A photoncounting detector for exoplanet missions Don Figer
- Slides: 30
A photon-counting detector for exoplanet missions Don Figer 1, Joong Lee 1, Brandon Hanold 1, Brian Aull 2, Jim Gregory 2, Dan Schuette 2 1 Center 2 MIT for Detectors, Rochester Institute of Technology Lincoln Laboratory Cf. D
Detector Properties and SNR Cf. D 2
Exoplanet Imaging Example • The exposure time required to achieve SNR=1 is much lower for a zero read noise detector. Cf. D 3
Photon-Counting Detectors • Photon-counting detectors detect individual photons. • They typically use an amplification process to produce a large pulse for each absorbed photon. • These types of detectors are useful in low-light and high dynamic range applications – – – Cf. D nighttime surveillance daytime imaging faint object astrophysics high time resolution biophotonics real-time hyperspectral monitoring of urban/battlefield environments orbital debris identification and tracking 4
Operation of Avalanche Photodiode Linear on Geiger mode on Linear Geiger quench mode avalanche Current off arm Vdc + DV Vbr Cf. D Voltage 5
Performance Parameters Single photon input ü Photon detection efficiency (PDE) Ø The probability that a single incident photon initiates a current pulse that registers in a digital counter APD output Discriminator level ü Dark count rate (DCR) Digital comparator output Ø The probability that a count is triggered by dark current Cf. D time Successful single photon detection 6 Photon absorbed but insufficient gain – missed count Dark count – from dark current
Avalanche Diode Architecture Cf. D 7
Zero Read Noise Detector ROIC Cf. D 8 8
Zero Noise Detector Project Goals • Operational – Photon-counting – Wide dynamic range: flux limit to >108 photons/pixel/s – Time delay and integrate • Technical – Backside illumination for high fill factor – Moderate-sized pixels (25 mm) – Megapixel array Cf. D 9
Zero Noise Detector Specifications Optical (Silicon) Detector Performance Phase 1 Goal Parameter Format Phase 2 Goal 256 x 256 1024 x 1024 25 µm 20 µm zero Dark Current (@140 K) <10 -3 e-/s/pixel QEa Silicon (350 nm, 650 nm, 1000 nm) 30%, 50%, 25% 55%, 70%, 35% 90 K – 293 K 100% Pixel Size Read Noise Operating Temperature Fill Factor a. Product of internal QE and probability of initiating an event. Assumes antireflection coating match for wavelength region. Cf. D 10
Zero Noise Detector Specifications Infrared (In. Ga. As) Detector Performance Phase 1 Goal Parameter Format Phase 2 Goal Single pixel 1024 x 1024 25 µm 20 µm Read Noise zero Dark Current (@140 K) TBD <10 -3 e-/s/pixel QEa (1500 nm) 50% 60% 90 K – 293 K NA 100% w/o mlens Pixel Size Operating Temperature Fill Factor a. Product of internal QE and probability of initiating an event. Assumes antireflection coating match for wavelength region. Cf. D 11
Zero Noise Detector Project Status • A 256 x 25 mm diode array has been bonded to a ROIC. • An In. Ga. As array has been hybridized and tested. • Testing is underway. • Depending on results, megapixel silicon or In. Ga. As arrays will be developed. Cf. D 12
Air Force Target Image Cf. D 13
Anode Current vs. Vbias and T Cf. D 14
Dark Current Cf. D 15
GM APD High/Low Fill Factor Cf. D 16
GM APD Self-Retriggering Simulated Histogram of Avalanche Arrival Times Cf. D 17
Radiation Testing Program Overview
Building Radiation Testing Program • Simulate on-orbit radiation environment – choose relevant mission parameters: launch date, mission length, orbit type, etc – Determine radiation spectrum (SPENVIS) • Transport radiation particles through shielding to estimate the radiation dose on the detector (GEANT 4) • Choose beam properties • Design/fab hardware • Obtain baseline data (pre-rad) • Expose to radiation • Obtain data (post-rad) Cf. D 19
Mission Parameters • 2015 launch date, 5 and 11 year mission durations • Radiation flux depends on relative phasing with respect to solar cycle • Choose representative mission parameters specific to each type of orbit – – L 2 Earth Trailing Heliocentric Distant Retrograde Orbits (DRO) Low Earth Orbit (LEO) – 600 km altitude (TESS) • Solar protons – ESP model – Geomagnetic shielding turned on • Trapped e- and p+ – – Cf. D Inside radiation belt AP-8 Min (proton) model AE-8 Max (electron) model Over-predicts flux at high confidence level setting (from SPENVIS HELP page) 20
Orbits Sun-Earth Rotating Frame DRO Earth Trailing Earth DRO 700, 000 ± ~50, 000 km radius from Earth Propagated ~10 years SIRTF Earth Launch C 3 ~ 0. 05 km 2/s 2 185 km altitude 28. 5° inclination DRO Insertion ~196 Days + L Delta-V ~150 m/s Sun L 2 Earth WMAP Cf. D 21 GIMLI Top View (North Ecliptic View)
Integrated Particle Fluence DRO L 2 LEO Earth Trailing Cf. D 22
Total Ionizing Dose and Non-Ionizing Dose (at L 2) Cf. D 23
Radiation Testing Program • Now that we know the radiation dose the detector is likely to see, we need to build a radiation testing program that is going to simulate the radiation exposure on orbit • We need to choose right beam parameters • Energy, dose rate, particle species • Then, choose radiation facility based on factors above as well as our hardware setup requirements • Vacuum, cryogenics, electrical • We make measurements of relevant quantities pre-, during, post-irradiation to characterize change in detector performance Cf. D 24
Beam Parameters • We want to expose the device to 50 krad (Si). • Due to practical considerations, we can only irradiate the device with a mono-energetic beam. • A device subjected to 50 krad would see 1. 18 e 9 Me. V/g of displacement damage dose (DDD) on orbit at L 2. • Ideally, a 50 krad exposure to the proton beam should also yield a DDD of 1. 18 e 9 Me. V/g to simulate condition on orbit. • For 60 Me. V proton beam, the corresponding DDD to a 50 krad exposure is 1. 26 e 9 Me. V/g. Cf. D 25
Beam Parameters • 60 Me. V happens to be where the proportionality between TID and DDD on-orbit is preserved – This depends on thickness of shielding. But if we choose energy around 60 Me. V, the proportionality should be more or less preserved. • Dose Rate – MIL Std 883 Test Method 1019 recommends 50 to 300 rad/sec, although this is for gamma ray beam – 50 rad/sec will still allow us to complete a radiation exposure run in reasonable amount time (~17 min. ) – It makes sense to follow this as higher the rate more chance the device breaks and for dosimetry reasons Cf. D 26
Estimate of Induced Dark Current • KDE = JD/ED =q/(A* )*Kdark= 2. 09 n. A/cm 2/Me. V at 300 K – This gives conversion formula to convert ED to density – Kdark=(1. 9± 0. 6) 105 carriers/cm 3/sec per Me. V/g silicon (Srour 2000) current for • This is for one week after exposure – A = 6. 25*10 -6 cm 2 – = 2. 33 g/cm 3 – q = 1. 6*10 -19 C • For 50 krad exposure to 60 Me. V proton beam is ED is 16. 05 Me. V • Mean Dark Current = KDE ED = 33. 5 n. A/cm 2 at 300 K • Or, Mean Dark Current = 2. 25 f. A/pixel = 14000 e-/pixel/sec at -20 °C (one week after exposure) Cf. D 27
Test Hardware Cf. D 28
Conclusions • We have developed, and are testing, a 256 x 256 photon-counting imaging array detector. • After lab characterization, we will expose four devices to radiation beam and then re-test. Cf. D 29
Detector Virtual Workshop • Year-long speaker series dedicated to future advanced detectors • Talks streamed and archived • Email if interested in being on distribution list: figer@cfd. rit. edu Cf. D 30
- Figer definition
- Pupil plane
- Don figer
- Heilmeier catechism
- Exoplanet exploration program
- Figer counting
- Don't take things that don't belong to you
- California missions map
- Theology of missions
- Spanish missions in georgia
- Spanish missions in texas map
- Aims missions
- California missions map
- What were missions presidios and haciendas
- Association of north american missions
- Esa and jj
- Amplify science harnessing human energy answer key
- Free methodist world missions
- 21 missions
- Why did the spanish establish missions in texas
- Spanish missions in texas
- Critical missions swat
- Day missions library
- Why did the spanish build missions in texas?
- Missions and presidios
- Franklincovey com msb missions personal
- Egg för emanuel
- Strategi för svensk viltförvaltning
- Sura för anatom
- Varians formel
- Rutin för avvikelsehantering