Current News
Status, October 3rd, 2006
FI CCD Science detector Fails.
The WiFeS Red Arm Science CCD has failed during operation.
From my notes, it looks as if the device failed at the end of Cooldown 1
on Thursday September 14th., after the QE data was taken - reported on
the previous page.
The problem appears to have been to do with the glue used to mate the copper
lug to the back of the detector package. The copper lug is the unit we use to mount
the device to our cold surface. The glue failed at the CCD operating temperature,
and the detector moved forward away from the cold surface. The flex held the device
in place, preventing it from falling forward onto the the dewar window.
However there was sufficient space between the 2 parts, to allow the detector's
temperature to rise sufficiently to cause a large increase in dark current while
the block remained cold. The rise in temperature caused Bias frames to look smeared,
indicating an elevation in the dark current. This was seen on all bias frames taken
after the 14th Sept., but not on any frames prior to that.
Inspection of the detector last Tuesday (26th Sept) revealed the parting of the
ways between the detector package and its mounting lug, see the next pictures:-
1.FI CCD mounted in Test Dewar #2.
2.FI CCD showing separation of the Detector
from its copper mounting lug.
Fairchild Imaging were contacted straight away and they have confirmed this was a
known problem with the glue used at the time this CCD was purchased in Nov 2004.
They were very apologetic and have unconditionally offered to replace the device.
This will arrive in the next week or 2, the old device has already been returned,
and when it does the characterisation process wil begin again.
I have been assured that the glue problem has been remedied and the new device will
operate without the extra feature!!
Enquiries about the WiFeS Detector Failure?
detman@mso.anu.edu.au
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