The beam must be extracted into the air through the vacuum window to irradiate the living cell.In the window design,the material and thickness must be chosen to compromise the beam spot size broadening and the window safety.The structure-static analysis on the window of different structures and materials is done with the finite element analysis method,and the deformation and the equivalent stress are simulated.The safety of these candidates is investigated using the intensity theory.In addition,the small angle scattering and the transverse range of ions are simulated using SRIM code,including all the effects on the beam spot size broadening,such as the incident ion energy, the material and the thickness of the window and the air composing.At last,the appropriate vacuum windows are presented,including the structure,material and thickness.
The micro-beam irradiation system,which focuses the beam down to micron order and precisely delivers a predefined number of ions to a predefined spot of micron order,is a powerful tool for radio-biology,radio-biomedicine and micromachining.The Institute of Modern Physics of Chinese Academy of Sciences is developing a heavy-ion micro- beam irradiation system up to intermediate energy.Based on the intermediate and low energy beam provided by Heavy Ion Research Facility of Lanzhou,the micro-beam system takes the form of the magnetic focusing.The heavy-ion beam is conducted to the basement by a symmetrical achromatic system consisting of two vertical bending magnets and a quadrupole in between.Then a beam spot of micron order is formed by a magnetic triplet quadrupole of very high gradient.The sample can be irradiated either in vacuum or in the air.This system will be the first opening platform capable of providing heavy ion micro-beam,ranging from low(10MeV/u)to intermediate energy(100MeV/u), for irradiation experiment with positioning and counting accuracy.Target material may be biology cell,tissue or other non-biological materials.It will be a help for unveiling the essence of heavy-ion interaction with matter and also a new means for exploring the application of heavy-ion irradiation.
