Characterization and improvement of thin natural diamond detectors for spectrometry of heavy ions below 1Â MeV/amu

In our previous paper [V.Kh. Liechtenstein, N.V. Eremin, R. Golser, W. Kutschera, A.A. Paskhalov, A. Priller, P. Steier, Ch. Vockenhuber, S. Winkler, Nucl. Instr. and Meth. A 521 (2004) 203], first results on the evaluation of thin natural diamond-based detectors (NDDs) as an energy spectrometer for heavy ions in the energy range below 1 MeV/amu were presented. Although results were promising, the energy resolution of the detector was limited by an unexpected high-energy loss in the “dead layer” of the entrance window. In this paper, we report a significant improvement in the spectrometric properties of two highly selected and carefully treated NDDs with electrical contacts made of carbon and gold films as thin as about 10 and 20 μg/cm2, respectively, instead of much thicker aluminum contacts used before. In particular, for the NDD with thin carbon contact an energy resolution of 7.6% for 197Au-ions at 20.6 MeV was obtained. The energy cut-off of the detectors was reduced to 0.9 and 1.5 MeV for carbon and gold contact, respectively. The measured data on energy cut-off for different projectiles are compared with calculations, which yields an estimate of the thickness of the dead layers. Long-term irradiation runs proved stable spectroscopic performance of the detectors, in spite of the inherent “pumping” effects and imperfections of pulse height distributions. Our data suggest that NDD-based spectrometers might outperform other detector types in applications where very fast detectors with high radiation tolerance are required.