Patent ID: 8069001

Claim:
A system for estimating in-depth thermal response that is correlated to shape of a surface that is undergoing ablation, the system comprising: a layer of electrically insulating material provided in a cylindrically shaped tube having a hollow inner core and having a longitudinal axis; first and second helices of electrically resistive wire material, surrounding the tube along the longitudinal axis, inter-wound with each other in a parallel sense, each helix having a first end, having approximately the same length L(t), having first and second electrical resistivities, ρ1 and ρ2, separated from each other by a small distance, and having an insulation layer extending between the first and second helices; an electrical current source connected adjacent to one of the first ends of the first and second helices; a voltmeter connected between the first ends of the first and second helices, to provide a measurement of at least one voltage difference V1(t), as a function of time between the first and second helices, for at least one time, t=t1, as the length L(t) changes in response to recession of the tube; and a numerical processor that receives the at least one voltage difference value, V1(t1), and provides an estimate of the length value L(t) of at least one of the first and second helices at the time t1, based upon the voltage difference V1(t1); where a portion of the insulation layer material undergoes charring at high temperature and becomes electrically conducting in a charred state at a second end of each of the first and second helices.