Supervisors : Petra Riedler and Vito Manzari

Many thanks to : Michele Morel, Michele Caselle, Andre Augustinus, Cesar Torcato De Matos

CHARLES Gabriel

OPERATING CONDITIONS OF ALICE SILICON PIXEL DETECTOR

Outline

Operating conditions of ALICE SPD

Humidity effect on half-staves

Dew point in the ALICE cavern

1/8

Half-staves in ALICE

Measurements in laboratory

(1)

2/81) Dew point

What is the dew point ?

The dew point is the temperature at which the partial pressure of water vapor in the air is equal to its pressure of saturated vapor. (2)

Example : at ambient temperature 20°C and a relative humidity of 60% the dew point is 12.01°C.

The relative humidity (RH) is defined as the ratio of the partial pressure of water vapor compared to the saturated vapor pressure of water vapor at a given temperature.

10 28Dewpoint (°C)

Summer Student perception

Too dry(one drink is

needed, at least)

Perfect(drink is not necessary, but it is the perfect weather for

a drink at resto 1)

Uncomfortable

(best case : drink is compulsory)

1) Dew point

3/8ALICE and the Dew point

The difference decreases since March

How can it be explained ?

Difference between ambient temperature and dewpoint decreases from 12°C to 7°C

Cavern dew point follows the outside trend

But… it is just in average

(3)

1) Dew point

4/8ALICE and the Dew point

The difference can sometimes be as low as about 4°C.

Conclusion : investigate the humidity effects will explain the present and futur consequences of these operating conditions on the detector.

How is the heart of ALICE ? 5/82) Humidity effects

I(V) curves

6 curves for each sector of one side. 10 sectors, 2 sides so 120 curves.

a. In ALICE

No general trend and no important change

Lab-tests ? 6/82) Humidity effects b. Lab-tests

Pictures

Noisy pixels

I(V) curves Bus resistance

HS_143 bus pad HS_143 pixel pad

Conclusion 7/82) Humidity effects

There is no major change in the behavior of the detector since the breakdown of the LHC. The operating conditions have not affected the SPD. But for this kind of problem only long term study makes sense.

There is not yet any change in the behavior of the tested half-stave in the laboratory. Maybe we see the begining of some trend.

So now we have to continue the lab-test, wait for some change, or not and check if the same behavior is seen in the ALICE SPD.

1) Dew point

8/8References

(1) The ALICE experiment at the CERN LH. The ALICE Collaboration, K Aamodt et al 2008 JINST 3 S08002

(4) M. Balkanski and R.F. Wallis, Semiconductor Physics and Applications, Oxford University Press, reprinted 2007.

(3) Website for the Geneva temperatures : http://www.wunderground.com

FOR LISTENING

(2) Barenbrug, A.W.T., Psychometry and Psychometric Charts, 3rd Edition, Cape Town, S.A. : Cape and Transvaal Printers Ltd., 1974

The heart of the heart of ALICE

2) Humidity effects

Rout=43.6 cmLout=97.6 cm

SPD

SSD

SDD

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Dew point2) Humidity effects

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