CFH12K Focal Plane Integration at IfA
November 1998
Here is a reduced collection of pictures taken during the integration of the CFH12K focal plane at IfA over the past week. Participants were Gerry Luppino, Jean-Charles Cuillandre, John Tonry and Barry Starr.
MIT/LL CCID20: the brick of the mosaic - November 6th, 1998
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This pictures shows the 2Kx4K thinned CCD designed and produced by the MIT Lincoln Laboratories. It is mounted on a package designed by Gerry Luppino. |
How to get a flat mosaic: measuring the height of each device - November 6th, 1998
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Each individual CCD+package has its own geometric characteristics after mounting (CCDs are mounted on the packages by MIT/LL). To get a perfectly flat mosaic, each device needs to be accurately measured and shims underneath the package (3 of them) machined. Here Gerry is using a powerful microscope to measure 6 points around the CCD+package which is mounted on a XYZ stage. Precision of the measurements is about 10 microns. |
Getting started - November 6th, 1998
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Before starting this exhausting task, Gerry takes a deep breath. The cold plate is empty, one can see the holes where packages will fit in. |
An almost complete 12K8K mosaic - November 6th, 1998
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8 CCDs are now installed on the focal plane. Notice the flexprints that had to be safely kept tied. All the pins of the connector on each flexprint are grounded together to avoid risks of static discharges damages on the CCDs. |
CCD delivering - November 6th, 1998
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Barney, the CFH12K mascot, never failed to deliver safely and on time each CCD. |
First look at a 12K8K mosaic - November 6th, 1998
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The 12K8K focal plane is amazingly flat, hence confirming the accuracy of measurements made a few days before with the XYZ stage and the precision of the machining made at the IfA machine shop. |
La curiosite est un vilain defaut - November 6th, 1998
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Some people could not resist checking out this amazing piece of technology! |
Let's take a walk - November 6th, 1998
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The focal plane needs to reach its final home: the cryostat. (pictures were actually being taken at that time on the white background, Gerry kept a strap on his wrist to avoid static discharges that could damage the CCDs). |
Chunks of CFH12K - November 5th, 1998
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This picture was taken to get the overall weight of the CFH12K cryostat. |
The focal plane mounted in the cryostat - November 6th, 1998
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The focal plane is now installed in the camera head. Gerry is setting the four screws keeping the focal plane is place. Measurements made prior integration of the CCDs on the cold plate showed that the tilt of the plate is less than 30 microns over the whole length of the mosaic. During all the sensitive operations, we kept an eye on each other; here John looks with anxiety Gerry handling the mosaic in one of the most dangerous operation... |
Can you see the light? - November 6th, 1998
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Don't be fooled by the apparent high reflectivity of these CCDs: they have a very high quantum efficiency. They look blue because they have a lower efficiency in the blue spectrum. Portrait de famille with Gerry, John and Barry. |
Final configuration in the cryostat - November 6th, 1998
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The window is now installed. The observing configuration at the CFHT prime focus will be look down. |
Installing the cold straps - November 8th, 1998
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On the back of the focal plane, a cold strap (coper) attaches to the back of each CCD package then connecting it to the big cold finger (the long bar) that will be attached to the nitrogen can. Notice the heat resistor on the back of the CCD packages. They will allow precise thermal regulation at a given temperature (-90C). |
CCDs testing setup - November 12th, 1998
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The CCDs are now at cryogenic temperature. A berylium has been installed (not seen here) to conduct Xrays tests but an internal LED in the dewar allows normal imaging tests. Notice the two Generation SDSU II controllers (Leach) on both sides of the cryostat. Each controller handles 6 CCDs. They are both running from the same clock hence allowing synchronized readouts without inducing noise on each other. The readout time for the whole 12K8K is 58 seconds (writing to disk in parallel included) and the readout noise is around 4 electrons! |
A first impression of the full mosaic - November 11th, 1998
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This image is a combination of the 12 frames, geometry of the relative CCD output is respected. This is a "flat-field" of 4 seconds obtained with the internal LED. The LED is located under the focal plane on one side of the dewar, so the light bounces several times before reaching the CCDs, causing this very non-uniform illumination. Notice the brick wall pattern on some of the CCDs (the dots on the upper left are a artifact of the image combination). The average flux on this image is 4000 ADUs (gain about 0.7 e-/ADU). |
Barney: the CFH12K mascot - November 12th, 1998
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Ages of dragons blowing fire are over, now with have purple dinosaurs blowing nitrogen and wearing ice shirts! |
