Patent Number: 
Section: claims

1. A range shifter that outputs a particle beam incident thereto while attenuating energy of the particle beam, comprising:a transmissive plate whose thickness has been adjusted based on a setup value of an amount of the energy to be attenuated; anda holder portion that holds the transmissive plate;wherein the thickness of the transmissive plate is adjusted to a thickness equivalent to an attenuation amount that is lower than the setup value by a predetermined rate; andwherein at least one of the transmissive plate and the holder portion is provided with a superimposing mechanism configured to releasably superimpose an adjustment sheet over the transmissive plate, said adjustment sheet being adjusted such that it has a thickness equal to or less than twice the attenuation amount of the predetermined rate. 2. The range shifter of claim 1, wherein the predetermined rate is set to from 2% to 7%. 3. The range shifter of claim 2, wherein the superimposing mechanism superimposes the adjustment sheet over the transmissive plate on the incident side of the particle beam. 4. A particle beam therapy system comprising:an accelerator that generates a particle beam;a plurality of treatment rooms;transport paths that connect between the accelerator and each of the plurality of treatment rooms; andan irradiation device provided in each of the plurality of treatment rooms, that forms the particle beam supplied through the transport path into an irradiation field that matches an irradiation target, to thereby irradiate the irradiation target with the particle beam,wherein the range shifter of claim 3 is provided in the irradiation device. 5. A particle beam therapy system comprising:an accelerator that generates a particle beam;a plurality of treatment rooms;transport paths that connect between the accelerator and each of the plurality of treatment rooms; andan irradiation device provided in each of the plurality of treatment rooms, that forms the particle beam supplied through the transport path into an irradiation field that matches an irradiation target, to thereby irradiate the irradiation target with the particle beam,wherein the range shifter of claim 2 is provided in the irradiation device. 6. The range shifter of claim 1, wherein the superimposing mechanism superimposes the adjustment sheet over the transmissive plate on the incident side of the particle beam. 7. A particle beam therapy system comprising:an accelerator that generates a particle beam;a plurality of treatment rooms;transport paths that connect between the accelerator and each of the plurality of treatment rooms; andan irradiation device provided in each of the plurality of treatment rooms, that forms the particle beam supplied through the transport path into an irradiation field that matches an irradiation target, to thereby irradiate the irradiation target with the particle beam,wherein the range shifter of claim 3 is provided in the irradiation device. 8. A particle beam therapy system comprising:an accelerator that generates a particle beam;a plurality of treatment rooms;transport paths that connect between the accelerator and each of the plurality of treatment rooms; andan irradiation device provided in each of the plurality of treatment rooms, that forms the particle beam supplied through the transport path into an irradiation field that matches an irradiation target, to thereby irradiate the irradiation target with the particle beam,wherein the range shifter of claim 1 is provided in the irradiation device.