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Muon Detector Calibration System Review

This review outlines the proposal for the Muon Detector Calibration System (MDCS) and its funding, research & development, and the first flasher prototype. It also discusses the system requirements, flasher deployment, and flasher waterproofing and potting methods.

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Muon Detector Calibration System Review

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  1. V. Vorobel, MDCS review Muon Detector Calibration System reviewVit VorobelCharles University in PragueFaculty of Mathematics and Physics

  2. Outline V. Vorobel, MDCS review Muon Detector Calibration System proposal Funding of the project MDCS Research & Development First flasher prototype Summary

  3. V. Vorobel, MDCS review Muon Detector Calibration System proposal

  4. V. Vorobel, MDCS review http://juno.ihep.ac.cn/cgi-bin/Dev_DocDB/ShowDocument?docid=2716

  5. Muon Detector Calibration System (MDCS) V. Vorobel, MDCS review • PROPOSAL • MDCS is a multi-diagnostic tool: • PMTs gain monitoring • PMTs timing check • Monitoring of PMT efficiency influenced e.g. by Earth Magnetic Field • Water attenuation monitoring for variousl • PMTs position crosscheck • MDCS for JUNO should consist of • ~128 isotropic LED flashers • deployed in the Muon Detector and operated centrally from the Control Room. Each flasher consists of • 4 various LEDs (l, intensity) . f36 m 15 cm

  6. System Requirements V. Vorobel, MDCS review • Electronics • During the calibration run only one flasher is active at any time. • Controllable flashing intensity • ~1p.e. from tested PMT for gain calibration, • More p.e. for timing and attenuation monitoring. • Flashing length ~10 ns, time precision < PMT TTS (4-12 ns), frequency ~1kHz. • Distance between the flasher and electronics 100m. • Low power consumption (heating). • Deployment • Direct visibility between the flasher and PMT is required. • Areas which are served with individual flashers must overlap. • Redundancy for the case of a failure of some flashers. • Optics • Approximately isotropic light emission (+/-10%). • Chemicals • Waterproof and stability in aggressive ultrapure water. • Low pollution release to the ultrapure water. • Challenge – the system must reliably operate without chance for repairs in depth up to 40m of aggressive high purity water during the life of the experiment.

  7. PMTs efficiency and light attenuation monitoring V. Vorobel, MDCS review water attenuation PMT solid angle PMT directivity LED directivity PMT efficiency LED luminosity PMT signal PMT gain • Assuming that we know the corrections the signal amplitudes of individual PMTs generated by individual flashers provide • water attenuation coefficient • relative PMT efficiencies • relative flashers luminosities as a by-product • Monitoring of the relative PMT efficiencies can reveal possible failure or change in a single PMT channel caused e.g. by Earth Magnetic Field. • Water attenuation change would indicate water pollution. The system can partially localize the pollution source. Use of LEDs with various l may help in identification of the polluting chemical.

  8. Flashers deployment V. Vorobel, MDCS review Direct visibility between LED flasher and PMT is the main requirement. Number of flashers should be redundant for case of a flasher failure. Upper hemisphere 72 flashers fixed to bird cage. Lower hemisphere 56 flashers fixed to steel truss holding CD. The fixation is dependent on design of the bird cage and of the truss. 8 8 8 16 32 32 16 7 1 The numbers indicate how many flashers are positioned around the vertical axis of the JUNO experiment in a given height and distance from the vertical axis.

  9. LED flasher Each flasher contains 4 LEDs with drivers inside SS pipe f30x3x120. One Cable Cat 5e – 4 twisted pairs provide power supply as well as trigger signal for all 4 LEDs. LEDs: 1 Blue 420 nm, low intensity – gain (PMT sensitivity region) 2 Blue 420 nm, high intensity – timing, efficiency 3 UV ~360 nm – eventual pollution (bis-MSB absorption) 4 Red 660 nm – visual check during installation elastic filler solid filler Position of the LEDs and drivers inside the flasher is fixed to a skeleton. Skeleton is 3D-printed from ABS (Acrylonitrile Butadiene Styrene) Flasher interior is potted with acrylic and/or silicone.

  10. Flasher waterproof & potting V. Vorobel, MDCS review • The LED and the flasher PCB are waterproof sealed using a combination of solid and elastic potting compounds – transparent epoxy and silicone polymer. • Flasher potting steps: • Assembly of SS pipe with teflon diffuser, • Application of transparent filler, • Submerge the skeleton with LEDs and PCBs to the filler, • After curing of the transparent filler the elastic filler is added on top of it. • Requirements for the potting compound • Must be adhesive to cable. Adhesion to teflon diffuser and SS pipe is advantageous. • Water resistant • Transparent • Stable elastic filler solid filler

  11. Onechannelscheme Based on the system developed by BNL for DayaBay V. Vorobel, MDCS review Source in Electronics room 3V 1kHz TTL trigger signal together with -9V Power supply Cable 100m Different cable types tested - Coaxial RG58 - Twisted pairs UTP Cat.5e Both types do the job Underwater Flasher PCB Circuit developed by BNL J.S. Kapustinsky et al.: Nuclear Instruments and Methods in Physics Research A241 (1985) 612-613

  12. V. Vorobel, MDCS review Muon Detector Calibration System - scheme • Source in Electronics room • 3V 1kHz TTL trigger signal • bias -9V (0-10V) DC • 512 outputs to flashers • 1 output for PMTs Readout Trigger • Size 6U module in 19” rack • Development and production price: • Simple version • 8 800 EUR • Simple + delay measurement 13 200 EUR 15 km of cable in total Price 8 000 EUR The biggest unknown in the budget Comparable with all other costs Underwater Flasher PCB Circuit developed by Virginia Tech for Daya Bay Production price of 600 PCBs: 6 000 EUR

  13. Interfaces V. Vorobel, MDCS review Time link-up to PMTs. Integration to Data Control System. Logistics and storage. Space for test on site. Location of PC for MDCS control. Location of crate 6U, 19 inch in electronics room. Cleaning of flashers and cables. Flashers fixation – bird cage, steel truss. Cables – installation, fixation, space. Installation organization. Solution of the items depend on general planning.

  14. Schedule V. Vorobel, MDCS review The most important time limitation is that the installation and commissioning of the MDCS must be done in parallel with the Veto PMTs installation.

  15. V. Vorobel, MDCS review Muon Detector Calibration System Research & Development

  16. V. Vorobel, MDCS review Electronics The test of one channel setup with BNL flasher was successful. Generated flashes have rise-time comparable with PMT TTS. Cable CAT.5 EC is satisfactory. Need to make sure that the system does not interfere with the PMT system. Potentially, either cable or PCB or LED can emit EM field and induce a false PMT readout. Possible measures: Balanced signal – tested, works. Use antenna for investigation of setup design modifications. LED and PCB shielded in SS pipe, use of a grounded metalic mesh if needed. Cable delay measurement – TDR method (timedomainreflection) under consideration. • PMT signal risetime 4ns length 11 ns

  17. Flashers directivity V. Vorobel, MDCS review Diffusers of various shapes tested. Si PIN sensor on a turnable arm 10cm installed in a black box. Bigger diffuser → better isotropy payed by less light. Diamond shape f18mm → anisotropy 30%. Still space for improvement optimizing the diffuser shape.

  18. Diffuser materials - optical properties V. Vorobel, MDCS review Spectra of the light from LED 420 nm and 370 nm diffused in various materials were measured with spectrometer Ocean Optics USB4000. Silon and Delrin - strongly absorb the light and shift to longer l. Teflon and HDPE - no shift of l observed. HDPE absorbs less then Teflon. • Diffusers of various materials were tested. • Teflon - Polytetrafluorethylen (PTFE) • High Density Polyethylen (HDPE) • Silon - AlkalicPolyamid (PA6G) • Delrin - AcetalHomopolymer

  19. V. Vorobel, MDCS review First flasher prototype

  20. V. Vorobel, MDCS review Prototype components Stainless steel pipe f30x3x120 HDPE light diffuser HDPE plug to center the cable JUNO cable Cat 5e shielded 4 twisted pairs HD PE jacket LEDs: Blue, flasher driver Blue Red UV Skeleton is 3D-printed from ABS (Acrylonitrile Butadiene Styrene) The prototype contains only one LED (blue) equipped with the flasher driver PCB 3 LEDs (UV, blue, red) are in DC mode

  21. Prototype potting Curing: recommended 4h 65ºC or 1h 100ºC or 15min 150ºC, our procedure 48 h room temperature Before curing – viscosity 450 mPa.s, (like engine oil) After curing – very soft elastic gel (not liquid, not rubber), very adhesive, transparent Potting material: SYLGARD 517 Silicone dielectric gel two components Reference sample in glass vessel

  22. Flasher waterproof testing V. Vorobel, MDCS review • The flasher prototype in pressure tank full of salty water • 35 g NaCl/ 1 L water, 10 bars (equivalent to depth 100 m) • After 3 weeks • Visual check: blue, red and UV LEDs are shining • Flashings successfully observed with PMT in dark cabinet PMT LED SS cover with cable feedthrough and tire valve Acrylic cover allows to watch the flasher inside Acrylic table mirror

  23. Lessons from the first prototype V. Vorobel, MDCS review • Cable • Difficult to strip off the protection layers from the cable • Cable is very rigid. Probably, other then coaxial configuration of the flasher should be designed • Ethanol penetrates between the protection layers during cleaning – inhibits curing • Potting material • The liquid partially leaked during curing – need to seal the assembly, take care about ethanol contamination • The gel is very soft after curing – cable should be more fixed • Skeleton • Not easy assemblywith LEDs – design polishing

  24. Pending issues V. Vorobel, MDCS review Technology of cleaning of the components Choice of LEDs (l, luminous intensity, …) Optimization of shape and size of the diffuser ball Electronics development Optimization of the Flashers deployment in the Muon Detector Fixation of the Flasher pipe to JUNO construction Characterization Installation organization

  25. Summary V. Vorobel, MDCS review We propose the System for Calibration of Muon Detector. The System is multi-diagnostic tool capable to monitor gain, relative efficiency and timing of PMTs, eventually to monitor water attenuation for various l and to help to reveal a possible PMT positions mismatch. The system consists of 128 flashers, each containing 4 LEDs of various wave-lengths, which are deployed in the Muon Detector and operated centrally from the Control Room. Performed tests proved applicability of Flasher circuit developed in LBNL. Ongoing activities: optimization of diffuser shape, electronics development. Funding corresponds with the expected expenditures.

  26. V. Vorobel, MDCS review Backup

  27. V. Vorobel, MDCS review open circuit reflection

  28. V. Vorobel, MDCS review https://en.wikipedia.org/wiki/Electromagnetic_absorption_by_water

  29. V. Vorobel, MDCS review Attenuation length

  30. V. Vorobel, MDCS review cable beginning open circuit reflection short circuit reflection cable end

  31. V. Vorobel, MDCS review cable end

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