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Introduction

Introduction. An instability of the current generated by the HV boards (A3512N) has been observed during the first runs of the MTCC The Imon of all the boards showed a drift of about 1-2 m A in 4-5 days

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Introduction

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  1. Introduction • An instability of the current generated by the HV boards (A3512N) has been observed during the first runs of the MTCC • The Imon of all the boards showed a drift of about 1-2 mA in 4-5 days • The offset of every channel changed after any hardware reset/power cycle of the system but not after any software power cycle. • The instability was in the generated current or in the monitoring current ? • The effect was due to the chambers ? To the HV cable or connectors ? To the grounding ? Or the the boards (more realistic solution)

  2. What we have seen during the MTCC POWER CYCLE Imon History plot during MTCC

  3. HARDWARE SETUP AT BLG 904 We decided to make test (without chamber) in order to understand where The problem or the problems are. NOT VENTILATEDRACK0 VENTILATED RACK1 SY1527 B 1 B 2 B 3 B 4 A 16 76 A 16 76 resistors FAN resistors 4 boards corresponding to 10 HV channels Have been tested with a resistive charge for more then 10 days FAN

  4. A3512N Stability Test 31 c 31 c WITHOUT FAN UNIT 20 c 31 c WITH FAN UNIT 20 c 20 c Imon History plot with resistive charge

  5. POWER CYCLE TEST BOARD 1 CH0/1 POWER CYCLE B2 CHO/1 BOARD 1 CH2 NO FAN-31C NO FAN-31C BOARD 3 CH0/1 BOARD 2 CH0/1 FAN-20C NO FAN-31C BOARD 3 CH2 BOARD 4 CH0/1 FAN-20C FAN-20C

  6. RESET SOFTWARE AND HARDWARE SW HW As you can see from the history plot the Imon does not change at all when we made a software power cycle but change dramatically with an hardware reset

  7. Imon distribution for board with and without fan As you can see from the distribution the s of the ventilated channel is less than 0.2 microA as we required in the technical specification In total we have tested 10 channels for about 5 days and similar results has been found on the other channels

  8. Conclusions • We were able to reproduce the instability effect at BLG 904 using resistive charge  problem is not related to the detector/cable • Measuring independently the current on the ground wire we understood the instability was on the monitored current (Imon) and not on the generated current. • An increasing current has been seen in every tested channel after about 36 hours. The effect continues for days. • The increase let us suspect to a thermal drift of some components and so we begin to use the CAEN fan unit to ventilate the boards. • Using the fans the board temperature went down from 31oC to 20oC and after 4 days Imon was very stable. • The s of the Imon distribution of the ventilated boards is 0.2 mA and it was twice without fan. • Software power cycle do not affect the Imon (offset is constant) • Hardware power cycle of any board present in the EASY crate affect the offset of all the boards in the crate. • CAEN got all the results and is now trying to reproduce them in their lab and to find solution. We will meet CAEN engineering in two week.

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