WE have been developing during the past year an apparatus to make possible the study of neutrons of known energies within the thermal region. In principle, the apparatus consists of a device for producing a burst of neutrons lasting about 0.5 millisecond at intervals of 5 milliseconds. The source is surrounded by paraffin to slow the neutrons down to thermal energies, and these neutrons are then detected by a boron tri-fluoride chamber 5.4 metres away. The electrical pulses from the chamber are amplified and fed to a cathode ray oscillograph. Time signals are also received by the same amplifier and oscillograph whenever the bursts of neutrons occur. Since the neutrons take an appreciable time to cross the 5.4 metres between source and detector, a pulse from the chamber will be recorded later than the time signal corresponding to the burst which produced the neutron, and the distance between the two is inversely proportional to the velocity of the neutron. The traces on the oscillograph screen are photographed on a rapidly moving film, and the distances between the time marks and the pulses measured after development. From an analysis of these measured distances the velocity distribution of the neutrons can be inferred.

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neutrons oscillograph screen trifluoride chamber velocity distribution of cathode ray marks

F.FR P..MOON .P.HOMSON& C..WYNN-WAMS,.Velocity Distribution of Thermal Neutrons. 142 (3601),829-829.

F.FR P..MOON .P.HOMSON& C..WYNN-WAMS,"Velocity Distribution of Thermal Neutrons" 142

F.FR P..MOON .P.HOMSON& C..WYNN-WAMS,"Velocity Distribution of Thermal Neutrons"