Patent Number: 047572094
Section: description

DETAILED ACCOUNT OF WORKING EXAMPLE OF THE INVENTION One embodiment of the invention is shown diagrammatically in the drawing. In the housing 10, shown only in part, of a neutron chopper a rotor 12 is mounted that has two opposite windows 11. The rotor 12 is supported in bearings at its top end (not shown) and its lower end. The neutron beam 13 passes through a quartz window 14 into the evacuated rotor chamber 15, from which either passes through the windows 11 in the rotor 12 to the exit window 16 or is diverted by the wall of the rotor, dependent on the position of the rotor. The metering of the neutrons, which are to pass through the exit window 16, is dependent on the speed with which the rotor 12 rotates. Precise metering is brought about by placing a number of rotors 12 in series, the speeds of rotation thereof having to attain values of up to 50,000 rpm. The specification for the drive a correspondingly high. The drive to be seen in the drawing is in the form of hysteresis motor with a stator 18 and a drive rotor 19. The stator 18 is embedded in cast material 20 within the neutron chopper housing 10, which consists of an electrically insulating material, which is resistant to high vacuum and radiation. Concentrically placed within the stator there is a rotor 19 in the form of a hollow cylinder, which has its upper end shrunk onto a ring 21 of non-magnetic material. By screwing the ring 21 at 22 onto the floor of the rotor 12 the drive rotor 19 is joined to the chopper rotor 12. The hollow cylindrical form of the drive rotor 19 makes it possible to have a lower bearing 23 within the hollow cylinder near the low end of the chopper rotor so that it is not necessary to have a long and weighty rotor shaft.