Goran Skoro Thermal stress in different materials
Thermal Stress~ET/(1-) T=EDD/Cp - thermal expansion coefficient E – elastic modulus T- temperature rise - Poisson’s ratio EDD – energy deposition density Cp– specific heat =f(T); E=f(T); =f(T); Cp=f(T) !!! strain Thermal Stressas a function of temperature for different materials???
High temperature target candidates: Ta, W, Nb(?), Mo(?)… 20 J/g corresponds to ~ 300 J/cc in Ta (and W) - energy density for 5 MW beam power, 6 GeV protons - Temperature dependent materials properties from MPDB database (see: www.jahm.com/index.html)
Assuming that the tensile strength (=f(T)) is a measure of material mechanical strength we can introduce ‘stress quality’ factor= thermal stress/tensile strength lower value of stress quality factor -> ‘better’ candidate for solid target W much better than Ta! Nb (?) Mo – looks fine! NB. Mo is valuable alloying agent. Almost all ultra-high strength steels contain Mo in amounts from 0.25 to 8% (German’s “Big Bertha” is ‘good’ example). Molybdenum? Is it a serious candidate for target?