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Humidity effects in SSD

Humidity effects in SSD. ITS Ventilation machine. On Feb 19 th at 22:00 the ITS ventilation machine has been switched off for SDD injector tests Concurrent increase of outside humidity Effects on SSD: 5 HV trips in the following 8h (5 ladders off)

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Humidity effects in SSD

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  1. Humidity effects in SSD WRC meeting - 1/3/2011

  2. ITS Ventilation machine WRC meeting - 1/3/2011 • On Feb 19th at 22:00 the ITS ventilation machine has been switched off for SDD injector tests • Concurrent increase of outside humidity • Effects on SSD: • 5 HV trips in the following 8h (5 ladders off) • Increased bias current on 20 “high current” ladders • Increased noise on Sintef modules (P-sides) • On Feb 21st at 1200 the ventilation is back • Fast recovery of the ladders

  3. Treated-air route Pre-treated air CR5 ALICE Cavern ITS Ventilation Machine A side C side ITS SSD-C sensor SSD-A sensor = RH sensors WRC meeting - 1/3/2011

  4. Ventilation OFF: effects on humidity STOP START • C-SIDE • Relative Humidity in the manifold before SSD • 23% 38% in ~12h • A-SIDE • Relative Humidity inside the SSD barrel on the opposite side (outlet) • 17% 25% in ~36h WRC meeting - 1/3/2011

  5. Effect of increased humidity on SSD bias current STOP START • C-SIDE • Relative Humidity in the manifold before SSD • 23% 38% in ~12h • high current on all the problematic ladders • 5 current trips A601 bias current 110uA → 280uA in 12h 280uA → 110uA in 5h WRC meeting - 1/3/2011

  6. Current-Humidity correlation Similar behaviour for all the “Sintef ladders” (~20 out of 144) WRC meeting - 1/3/2011

  7. bias current and humidity SSD meeting March’10 seen in all normal Sintef ladders WRC meeting - 1/3/2011

  8. SSD meeting March’10 Humidity Effects: on global noise • firstly spotted in the average Noise evolution: global average Noise suppressed when Rel. Humidity < 15% 6 noise [rms ADC] P noise 25 R.H. [%] Relative Humidity (<15% 10-18/02) 5 20 15 4 10 N noise 3 5 10feb 18feb P noise noise [rms ADC] 6 • average noise on Sintef correlated with the R.H. • due to de-insulation effects on irradiated Sintef sensors 5 4 3 N noise WRC meeting - 1/3/2011 2 1 10 15 30 20 25 Relative Humdity [%]

  9. SSD meeting March’10 Humidity Effects: Sintef <Noise> Vs R.H. • Noise averaged over all (active) Sintef ladders • global noise: ~1 ADC channel gained at low humidity • single module noise: • @16%: P-noise down to acceptable values in many cases • both sides generally decreasing WRC meeting - 1/3/2011

  10. Conclusions • Rather dramatic influence of humidity on current • Affects mostly high-current ladders (“Sintef ladders”) • Non-Sintef ladders are not affected • Keeping the humidity low (15 % on SSD-A sensor): • is beneficial for Sintef current • allows to recover ~30 modules (low noise) WRC meeting - 1/3/2011

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