This unit transitions from basic plasma observations to the industrial and research applications of plasma environments. You will learn to manage vacuum systems—a prerequisite for any plasma experiment—and study how plasma interacts with surfaces and external fields.
A Vacuum Pump (Rotary or Diffusion) is characterized by its pumping speed (S), which is the volume of gas removed from the system per unit time.
The speed is determined by observing the rate of pressure drop in a chamber of known volume (V).
Where P1 and P2 are the pressures at the beginning and end of time interval t. A plot of log(P) vs t yields a straight line from which S is calculated.
Paschen’s Law defines the Breakdown Voltage (Vb)—the voltage required to start a discharge or "spark" between two electrodes in a gas—as a function of the product of gas pressure (p) and distance between electrodes (d).
Key Observation: There is a unique minimum voltage (Vmin) at a specific value of p · d. Below this value, it's hard to find an electron; above it, electrons lose too much energy in collisions to cause ionization.
In a plasma, charged particles gyrate around magnetic field lines. A Magnetic Mirror is a configuration where the magnetic field is stronger at the ends of a region than at the center.
Particles with sufficient magnetic moment are reflected back toward the center of the region when they encounter the "stronger" field at the ends. This is a fundamental technique used in fusion research to keep high-temperature plasma away from reactor walls.
Plasma is used extensively in the semiconductor industry to modify surfaces at the nanometer scale.
Tip: In vacuum experiments, always clean the gaskets with Isopropyl Alcohol (IPA) and apply a very thin layer of high-vacuum grease (like Apiezon) to ensure a hermetic seal.