Present Status of the Reconstructed Large Mass Spectroscope

Abstract

After completely destroying the old large mass spectrograph by the high-tide typhoon in 1961, the reconstruction of a new large instrument, which has the quite similar dimensions in the main parts to the old one's, was planned. The machinery works of the main parts was finished in 1964, and their setting up works was begun in 1964 in the new building of our Science Faculty. The newly constructed large machine has the following points improved against the old one: in order to have better focus stabilities, the effective areas of the electric field and the main magnetic field are both somewhat extended; for eliminating charging up effect on the slit blades as much as possible, the blades can be baked. With the new machine, electric method can be used together with photographic method simultaneously, for measuring double mass differences. And, we call the new machine“the large double focusing mass-spectroscope”. The preliminary focus adjustment was carried out with photographic method. In this case, even in the best condition, the resolution obtained was only about 100, 000 or somewhat less, and in most cases it was only the half or one third of the above best valve. In order to find out this cause, the electric method was adopted. And as the results, the rather large a. c. stray magnetic field, filling in the room which affected the ion beam oscillation, was found. At present, as the results of eliminating such these stray magnetic field as much as possible, the half-width resolution of about 300, 000 has been obtained with the widths of main and collector slits of about 10μ Erespectively. In order to increase the absolute accuracy of doublet mass difference measurements, some preliminary experiments with electric method have been carried out. A few results obtained so far will be described in this report.