Privacy and Security Notice

Helicity scheme for E93027 run We are running in the traditional mode and NOT in the special HAPPEX mode with random helicity signal
and delayed pulse which identifies the helicity.  The signals come into Hall A counting house by  fiber optic cables from MCC. The optics cables come in to a rack in the middle room where they are transformed to NIM and NIM bar signals. Both the NIM signal and NIM bar  are each fed into a gate generator and delayed by
150  usecs and then the signal is fed into another gate generator, which gives a pulse with about 30 msec width.  The signals then go downstairs to the equipment aisle through patch 1H75B03, numbers 17+18. The signals are connected with 4 foot BNC cables to the patch panel to the hadron arm "nose",  through numbers 9+10. At the back of the detector stack, 10 foot BNC cable bring the signals to patch 161B, numbers D5+D6, which takes them upstairs to the top level of the stack.  Here the signal are feed into  gate generator and a gate width of about 33 msec is produced . The gap between plus and minus helicities is 270 usec which means that about 0.8% of the events will be undetermined polarization.  The helicity signals are anded with the RUN signal and this signal is sent as a gate to a scalar bank and to an ADC channel to be used to identify the helicity of the event.