Heat transfer from the high-energy electron to the metal target

Temperature rise was measured when the electrons having energy from 3 to 10 keV were irradiated to five kinds of metal target (Al, Cu, Fe, Mo, Pt). The metal targets were irradiated with electron beam in vacuum of 10-5 mm Hg at current of 15 microampere and at accelerating voltage of 10 kV for 30 minutes to 4 hours. The diameter of tungsten filament for producing electrons was 0.3 mm. The size of slits was 3 mm x 20 mm. The distance between the accelerator and the second slit was 19 mm. The targets were 20 mm in width, 30 mm in length and 1 mm in thickness. A porcelain tube was provided for mounting the targets to change the incident angle. Reflection ratios were measured, and the ratio Q/I sub(t)V was examined, where Q is the heat value given to the metal targets by fast electrons, and I sub(t)V is the energy of input electrons absorbed into the targets. In conclusion, (1) the energy given to the surfaces of metals by electrons was almost same as the energy of the electrons absorbed by the surfaces of metals; (2) the Q/I sub(t)V decreased with the increase of input energy, but it slightly increased with the incident angle and the atomic number. These results are owing to the effect by the reflection ratios. (Iwakiri, K.)