1. Novel LAr TPC developments for neutrino and astrophysics
A. Badertscher, L. Kaufmann, L. Knecht, M. Laffranchi, A. Marchionni, G. Natterer, P. Otiougova, F. Resnati, A. Rubbia, T. Viant
ETH Zurich
CHIPP Workshop on Detector R&D, June 2008
A precision detector for
proton decay searches
neutrino oscillation measurements
dark matter searches
GLACIER: a concept for a scalable LAr detector up to ~ 100 kton
necessary R&D steps
LAr LEM-TPC: a novel scalable detector for cryogenic operation
0.1 x 0.1 m2 test setup
low-noise preamplifiers and DAQ developments
ArDM: a ton-scale LAr detector with a 1 x 1 m2 LEM readout
status of the inner detector
cryogenics and first cool down
first tests of the Light readout
Conclusions

2. LAr TPC as neutrino detector
A LAr TPC is the best detector for oscillation searches
measurements of θ13 and mass hierarchy, search for CP violation
provides high efficiency for e charged current interactions
adequate rejection against  NC and CC backgrounds
e/0 separation
fine longitudinal segmentation (few % X0)
fine transverse segmentation, finer than the typical spatial separation of the 2 ’s from 0 decay
e/,h separation
embedded in a magnetic field provides the possibility to measure both wrong sign muons and wrong sign electrons samples in a neutrino factory beam
F. Arneodo et al., “Performance of a liquid argon time projection chamber exposed to the WANF neutrino beam”, Phys. Rev. D 74 (2006)
Data collected in 1997
Search for QE events
86 “golden events with an identified proton of kinetic energy larger than 40 MeV and one muon matching NOMAD reconstruction

3. LAr TPC as proton decay detector
LAr MC: p → K+ ν
LAr TPC as proton decay detector
K.L. Giboni “A two kiloton liquid Argon detector for solar neutrinos and proton decay”, NIM 225 (1984) 579
ICARUS Coll. “ICARUS II. A second generation proton decay experiment and neutrino observatory at the Gran Sasso Laboratory”, Sept. 1993
LAr MC: p → e+ π0
10x efficiency than WC
only way to reach 1035 years
A. Bueno, M. Campanelli, A. Ferrari, A. Rubbia “Nucleon decay studies in a large liquid Argon detector”, AIP Conf. proc. 533 (2000) 12
A. Bueno et al. “Nucleon decay searches with large liquid Argon TPC detectors at shallow depths: atmospheric neutrinos and cosmogenic background”, JHEP04 (2007) 041

4. GLACIER Giant Liquid Argon Charge Imaging ExpeRiment
A scalable detector with a non-evacuable dewar and ionization charge detection with amplification
Passive perlite insulation
≈70 m
Drift length
h =20 m max
Electronic crates
Single module cryo-tank based on industrial LNG technology
A. Rubbia hep-ph/
Venice, Nov 2003
Giant Liquid Argon Charge Imaging ExpeRiment
possibly up to 100 kton

5. GLACIER concepts for a scalable design
LAr storage based on LNG tank technology
Certified LNG tank with standard aspect ratio
Smaller than largest existing tanks for methane, but underground
Vertical electron drift for full active volume
A new method of readout (Double-phase with LEM)
to allow for very long drift paths and cheaper electronics
to allow for low detection threshold (≈50 keV)
to avoid use of readout wires
A path towards pixelized readout for 3D images.
Cockroft-Walton (Greinacher) Voltage Multiplier to extend drift distance
High drift field of 1 kV/cm by increasing number of stages, w/o VHV feed-through
Very long drift path
Minimize channels by increasing active volume with longer drift path
Light readout on surface of tank
Possibly immersed superconducting solenoid for B-field
Scalable detector
Size
(kton)
Diameter
(m)
Height
100 70 20 10 30 1
LAGUNA: Large Apparatus for Grand Unification and Neutrino Astrophysics FP7 design study to address:
the excavation and preparation of the underground space
the design and construction of the tank
instrumentation
safety aspects including three detector technologies (Water, Scint, LAr) in various possible European sites

6. Steps towards GLACIER ➠ ➠ ➠ ➠ ➠
Small prototypes ➠ ton-scale detectors ➠ 1 kton ➠ ?
ArDM ton-scale
LEM readout on 1x1 m2 scale UHV, cryogenic system at ton scale, cryogenic pump for recirculation, PMT operation in cold, light reflector and collection, very high-voltage systems, feed-throughs, industrial readout electronics, safety (in Collab. with CERN)
B-field test ➠ ➠
direct proof of long drift path up to 5 m ➠
ArgonTube: long drift, ton-scale
LEM test
we are here
proof of principle double-phase LAr LEM-TPC on 0.1x0.1 m2 scale
Test beam 1 to 10 ton-scale
1 kton
Application of LAr LEM TPC to neutrino physics: particle identification ( MeV electrons), optimization of readout and electronics, possibility of neutrino beam exposure
full engineering demonstrator for larger detectors, acting as near detector for neutrino fluxes and cross-sections measurements, … ➠ ➠
10m
12m

7. Maximum sensitive volume
LAr LEM-TPC
10 cm drift
Maximum sensitive volume
10 x 10 x 30 cm3
Anode
1.5 kV/cm
28 kV/cm
LEM 2
1.2 kV/cm
28 kV/cm
LEM 1
1.0 kV/cm
LAr level
3 kV/cm
Grids

8. Proof of concept: LEM tests in pure Ar gas
P. Otiougova, PhD Diss. ETHZ 17704, April 2008
MPGDs generally function in gas mixtures: not compatible with double phase operation in LAr
Pure Ar
Photon feedback
Ions induced signal
10 s/div
@ 300 K, 1 bar
Emult ≈ 12 ÷ 13 kV/cm
Ar/CO2 90/10
Ions induced signal
Electrons induced signal
2 s/div
Ar/CO2 90/10
Faster signal achieved by drifting electrons to an anode and so enhancing the electron component signal
200 ns/div

9. Double stage LEM with Anode readout
Signal collection plane
Bottom LEM
16 strips 6 mm wide
10 x 10 cm2
Anode
Top LEM
Produced by standard Printed Circuit Board methods
Double-sided copper-clad (18 μm layer) FR4 plates
Precision holes by drilling
Gold deposition on Cu (<~ 1 μm layer) to avoid oxidization
Single LEM Thickness: 1.55 mm
Amplification hole diameter = 500 µm
Distance between centers of neighboring holes = 800 µm
10 x 10 cm2
16 strips 6 mm wide

10. Technical developments 1
HV feedthrough
Miniaturized kapton cables
LEMO 30 kV connector
HV connections to LEM planes (~8 kV)
Voltage divider for field shapers
HV connections to cathode and grids (up to ~30 kV)
All materials must be compatible with UHV and cryogenic application

11. Technical developments 2
kapton flex-prints
to ZIF connectors
32 channels/cable
To preamplifiers
vacuum tight, epoxy-sealed
feedthrough
Capacitor-based Levelmeters
ZIF connectors
scalable LEM design

12. Preamplifier development
10 €/ channel
2 channels on one hybrid
Custom-made front-end charge preamp + shaper
Inspired from C. Boiano et al.
IEEE Trans. Nucl. Sci. 52(2004)1931
4 different shaping constants
Measured values
ICARUS electronics
(τf=1.6 μs)
2 fC, Ci=350 pF
equivalent to
1 fC, Ci=200 pF

13. LEM-TPC typical signals and tracks
F. Resnati
PhD ETHZ in progress
Preamplifier box
LEM-TPC Setup
Pure GAr
Double-phase operation
with unpurified LAr
Signals digitized with one
8 channel, 14 bit, 100 MHz CAEN V1724 digitizer
Signal fits and track reconstruction in progress: Diploma Work by A. Behrens, ETHZ

14. Data Acquisition System development
R’EQUIP (130 kCHF) + ETHZ Scient. Equip. (130 kCHF) grants channel prototype
In collaboration with CAEN, developed A/D conversion and DAQ system
256 channels
12 bit 2.5 MS/s flash ADCs + programmable FPGA with trigger logic
Global trigger and channel-by-channel trigger,switch to ’low threshold’ when a ‘trigger alert’ is present
1 MB circular buffer, zero suppression capability, 80 MB/s chainable optical link to PC
SY2791
32 preamplifier channels
Tests in progress
A/D + DAQ
section
ETHZ preamps
CAEN SY2791 prototype
CAEN A2792 prototype

15. ArDM: search for Dark Matter
Funded by ETH + SNF
A. Rubbia, “ArDM: a Ton-scale liquid Argon experiment for direct detection of dark matter in the universe”, J. Phys. Conf. Ser. 39 (2006) 129
Two-stage LEM
Cockroft-Walton (Greinacher) chain: supplies the right voltages to the field shaper rings and the cathode up to 500 kV (E=1-4kV/cm)
800 mm
Assembly
@ CERN
1200 mm
Field shaping rings
and support pillars
Cathode grid
ETHZ, Zurich, Granada, CIEMAT, Soltan, Sheffield
14 PMTs

16. ArDM Inner Detector Field shaping rings and support pillars
Cockroft-Walton (Greinacher) chain
Cathode grid
Reflector foils
Shielding grid
PMTs

17. ArDM Cryogenics and LAr purification
vacuum insulation
LN2 cooling jacket
1400 l
‘dirty’ LAr cooling bath
pure LAr closed circuit
In collaboration with BIERI engineering
Winterthur, Switzerland
Recirculation and CuO purification cartridge
Bellow pump

18. ArDM Assembly
Sept – May 2008

19. Slow Control System Diploma Work by U. Degunda, ETHZ
LAr Bath Levelmeters

20. First ArDM cooldown temperature sensors along the detector axis ~ 20h
1.1bar
temperature sensors along the detector axis
Warming Up
Precooling of the external bath
0.4bar
refilling of the
external bath
9:00
6th May
04:00
13th May
16:00
8th May
23:00
10thMay
~ 20h

21. LAr Pump tests Measured LAr flux ~ 20 l/hr
Diploma Work by L. Epprecht, ETHZ
30 cm3
volume
In collaboration with BIERI engineering
Winterthur, Switzerland
 /  (# Measurement)
Measured LAr flux ~ 20 l/hr

22. First tests of Light Readout
photomultipliers
cathode
e-shield
movable
241Am
source
-30
+30
blue LED
fiber
V. Boccone, PhD U. of Zürich in progress
UHV magnetic
actuator
300K
P=1.1bar
2~2.9s
reflectors with wavelength shifter
88K
P=1.1bar
2~3.2s

23. The next steps …
LAr LEM-TPC tests with 32 channel readout and new CAEN DAQ system
implementation of LAr purification
simultaneous measurement of light and ionization charge
investigation of efficiency, stability and energy resolution of the LEM readout system
Address safety issues for ArDM: handling of one ton of LAr
installation of ODH detectors and in-situ rigeneration of the LAr purification cartridge
Filling of ArDM inner detector with LAr
operation of the LAr pump and purification cartridge
tests of light readout in LAr
test of the HV system
stability of cryogenic operation of the device: installation of a cryocooler
Design and construction of a 1 x 1 m2 LEM readout system for ArDM
Proceeding towards ‘physics’ operation of ArDM

24. Conclusions
The synergy between precise detectors for long neutrino baseline experiments and proton decay (and astrophysical neutrinos) apparatus is essential for a realistic proposal for a kton LAr detector
discovery physics, not only precision measurements
GLACIER is a concept for a scalable LAr detector up to 100 kton demanding concrete R&D
ArDM is a real 1-ton prototype of GLACIER
After a successful demonstration of ArDM, we want to proceed in a staged approach in order to reach a mature proposal for a 100 kton device, possibly around 2014
Full engineering design for a 1 kton prototype, together with continued R&D on readout devices/electronics
Construction of a 1 kton detector and exposure to a neutrino beam in a near location to demonstrate the physics performance