MULTI DETECTOR INPUT AND FUNCTION GENERATOR FOR POLARIZED NEUTRON EXPERIMENTS

In this paper a VME module is described for static or stroboscopic mea surements with a neutron scattering instrument, consisting essentially of a series of up to 64 He-3 neutron detectors around a sample enviro nment. Each detector is provided with an amplifier and a discriminator to separate the neutrons from noise. To reduce the wiring, the discri minator outputs are connected to the module by coding boxes. Two 16-in puts to one-output coding boxes generate serial output codes on a fibe r optic connection. This basically fast connection reduces the dead ti me introduced by the coding, and the influence of environmental noise. With stroboscopic measurements a periodic function is used to affect the sample surrounded by a field coil. Each detected neutron is labele d with a data label containing the detector number and the time of det ection with respect to a time reference. The data time base can be pro grammed on a linear or a nonlinear scale. An external source or an att ribute of the periodic function may generate the time reference pulse, A 12-bit DAC connected to the output of an 8 K, 16-bits memory, where the pattern of the current has been stored before, generates the func tion. The function memory is scanned by the programmable function time base. Attributes are set by the four remaining bits of the memory. On e separate detector input connects a monitor detector in the neutron b eam with a 32-bit counter/timer that provides measuring on a preset co unt, preset time or preset frame. (C) 1998 Elsevier Science B.V. All r ights reserved.