Neutron Scattering

Figure 10 .7 : Disc chopper .
10% than 1% . A reduction of the window site would not help to improve this ratio,
silice that would also impose a reduced beam width on the system which would reduce
the available intensity to an unacceptable level . To achieve nevertheless a reasonable
temporal resolution wich the required pulse-pulse distance (to avoid "frame overlap"),
it is necessary to combine several dise choppers where slow choppers select only one of
several openings of faster ones (rotating with a integer multiple n of the pulse repetion
frequency S2) . The resulting pulse bas -according to the higher rotation frequency nQ- a
length which is shorter by a factor 1/n . Also counter rotating dises are employed . The
multiple dise chopper technique requires exact electronic control of the relative rotation
phases of the choppers .
10- 12