A Readout Electronics System for GEM Detectors IEEE NPSS Real Time Conference 2009 A Readout Electronics System for GEM Detectors Zhi Deng, Yinong Liu, Guanghua Gong Dept. of Engineering Physics, Tsinghua University IHEP, Beijing, China, May 10-15,2009
GEM Detectors GEM-TPC @ Tsinghua
Architecture of Readout Electronics electrons Readout pads CASA Commercial ADC (10bit, ~10MSPS) FPGA (DSP) DAQ Detector Analog Front-ends Digital Back-ends
CASA: the Front-end ASIC CSA Gain Stage 1st Shaper 2nd Shaper Variable value of C, giving different charge gain, together with matched size of the MOS transistor A dummy shaper amplifier, transfer signals to differential A fully differential amplifier, with class-AB output stage
Specifications of CASA Input Charge 10-1500fC SNR for MIP >20:1 Gain (Differential) 1-28mV/fC, adjustable Shaping Time (t) 25-100ns, adjustable Output Swing 2 V p-p, differential Drive Load 10pF Crosstalk <1% Power Consumption <10mW/ch
Chip Performance Test Input Protection Circuits CASA in CPGA package Power: 8.9 mW/ch Crosstalk: <0.98%
Programmability Programmable gain Programmable t Adjustable baseline
Noise Performance Noise@ Different gain Noise@ Different t
Linearity
With GEM detector COOL-X X-ray Generator (peak @~8keV) GEM detector CASA and buffer chips
Sampling and DSP Board Input Buffer AD9212 CLK Xilinx XC4VSX35
Sampled Noise Spectrum Normalized Power Spectrum Density Continuous Frequency /Hz f-3dB=100M
The Impact to SNR no pre-filter tr,preamp =5ns with pre-filter
Test Results
Summary A waveform sampling readout electronics system has been developed for GEM detectors, using a front-end ASIC and commercial ADC and FPGA chips. The front-end ASIC has been tested and work successfully. The sampling and DSP board has been designed and will be tested soon. The dependence of SNR with the sampling frequency has been quantitatively studied, which is very important for control of power consumption.