a digitally controlled power supply for providing said accelerating voltage, said supply including {HEAD ~ means} for switching and accelerating {TAIL ~ voltage} between different levels; and 
for accelerating
a digitally controlled power supply for providing said accelerating voltage , said supply including { HEAD ~ means } for switching and accelerating { TAIL ~ voltage } between different levels ; and
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL OTH OTH REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH