Beta and gamma ray studies of 144Ce and 207Bi

Abstract

A brief introduction on the scope of gamma ray spectroscopy is given in Chapter I, Chapter II deals with, the codification of the detecting system is of the prolate spheroidal field b-ray spectrometer (large spectrometer) and the medium size magnetic lens spectrometer (small spectrometer). The "Venetian blind" E.M.I photomultipliers previously used in both the spectrometers have been replaced by 36 a'VP photomultipliers and fast electronics using avalanche discriminator circuits.The NE 102 phosphors were replaced by the fast NE 104 scintillators. further improvement in the large spectrometer was made by replacing the conical phosphor and a straight light guide by an equiangular spiral light guide. Chapter IV describes the preparation of p-sources. An improved technique using the electrospraying method has been applied in the preparation of Th B and Ce sources. The coincidence measurements of 144Ce using the two spectrometers have been described in Chapter VI. But the most important and original contribution of this thesis is the e y coincidence measurements of 144Ce using the large spectrometer and a Go(Li) K-ray detector in con-junction. The e - y coincidence measurements have been described in Chapter VI. Very possibly a magnetic spectrometer and a Ge(Li) x-ray detector have been used for the first time time in these e - y coincidence measurements on 144Ce. The single y-ray spectra of 144Ce neasured with the 5 cc Ge(Li) detector and with X-ray detector are also described in this chapter. The use of a G-e(Li) X-ray detector in the e - y coincidence neasurenents of Ce has nade it possible to solve the ambiguities in the literature concerning sone low energy transitions and in the placing of the upper excited level in 144Pr The results can be talcen as the nost reliable ones obtained so far. Our results agree best with Geiger et al (1960,61). Chapter VII describes some (Tl)/Ge(Li) y - y coincidence measurenents of 207Bi and it is possible that these are the first measurenents on 207Bi with this type of equipment.