DARKCURRENT

The dark current of the detector with no filter and the Ks filter was measured by timing the time it takes to fill the detector well as the chip warmed up. The time to fill was measured by sequencing the chip manually using the tickle program holding the reset line high for a few of the pixels then dropping it an watching the detector output voltage with an oscilloscope.

The conversion to electrons per second was made by assuming that the Full Well charge was 250,000 e. This value is too low. A fit to the slope of the darkcurrent line results in the following relation: 

Log10(e/sec) = -1.6 + 0.0525 * T(K)
The calculated values are: 
TChipSensor     Dark Current 
 (K)            (e/sec/pixel)
100               4500
 90               1300    <--- Present cooler temperature
 80                400
 70                120
These are higher than those derived from the Gemini results and indicate that the chip is substantially warmer than its holder.

The J filter data were done by measuring the exposure rate in a 1 second Fowler exposure. The loop is a result of measurements taken with the compressor turned back on for a while then back off.

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Last Revised Sep 13 2000