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Transcript
Simulating Noise and Crosstalk problems with GEM detectors Matti Rahkala, HIP. Part One Comparing of different Order Low Pass Filters. Smoothing High Voltage source output. Frequency response of 1 to 4 Order RC-filters. Equal amount of the sum of Resistance and Capacitance 1.0V 0.8V 0.6V 0.4V 0.2V 0V 100Hz V(Out4) V(Out3) 1.0KHz V(Out2) 10KHz 100KHz V(Out1) Frequency 1.0MHz 10MHz The same, but at Log scale. 3800 times improvement (72 dB) at 1 MHz between 1. and 4. order filter 10V 1.0V (1.0000M,1.5916m) 1. Order Filter 1.0mV 1.0uV (1.0000M,417.920n) 4. Order filter 1.0nV 10pV 100Hz V(Out4) V(Out3) 1.0KHz V(Out2) 10KHz 100KHz V(Out1) Frequency 1.0MHz 10MHz Impulse response. Equal V(t)*dt integrals. Decay time vs. Amplitude 1.5V 4. Order 3. Order 2. Order 1.0V 1. Order 0.5V 0V 0s V(Out4) 50us V(Out3) V(Out2) 100us V(Out1) 150us 200us Time 250us 300us 350us 400us Part two. Noise and Crosstalk simulation of the GEM Strips Frequency response of the GEM Strips 1.0KV Output 1.0V Strip Voltage First adjacent Strip Voltage 100uV 2. adjacent Strip 10nV 3. adjacent Strip 1.0pV 1.0Hz V(B3) 10Hz V(B2) V(B1) 100Hz V(In) V(Out) 1.0KHz 10KHz Frequency 100KHz 1.0MHz 10MHz 100MHz 1 Resistor – Capacitor contribution to The output Noise Level 1.5m 2 80uV 1.428 mV RMS Output Noise density, V/SQRT(Hz) RMS Output total noise as fuction of upper Frequency 60uV 1.0m 40uV 0.5m 20uV 0 >> 0V 1.0Hz 1 10Hz 100Hz 1.0KHz SQRT(S(NTOT(ONOISE))) 2 V(ONOISE) 10KHz Frequency 100KHz 1.0MHz 10MHz 100MHz Cont … Fighting against Noise 1. Detecting and attenuating the Common mode Noise Current 2. Forgotten enemy – microfonic phenomena. It needs furter investigations with a proper analysig tools. I propose use of Acceleration sensors and cross correlation measurement as an analytical tool. 3. Last but not least; Tribo electricity. Huge problem if ignored with measurement Setup. The Triboe effect is easy to demonstrate. It gives Huge noise response. 1. Power Supply Noise Common mode current coming from Power supply. Measured by toroidal current transformer. 2 mA pp (top trace) Corresponding Charge Amplifier output noise coupling. CM to normal mode Noise pick up. (Bottom trace) HF-Noise envelope Before attenuation ferrites. Slow sweep, 8 mVpp Noise envelope at Amplifier output. Sniffer tool. Simply toroidal transformer. 2 rounds secondary winding- 50 ohm termination. Simply filter. 1.64 mVpp noise at output Two rounds 1.593 mVpp Noise Level Three rounds. nine ferrites. 1.050 mVpp noise output Some conclusions and Recommendations Don’t use switching power supplies if you can avoid it. CM-transformers (ferries) helps sometimes. CMnoise source impedance is too high for filters alone. Noise Current takes lowest impedance path to ground. The Art is: With Ferrites you can steer CM-noise Current to choose less hazardous path to the Ground. Ground Noise, You can’t attenuate it much but You can steer it to the harmless path!