LLNL AO talk - Aug. 17, 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
38
Embed
LLNL AO talk - Aug. 17, 2004 John Vallerga, Jason McPhate, Anton Tremsin and Oswald Siegmund Space Sciences Laboratory, University of California, Berkeley.
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
LLNL AO talk - Aug. 17, 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
LLNL AO talk - Aug. 17, 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”
LLNL AO talk - Aug. 17, 2004
Imaging, Photon Counting DetectorsCharge distribution on stripsCharge CloudMCP stackTube Window withphotocathodeγ
Photocathode converts photon to electron
MCP(s) amplify electron by 104 to 108
Rear field accelerates electrons to anode
Patterned anode measures charge centroid
LLNL AO talk - Aug. 17, 2004
Why would you want one?• No readout noise penalty
– Use as many pixels as you wish
• Continuous temporal sampling to ~ nsecs– Choose integration period(s) after the fact or on
the fly
• Other advantages– Large area, curved focal planes– Cosmic ray = 1 count
– LN2 not required
– Low dark current (0.16 attoamps cm-2)
LLNL AO talk - Aug. 17, 2004
Spatial Resolution
12 µm pore glass MCPs 7 µm pore glass MCPs
Cross Strip readout of Glass MCPs
LLNL AO talk - Aug. 17, 2004
MCP Detectors at SSL Berkeley COS FUV for Hubble (200 x 10 mm windowless)
25 mm Optical Tube
GALEX 68 mm NUV Tube (in orbit)
LLNL AO talk - Aug. 17, 2004
GaAs Photocathodes (GenIII)
• Developed for night vision tubes
• Slight cooling required (104 cps at room temp)
• Only fabricated in USA and Japan
LLNL AO talk - Aug. 17, 2004
GaN UV Photocathodes, 1000- 4000ÅGaN UV Photocathodes, 1000- 4000Å
0.1
1
10
100
150 200 250 300 350 400
NW-BH071#3
NW-BH071#2
NW-JG238#3
NW-JG238#2
Quantum Efficiency (%)
Wavelength (nm)
LLNL AO talk - Aug. 17, 2004
Advantages of multi-pixel sampling of Shack Hartman spots
Linear response off-nullInsensitive to input widthMore sensitive to readout noise