The Volotek controller and its cable infrastructure in LHC: specifications, functional behavior, cable layout and results from cabling quality check

Transcription

1 The Volotek controller and its cable infrastructure in LHC: specifications, functional behavior, cable layout and results from cabling quality check Benoit Rio TE/VSC/ICM 1

2 Content Introduction Volotek specification Functional behavior Circuit overview Digital Power Filament Electrometer Triax cable specs and connectors Typical cabling layout in tunnel Measurements and cabling quality check 2

3 Introduction 3

4 Volotek specification Technical specification Description Pressure range Electron emission current Grid Voltage Filament (with tranformer box) Sensitivity electrometer Resolution electrometer Specification 10-4 Pa to Pa (10-6 to mbar) 0.2mA to 10mA (until 70mA in degassing) +150 to 200Vdc (measurement) +600Vdc fixed(degassing) 50V (measurement) 5V (degassing) Until 5A 100fA 12 bits 4

5 Functional behavior Front view Rear view 5

6 Functional behavior 3 modes of operation : Measurement Measure of the pressure by reading of ionization current Modulation Identification of residual current created by X-rays Degassing Grid heating for cleaning it 6

7 Functional behavior Operation in measurement (Ie = 4mA) Ifil 3A Ie Ic Vfil 50V Vgrid 150V 7

8 Functional behavior Operation in modulation (Ie = 4mA) Ifil 3A X-ray X-ray The modulator is fixed at the ground potential to attract the ionization current IRes Vfil 50V Vgrid 150V 8

9 Functional behavior Operation in degassing Ifil 5A The grid is cleaned by bombardment of electron The modulator and the collector are fixed to the grid potential Vfil 5V Vgrid 600V 9

10 Circuit overview of Volotek Block diagram Electrometer Digital card Backplane Power Filament Transformer Power supply 10

11 Circuit overview of Volotek Digital card 11

12 Circuit overview of Volotek Power Filament 12

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14 Circuit overview of Volotek Measure of emission current 14

15 Circuit overview of Volotek Electrometer 15

16 Circuit overview of Volotek -AOP LMC6001 : Ultra Ultra-Low Input Current Amplifier with input current of 25fA. - Adjustable gain between 10 6 at by command of relay. - Protection diode for input of AOP. 16

17 Circuit overview of Volotek Gain of 1. This AOP is use for inverted the signal in input (First AOP is inverting amplifier). 0 Ω 0 Ω 0 Ω ADC 14 bits with SPI communication. Sampling frequency is 1kHz. 17

18 Circuit overview of Volotek 2 Versions of Controller : Version B Version C The difference between versions are : Improvement of communication board (profibus signal amplification) Modification of power supply card (AC/DC power module) Modification of digital card (pinout connector, reference driver, layout, ) Modification of backplane card (pinout connector) Replacement of the second OPA in the electrometer (component obsolete) Modification of the grid power supply ( new PWM controller) 18

19 Number of gauges Circuit overview of Volotek Distribution of Volotek in the LHC Version of controller Version B 128 Version C 40 Quantity Version vs noise 20 Version B Version C 0 Version B Version C Gauge Noisy gauge Version of controller Noisy gauge (in %) Version B 41 % Version C 42.5 % The percentage of noisy gauges between version B and C is the same. The difference of the version isn t linked at noise 19

20 Triax cable specs and connectors Specification of the triax cable TCA3 Sheath Inner shield 2 Semiconductive layer Insulation Insulation Wrapping Wrapping Inner Shield 1 Inner conductor 20

21 Triax cable specs and connectors 21

22 Triax cable specs and connectors The cable has a good insulation resistance and allows low leakage currents 22

23 Triax cable specs and connectors Triax connector specification 23

24 Typical cabling layout in tunnel Wiring diagram Triax cable TCA3 Controller in the rack Power shielded cable between the controller and the transformer Transformer in the LSS Power shielded cable between the transformer and the gauge Gauge in the LSS 24

25 Typical cabling layout in tunnel Cabling in the LHC Controller in the UJ/US/UA Transformer near the gauge in the LSS Up to more than 300 meter of cable between controller and the gauge 25

26 Typical cabling layout in tunnel Typical cabling (example of P2) 26

27 Typical cabling layout in tunnel 27

28 Typical cabling layout in tunnel 28

29 Typical cabling layout in tunnel 29

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31 Measurements and cabling quality check Check of cable quality : Measurement of shield continuity with ohmmeter» Identify the discontinuity internal shield Measurement of cable quality with reflectometer» Identify the broken internal shield» Measure the cable length» Identify the number of broken cables and their lengths 31

32 Measurements and cabling quality check Measurement of shield continuity with ohmmeter 32

33 Measurements and cabling quality check Distribution of inner shield continuity Internal shield continuity ok Internal shield continuity nok Don t know (No access or other)

34 Measurements and cabling quality check Inner shield continuity 2% 29% 68% Internal shield continuity OK Internal shield continuity Nok Don't know (no access or other) 34

35 Measurements and cabling quality check Measurement of cable quality with reflectometer 35

36 Measurements and cabling quality check Example of graphic with reflectometer in P7 Good cable (Continuity between the shield) Bad cable (No continuity between the shield) End of cable External shield End of cable External shield Internal shield Shield break Internal Shield Distance (meter) Distance (meter) 36

37 Measurements and cabling quality check Length measurement at P7 P7 Reflectometer VAC Name Shielding continuity L ext shield L int shield diff L shield [m] [m] [m] VGI.172.7L7.B NO VGI.172.7L7.R NO VGI.392.6L7.B NO VGI.534.6L7.R NO VGI.53.6L7.B NO VGI.324.5L7.R YES VGI.210.5L7.B NO VGI.130.5L7.R NO VGI.454.4L7.B NO (BNC+BNC) VGI.456.4L7.R NO (BNC+BNC) VGI.193.4L7.B NO (BNC+BNC) VGI.193.4L7.R NO (BNC+BNC) VGI.454.4R7.B NO VGI.456.4R7.R NO VGI.130.5R7.B YES VGI.210.5R7.R YES (BNT) VGI.324.5R7.B NO VGI.53.6R7.R YES (BNT) VGI.534.6R7.B NO VGI.392.6R7.R NO VGI.128.7R7.B YES (BNT) VGI.128.7R7.R YES (BNT)

38 Measurements and cabling quality check Why the internal shield is cut? During the building of the LHC, the cables were extended to match the machine evolution. The cable extension has been realized with the BNC coaxial adapter. The BNC adapter doesn t have internal shield. 38

39 Measurements and cabling quality check 39

40 Measurements and cabling quality check What can we do Repair the cables Replace the cables. Use triaxial adapter. Mount a triaxial female connector. Mitigate the current in the shield Use capacitor box to limit the low frequency signal in the external shield. 40

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42 The Volotek controller and its cable infrastructure in LHC ANY QUESTIONS? 42

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