A 20 cm 100% transmission drift chamber with thin foil cathodes

A drift chamber with a drift space up to 20 cm long and a height of 6 cm has been constructed. The novel features of this chamber are, through the use of evaporated gold strips on a thin mylar foil instead of potential wires, a 100% transmission even for heavy ions and a minimum straggling outside the sensitive area through the use of helium as a 'buffer' gas. A position resolution of better than 0.8 mm fwhm has been obtained for 6-9 MeV alpha particles for normal, as well as inclined (600) incidence. The energy loss was approximately 320 keV with a resolution of 15% (50 keV), which was mainly determined by the straggling. (Auth.)