PPubMed1 Jan 2022Cited 10×

Single-shot experiments at the soft X-FEL FERMI using a back-side-illuminated scientific CMOS detector Single-shot experiments at the soft X-FEL FERMI

Cyril Léveillé, Kewin Desjardins, Horia Popescu, Boris Vondungbo, Marcel Hennes, Renaud Delaunay, Emmanuelle Jal, Dario De Angelis, Matteo Pancaldi, Emanuele Pedersoli, Flavio Capotondi, Nicolas Jaouen

Abstract

'Marcel Hennes' 'Renaud Delaunay' 'Emmanuelle Jal' 'Dario De Angelis' 'Matteo Pancaldi' 'Emanuele Pedersoli' 'Flavio Capotondi' 'Nicolas Jaouen'] We demonstrate the possibility of using a CMOS 2D sensor for time-resolved pump-probe XUV FEL experiments. We gained a factor of 30 in acquisition time compared to the use of a commercial CCD-BSI.

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CMOS detector enables single‑shot XUV FEL experiments with ~30× faster data acquisition than traditional CCDs.

What’s new

i.Demonstrated a back‑side‑illuminated scientific CMOS detector for single‑shot soft X‑ray FEL experiments
ii.Achieved roughly a 30‑fold reduction in acquisition time compared to CCD‑BSI detectors
iii.Validated detector linearity over a wide fluence range and measured its noise performance
iv.Performed proof‑of‑principle pump‑probe demagnetization measurements with single‑shot data
v.Showed feasibility of XPCS experiments using the CMOS detector

How they did it

An AXIS‑SXR camera equipped with a GPIXEL GSENSE400BSI CMOS sensor was installed at the FERMI DiProI end‑station. Pump‑probe experiments used a 100 fs IR laser and a 60 fs 58 eV XUV FEL pulse, recording single‑shot scattering frames while continuously varying the pump‑probe delay. Results were compared to those obtained with a conventional CCD‑BSI under identical conditions.

What they found

~30× faster acquisition time (20 s for ~1000 points vs ~600 s with CCD)
Linear detector response over one order of magnitude fluence (offset <10 %)
Maximum pixel signal 800 ADU/pixel, far below saturation limit of 65 000 ADU
Detector noise ≈4 ADU RMS for 14.5 ms exposure
Demagnetization time constant ≈90 fs with 13 fs standard deviation across fluences

Caveats

✕Quantum efficiency drops to ~20 % around 50 eV, limiting low‑energy performance
✕Camera operated without active cooling (stabilized at 6 °C), leading to higher noise than possible
✕Linearity deviates at high fluences due to sample electronic changes
✕Current sensor efficiency is low for energies below ~1000 eV

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Single-shot experiments at the soft X-FEL FERMI using a back-side-illuminated scientific CMOS detector Single-shot experiments at the soft X-FEL FERMI

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