For further information please read this document on EMCCDs by Dhillon & Tulloch.

Dark Current

1. The camera must be setup and allowed to cool to operating temperature, the camera must have been running for 2 hours. If the controller is reset or even a dasreset issued then it is important to wait 2 hours. The dark current is excessive during the first 2 hours after a controller reset.

The EM output

1. Set the camera to 'fast' speed this selects the EM output.

2. System Gain (gs)

2(i). Use the timing .lod file

/home/dspdev/ccd/timIII/QUCAM3/genIII_QUCAM3_NINV_NONFT_tim.lod

or

/home/dspdev/ccd/timIII/QUCAM2/genIII_QUCAM2_NINV_NONFT_tim.lod

depending on the camera. With this Electron Multiplication is enabled.

2(ii). Take a weakly-illuminated image, a few tens of counts is sufficient. e.g. test.fit

2(iii). Iraf does not give the option of a natural log for the y-axis of a histogram, it is therefore necesary to use excel to plot the histogram required to calculate the gain. Instead of plotting a graph of the histogram the output must be sent to file 'epar imhisto (listout = yes) List instead of plot histogram'.

2(vi). Make a histogram of the image and send to a file e.g.'imhisto test1 > histo_test1.txt'

2(v). Copy or ftp this file 'histo_test1.txt' to a machine with excel.

2(iv). Import into excel and produce a histogram of the Signal in ADUs. Take a least-squares linear fit of the graph, the slope of which gives the system gain gs. Here is an excel file that can be used as a template.

2(v). N.B. It is possible to get a good idea of the camera gain with a rough calculation from the iraf graph.

cl> imhisto test.fit

For this the output of imhisto must go to a plot 'epar imhisto (listout = no) List instead of plot histogram'

3. Gain with EM gain turned off (gso)

3(i) Use the timing .lod files

/home/dspdev/ccd/timIII/Q2TEST/genIII_QUCAM2_NINV_NONFT_tim_HVoff.lod

or

/home/dspdev/ccd/timIII/Q3TEST/genIII_QUCAM3_NINV_NONFT_tim_HVoff.lod

depending on the camera.

these .lod file reduces the amplitude of the HV clock to 20V. At this level there is no electron multiplication the serial register behaves like a normal CCD output register.

3(ii) Set the readout speed to'fast'.

3(iii) Measure the gain in the normal way using the 'gain' script.

4. EM gain (ga)

The EM gain is the multiplication factor equal to the mean number of electrons that exit the EM register in response to a single electron input. ga = gso/gs

The Conventional Output

1. Set the camera to 'slow' speed this selects the conventional output, check the bias noise and gain in the normal way using the 'gain' script.

Frame Transfer Mode

1. It is not possible to test frame transfer mode with Voodoo this must be done with the observing system.