能量损失 de 4z e lo NZ2 Ig nmv Lindhard a Scharff Nuclear Bethe Relativistic 1≈Z log E FIGURE : The generel dependance of the stopping power. dE/dx, is show as a function of energy for an on travelling through matter The schematic was taken from Sigmund(Sigmund 1977)
能量损失 e be v NZ mv Z e dx dE 2( ) lg 4 ~ 2 2 2 4 1 − =
Range of Heavy Charged Particles in a Medium Variation of a Intensity as a function of Thickness Intensity Detector Particles lose R ange all their energy at a distance absorber called range ing a source a source th sickness hield E de R 4-=/ca8=(2)m=() m 9(Uo
Range of Heavy Charged Particles in a Medium Variation of Intensity as a Function of Thickness Detector Absorber Intensity thickness straggling source Range source Shield Particles lose all their energy at a distance called range
a material is found to have a tenth-thickness of 2 3 cm for 1.25 Mev gamma rays,(a) What is the linear attenuation coefficient for this material?(b) What is the half-thickness?(c)What is the mean- free-path length for 1.25-MeV photons in this material? The specific rate of energy loss(dE/pdx )of a 5 Mev proton in silicon is 59 keV mgcm and its range R'is 50 mg cm Calculate values of(-dElpdxc) and range R'for deuterons, tritons, 3He and a particles, all of which have the same speed as the proton
A material is found to have a tenth-thickness of 2.3 cm for 1.25 MeV gamma rays, (a) What is the linear attenuation coefficient for this material? (b) What is the half-thickness? (c) What is the meanfree-path length for 1.25-MeV photons in this material? The specific rate of energy loss (-dE/ρdx) of a 5 MeV proton in silicon is 59 keV mg-1 cm2 and its range R' is 50 mg cm-2 . Calculate values of (-dE/ρdx) and range R' for deuterons, tritons, 3He and a particles, all of which have the same speed as the proton
2. 3 Radiation doses and hazard assessment Historical roots 2) Dosimetric Quantities 3)Natural Exposures for humans 4) Radiation effects
1) Historical Roots 2) Dosimetric Quantities 3) Natural Exposures for Humans 4) Radiation Effects 2.3 Radiation Doses and hazard Assessment
1)Historical Roots Early workers exposed to X-rays developed dermatitis (RKK) Uranium miners developed skin lesions People working with radioactivity experienced illness Researchers exposed to radioactivity suffered radiation sickness at advanced age Manhattan project workers in Los Alamos, Oak Ridge, Hanford, and atomic worker in the former USSR suffered anorexia (f) fatigue, headache, nausea(H), vomiting, and diarrhea
Early workers exposed to X-rays developed dermatitis（皮炎）. Uranium miners developed skin lesions. People working with radioactivity experienced illness. Researchers exposed to radioactivity suffered radiation sickness at advanced age. Manhattan project workers in Los Alamos, Oak Ridge, Hanford, and atomic worker in the former USSR suffered anorexia（厌食）, fatigue, headache, nausea（反胃）, vomiting, and diarrhea. 1)Historical Roots