Low Threshold Acquisition Controller for Skipper Charge Coupled Devices

In this work, the design and preliminary results of the first specially design Skipper-CCD controller, aimed for low threshold particle and astronomy experiments, is presented. The system integrates on a single board: the generation of the clock and bias signals for the sensor; four high-speed analog-to-digital converters to digitize the video channels of the CCD; Artix-7 FPGA to perform pixel calculation and board control; a front panel connector for all the signal inspection; and Ethernet port for full operation and data collection through standard network connection to a PC. The system has been fully tested and sample images were taken for both conventional and Skipper-CCDs.

I. Introduction

Initially presented as memory solutions [1] , [2] , Charge Coupled Devices (CCDs) have found a niche as imaging detectors due to their ability to obtain high resolution digital images. In particular, scientific CCDs have been extensively used in ground and space-based astronomy and X-ray imaging [3] . CCDs have low read-out noise, good spatial resolution, and low dark current. Furthermore, CCDs can be made thick and fully-depleted to increase its detection mass, enabling their use as particle detectors [4] . The low read-out noise can be as low as 2 e ⁻ , which enables obtaining a low energy threshold of 5.5 eV. Recently, with the development of fully-depleted Skipper-CCD, it has been possible to achieve a extremely low readout noise of 0.068e ⁻ [5] , [6] . Currently, the Sub-Electron-Noise Skipper-CCD Experimental Instrument (SENSEI) will use ~50 skipper-CCD to achieve a 100 gram mass for dark matter searches [7] . Other experiments like CONNIE (Coherent Neutrino-Nucleous Interaction Experiment) [8] and DAMIC (Dark Matter in CCDs) [9] are planning to migrate to this new skipper-CCD technology. This context has motivated the development of a low-noise electronic controller for Skipper-CCD, which will ease the migration for the mentioned experiments. The design of the so called Low-Threshold Acquisition (LTA) system is presented in Section II . Experimental results obtained with Skipper-CCD are shown in Section III , and Section IV summarizes and concludes the work.