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

Matthew Moulson for the LAV Working GroupNA62 Photon-Veto Working Group Meeting

CERN, 17 December 2013

LAV construction & installation status

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 trip2 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

LAV construction status – M. Moulson (Frascati) – Photon Veto WG – CERN – 17 December 2013

A10 transport

3

No acceleration eventsNo damage

Temperature not as stable as in other transports• Less efficiently wrapped?• Thermal blanket setting too low?

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 glued300 HV dividers ready (143 with cables)


Setup for wrapping & light-leak testing

block to test

amp LTDscaler

HV

oscilloscoppio

light source

cleaning stand


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


Noise problems in Ed. 5710 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


Low-pass RC filter for noiseSince 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 − RCdVdt

I R C V

At low f, V = IRAt high f, V < IR


Effect of filter on signal and noiseTest pulse, no filter: 50 ns × 50 mV

Test pulse, filter: 50 ns × 20 mV

trig −95 mVoffset −4 mV

trig −40.2 mVoffset −4 mV

Noise, no filter: 50 ns × 10 mV

Test pulse:100 mV5 ns rise, 15 ns fall20 ns duration trig −11.8 mV

Noise, filter: 50 ns × 2 mV

trig −2.48 mV

Test pulse attenuation = 0.40Noise attenuation = 0.21

S/B increased 1.92×Can trigger at 3 mV with filt (= 7.5 mV)


Effect of amplification on noiseNoise, 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 mVoffset +10 mV

After amplification:Noise attenuation = 0.21 → 0.11

Possibly from better measurement, though effect seems to be real


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)


dyMat T wrapping: Initial observationsTest 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


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


Corners require special care

Corners susceptible for two reasons:1. Cracks originating from folds in wrapping2. Damage from handling

No significant difference between wrapping patternsEnd flap vs separate end piece)

Operative rule:Any white spots in wrapping must be covered!


Thoughts on wrapping procedureBlocks 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 divider2. Move to oven and test

with original wrapping3. Move to cleaning stand;

clean and wrap block and test for leaks

4. Move to A12 and mount

1. Add new HV divider2. Move to cleaning stand;

clean and wrap3. Move to oven and test4. Move to cleaning stand

and test for leaks5. Move to A12 and mount

Save 1 movement overall and 2 movements with new wrappingOf course, must confirm that results in oven same with old/new wrapping


Comparison of old & new wrapping

ME0710 MD7445

Original

HV (V) 1143 1356

G × 10−6 1.18 1.31

Y (pe/MeV) 0.334 0.302

New

HV (V) 1146 1354

G × 10−6 1.210 1.27

Y (pe/MeV) 0.308 0.299

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


Thoughts on rapid light-leak testingNeed 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 below2. 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


Design notes for light box

SMD 3528 LEDs (3.5 × 2.8 mm2)

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 cm3: 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


Light box (“Discoteca”)

Thanks to G. Petragnani for help with design & construction!


Sides are independently switchable


SummaryInstallation 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:

4. We know we can get a good, light-tight wrapping with dyMat T

5. We have developed a reliable technique for measuring light-leak rates

6. We still need to optimize and streamline the procedure for wrapping and testing, especially to avoid excessive handling

7. 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”)

Documents

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