Accommodation of the Rare Gases on Clean Tungsten Surfaces Between 77 and 380 K

Using the hot filament method, the thermal accommodation coefficients (a. c.) of the rare gases on clean tungsten surfaces were measured as a function of gas and surface temperatures. As described earlier, the extreme cleanliness of the surface and of the system was achieved by the use of ultra high vacuum techniques and monitored by a field emission microscope. The results show that the gas temperature influences the magnitude of the a. c. in practically all cases. The numerical results for the isothermal a. c. agree well with the best values reported previously. In most cases, an influence of the surface temperature is found as well, which seems to increase with increasing trapping of the accommodating gas. Within the accuracy of the measurements, no influence of the gas pressure on the a. c. is found.