(Tuesday, 7/16/2019) 7:30 AM - 9:30 AM
Room: Stars at Night Ballroom 1
Purpose: To demonstrate a method to irradiate human cancer cell lines using low energy proton, lithium, and carbon ion beams at the Argonne superconducting ion linac ATLAS. At beam energies of 10-15 MeV/u the ranges of these beams are ~1 mm so a method to spread out the Bragg peak (SOBP) to be ~0.3 mm wide is required.
Methods: The irradiations are done in air with the ion beams existing the vacuum of the beamline through a thin titanium window, passing through a set of 2 rotating absorber wheels to create the SOBP, and then passing through the various cell types. With the SOBP being ~0.3 mm deep, the cells are uniformly irradiated with doses of ~2-5 Gy. In this paper we describe the design and first implementation of the apparatus for creating the SOBP for such low energy ion beams. The SOBP is generated by using mylar absorbers of 0, 1, 2, and 3 layers of 6.4 micro-meters on one wheel and 0-10 layers of 25.4 micro-meters on the other wheel. The wheels rotate asynchronously to create the SOBP with ~3% uniformity averaged over ~100 seconds. Simulations using the Monte Carlo ion tracking code PHITS determined the total ions for each beam required to produce 2Gy irradiations.
Results: In the first irradiation run the beams used to cover a large range of linear energy transfer were 16-MeV protons, 60-MeV lithium, and 120-MeV carbon. The delivered doses were verified using gafchromic film to be in the range of 2 Gy.
Conclusion: We have developed a method to create a uniform SOBP to be used for low energy ion beam irradiations in fundamental cellular radio-biology research related to ion beam therapy.
Funding Support, Disclosures, and Conflict of Interest: Funded by the US DOE Office of Nuclear Physics Contract DE-AC02-06CH11357.
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