1. Matthew Moulson for the LAV Working Group NA62 Photon-Veto Working Group Meeting CERN, 17 December 2013 LAV construction & installation status

2. LAV construction status – M. Moulson (Frascati) – Photon Veto WG – CERN – 17 December 2013 LAV installation status at a glance 2 A10 transport 15-16 October Last transport for LAV stations in vacuum No damage – relatively uneventful Separate transport to be organized to return endcaps to Fantini Unable to transport all 4 endcaps on return trip 2 endcaps currently in use – need to replace with wooden endcaps A9 installation week of 04 November Waiting to install A10-A11 – new pieces of blue tube in stainless steel won’t be ready until March 2014 Cabling work Installation of cable supports for A6-A7-A8 Measurements for cable supports for A9-A10-A11 HV cabling: A4-A8 + recabling of A1-A3 with reflected cables Small modification needed for new cables Waiting for signal cables for A1-A11 with correct impedance to be manufactured

3. LAV construction status – M. Moulson (Frascati) – Photon Veto WG – CERN – 17 December 2013 A10 transport 3 No acceleration events No damage Temperature not as stable as in other transports Less efficiently wrapped? Thermal blanket setting too low?

4. LAV construction status – M. Moulson (Frascati) – Photon Veto WG – CERN – 17 December 2013 4 A12 construction status at a glance 263 blocks of Type 8 glued 300 HV dividers ready (143 with cables)

5. LAV construction status – M. Moulson (Frascati) – Photon Veto WG – CERN – 17 December 2013 5 Setup for wrapping & light-leak testing

6. LAV construction status – M. Moulson (Frascati) – Photon Veto WG – CERN – 17 December 2013 6 Notes on setup of electronics Lead-glass blocks: MD8090: dyMat T wrapping from A4 sample sheets ME1739: dyMat T wrapping from single sheet, separate end piece ME3301: dyMat T wrapping from single sheet, end flap Fast amplifier: CAEN N412: 8 channels, fixed 10× gain Low-threshold discriminator: LeCroy 620AL: 8 channels with −30 mV to −1 V common threshold Scaler: CAEN N1145: 4 channels + timer HV supply: CAEN N470: 4 channels, 3kV × 3mA, configurable polarity, front- panel programmable

7. LAV construction status – M. Moulson (Frascati) – Photon Veto WG – CERN – 17 December 2013 7 Noise problems in Ed. 57 10 mV × 50 ns −12.5 mV trig 10 mV × 2 μs −12.5 mV trig RF noise in Ed. 57: Frequency ~100 MHz Modulated at ~2.5 MHz Amplitude 11-19 mV Variable in time Significant complication for light-tightness mmt: Light leaks give small (< 10 mV) pulses Noise appears to be induced: Complete shielding e.g. of HV divider with Al foil reduces noise ~30% Not effective enough In practice, difficult to shield HV divider on block anyway

8. LAV construction status – M. Moulson (Frascati) – Photon Veto WG – CERN – 17 December 2013 8 Low-pass RC filter for noise Since we cannot eliminate noise by grounding or shielding, try to see if we can filter it Since the PMT is approximately a current source, use a parallel RC circuit as a simple low-pass filter V = IR − RC dV dt IRCV At low f, V = IR At high f, V < IR

9. LAV construction status – M. Moulson (Frascati) – Photon Veto WG – CERN – 17 December 2013 9 Effect of filter on signal and noise Test pulse, no filter: 50 ns × 50 mV Test pulse, filter: 50 ns × 20 mV trig −95 mV offset −4 mV trig −40.2 mV offset −4 mV Noise, no filter: 50 ns × 10 mV Test pulse: 100 mV 5 ns rise, 15 ns fall 20 ns duration trig −11.8 mV Noise, filter: 50 ns × 2 mV trig −2.48 mV Test pulse attenuation = 0.40 Noise attenuation = 0.21 S/B increased 1.92× Can trigger at 3 mV with filt (= 7.5 mV)

10. LAV construction status – M. Moulson (Frascati) – Photon Veto WG – CERN – 17 December 2013 10 Effect of amplification on noise Noise, before amp: 50 ns × 10 mV Noise, amp 10×: 50 ns × 100 mV Noise, amp 10×, filter: 50 ns × 20 mV trig −19 mV trig −236 mV trig −17 mV offset +10 mV After amplification: Noise attenuation = 0.21 → 0.11 Possibly from better measurement, though effect seems to be real

11. LAV construction status – M. Moulson (Frascati) – Photon Veto WG – CERN – 17 December 2013 11 Threshold setting for production Signal from tube, with filter: 50 ns × 10 mV 50 ns × 10 mV −2.5 mV trig Can easily trigger at 2.5 mV, with great sensitivity to light pulses Include 10x amplifier in signal chain LTD threshold set to 25 mV using test pulse (= 0.237 V on monitor pin)

12. LAV construction status – M. Moulson (Frascati) – Photon Veto WG – CERN – 17 December 2013 12 dyMat T wrapping: Initial observations Test stand offers good sensitivity to light leaks Well-wrapped block counts at 100-1000 Hz before debugging Counts skyrocket when flashlight shines on defects in wrapping With careful application of black tape, count rate can be brought to ~1 Hz and does not change when block wrapped in black cloth dyMat T wrapping is generally effective at blocking light Intact wrapping blocks light from 100 W incandescent bulb at 40 cm Sealing technique around reinforcement plates appears to be effective: Inner layer of black tape directly on reinforcement plates Outer layer of black tape to seal wrapping to inner layer Black outer coating is somewhat fragile Scratches or dimples that appear white to the eye will transmit light and must be repaired by application of black tape Edges and corners are particularly vulnerable and will need to be reinforced a priori with black tape

13. LAV construction status – M. Moulson (Frascati) – Photon Veto WG – CERN – 17 December 2013 13 Examples of scratches and scuffs Sharp object pressed into outer layer of wrapping, causing depression Scuff marks scrape off black outer layer Ding along edge of block

14. LAV construction status – M. Moulson (Frascati) – Photon Veto WG – CERN – 17 December 2013 14 Corners require special care Corners susceptible for two reasons: 1.Cracks originating from folds in wrapping 2.Damage from handling No significant difference between wrapping patterns End flap vs separate end piece) Operative rule: Any white spots in wrapping must be covered!

15. LAV construction status – M. Moulson (Frascati) – Photon Veto WG – CERN – 17 December 2013 15 Thoughts on wrapping procedure Blocks are heavy – need to minimize handling: Efficiency: Repeated movements take time and effort Protection of wrapping: More movements = more damage Ergonomics & safety! Reduce number of necessary movements by testing blocks in oven before wrapping: 1.Add new HV divider 2.Move to oven and test with original wrapping 3.Move to cleaning stand; clean and wrap block and test for leaks 4.Move to A12 and mount 1.Add new HV divider 2.Move to cleaning stand; clean and wrap 3.Move to oven and test 4.Move to cleaning stand and test for leaks 5.Move to A12 and mount Save 1 movement overall and 2 movements with new wrapping Of course, must confirm that results in oven same with old/new wrapping

16. LAV construction status – M. Moulson (Frascati) – Photon Veto WG – CERN – 17 December 2013 16 Comparison of old & new wrapping ME0710MD7445 Original HV (V)11431356 G × 10 −6 1.181.31 Y (pe/MeV)0.3340.302 New HV (V)11461354 G × 10 −6 1.2101.27 Y (pe/MeV)0.3080.299 Initial comparison of oven results from two blocks with original and new wrapping gives encouraging results Need to repeat test with higher statistics when wrapping material arrives

17. LAV construction status – M. Moulson (Frascati) – Photon Veto WG – CERN – 17 December 2013 17 Thoughts on rapid light-leak testing Need a standard test for light leaks that is: Reliable – passing test indicates that block is sufficiently light tight Reproducible – same test applied over and over gives same results Rapid – have to process many blocks In addition, desirable for test to supply some information on location of leaks Leaks can be very small and are best found with small flashlight Very helpful if standard test provides general area for light leaks Idea is to use a lightweight wooden box with LED distributed over internal surface to illuminate all sides simultaneously Can be used two ways: 1.Block suspended from cleaning stand – light box pulled up from below 2.Block stood tube-down on table – light box lowered over block LEDs on each internal face independently switchable to provide some ability to localize leaks Leaks can also be localized by lowering/raising box slowly over block and watching count rate

18. LAV construction status – M. Moulson (Frascati) – Photon Veto WG – CERN – 17 December 2013 18 Design notes for light box SMD 3528 LEDs (3.5 × 2.8 mm 2 ) Brilliant white (6000K) 300 LED = 1560 lumen (100 W incandescent = 1380 lumen) Power consumption at 12 VDC: 4.8 W/m rated 3.8 W/m measured Light source: 300 parallel wired LEDs in 5 m of transparent, waterproof (IP65), epoxy-based strip with adhesive backing Design considerations: Volume 24 × 24 × 60 cm 3 : completely covers block, including PMT Lightwight aspen plywood construction + 2 handles for easy handling Interior spray painted with opaque white enamel All wiring on exterior – nothing to snag or catch on inside LED strips are soft, rubbery epoxy

19. LAV construction status – M. Moulson (Frascati) – Photon Veto WG – CERN – 17 December 2013 19 Light box (“Discoteca”) Thanks to G. Petragnani for help with design & construction!

20. LAV construction status – M. Moulson (Frascati) – Photon Veto WG – CERN – 17 December 2013 20 Sides are independently switchable

21. LAV construction status – M. Moulson (Frascati) – Photon Veto WG – CERN – 17 December 2013 21 Summary Installation status: 1.A10 transported to CERN in October – A1-11 have all been delivered 2.A9 has been installed – A1-9 have all been installed 3.Cabling work is in progress Status of wrapping and light-leak tests for A12: 1.We know we can get a good, light-tight wrapping with dyMat T 2.We have developed a reliable technique for measuring light-leak rates 3.We still need to optimize and streamline the procedure for wrapping and testing, especially to avoid excessive handling 4.We have taken steps in this direction: We will investigate the feasibility of testing in oven before wrapping Preliminary indications are that this makes no difference We have developed a convenient standard illumination source (“Discoteca”)