High performance microchannel plate detectors for UV/visible Astronomy

1Space Sciences Lab, UC Berkeley, CA, USA

High performance microchannel plate detectors for UV/visible

Astronomy

High performance microchannel plate detectors for UV/visible

Astronomy

Dr. O.H.W. SiegmundSpace Sciences Laboratory, U.C. Berkeley

Work funded by NASA grants, NAG5-8667, NAG5-11547, NAG-9149


Advanced MCP Sensors for Astrophysics Existing DetectorsExisting Detectors

Advanced MCP Sensors for Astrophysics Existing DetectorsExisting Detectors

COS 2 x 90mm x 10mm XDL detectorGALEX 65mmsealed tube XDL detector

High QE alkali halide cathodes (CsI, KBr) with ~50%QE covering 10nm - 185nmHigh QE alkali halide cathodes (CsI, KBr) with ~50%QE covering 10nm - 185nm

MCP’s with 12µm to 6µm pores, background MCP’s with 12µm to 6µm pores, background 0. 2 events cm-2 sec-1

Cross-delay line readouts with 15µm resolution, 90 x 20mm, 65mm formatsCross-delay line readouts with 15µm resolution, 90 x 20mm, 65mm formats


Advanced MCP Sensors for Astrophysics COS FUV Detector and ElectronicsCOS FUV Detector and Electronics

Advanced MCP Sensors for Astrophysics COS FUV Detector and ElectronicsCOS FUV Detector and Electronics


Advanced MCP Sensors for Astrophysics COS FUV Detector QECOS FUV Detector QE

Advanced MCP Sensors for Astrophysics COS FUV Detector QECOS FUV Detector QE

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RequirementsQE post miniscrub2

WAVELENGTH (Å)

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RequirementsQE post miniscrub2

WAVELENGTH (Å)

CsI cathodes on FUV02 flight detector compared with COS spec

Segment A Segment B


Advanced MCP Sensors for Astrophysics COS Detector Event Rate PerformanceCOS Detector Event Rate Performance

Advanced MCP Sensors for Astrophysics COS Detector Event Rate PerformanceCOS Detector Event Rate Performance

Global count rate throughputGlobal count rate throughput

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Gain and PHD vs. Localized Input Rate

(Single 25µm x 500µm Slit)

Relative Gain

Relative PH width

Relative Gain

Microchannel Pore Input Rate (cps)

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Digital Event Counter (cps)

Fast Event Counter (cps)

COS FUV local and global count rate performance is better than FUSE, and exceeds specs.


Advanced MCP Sensors for Astrophysics COS Detector ResolutionCOS Detector Resolution

Advanced MCP Sensors for Astrophysics COS Detector ResolutionCOS Detector Resolution

COS detector co-added image of 10µm pinholes on 500µm centers & 25µm x 500µm COS detector co-added image of 10µm pinholes on 500µm centers & 25µm x 500µm

slits 200µm apart. Pixels are 6µm x 25µm or ~15,000 x 400 format per segment.slits 200µm apart. Pixels are 6µm x 25µm or ~15,000 x 400 format per segment.

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COS FUV01 Segment A - Pinhole Resolution vs. X

X FWHM(µm)

X centroid (pxl)

COS FUV detector resolutionis ~20µm x 30µm FWHM


Advanced MCP Sensors for Astrophysics Developing Detector ProspectsDeveloping Detector Prospects

Advanced MCP Sensors for Astrophysics Developing Detector ProspectsDeveloping Detector Prospects

Raw flat field imageRaw flat field image

Shows MCP multiShows MCP multi

-fibers, but after-fibers, but after

thermal correctionthermal correction

and division data and division data

looks statistical (withlooks statistical (with

~4400 cnts/resel we ~4400 cnts/resel we

get S/N ~60:1).get S/N ~60:1).

Using FPSPLIT with 4 co-added images each with 60:1 S/N we get S/N of ~100:1 which is in close accord with photon statistics. For analysis see memoby Wilkinson/Penton/Vallerga/McPhate.


Photocathode DevelopmentPhotocathode Development

Polycrystalline boron doped diamond, band gap - 5.47 eV (227 nm) - Solar blind.Hydrogenated diamond is air stable (<10% drop in 18 hours) and is very robust.

GaAs QE up to 50% in the red now possible, low background ≈10 events/sec @-20°CTime response <1ns, for Interferometry, Lidar,Molecular fluorescence.

Diamond Photocathodes on Silicon and Si MCP’sGaAs photocathode UV efficiency

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#2#1#5#821201Si MCP2080120501

Wavelength (Å)

Diamond coated Silicon MCP

GaAs Photocathodes on windows, & Diamond Photocathodes on Silicon & Si MCP’s

Pre-hydrogenated values

Cs activated


GaN PhotocathodesGaN Photocathodes

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GALEX NUV01 CsTe

NIST CsTe diode

CsI #3 2/99 20°

Quantum Efficiency

Wavelength (Å)

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NW-BH071#3

NW-JG238#2

SVT3102#2

SVT2702S-52803

NW-JG238S#3

Quantum Eficiency (%)

Wavelength (nm)

Fig.1. Measured quantum efficiency of CsI on MCP’s,CsTe semitransparent (NIST) on MgF2 window and CsTe semitransparent (GALEX) on thick UV silica windows.

Fig.2. Measured QE of GaN samples on sapphire (300µm) after cesiation, for semitransparent(corrected for substrate transmission) & opaque modes

opaque

semitransparent


Silicon MCP DevelopmentsSilicon MCP Developments

Hexagonal pore Si MCP with ~7µm pores, >75% open area

Silicon MCP’sSilicon MCP’sSilicon MCP’s are made by photo-lithographic methods

Photolithographic etch process - very 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 and “hot” processes OK

UHV compatible, low background (No radioactivity)

Development in collaboration with Nanosciences.

Typical Silicon microchannel plates in test program

25mm diameter (75mm currently feasible)

40:1 to 60:1 L/D (>100:1 possible)

7µm pore size, hexagonal and square pore

~2° bias and 8° bias, resistances ~GΩ, to <100MΩ possible

Working on processing techniques to improve uniformity

Techniques for gain & QE enhancement under investigation

8cm Si MCP on 100mm substrate


Silicon MCP Performance Characteristics

Gain & PHD very similar to glass MCP’s, stacks of Si MCP’s (4) with gain up to 106

QE is similar to good bare glass MCP’s (COS, EUVE, 12/10/6µm)The background rate is lower (0.02 events cm-2 sec-1) than any glass MCPGain and response uniformity are reasonably good. No “hex” modulation!

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Si MCP

Bare glass

Si Hex MCP

QDE

Wavelength (Å)

QDE for Si & bare glass MCP’s vs Wavelength

6µm pore MCP

12/10µm COS

Contrast enhanced image of the fixed pattern responseto a Hg vapor lamp with a stack of 4 Si MCP’s. ~14mm

area, 107 counts, ~50µm resolution XDL.


Cross strip anode readoutCross strip anode readout

Bottom fingers

32mm x 32mm XS anode, 0.5mm periodCross strip is a multi-layer cross finger layout. Cross strip is a multi-layer cross finger layout. Fingers have ~0.5mm period on ceramic.Fingers have ~0.5mm period on ceramic.Charge spread over 3-5 strips per axis, Charge spread over 3-5 strips per axis, Event position is derived from charge centroid.Event position is derived from charge centroid.Can encode multiple simultaneous events.Can encode multiple simultaneous events.Fast event propagation (few ns). Fast event propagation (few ns).

Anodes up to 32 x 32mm have been madeAnodes up to 32 x 32mm have been madeSignals are routed to anode backside by hermetic viasSignals are routed to anode backside by hermetic viasPackaging can be compact with amp on anode backsidePackaging can be compact with amp on anode backsideOverall processing speed should support >> MHz ratesOverall processing speed should support >> MHz ratesCompact and robust (900°C).Compact and robust (900°C).


Cross Strip Anode Electronics Chain

Anode backside showing the external board where preamplifier chips are mounted.

Cross strip anode position encoding electronics test-bed system. All signals amplified and digitized. Can choose up to 12 bits per signal.

X FingersADCPreampShaper50 Ohm Driver

Discriminator1616161616 DIGITALINTERFACEBasic encoding sequence

Small, low power ASIC encoding with sparsification reduces data throughput requirements


Outstanding Spatial Resolution/LinearityOutstanding Spatial Resolution/Linearity~7µm pores are resolved, <3 µm electronic resolution with 10 bit encoding electronicsImage linearity is ~1µm level and shows pore misalignments and multi-fiber boundariesGain required is <4 x 105, allows higher local event rates than normal readoutsLower gain means longer overall MCP lifetime due to reduced charge extraction.

Cross Strip Anode ReadoutCross Strip Anode Readout

Flood image of 12µm pore MCP pair at 4 x 106 Gain, ≈1mm square area.

Small zone of a single 12µm 160:1 L/D MCP at 2x105 gain showing apparent displacement of pore images at multifiber boundaries


Resolution of Cross Strip MCP SensorsResolution of Cross Strip MCP Sensors

Air force mask on6µm pore MCP pairwith cross strip readout

Gain 1.3 x 106

Air force mask onSingle 6µm pore MCP optical image


Advanced MCP Sensors for Astrophysics GALEX Early ObservationsGALEX Early Observations

Advanced MCP Sensors for Astrophysics GALEX Early ObservationsGALEX Early Observations

60mm XDL detectors with CsI and CsTe photocathodes, Launched 6/0360mm XDL detectors with CsI and CsTe photocathodes, Launched 6/03

Near-UV Channel

M83

M101


M51 – Whirlpool GalaxyComparison

UltravioletGALEX

VisibleDSS

Near Infrared2MASS

GALEX Early Data


M31 Andromeda

High performance microchannel plate detectors for UV/visible Astronomy

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