Progress in Micromegas & RetGEM Detectors

1. CBM China Meeting, Tsinghua University, November 2-4, 2009 Progress in Micromegas & RetGEM Detectors Limin Duan 中国科学院近代物理研究所 Institute of Modern Physics, CAS 2009-11-3

2. 1. Micromegas detectors This type of detectors was developed firstly at Saclay by Y. Giomatarisa and others. The detector consists of a two-stageparallel-plate avalanche chamber of small amplification gap combined with a conversion-driftspace. Fast signals are obtained during thecollection of the electron avalanche on the anode plane.

3. Configuration of Micromegas detector assembled detector Readout PCB anode Gas sealed Al container

4. Wire mesh structure • Wire mesh cathode (stainless steel woven wire mesh) • Active area：50×50mm2 • 600 LPI • Wire diameter：18m • Pitch: 41 m Wire mesh are produced in dimensions up to 3*40m; Less expensive than the Micromegas grid; Much sturdier and easier to handle; Higher resistance to discharge.

5. Front-end electronics and data acquisition system NIM & CAMAC system For the measurement of few parameters like energy spectra, effective gain, discharge probability etc.

6. Front-end electronics and data acquisition system FE: SFE16 DAQ: PXI－HPTDC Used in position resolution measurement

7. Measurement results Discharge probability and effective gain vs. voltage applied to the mesh. Energy spectrum of 5.9keV X-ray from 55Fe. FWHM=25%. Ar +10% CO2

8. Measurement results One dimension read out. Distance from Mesh to PCB is 290 m.The period of anode electrodes is 400m. Position resolution is <120m. Position ( 0.4mm per channel). narrow beam collimator The x ray pass through the narrow slits and then enter drift region. The edges of the slits parallel to the induction (read out) electrodes. The width of all slits is 100 m , and the period of the slits is 2.1mm. Multiplicity of fired electrodes.mean=1.5 ch Ar +10% CO2

9. Measurement results Multiplicity of fired electrodes. mean=2.5 ch Position ( 0.2mm per channel). The period of anode electrode is 200m. Mesh to PCB is 160 m. Position resolution is <100m Ar +10% CO2

10. Electrons Ions 2. RetGEM Detectors a robust, high-gain gaseous electronmultiplier,manufactured economically by standard printed-circuit drilling and etching technology. Its operation and structureresemble that of GEMs but with 5 to 20-fold expanded dimensions. These detectors can operate stably at gains close to 105 and if discharges appear at higher gains the protective layers restricttheir energies so that they do not damage either the detector orthe readout electronics. RetGEM: Resistive Electrode Thick Gas Electron Multiplier

11. Surface treatment original copper surface oxidation coated by CsI layers using vacuum evaporation coated by welding-proof ink

12. Configuration of RetGEM detectors Assembled double mode RETGEM. Gas sealed box. Schematic drawing of the experimental set up: (a) single mode, (b) double mode. Anode and RETGEM.

13. Measurement results Single mode. Counting rate plateau curve. Discharge probability and effective gain vs. voltage applied to the mesh. RETGEM consisting of a standard PCB of 1 mm thick with a hole diameter of 0.8mm, in pitch of 1.2mm, and 30 m copper layer, whose active area is 30mm*30mm.

14. Measurement results The energy resolution and discharge probability for a single mode with different ratio of gas mixtures. Energy spectrum of a single RETGEM in Ar+2%CO2. Single mode.

15. Measurement results Energy resolution and discharge probability vs. voltage while operating in double mode. Energy spectrum of a double RETGEM in Ar+5%CO2. Double mode.

16. Thanks！