Experimental study of proton scattering on carbon

Abstract

Measurement of inelastic scattering cross sections of 8 MeV protons on carbon has been carried out in the 30–170° angular range. The excitation functions for the 1.73 MeV-resonance have been measured in the 1–2 MeV energy range at 110°, 115° and 150°. Measurements of the excitation functions have been compared with previous measurements and Gurbich evaluation.

Introduction

Knowledge of proton scattering cross sections of carbon is important for the determination of carbon in materials, which cannot be analyzed through the proton induced X-ray emission (PIXE) technique. Rutherford back scattering spectrometry using alpha particle scattering is limited to its analysis mainly on the surface of samples. Ion beam analysis techniques based on proton scattering are more sensitive and capable of higher depth analysis. However the interaction of protons with carbon as for other light elements is non-Rutherford and proton scattering cross sections can not be accurately calculated. Therefore it is very important to have accurate proton scattering cross section data for accurate determination of carbon in materials relevant to modern technology. Earlier proton carbon scattering cross section measurements were carried out with a view to obtaining information on nuclear structure [1], [2], [3], [4], [5], [6]. The requirement for accurate proton scattering cross section data on carbon for IBA resulted in numerous reported measurements of excitation functions at backward angles [7], [8], [9], [10], [11], [12], [13], [14]. The availability of several proton-scattering data on the excitation functions at backward angles for light elements in general and for carbon in particular led Gurbich [15], [16], [17], [18] to undertake the evaluation of the data. On comparing the evaluation of proton carbon scattering data Gurbich [16] observed a discrepancy in the data of the 1.73 MeV-resonance at 110° and 115° below 1.8 MeV and recommended more measurements to resolve the discrepancy. Yasuda et al. [19] reported a more sensitive technique for carbon determination, which is based on the detection of 8 MeV protons in-elastically scattered in coincidence with 4.43 MeV gamma rays resulting from the de-excitation of the 4.43 MeV-state of ¹²C. Successful utilization of the technique will require measurements of the inelastic scattering cross sections of protons for this level at more angles. The excitation function is practically constant in the 7.6–8 MeV energy range in the backward direction in the 105°–140° angular range [4]. Thus the angular distribution of 8 MeV protons of this level will provide the excitation function for this level at a desired angle in this energy range. Therefore the inelastic differential scattering cross sections of 8 MeV protons on carbon have been measured in the 30°–170° angular range. The measurements of excitation functions for the 1.73 MeV resonance of carbon at 110°, 115° and 150° have been carried out to resolve the discrepancy reported by Gurbich [16]. The measurements have been compared with previous measurements and Gurbich evaluation [16].