All metal parts are water cooled in an
isolated manner. The hollow cathode was made from aluminum,
with a rectangular, elongated cross section. For our
tests, the slit runs vertical as one would use it in an in-line
vertical sputtering system; the dimensions of the cavity
were 197 mm height 54 mm depth 38 mm width. The
constriction was made from aluminum sheet metal in which
a 1-mm-wide 180-mm-long slit was machined. The choice of
the constriction material is not critical: in some preliminary
experiments, the constrictions were made from ceramic and
stainless steel.