# Presentation: 076637

- LANL Critical Skills Program

- John Kline
- July 10, 2002

***P-24 Plasma Physics***

## 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

## 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.

## Proof of Principle

- DIIID Tokamak in San Diego
- Operated by General Atomics

## Proof of Principle

- These experiments study fusion directly

- These experiments study RF current drive at WVU

## Proof of Principle Experiments

-  Do the experiments scale up in size?
-  Do the experiments scale up with the plasma parameters?
- DIIID Tokamak *n* ~ 1 x 1015 cm-3, *T**e* ~ 5 keV, *T**i* ~ 15 keV
- WVU Tokamak *n* ~ 1 x 1013 cm-3, *T**e* ~ 3-5 eV, *T**i* ~ 0.3- 1.0 eV

## Double Plasma Device

- The Pickett’s Charge Plasma Device
- At Gettysburg College

## Double Plasma Device

- Plasma

- Magnets

- Filament

- Biasing Grid

- RF Power
- Supply

- Antenna for launching waves

## Double Plasma Device

-  Plasma Densities of  *n* ~ 1 x 109 – 1 x 1010 cm-3
-  Electron Temperatures of *T**e* ~ 1 – 3 eV
-  Ion Temperatures of *T**i* ~ 0.2 – 0.3 eV
-  Ar Fill Pressure of *N**o* ~ 1 x 10-5 – 5 x 10-4 Torr

## 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

- Radius

- Diamagnetic
- Current

## 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

## Non-Neutral Plasmas

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

## Malmberg Penning Traps

## 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.

## Plasma Crystals

## 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

## RF Plasma Discharge

- Plasma Parameters:
-  Typically operated at 13.56 MHz; Many different fill gases.
-  Capacitive
-  Density on order of *n* ~ 1 x 108 to 1 x 1010 cm-3
-  Electron Temperature *T**e* ~ 3 eV
-  Fill Pressure of *N**o **~ *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
-  Electron Temperature *T**e* ~ 3 eV
-  Fill Pressure of *N**o **~ *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 *T**e* ~ 3 - 5 eV
-  Ion Temperature *T**i* ~ 0.05 – 1.0 eV
-  Fill Pressure of *N**o* ~ 1 x 10-4 – 1 x 10-2 Torr (Atmospheric)

## Capacitively Coupled Sources

- Matching
- Network

- RF Source

- Plasma

- Capacitor
- Plates

- Vacuum
- Chamber

- (GEC Reference Cell)

## Inductively Coupled Sources

- Matching
- Network

- RF Source

- Pyrex Chamber

- Antenna

- Alternative Antenna

- Magnets
- (not required)

## Inductively Coupled Sources

## Inductively Coupled Sources

## Helicon Sources

- Matching
- Network

- RF Source

- Pyrex Chamber

- Antenna

- Magnets
- (required)

## 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.

## Helicon Sources

## Dusty Plasma Experiments

- 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.

- 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.

## 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 53-63 micron grain size. The frames are approximately 200 microns square.

## Planetary Rings Experiment

## 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.**

## Saturn

## 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

## Cloud vs. Stream Velocities

**Comparison of particle speeds in the cloud and the stream.   Particles in the ****stream**** have speeds, v****st**** ~ 30 to 40 mm/s.   Particles in the ****cloud**** have speeds up to  v****max**** ~ 2 mm/s.  ****Dust acoustic waves**** are also visible at the top of the cloud.**
**  **
**(The stream velocity vectors are shown in 3/8****th**** scale relative to  the cloud velocity vectors.)**