Materials Characterization/Analysis and Ion-Beam Reactions


The Materials Characterization/Analysis and Ion-Beam Reactions Group [L. E. Seiberling, H. A. Van Rinsvelt, F. E. Dunnam, I. I. Kravchenko] has acquired a Model 5SDH Pelletron electrostatic accelerator from the Los Alamos Scientific Laboratory. The machine, used for only a few years by a geophysics research group, was declared surplus by LASL and acquired by us with assistance from the manufacturer National Electrostatics Corporation [NEC], our colleague Greg Stewart, and the New Physics Building Committee.


Pelletron® is a trademark of NEC and refers to the electrostatic charging mechanism invented by NEC's founder Professor Ray Herb of the University of Wisconsin. Instead of an insulated belt transporting a sprayed-on charge [as with a Van de Graaff® accelerator], an endless inductively-charged 'bead chain' of alternating nylon and aluminum links (the 'pellets') is employed, resulting in more rapid and efficient charge transfer. NEC machines hold the high-energy record for electrostatically (dc) accelerated ion beams.


Our 5SDH accelerator is a 1.7 MV horizontal, 'tandem' system designed to produce very stable beams at currents up to 200 nA. A tandem machine initially accelerates negative ions from a source at ground potential to the high voltage terminal potential +V. Inside the terminal the ions are made positive by stripping off electrons whereupon they are accelerated again. The maximum energy (in eV) for a completely stripped ion is thus (Z+1)V where Z is the ion's atomic number and V is the terminal potential. Our Pelletron thus produces proton or He+ beams of up to 3.4 MeV energy and He++ to 5.1 MeV. With ion source modifications, carbon and oxygen beams can be accelerated up to 11 MeV and 15 MeV, respectively.

The UF Pelletron is currently being installed in our laboratory [B2, NPB].


Here are two photographs of the UF Pelletron, taken by HAVR at Los Alamos in May:


Side View of the 5SDH Pelletron Accelerator. The white containment vessel is pressurized to approximately 100 psig with an insulating gas. Negative ions are injected at the left end (not in the picture), are stripped of electrons as they pass through the high-voltage terminal near the tank's center and are accelerated further before emerging through the stainless-steel Tee at the right end of the tank.

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End View of the Pelletron. The energetic ion beam emerges from the round flange in the background at right, passes through the analyzing magnet (white object near center) and is directed through one of five beam manifold exits (atop the blue table) into the experimental areas.

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Delivery of the Pelletron is scheduled for Monday 25 October. Acquisition costs were moving expenses of approximately $30,000. Current price of a new 5SDH Pelletron is $420,000.

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This versatile accelerator is a primary instrument in a research laboratory facility that will provide energetic ion beams as analytical probes for condensed matter investigations or to initiate nuclear and/or atomic reactions for further study. While it will be primarily employed in experiments designed by group members [see below] the facility will also be available to other investigators.

Research Group Members [for more details please refer to the home pages]:

L. E. Seiberling <>

Surface physics

Transmission Ion Channeling

Scanning Tunneling Microscopy


H. A. Van Rinsvelt <>

Trace Element Analysis Using PIXE and RBS

Nuclear microprobe investigations


F. Eugene Dunnam <>

Nuclear Spectroscopy

Cosmic-Ray Detector Development


I. I. Kravchenko <>

Atomic manipulation

X-ray photoemission spectroscopy

Thin film physics

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Last Updated 22 October 1999