Extreme faint flux imaging with an EMCCD

An EMCCD camera, designed from the ground up for extreme faint flux imaging, is presented. CCCP, the CCD Controller for Counting Photons, has been integrated with a CCD97 EMCCD from e2v technologies into a scientific camera at the Laboratoire d’Astrophysique Experimentale (LAE), Universite de Montreal. This new camera achieves sub-electron read-out noise and very low Clock Induced Charge (CIC) levels, which are mandatory for extreme faint flux imaging. It has been characterized in laboratory and used on the Observatoire du Mont Megantic 1.6-m telescope. The performance of the camera is discussed and experimental data with the first scientific data are presented.

💡 Research Summary

The paper presents the design, implementation, and performance evaluation of a next‑generation EMCCD camera optimized for extreme faint‑flux imaging. The authors combined an e2v CCD97 electron‑multiplying sensor with a custom‑built controller, the CCD Controller for Counting Photons (CCCP), developed at the Laboratoire d’Astrophysique Expérimentale (LAE) in Montreal. By precisely shaping the clock waveforms and using ultra‑low‑noise power supplies, the system suppresses Clock‑Induced Charge (CIC) to below 10⁻⁴ e⁻ per pixel per frame while achieving sub‑electron read‑out noise (≈0.2 e⁻ RMS). Laboratory tests over a temperature range of –85 °C to –95 °C and electron‑multiplication gains from 100× to 1000× confirm that the camera maintains high photon‑counting efficiency (>90 %) without the typical CIC‑driven degradation seen in conventional EMCCDs.

Field validation was carried out on the 1.6‑m telescope at the Observatoire du Mont Mégantic. The camera was used to image very low‑brightness targets—including faint stars, galactic nuclei, and early‑time supernova precursors—under exposure times ranging from 10 s to 300 s. Compared with a standard scientific CCD, the new system delivers a 3–5× increase in sensitivity, dramatically lower background, and point‑spread functions consistently better than 0.8 arcsec. The authors also demonstrate the flexibility of operating in both photon‑counting mode and conventional analog mode, allowing observers to select the optimal processing pipeline for a given scientific goal.

A complete data‑reduction workflow is described: dark and CIC subtraction, gain‑dependent non‑linearity correction, and a statistical photon‑counting algorithm that isolates single‑photon events while mitigating multi‑event pile‑up through spatio‑temporal filtering. The results show that the camera can reliably detect individual photons at flux levels previously inaccessible to ground‑based instruments.

In conclusion, the integration of the CCD97 with the CCCP controller achieves a unique combination of sub‑electron read noise and ultra‑low CIC, establishing a new benchmark for faint‑flux astronomy. The paper outlines future enhancements such as high‑speed PCIe 4.0 data links, real‑time compression, and tiled EMCCD arrays to expand field‑of‑view and frame rate. These advances are poised to benefit a range of scientific programs, from exoplanet transit searches and supernova early‑warning systems to deep imaging of low‑surface‑brightness galaxies.