Michael Bloom: Kings College LondonSupervisors

Paolo Petagna and Karl Aaron GillSpecial Thanks to Duccio Abbaneo

And all the CMS Tracker Team

Environmental Monitoring of CMS Tracker Volume

Due to radiation damage the silicon detectors become less effective. The effects can continue to get worse with time even when the detector is not in use (reverse annealing).

For this reason the tracker must be cooled during its operation, and also during maintenance.

It is thus necessary to keep the humidity low inside the tracker to avoid condensation (humidity can severely damage silicon detectors and electronics parts).

For this reason the tracker volume is sealed and flushed through with dry air or nitrogen.

Long term radiation damage

Humidity MeasurementsIt is necessary to have accurate

measurements of humidity inside the volume, to monitor the correct functioning of the dry gas ventilation.

So sensors were needed which were Radiation HardSmall in size and mass.

Due to these unusual requirements only one sensor was found which fitted the criteria (after a long search).

The HMX.The sensors are Wheatstone

bridges on a block of composite which changes shape with humidity.

There are hundreds of these throughout the tracker volume.

Usually each sensor has to be pre-calibrated. However this was not possible before the installation of the sensors.

For this reason a small number of calibrated non radiation hard sensors (Honeywell) where inserted into the volume to act as “standard candles” for the HMX’s (will be damaged after some irradiation).

My work has been to look through data taken over the past year during Tracker integration and find useful periods in terms of temperature and humidity and use the data from the Honeywell sensors to calibrate the HMX’s.

Fig: Wheatstone Bridge.

Conversion to Useful Values

1 2

BIAS

C C ADCB

V

1 2

3

B H H TRh

H

17.502240.97 ln

100 240.9717.502

17.502 ln100 240.97

DP

Rh TT

TRh T

T

The Calibration Every moisture sensor must

be coupled to a corresponding temperature sensor to apply the appropriate correction to its output.

The relative humidity Rh can be calculated from the DP measurement of the HIH’s.

Sets of values of - Bridge (from HMX)- Rh (from HIH)- T (from dedicated sensor)

can be used to fit for the HMX calibration constants

Temperature(ºC)

Rh(%)

0 10 20 30

0

20

-20

Results

               

  HMX Name H1 H2 H3 Error in Rh  

  1 RH MONITOR_in_Zpf_TOP_1 -19.825232 0.537750 4.838761 11.88%  

  2 RH MONITOR_in_Zp_Xm_BH_2 -7.274002 0.089599 0.341362 2.72%  

  3 RH MONITOR_in_Zpf_BOT_3 -12.121781 0.142241 0.361109 2.74%  

  4 RH MONITOR_in_Zp_Xp_BH_4 -7.737203 0.080506 0.355576 1.98%  

  5 RH MONITOR_in_Zmf_TOP_5 -8.407855 0.071818 0.451856 4.94%  

  6 RH MONITOR_in_Zm_Xm_BH_6 -9.507491 0.084917 0.377926 2.94%  

  7 RH MONITOR_in_Zpn_TOP_7 -42.920213 0.632956 17.725364 16.99%  

  8 RH MONITOR_in_Zpn_BOT_8 -7.096687 0.073780 0.288337 3.44%  

  9 RH MONITOR_in_Zmn_TOP_9 3.620965 -0.224137 1.213385 32.20%  

  10 RH MONITOR_in_Zmn_BOT_10 -8.131568 0.114518 0.481394 11.80%  

  13 RH MONITOR_in_Zmf_BOT_13 -8.785692 0.047156 0.186176 3.46%  

  14 RH MONITOR_in_Zm_Xp_BH_14 -6.092944 0.081483 0.316845 3.42%  

               

Results

               

  HMX Name H1 H2 H3 Error in Rh  

  1 RH MONITOR_in_Zpf_TOP_1 -19.825232 0.537750 4.838761 11.88%  

  2 RH MONITOR_in_Zp_Xm_BH_2 -7.274002 0.089599 0.341362 2.72%  

  3 RH MONITOR_in_Zpf_BOT_3 -12.121781 0.142241 0.361109 2.74%  

  4 RH MONITOR_in_Zp_Xp_BH_4 -7.737203 0.080506 0.355576 1.98%  

  5 RH MONITOR_in_Zmf_TOP_5 -8.407855 0.071818 0.451856 4.94%  

  6 RH MONITOR_in_Zm_Xm_BH_6 -9.507491 0.084917 0.377926 2.94%  

  7 RH MONITOR_in_Zpn_TOP_7 -42.920213 0.632956 17.725364 16.99%  

  8 RH MONITOR_in_Zpn_BOT_8 -7.096687 0.073780 0.288337 3.44%  

  9 RH MONITOR_in_Zmn_TOP_9 3.620965 -0.224137 1.213385 32.20%  

  10 RH MONITOR_in_Zmn_BOT_10 -8.131568 0.114518 0.481394 11.80%  

  13 RH MONITOR_in_Zmf_BOT_13 -8.785692 0.047156 0.186176 3.46%  

  14 RH MONITOR_in_Zm_Xp_BH_14 -6.092944 0.081483 0.316845 3.42%  

               

Results

Before Calibration After Calibration

Further WorkAnalysis of more data to improve fitting.The calibration of the Monitor HMXs were focused on but there

are still many in the sub detectors which need to calibrated.The calibration must be implemented in PVSSThe use of sniffer pipes to monitor humidity must finalised.

Thank you for your time!Questions?