Telescope Built In City For I.G.Y. Work

Press, Volume XCV, Issue 28257, 20 April 1957, Page 4

Telescope Built In City For I.G.Y. Work

A meson telescope, built to the specifications of the special committee for the International Geophysical Year, has been designed by Mr C. A. Roper, a cosmic ray physicist at the Geophysical Laboratory in Christchurch. The staff of the laboratory completed the assembly of the telescope last Tuesday. It will be sent to the scientific station, specially built at Invercargill for the International Geophysical Year, where it will be one of the most important pieces of equipment at the station.

The aim of the meson'telescope is to measure how the intensity of cosmic rays varies at the surface of the earth—for short-term tests, in minutes, and for long-term tests, over some months. “Work on cosmic rays has given birth to many new ideas on nuclear fission,” said Mr Roper. “Physicists look on cosmic rays, as a good high-energy laboratory.” Source Not Known Mr Roper said that it was known what cosmic rays were, but not where they came from. “Some persons say they come from inside the solar system, and others say that almost all the rays come from outside it,” he said. “What we do know is that when there is an eruption on the sun and conditions are right, there is a large increase in the intensity of cosmic radiation measured on earth. This takes place at the most, two hours after the eruption. It is assumed, therefore, that some of the rays have come from the sun.” The meson telescope does not look like a telescope, but is similar to one in that it has a limited field of view. It records the variation of intensity of “mesons,”' the hard components of cosmic ladiation. Mr Roper said that primary radiation from outer space collided with atoms in the upper atmosphere, causing them to eject mesons as secondary particles. The number of mesons recorded by the telescope was, therefore, an indication of the intensity of the primary radiation. The direc-

tion in which the telescope was pointing gave perhaps a clue to the origin of the radiation. Three Trays The telescope had three trays above each other, each containing 10 geiger counters to measure the intesity of cosmic rays, Mr Roper said. Lead was placed above and below.the centre tray. As soon as the ionising particle (any fragment of an atom which carried a positive or negative charge) passed through the instrument, it set up a current which was recorded by instruments at the side of the telescope. If the three pulses from the trays took place within threemillionths of a second, it could be said that they were all caused by the passage through the three trays of one particle, he said. The physicist waits for a solar flare and compares its effect on the unshielded geiger counter, which admits low-energy cosmic rays, with that on the one shielded with lead.