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CHIPP Astro-Particle Physics Workshop, Versoix, May 3 rd 2005 Photon Counting with a 512 x 512 Pixel...
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![Page 1: CHIPP Astro-Particle Physics Workshop, Versoix, May 3 rd 2005 Photon Counting with a 512 x 512 Pixel Array at 1 kHz Frame Rate - A New Wavefront Sensor.](https://reader034.fdocuments.us/reader034/viewer/2022051401/56649d4a5503460f94a2747f/html5/thumbnails/1.jpg)
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Photon CountingPhoton Countingwith a 512 x 512 Pixel Arraywith a 512 x 512 Pixel Array
at 1 kHz Frame Rateat 1 kHz Frame Rate--
A New Wavefront SensorA New Wavefront Sensorfor Adaptive Opticsfor Adaptive Optics
Bettina Mikulec, Allan ClarkUniversity of Geneva
John Vallerga, Jason McPhate, Anton Tremsin, Oswald Siegmund
Space Science Laboratory, University of California
![Page 2: CHIPP Astro-Particle Physics Workshop, Versoix, May 3 rd 2005 Photon Counting with a 512 x 512 Pixel Array at 1 kHz Frame Rate - A New Wavefront Sensor.](https://reader034.fdocuments.us/reader034/viewer/2022051401/56649d4a5503460f94a2747f/html5/thumbnails/2.jpg)
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Introduction into Adaptive Optics*Introduction into Adaptive Optics*
• Turbulence in the earth’s atmosphere makes stars twinkle
• More importantly, turbulence spreads out the star light making it a blob rather than a point– Temperature fluctuations in the
air cause changes in the index of refraction
– light rays are no longer parallel when they reach telescope and can therefore not anymore be focused to a point
Even the largest ground-based astronomical telescopes have no better resolution than an 8"
telescope!
Even the largest ground-based astronomical telescopes have no better resolution than an 8"
telescope!*adapted from AO lectures of Claire Max, Astro289C, UC Santa Cruz
blurPoint focus
Parallel light raysLight rays affected by turbulence
![Page 3: CHIPP Astro-Particle Physics Workshop, Versoix, May 3 rd 2005 Photon Counting with a 512 x 512 Pixel Array at 1 kHz Frame Rate - A New Wavefront Sensor.](https://reader034.fdocuments.us/reader034/viewer/2022051401/56649d4a5503460f94a2747f/html5/thumbnails/3.jpg)
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Adaptive OpticsAdaptive Optics
proposal for anew WFS -
Optical Medipix tube
![Page 4: CHIPP Astro-Particle Physics Workshop, Versoix, May 3 rd 2005 Photon Counting with a 512 x 512 Pixel Array at 1 kHz Frame Rate - A New Wavefront Sensor.](https://reader034.fdocuments.us/reader034/viewer/2022051401/56649d4a5503460f94a2747f/html5/thumbnails/4.jpg)
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Example for the enormous improvements using AO(Lick Observatory).
Adaptive OpticsAdaptive Optics
![Page 5: CHIPP Astro-Particle Physics Workshop, Versoix, May 3 rd 2005 Photon Counting with a 512 x 512 Pixel Array at 1 kHz Frame Rate - A New Wavefront Sensor.](https://reader034.fdocuments.us/reader034/viewer/2022051401/56649d4a5503460f94a2747f/html5/thumbnails/5.jpg)
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The new generation: adaptive optics on 8-10 m The new generation: adaptive optics on 8-10 m telescopestelescopes
Summit of Mauna Kea volcano in Hawaii:
Subaru
2 Kecks
Gemini North
And at other places: MMT, VLT, LBT, Gemini South
ESO VLT
Gemini South
![Page 6: CHIPP Astro-Particle Physics Workshop, Versoix, May 3 rd 2005 Photon Counting with a 512 x 512 Pixel Array at 1 kHz Frame Rate - A New Wavefront Sensor.](https://reader034.fdocuments.us/reader034/viewer/2022051401/56649d4a5503460f94a2747f/html5/thumbnails/6.jpg)
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30 m diameter:– California Extremely Large Telescope (CELT) -– Thirty Meter Telescope (TMT)
50 m diameter:– EURO50 on La Palma
100 m diameter:– European Southern Observatory’s “OverWhelmingly Large
Telescope” (OWL)
All propose AO systems with > 5000 actuators
Palomar Hale 5m telescope
Next Generation of Large Telescopes Next Generation of Large Telescopes (proposed)(proposed)
TMT
![Page 7: CHIPP Astro-Particle Physics Workshop, Versoix, May 3 rd 2005 Photon Counting with a 512 x 512 Pixel Array at 1 kHz Frame Rate - A New Wavefront Sensor.](https://reader034.fdocuments.us/reader034/viewer/2022051401/56649d4a5503460f94a2747f/html5/thumbnails/7.jpg)
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• Determine the distortions with the help of a natural or laser guide star and a lenslet array (one of the methods). Deviations of the spot positions from a perfect grid is a measure for the shape of the incoming wave-front.
Adaptive OpticsAdaptive Optics
Shack-Hartmann wavefront sensor
![Page 8: CHIPP Astro-Particle Physics Workshop, Versoix, May 3 rd 2005 Photon Counting with a 512 x 512 Pixel Array at 1 kHz Frame Rate - A New Wavefront Sensor.](https://reader034.fdocuments.us/reader034/viewer/2022051401/56649d4a5503460f94a2747f/html5/thumbnails/8.jpg)
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Wavefront Sensor RequirementsWavefront Sensor Requirements
• High QE for dimmer guide stars (~80% optical QE)• Gate the detector in 2-4 s range for operation with laser
guide starso Many pixels in the order of 512 x 512; future large
telescopes will have about 5000 actuators (controlled via 70 x 70 centroid measurements)
• 1000 photons per spot to get a 3% centroid rms error with respect to the stellar image size.
o 1 kHz frame rate (light integration, readout, calculations, send out 5000 signals and ready for new frame); faster than the timescale of the atmospheric turbulences
o Very low readout noise (< 3e-)
Large pixel array, high frame rate and no readout noise
not simultaneously achievable with CCDs!
![Page 9: CHIPP Astro-Particle Physics Workshop, Versoix, May 3 rd 2005 Photon Counting with a 512 x 512 Pixel Array at 1 kHz Frame Rate - A New Wavefront Sensor.](https://reader034.fdocuments.us/reader034/viewer/2022051401/56649d4a5503460f94a2747f/html5/thumbnails/9.jpg)
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2 µm pores on 3 µm centers (Burle Industries)
Proposal for a New Wavefront SensorProposal for a New Wavefront Sensor
High-QE GaAs photo-cathode Matched pair of microchannel plates (MCP) with 10 m
pore diameter in chevron configuration Medipix2 counting CMOS pixel chip Integrate photon events on pixel,
noiseless chip readout
![Page 10: CHIPP Astro-Particle Physics Workshop, Versoix, May 3 rd 2005 Photon Counting with a 512 x 512 Pixel Array at 1 kHz Frame Rate - A New Wavefront Sensor.](https://reader034.fdocuments.us/reader034/viewer/2022051401/56649d4a5503460f94a2747f/html5/thumbnails/10.jpg)
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The Medipix2 Photon Counting ChipThe Medipix2 Photon Counting Chip
0.25 m CMOS technology (33M transistors/chip)square pixel size of 55 µm 256 x 256 pixelssensitive to positive or negative input charge (free choice of different detector materials)pixel-by-pixel detector leakage current compensation window in energydiscriminators designed to be linear over a large range14-bit counter per pixel count rate: ~1 MHz/pixel (0.33 GHz/mm2)3-side buttableserial or parallel I/O (min. readout time of full matrix 266 µs)
![Page 11: CHIPP Astro-Particle Physics Workshop, Versoix, May 3 rd 2005 Photon Counting with a 512 x 512 Pixel Array at 1 kHz Frame Rate - A New Wavefront Sensor.](https://reader034.fdocuments.us/reader034/viewer/2022051401/56649d4a5503460f94a2747f/html5/thumbnails/11.jpg)
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Measurement SetupMeasurement Setup
• A Medipix2 photon counting chip • A matched pair of MCPs:
– Photonis MCPs with 33 mm diameter– 10 m hole diameters, L/D = 40/1– low resistivity (~22 MOhms per plate)– gain was varied between 20k and 200k (1430 - 1680 V)
• Vacuum tank pumped down to ~10-6 torr• Hermetic feed-throughs (50-pin connector for Medipix
signals)• A standard UV Hg pen-ray lamp with collimator (~10
counts/s -500M counts/s)
![Page 12: CHIPP Astro-Particle Physics Workshop, Versoix, May 3 rd 2005 Photon Counting with a 512 x 512 Pixel Array at 1 kHz Frame Rate - A New Wavefront Sensor.](https://reader034.fdocuments.us/reader034/viewer/2022051401/56649d4a5503460f94a2747f/html5/thumbnails/12.jpg)
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Feasibility TestsFeasibility Tests
single photonevents
gain 106, rear field 427 V gain 50k, rear field 980 V
It works!It works!
06 April 2004
• Event size function of MCP gain, rear field, MCP-Medipix distance and Medipix threshold
![Page 13: CHIPP Astro-Particle Physics Workshop, Versoix, May 3 rd 2005 Photon Counting with a 512 x 512 Pixel Array at 1 kHz Frame Rate - A New Wavefront Sensor.](https://reader034.fdocuments.us/reader034/viewer/2022051401/56649d4a5503460f94a2747f/html5/thumbnails/13.jpg)
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Flood FieldsFlood Fields
• Take image with collimated UV source at 50ke gain and 1600 V rear field (~5000 counts/pixel). Average single spot area: 2.4 pixels
– Fixed pattern noise from dead spots on the MCPs and MCP multifibres divides out.
take 2 independent uniform illuminations(flood fields at ~500Mcps)
Histogram of ratio consistent with countingstatistics (rms 0.02)
Ratio = flood1 / flood2.
![Page 14: CHIPP Astro-Particle Physics Workshop, Versoix, May 3 rd 2005 Photon Counting with a 512 x 512 Pixel Array at 1 kHz Frame Rate - A New Wavefront Sensor.](https://reader034.fdocuments.us/reader034/viewer/2022051401/56649d4a5503460f94a2747f/html5/thumbnails/14.jpg)
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ResolutionResolution
• The Air Force test pattern was used to demonstrate the imaging properties of the detector, in particular the resolution.
increaseshuttertime
100 s exposure; the spotscorrespond to individualphoton events.
1 s exposure. Group 3-2 visible (~9 lp/mmcorresponding to the Nyquistlimit of 55 m pixels)
![Page 15: CHIPP Astro-Particle Physics Workshop, Versoix, May 3 rd 2005 Photon Counting with a 512 x 512 Pixel Array at 1 kHz Frame Rate - A New Wavefront Sensor.](https://reader034.fdocuments.us/reader034/viewer/2022051401/56649d4a5503460f94a2747f/html5/thumbnails/15.jpg)
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Event CentroidingEvent Centroiding
• Centroiding individual photon events to achieve sub-pixel resolution:– Take many very low count rate images with larger spot area
to avoid overlapping spots. (~100-150 counts/frame; 1000 frames)
– Identify unique spots and reject overlapping events (counts 2), count spots, record their size and calculate the centroids.
Could be useful forlow rate imaging applications!
centroiding
Group 4-2 starts to be resolved(17.95 lp/mm; 55.7 m corresponding to ~28 m pixels).
![Page 16: CHIPP Astro-Particle Physics Workshop, Versoix, May 3 rd 2005 Photon Counting with a 512 x 512 Pixel Array at 1 kHz Frame Rate - A New Wavefront Sensor.](https://reader034.fdocuments.us/reader034/viewer/2022051401/56649d4a5503460f94a2747f/html5/thumbnails/16.jpg)
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UV Photon Counting MovieUV Photon Counting Movie
QuickTime™ and aYUV420 codec decompressor
are needed to see this picture.
Air Force resolution mask, 100 ms exposures
![Page 17: CHIPP Astro-Particle Physics Workshop, Versoix, May 3 rd 2005 Photon Counting with a 512 x 512 Pixel Array at 1 kHz Frame Rate - A New Wavefront Sensor.](https://reader034.fdocuments.us/reader034/viewer/2022051401/56649d4a5503460f94a2747f/html5/thumbnails/17.jpg)
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Spot Size vs. GainSpot Size vs. Gain
Pinhole grid mask (pitch 0.5 mm x 0.5 mm) to simulate Shack-Hartmann spots:
Rear field: 1600V, gap 500 m, threshold 3 ke-
Gain: 200 000 Gain: 20 000
![Page 18: CHIPP Astro-Particle Physics Workshop, Versoix, May 3 rd 2005 Photon Counting with a 512 x 512 Pixel Array at 1 kHz Frame Rate - A New Wavefront Sensor.](https://reader034.fdocuments.us/reader034/viewer/2022051401/56649d4a5503460f94a2747f/html5/thumbnails/18.jpg)
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Sub-Pixel Spatial LinearitySub-Pixel Spatial Linearity
LampPinhole
Detector
![Page 19: CHIPP Astro-Particle Physics Workshop, Versoix, May 3 rd 2005 Photon Counting with a 512 x 512 Pixel Array at 1 kHz Frame Rate - A New Wavefront Sensor.](https://reader034.fdocuments.us/reader034/viewer/2022051401/56649d4a5503460f94a2747f/html5/thumbnails/19.jpg)
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Average Movement of ~700 SpotsAverage Movement of ~700 Spots
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
0 5 10 15 20 25
Lamp Position (mm)
Centroid Position (µm)
Delta X
Delta Y
1 pixel
• Achieved a 2 m rms centroid position error with ~550 events/spot.
![Page 20: CHIPP Astro-Particle Physics Workshop, Versoix, May 3 rd 2005 Photon Counting with a 512 x 512 Pixel Array at 1 kHz Frame Rate - A New Wavefront Sensor.](https://reader034.fdocuments.us/reader034/viewer/2022051401/56649d4a5503460f94a2747f/html5/thumbnails/20.jpg)
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Electron DetectionElectron Detection
• First test results with beta sources
QE ~46% for Ni and ~63% for the Tl image;increasing efficiency with e- energies above ~50 keV consistent with literature.
63Ni, 67 keV max.~300 counts/pixel
Gain ~60k,rear field 1600 VMedipix threshold~38 ke-
204Tl, 764 keV max.~100 counts/pixel
![Page 21: CHIPP Astro-Particle Physics Workshop, Versoix, May 3 rd 2005 Photon Counting with a 512 x 512 Pixel Array at 1 kHz Frame Rate - A New Wavefront Sensor.](https://reader034.fdocuments.us/reader034/viewer/2022051401/56649d4a5503460f94a2747f/html5/thumbnails/21.jpg)
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ConclusionsConclusions
• New detector concept proven to work!• Performed systematic tests varying different
detector parameters• No fixed pattern noise yet detectable except
MCP imperfections• Resolution at Nyquist limit and below (for event-
by-event centroiding) demonstrated• Images presented with both UV and electron
sources detector has a great capacity to be used for various wavelengths and particles
![Page 22: CHIPP Astro-Particle Physics Workshop, Versoix, May 3 rd 2005 Photon Counting with a 512 x 512 Pixel Array at 1 kHz Frame Rate - A New Wavefront Sensor.](https://reader034.fdocuments.us/reader034/viewer/2022051401/56649d4a5503460f94a2747f/html5/thumbnails/22.jpg)
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Ongoing workOngoing work
• Test new ceramic chip carrier (= tube backend); thermal cycling tests with Medipix2 chip mounted
• Tube fabrication at SSL Berkeley and at commercial firm with GaAs photo-cathode
• Test prototype parallel readout board designed in collaboration with ESRF– reduce output bandwidth by using an FPGA; goal: 1 kHz
continuous frame rate with 2x2 chip arrangement
• Test prototype tubes at the AO laboratory at CFAO, U.C. Santa Cruz
• Final test at a telescopeSSL received 3-year NOAO grant, 1.5 more years to go…, some funding for Univ. Geneva from Fonds National and F. Schmidheiny
• Consider other applications for such a detector
![Page 23: CHIPP Astro-Particle Physics Workshop, Versoix, May 3 rd 2005 Photon Counting with a 512 x 512 Pixel Array at 1 kHz Frame Rate - A New Wavefront Sensor.](https://reader034.fdocuments.us/reader034/viewer/2022051401/56649d4a5503460f94a2747f/html5/thumbnails/23.jpg)
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Parallel Readout BoardParallel Readout Board
![Page 24: CHIPP Astro-Particle Physics Workshop, Versoix, May 3 rd 2005 Photon Counting with a 512 x 512 Pixel Array at 1 kHz Frame Rate - A New Wavefront Sensor.](https://reader034.fdocuments.us/reader034/viewer/2022051401/56649d4a5503460f94a2747f/html5/thumbnails/24.jpg)
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Tube DesignTube Design
![Page 25: CHIPP Astro-Particle Physics Workshop, Versoix, May 3 rd 2005 Photon Counting with a 512 x 512 Pixel Array at 1 kHz Frame Rate - A New Wavefront Sensor.](https://reader034.fdocuments.us/reader034/viewer/2022051401/56649d4a5503460f94a2747f/html5/thumbnails/25.jpg)
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Tube DesignTube Design
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Backup Slides!
![Page 27: CHIPP Astro-Particle Physics Workshop, Versoix, May 3 rd 2005 Photon Counting with a 512 x 512 Pixel Array at 1 kHz Frame Rate - A New Wavefront Sensor.](https://reader034.fdocuments.us/reader034/viewer/2022051401/56649d4a5503460f94a2747f/html5/thumbnails/27.jpg)
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The Setup at SSL - PhotosThe Setup at SSL - Photos
![Page 28: CHIPP Astro-Particle Physics Workshop, Versoix, May 3 rd 2005 Photon Counting with a 512 x 512 Pixel Array at 1 kHz Frame Rate - A New Wavefront Sensor.](https://reader034.fdocuments.us/reader034/viewer/2022051401/56649d4a5503460f94a2747f/html5/thumbnails/28.jpg)
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Spot SizeSpot Size
Spot Area vs Rear Field
0
5
10
15
20
25
30
35
40
0 200 400 600 800 1000 1200 1400 1600
Rear Field (V)
Spot Area (pixel)
Gain 25k
Gain 50k
Gain 100k
Gain 200k
Gain 400k
Rear Field = 1600V
0
2
4
6
8
10
12
14
16
18
20
0 5 10 15 20 25 30 35 40
Lower Threshold (ke-)
Mean Spot Area (pixel)
G=20k, Area
G=50k, Area
G=100k, Area
G=200k, Area
Spot area versus rear field.Spot area versus Medipix2 low threshold.
![Page 29: CHIPP Astro-Particle Physics Workshop, Versoix, May 3 rd 2005 Photon Counting with a 512 x 512 Pixel Array at 1 kHz Frame Rate - A New Wavefront Sensor.](https://reader034.fdocuments.us/reader034/viewer/2022051401/56649d4a5503460f94a2747f/html5/thumbnails/29.jpg)
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Soft X-Ray PhotocathodesSoft X-Ray Photocathodes
0
20
40
60
80
100
0.1 1
CsBr
KI
Energy (keV)
![Page 30: CHIPP Astro-Particle Physics Workshop, Versoix, May 3 rd 2005 Photon Counting with a 512 x 512 Pixel Array at 1 kHz Frame Rate - A New Wavefront Sensor.](https://reader034.fdocuments.us/reader034/viewer/2022051401/56649d4a5503460f94a2747f/html5/thumbnails/30.jpg)
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EUV and FUVEUV and FUV
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0 500 1000 1500 2000
CsI 1985 vs 1999
CsI 1985 30°CsI 1985 20°CsI #3 2/99 20°CsI #3 2/99 30°CsI #2 1/99 20°CsI #2 1/99 30°
Wavelength (Å)
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GaN UV Photocathodes, 1000- GaN UV Photocathodes, 1000- 4000Å4000Å
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)
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hBright st
ars + 0
= 1% sk
y
coverage
Isoplanatic Angle (Isoplanatic Angle (00) & Sky Coverage) & Sky Coverage
TelescopePrimarymirror
![Page 33: CHIPP Astro-Particle Physics Workshop, Versoix, May 3 rd 2005 Photon Counting with a 512 x 512 Pixel Array at 1 kHz Frame Rate - A New Wavefront Sensor.](https://reader034.fdocuments.us/reader034/viewer/2022051401/56649d4a5503460f94a2747f/html5/thumbnails/33.jpg)
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Laser Guide StarsLaser Guide Stars
Can achieve>70% sky
coverage withlaser guide staradaptive optics!
![Page 34: CHIPP Astro-Particle Physics Workshop, Versoix, May 3 rd 2005 Photon Counting with a 512 x 512 Pixel Array at 1 kHz Frame Rate - A New Wavefront Sensor.](https://reader034.fdocuments.us/reader034/viewer/2022051401/56649d4a5503460f94a2747f/html5/thumbnails/34.jpg)
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Laser Guide Star ParallaxLaser Guide Star Parallax
d
L
589.2 nm
• “Star” more of a streak• Shape changes over pupil• Can use pulsed laser to limit
spatial extent• Requires gated detector
![Page 35: CHIPP Astro-Particle Physics Workshop, Versoix, May 3 rd 2005 Photon Counting with a 512 x 512 Pixel Array at 1 kHz Frame Rate - A New Wavefront Sensor.](https://reader034.fdocuments.us/reader034/viewer/2022051401/56649d4a5503460f94a2747f/html5/thumbnails/35.jpg)
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005
35Bettina Mikulec
Advantages of Multi-Pixel Sampling of Shack Advantages of Multi-Pixel Sampling of Shack Hartmann SpotsHartmann Spots
Linear response off-nullInsensitive to input widthMore sensitive to readout noise
2 x 22 x 2 5 x 55 x 5
![Page 36: CHIPP Astro-Particle Physics Workshop, Versoix, May 3 rd 2005 Photon Counting with a 512 x 512 Pixel Array at 1 kHz Frame Rate - A New Wavefront Sensor.](https://reader034.fdocuments.us/reader034/viewer/2022051401/56649d4a5503460f94a2747f/html5/thumbnails/36.jpg)
CH
IPP
Astro
-Particle
Ph
ysics Work
shop
, Verso
ix, May
3rd 2
005
36Bettina Mikulec
Deformable MirrorsDeformable Mirrors
• Range from 13 to > 900 actuators (degrees of freedom)
Xinetics~ 50 mm
~ 300mm
![Page 37: CHIPP Astro-Particle Physics Workshop, Versoix, May 3 rd 2005 Photon Counting with a 512 x 512 Pixel Array at 1 kHz Frame Rate - A New Wavefront Sensor.](https://reader034.fdocuments.us/reader034/viewer/2022051401/56649d4a5503460f94a2747f/html5/thumbnails/37.jpg)
CH
IPP
Astro
-Particle
Ph
ysics Work
shop
, Verso
ix, May
3rd 2
005
37Bettina Mikulec
Position Error (550 Events/Spot) Position Error (550 Events/Spot)
0
5
10
15
20
25
30
35
40
45
50
-20 -15 -10 -5 0 5 10 15 20
Centroid difference (microns)
Number of centroids
rms = 2.0 µm
![Page 38: CHIPP Astro-Particle Physics Workshop, Versoix, May 3 rd 2005 Photon Counting with a 512 x 512 Pixel Array at 1 kHz Frame Rate - A New Wavefront Sensor.](https://reader034.fdocuments.us/reader034/viewer/2022051401/56649d4a5503460f94a2747f/html5/thumbnails/38.jpg)
CH
IPP
Astro
-Particle
Ph
ysics Work
shop
, Verso
ix, May
3rd 2
005
38Bettina Mikulec
Medipix readout of semiconductor Medipix readout of semiconductor arraysarrays
![Page 39: CHIPP Astro-Particle Physics Workshop, Versoix, May 3 rd 2005 Photon Counting with a 512 x 512 Pixel Array at 1 kHz Frame Rate - A New Wavefront Sensor.](https://reader034.fdocuments.us/reader034/viewer/2022051401/56649d4a5503460f94a2747f/html5/thumbnails/39.jpg)
CH
IPP
Astro
-Particle
Ph
ysics Work
shop
, Verso
ix, May
3rd 2
005
39Bettina Mikulec
X-ray of FishX-ray of Fish
QuickTime™ and aCinepak decompressor
are needed to see this picture.
(… with silicon detector)