<p> With the system in T9 and a Keithley Source Meter supplying HV to the detector.</p>
<p>The source meter supplies 200V and measures the current .... </p>
<p>I noticed that the current value was not stable... varying by +/-0.5uA. In conversation with Marcello i learnt that normally much more stable than this. </p>
<p>I have carried out the following changes.</p>
<p>added a 22nF X7R capacitor at the detector end of the Kapton cable from the HV connector pin ( G/R ) to the ground plane of the Kapton.</p>
<p>added a 14k resistor in series with the HV supply +ve signal before it connects to the adaptor board.</p>
<p>isolated the G/R connection on the second Kapton that would normally be connected to the HV on the detector.</p>
<p>The HV now is a lot quieter +/-0.01uA.</p>
<p>Next i disconnected the HV -ve input from ground at the adaptor board. This resulted in all the FEE64 being equally noisy!!</p>
<p>Next I connected a 22nF X7R capacitor between the HV negative and ground at the adaptor. This resulted in all FEE64 becoming equally calm. </p>
<p>The FWHM of the spectra is not good at 250 to 300 but the fact that all FEE64 are equal now is interesting.</p>
<p>I will update this post with pictures.</p>
<p> Update:- </p>
<p>This change was not stable and repeatable. I changed back to the original connections and things haven't gone back. </p>
<p>So power down and leave for today.... It doesn't make sense to me ... but then that's nothing new :-)</p>
<p>It appears that something is heating/charging up during the day and the noise becomes swamped by this effect ????</p> |