Ultrasonic non destructive testing consists in emitting an acoustic wave in a material and then locating the reflected echoes produced by impedance changes, due to flaws or medium discontinuities. In some cases, echoes can overlap in the A-scan (typically for layered materials), yielding a difficult analysis: techniques such as matched filtering may fail and advanced techniques are necessary to locate the echoes. Sparse deconvolution methods have been recently applied to such problems. The challenge is to estimate a sparse sequence composed by the echoes locations (times of flight) and amplitudes. Usually, deconvolution is addressed by considering restoration at the acquisition sampling scale. This limits the precision of the spike location and may cause spike splitting. In this paper, we consider a high-resolution formulation of the deconvolution problem with a more precise restoration grid. To do so, we extend the approach proposed by Soussen et al. (IEEE Trans. Signal. Process, 2011) which minimizes a data misfit least-square criterion, penalized by a L0-norm term. The method has been tested on synthetic and experimental data. Compared to classical deconvolution algorithms, results show a better estimation of times of flight for a small increase of the computation time.