LAr detector R&D in Japan T.Maruyama (KEK) for LAr R&D groups

Concept of LAr TPC Ionization electron signal ~5x104e/cm MIP Liquid Ar 1 kV/cm Gas Argon 5kV/cm GEM readout Ionization electron signal ~5x104e/cm MIP 3D track reconstruction as a TPC drift velocity is ~mm/μs with ~kV/cm electric field LAr purity affects the attenuation of the drift electrons. No amplification inside LAr Diffusion of the drift electrons is about 3mm after 20m drift Double phase Ionization electrons Scintillation light Cherenkov light Charged particle Electric Field ドリフト速度: P10 50 mm/micros 純Ar: 1-5 mm/micros nm charged current event Closed dewar ne charged current event A. Bueno, et.al.,, hep-ph/0701101

Quest for the Origin of Matter Dominated Universe One of the Main Subject of the KEK Roadmap Discovery of the ne Appearance Neutrino Intensity Improvement Huge Detector R&D T2K (2009~) 　 Water Cherenkov v Liquid Ar TPC Establish Huge Detector Technology Construction of Discovery of Lepton CP Violation Proton Decay 2009/07/22 NuFact09 at Chicago 3 3

Image of ~100kt LAr and important R&D components Liquid phase Single stage GEM Readout Gas phase Test for long drift distance of ionized electrons using cylindrical cryostat Double phase detector readout using both liquid and gas Argon phases (with GEM/LEM) Electronic racks Charge readout plane GasAr E ≈ 3 kV/cm Extraction grid E-field LAr 20m E≈ 1 kV/cm Field shaping electrodes 80m 　Very high purity of LAr is needed. (t(ms)=300/ppb, e.g: 1/e at ~5cm of 10ppb with 1kV/cm) Drift velocity is slower with lower voltage, and it affects more attenuation in LAr. 　To provide better S/N, GAr is used, too. Cathode (- HV) High Voltage up to ~MV

Items to be Proven toward Huge Detector Technical Feasibility for Huge Detector Establish realistic maximum drift distance Tightness of LNG (Liquid Natural Gas) type tank. Purification from non-evacuated large volume. Possible drift high voltage, and effect of the bubble inside the tank Ionization signal distortion for long drift, dE/dx Use of passive insulation (thermal uniformity, stability, …) Scaling up of purification capacity Pre-cooling, flushing Physics Performance Define tolerable charge signal distortion , dE/dx resolution MC study needed (reconstruction,…) Proof with Beam is necessary Calorimetry (energy reconstruction, electric field dependence, energy scale, etc should be investigated with electron/muon beam) Charged pions (hadron interaction in medium, electric field dependence)

Items to be Proven toward Huge Detector (2) Signal-to-noise ratio is one of main issues in liquid argon TPC minimum ionizing track is releasing about 3 fC or about 17'000 electrons per 3 mm readout pitch, and dQ/dt decreases with drift length because of diffusion also attenuation due to impurities reduces further number of electrons problems for large detectors; need very good charge preamplifier (expensive) and noise must be kept low in charge preamplifier depends on capacitive load at input typically 100-200 pF it increases when wires are longer ---> longer wires ---> more noise also environmental noise (computers, DAQ, clocks etc...) is bad drift length is limited by attenuation and diffusion therefore our approach is to do new R&D on charge readout method on small scale setup prototype before trying to simply extrapolate existing technology to large detectors 

Strategy toward huge detector (Japan) 250L detector 100 cm 40 cm 　We prepare for several steps toward 100kt 10L (test of double phase readout) -> under testing 250L (test for e/g response of LAr TPC) and expose neutrino beam at J-PARC -> 2009 detector construction 30m3 (40 ton) max-drift -> under designing 40~1000ton detector 　These are inside the roadmap shown in CERN workshop (next page) 20 m 80 m 100ｋｔ detector

Roadmap shown in CERN workshop This talk mainly concentrates these !! by Alberto Marchionni on 2-Oct

Liquid Argon TPC R&D (KEK) 10L Liquid Argon teststand was set up at KEK. - Gas Argon is liquefied after purification. - Test chamber is evacuated and baked before lique- faction. 4 channel strip was used for read out. (anode plane) Field shapers and grid plane are pre- pared. Sensitive area is ~ 9x9x5cm3 LAr GAr LAr Open Bath Scroll Pump Turbo Pump Oxysorb (O2 filter) Hydrosorb (H2O filter) Test Chamber Anode Cathode Grid Field shaper Inside chamber 2009/07/22 NuFact09 at Chicago

First cosmic ray track at KEK (single phase) Trigger counters was set to measure cosmic ray track. We see the cosmic ray signal using the TPC (oscilloscope signal is shown below). Signal timing is as expected. First cosmic ray track at KEK Open Bath trigger1 trigger2 1 2 3 4 Anode Grid Trigger 1 (2cmx20cm X5mm(t)) Cathode Trigger 2 (2cmx20cmx5mm) 2009/07/22 NuFact09 at Chicago

Double Phase Detector Cathode: 9x9 cm copper plate Anode：9x2.2 cm copper plates 4 ch readout Field Shaper (SUS) 9x9 cm x0.8 mm 8 mm distance (5th is grid) Extraction Grid 100 mm SUS wire 5 mm pitch (1D) Anode Cathode GEM Field shapers Extraction Grid (Gas) Extraction Grid (Liquid) 11

Cosmic Track (double phase) 2009/07/22 12/28 NuFact09 at Chicago

Consideration on GEM gain Gain of GEM was reduced as a function of pressure/temperature (right-top; test varying with pressure) At present, we estimate the gain of 2.5 for this GEM (applying HV just before sparking) comparing single and double phase configurations. If we changed the HV configuration, it may be up to 4.0. There is also a good solution to increase sparking voltage. (see Alberto’s talk later) Gain of 50 was achieved by Russian group in pure Gas Argon. (double phase detector) Thinner GEM was used. Lower pressure ~ 0.8 bar These could not be a good solution for huge detector. Aimed S/N is ~10 for neutrino physics, so that this is not so bad at the first step. @ LAr temperature REPIC GEM w/o Rim 400 mm thickness 300 mmf hole 700 mm pitch Electrode: Copper

Status of 250L We borrow prototype cryostat of MEG (m -> e g) experiment (PSI). Cryostat was made for LXe (165K) test. Borrowed from ICEPP (U of Tokyo, Japan) Transported from PSI to KEK via CERN (Aug-19-2009) by ETHZ group. Aim to have e/g test-beam until next summer (2010-summer). Afterwards, neutrino exposure will be a next target. At present, evacuation test is under going (right bottom). ~0.01Pa was achieved. Also setup of cryogenic systems (on LN2 coil system and GM refrigerator) are under constructing !! ＫＥＫ (09/09/01) GM refrigerator (150W@90K)

200L Purging Test valve Demonstrate the performance of Air purging w/o evacuation 2 simple Oxygen monitors (0.1%-100%) TORAY Oxygen monitor 1ppm ~ 100% Connected to output line Bubbler Gas: O2 > 0.5% Liq.: O2 < 0.5% Safety valve (0.3bar) Simple Oxygen monitors (upto 0.1%) TORAY Oxygen monitor (up to ~1ppm) Bubbler of LAr

Result Gas flow: 200L/hour First 1.5 hour Monitor2 Gas flow: 200L/hour First 1.5 hour 20% -> 0.5% Different behavior afterwards Exp. function t ~ 1 hour We achieved ~3ppm (plateau) 10 hours Input Gas purity directly inject Gas to O2 monitor < 1 ppm Looks very nice at the first glance. (just purging achieved ~ppm level purity of gas) Tests will be done; Materials inside vessel Add ppm H2O monitor Monitor3 Monitor1 Input Gas purity t ~ 1 hour

Summary LAr TPC is a very important candidate for next generation neutrino physics and proton decay. There are many R&D items to achieve; Tank/Vessel (incl. Purity without evacuation) Possible high voltage for drift Ionization signal distortion. Scaling up of purification capacity Good electronics and number of channels Physics performance Several R&D items under going (also collaborated with European colleagues) are shown. One solution to achieve the good signal-to-noise ratio even with attenuation is to use 2-phase TPC. Some results are shown in this talk.

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Towards Huge LAr TPCs There are several proposals towards Huge LAr TPCs with different approaches: a modulable or a scalable detector for a total LAr mass of 50-100 kton evacuable or non-evacuable dewar -> evacuation guarantees the good purity. detect ionization charge in LAr without amplification or with amplification -> affects signal to noise ratio, etc. see later comments. Goal; Keep good physics performance with reasonable total cast for building. 2009/07/22 NuFact09 at Chicago

Purity Monitor Xenon flash lamp Optical fiber, feedthrough Hamamatsu Quartz window Optical fiber, feedthrough Ocean Optics good UV transmission Photo cathode Cathode copper plate Readout Anode signal only Signal yield is stable within few% over few hours 2009/9/5 T.Maruyama @ NND

2 Phase TPC with GEM (KEK) REPIC thick GEM 400 mm thickness 300 mmf hole 700 mm pitch GEM – Anode distance = 3 mm Nominal voltage Cathode -9kV, Ext Grid -2.5kV GEM DV=-1.8 kV and lower V = -300V Sensitive area: 9x9x4.5 cm Cathode: 9x9 cm copper plate Anode：9x2.2 cm copper plates 4 ch readout Extraction Grid 100 mm SUS wire 5 mm pitch (1D) 2009/07/22 NuFact09 at Chicago