1. Beijing, August 18, 2004 P. Colas - Micromegas for HEP 1 Recent developments of Micromegas detectors for High Energy Physics Principle of operationPrinciple of operation AdvantagesAdvantages Experiments in progressExperiments in progress –Compass, CAST, NA48/Kabes Developments in progressDevelopments in progress –LC-TPC, neutron detection, NOSTOS neutrino experiment,… P. Colas, DAPNIA Saclay ICHEP 2004, Beijing

2. Beijing, August 18, 2004 P. Colas - Micromegas for HEP 2 Micromegas: Principle of operation Micromegas : a micromesh sustained by 50-100  m - high insulating pillars. The multiplication takes place between the anode and the mesh 200  m Small size -> Fast signals -> Short recovery time -> High rate capabilities

3. Beijing, August 18, 2004 P. Colas - Micromegas for HEP 3 Micromegas further advantages S1/S2 ~ E amplif / E drift S1 S2 Can choose the gap/HV to have the gain maximum w.r.t. the gap and pressure -> excellent energy resolution Ion feedback suppressed by E drift /E amplif

4. Beijing, August 18, 2004 P. Colas - Micromegas for HEP 4 COMPASS MIP detection for measuring the nucleon spin structure High particle flow : 105 kHz/cm 2 Sparks give less than 1 per mil dead time Space resolution < 70  m with 350  m strips The largest Micromegas so far (40x40 cm 2 ) In operation at CERN since 2002 efficiency>97%

5. Beijing, August 18, 2004 P. Colas - Micromegas for HEP 5 CAST Solar Axion detection : con- version of solar axions in a LHC magnet -> observe low-energy X- rays 2D with overlayed crossed strips In operation at CERN since 2003 CERN Axion Solar Telescope axions Transverse magnetic field (B) X ray detector L

6. Beijing, August 18, 2004 P. Colas - Micromegas for HEP 6 CAST Low threshold : 600 eV ! Low background (fluorescence) 6.5 keV  X y Cu escap e Fe escape Ar Low energy spectrum from Micromegas in CAST

7. Beijing, August 18, 2004 P. Colas - Micromegas for HEP 7 NA48/KABES CP violation In operation at CERN since summer 2003 Principle : TPC + micromegas KAon BEam Spectrometer T drift2 Micromegas Gap 50 μm Micromegas Gap 50 μm T drift1

8. Beijing, August 18, 2004 P. Colas - Micromegas for HEP 8 NA48/KABES Excellent time resolution Tagged K  track Space resolution from drift time measurement: 70 μm Time resolution: 0.6 ns Using TOT to correct time slewing Tagging with reconstructed K ±   ±  +  - (T 0 ) KABES - (T 0 ) DCH Spectrometer (ns) X Station 1 or 2 - X Station 3 (cm)

9. Beijing, August 18, 2004 P. Colas - Micromegas for HEP 9 Challenging requirements: High two-track separation in jets both in Z and in R  (O(8mm)) High background from photons and neutrons (600 n/BX) Excellent jet resolution (E-flow) Particle identification High granularity Low ion feedback Low H-content of the gas High granularity, small diffusion electrons ions chamber => Micropattern detectors Low material budget of the endplate (thin frame) Good dE/dx resolution TPC for the Linear Collider

10. Beijing, August 18, 2004 P. Colas - Micromegas for HEP 10 Detector 1024 pads Pad layout Field cage Readout Berkeley-Orsay-Saclay TPC

11. Beijing, August 18, 2004 P. Colas - Micromegas for HEP 11 LC-TPC FUTURE PROJECTS, R&D Cosmic ray data taking in May 2004. Accurate measurements of diffusion coefficients in progress. First results show that <100  m point resolution should be reached

12. Beijing, August 18, 2004 P. Colas - Micromegas for HEP 12 Spherical TPC for neutrino detection NOSTOS project : –Neutrino oscillation from Tritium –Supernova detection, burst time structure –Coherence in -A interactions to be tested at a reactor Uses the longitudinal diffusion in the gas to estimate the distance to center FUTURE PROJECTS, R&D Tritium source surrounded by a Micromegas

13. Beijing, August 18, 2004 P. Colas - Micromegas for HEP 13 Spherical TPC for neutrino detection Observe tritium e oscillation and measure  13 Measure the magnetic moment of the neutrino Measure the weak mixing angle at low energy Detect supernovae explosions FUTURE PROJECTS, R&D

14. Beijing, August 18, 2004 P. Colas - Micromegas for HEP 14 Micromegas readout by silicon pixels CERN-NIKHEF-Saclay-Twente MIPs have been seen in a combination micromeg.+Medipix InGrid (integrated grid) project pillars on silicon FUTURE PROJECTS, R&D 10 mm

15. Beijing, August 18, 2004 P. Colas - Micromegas for HEP 15 Neutron detection Use a converter to extract alphas FUTURE PROJECTS, R&D Numerous applications: neutron tomography, neutron detection in hostile environments

16. Beijing, August 18, 2004 P. Colas - Micromegas for HEP 16 New developments Bulk Micromegas obtained by lamination of a woven grid on an anode with a photo-imageable film Large area robust detectors can be made for neutrino detection or photodetection

17. Beijing, August 18, 2004 P. Colas - Micromegas for HEP 17 New developments Resistive layers (Ottawa- Saclay) Spreads the charge -> improves resolution with large pads (70  m obtained with 2mm pads with 3keV X-rays) Might protect from discharges New materials for meshes Two-stage micromegas

18. Beijing, August 18, 2004 P. Colas - Micromegas for HEP 18 CONCLUSION Existing Micromegas detectors perform well since over a year Micromegas offers exciting perspectives for HEparticle detection: –High granularity and suppressed ion back-flow for TPCs –Single electron detection, with a very fast electron signal –Record-breaking time resolution –Low matter budget