THE X-RAY SOURCE CONTROL IS SHOWN ABOVE. A CAPTIVE 4 METER CABLE CONNECTS THIS TO THE SOURCE HEAD UNIT. THE CONTROL SUPPLIES FILAMENT HEATING CURRENT AND PROVIDES ELECTRON BEAM CONTROL THROUGH THE VARIABLE SELF-BIAS RESISTANCE. MONITORING OF THE HEATING CUMENT AND THE BEAM CURRENT IS ALSO PROVIDED. BECAUSE OF THE RISK OF HIGH-VOLTAGE TRANSIENTS APPEARING ON THESE CIRCUITS IN THE EVENT OF A VACUUM ACCIDENT, THE SOURCE CONTROL IS FULLY ENCLOSED AND THE CONTR0LS ARE INSULATED. IT IS RECOMMENDED THAT THE HIGH-VOLTAGE SUPPLY USED WITH THIS SOURCE BE A FULLY REGULATED AND PROTECTED TYPE SUCH AS A NUCLEAR DETECTOR BIAS SUPPLY.