(Wednesday, 7/17/2019) 4:30 PM - 6:00 PM
Room: 304ABC
Purpose: To advance the fundamental mechanism study and quantification of radiobiological effects in particle-therapy in at subcellular level, we design and investigate electrostatic lens systems to focus MeV ion beams onto subcellular matrix with <100 nanometer spot size, in a compact (easily-aligned) and cost-effective format
Methods: The investigation was performed using the simulation tools of SIMION 8.1 (high accuracy but low efficiency) and GICOSY (contra). The numbers, lengths, intervals and excitation potentials of discretized lens and aperture-lens distance (DAL) under given incident beam conditions were studied and optimized. The performances of the optimized systems were compared with that of the state-of-the-art electrostatic quadrupole sextuplet (EQS) lens system, in terms of system length (Ls), working distance (Dw), demagnification factor (Df), chromatic and spherical aberrations.
Results: Two EQ lens systems composed of a triplet (EQT) and a quadruplet (EQQ) were obtained in our optimization for a 3 MeV/charge proton beam with beam diameter of 30 μm and angular divergence of6.7 μrad. Compared with the state-of-the-art EQS system, our optimized EQT system with three lenses fewer achieves ~4.7 folds shorter on Ls (0.84 m vs. 3.887 m), ~2.5 times larger on Df (95 vs. 38) and ~1.4 times longer on Dw (170.2 mm vs. 126 mm). They are ~4.7 folds shorter (0.86 m), ~0.87 fold smaller (33) and ~0.78 times shorter (98.3 mm) for the optimized EQQ system compared with EQS, respectively. For the EQT system, Df increased then decreased with an increasing DAL for input beam diameters of 30, 20, 9 and 6 μm. With 3-m DAL and 6μm input beam, a focusing beam spot of ~60 nm can be achieved.
Conclusion: The EQT design shows great potential to focus MeV ion beams to <100 nm scale to ultimately advance critical radiobiological studies for particle therapy.
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