The 14UD pelletron
The 14UD, in stand-alone operation since 1973, services seven well established beamlines plus three new ones in the LINAC Hall. It runs between 3500 and 5000 hour per year depending on competition from development projects and is operated by experimenters.
Ion sources include a NEC Multi-Sample SNICS and a Gas Cathode equipped SNICS II. These feed a high resolution injector system and a comprehensive pulsing system. The pulser boasts a programmable chopper which produces intervals of beam as short as 50 ps with repetition rates from sub microseconds to multi-milliseconds. A double gridded buncher, operating at 9.375 MHz, plus two harmonics, compresses the beam into pulses less than 1 ns wide at injection into the 14UD. Two orthogonal post acceleration choppers clean up the pulses. The phase detector is in front of the image slits of the energy analysing magnet.
The high voltage terminal of the 14UD includes a gas stripper differentially pumped by two turbopumps and two ion pumps. This is followed by the existing foil stripper and electrostatic triplet quadrupole lens. All terminal equipment is controlled via optical cable.
The 14UD routinely operates above 15.5 MV. The voltage performance upgrades include the installation of NEC compressed geometry accelerator tube, which increases the insulated length by 12%, and the local development of a robust resistor grading system for the column and tube.