This year @UPMC, students in Physics (Third year of Bachelor’s degree – L3 & First year of Master’s degree « Physics & Applications » - M1) apprehend fundamental concepts of Plasma physics thanks to a new hands-on experiment called « Plasma discharges – Langmuir probe ». 

This Teaching Unit allows students to become familiar with fundamental processes in plasma physics.

 

  MG 2388 UPMC Pierre Kitmacher      MG 2402 UPMC Pierre Kitmacher

 Photo credit: ©UPMC-Pierre Kitmacher 

 

Learn more about this new hands-on experiment

 
 
A glow discharge is a plasma (ie. a gaz containing ions and free electrons thanks to an electric current). We focus here on discharge tubes commonly (and inacurrately) called "neon". These glass tubes are subjected to a very low air pressure. By pluging a high-voltage supply to the metal electrodes of the tube, we create a very high electrical potential (around a few hundred volts DC). From a « disruptive » value, a breakdown can be observed: the gas becomes conductive and releases a large number of electrons. Then, a plasma appears between the electrodes.


Student objectives:

  1. Students have to quantitatively measure the breakdown voltage of a tube under a given residual gas pressure; Then, students are able to verify the Paschen law.
  2. Students qualitatively study the light emitted by the plasma’s glow discharge (by image analysis) and highlight that inelastic electron/ion collisions are the source of this light emission.
  3. Students measure the floating electrostatic potential within the plasma and highlight the inhomogeneity of the electric field inside discharge (screening effects).
  4. The Langmuir probe allow them to measure the temperature of electrons in the plasma.
  5. A spectroscopic study help identify more precisely the ions and their excited states formed in the glow discharge.

This hands-on experiment was created in collaboration with INSP (Institut des NanoSciences de Paris) the experimental platform of the Physics Faculty @UPMC and the Cluster of Excellence PLAS@PAR.
More information about plasma physics education (summer school, grants for international internships, scolarships, etc) here.
 
 MG 2395 UPMC Pierre Kitmacher

Photo credit: ©UPMC-Pierre Kitmacher