A terrella (“little earth”) is a permanent magnet mounted in a vacuum vessel.  The dipole field of the magnet is capable of confining a plasma.  This plasma can be considered as a toy model of the Earth’s magnetosphere.   Emphasis will be placed on making equipment in-house wherever possible. 

Available Experiments include:

 0)   Vacuum techniques and electrical hookup primer No prior knowledge of vacuum techniques associated with base pressures in the  1 mTorr range is assumed; participants will also receive basic training (if needed) in arranging appropriate grounds in a magnetically-confined plasma system.

1)  Diagnosis of plasma density and temperature with Langmuir probes  Participants will use a Langmuir probe to measure plasma density and temperature, and learn to differentiate Langmuir probe traces that are simple to analyze from those that are complicated .

2)  Diagnosis of plasma temperature with spectroscopy

Participants will learn how to use spectral line intensity ratios to estimate the plasma temperature.

3)  Microwave plasma experiments

Participants will explore the physics of microwave breakdown of magnetically-confined plasma.

Participants need not bring any special equipment to the Immersion. 

 SAFETY WARNING: Lethal voltages (~100 V) are present on exposed wires;  microwaves used in experiment 3.

COSTS

The cost of building a terrella comparable to the UW terrella from new parts would be over $10,000, the main costs being in the vacuum vessel and the turbo-pump needed to reach mTorr pressures.  A very low-cost alternative, comparable to a plasma ball, is under development and will be discussed at the Immersion.