A physical vapor deposition reactor includes a vacuum chamber with a sidewall, a ceiling and a retractable wafer support pedestal near a floor of the chamber, and a vacuum pump coupled to the chamber, the retractable wafer support pedestal having an internal electrode and a grounded base with a conductive annular flange extending from the base. A metal sputter target at the ceiling is energized by a high voltage D.C. source. The reactor has an RF plasma source power generator with a frequency suitable for exciting kinetic electrons is coupled to either the sputter target or to the internal electrode of the pedestal. A removable shield protects the sidewall and is grounded by plural compressible conductive tabs dispersed at generally uniform intervals on the annular flange and engaging a bottom edge of the shield whenever the retractable wafer support pedestal is in an unretracted position, each of the uniform intervals being less than a wavelength corresponding to the frequency of the RF plasma source power generator.