  The operation principle and preliminary results of a novel gas-avalanche
patterned hole electron multiplier, the Thick-COBRA (THCOBRA), are presented.
This micro-hole structure is derived from the THGEM and MHSP. Sub-millimeter
diameter holes are mechanically drilled in a thin G10 plate, Cu-clad on both
faces; on one of the faces the Cu is etched to produce additional anode strips
winding between circular cathode strips. Primary avalanches occurring within
the holes are followed by additional ones at the anode-strips vicinity. Gains
in excess of 5*104 were reached with 22.1 x-rays in Ar, Ne and Ar-10%CH4, with
12.2 % FWHM energy resolution in Ar-10%CH4. Higher gains were measured with
single photoelectrons. This robust multiplier may have numerous potential
applications.
