Hi,
I have a Cathodoluminescnece system, which is a scientific instrument. It is circa 1980's technology. This instrument uses a cold cathode to create an electron beam, which is directed towards the surface of a sample. The electron beam will cause certain samples to luminesce. The maker of this instrument was essentially a one man company and that man has since retired and is no longer reachable. The good thing is that the cold cathode portion of the instrument is user-serviceable.
The system I have worked for quite a while but I haven't used it in several years. In starting up the instrument, I have come across several issues and I have rectified all but one. The system works by pumping a vacuum (~50-100 mTorr) on the sample chamber and cathode. Once the appropriate vacuum level is reached, the high voltage is switched on and a dial is used to increase the voltage (up to an operating voltage of 10-15 kV).
The problem: When turning up the voltage, the current increases quickly. By the time the voltage is turned up to a value of approximately 2 kV, the current reaches a limit and trips the high voltage circuit.
Some additional information:
-Without a vacuum, the voltage can be turned up to 15 kV (the maximum value). Only a small current is observed, which according to the manual is related to the current limiting circuit.
-The moment as a vacuum is applied to the system at 15 kV, the current limit is tripped and the HV is turned.
-Based upon the behavior of the vacuum gauge, I believe that the gauge is fine and that the system is pumping down to an appropriate level.
-I have carried out the troubleshooting steps listed in the manual. Based upon the fact that I can turn up the voltage to 15 kV when no vacuum is present, I think that the power supply is working properly.
I have attached a manual for the instrument which includes various troubleshooting options and circuit diagrams.
I fear that this may be too complex of a question to post online, but I thought I'd give it a shot in case anyone has ideas. I will do my best to answer questions and respond quickly. Oh, I'm far from an expert in electronics, though I have some basic knowledge and tools.
Thank you kindly,
Chris
I have a Cathodoluminescnece system, which is a scientific instrument. It is circa 1980's technology. This instrument uses a cold cathode to create an electron beam, which is directed towards the surface of a sample. The electron beam will cause certain samples to luminesce. The maker of this instrument was essentially a one man company and that man has since retired and is no longer reachable. The good thing is that the cold cathode portion of the instrument is user-serviceable.
The system I have worked for quite a while but I haven't used it in several years. In starting up the instrument, I have come across several issues and I have rectified all but one. The system works by pumping a vacuum (~50-100 mTorr) on the sample chamber and cathode. Once the appropriate vacuum level is reached, the high voltage is switched on and a dial is used to increase the voltage (up to an operating voltage of 10-15 kV).
The problem: When turning up the voltage, the current increases quickly. By the time the voltage is turned up to a value of approximately 2 kV, the current reaches a limit and trips the high voltage circuit.
Some additional information:
-Without a vacuum, the voltage can be turned up to 15 kV (the maximum value). Only a small current is observed, which according to the manual is related to the current limiting circuit.
-The moment as a vacuum is applied to the system at 15 kV, the current limit is tripped and the HV is turned.
-Based upon the behavior of the vacuum gauge, I believe that the gauge is fine and that the system is pumping down to an appropriate level.
-I have carried out the troubleshooting steps listed in the manual. Based upon the fact that I can turn up the voltage to 15 kV when no vacuum is present, I think that the power supply is working properly.
I have attached a manual for the instrument which includes various troubleshooting options and circuit diagrams.
I fear that this may be too complex of a question to post online, but I thought I'd give it a shot in case anyone has ideas. I will do my best to answer questions and respond quickly. Oh, I'm far from an expert in electronics, though I have some basic knowledge and tools.
Thank you kindly,
Chris
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