Thorsten Lux IFAE-BIST Concept of the DP TPC Baseline Choice: PMTs - - PowerPoint PPT Presentation

Thorsten Lux

IFAE-BIST

 Concept of the DP TPC  Baseline Choice: PMTs  311 Prototype  protoDune-DB/WA105  Alternative Light Readout R&D  Conclusions

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Ligh ght t sensors

• rs (provide

e t0) Cathode (~600 kV) Drift field 0.5 – 1 kV/cm Grid

LAr

Extraction field 2-3kV/cm

GAr

Anode (strips) 0V 1 cm 2 mm Collection field 5kV/cm e-

128 nm prompt light

6 m

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LEM/ THGEM

CIEMAT (Madrid) IFAE (Barcelona)

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• Model: R5912 from Hamamatsu
• Suitable for LAr
• Dynode stages: 10/14
• Gain: 107/109
• Dark counts: 4000 cps
• Diameter: 8”
• Cathode coverage: ~3%

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• PMTs not directly sensitive to 128 nm
• TPB used for WLS
• Thermal evaporation
• 2 options for coating:

TPB directly on PMT TPB on acrylic plate

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Setup at CERN used for characterization of both options Higher Qeff with direct coating but acrylic still fine and simpler => both tested in 311 prototype First samples coated at CERN facility.

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• Purpose: first tests of

some design features of WA105

• Construction ongoing
• Data taking starts in

September 2016

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5 PMTs:

• 3 directly coated
• 2 acrylic plate coatings

2 PMT bases tested:

6m 6m 6m 6m 6m 6m Some detector parameters

• 8.3x8.3x8.1 m3 total volume
• Total mass: 705 tons
• Active mass: 300 tons
• 7680 charge readout channels
• 36 PMTs (baseline: acrylic

plate coating)

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Characterization setup built at CIEMAT (Madrid/Spain)



Gain vs HV HV



Dark k current t frequency



Linearity (charge output vs light amplitude and frequency)



“Light memory” - Response to the same light pulse after a previous variable light excitation.



(With TPB) Spectral response at several points between 260nm and 400nm with LEDs or Xe lamp + monocromator and at 128nm with Ar and radioactive source.

Tests with all PMTs

Linearity Gain vs HV Room temperature LN2 temperature

Thin Films Depositi tion

• n system:
• Chamber: high 45 cm, : 30 cm.
• Mechanical pump
• Diffusion pump (High vacuum)
• Vacuum meters:
• Pirani
• Penning
• High intensity source
• In situ thickness measurement

(quartz crystal microbalance) TPB Depositi tion

• n parameter

ters:

• Technique: Thermal evaporation
• Base pressure: < 5·10-7 mbar
• Substrates: glass and Acrylic (5 x 5

cm).

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• based on same

technology as charge readout: TCA

• cost-effective =>

scalable for DUNE

• electr

tron

• nics

s outside side of cryosta stat

• developed by LAPP-

APC-OMEGA-IPNL

• provides trigger for

non-beam events

Cosmics are normally great for detector characterization but in for WA105 also a challenge ....

~10 kHz of cosmics  ~40 cosmics overlapping in 4 ms readout window  reconstruction of beam event a challenge dE/dx (MIP): ~2 MeV/cm  50.000 e/ions, 50.000  per cm  30 million e/ions and  per MIP in 600 cm

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• primary light has 2 components:

‐ fast component, singlet: 6 <  < 18 ns ‐ slow component, triplet: ~1.6 s

• 30 million photons for straight cosmic
• most of light for MIPs in fast component =>

perfect for triggering But we have light background …

5 mm, 3 kV/cm 2 mm, 5 kV/cm 1 mm LEM, 35 kV/cm

• electroluminescence (EL) in gas phase
• each e- will produce some hundreds s
• “constant” background

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Not a proble lem for DUNE ... Underg rgro round und operatio ion n reduces ces cosmics cs by 104 to 105! !

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Worse if N2 contamination!

(A. Sokolov, MPGD2015)

ppm level of N2:

• reduces primary light

peaks

• increases EL induced

background Simulation 311 prototype type will provi vide de importa tant t inpu put

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 Hamamatsu 3x3-50UM VUV3

Sample

 Setup

Serial N. N. Vop Vop (V) Dark Coun unts (kcps) Gain Temp. Coef efficien en t A0019 53.53 671 5.5E 6 56mV/C A0020 53.63 607

Gali S66 Amplifier (x6) 260 nm LED CAEN V965A QDC Tek DPO4104 Oscilloscope Tek AFG3252 Signal Generator Directly sensitive to 128 nm

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30 35 40 45 50 55 60 65 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

Counts Charge (pC) Counts of A20 T= 298K Vop = 53.63V Led 260nm Gate 500 ns 1kHz

Results

Serial N. N. Vop Vop (V) Dark Coun unts (cps) Gain A0019 53.53 750k 6.40E6 A0020 53.63 675k 6.84E6 Serial N. N. Vop Vop * (V) Dark Coun unts (cps) Gain A0019 44.0 20 6.40E6 A0020 44.1 20 6.84E6

*The Temperature coefficient provided by Hamamatsu won’t work at 77K. Vop is an estimation so we have the same gain we have at room temperature.

32 34 36 38 40 42 44 46 48 50 52 54 56 58 60 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

Counts Charge (pC) Counts of A20 T= 77K Vop = 44.1V Led 260nm Gate 500 ns 1kHz

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Idea: Replace transpartent wire cathode by large acrylic plate coated with conductive ITO + TPB coating Pros:

• no bubbles from

PMTs

• no light from space

between cathode and PMTs Cons:

• not cheap
• many plates of <=1

m2 => clueing them together and align them

• effect of ions on

TPB? ETH Zurich

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Tests ts in 1ton detec ector tor with larger er plates es and gluing g them m togeth ther will start t soon.

• Current baseline choice for WA105: PMTs + acrylic

plates

• Final decision after analysis of 311 prototype data
• Characterization of all 40 PMTs for WA105 at room

and LN2 temperature

• LRO electronics development well advance and

suitable also for DUNE

• Surface operation of WA105 adds challenges to LRO
• R&D on alternative LROs:
• SiPM directly sensitive to 128 nm
• SiPM coupled to WLS (to early to present results)
• ITO+TPB coated cathode
• Installation of PMTs in WA105: 10/2017

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