SPIE Instrumentation for Astronomy AO - June22, 2004 John Vallerga, Jason McPhate, Anton Tremsin and Oswald Siegmund Space Sciences Laboratory, University of California, Berkeley Bettina Mikulec and Allan Clark University of Geneva A noiseless 512 x 512 detector for AO with kHz frame rates
19
Embed
SPIE Instrumentation for Astronomy AO - June22, 2004 John Vallerga, Jason McPhate, Anton Tremsin and Oswald Siegmund Space Sciences Laboratory, University.
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
SPIE Instrumentation for Astronomy AO - June22, 2004
John Vallerga, Jason McPhate, Anton Tremsin and Oswald Siegmund
Space Sciences Laboratory, University of California, Berkeley
Bettina Mikulec and Allan Clark
University of Geneva
A noiseless 512 x 512 detector for AO with kHz
frame rates
SPIE Instrumentation for Astronomy AO - June22, 2004
Future WFS Requirements*
• High (~80%) optical QE
• Lots of pixels - eventually 512x512
• Very low readout noise (< 3 e-)
• kHz frame rates
The last three are not simultaneously achievable with the current generation of CCDs
*Angel et al “A Road Map for the Development of Astronomical AO”
SPIE Instrumentation for Astronomy AO - June22, 2004
Imaging, Photon Counting Detectors
• Detects individual quanta of light via photoelectric effect
• Microchannel plate amplifies single electron to large charge cloud
• Signal per photon >> noise
• Readout gives X,Y of every event
• Time of every event also available
Charge distribution on stripsCharge CloudMCP stackTube Window withphotocathodeγ
SPIE Instrumentation for Astronomy AO - June22, 2004
Microchannel Plates
2 µm pores on 3 µm centers (Burle Industries)
SPIE Instrumentation for Astronomy AO - June22, 2004
MCP Detectors at Berkeley
85 mm
10 mm
400 pxl
14000 pxl
COS FUV for Hubble (2004,2005,???)
25 mm Optical Tube
68 mm
GALEX NUV Tube (in orbit)
SPIE Instrumentation for Astronomy AO - June22, 2004
GaAs Photocathodes (GenIII)
• Developed for night vision tubes
• Slight cooling required (104 cps at room temp)
• Only fabricated in USA and Japan
SPIE Instrumentation for Astronomy AO - June22, 2004
Advantages of multi-pixel sampling of Shack Hartman spots
Linear response off-nullInsensitive to input widthMore sensitive to readout noise
2 x 2 5 x 5
SPIE Instrumentation for Astronomy AO - June22, 2004
Wavefront Sensor Photon Rate
• Future large telescopes need > 5000 actuators
• Kilohertz feedback rates
• 1000 detected events per spot for sub-pixel centroiding
5000 x 1000 x 1000 5 Gigahertz counting rate!
• 104 time faster than existing photon counting imagers– Requires integrating readout
SPIE Instrumentation for Astronomy AO - June22, 2004
Our detector concept
An optical imaging tube using:
– GaAs photocathode
– Microchannel plate to amplify a single photoelectron by 104
– ASIC to count these events per pixel
SPIE Instrumentation for Astronomy AO - June22, 2004
Medipix2 ASIC Readout
Pixellated readout for x and gamma ray semiconductor sensors (Si, GaAs, CdTe etc)