1. M ICROFLUIDIC S CINTILLATION D ETECTORS 25.06.2015 // Pietro Maoddi DT Seminar: Microfluidic Scintillation Detectors 1 Pietro Maoddi Detector Technologies group, CERN Microsystems Laboratory 4, EPFL June 25 th 2015

2. O UTLINE IntroductionMain resultsConclusions 25.06.2015 // Pietro Maoddi DT Seminar: Microfluidic Scintillation Detectors 2 Scintillation detectors Project goals Intro to microfabrication Conclusions Outlook Detectors based on SU-8 Detectors based on Silicon Radiation damage studies

3. S CINTILLATION D ETECTORS Scintillator + Photodetector = Scintillation detector 25.06.2015 // Pietro Maoddi DT Seminar: Microfluidic Scintillation Detectors 3 Photodetector Electrical signal Particle Scintillator Light 1 2 3 4 5 6 x How to track the particle position?  Segment the detection volume The particle passed in position x=4

4. F IBRE D ETECTORS Principle 25.06.2015 // Pietro Maoddi DT Seminar: Microfluidic Scintillation Detectors 4 Scintillatin g core (n 1 ) Cladding (n 2 < n 1 ) Photons emitted above critical angle are guided Air (n = 1) Water (n = 1.33)

5. F IBRE D ETECTORS Principle Example: LHCb SciFi Large active area ~36 µm RMS spatial resolution ~2 p.e. per MIP per fibre 25.06.2015 // Pietro Maoddi DT Seminar: Microfluidic Scintillation Detectors 5 Scintillatin g core (n 1 ) Cladding (n 2 < n 1 ) Photons emitted above critical angle are guided 2 × 2.5 m 2 × 3 m Module section: 5 layers of Ø250 µm fibres Pictures: C. Joram, “LHCb SciFi, the new Fibre Tracker for LHCb”, ECFA High Luminosity LHC ExperimentsWorkshop. Aix-Les-Bains, France, 2014. url: http://goo.gl/xF8sL6 http://goo.gl/xF8sL6 xuv

6. F IBRE D ETECTORS Principle Example: LHCb SciFi Large active area ~36 µm RMS spatial resolution ~2 p.e. per MIP per fibre Defects may appear in fabrication Fibres need to be replaced upon damage 25.06.2015 // Pietro Maoddi DT Seminar: Microfluidic Scintillation Detectors 6 Scintillatin g core (n 1 ) Cladding (n 2 < n 1 ) Photons emitted above critical angle are guided 2 × 2.5 m 2 × 3 m Module section: 5 layers of Ø250 µm fibres Pictures: C. Joram, “LHCb SciFi, the new Fibre Tracker for LHCb”, ECFA High Luminosity LHC ExperimentsWorkshop. Aix-Les-Bains, France, 2014. url: http://goo.gl/xF8sL6 http://goo.gl/xF8sL6

7. C APILLARY D ETECTORS CERN RD46 collaboration (1990s) Glass capillaries filled with liquid scintillator  “Liquid core” scintillating fibres 25.06.2015 // Pietro Maoddi DT Seminar: Microfluidic Scintillation Detectors 7 Pictures: RD46 Status Report, CERN/LHCC 97-38, 1997 n glass ~ 1.49 n liquid ~ 1.62

8. C APILLARY D ETECTORS CERN RD46 collaboration (1990s) Glass capillaries filled with liquid scintillator  “Liquid core” scintillating fibres Defects may appear in fabrication Complex filling system 25.06.2015 // Pietro Maoddi DT Seminar: Microfluidic Scintillation Detectors 8 Pictures: RD46 Status Report, CERN/LHCC 97-38, 1997 n glass ~ 1.49 n liquid ~ 1.62

9. M ICROFLUIDIC S CINTILLATION D ETECTORS 25.06.2015 // Pietro Maoddi DT Seminar: Microfluidic Scintillation Detectors 9 Microfluidic channel filled with liquid scintillator defining an array of waveguides Photodetector pixel coupled to each channel end Scintillation light guided along microchannel and detected Photodetector array Microchannel Scintillation particle ( e -, p +, n, γ, …) electrical signal

10. M ICROFLUIDIC S CINTILLATION D ETECTORS 25.06.2015 // Pietro Maoddi DT Seminar: Microfluidic Scintillation Detectors 10 DAQ system Photo: J. Daguin 20 mm 15 mm First MSD prototype (A. Mapelli) Microchannels made by SU-8 photolithography filled with liquid scintillator Gold reflective coating (200 µm deep channel) MAPMT A. Mapelli PhD thesis Scintillation Particle Detectors Based on Plastic Optical Fibres and Microfluidics, 2011

11. M ICROFLUIDIC S CINTILLATION D ETECTORS Main advantages of MSDs Radiation resistance Liquid scintillator intrinsically radiation resistant… …and recirculation (substitution) easily possible Dimensional control Precise/reproducible geometries wrt traditional assembly  higher resolution Very thin detectors, minimal material budget  new applications 25.06.2015 // Pietro Maoddi DT Seminar: Microfluidic Scintillation Detectors 11

12. H ADRON T HERAPY Cancer treatment using particle beams (protons, heavy ions, neutrons, pions, …) More selective than radiotherapy  Less damage to healthy tissues 39 facilities worldwide ~100’000 patients treated as of 2012 Most facilities in US and Japan Many new centers in Europe, e.g. HIT (Germany), CNAO (Italy), ETOILE (France) 25.06.2015 // Pietro Maoddi 12 DT Seminar: Microfluidic Scintillation Detectors RadiotherapyHadrontherapy

13. O N -L INE B EAM M ONITORING Microfluidic detectors Thin, very «light» devices Excellent radiation hardness 25.06.2015 // Pietro Maoddi DT Seminar: Microfluidic Scintillation Detectors 13 Extremely thin microfluidic detector Real-time monitoring of the beam during patient irradiation possible Safer treatment Optimized beam time use Cost reduction Beam line end A. Mapelli, P. Maoddi, P. Renaud, WIPO Patent 2013167151 A1, 2013 Project funded for 1/3 by CERN’s Knowledge Transfer office for this application

14. D OUBLE L AYER MSD S 1 microchannel layer  1D spatial resolution 2 microchannel layers  2D spatial resolution Analogous to scintillating fiber detectors Needed in many applications Keeps advantages of single layer MSD (… but fabrication more complex) 25.06.2015 // Pietro Maoddi DT Seminar: Microfluidic Scintillation Detectors 14 A. Mapelli, P. Maoddi, P. Renaud, WIPO Patent 2013167151 A1, 2013

15. D ESIGN C ONSIDERATIONS Materials environmental requirements High radiation levels  radiation resistance Liquid scintillators  chemical compatibility High vacuum (in some applications)  mechanical resistance Materials technological requirements Compatibility with microfabrication techniques Optical quality: refractive index, reflectivity, transparency, smoothness… Dimensions Thinness vs. light yield trade-off Area: control of micropatterning over relatively large areas (several cm 2 ) 25.06.2015 // Pietro Maoddi DT Seminar: Microfluidic Scintillation Detectors 15

16. M ICROFABRICATION Fabrication performed at EPFL Micro and Nano Technology (CMi) Class 100 cleanroom (Maximum 100 particles of size 0.5 µm or larger permitted per cubic foot of air) Standard working substrate: silicon wafers Ø100 mm, 0.5 mm thick 25.06.2015 // Pietro Maoddi DT Seminar: Microfluidic Scintillation Detectors 16

17. M ICROFABRICATION Additive approachSubtractive approach 25.06.2015 // Pietro Maoddi DT Seminar: Microfluidic Scintillation Detectors 17

18. O UTLINE IntroductionMain resultsConclusions 25.06.2015 // Pietro Maoddi DT Seminar: Microfluidic Scintillation Detectors 18 Conclusions Outlook Detectors based on SU-8 Detectors based on Silicon Radiation damage studies Scintillation detectors Project goals Intro to microfabrication

19. SU-8 F OR MSD S Radiation resistant Compatible with liquid scintillators Mechanically resistant Relatively “light” (X 0 ~350 mm) Optically smooth and transparent (but high refractive index n~1.6) Used in other detector technologies 25.06.2015 // Pietro Maoddi DT Seminar: Microfluidic Scintillation Detectors 19 Pictures from P. Maoddi, A. Mapelli, S. Jiguet and P. Renaud. SU-8 as a Material for Microfabricated Particle Physics Detectors, Micromachines, vol. 5, num. 3, p. 594-606, 2014

20. S INGLE L AYER SU-8 D EVICES SU-8 lithography over a sacrificial layer on 2 wafers Mylar film Aluminum layer* Bonding of the devices SU-8/SU-8 bonding Release of the devices Mechanical Wet etching Anodic dissolution* 25.06.2015 // Pietro Maoddi DT Seminar: Microfluidic Scintillation Detectors 20 «Bottom» wafer «Top» wafer Deposition of a sacrificial layer Patterning of SU-8 device bottom Patterning of SU-8 device top Patterning of SU-8 microchannels Wafer bonding Sacrificial layer removal Free-standing thin SU-8 device 110 µm total thickness (30 + 50 + 30) 200 µm * Preferred process

21. S INGLE L AYER SU-8 D EVICES SU-8 lithography over a sacrificial layer on 2 wafers Mylar film Aluminum layer* Bonding of the devices SU-8/SU-8 bonding Release of the devices Mechanical Wet etching Anodic dissolution* 25.06.2015 // Pietro Maoddi DT Seminar: Microfluidic Scintillation Detectors 21 Free-standing thin SU-8 device 110 µm total thickness (30 + 50 + 30) 200 µm * Preferred process Al-coated Mylar (clamped) Silicon

22. D OUBLE L AYER SU-8 D EVICES Extension to two microchannel layers Cr and Al sacrificial films Selective dissolution (HCl, KOH) Bonding optimization 25.06.2015 // Pietro Maoddi DT Seminar: Microfluidic Scintillation Detectors 22 Pictures: P. Maoddi, A. Mapelli, S. Jiguet and P. Renaud. SU-8 as a Material for Microfabricated Particle Physics Detectors, Micromachines, vol. 5, num. 3, p. 594-606, 2014

23. C HALLENGES I N SU-8 MSD S SU-8 R.I. higher than that of commercial LS  optical coating needed Alternative solution: high R.I. liquid scintillator 25.06.2015 // Pietro Maoddi DT Seminar: Microfluidic Scintillation Detectors 23 Internal coating by injection of low R.I polymer (e.g. Teflon AF n=1.3) Semester projects Dara Haftgoli Bakhtiari David McMeekin  Results not suitable for optics (thickness < 5µm, low uniformity) SU-8 (n=1.6) microchannels filled with methylene diiodide (n=1.8) + rhodamine 6G fluorescent dye Light spot Ø ~ 4 mm Filled chip Empty chip Photodetector pixel number Time-integrated intensity (a.u.) Proof of concept in collaboration with INFN Rome group: P. Bagiacchi, G. Gemignani, F. Safai Tehrani, S. Veneziano Photodiode array 5 µm ~ 200 nm SU-8 Teflon AF coating Post-bonding optical coating Pre-bonding optical coating e.g. Al coating after µchannel patterning No suitable method found for bonding

24. SU-8 MSD S : C ONCLUSIONS Novel fabrication approach based on wafer bonding and selective release developed Both single and double layer thin devices made Experimental validation with high-n fluorescent liquid To do: integrate optical coating (or use high-n scintillator) 25.06.2015 // Pietro Maoddi DT Seminar: Microfluidic Scintillation Detectors 24

25. O UTLINE IntroductionMain resultsConclusions 25.06.2015 // Pietro Maoddi DT Seminar: Microfluidic Scintillation Detectors 25 Conclusions Outlook Detectors based on SU-8 Detectors based on Silicon Radiation damage studies Scintillation detectors Project goals Intro to microfabrication

26. S ILICON A S A M ATERIAL F OR MSD S Radiation resistant Compatible with liquid scintillators Mechanically and thermally resistant Can be optically smooth (but it’s not transparent) Used in other detector technologies Offers new integration possibilities (photodetectors, electronics, …) Many reliable processing techniques available 25.06.2015 // Pietro Maoddi DT Seminar: Microfluidic Scintillation Detectors 26

27. D RY E TCHING AND S MOOTHING RF plasma reactor alternating SF 6 (etching) and C 4 F 8 (polymer coating) plasmas Vertical etching profile but resulting in «scalloping» Wet oxidation  SiO 2 has larger volume than Si  surface features loss SiO 2 removal with hydrofluoric acid  smooth silicon 25.06.2015 // Pietro Maoddi DT Seminar: Microfluidic Scintillation Detectors 27 2 µm 5 µm

28. S I MSD S : F ABRICATION B Y D RY E TCHING Two level DRIE (µchannels + inlets) Smoothing by thick wet oxidation Optical coating (Al deposition) Bonding and «packaging» 25.06.2015 // Pietro Maoddi DT Seminar: Microfluidic Scintillation Detectors 28 20 mm 15 mm EtchingSmoothing Al coating Pyrex w/ stripes Bonding Dicing & packaging (top view) 2 µm 5 µm

29. S I MSD S : F ABRICATION B Y W ET E TCHING Double side wet etching  2 µchannel layers Alignment to {100} silicon planes to obtain vertical sidewalls 25.06.2015 // Pietro Maoddi DT Seminar: Microfluidic Scintillation Detectors 29 Oxide mask etch Wet etching Aluminum coating Three wafer stack bonding Dry etching (fluidic via) … then dicing & packaging 90° 20 µm Internship L. Serex

30. S I MSD S : P HOTODETECTOR I NTEGRATION Si process compatibility  integration of photodiodes to µ-channels 25.06.2015 // Pietro Maoddi DT Seminar: Microfluidic Scintillation Detectors 30 Master projects L. Batooli E. Cuenot C. Wiese R. Moreddu (ongoing) Internship L. Serex Collaborators N. Wyrsch M. Moridi D. Bouvet Picture: C. Wiese Experimental validation by detecting light from micromirrors with PMTs Integration of a-Si:H photodiodes still ongoing planar integration: PD wire bond PCB

31. S I MSD S : C HARACTERIZATION W ITH S I PM S Silicon photomultipliers (SiPMs): new high gain photodetectors 25.06.2015 // Pietro Maoddi DT Seminar: Microfluidic Scintillation Detectors 31 Readout electronics development at INFN Rome S. Veneziano, F. Safai Tehrani et al. Custom electronics and DAQ system Master project M. Asiatici Sensitive to single photon (~50% PDE) Custom readout electronics and DAQ Single photon peaks

32. C HARACTERIZATION W ITH S I PM S 25.06.2015 // Pietro Maoddi DT Seminar: Microfluidic Scintillation Detectors 32 Measurements at CERN with: C. Joram E. Van Der Kraji Landau distrubutioni th photoelectron peakPedestal

33. C HARACTERIZATION W ITH S I PM S 25.06.2015 // Pietro Maoddi DT Seminar: Microfluidic Scintillation Detectors 33 (700×190 µm 2 microchannel cross section)

34. O UTLINE IntroductionMain resultsConclusions 25.06.2015 // Pietro Maoddi DT Seminar: Microfluidic Scintillation Detectors 34 Conclusions Outlook Detectors based on SU-8 Detectors based on Silicon Radiation damage studies Scintillation detectors Project goals Intro to microfabrication

35. I NCREASED R ADIATION R ESISTANCE 25.06.2015 // Pietro Maoddi DT Seminar: Microfluidic Scintillation Detectors 35 Device irradiation necessary to validate radiation resistance concept Heavy irradiation tests with protons  possible, but complex (safety, logistics, …) Lab surrogate: UV irradiation Indirect damage of the liquid scintillator in the microchannels by destruction of the fluors Master project D. Brouzet BaseFluor UV photons / Forster transfer Blue photons Ionising particles Liquid scintillator Damage by intense UV irradiation (photobleaching)

36. I NCREASED R ADIATION R ESISTANCE 25.06.2015 // Pietro Maoddi DT Seminar: Microfluidic Scintillation Detectors 36  Proof of concept of increased radiation resistance by scintillator recirculation Experiment 1 Continuous UV irradiation Periodic replacement of LS Experiment 2 Continuous UV irradiation Constant circulation of LS

37. S I MSD S : C ONCLUSIONS Several fabrication approaches proposed Both single and double layer devices made Experimental characterizations with SiPMs (and PMTs) Principle of scintillator recirculation validated 25.06.2015 // Pietro Maoddi DT Seminar: Microfluidic Scintillation Detectors 37

38. O UTLINE IntroductionMain resultsConclusions 25.06.2015 // Pietro Maoddi DT Seminar: Microfluidic Scintillation Detectors 38 Conclusions Outlook Detectors based on SU-8 Detectors based on Silicon Radiation damage studies Scintillation detectors Project goals Intro to microfabrication

39. C ONCLUSIONS Different technologies for the fabrication of MSDs explored Very thin and double layer devices Increased radiation resistance by scintillator recirculation New open development lines for the future Wafer-level photodetector integration Large devices operating by TIR  microchannels in low R.I. material 25.06.2015 // Pietro Maoddi DT Seminar: Microfluidic Scintillation Detectors 39 SU-8 Single layerDouble layer Silicon Dry etchedWet etched Double layer With mirrors

40. T HANK Y OU 25.06.2015 // Pietro Maoddi DT Seminar: Microfluidic Scintillation Detectors 40 Acknowledgements: C. Bault, M. Capeans, A. Catinaccio, B. Gorini, M. Haguenauer, S. Jiguet, C. Joram, G. Lehmann Miotto, A. Mapelli, F. Perez Gomez, P. Petagna, P. Renaud, F. Safai Tehrani, S.Veneziano CERN Contact: Alessandro Mapelli (PH-DT-EO) CERN-THESIS-2015-078 https://cds.cern.ch/record/2027620