Optimization research on image lens of proton radiography

Parameters of Zumbro lens are optimized to minimize the image blur. When the length of outer drift equals to the length of inner drift, the image blur is minimized or is very close to the minimum. Field of view of Zumbro lens is also investigated, which is not sensitive to parameters of Zumbro lens and is close to two thirds of the aperture of quadrupole magnet. Parameters of a Zumbro lens for 20 GeV proton radiography are presented. Geant4 simulation resluts show that the parameters are valid.