Investigation of core structures for the electron-beam reproducing head in magnetic recording

The relative advantages of perpendicular versus longitudinal recording have been re-evaluated in term of the electron-beam pickup. It is shown that dc response can be obtained only with perpendicular or transverse recarding, but because of other considerations longitudinal recording appears to be more generally practicable, even though the resulting low-frequency response limit depends upon the extent to which the physical dimensions of the core may , b e increased and the speed of the recording medium may be reducqd. Measurement techniques have been devised to permit study of the magnetic circuit parameters which influence over-all pickup sensitivity; associated studies show the advantages of a core structure having unconventional configuration and physical dimensions. Procedures recentlypresented by other writers for the investigation of factors contributing t o high-frequency loss in conventional heads have been tested with the electron-beam pickup; tape-coating thickness appears to be responsible fm, a decibel loss approximately equal to the total contributed by all other factors. Relatively simple striptype core structures for use with the electron-beam tube have been developed - over-all performance data under typical recording conditions show an output of the order of 0.2 volt and an equalized response range of approximately one to 15,000 cycles per second, plus or minus three decibels, at a tape speed of 10 inches per second.