2. CMS - PAVIA1 Engineering Design Review RPC - BAKELITE

3. CMS - PAVIA2 3.1 THE MATERIAL We have investigated and measured three main physical parameters of the bakelite: the volume resistivity  as a function of Temperature and Humidity the average roughness R a the relative dielectric constant  r as a function of the input frequency We also have investigated how the factory parameters are related to the sheets resistivity value.

4. CMS - PAVIA3 QualityControl Factory Main Parameters: Type of Paper Flow Resin Volatile Heating Temperature Pressing Temperature Resin Reactivity How much the resin spreads out on the paper foil Percentage of resin in the paper Resin   Percentage of additives Volatile   GOES

5. CMS - PAVIA4 RESISTIVITY MEASURE Needs good electrical contact between electrodes and bakelite We have tried several options for the contact - among other: sponge with water antistatic foam (with and without water) conductive gel conductive rubber Brass Electrodes Upper 5 cm Lower 10 cm for guard ring option

6. CMS - PAVIA5 How to measure  ~ 10 10 - 10 11  cm R = 10 or 100 k    = k V 0 /(V/R) k = geometrical factor (98.17) V 0 = 500 Volts V0V0 V R Constant pressure (3 atm) on the electrodes by means of pistons

7. CMS - PAVIA6 V0V0 V R R HV distribution: CAEN SY 127 Reading through Nat. Inst. FIELDPOINT FP-100 or through a 617 Keithley programmable electrometer (via gpbi ) and LabView 5.0

8. CMS - PAVIA7 Conductive rubber vs cloth and water for 3 bakelite samples V1 C or V2 C (mV) V R (mV) Normalisation factor to water : 0.25 V R /V1 C V R /V2 C V1 C /V2 C V0V0 V R R V0V0 V1 C R V0V0 V2 C R

9. CMS - PAVIA8 Resistivity measurements at the factory 0 prototype

10. CMS - PAVIA9 View of the pistons driven by a manual air valve 0 prototype

11. CMS - PAVIA10 The manual switch for the serial read-out 0 prototype

12. CMS - PAVIA11 Aging Studies ``Natural’’ Aging  vs Temperature  vs Humidity  vs Time ``Radiation” Aging gamma irradiation neutron irradiation

13. CMS - PAVIA12   x  11 )  cm H (%) Resistivity vs Humidity We have normalized at 20 C first Max  % variation ~ 7% with a  max H = 5 %

14. CMS - PAVIA13  (x 10 11 )  cm H (%) Without temperature correction  = (1/  ) (d  / d T) Max  % variation ~ 10%

15. CMS - PAVIA14 In all our data a temperature normalised value is usually given at T=20 C following this curve. Temperature Normalisation Multiplying factor an effective  value has to be multiplied for to obtain  at T=20 C

16. CMS - PAVIA15 Resistivity as a function of temperature Note also the ``inertia” of the bakelite in following the temperature change  (x 10 11 )  cm T (C) Here temp starts to decrease while  is still constant Then also  starts to increase

17. CMS - PAVIA16 Resistivity measurement made by ATLAS group

18. CMS - PAVIA17

19. CMS - PAVIA18 Comparison with ATLAS measurements on a subsample of the pre-production set

20. CMS - PAVIA19 Results on preproduction samples We have measured the resistivity of some 130 bakelite panels in different places and in different conditions to check their behaviour in a medium time range. The following plots refer to foils of different sizes and for melamine and/or phenolic plates

21. CMS - PAVIA20

22. CMS - PAVIA21 Resistivity (at T=20 C) for Melamine foils. Size :160 cm x 320 cm At the factory At General Technica after 2 months panels on the pallets

23. CMS - PAVIA22 Resistivity (at T=20 C) for Phenolic foils. Size :130 cm x 320 cm At the factory At General Technica after 2 months panels on the pallets

24. CMS - PAVIA23

25. CMS - PAVIA24

26. CMS - PAVIA25

27. CMS - PAVIA26 Dielectric behaviour of the bakelite as a function of the input frequency signal tg  Rp Cp  rr Rp Cp

28. CMS - PAVIA27 Resistivity as a function of the input frequency

29. CMS - PAVIA28 Systematic Automatic measurement of the resistivity of a bakelite sample as a function of the time. SETUP: a piston with conductive rubber is continuously measuring the resistivity of a bakelite sample after a predetermined set of measurements the piston moves up for a fixed time and back down on the sample for the next cycle of measures. reading through FIELDPOINT FP-100 interface driven by LabView. Number of cycles, number of measures within a cycle, time between cycles and time between measurements are supplied by the user Automating reading of Temperature and Humidity

30. CMS - PAVIA29 Systematic: 800 cycles of measures, 10 measures/cycle, 10 sec after each measure (~ 26 hours). The resistivity (at T=20 C) of a phenolic sample as a function of time is normalised to the first value and plotted (left scale). The recorded value of the humidity is also shown (right scale) H=47.5 % H= 53 %

31. CMS - PAVIA30 Histogram distribution from the previous plot Temperature (C) Humidity (%)

32. CMS - PAVIA31 Another example (melamine) for which instead the humidity has changed only from 45 % to 46.5 % (only 294 cycles)

33. CMS - PAVIA32 Histogram distribution of the previous plot. Temperature

34. CMS - PAVIA33 Roughness Quality Qualitative view of the surface of the new improved bakelite. The pixel matrix greyscale of a micropictrue of the bakelite surface is shown

35. CMS - PAVIA34 Automatic Station for Resistivity measurement mechanics and controls electronics and DAQ