Subject: New gain on the red arm of DIS

From: Gordon Richards

Submitted: Fri, 28 Aug 1998 01:44:00 -0500 (CDT)

Message number: 65 (previous: 64, next: 66 up: Index)

Fellow users of DIS,

As you all well know, the read noise on the red arm of DIS has been
rather high (and variable) lately.  The RN had reached 40 electrons,
which was mostly due to the fact that the bias histograms are doubled
peaked (actually they are sometimes triply peaked).

On 22 August 1998 (UT) Jon Brinkman and Jim Gunn (others?) took a look
at DIS to see if they could resolve the problem.  The power supplies
were swapped and other ones were tried as well.  

The end result is that the problem and the solution to it are still
not clear, but DIS has been left in a state that is far better than it
was found in.

The reason for this note is to report new values for the RN and gain,
since the gain on the red side has changed considerably as a result of
a new power supply which operates at a different voltage.

On the night of the changes, Tia and I found:

	Gain(electrons/ADU)	RN(ADU)
Blue		0.992		9.238
Red		1.497		6.788

Where the errors are certainly larger than the 3 decimal places that I
give the numbers to.

As of last night, the blue RN is stable at about 9.5 electrons, but
the red RN is up to 14.3 electrons and is starting to show a double
peak in the bias histogram.  Jon Brinkman is looking into this
continued change on the red side, but for now it is certainly better
than it has been and the blue side is really quite nice.


Gordon

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