abnormally low UV incident light

Hello,

 

We have an Agilent 8453 UV-Vis spectrometer. It appeared that the UV incident light is abnormally weak (huge noise in the UV but normal baseline for Vis in the background scan) compared to the visible region, despite that both the SLS board and UV (deuterium) lamp were very recently replaced. I couldn't come up with other possible causes. Can I have suggestions on which part to troubleshoot? Or can I have suggestions on how to independently verify the UV lamp is working properly, so I can track down other optic components? 

 

Thank you,

Kang

Parents
  • 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

Reply
  • 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

Children
  • 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

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