Large-Area CdTe Photon-Counting Pixel Detectors

Transcription

1 Large-Area CdTe Photon-Counting Pixel Detectors Tilman Donath, Application Scientist , DIR2015, Ghent DECTRIS Ltd Baden Switzerland

2 Agenda 1. Introduction Hybrid Photon Counting Technology PILATUS3 readout ASIC CdTe module 2. Characterization & Applications 3. Summary 2

3 About DECTRIS Founded in 2006 as a spin off from the Paul Scherrer Institute 70 employees, located in Baden, Switzerland Products: 1D and 2D Hybrid Photon Counting X-ray detectors for scientific, industrial & medical applications Over 800 detector systems delivered to synchrotron facilities and OEM partners 3

4 HPC Products PILATUS3 R/S/X (172 µm pixel) EIGER R/X (75 µm pixel) MYTHEN2 R/X (50 µm strip) 4

5 Hybrid photon counting (HPC) technology Sensor pixel X-ray Readout pixel + Readout ASIC Direct conversion of X-rays in semiconductor sensor Optimal spatial resolution (PSF of ~1 pixel) Single-photon counting with energy threshold no readout noise & dark current high dynamic range (20 bit) fast readout 5

6 Integrating vs. Counting detector Photon energy X-rays on detector Charge integrating (flatpanel / CCD) Charge Charge-integrating detector time ADC photon weighting energy readout noise from ADC even at zero signal, dark current adding to signal, offset Photon-counting detector dynamic range limited by capacitance/well depth. Photon counting (PILATUS) Amplifier output Threshold exactly one count per photon above threshold energy, Comp. output Digital counter dark current fully suppressed, fast readout of digital counters, dynamic range = counter depth 20 bit (~1: ). 6

7 [counts] Noise-free detection 100 ms Dark images show - no readout noise - no dark current total number of counts: 0 1 hour 3 2 background radiation visible 1 0 Darkfields from PILATUS 100K detector 7

8 Cadmium Telluride Module CdTe sensor PILATUS3 CdTe module largest available CdTe sensors 35 x 42 mm 2, 1 mm thick two sensors per module with 3 pixel gap between sensors PILATUS3 readout ASIC featuring DECTRIS Instant Retrigger Technology Number of pixels: pixels Pixel size: mm 2 Active area: mm 2 8

9 Efficiency CdTe vs Silicon 9

10 Efficiency, measured Measurements at BAMline, BESSY II K escapes from Cd (>26.7 kev) Te (> 31.8 kev) - Beam energy kev - Low flux (max. 50 kcps) - E th = 50% photon energy Simulation with HORUS (JINST 6 P ) Scripts provided by D. Pennicard (DESY) 10

11 Variation of Ratio [%] Mean count stability at high flux 5x5 pixels Irradiated area Less than 1% variation over 14 hours BAMline at BESSYII Photon energy 33 kev Night constant high flux approx. 2.5 x 10 6 counts/s/pixel = approx. 8.5 x 10 7 counts/s/mm 2 11

12 Spatial Resolution Line pair test recorded with PILATUS3 CdTe detector, flat-fielded image. 0.5 lp/mm 2.9 lp/mm Homogeneous illumination from X- ray tube, tungsten target at 60 kvp and 3 mm aluminum filtration. Line pair test (Funk, type 53) 0.05 mm Pb Lp/mm: 0.25, 10, 6 12

13 Pinhole Measurement Pixel response scanned using a 10 µm diameter pinhole. geometrical and electrical pixel borders coincide 13

14 Large-area CdTe detectors PILATUS3 X CdTe 300K PILATUS3 X CdTe 300K-W PILATUS3 X CdTe 1M PILATUS3 X CdTe 2M Number of detector modules Sensitive area (width x height) [mm 2 ] 1 x 3 3 x 1 2 x 5 3 x x x x x Maximum frame rate [Hz]

15 Application Examples 15

16 CdTe detector - First Application Tests at ESRF PILATUS3 X CdTe 300K Single-photon counting (noise-free) Max. frame rate: 500 Hz Readout time: 0.95 ms Sharp PSF: ~1 pixel fwhm European Synchrotron Radiation Facility (ESRF), Grenoble, France ID15A High-Energy Scattering Beamline 16

17 X-ray Powder Diffraction Flatpanel PILATUS3 CdTe Sample: Powder-in-tube superconducting filament containing Nb3Sn powder in a tungsten tube (Ø50mm). Photon energy: 46.3 kev 17 Same static powder diffraction pattern recorded with both detectors positioned to cover the - same solid angle (same flux) per pixel, - same exposure time 100 ms. Acknowledgment: M. Di Michiel, G. Vaughan, R. Homs, T. Buslaps (ESRF)

18 Time-resolved X-ray Diffraction CT ESRF Beamline ID15A, X-ray beam energy 93keV, 130 projections x 100 translations ( diffraction patterns) per slice Study is enabled by fast, afterglow-free PILATUS3 X CdTe 300K detector. «Real Time Chemical Imaging of a Working Catalytic Membrane Reactor» A. Vamvakeros et al., Chem. Commun., 2015, Advance Article DOI: /C5CC03208C 18

19 Diffraction-CT Results Found formation of stable BaWO4 layer at CMR wall and uncontrolled mobility of W at high temperatures. «Real Time Chemical Imaging of a Working Catalytic Membrane Reactor» A. Vamvakeros et al., Chem. Commun., 2015, Advance Article DOI: /C5CC03208C 19

20 CT of Aluminum Foam Phantom PILATUS3 300K-W C = 0 HU, W = 1000 HU 10 mm Tube: 60 kvp, 10 ma; experimental CT scanner Scan parameters: 1000 projections in 8s (125 fps; 7ms exposure + 1ms readout) By courtesy of CT Imaging, Erlangen, Germany. 20

21 Dual Energy Decomposition 140 kvp Aluminum 80 kvp PMMA Decomposition using PMMA/Aluminum calibration and rational polynomial approach. PILATUS3 X CdTe test. Images courtesy of F.M. Epple, Technical University of Munich. 21

22 Summary Advantages of CdTe HPC detectors QE > 70% up to 80 kev sharp PSF (~1 pixel) high dynamic range high frame rates no afterglow Largest available CdTe X-ray detectors PILATUS3 Si and CdTe detectors highly successful for XRD at synchrotrons and lab sources 22

23 Outlook Industrial and Medical Imaging applications - are the next step Multiple thresholds per pixel - for spectral information in a single shot Industrial imaging with our silicon detectors at low-energies (4-36 kev) EIGER (75 µm pixel) and Mythen (50 µm strip) 23

24 Acknowledgment Valeria Radicci, Christiana Christodoulou, Michael Rissi, Tariel Sakhelashvili, Matthias Schneebeli, Peter Trueb, George Tudosie, Pietro Zambon, Clemens Schulze-Briese, Christian Broennimann The first PILATUS3 X CdTe 2M 24

25 Thank you for your attention! DECTRIS Ltd Baden Switzerland