Tuesday, September 05, 2006
TWIN windows became dirty again
After the labor day, we tried to continue the experiments. So I filled the new gases into the TWIN excimer amplifier this morning. The output energy of the front end was 34.7 mJ, Alex already used this beam to align the target and x-ray spectrometer. Unfortunately, the energy was dropped to 7.7 mJ suddenly in the afternoon, I found there were small dust grains on the long chamber windows, which was similar to the status two weeks ago (on Aug. 22th). I cleaned the same windows on May 10th (http://xysong.blogspot.com/2006/05/twin-dirty-windows.html). It is very strange that the windows became dirty frequently. I guess the filter was dirty or something wrong inside the long tube.
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I think your energy drop is strange but not unbelievable. If you use the laser each day usually you need to check the windows regularly (every month) and clean them if they are dirty. If you cleaned them in May, it is already time to clean them again. I am not wondering if they are dirty. However, it is still strange that the energy dropped so much within one day, it cannot be caused by the windows. If the windows are dirty, the gas lifetime is shorter but usually not that much. The 35 mJ energy with a new fill is also lower than the values from earlier, so I think the windows were dirty also in the morning.
Are you sure that the font-end, timing and the whole alignment was still ok in the afternoon (pinhole alignment, off-axis angles, etc.)?
Was it a problem with the short tube, or the long one, or probably both tubes (after the short tube the energy was ok or not and if not than the input energy was ok or not)?
Have you seen any kind of leakage (pressure drop)?
Could you please check if the fan motors are working well?
First I would suggest not to open the reservoir. However, I can imagine that you migth have some problems with the magnetic coupler inside the tube. Can you hear any strange noise from inside? Does the fan-motor run well?
Perhaps you should check if the fan is working. You can use the small aluminium window I marked on the picture (see attachment) for that. I would do that parallel, when I clean the windows and the laser is opened anyway. Use a torch to illuminate the fan, and turn the motor by hand to check if the fan is runnig, whether you can feel or hear some friction
(between magnetic coupler and reservoir end-plate), or perhaps it is not running at all.
If everything is ok with the pressure and the fan, I would recommend you to clean the windows, check for tightness, make a new fill, align the system and check the energy and the gas-lifetime.
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