The chopper module 1, wherein {HEAD ~ the plurality} of {TAIL ~ longitudinal channels} comprises four longitudinal channels 
of
The chopper module 1 , wherein { HEAD ~ the plurality } of { TAIL ~ longitudinal channels } comprises four longitudinal channels
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH