Dectris EIGER 2 - Continuous Readout; Auto-Summation; Instant Retrigger

3.2.2. Continuous Readout
A hallmark feature of EIGER2 is its continuous readout that enables high frame rates at high duty cycles with
only 100 ns deadtime between frames. Every pixel of an EIGER2 ASIC features two digital counters for each
of its two energy discriminating thresholds. After acquisition of a frame, the pixels switch from counting in
one digital counter to the other. While one counter is being read out, data acquisition continues in the other
counter.
3.2.3. Auto-Summation
EIGER2 auto-summation mode is a further benet of continuous readout with high duty cycle. While a single
frame is limited to the 16 or 8 bit of the digital counter, auto-summation extends the data depth up to 32 bit,
or more than 4.2 billion counts per pixel, depending on the number of summed frames in an image. At short
exposure times and high frame rates, all counts are captured in the digital counter of a pixel and directly read
out as an image. If long exposure times are requested, frames are still acquired at high rates on the pixel level,
eectively avoiding any overows. The detector system sums the frames to images on the y, extending the
bit depth of the data by the number of summed frames.
3.2.4. Instant Retrigger
EIGER2 X-ray detectors feature the DECTRIS INSTANT RETRIGGER
®
technology for improved high-rate count-
ing performance. The Instant Retrigger capability results in non-paralyzable counting and allows for enhanced
count-rate correction.
DECTRIS INSTANT RETRIGGER
®
with adjustable dead time is a photon counting imaging method that results
in non-paralyzable counting and achieves an improved high-rate counting performance. In a conventional
single-photon counting X-ray detector, the charge pulses generated by impinging photons are counted by digi-
tal circuits. Simultaneously generated pulses can pile up and result in photon counts being lost. At high photon
uxes, pulse pile-up signicantly aects the observed count rate and can lead to complete paralyzation of the
counting circuit. In the rst generations of EIGER and PILATUS photon counting detectors, even though a count
rate correction was applied to compensate for the counting loss at high count rates, the maximum usable count
rate was still limited by counter paralyzation. In EIGER2 detectors, the Instant Retrigger re-evaluates the pulse
signal after a predetermined dead-time interval after each count and is able to retrigger the counting circuit
should a pulse pile-up occur. The dead time interval is adjustable and is equivalent to the width of one single
photon pulse. This results in non-paralyzable counting and allows for enhanced count-rate correction so as to
achieve improved data quality at high count rates.
DECTRIS EIGER
®
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