Transcript A noiseless 512 x 512 detector for AO with kHz frame rates

Optical image tube with Medipix readout
John Vallerga, Jason McPhate, Anton Tremsin and
Oswald Siegmund
Space Sciences Laboratory
University of California, Berkeley
Medipix2 Meeting, Jan. 2008, John Vallerga
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)
Medipix2 Meeting, Jan. 2008, John Vallerga
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
Medipix2 Meeting, Jan. 2008, John Vallerga
Vacuum Tube Design
Medipix2 Meeting, Jan. 2008, John Vallerga
Vacuum Tube Design
Medipix2 Meeting, Jan. 2008, John Vallerga
Vacuum Tube Design
Medipix2 Meeting, Jan. 2008, John Vallerga
Vacuum Tube Design
Medipix2 Meeting, Jan. 2008, John Vallerga
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
Medipix2 Meeting, Jan. 2008, John Vallerga
Medipix on a Header
Medipix2 Meeting, Jan. 2008, John Vallerga
Vacuum Tube Design
Medipix2 Meeting, Jan. 2008, John Vallerga
MCP/Medipix Serial I/F Board
Medipix2 Meeting, Jan. 2008, John Vallerga
Original Medipix mode readout (UV)
256 x 256
(14 mm)
Medipix2 Meeting, Jan. 2008, John Vallerga
Zoom
Timepix readout
Medipix2 Meeting, Jan. 2008, John Vallerga
TOT centroids result in factor of 8
improved resolution!
256 x 256 converted to 4096x4096 pixels (3.4µm pixels)
Medipix2 Meeting, Jan. 2008, John Vallerga
Second tube process
Success!
Qualification: poor optical QE
Medipix2 Meeting, Jan. 2008, John Vallerga
Quantum efficiency (factor of 4 too low)
AO Tube #2 - Quantum efficiency
4
3.5
QE (%)
3
2.5
2
1.5
1
0.5
0
350
400
450
500
550
600
W avelengt h (Å )
Medipix2 Meeting, Jan. 2008, John Vallerga
650
700
First tests in darkroom
Use existing vacuum box
for HV connections,
stable mount
Medipix2 Meeting, Jan. 2008, John Vallerga
Optical bench
Medipix2 Meeting, Jan. 2008, John Vallerga
First Light!
Medipix2 Meeting, Jan. 2008, John Vallerga
Linearity and Resolution
Residual to linear fit
8
6
Residual (microns)
Projected pinhole pattern
(1 x 2 mm)
4
2
0
-2
-4
-6
0
2
4
6
8
10
12
14
16
pinhole
Resolution v s. Position
1 .8
Resolution (FWHM, pixels)
1 .6
1 .4
1 .2
1
0 .8
0 .6
0 .4
0 .2
0
0
50
100
150
X Posit ion (pixels)
Medipix2 Meeting, Jan. 2008, John Vallerga
200
250
Flat field (red diode)
Medipix2 Meeting, Jan. 2008, John Vallerga
Old watch
Medipix2 Meeting, Jan. 2008, John Vallerga
Old watch
(radium dial)
Medipix2 Meeting, Jan. 2008, John Vallerga
Old watch
Medipix2 Meeting, Jan. 2008, John Vallerga
Gain and Event Threshold
AO-02 tube Gain vs. Voltage
Gain (kiloelectrons)
25
20
15
10
5
0
1600
1650
1700
1750
Voltage acros s M CPs
Medipix2 Meeting, Jan. 2008, John Vallerga
1800
1850
Gain and Event Threshold
Events/frame (10 microsec)
AO-02 tube Detected events/frame
450
400
350
300
250
200
150
100
50
0
1600
1650
1700
1750
Voltage acros s M CPs
Medipix2 Meeting, Jan. 2008, John Vallerga
1800
1850
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
Medipix2 Meeting, Jan. 2008, John Vallerga