1. The 1m2 Micromegas prototype for hadronic calorimetry
M. Chefdeville
LAPP, Annecy

2. Overview Motivations for a Digital Hadronic CALorimeter
R&D for a Micromegas DHCAL
Construction of a 1m2 prototype

3. Calorimetry at a linear e+/e- collider
Large angular coverage
Excellent jet energy resolution
3% at 100 GeV
Detector concepts
SiD and ILD based on Particle Flow Approach
Single particle shower imaging capability
Highly segmented and compact calorimeters
4th concept based on dual readout of scintillation and Cerenkov light
Calorimeter design
Small cell sizes (~1 cm2)
Thin sensitive layers (solid or gas)
HCAL choice of active media
Analog HCAL : Scintillators + SiPM
Digital HCAL : Gaseous Detectors RPC or GEM or MicroMegas
R&D within CALICE collaboration
Matching energy deposits
in calorimeter with tracks

4. Analog or digital information?
Hadronic energy resolution
Jet energy resolution (perfect PFA)
KEK for GLD
H MATSUNAGA
Pramana J. Phys., Vol 69, No 6, p
dec 2007
optimal for PFA :
“semi-digital” (2bits) readout with 1cm2 cells

5. Micromegas test chambers
Bulk Micromegas (woven mesh)
Robust and cheap
128 μm gap
78 μm hole pitch (325 LPI) & 30 µm diameter wires
6 x 16 – 12 x x 32 cm2 sensitive area (depending on readout)
Ar/iC4H10 95/5 mixture
Mesh voltage Vmesh ~ V
Gas gain G ~
Drift gap & field of 3 mm & 150 V/cm
High collection efficiency expected
Readout of 1 cm2 pads
Analog : GASSIPLEX + CENTAURE DAQ
Digital: HARDROC or DIRAC
+ Detector Interface board (DIF) + EUDET DAQ2 or CrossDAQ

6. Detector assembly Analog readout prototypes Digital readout prototypes
GASSIPLEX
Analog readout prototypes
GASSIPLEX card (6 chips) next
to the anode pad PCB
Digital readout prototypes
Embedded FE electronics
Chips below the anode pad PCB
Mesh laminated on the PCB
Use of a mask
Active Sensor Unit (ASU = PCB + ASIC)
Drift electrode
Grounded steel cover + kapton + Cu foil
Goal is to have thin layers (8 mm) and small dead areas
No screws but drift frame glued on PCB
Can not open chamber
HARDROC / DIRAC
mask
PCB
with ASICs

7. Characterisation with analog readout
ADC Counts
Few kBq 55Fe X-ray source
5.9 & 6.5 keV in 8.5:1 ratio
Placed above steel cover holes
Conversion rate ~ 20 Hz
Readout
Mesh signal + preamplifier + scope
Anode pad signal + GASSIPLEX/CENTAURE
Collection efficiency
Peak position and field ratio FR = EA/ED
Plateau for FR ~
Gain in units of ADC counts
Slope compatible with previous measurements
Pressure dependence assessed (-2 fC/mbar)
Energy resolution
19-20 % FWHM
Far from the statistical limit (11-12 %)
One pad response
Vmesh (V)
ADC Counts

8. Characterisation with analog readout
T9 line at PS-CERN (Nov. 2008)
Beam tests 2008
August: SPS-CERN H2 line (participation from Irfu/Saclay D. Attié, P. Colas and S. Turnbull)
November: PS-CERN T9 line
Set-up
Trigger: 3 scintillators in coincidence
3 MicroMegas 6x16 pads
1 MicroMegas 12x32 pads
Steel absorber option
Measure
Efficiency & multiplicity
Response uniformity
X-talk
Behaviour in showers
On–going data analysis
Pions of 200 GeV
Muons of 200 GeV
Pions with 1 steel block + absorbers
Pions of 7 GeV

9. Characterisation with analog readout
MPV ~ 45 fC
E Nb of Events
Results
Expected Landau distribution observed
Most Probable Value ~ 45 fC
Variations of 10 % r.m.s. over 4 chambers
Very good efficiency of ~ 95 %
Gain ~ 104 and threshold at 2.8 fC
Hit multiplicity < 1.1
Good noise conditions: pedestal spread <0.2 fC r.m.s. after alignment procedure
all triggers
E (ADC counts)
One pad response
Normalised MPV
Number of Pads
Efficiency
Chamber 0
97,05 ± 0,07%
Chamber 1
98,54 ± 0,05%
Chamber 2
92,99 ± 0,10%
Chamber 3
96,17 ± 0,07%

10. Characterisation with digital readout
PCB backside
DIRAC chip
DIRAC1 readout
64 channels ASIC (R. Gaglione)
Possibility to chain detectors
Threshold at 19 fC
First chamber with embedded electronics working!
PCB backside
Mask for bulk laying
~ events in total
PCB topside
8x8 pads with bulk
Beam Profile when moving the X-Y table
Test chamber on beam line

11. Characterisation with digital readout
HARDROC1 readout
64 channels ASIC, 3 layers of 8 x 32 cm2
Grouped by 4 on a PCB (ASU)
Data currently under study
Slightly in a rush for the beam test
Unstable behaviour of some chambers
Next beam tests, full characterization of chambers in dedicated test box
« Cooking » of the mesh
Collection
Gain margin
Response uniformity
Spark protections
Bulk

12. The 1 m2 Micromegas prototype
Long term goal: build a 1 m3 calorimeter
Stack of 1 m2 layers
Many parameters undefined yet
Absorber material-thickness
Sensitive layers: RPC-GEM-Micromegas
Coming year: build and test a 1 m2 Micromegas prototype
Tile detectors of smaller size
Easier fabrication
Reduce spark damages
Minimize dead areas
Prototype
9 216 channels
96 x 96 cm² active area
6 ASU of 32 x 48 cm2
3 DIF + interDIF boards
3 inter-DIF and DIF cards
6 ASU chained by 2

13. The 1 m2 Micromegas prototype
Reduce drift gap sensitivity to chamber over-pressure and cathode sag
Glue insulating walls and cathode
Reduce field distorsion between ASU
Mesh and pad extend 1 mm below the wall
2mm
Stainless steal 2mm
Mask for detector planeity
ASU (PCB+Bulk)
5mm
5 µm copper cathode
Insulating
wall
6 mm
Match thickness requirement of less than 8 mm

14. Stainless steal baseplate
Stainless steal cover
Frame
Gas tubes
ASU
DIF & interDIF
Vetronite mask
Stainless steal baseplate

15. Status of the 1 m2 prototype
DIF & DAQ almost ready
Active Sensor Units 32 x 48 cm2
PCB design and routing for 24 HARDROC2 ready
Also ASU with 24 DIRAC2 for the end of the year
Single ASU test box under conception
Largely inspired from T2K box
Still, mesh area ~ PCB area
Different positioning of the ASU
Mechanical prototype (dummy ASUs) under construction
Check e.g. gas tightness and homogeneity
2D field calculation

16. Conclusion MicroMegas R&D for DHCAL very active!
ASIC developments
Innovative prototypes, first digital readout with embedded electronics
Beam test results promising and partly understood so far, still a lot to analyze
Next beam test planned in 2009
1 m2 prototype should be ready for test by the end of the year
Next step: go for a 1 m3 calorimeter
Simulation efforts in parallel
Analog VS Digital
Semi-digital: how many thresholds and which heigths
Calorimeter design and material

17. Acknowledgements
Catherine Adloff Jan Blaha Sébastien Cap Alexandre Dalmaz Cyril Drancourt Ambroise Espagilière Renaud Gaglione Raphael Gallet Nicolas Geffroy Claude Girard Jean Jacquemier Yannis Karyotakis Fabrice Peltier Julie Prast Jean Tassan Guillaume Vouters