Gas pixel detector for x-ray observation

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1 Gas pixel detector for x-ray observation David Attié P. Colas, E. Delagnes, Y. Giomataris, M. Campbell, X. Llopart, M. Chefdeville, H. van der Graaf, J. Timmermans, J. Visschers NDIP08 Aix-les-Bains June 19 th,

2 Outline Introduction: motivations for a gas pixel detector 1. The TimePix readout chip Description Architecture and schematic 2. Micro Pattern Gaseous Detector TPC Description of Micromegas Micro-TPC 3. Application for x-ray observations Measurement of primary statistics in gas TPC based polarimeter Conclusion David.Attie@cea.fr NDIP08 Aix-les-Bains June 19 th,

Motivations for pixelized gaseous detector Gaseous detector advantages: 2D/3D imaging Low occupancy and low radiation length X 0 mean free path could be important Spatial resolution:

electrons direction & energy of tracks: low-energy e- for X-ray polarimetry 2 e- from double beta decay, nuclear recoils in WIMP or neutrino interactions for dark matter search ALICE

3 Motivations for pixelized gaseous detector Gaseous detector advantages: 2D/3D imaging Low occupancy and low radiation length X 0 mean free path could be important Spatial resolution: σ xy limited by the pad size (pitch/ 12) narrow charge distribution (RMS ~15 μm) High granularity: δ-ray recognition/suppression in TPC possibility to count primary clusters & electrons direction & energy of tracks: low-energy e- for X-ray polarimetry 2 e- from double beta decay, nuclear recoils in WIMP or neutrino interactions for dark matter search ALICE TPC simulations Digital TPC as a tracking detector with very high spatial resolution for astrophysics & high energy physics experiments David.Attie@cea.fr NDIP08 Aix-les-Bains June 19 th,

Description of the TimePix chip Chip (CMOS ASIC)

chip developed first for medical applications

25 μm on 6 layers Characteristics: surface: 1.

6 cm 2 matrix of 256 x 256 pixel size: 55 x 55 μm

discriminator register for configuration TimePix

e- 70 e - per pixel, C in ~ 15 ff 1 2 3 4 5 55 μm

4 Description of the TimePix chip Chip (CMOS ASIC) upgraded in the EUDET framework from the Medipix2 chip developed first for medical applications Pixel IBM technology 0.25 μm on 6 layers Characteristics: surface: 1.4 x 1.6 cm 2 matrix of 256 x 256 pixel size: 55 x 55 μm 2 For each pixel: preamp/shaper threshold discriminator register for configuration TimePix synchronization logic 14-bit counter Noise: ~ 650 e- 70 e - per pixel, C in ~ 15 ff μm μm Preamp/shaper Interface THL disc. Configuration latches Llopart et al., NIMA 581 (2007) μm 55 μm 4 Synchronization Logic 5 55 μm 55 μm Counter μm (pixel array) David.Attie@cea.fr NDIP08 Aix-les-Bains June 19 th,

5 TimePix Synchronization Logic Control Each pixel can be configured independently in 5 different modes Internal Shutter Medipix Timepix TOT Mode 100 MHz Internal clock up to 100 MHz DACs values Shutter Mask P1 P0 Mode Masked Masked Masked Masked Medipix Internal Clock Digital Signal 10 ns TOT Timepix-1hit Timepix Analog Signal detected not detected Summed charge David.Attie@cea.fr NDIP08 Aix-les-Bains June 19 th,

6 Detectors using TimePix chip Solid detector Gas detector x, y, F(x, y) 2D x, y, z(t), E(x,y) 3D Drift cathode grid X-ray source Ionizing particle Gas volume + - Semiconductor sensor Flip-chip bump bonding connections + - Amplification System (MPGD) + - Medipix2/TimePix chip TimePix chip David.Attie@cea.fr NDIP08 Aix-les-Bains June 19 th,

InGrid: Integrated Micromegas Grid Micromegas is a Micro Pattern Gaseous

pillars above the anode e- ~ 1 kv/cm Multiplication between anode and mesh Gain

chip by post-processing Resistive layer for protection of a-si:h IMT Neuchatel

7 InGrid: Integrated Micromegas Grid Micromegas is a Micro Pattern Gaseous Detector formed by a metallic micromesh (hole pitch 70 μm) sustained by 50 μm pillars above the anode e- ~ 1 kv/cm Multiplication between anode and mesh Gain up to 10 5 PCB pad ~ 80 kv/cm Integrate Micromegas detector directly on a CMOS chip by post-processing Resistive layer for protection of a-si:h IMT Neuchatel NIKHEF (MESA+, Univ. Twente) David.Attie@cea.fr NDIP08 Aix-les-Bains June 19 th,

8 InGrid: energy resolution Energy resolution depends on the grid geometry Grids can be very flat Escape peak K α Escape peak K β 13.6 % FWHM best energy resolution achieved: 13.6 % with 55 Fe source in P10 removal of K β 6.5 kev line: kev in P10 Hole pitch down to 14 μm with various diameters Gap: 50 μm; Hole picth: 32 μm,ø: 14 μm Different gaps (35-75 μm) Until now: grid is 1 μm of Al but can also be increased to 5 μm by electrolysis to be more robust Kβ-filtered spectrum with Cr foil 11.7% FWHM David.Attie@cea.fr NDIP08 Aix-les-Bains June 19 th,

Micro-TPC using TimePix/Micromegas Micro-TPC

mixture at atmospheric pressure TimePix chip

9 Micro-TPC using TimePix/Micromegas Micro-TPC with a 6 cm height field cage Windows for X-ray sources Size : 4 cm 5 cm 8 cm Cover Windows for β sources 6 cm Field cage Micromegas mesh Gas mixture at atmospheric pressure TimePix chip David.Attie@cea.fr NDIP08 Aix-les-Bains June 19 th,

10 Micro-TPC TimePix/Micromegas TimePix chip + SiProt 20 μm + Micromegas 55 Fe source Ar/Iso (95:5) Time mode z = 25 mm V mesh = -340 V t shutter = 283 μs David.Attie@cea.fr NDIP08 Aix-les-Bains June 19 th,

11 Measurements of primary statistics in gases Diffusion σ t should be big enough to separate electrons: e- per pixel ~ 1 Study of primary electrons and Fano factor F using RMS Spectrum of number of electrons for 2000 events: RMS 2 F b = + N 1 ε εn F: Fano factor b: single e- gain distribution rms (%) ε: detection efficiency N: number of primary e- TimePix+Ingrid+ 15 μm SiProt Argon + 5% Isobutane Sensitive to K α & K β FWHM = 9,5 % lines 5.9 kev line at ~ 226 e- David.Attie@cea.fr NDIP08 Aix-les-Bains June 19 th,

Polarimetry using photoelectric absorption Ideal polarimeter is a track

Photoelectron Differential photoelectron cross-section emitted from the

2r0 Z α hυ 2 φ 7 2 sin ( 1 β cosθ ) θ polar angle, φ azimutal angle θ cos

direction 2 φ 4 Auger electron N max φ θ N P = max N N min = B 2A + B N ( φ)

12 Polarimetry using photoelectric absorption Ideal polarimeter is a track imager with: resolution elements < mean free path of photoelectron X-ray E Photoelectron Differential photoelectron cross-section emitted from the atomic s-orbital in non relativist limit: dσ = dω dσ dω 4 cos mec 2r0 Z α hυ 2 φ 7 2 sin ( 1 β cosθ ) θ polar angle, φ azimutal angle θ cos Emission angles are modulated by the polarization P 2 maximum in the plane γ direction 2 φ 4 Auger electron N max φ θ N P = max N N min = B 2A + B N ( φ) = A + B cos 2 ( φ φ pol ) N min David.Attie@cea.fr NDIP08 Aix-les-Bains June 19 th,

13 Prototype TPC polarimeter using TimePix/Micromegas TimePix chip + SiProt 20 μm + Micromegas 55 Fe source Ne/Iso (90:10) TOT mode z < 5 mm V mesh = -450 V t shutter = 0.2 s David.Attie@cea.fr NDIP08 Aix-les-Bains June 19 th,

14 Prototype TPC polarimeter using TimePix/Micromegas Identify the cluster TimePix Determination chip of the polarization + SiProt 20 μm Barycentre + Micromegas Principal axis 55 Fe source Reconstructed absorption point Ne/Iso Reconstructed (90:10) photoemission direction with identification of the absorption point and the TOT mode removal of the final part of the track z < 5 mm φ photoemission angle Photoelection + e auger track in Neon+10 Isobutane φ Low V mesh = E -450 V k-edge of Neon e auger are isotropically emitted with a small t shutter fraction = 0.2 of sthe photon energy In low Z gas mixture tracks are longer so angular reconstruction is easier David.Attie@cea.fr NDIP08 Aix-les-Bains June 19 th,

15 Example of TPC for x-ray polarimeter Drift Electrode GEM like Readout Strips 130 μm pitch Black et al. NIMA 581, 2007, 755 Photoelectron Gas mixture: Neon/DME 50:50 at 0,6 atm e - Drift y x(t) y z x X-ray 2O mm Trigger Digitized Waveforms Differentiated Waveforms Polarized 6.4 kev photons Image Uniform response Modulation (P ~50 %) No false modulation An encouraging start Counts Unpolarized 5.9 kev photons 0 o 45 o 90 o Photoemission electron angle (degree) David.Attie@cea.fr NDIP08 Aix-les-Bains June 19 th,

16 Conclusions TimePix chip/micromegas + SiProt: demonstrator for the digital TPC useful tool for x-ray observations Ultimate resolution for a TPC thanks to the single electron sensibility Micro-TPC is an excellent tool to characterize photon absorption in gas mixtures - statistics of primary electrons and clusters - Fano factor (gain fluctuation) Identification of the photoelectron angle by imaging the photoelectron track is very promising for soft x-ray polarimetry ( 2 kev < Eγ < 50 kev) Still some technologic issues: Self triggering capability How to improve the readout of the chips (speed and larger surface)? - through Si connectivity: avoiding bonding wires - fast readout technology (~5 Gb/s) Sealed detector David.Attie@cea.fr NDIP08 Aix-les-Bains June 19 th,

17 The TimePix collaboration NIKHEF Saclay CEA/DAPNIA Univ. Twente/Mesa+ Harry van der Graaf Martin Fransen Jan Timmermans Jan Visschers Sipho van der Putten Arno Aarts David Attié Paul Colas Esther Ferrer-Ribas Arnaud Giganon Yannis Giomataris Marc Riallot Jurriaan Schmitz Victor Blanco Carballo Cora Salm Sander Smits FREIBURG CERN A. Bamberger K. Desch U. Renz M. Titov N. Vlasov A. Zwerger P. Wienemann Erik Heijne Xavier Llopart Medipix Consortium β - from 90 Sr source in He/Isobutane 80:20 Thank you for your attention David.Attie@cea.fr NDIP08 Aix-les-Bains June 19 th,

18 Backup slides NDIP08 Aix-les-Bains June 19 th,

19 Readout system for Medipix2/TimePix chip MUROSv2.1: Serial readout VHDCI cable of length <3m read 8 chips in mosaic tunable clock [30-200MHz] USB: Serial readout ~5 fps@20mhz Mosaic achitecture: David.Attie@cea.fr NDIP08 Aix-les-Bains June 19 th,

TimePix chip architecture 36 10 6 transistors on 6 layers (~550

5 μw) Reference clock per pixel up to 100 MHz Characteristics: analog

20 TimePix chip architecture transistors on 6 layers (~550 transistors/pixel 13.5 μw) Reference clock per pixel up to 100 MHz Characteristics: analog power: 440 mw digital power (Ref_Clk = 80 MHz): 450 mw serial readout (@ 100 MHz): 9.17 ms parallel readout (@ 100 MHz): 287 μs Pixel modes: masked counting mode (Medipix, Timepix-1h) Time-Over-Threshold charge info Common stop time info David.Attie@cea.fr NDIP08 Aix-les-Bains June 19 th,

21 TimePix chip schematic For each pixel Previous Pixel Ref_Clkb Clk_Read Mux 4 bits thr Adj Mask Mux Input Ctest Preamp THR Testbit Test Input Disc Polarity Shutter P0 P1 Timepix Synchronization Logic Shutter_in t Conf 8 bits configuration 14 bits Shift Register Ovf Control Ref_Clk Clk_Read Next Pixel Analogic part Digital part David.Attie@cea.fr NDIP08 Aix-les-Bains June 19 th,

First TimePix Quad First Timepix quad + 300 μm Si crystal 516 32 1 1.

Campbell, CERN 1 1 X (column number) 516 01 45.75 250.8 2953 500.

22 First TimePix Quad First Timepix quad μm Si crystal Medipix mode counting - 55 Fe source - t shutter =40 s 2. Time mode - 90 Sr source - t shutter = 237 μs Y 3. Time-Over-Threshold mode Am source - t shutter = 5 s Llopart & Campbell, CERN 1 1 X (column number) e David.Attie@cea.fr NDIP08 Aix-les-Bains June 19 th,

en même temps He CO 2 70/30 Fort potentiel pour la séparation de

23 TimePix & GEMs Freiburg (+Bonn) Ar CO 2 70/30 Cartes de 181x181 en mode Time & et en TOT Fournit les informations charge & temps en même temps He CO 2 70/30 Fort potentiel pour la séparation de traces David.Attie@cea.fr NDIP08 Aix-les-Bains June 19 th,

24 TimePix using Micromegas Timepix chip + Micromegas on frame: Moiré effects + pillars Timepix chip + SiProt + Ingrid: Uniform MESA+ Resistive layer for protection IMT Neuchatel counting mode David.Attie@cea.fr NDIP08 Aix-les-Bains June 19 th,

25 Micro-TPC TimePix/Micromegas TimePix chip + SiProt 20 μm + Micromegas 90 Sr source Ar He Time mode z ~ 40 mm V mesh = -340 V t shutter = 180 μs spark-proof! David.Attie@cea.fr NDIP08 Aix-les-Bains June 19 th,

26 Micro-TPC TimePix/Micromegas TimePix chip + SiProt 20 μm + Micromegas 90 Sr source Ar/Iso (95:5) Time mode z ~ 40 mm V mesh = -340 V t shutter = 180 μs David.Attie@cea.fr NDIP08 Aix-les-Bains June 19 th,

27 Gas mixture containing Neon NDIP08 Aix-les-Bains June 19 th,

28 Simulated quality factor Bellazzini et al., NIMA 572 (2007) 167 NDIP08 Aix-les-Bains June 19 th,

Detecting low energy recoils with Micromegas

Detecting low energy recoils with Micromegas Giomataris Ioannis, DAPNIA-Saclay Principle, performance Low threshold results Axion-WIMP search, polarimetry Large gaseous TPC Conclusions 1 40 kv/cm 1 kv/cm