Optical image tube with Medipix readout John Vallerga, Jason McPhate, Anton Tremsin and Oswald Siegmund Space Sciences Laboratory University of California, Berkeley

Motivation Original: Optical imaging detector for adaptive optics wavefront sensor Noiseless readout kHz frame rate GHz count rate High QE Long life (low MCP gain) Additionally: UV, neutron sensitive image tubes High spatial resolution (Timepix)

Imaging, Photon Counting Detectors Photocathode converts photon to electron MCP(s) amplify electron by 104 to 108 Rear field accelerates electrons to anode Patterned anode measures charge centroid

Vacuum Tube Design

Vacuum Tube Design

Vacuum Tube Design

Vacuum Tube Design

Thick Film Ceramic Header Internal mounting/GND surface for Medipix Route ~60 Medipix signals out of vacuum Multi-layered to better match Medipix pitch Maintain hermetic seal of tube to ≤10-9 Torr Provide land pads for external I/F connectors

Medipix on a Header

Vacuum Tube Design

MCP/Medipix Serial I/F Board

Original Medipix mode readout (UV) This is the very bad case of large events in Medipix mode. For normal medipix operation, we would try to make the spot size small. But in this case,we tried to make the spots large, leading to the poor resolution. But it is illustrative of what no centroiding can get you Zoom 256 x 256 (14 mm)

Timepix readout Remember the AFTP code 4-4 corresponds to 2^(4+(4-1)/6) or 2^4.5 Next slide is the center of the right image

TOT centroids result in factor of 8 improved resolution! Remember the AFTP code 4-4 corresponds to 2^(4+(4-1)/6) or 2^4.5 Next slide is the center of the right image 256 x 256 converted to 4096x4096 pixels (3.4µm pixels)

Second tube process Success! Qualification: poor optical QE

Quantum efficiency (factor of 4 too low)

First tests in darkroom Use existing vacuum box for HV connections, stable mount

Optical bench

First Light!

Linearity and Resolution Projected pinhole pattern (1 x 2 mm)

Flat field (red diode)

Old watch

Old watch (radium dial)

Old watch

Gain and Event Threshold

Gain and Event Threshold

Summary and future work Demonstration of successful use of Medipix2 in sealed MCP tube More laboratory and telescope tests to be done Looking for industrial partner 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