Energy degrader and charged particle beam irradiation system equipped therewith

Abstract

An energy degrader includes a plurality of attenuating members configured to attenuate the energy of an incident charged particle beam, the plurality of attenuating members having different amounts of energy to be attenuated. A low-energy-side attenuating member that is the attenuating member with a larger amount of energy to be attenuated is made of a material having a higher transmittance of the charged particle beam than that of a high-energy-side attenuating member that is the attenuating member with a smaller amount of energy to be attenuated.

What is claimed is: 
     
         1 . An energy degrader comprising:
 a plurality of attenuating members configured to attenuate the energy of an incident charged particle beam, the plurality of attenuating members having different amounts of energy to be attenuated,   wherein a low-energy-side attenuating member that is the attenuating member with a larger amount of energy to be attenuated is made of a material having a higher transmittance of the charged particle beam than that of a high-energy-side attenuating member that is the attenuating member with a smaller amount of energy to be attenuated.   
     
     
         2 . The energy degrader according to  claim 1 ,
 wherein only the low-energy-side attenuating member with the largest amount of energy to be attenuated among the plurality of attenuating members is made of a material having a high transmittance.   
     
     
         3 . The energy degrader according to  claim 1 ,
 wherein the low-energy-side attenuating member is formed from beryllium, and the high-energy-side attenuating member is formed from graphite.   
     
     
         4 . A charged particle beam irradiation system including the energy degrader according to  claims 1  and irradiating the charged particle beam, the charged particle beam irradiation system comprising:
 an accelerator configured to accelerate charged particles introduced into the energy degrader; and 
 an irradiation device configured to irradiate the charged particle beam having energy attenuated by the energy degrader.