We present a candidate sensor for future spectroscopic applications, such as a Stage-5 Spectroscopic Survey Experiment or the Habitable Worlds Observatory. This type of charge-coupled device (CCD) sensor features multiple in-line amplifiers at its output stage allowing multiple measurements of the same charge packet, either in each amplifier or in the different amplifiers. Recently, the operation of an eight-amplifier sensor has been experimentally demonstrated, and we present the operation of a 16-amplifier sensor. This new sensor enables a noise level of ∼1 erms− with a single sample per amplifier. In addition, it is shown that sub-electron noise can be achieved using multiple samples per amplifier. In addition to demonstrating the performance of the 16-amplifier sensor, we aim to create a framework for future analysis and performance optimization of this type of detectors. New models and techniques are presented to characterize specific parameters, which are absent in conventional CCDs and Skipper CCDs: charge transfer between amplifiers and independent and common noise in the amplifiers and their processing.
The Skipper CCD-in-CMOS image sensor integrates the non-destructive readout capability of skipper Charge Coupled Devices (CCDs) with a high conversion gain pinned photodiode on a CMOS imaging process, while taking advantage of in-pixel signal processing.
We will present the first results of the testing of the first prototype ASIC, fabricated in a commercial 180nm CMOS processes, which integrates a pixel matrix as well as individual test structures. Individual pixels in the test structures of the fabricated devices were instrumented to characterize their charge transfer capability and to study their operation in low readout noise conditions. We were able to operate the pixel in single carrier counting mode with deep sub-electron noise to measure charge packets collected by the photodiode when exposed to low illumination levels. Additionally, we will also report on the status of the custom 65nm ASICs prototypes being developed to achieve high speed, sub-electron noise readout. Work supported by the DOE Office of Science under the Microelectronics Co-Design Research Project “Hybrid Cryogenic Detector Architectures for Sensing and Edge Computing enabled by new Fabrication Processes
The non-destructive readout capability of the Skipper Charge Coupled Device (CCD) has been demonstrated to reduce the noise limitation of conventional silicon devices to levels that allow single-photon or single-electron counting. The noise reduction is achieved by taking multiple measurements of the charge in each pixel. These multiple measurements come at the cost of extra readout time, which has been a limitation for the broader adoption of this technology in particle physics, quantum imaging, and astronomy applications. This work presents recent results of a novel sensor architecture that uses multiple non-destructive floating-gate amplifiers in series to achieve sub-electron readout noise in a thick, fully-depleted silicon detector to overcome the readout time overhead of the Skipper-CCD. This sensor is called the Multiple-Amplifier Sensing Charge-Coupled Device (MAS-CCD) can perform multiple independent charge measurements with each amplifier, and the measurements from multiple amplifiers can be combined to further reduce the readout noise. We will show results obtained for sensors with 8 and 16 amplifiers per readout stage in new readout operations modes to optimize its readout speed. The noise reduction capability of the new techniques will be demonstrated in terms of its ability to reduce the noise by combining the information from the different amplifiers, and to resolve signals in the order of a single photon per pixel. The first readout operation explored here avoids the extra readout time needed in the MAS-CCD to read a line of the sensor associated with the extra extent of the serial register. The second technique explore the capability of the MAS-CCD device to perform a region of interest readout increasing the number of multiple samples per amplifier in a targeted region of the active area of the device.
Detectors with sub-electron noise open new possibilities for the spectroscopy of Earth-like exoplanets, probing the faintest signatures of dark energy and dark matter with high-redshift galaxies, and observing fast-evolving transients. Multi-amplifier sensing (MAS) charge-coupled devices (CCDs) offer the capability to achieve ultra-low readout noise floors together with a readout rate comparable to current CCDs employed in observatories. This is achieved by distributing a chain of Skipper floating-gate amplifiers along the serial register, allowing charge to be read repeatedly, non-destructively, and independently. We show recent progress in optimizing the MAS CCD for use in astronomy. These include reducing noise to sub-electron levels with faster read times than Skipper CCDs, optical characterization results, and a discussion of the range of astronomical science cases and facilities that would be enabled by MAS CCDs.
We present the development of a Skipper Charge-Coupled Device (CCD) focal plane prototype for the SOAR Telescope Integral Field Spectrograph (SIFS). This mosaic focal plane consists of four 6k × 1k, 15 μm pixel Skipper CCDs mounted inside a vacuum dewar. We describe the process of packaging the CCDs so that they can be easily tested, transported, and installed in a mosaic focal plane. We characterize the performance of ∼ 650μm thick, fully-depleted engineering-grade Skipper CCDs in preparation for performing similar characterization tests on science-grade Skipper CCDs which will be thinned to 250μm and backside processed with an antireflective coating. We achieve a single-sample readout noise of 4.5 e− rms/pix for the best performing amplifiers and subelectron resolution (photon counting capabilities) with readout noise σ ∼ 0.16 e− rms/pix from 800 measurements of the charge in each pixel. We describe the design and construction of the Skipper CCD focal plane and provide details about the synchronized readout electronics system that will be implemented to simultaneously read 16 amplifiers from the four Skipper CCDs (4-amplifiers per detector). Finally, we outline future plans for laboratory testing, installation, commissioning, and science verification of our Skipper CCD focal plane.
The Skipper is a special type of charge-coupled device (CCD) that allows pixel measurements with sub-electron noise levels due to its non-destructive readout operation. Over the last decade, these sensors have been used as particle detectors on a variety of experiments, such as the direct detection of galactic dark matter and neutrino experiments. Skipper CCD achieves low-noise by reading multiple times, and sequentially, the pixel charge packet, which translates to longer readout times. This becomes a limiting factor for those applications that require sub-electron detection and faster readout speeds. A novel analysis method for reducing the total pixel readout time is presented in this work. The method relies on analyzing the time-domain properties of the video signal including the clock feedthroughs and their shapes to optimize the clock transitions that define the pixel. The analysis technique is experimentally demonstrated using a standard scientific detector and also with a Skipper CCD with single photon sensitivity. In both cases the sensors are operated and readout using the Low Threshold Acquisition (LTA) controller with an updated firmware for faster clock sequencing. A good compromise between noise performance and total readout time was achieved. This will allows the use of the Skipper CCD and/or the LTA for astronomy, quantum imaging, and other applications that require faster readout times than previous uses of the sensor and the controller.
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