abnormally low UV incident light

Hello Kang,

I'd be interested to get feedback on whether you are working mostly in the UV region of the spectrum - or mostly in the VIS region?

The symptoms suggest you may have an issue with solarization of the D2 lamp.
Solarization is the term used for the discoloration that can occur in the quartz envelope of the lamp when this is exposed to prolonged exposure to high energy radiation (such as short UV, X-rays, gamma rays and neutrons). This is a natural process that occurs with fused quartz. When this discoloration occurs, the UV intensity is reduced.
You can check this by removing/examining the lamp when it is cool (but do not touch with bare fingers). A dark patch in the lamp would confirm this has occurred.

Solarization of the lamp occurs because the lamps are being operated continuously. The solarization of the D2 lamp means that the intensity of light will drop, even if the vis lamp is OK.
If you are only working in 1 region of the spectrum, it is recommended that the user switches off the lamp that will not be required i.e. if measuring in the VIS range, then switch off the D2 lamp. Or if you are only measuring in the UV region, then switch off the VIS lamp.
Although this will require some warm-up prior to use when or if you need to extend the measurement range again, you should expect to see less issues with solarization and reduced intensity from the D2 lamp. This should extend the time before the solarization issue occurs.

If there is solarization of the lamp and the performance is no longer acceptable for your application, then it is necessary to replace the lamp.

Hope this helps,

Eric

Hello Kang:

Generally, and aging lamp would be the likely cause of this problem.  The average life of the 8453 lamp is 1000 hours.  Lamp performance and lifetime may also be affected by physical shock while the lamp is hot, igniting the lamp while it's hot, or frequency of ignition.

If the lamp is new and the self-tests pass except for the UV range, then another possibility may be a solarized source lens.  This is more likely for an older 8453 where many hours of UV light have passed through the lens.  (The 8453 was manufactured from 1995 to 2014.)

Best regards,

Mike

Hi Eric, 

Thank you for your suggestions and thorough explanations! While I agree that the aging lamp could be the cause, the problem still persisted after I replaced the lamp by a brand new one. So I was hypothesizing there were causes related to optical parts. 

Best,

Kang

Hi Mike,

The problem persisted even after a brand new lamp was installed. Our instrument was purchased around 2011, so it likely fall in the range you mentioned. Can I have your suggestions on how to replace the source lens, such as the part number etc.? Thanks!

Best,

Kang

Hello Kang:

The part number is G1103-68002. 

Before replacement, attempt to clean the lens using the procedure described in the online help of UV-Vis ChemStation.

The replacement of the lens should only be performed by an Agilent qualified field service engineer.  If the source housing is damaged during replacement, the optical bench will need to be replaced.

Best regards,

Mike