1. SPIE Instr. for Astronomy, Marseille, John Vallerga, jvv@ssl.berkeley.edu Optically sensitive MCP image tube with a Medipix2 ASIC readout John Vallerga, Jason McPhate, Anton Tremsin and Oswald Siegmund Space Sciences Laboratory University of California, Berkeley

2. SPIE Instr. for Astronomy, Marseille, John Vallerga, jvv@ssl.berkeley.edu Motivation for new wavefront sensor detector kHz frame rates Larger format (> 256 x 256) –More accuators –More complex LGS images (parallax, etc) –Off null / open loop operation Very low (or zero!) readout noise High dynamic range and gated

3. SPIE Instr. for Astronomy, Marseille, John Vallerga, jvv@ssl.berkeley.edu Centroid in presence of noise: 8 x 8 Noiseless 35% QE 10 photons --- 100 photons 1000 photons 8 x 8 2.5 e - rms 90% QE 6 x 6 2.5 e - rms 90% QE 4 x 4 2.5 e - rms 90% QE

4. SPIE Instr. for Astronomy, Marseille, John Vallerga, jvv@ssl.berkeley.edu Photon Counting Q ADC V  v Events  Events Charge integrating Threshold Events Count (x,y,t)

5. SPIE Instr. for Astronomy, Marseille, John Vallerga, jvv@ssl.berkeley.edu Imaging, Photon Counting Detectors Photocathode converts photon to electron MCP(s) amplify electron by 10 4 to 10 8 Rear field accelerates electrons to anode Patterned anode measures charge centroid

6. SPIE Instr. for Astronomy, Marseille, John Vallerga, jvv@ssl.berkeley.edu GaAsP Photocathodes Hayashida et al. Beaune 2005 NIM

7. SPIE Instr. for Astronomy, Marseille, John Vallerga, jvv@ssl.berkeley.edu Wavefront Sensor Event Rates 5000 centroids Kilohertz feedback rates (atmospheric timescale) 1000 detected events per spot for sub-pixel centroiding  5000 x 1000 x 1000 = 5 Gigahertz counting rate! Requires integrating detector

8. SPIE Instr. for Astronomy, Marseille, John Vallerga, jvv@ssl.berkeley.edu Medipix/Timepix ASIC readout 256 x 256 array of 55 µm pixels Integrates counts, not charge 100 kHz/pxl Frame rate: 1 kHz Low noise (100e - ) = low gain operation (10 ke - ) GHz global count rate ~1 W watt/chip, abuttable Developed at CERN ~ 500 transistors/pixel

9. SPIE Instr. for Astronomy, Marseille, John Vallerga, jvv@ssl.berkeley.edu Readout Architecture 3328 bit Pixel Column 0 3328 bit Pixel Column 255 3328 bit Pixel Column 1 256 bit fast shift register 32 bit CMOS outputLVDS out Pixel values are digital (13 bit) Bits are shifted into fast shift register Choice of serial or 32 bit parallel output Maximum designed bandwidth is 100MHz Corresponds to 266µs frame readout

10. SPIE Instr. for Astronomy, Marseille, John Vallerga, jvv@ssl.berkeley.edu “Built-in” Electronic Shutter Enables/Disables counter Timing accuracy to 10 ns Uniform across Medipix Multiple cycles per frame No lifetime issues External input - can be phased to laser

11. SPIE Instr. for Astronomy, Marseille, John Vallerga, jvv@ssl.berkeley.edu Vacuum Tube Design

12. SPIE Instr. for Astronomy, Marseille, John Vallerga, jvv@ssl.berkeley.edu Vacuum Tube Design

13. SPIE Instr. for Astronomy, Marseille, John Vallerga, jvv@ssl.berkeley.edu Vacuum Tube Design

14. SPIE Instr. for Astronomy, Marseille, John Vallerga, jvv@ssl.berkeley.edu Vacuum Tube Design

15. SPIE Instr. for Astronomy, Marseille, John Vallerga, jvv@ssl.berkeley.edu Vacuum Tube Design

16. SPIE Instr. for Astronomy, Marseille, John Vallerga, jvv@ssl.berkeley.edu Difficulties over last two years Finding industrial partner to help fabricate vacuum tube and develop GaAs photocathode Burle merged with Photonis merged with DEP ITT - busy with military night vision Hamamatsu - too small a project Use in-house tube facilities with multi-alkali photocathode New brazing technique compatible with ceramic header materials (vacuum brazing) Slow leaks: tube failure Photocathode inconsistency

17. SPIE Instr. for Astronomy, Marseille, John Vallerga, jvv@ssl.berkeley.edu Second tube process Success! Qualification: poor optical QE

18. SPIE Instr. for Astronomy, Marseille, John Vallerga, jvv@ssl.berkeley.edu Quantum efficiency (factor of 4 too low)

19. SPIE Instr. for Astronomy, Marseille, John Vallerga, jvv@ssl.berkeley.edu First tests in darkroom

20. SPIE Instr. for Astronomy, Marseille, John Vallerga, jvv@ssl.berkeley.edu Linearity and Resolution Projected pinhole pattern (1 x 2 mm)

21. SPIE Instr. for Astronomy, Marseille, John Vallerga, jvv@ssl.berkeley.edu Flat field White light 66 MHz input rate No optic No “hex” pattern Black pixels are masked in Medipix2 Locally uniform 20 µs50 s

22. SPIE Instr. for Astronomy, Marseille, John Vallerga, jvv@ssl.berkeley.edu Fixed pattern noise SNR > 200

23. SPIE Instr. for Astronomy, Marseille, John Vallerga, jvv@ssl.berkeley.edu Old WWII watch movie

24. SPIE Instr. for Astronomy, Marseille, John Vallerga, jvv@ssl.berkeley.edu Old WWII watch movie 2 (radium dial) Bkgd.002 ct/pxl/s Room Temp

25. SPIE Instr. for Astronomy, Marseille, John Vallerga, jvv@ssl.berkeley.edu Gain and Event Threshold

26. SPIE Instr. for Astronomy, Marseille, John Vallerga, jvv@ssl.berkeley.edu Gain and Event Threshold

27. SPIE Instr. for Astronomy, Marseille, John Vallerga, jvv@ssl.berkeley.edu Electronic shutter and diode laser No shutter All images: room lights, 1kHz pulsed laser and 1 sec integ. Stretched by 400 1.5 µs shutter

28. SPIE Instr. for Astronomy, Marseille, John Vallerga, jvv@ssl.berkeley.edu Medipix3 - late 2008 0.13 µm CMOS technology Twice as many transistors in pixel Concurrent readout/integration Serial readout at 250MHz clock Up to 10,000 frames/sec

29. SPIE Instr. for Astronomy, Marseille, John Vallerga, jvv@ssl.berkeley.edu Summary and future work Demonstration of successful use of Medipix2 in sealed MCP tube More laboratory and telescope tests to be done Working with Photonis to incorporate our various readout technologies into their tubes –Delayline, cross strip, Medipix, Timepix, etc. –Standard industrial design –Better and more consistent photocathodes UV, neutron imaging tubes

30. SPIE Instr. for Astronomy, Marseille, John Vallerga, jvv@ssl.berkeley.edu Acknowledgements Univ. of Barcelona University of Cagliari CEA CERN University of Freiburg University of Glasgow Czech Academy of Sciences Mid-Sweden University University of Napoli NIKHEF University of Pisa University of Auvergne Medical Research Council Czech Technical University ESRF University of Erlangen-Nurnberg Thanks to the Medipix Collaboration: This work was funded by an AODP grant managed by NOAO and funded by NSF

31. SPIE Instr. for Astronomy, Marseille, John Vallerga, jvv@ssl.berkeley.edu City Movie - 1 Cycle Line Frequency

32. SPIE Instr. for Astronomy, Marseille, John Vallerga, jvv@ssl.berkeley.edu Extra slides

33. SPIE Instr. for Astronomy, Marseille, John Vallerga, jvv@ssl.berkeley.edu Timepix version of Medipix Amplitude rather than counts using “time over threshold’ technique If charge clouds are large, can determine centroid to sub- pixel accuracy Tradeoff is count rate as event collisions in frame destroy centroid information Single UV photon events

34. SPIE Instr. for Astronomy, Marseille, John Vallerga, jvv@ssl.berkeley.edu Original Medipix mode readout (UV) Zoom 256 x 256 (14 mm)

35. SPIE Instr. for Astronomy, Marseille, John Vallerga, jvv@ssl.berkeley.edu Factor of 8 improved resolution! 256 x 256 converted to 4096x4096 pixels (3.4µm pixels)

36. SPIE Instr. for Astronomy, Marseille, John Vallerga, jvv@ssl.berkeley.edu Factor of 8 improved resolution! 256 x 256 converted to 4096x4096 pixels (3.4µm pixels)

37. SPIE Instr. for Astronomy, Marseille, John Vallerga, jvv@ssl.berkeley.edu Centroid error vs. input fluence