1

WRC meeting - 1/3/2011

Humidity effects in SSD

Mino for SSD

WRC meeting - 1/3/2011

2

ITS Ventilation machine

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

Mino for SSD

WRC meeting - 1/3/2011

3

Treated-air route

ALICE Cavern

CR5

Mino for SSD

ITS Ventilation Machine

ITS

SSD-C sensor

SSD-A sensor

Pre-treated air

A side C side

= RH sensors

WRC meeting - 1/3/2011

Ventilation OFF: effects on humidity

4

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

Mino for SSD

WRC meeting - 1/3/2011

Effect of increased humidity on SSD bias current

5

A601 bias current110uA → 280uA in 12h280uA → 110uA in 5h

● high current on all the problematic ladders● 5 current trips

STOP START C-SIDE Relative Humidity in

the manifold before SSD

23% 38% in ~12h

Mino for SSD

WRC meeting - 1/3/2011

6

Current-Humidity correlation

Mino for SSD

Similar behaviour for all the “Sintef ladders” (~20 out of 144)

WRC meeting - 1/3/2011 Mino for SSD

7

bias current and humidity

seen in all normal Sintef laddersSSD meeting March’10

WRC meeting - 1/3/20118

Humidity Effects: on global noise● firstly spotted in the average Noise evolution: global average Noise suppressed when Rel. Humidity < 15%

● average noise on Sintef correlated with the R.H.● due to de-insulation effects on irradiated Sintef sensors

Relative Humidity(<15% 10-18/02)

P noise

N noise

10feb

18feb

3

4

5

6

1510

5

20

25

R.H. [%]

noise[rms ADC]

N noise

P noise

4

3

2

1

5

6noise[rms ADC]

10 3015 20 25

Relative Humdity [%]

Mino for SSD

SSD meeting March’10

WRC meeting - 1/3/20119

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

Mino for SSD

SSD meeting March’10

WRC meeting - 1/3/2011

10

Conclusions

Mino for SSD

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)