Design Of X-ray Polarization Detection Load Electronics System Based On Pixel Chip Topmetal-M2

Polarization detection of soft X-ray energy band(1-10 ke V)is of great significance in scientific research of target source model(dense stars such as black holes,magnetic field morphology and radiation mechanism)and relativistic jet and other astronomical phenomena.The soft X-ray micro structure gas pixel detection unit is designed according to the principle of "Photoelectric effect".The physical process of detection is divided into gas photoelectron interaction,ionization and drift,electron avalanche and electron collection.Topmetal-M2,developed by the Pixel Lab of Central China Normal University(PLA),has the ability of electronic collection.It is a large size array pixel detection chip based on the 130 nm CMOS double well process of domestic Huahong Hongli(GSMC).This chip is the key technology to complete X-ray polarization detection.The Low Earth orbit cube star used for X-ray polarization detection is mainly composed of solar panels,thrusters,antennas,specific loads,etc.Among them,the specific payload used for X-ray polarized astronomical observation is mainly composed of microstructural gas detectors and their readout electronics systems.The detector is composed of metal beryllium window,gas multiplication Microchannel plate detector(GMCP),high-sensitivity silicon pixel chip Topmetal-M2,ceramic base,etc.It has the advantages of rapid response time,easy transformation and research,radiation resistance,etc.This article mainly designs an X-ray polarization detection payload prototype readout electronics system,which includes a Topmetal-M2 pixel chip data acquisition board,an FPGA main control board,and a high-voltage board based on the A7504 N high-voltage module.The work completed in this article is divided into the following aspects:1.A hardware system for soft X-ray polarization detection of small payload electronics was designed,which includes a top-level PCB board for collecting Topmetal-M2 energy output channel data;Equipped with electronic devices such as FPGA,Ethernet PHY,FLASH,eMMC,CAN to control the load function of the main control PCB board;Use the A7504 n module to provide a high-voltage electric field on the bottom PCB board.The startup and configuration information of each module can be transmitted through communication on the upper computer platform,with a command transmission rate of 1Mb/s on the CAN bus and a data return rate of 3MB/s on UDP.2.A data processing algorithm has been designed,and the data volume of the detection unit running in orbit without compression is 288GB/day.The communication transmission bandwidth cannot meet the requirements,so online data processing is needed to reduce the transmission data volume.The algorithm module includes JESD204 B output data concatenation,frame header processing,effective data filtering,and multi-channel cache output;The final effective data compression transmission rate is 3.41MB/s.3.Designed a high capacity and error tolerant storage system module on board the satellite.This article combines the eMMC5.0 protocol to complete the initialization,read and write operations of eMMC devices.The designed BOOT startup block effectively solves the problem of load power failure and shutdown.And encapsulate the top layer of the storage module as a FIFO interface,facilitating inter module calls and later maintenance.4.According to the requirements of remote update of the system and radiation protection,a remote update function based on FLASH is designed,which uses FPGA as the master control and cooperates with UDP communication mode to complete the configuration file writing and power on independent reading configuration,replacing the traditional JTAG scheme and improving the configuration convenience.Considering the difficulty of manual maintenance and debugging in the space environment,adding XOR accumulation operations at the firmware level to improve the accuracy of writing configuration file data,and adopting the Multi Boot FLASH partitioning scheme,the load can continue to operate when there is an error in the configuration file,ensuring the stable operation of small loads.The small payload prototype designed in this article has been tested on the ground by X-ray and alpha sources for a long time,and the system runs robustly.Topmetal-M2 successfully detects and plots polarization tracks with different energies and angles at a scanning rate of 2.56 ms per frame,and the read and write rates in the storage system reach 9.65MB/s and 8.75MB/s,respectively,meeting the data transmission requirements.