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
2Space Sciences Lab, UC Berkeley, CA, USA
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
3Space Sciences Lab, UC Berkeley, CA, USA
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
4Space Sciences Lab, UC Berkeley, CA, USA
Advanced MCP Sensors for Astrophysics COS FUV Detector QECOS FUV Detector QE
Advanced MCP Sensors for Astrophysics COS FUV Detector QECOS FUV Detector QE
0
0.1
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0.6
1100 1200 1300 1400 1500 1600 1700 1800
RequirementsQE post miniscrub2
WAVELENGTH (Å)
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0.5
1100 1200 1300 1400 1500 1600 1700 1800
RequirementsQE post miniscrub2
WAVELENGTH (Å)
CsI cathodes on FUV02 flight detector compared with COS spec
Segment A Segment B
5Space Sciences Lab, UC Berkeley, CA, USA
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
0.6
0.8
1
1.2
1.4
1.6
1.8
2
0.1 1 10 100
Gain and PHD vs. Localized Input Rate
(Single 25µm x 500µm Slit)
Relative Gain
Relative PH width
Relative Gain
Microchannel Pore Input Rate (cps)
0
20000
40000
60000
80000
100000
0 50000 100000 150000 200000 250000
Digital Event Counter (cps)
Fast Event Counter (cps)
COS FUV local and global count rate performance is better than FUSE, and exceeds specs.
6Space Sciences Lab, UC Berkeley, CA, USA
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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0 2000 4000 6000 8000 10000 12000 14000 16000
COS FUV01 Segment A - Pinhole Resolution vs. X
X FWHM(µm)
X centroid (pxl)
COS FUV detector resolutionis ~20µm x 30µm FWHM
7Space Sciences Lab, UC Berkeley, CA, USA
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.
8Space Sciences Lab, UC Berkeley, CA, USA
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
0.001
0.01
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1
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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
9Space Sciences Lab, UC Berkeley, CA, USA
GaN PhotocathodesGaN Photocathodes
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1500 2000 2500 3000 3500 4000 4500
GALEX NUV01 CsTe
NIST CsTe diode
CsI #3 2/99 20°
Quantum Efficiency
Wavelength (Å)
0
10
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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
10Space Sciences Lab, UC Berkeley, CA, USA
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
11Space Sciences Lab, UC Berkeley, CA, USA
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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0.05
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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.
12Space Sciences Lab, UC Berkeley, CA, USA
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).
13Space Sciences Lab, UC Berkeley, CA, USA
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
14Space Sciences Lab, UC Berkeley, CA, USA
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
15Space Sciences Lab, UC Berkeley, CA, USA
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
16Space Sciences Lab, UC Berkeley, CA, USA
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
17Space Sciences Lab, UC Berkeley, CA, USA
M51 – Whirlpool GalaxyComparison
UltravioletGALEX
VisibleDSS
Near Infrared2MASS
GALEX Early Data
18Space Sciences Lab, UC Berkeley, CA, USA
M31 Andromeda