High Resolution Magnetic Spectrometry

Abstract

I do not intend to speak about all possible types of spectrometers which are able to perform high resolution experiments at intermediate energies. Our first spectrometer SPESI gives a resolution of 6 10−5 in momentum at 1 GeV. It would be difficult to extrapolate the good features and difficulties of our spectrometer to other kinds of spectrometers (e.g. Los Alamos). I will describe two spectrometers which are actually in operation: SPES I, in routine operation since the end of 1972; SPES II in test operations and will be used for taking its first data in July 1975. A few other projects in intermediate energy spectroscopy at Saturne will be described at the end of this lecture (last but not least, the accelerator improvement program). This is necessary to obtain higher quality spectroscopic information. Low-energy nuclear physicists have used magnetic spectrometers for a long time and the “compensation-principles” have been known for more than two decadesA). The goals were, and still are, to construct a spectrometer system able to: analyze as accurately as possible the energy (in fact the momentum) of reaction products emitted from a target struck by a primary beam (resolution δp/p); utilize a large solid angle, which must be well defined independent of the magnitude of the momentum of the particles to be analyzed (Ω); measure the momenta inside a band as wide as possible (△P tot); focus analyzed particles in both transverse directions on an area as small as possible; be insensitive to the primary beam characteristics (emittance, momentum dispersion); have a large angular range; give high angular accuracy.