Extremely low noise integrated charge sensitive amplifiers for electrostatic influence based detectors for cosmic and terrestrial dust

• Applicants: Professor Dr.-Ing. Manfred Berroth; Privatdozent Dr.-Ing. Ralf Srama
• Subject Area: Electronic Semiconductors, Components and Circuits, Integrated Systems, Sensor Technology, Theoretical Electrical Engineering ; Astrophysics and Astronomy
• Term: from 2017 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 389806487

Dust is considered to be one of the most important components of the Universe. Our own solar system was created from what used to be an interstellar dust cloud 4.6 billion years ago. Dust-astronomy analyzes the properties of interstellar, cometary and asteroidal dust to gain a better understanding of the conditions during the creation of our solar system. By analyzing both the chemical composition and the trajectory of dust grains, future dust telescopes will deliver unprecedented details on the origin of the particles and will aid the search for organic molecules in space. Concurrently research focuses on detectors to analyze dust on Earth and on lunar surfaces, ena-bling the precise measurement of suspended dust.Internally the dust detector consists of multiple sensors, of which the influence-charge based trajectory-detector is one of the most important ones. Simplified, this detector can be considered as a number of grids consisting of several isolated wire-electrodes. Each electrode is connected to a charge sensitive amplifier (CSA). By evaluating the transient charges influenced in the electrodes by UV-light charged particles the speed and the direction of flight of the particle can be calculated. The biggest challenge in designing these detectors is presented by the very low charge of the particles, starting at 35 elementary charges for future dust detectors. Additionally, new dust detector projects demand heavily increased bandwidths. Researching potential measures to reach both of these requirements in CSAs presents the primary goal of this proposal. Due to the large variety of the speed of the particles the proposal defines three frequency bands covering the range form 7 Hz to 50 MHz. For higher frequencies, starting at 10 kHz, a system-wide analytic description and optimization of the system is intended. A further point of research consists of designing amplifiers, which can be matched to detectors with different capacitance values. At the same time the maximum operating frequency is meant to increase from 10 MHz to 50 MHz. Special attention is given to the frequency range that spans from 7 Hz to 300 kHz and represents particles moving on planetary surfaces. One of the main focus points of the proposal consists of improving the flicker noise amplifiers experience at these frequencies. While classic methods to improve the low frequency noise do not work in CSAs, Switched Biasing via bulk switching appears to be a potential measure to reduce this noise in CSAs. Therefore the planned project aims at em-ploying this technique in low frequency dust detectors for planetary surfaces. If successful, accord-ing to the knowledge of the authors, this would be the first successful application of active flicker noise suppression in CSAs.

• DFG Programme: Research Grants
• Co-Investigator: Dr.-Ing. Markus Grözing