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