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

2. 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/

3. 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

4. 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

5. 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)

6. 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 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 

7. 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 -> 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

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

9. 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

10. 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

11. 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

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

13. 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

14. 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 ) 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

15. 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

16. 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

17. 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.

18. backup

19. 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 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

20. 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
NND

21. 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