Tandem Van de Graaff Accelerator

Facility Contact: 

Eric Smith
(206) 616-3394
Doug Will
(206) 543-4489


Facility Description: 

CENPA has a High Voltage Engineering Corporation Model FN tandem Van de Graaff accelerator purchased in 1966 that has been in continuous use performing a wide variety of accelerator based experiments. In 1995 it was adapted to use an (optional) terminal ion source and a non-inclined tube #3, which enables the accelerator to produce high intensity beams of hydrogen and helium isotopes at energies from 100 keV to 7.5 MeV. The accelerator and its associated ion sources are operated and maintained by staff and students at CENPA. The graduate students and undergraduate hourly employees are trained to operate and service the ion sources and the accelerator in the facility. Experiments in nuclear physics and astrophysics for PhD thesis work as well as graduate and undergraduate projects are done annually using the accelerator. Outside users are also welcome and are frequently accommodated by the lab. Please contact us for rates and availability.

Laura Bodine - Tandem

Graduate student Laura Bodine making a modification to the implantation region of the beam line just off of the injector deck and down stream from the ion sources. She is installing an apparatus used to measure the dead layers of silicon surface barrier detectors using light ions (1H, 2H,3He, 4He) with energies from 10 to 60 keV.

Nora Boyd - Tandem

Nora Boyd, research engineer, tuning a negative deuteron beam from the direct extraction ion source (DEIS) on the elevated injector deck. The DEIS typically produces ion beams with energies around 45 keV. The platform on which she is standing will be elevated to 200kV to boost the ion velocity for injection into the tandem Van de Graaff accelerator.

Tandem Table

Several additional ion species are available including the following: Mg, Al, Si, P, S, Cl, Fe, Cu, Ge, Se, Br and Ag. Less common isotopes are generated from enriched material. We recently have been producing the positive ion beams of the noble gases He, Ne, Ar, and Kr at ion source energies from 10 keV to 100 keV for implantation, in particular the rare isotopes 21Ne and 36Ar. We have also produced a separated beam of 15-MeV 8B at 6 particles/second.

David Zumwalt - Tandem

Graduate student David Zumwalt attaching a diagnostics port to the molten lithium target chamber for the 6He experiment. In this chamber a 17.5 MeV deuteron beam is incident on molten lithium producing 6He through the reaction 7Li(2H, 3He)6He.

Jared Kofron - Tandem

Jared Kofron, a graduate student on the Project 8 neutrino experiment, tuning the tandem Van de Graaff accelerator from the control console. He is running a deuteron beam in tandem mode with the terminal at 8.8 MV. The negative ions leave the injector deck with an energy of 250 keV. The negative deuterons pick up 8.8 MeV on their way to the terminal where two electrons are stripped off. The positive deuterons pick up another 8.8 MeV on their trip away from the terminal. The total beam energy is the sum of the three, or 17.85 MeV.