GYROMAGNETIC RESONANCE TECHNIQUE AND APPARATUS

• Main Author: ERWIN L. HAHN
• Format: Patent
• Language: English; French
• Published: 22.04.1958
• Subjects: INFORMATION STORAGE; PHYSICS; STATIC STORES

795,815. Electric digital-data-storage apparatus. INTERNATIONAL BUSINESS MACHINES CORPORATION. Jan. 14, 1955 [Jan. 18, 1954], No. 1210/55. Class 106 (1). In a " spin-echo " digital data storage device a sample of a crystalline substance (such as potassium chlorate) having an internal electric polarizing field is used as the storage element, thus obviating the necessity of an external polarizing field, as when a liquid is used as the storage element. In the preferred embodiment in order to increase the time for which phase memory can exist (transverse relaxation time) a small constant homogeneous magnetic field is applied to the sample 22, Fig. 3, by D.C. coils 33, 34. This field lowers the probability of neighbouring nuclei assuming the same spin frequency (by virtue of the phenomenon of Zeeman separation) and hence reduces interference between adjacent nuclei (spin-spin flipping) and thus increases the relaxation time. As described in Specification 795,057 in order to reduce power requirements the Larmor bandwidth may be varied, this being achieved by coils 39, 40. The idea of selectively entering data into a number of crystals having different resonant frequencies by frequency modulating the R.F. input signal is mentioned. As alternatives to entering data by R.F. signals are suggested the methods of positioning the crystal between the plates of a condenser or physically oscillating the crystal.