Report on future detector requirements at ESRF

Linearity:
For the same reason, linearity on an extended range of intensities has to be reached on both
main detector and incident flux detector.
Flux on detector:
In order to optimise the use of the detector characteristics (linearity and signal to noise ratio),
the flux is adjusted so that the measured currents range from 0.1 pA and 1 µA. To give an
equivalent in terms of photons on a Si diode, 0.1 pA corresponds to 3000 photons of 1 keV.
Particular operating conditions:
The detectors will be operated in ultra-high vacuum, near high magnetic fields up to 6 T.
Existing detectors
ID12 is using Si pnn + photodiodes operated in the photovoltaic mode and optimised for the
beamline by Eurisys-Mesures [Goulon et al., 2005]. The dark current on both I and I0 is
measured alternatively with the fluorescence signal using a chopper at a typical frequency of
67 Hz.
Short term possibilities
A patent (FR08/55566, Goulon et al.) has been registered concerning a detector for the
measurement of ferromagnetic resonances at GHz frequencies.
Main required improvements
The main expected improvement concerns the detection of signals of very low intensity at
high frequencies.
Other types of detectors
Circular Polarization Beamline also uses an energy dispersive detector (see page 94).
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