Cherenkov detector for cosmic ray detection

In a novel cherenkov detector carried on an artificial satellite for determination of the incident direction of heavy particles in cosmic rays, the back side of a luminous body in the detector is grooved in a checkered pattern to form a rough surface which decreases the degree of total reflection of the luminous body so that the light emitted by incident heavy particles having a velocity nearly equal to the light velocity impinges upon the back side of the luminous body at less than a critical angle of incidence. The luminous body is made of a metacrylic resin the front side of which is coated with a black paint consisting of a mixture of an acrylic resin with carbon black for forming an optically reflectionless surface exhibiting a high mechanical and thermal strength. Accordingly, visible radiation due to the incidence of the heavy particles is obtained with a high efficiency of detection and the detector containing this luminous body is suitable for use in outer space. (Ohno, Y.)