A 
neutron generator includes a sealed envelope providing a low pressure environment for a gas. One end of the envelope defines an 
ion source chamber. A target 
electrode is disposed at the other end of the envelope. An extracting 
electrode is spaced apart from the target 
electrode by an accelerating gap. The extracting electrode bounds the 
ion source chamber. A dispenser 
cathode electrode and grid electrode are disposed in the 
ion source chamber for inducing 
ionization in the 
ion source chamber. The dispenser 
cathode electrode, the grid electrode and the extracting electrode operate at a positive 
high voltage potential and the target electrode operates at or near ground potential. This configuration provides an 
electric field gradient that accelerates ions towards the target electrode to induce collisions of ions with target material, thereby causing fusion reactions that generate neutrons. 
High voltage power supply circuit means supplies a positive 
high voltage signal to the electrodes of the 
ion source. The positive 
high voltage signal has a 
low voltage signal component floating on a positive high 
voltage signal component. For the dispensing 
cathode electrode, the 
low voltage signal component can be a DC or AC signal suitable for emitting electrons from the dispensing 
cathode electrode. For the grid electrode, the 
low voltage signal component can be a positive pulsed-mode signal (preferably with magnitude in the range between 100 to 300 volts). 
High voltage insulation surrounds and electrically insulates the high 
voltage power supply circuit means. Other 
ion source electrode configurations, such as 
cold cathode (Penning) ion source and RF-driven ion source, can also be used.