Preparing a HERMES Proposal

All HERMES detectors are from the E2V CCD231-84 family, grade-0 cosmetic quality (the highest available quality), and are 4096 x 4112, 15um pixel devices. All CCDs are housed in cryostats operating at about a temperature of 170K.

The "blue" and "green" channel detectors are both 16 micron, standard silicon devices with broadband and mid band coatings. The "red" channel detector is a 40 micron, deep depletion device with fringe suppression and an ER1 coating. The "IR" channel detector is a 100 micron bulk silicon device with fringe suppression and a "Multi-9" coating.

CCD Readout Amplifiers 

Each detector is controlled with an AAO2 CCD controller, and permit readout from one, two or four detector outputs at various readout rates with windowing and binning options.

Y (spatial direction)

 X (spectral direction)

Using two Left amplifiers or two Right amplifiers readout the detector in the spatial direction avoiding splitting the data in the spectral direction. Using two Top amplifiers or two Bottom readout the detector in the spectral direction, splitting a single fibre spectrum into two. Using all four amplifiers reads the detector in 4 quadrants.

CCD Readout modes

The table below gives the gain, readout noise and readout times for the various readout modes using  a single top left amplifier. The values for other amplifers are very similar.  The level of dark current in the four CCDs is between 1.5 - 3.0e/pixel/hour.

Each CCD can be binned independently in the Y (spatial) direction and up to 2x in the X (spectral) direction for all readout modes. The readout times for binned data using two amplifiers with FAST readout are as given below. Double the readout time for single amplifer mode and halve the readout time if four amplifiers are to be used.