Plasma behaviour affected by a magnetic filter

Operation of magnetic filters is studied experimentally regarding their use for electron cooling in the sources of the negative hydrogen ion beams. Axial profiles of the plasma parameters-electron temperature and density-are measured by probe diagnostics in the expansion plasma region of an inductively driven tandem type of a plasma source. The obtained drop of the electron temperature down to values of about and below 1 eV required for efficient production of negative hydrogen ions is the result proving the proper operation of the filter. The mechanism of electron cooling is discussed based on thermal conductivity effects