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1 Space Sciences Lab, UC Berkeley, CA, USA High performance microchannel plate detectors for UV/visible Astronomy Dr. O.H.W. Siegmund Space Sciences Laboratory,

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Presentation on theme: "1 Space Sciences Lab, UC Berkeley, CA, USA High performance microchannel plate detectors for UV/visible Astronomy Dr. O.H.W. Siegmund Space Sciences Laboratory,"— Presentation transcript:

1 1 Space Sciences Lab, UC Berkeley, CA, USA High performance microchannel plate detectors for UV/visible Astronomy Dr. O.H.W. Siegmund Space Sciences Laboratory, U.C. Berkeley Work funded by NASA grants, NAG5-8667, NAG , NAG-9149

2 2 Space Sciences Lab, UC Berkeley, CA, USA Existing Detectors Advanced MCP Sensors for Astrophysics Existing Detectors COS 2 x 90mm x 10mm XDL detector GALEX 65mmsealed tube XDL detector High 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 formats

3 3 Space Sciences Lab, UC Berkeley, CA, USA COS FUV Detector and Electronics Advanced MCP Sensors for Astrophysics COS FUV Detector and Electronics

4 4 Space Sciences Lab, UC Berkeley, CA, USA COS FUV Detector QE Advanced MCP Sensors for Astrophysics COS FUV Detector QE CsI cathodes on FUV02 flight detector compared with COS spec Segment A Segment B

5 5 Space Sciences Lab, UC Berkeley, CA, USA COS Detector Event Rate Performance Advanced MCP Sensors for Astrophysics COS Detector Event Rate Performance Global count rate throughput COS FUV local and global count rate performance is better than FUSE, and exceeds specs.

6 6 Space Sciences Lab, UC Berkeley, CA, USA COS Detector Resolution Advanced MCP Sensors for Astrophysics COS Detector Resolution 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. COS FUV detector resolution is ~20µm x 30µm FWHM

7 7 Space Sciences Lab, UC Berkeley, CA, USA Developing Detector Prospects Advanced MCP Sensors for Astrophysics Developing Detector Prospects Raw flat field image Shows MCP multi -fibers, but after thermal correction and division data looks statistical (with ~4400 cnts/resel we 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 memo by Wilkinson/Penton/Vallerga/McPhate.

8 8 Space Sciences Lab, UC Berkeley, CA, USA Photocathode Development Polycrystalline boron doped diamond, band gap 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 Time response <1ns, for Interferometry, Lidar,Molecular fluorescence. Diamond Photocathodes on Silicon and Si MCP’s GaAs photocathode UV efficiency Diamond coated Silicon MCP GaAs Photocathodes on windows, & Diamond Photocathodes on Silicon & Si MCP’s Pre-hydrogenated values Cs activated

9 9 Space Sciences Lab, UC Berkeley, CA, USA GaN Photocathodes Fig.1. Measured quantum efficiency of CsI on MCP’s, CsTe semitransparent (NIST) on MgF 2 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

10 10 Space Sciences Lab, UC Berkeley, CA, USA Silicon MCP Developments Hexagonal pore Si MCP with ~7µm pores, >75% open area Silicon MCP’s Silicon 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

11 11 Space 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 10 6 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 MCP Gain and response uniformity are reasonably good. No “hex” modulation! QDE for Si & bare glass MCP’s vs Wavelength 6µm pore MCP 12/10µm COS Contrast enhanced image of the fixed pattern response to a Hg vapor lamp with a stack of 4 Si MCP’s. ~14mm area, 10 7 counts, ~50µm resolution XDL.

12 12 Space Sciences Lab, UC Berkeley, CA, USA Cross strip anode readout Bottom fingers 32mm x 32mm XS anode, 0.5mm period Cross strip is a multi-layer cross finger layout. Fingers have ~0.5mm period on ceramic. Charge spread over 3-5 strips per axis, Event position is derived from charge centroid. Can encode multiple simultaneous events. Fast event propagation (few ns). Anodes up to 32 x 32mm have been made Signals are routed to anode backside by hermetic vias Packaging can be compact with amp on anode backside Overall processing speed should support >> MHz rates Compact and robust (900°C).

13 13 Space 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. Basic encoding sequence Small, low power ASIC encoding with sparsification reduces data throughput requirements

14 14 Space Sciences Lab, UC Berkeley, CA, USA Outstanding Spatial Resolution/Linearity ~7µm pores are resolved, <3 µm electronic resolution with 10 bit encoding electronics Image linearity is ~1µm level and shows pore misalignments and multi-fiber boundaries Gain required is <4 x 10 5, allows higher local event rates than normal readouts Lower gain means longer overall MCP lifetime due to reduced charge extraction. Cross Strip Anode Readout Flood image of 12µm pore MCP pair at 4 x 10 6 Gain, ≈1mm square area. Small zone of a single 12µm 160:1 L/D MCP at 2x10 5 gain showing apparent displacement of pore images at multifiber boundaries

15 15 Space Sciences Lab, UC Berkeley, CA, USA Resolution of Cross Strip MCP Sensors Air force mask on 6µm pore MCP pair with cross strip readout Gain 1.3 x 10 6 Air force mask on Single 6µm pore MCP optical image

16 16 Space Sciences Lab, UC Berkeley, CA, USA GALEX Early Observations Advanced MCP Sensors for Astrophysics GALEX Early Observations 60mm XDL detectors with CsI and CsTe photocathodes, Launched 6/03 Near-UV Channel M83 M101

17 17 Space Sciences Lab, UC Berkeley, CA, USA M51 – Whirlpool Galaxy Comparison Ultraviolet GALEX Visible DSS Near Infrared 2MASS GALEX Early Data

18 18 Space Sciences Lab, UC Berkeley, CA, USA M31 Andromeda


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