为什么MH在未启动完成时关灯弧管会变黑？
(Apple Translate:) Why does MH turn off the arc tube black when it is not started?

I'm sorry, the machine translation makes the question a bit strange (and the Google translate was not better), so I don't know if I would be answering the real question:

Assume the question was why the arctube in the MH blackens when it shuts down short while after ignition:

When igniting, the discharge starts with cold electrodes, which causes heavy sputtering, aka the electrode material (= tungsten) being "sanded off" by the fast gas ions hitting the electrode and the sputtered tungsten then lands on pretty much anything inside of the tube, include the arctube wall. And that causes it to blacken.
Now when you let the arctube warm up and burn normally for about half a hour or more, the halogen cycle starts, moving the tungsten back from the arctube wall onto the electrodes, so clearing the walls back: The halogens (iodine,...) tend to react with the tungsten on the colder areas, so e.g. on the arctube wall, so etch out the tungsten landed there. The resulting halide then decomposes in the hot regions, so mainly in the arc and close to the electrodes (the heat there is too high for the molecule to stick together), causing a higher pressure tungsten cloud which then condenses back on the electrodes.

But this halogen cycle tungsten recovery requires the system to reach sufficient temperatures for the reactions to start and has to run for a while to move all the material back so clean up the arctube back.
If you do not let it run ther long enough after startup, this cleaning has no chance to take place and so the arctube ends up black.
By the way this is the reason, why in dimming systems the lamps are required to run at least half hour at full power after ignition before the power gets reduced to the desired level: The reduced power level may not provide enough heat for the cleaning cycle to run properly.

基本上只要点亮15分钟就会恢复正常
Basically, it only takes about 15 minutes to get back to normal

The reason why the arctube blackens shortly after ignition, when turning off the lamp at this moment, is because of mercury that has been condensed on the electrodes being sputtered on the arctube wall. It should evaporate within 1-3 min.

The reason why the arctube blackens shortly after ignition, when turning off the lamp at this moment, is because of mercury that has been condensed on the electrodes being sputtered on the arctube wall. It should evaporate within 1-3 min.

The reason why the arctube blackens shortly after ignition, when turning off the lamp at this moment, is because of mercury that has been condensed on the electrodes being sputtered on the arctube wall. It should evaporate within 1-3 min.

我发现只要MH启动完成并达到足功率，汞蒸气堆积就会消失
(Google Translate:) I found that as long as the MH starts and reaches full power, the mercury vapor accumulation will disappear.