Photon Counting Sensors for Future MissionsDr. Oswald Siegmund

Space Sciences LaboratoryUniversity of California, Berkeley, CA

FUSE rowland circle 200 x 10mmcurved MCP detector, 10k x 300 formatGALEX

65mm MCP sealed

detectors,2k x 2k format

130nm -300nm

M31/32

Imaging

Spectroscopy

QuickTime™ and aGraphics decompressor

are needed to see this picture.Experimental Astrophysics Group

UC Berkeley ---- Mission ExperienceDr. Oswald Siegmund

1992 1993 1994 1995 1996 1997 1998 1999 2000 2000 2002 2003 2004FAUST ALEXIS

EUVE

ORFEUS

FUSE GALEX

IMAGE COS HST

FUVITA

SOHO

Historical Progress of Spatial Resolutionfor photon counting sensors

Imaging and spectroscopy MCP sensors for past and future missions. All sciencetopics show rapid rise in spatial resolution performance requirements.Astronomy/solar sensors are most demanding. Remote sensing less so but have greater timing needs. Planetary sensors emphasize low power/weight

104

105

106

107

108

1990 1995 2000 2005 2010 2015 2020

AstronomyRemote SensingPlanetarySolar

Date

HORUS

MUST

NPOESS

COS

STIS

FUSE

JMEX

NEXUS

EUVE

JUNO

GALEX

IMAGE SI

IMAGE EUVI

PLUTOALICE

ROSETTA ALICE

IMAGER

GUVI

IMAGE WIC

ALEXIS

ORFEUS

SOHO

FAUST

Photon Counting Sensor CharacteristicsNo cosmic ray streaks

No need for accurate pointing stability during long exposures

Cosmic rays rejected, or just dots.

No radiation damage.

Photons time tagged, rebin image with aspect solution

No degradation of cathode QE with time or environment

No cooling required. No need for de-contamination. No CTE changes

No transfer of blank data areas, no noise pedestal

Only photon events and photon-like background registered

Microchannel Plate Detectors

Detector Capabilities Sizes up to >100mm

QE, 60% max (FUV)

High timing resolution, <100ps

High spatial resolution, <10µm

High event rates, >MHz

Low background, 0.02 cm-2 sec-1

Photocathodes convert radiation (photons, particles)

Amplify signal with microchannel plates

Register position and time with electronic readout

Schematic for cross strip readout

High Quantum Efficiency PhotocathodesNew III-V photo-cathodes are under development

1

10

100

100 150 200 250 300 350 400

GaN JG-138

NW-BH071#3

GaN JG-138

SVT3102#2

GaN JG-220

Wavelength (nm)

Early trial sealed tube

Process development samples

& significant improvements in QE are being made

GaAs photocathodes overlapGaN and have high QE into IR

GaN opaque photocathodesshow high QE and longevity

QE @ 600nm < 10-6

STIS

Other materials also show promise, diamond, othe III-V compounds

Advanced Microchannel Plates

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

Background Rate (events cm

-2

sec

-2

)

Threshold (x modal gain)

Residual counts from glass MCP's?

Photo-lithographic silicon based MCP’s - uniform pore pattern. No multifiber boundaries & array distortions of glass MCP’s. Large substrate sizes (100mm) OK, with small pores (<5µm). High temperature tolerance - CVD cathode processes OK. Initial tests are encouraging, but needs more development

Si MCP ~7um hex pores, >75% OAR

Ultra low background rates<0.02 events cm-2 sec-1

8cm Si MCP on 100mm wafer

Diamond on Si MCP

Cross Strip Imaging Readout

Air force mask on 7µm pore MCP pair with 32mm cross strip

Cross strip is a multi-layer cross finger layout.

Event charge centroid gives event positions.

Ultra high spatial resolution (<5µm)

Large formats possible (100mm) in many shapes

Low gain/long lifetime/low fixed pattern noise

Anodes 32 x 32mm have been made.

7µm pore MCP pair at 2x106 gain

ASIC preamps plug directly to

the anode

Gain 4 x 105

MEDIPIX (CMOS) readout for MCP’s

Cathode + MCP + image readout using “Medipix2” ASIC by CERN.

55um pixel @ 256x256 (3-side buttable), 14mm x 14mm CMOS chip .

Pixel level amp, discriminator, gate & counter, to count photon events.

MCP gain only 104, CMOS noise negligible. Very high dynamic range.

Events counted at each pixel for each frame - (No charge transfer).

MCP testbed built, Medipix imaging @ 500MHz rates, 55µm resolution.

1 kHz frame rate noiseless photon counter with GHz counting rate

Single frame shows single photons

Integration shows image resolution

MEDIPIX in MCP housing

Photon Counting Sensor Prospects•QE >50% over 10nm - 900nm range, in selectable bandpasses, with solar blind options.

•Si MCP’s with <5um pores, low fixed pattern noise, low background <0.02 cm-2 sec-1 & lifetimes 100 - 1000x better.

•Cross strip readouts with 20k x 20k resolution, selectable format sizes up to >100 x 100mm, & counting rates >10 MHz, with 100x improved local rates

•CMOS, MEDIPIX, readouts with GHz rates,

1k x 1k abuttable to 2k x 2k with <25um pixels.