A new CCD optimized for pulsed laser guide star wavefront sensing

Principal Investigator

Co-Investigators

James Beletic Rockwell Scientific Company

Sean Adkins Keck Observatory

Barry Burke MIT Lincoln Laboratory

Charlie Bleau SciMeasure Analytical Systems

Ray DuVarney SciMeasure Analytical Systems

Jerry Nelson Univ. California, Santa Cruz

Richard Stover Lick Observatory

Francois Rigaut Gemini Observatory

Project purposeMake AO CCDs* photon-noise

limitedGoal: 1e- noise at 1 kHz frame

rate

1.Significantly reduce readout noise

A. Increase # of readout ports & use best MOSFET designB. Test the new planar JFET (& use many ports)

2. Use novel design to optimally sample LGS photons

Planar JFETperformance?

Project Phases

1. Produce and test a standard geometry CCD 160 x 160 pixel image array 18 or 21 micron pixels Split frame transfer 20 readout ports

A. Best MOSFETB. Planar JFET

160 x 160 pixelimage area

10 readout ports

80 x 160 pixel1/2 frame storage

lower1/2 frame storage

10 readout ports

16 x 80 pixelsread out of a single port

• Challenges:

LGS spot elongation

WFS CCD: - Readout noise - Readout time

• Assume: Shack-Hartmann WFS

d

L

LGS optimized AO CCD

8-10 meter telescope20 subapertures across the pupil

• Laser-subap separation• Altitude of Na layer• Thickness of Na layer• Altitude of telescope• Zenith angle• Mount (az-el)• AO system location

LGS spot elongation in a specific subaperture is a function of:

Shack-Hartmann subapertureimage plane geometry

Shack-Hartmann subaperture image plane geometry

Shack-Hartmann subaperture image plane geometry

Can bin to 2x2 pixels

LowerReadout

Noise

FasterReadout

More photons per pixel

HigherSNR

Wavefront sensor

subapertures shown with respect to telescope

primary mirror

LGS spots in each

subaperture

Detail of pixel array for

corresponding LGS spot

Clock Lines

Video outputSerial

Register

Pulsed laser overcomes spot elongation

CW LaserPulsed Laser

Can track laser pulse acrossa single subaperture

Spot travel direction

Dump Drain Vdump drain

I1

I2

I3

FS1

FS2

FS3

S1

S2

S3

Image Array

Serial Register

Frame Storage

Voutput gate

SummingWell

2 stageamplifier

OutputSelect

VideoOut

4 serial register pixels to to “warm up” electronics

SW

ResetGate

reset

Phase 2 CCD Design - Subaperture Design

Electronics and cryostat bySciMeasure Analytical

Systems

Come see a SciMeasureCamera Systemat this poster

(with an “old time”e2v chip inside)

AO CCD Project Plan

Phase 1 CCD 160 x 160 pixel std. geometry Test planar JFET Results 2005

160 x 160 pixelimage area

10 readout ports

80 x 160 pixel1/2 frame storage

lower1/2 frame storage

10 readout ports

16 x 80 pixelsread out of a single

port

Phase 2 CCD Pulse LGS geometry Design 2005

• use best phase 1 amp

Fab / test 2006