Positron annihilation radiation profi le in aluminum was observed with a pair of Ge detectors in coincidence. 22Na was used as a source of positron and the two-dimensional gamma energy spectrum wasfi tted using a model function. Annihilation components of positron at rest with conduction band, 1s, 2s, and 2p electrons were observed. The in-flight positron annihilation was also observed. The model function also took into account the detector response function, relative effi ciency corrections and the gamma backscattering. Coincidences involving a combination of Compton effect, pileup, ballistic defi cit, and pulse shaping problems were treated as well.

This paper discusses some aspects of deconvolution of one-dimensional spectra in the framework of the Least Squares Method and presents a minimum variance regularization procedure. Covariance matrices are taken into account inevery step. Fluctuation and artifacts, both in the deconvolved and regularized spectra, are related to the structure of the covariance matrices. The method is applied to a simulated spectrum and to the 34S (gamma, <img src="http:/img/fbpe/bjp/v31n1/02eq05.gif">n) cross section determination from actual yield data.