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