SPIE Instr. for Astronomy, Marseille, John Vallerga, 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

SPIE Instr. for Astronomy, Marseille, John Vallerga, 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

SPIE Instr. for Astronomy, Marseille, John Vallerga, Centroid in presence of noise: 8 x 8 Noiseless 35% QE 10 photons photons 1000 photons 8 x e - rms 90% QE 6 x e - rms 90% QE 4 x e - rms 90% QE

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

SPIE Instr. for Astronomy, Marseille, John Vallerga, 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

SPIE Instr. for Astronomy, Marseille, John Vallerga, GaAsP Photocathodes Hayashida et al. Beaune 2005 NIM

SPIE Instr. for Astronomy, Marseille, John Vallerga, 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

SPIE Instr. for Astronomy, Marseille, John Vallerga, 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

SPIE Instr. for Astronomy, Marseille, John Vallerga, Readout Architecture 3328 bit Pixel Column bit Pixel Column bit Pixel Column 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

SPIE Instr. for Astronomy, Marseille, John Vallerga, “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

SPIE Instr. for Astronomy, Marseille, John Vallerga, Vacuum Tube Design

SPIE Instr. for Astronomy, Marseille, John Vallerga, Vacuum Tube Design

SPIE Instr. for Astronomy, Marseille, John Vallerga, Vacuum Tube Design

SPIE Instr. for Astronomy, Marseille, John Vallerga, Vacuum Tube Design

SPIE Instr. for Astronomy, Marseille, John Vallerga, Vacuum Tube Design

SPIE Instr. for Astronomy, Marseille, John Vallerga, 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

SPIE Instr. for Astronomy, Marseille, John Vallerga, Second tube process Success! Qualification: poor optical QE

SPIE Instr. for Astronomy, Marseille, John Vallerga, Quantum efficiency (factor of 4 too low)

SPIE Instr. for Astronomy, Marseille, John Vallerga, First tests in darkroom

SPIE Instr. for Astronomy, Marseille, John Vallerga, Linearity and Resolution Projected pinhole pattern (1 x 2 mm)

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

SPIE Instr. for Astronomy, Marseille, John Vallerga, Fixed pattern noise SNR > 200

SPIE Instr. for Astronomy, Marseille, John Vallerga, Old WWII watch movie

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

SPIE Instr. for Astronomy, Marseille, John Vallerga, Gain and Event Threshold

SPIE Instr. for Astronomy, Marseille, John Vallerga, Gain and Event Threshold

SPIE Instr. for Astronomy, Marseille, John Vallerga, Electronic shutter and diode laser No shutter All images: room lights, 1kHz pulsed laser and 1 sec integ. Stretched by µs shutter

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

SPIE Instr. for Astronomy, Marseille, John Vallerga, 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

SPIE Instr. for Astronomy, Marseille, John Vallerga, 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

SPIE Instr. for Astronomy, Marseille, John Vallerga, City Movie - 1 Cycle Line Frequency

SPIE Instr. for Astronomy, Marseille, John Vallerga, Extra slides

SPIE Instr. for Astronomy, Marseille, John Vallerga, 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

SPIE Instr. for Astronomy, Marseille, John Vallerga, Original Medipix mode readout (UV) Zoom 256 x 256 (14 mm)

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

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

SPIE Instr. for Astronomy, Marseille, John Vallerga, Centroid error vs. input fluence