Conclusions

3. Why build small plasma experiments?
Needs: That is all you need.
Costs: Every scientist knows that funding.
Proof of Principle: A small experiment used to prove concepts before building full scale experiments can be limited.

4. Proof of Principle DIIID Tokamak in San Diego
Operated by General Atomics

5. Proof of Principle These experiments study fusion directly
These experiments study RF current drive at WVU

6. Proof of Principle Experiments
The biggest draw back to small Proof of Principle experiments is scaling.
Do the experiments scale up in size?
Do the experiments scale up with the plasma parameters?
DIIID Tokamak n ~ 1 x 1015 cm-3, Te ~ 5 keV, Ti ~ 15 keV
WVU Tokamak n ~ 1 x 1013 cm-3, Te ~ 3-5 eV, Ti ~ eV

7. The Pickett’s Charge Plasma Device
Double Plasma Device
The Pickett’s Charge Plasma Device
At Gettysburg College

8. Double Plasma Device Biasing Grid Antenna for launching waves Filament
RF Power
Supply
Magnets

9. Double Plasma Device Plasma Parameters:
Plasma Densities of n ~ 1 x 109 – 1 x 1010 cm-3
Electron Temperatures of Te ~ 1 – 3 eV
Ion Temperatures of Ti ~ 0.2 – 0.3 eV
Ar Fill Pressure of No ~ 1 x 10-5 – 5 x 10-4 Torr

10. Space Plasma Physics Plasma Physics: Chaos and Nonlinear Dynamics
Potential Layers
Waves and Instabilities
Velocity Shear Driven
Drift Waves Bo
Velocity
Gyro-orbit size
Density
Diamagnetic
Current
Radius

11. Non-Neutral Plasmas
Most plasmas studied are quasi-neutral, i.e. ne ~Zni
Small electric fields, perturbations, arise only at microscopic levels due to plasma waves.
For Non-neutral plasmas, the plasma is made up of purely electrons or ions. This produces a net electric field in the plasma.
Plasma parameters:
Densities on the order of n ~ 1 x 106 – 1 x 109 cm-3 Temperatures of a few (1-2) eV
Fill Pressures of < 1 x 10-6 Torr

12. Non-Neutral Plasmas
Transport and Diffusion (neoclassical and classical)
Vortex formation and Plasma Crystals
Capturing of positrons and anti-protons
Auto-resonance studies

13. Malmberg Penning Traps

14. Malmberg Penning Traps
A) the outer cylindrical electrode, B) the inner cylindrical electrode, C) the grids, D) the annular collecting electrode and E) the filament.

15. Plasma Crystals

16. RF Plasma Discharge
Radio Frequency plasma sources use high power AC sources to generate a plasma.
There are three types of RF plasma sources: Capacitive, Inductive, and Helicon
Research areas:
Plasma Chemistry: For example control of N+, N2+, N, and N2; Break down of CH1 and CO2
Plasma Processing, both etching and deposition
Waves and instabilities
Textile processing
Bacterial removal

17. RF Plasma Discharge Plasma Parameters:
Typically operated at MHz; Many different fill gases.
Capacitive
Density on order of n ~ 1 x 108 to 1 x 1010 cm-3
Electron Temperature Te ~ 3 eV
Fill Pressure of No ~ 0.1 x 10-2 – 1.5 x 10-1 Torr
Inductive
Density on order of n ~ 1 x 109 to 1 x 1012 cm-3
Fill Pressure of No ~ 1 x 10-4 – 1 x 10-2 Torr (Atmospheric)
Helicon
Density on order of n ~ 1 x 1010 to 5 x 1013 cm-3
Electron Temperature Te ~ eV
Ion Temperature Ti ~ 0.05 – 1.0 eV

18. Capacitively Coupled Sources
(GEC Reference Cell)
Vacuum
Chamber
Matching
Network
RF Source
Plasma
Capacitor
Plates

19. Inductively Coupled Sources
Pyrex Chamber
Matching
Network
RF Source
Antenna
Magnets
(not required)
Alternative Antenna

20. Inductively Coupled Sources

21. Inductively Coupled Sources

22. Helicon Sources Matching Network RF Source Antenna Magnets (required)
Pyrex Chamber
Matching
Network
RF Source
Antenna
Magnets
(required)

23. Helicon Sources
Magnetically enhanced RF Plasma source with driving frequency between the ion and electron cyclotron frequencies: ci <<  < < ce< pe.
A helicon wave is “bounded” whistler, a right hand circularly polarized electromagnetic, wave. Wave propagation helps to enhance the density production.
Developed in 1970 by Rod Boswell looking for left handed circularly polarized waves.

24. Helicon Sources

25. Dusty Plasma Experiments
Because the presence of charged dust in plasma is relevant to environments ranging from industrial plasma process devices to the space plasma environment to the edges of fusion energy experiments, the study of dusty plasmas has recently become one of the fastest growing areas of plasma physics.
A dusty plasma is created by adding small particles (~ 10 um) to a plasma. The dust particles become charged and change the plasma dynamics, as well as, create a dynamical system of their own.

26. Dusty Plasma Experiments
Photomicrographs of a) glass microballoons and b) Minnesota Lunar Simulant (MLS-1), a simulated lunar soil. All samples were sieved to select a micron grain size. The frames are approximately 200 microns square.

27. Planetary Rings Experiment

28. Planetary Rings Experiment
A rotating magnet is used to generate a co-rotating electric field in the plasma.
If a cloud of microparticles is suspended in the vicinity of the rotating magnet, the electric field can cause the cloud to become extended into a ring-like structure.
Experiments will focus on studying the properties of driven and self-generated instabilities in the ring plane.

29. Saturn

30. Conclusions
There are many interesting and scientifically significant plasma physics experiments that can be done on a table top.
A well design and thought out experiment can be very productive.
Other small plasma experiments:
Glow discharge
Arc discharge
Hollow cathode
Plasma gun
Filament sources
Atmospheric plasma jets: for welding, material sprays, and contamination cleanup

31. Cloud vs. Stream Velocities
Comparison of particle speeds in the cloud and the stream. Particles in the stream have speeds, vst ~ 30 to 40 mm/s. Particles in the cloud have speeds up to vmax ~ 2 mm/s. Dust acoustic waves are also visible at the top of the cloud.
(The stream velocity vectors are shown in 3/8th scale relative to the cloud velocity vectors.)