Noise on chambers M1R4 N.Bondar 19.12.2016

Chamber M1A4D Noisy and good channels RMS 19.15 RMS 3.76 45 ru 18 ru Total we have noisy chambers 32 on A-side and 18 on C-side

The noise origin on chambers M1R4 Electrical circuit of the chamber (simplified) Internal HV filter SPB +HV RET GND 100K 8Ohm 0.1K 2.2N 680pF HV signal by oscilloscope 20ns Amplitude 50mV Any HV level 5us Parasitic signal is produced by switching DC-DC convertor . There are two options for understanding why we have noise only for some chambers: - Different level of parasitic signal due to parameters variation - Wrong filter inside the chamber or poor connected

The noise on chambers M1R4 Proposed solution to fix the problem – additional filter on the output of the power module. Each filter has 4 identical channels . The filter prototype has R1=R2 = 470K, C1=1nF R1 R2 +HV RET GND C1 J1 Jumper J1 I used to understand where capacitors C1 should be connected.

The noise on chambers M1R4 The filter prototype used for tests. Resistors hidden inside the shrinkable tubes

The noise on chambers M1R4 Result of testing filter installed on the CAEN HV module . Chamber M1R4D FEB 0 RMS results under different conditions I2C 1 DIALOG 0 Ch Thres Rate(KHz) Mean RMS 01 079 004569.40 78.15 10.68 02 080 006806.30 79.52 19.35 03 080 003317.10 79.71 10.39 04 071 005610.80 70.21 19.05 05 079 002770.20 79.05 10.40 06 081 003880.70 79.98 18.76 07 080 002288.00 79.46 7.23 08 067 003648.80 67.07 13.56 09 068 002618.40 68.12 7.21 10 072 003622.60 71.52 12.70 11 080 003824.70 79.08 11.25 12 081 003864.70 79.87 18.18 13 071 005109.60 70.71 13.01 14 075 004757.50 73.72 19.34 15 075 005146.20 74.22 13.57 16 076 004847.10 74.20 17.94 1 2 3 4 6 5 RMS 3.2 4.61 2.39 3.45 2.34 3.23 2.3 3.16 2.6 3.46 3.21 3.48 3.76 3.03 RMS 3.18 4.91 2.33 3.76 2.58 3.19 2.59 3.47 3.45 2.64 3.17 3.75 3 RMS 3.55 4.91 2.75 3.76 2.58 3.2 2.59 3.47 3.45 2.63 3.17 3.75 3.46 2.99 RMS 3.54 4.91 2.91 3.75 2.59 3.76 3.47 2.58 3.77 2.64 3.52 4.05 4.33 3.17 RMS 3.55 5.19 2.9 4.03 2.58 3.76 2.59 3.47 3.77 2.63 3.75 4.05 4.33

The noise on chambers M1R4 Conditions: No filter Filter installed on chamber, Return and GND connected together on chamber HV on M1 filter on CAEN .Return and GND connected together HV on M1 filter on CAEN . Return and GND separated. Capacitors connected to GND HV on M1 filter on CAEN . Return and GND separated. Capacitors connected to Return 6 HV on M1 filter on CAEN . Return and GND separated. Capacitors connected to Return

HV-training Oleg 150 CMBs to be trained in WS ~40% done – work on A-side now CMBs on M5R3-M5R4 are seriously polluted after LS1: - current at negative polarity appears even below 1kV sometimes - removing takes up to few weeks