BLP Gas-Phase Replication Effort - Run 11….9FEB98 ………………..(best viewed with 1024 pixel display width)
Legend
Total Input Power (electrical)
Output Power (heat)
Chamber Wall Temperature (C)
Gas Temperature (C)
Gas Pressure (torr)
Filament Temperature (° C)
Room Temperature (C)
Inlet water Temperature (C)
This was a filament research run, in which we attempted to scavenge oxygen from the chamber with several soakings in hot H2 gas before attempting to operate the filament. There was no catalyst in the chamber.
We started the run with 30 watts to the cartridge heater to bring the chamber up to operating temperature. After 2.5 hours of warm-up we admitted ~15 torr of H2 gas to the chamber and closed it off. This event is marked by the sudden jump in the Press trace, which is plotted on a 0-20 mm scale. We figured that the highest tolerable hydrogen pressure should be used to promote the chemical activity of the hydrogen. 15 torr is the rated full scale for the delicate silicon pressure sensor we are using. Interestingly, the Press trace continued to climb over the next hour as if some reaction were taking place in the chamber that produced more and more gas…? At hour 3.5 we evacuated the chamber. At hour 4.1 we again filled the chamber with about 15 torr of H2 gas. This time the pressure did not creep up during the 30 minute period that the gas was present. At hour 4.7 we evacuated the chamber again and we repeated this hydrogen filling procedure one more time during the next hour. Upon evacuating the 3rd load of hydrogen from the chamber we applied 10 watts to the new tungsten filament and reduced the cartridge heater power to 20 watts. By this time, Pout was running satisfactorily close to Pin, indicating thermal equilibrium in the calorimeter. We ran the filament for about an hour in vacuum to thoroughly degas it and then admitted the standard 2 torr of H2 gas to the chamber. As you can see from the Tfil trace, the results were both familiar and disappointing. The filament was attacked at the same rate as before. It lasted about an hour during which time we manually adjusted the cartridge heater power to keep the total input power at 30 watts.
Apparently the hydrogen scavenging cycles did not help at all. Maybe the Pt wire will be here in a day or two.
Note the anti-correlated Tgas and Twall traces during the hydrogen scavenging. With hydrogen in the chamber, the gas temperature sensor is held down close to the wall temperature. With the chamber evacuated, the gas temperature sensor sees only the considerably radiation from the nearby cartridge heater and its temperature rises significantly.