Mini-Tandem Accelerator

The Mini-Tandem Accelerator is a core feature of TUNL's Low-Energy Beam Accelerator Facility. It accepts H^- and D^- ion beams from TUNL's atomic beam polarized ion source and enables their acceleration from an initial energy of ~80 keV to energies as high as 480 keV. A publication describing this device, A Very Low Energy Tandem Accelerator, appeared in Nuclear Instruments and Methods in Physics Research A333 (1993) 239-243. The effort was a significant part of the doctoral thesis work of Timothy C. Black.

The Mini-Tandem is essentially a high-voltage dome, whose electrostatic potential can be varied continuously between 0 and +200 kV. Evacuated acceleration tubes allow the beam to enter and leave this dome, which surrounds a small evacuated chamber containing a thin carbon foil. Negative ions accelerated to the dome enter the chamber and pass through the foil, where they lose two electrons. They are then accelerated again when they emerge from the dome as positive ions. The name ‘tandem’ thus derives from the fact that the beam is accelerated twice … upon entering the dome, and then again upon leaving.

TUNL’s Low-Energy Beam Facility and mini-tandem accelerator have enabled unique studies of scattering and reactions in light nuclei with incident polarized and unpolarized beams, at energies between 50 and 500 keV which are typical of the most important reactions which are believed to have contributed to big-bang nucleosynthesis.