Hope College Department of Physics and Engineering
Research Experiences for Undergraduates
Title: The installation of a new Van de Graaff Accelerator and its applications at Hope College
Name: Abe Pena
Home Institution: University of Texas – Austin
Research Advisor: Dr. Paul DeYoung, Dr. Graham Peaslee
Source of Support: NSF-REU
Recently Hope College received a grant from the NSF for a 1.7 MV Van de Graaff Accelerator. The accelerator installation began early June 2004. Experiments to be done with the new accelerator include particle induced x-ray emission (PIXE) and Rutherford backscattering (RBS). The system's main components consist of an ion source (H or He), a pelletron tandem, and three experimental stations (PIXE, microprobe, and general scattering)
In PIXE, near-particle collisions result in x-ray emission; the x-ray energies are determined with a SiLi detector. X-rays characteristic to different atoms produce signature peaks for each element giving the atomic constituents of the sample. PIXE will be applied to a variety of samples including sand, environmental specimens and dinosaur bones.
In RBS, energy loss of alpha particles traversing the sample and kinematics of the collisions determine various properties of recorded spectra. The peaks and edges in the energy spectrum allow one to know the thickness and composition of each element's layer in the sample. The particular energies observed are related to the depth of the elements in the sample. For example, thin layers will result in sharp peaks while thick layers result in wide peaks.