Speaker
Description
The Low-Energy Polarization Detector (LPD) represents one of the effective payloads for the Polar-2 mission, characterized by wide field of view and large sensitive area capabilities. The primary objective of the LPD is effectively to measure low-energy X-ray polarization in the gamma-ray bursts. The LPD consists of 81 detector units, each containing a pixel sensor, a gas microchannel plate (GMCP), a detector cavity and an environmental monitoring sensor. The pixel sensor is responsible for collecting and processing charges amplified by GMCP for imaging. In the space, the X-ray radiation from gamma-ray bursts undergoes rapid fluctuations within a short period, while energy resources are limited and there is significant heat dissipation pressure.
Hence, the pixel sensors are needed to possess the features of large arrays, high spatial resolution, high energy resolution, and fast readout capabilities at the low power consumption. A pixel sensor named Topmetal-L is an optimized large-area pixel sensor designed for space applications, with a chip size of 16.9mm × 24.0mm and consisting of 356 rows × 512 columns, with a pixel pitch of 45µm. The pixel circuit includes a low-power, low-noise folded cascode amplifier to achieve a high signal-to-noise ratio for energy information. It also features a feedback structure with a 1fF capacitor and an NMOS in parallel to provide amplification and adjustable decay time. Furthermore, a two-stage source follower readout structure is employed to minimize readout crosstalk. The gain of the pixel readout channel is 122mV/ke-, and the ENC is 20.0e-@1ke-. Total chip power consumption is 820mW. A checkpoint readout method for pixel array has been proposed to address polarization detection issues. This method improves readout speed while reducing power consumption, with the speed enhancement and power savings depending on the scanning interval. The GDS file of Topmetal-L has been submitted for fabricating in July 2023.
| Submission declaration | Original and unplublished |
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