160 likes | 263 Views
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.
E N D
Simulating Noise and Crosstalk problems with GEM detectors Matti Rahkala, HIP.
Part OneComparing 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
The same, but at Log scale. 3800 times improvement (72 dB) at 1 MHz between 1. and 4. order filter
Impulse response. Equal V(t)*dt integrals. Decay time vs. Amplitude
Cont … Fighting against Noise • Detecting and attenuating the Common mode Noise Current • 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. • 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.
Some conclusions and Recommendations • Don’t use switching power supplies if you can avoid it. • CM-transformers (ferries) helps sometimes. CM-noise 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!