RADIATION HARD UV LED S

Transcription

1 RADIATION HARD UV LED S LIGO Livingston Sasha Buchman Ke-Xun Sun Stanford University LIGO Hanford 11th ICATPP Conference Villa Olmo, 5-9 October, 2009 GP-B, Relativity Mission, Gravity Probe B Page LISA, 1 Laser Interferometer Space Antenna

2 Outline The UV LED Charge management The Relativity Mission, Gravity Probe B GP-B The Laser Interferometer Space Antenna LISA Laser Interferometer Gravitational-Wave Observatory LIGO UV LED Lifetime and Radiation Testing Lifetime Testing Radiation Testing Environmental Testing Page 2

3 UV LED Based on gallium nitride (GaN) UV LED in TO39 packaging Various other packaging ~255 nm central frequency 10 nm WHM UV LED fiber coupled UV LED Performance UV LED with ball lens Page 3

4 UV Charge Management Page 4 Use of UV Sources Photoelectrons for charge management of test bodies (TB) Photoemission from TB and its enclosure Bipolar discharging using photoelectrons and bias Test Bodies Insulators (LIGO, VIRGO, GEO600) Floating conductors (LISA, LPF, GP-B) Charging Sources Handling and installation Pump-down or other gas flow Separation of dissimilar materials Cosmic radiation Patch effects Vacuum field emission (Field >10 7 V/m) Charge Magnitude Typically pc/day Typically <1nC/event

5 Sources for Charge Management I Ion Sprayers / Ion Bars For use in air Standard for clean rooms and benches STATIC CLEAN DC Ionizer DC-ESR-C Clean room use SIMCO, Type P-Sh-N Working distance mm Voltage7000 V - AC UV photoelectrons For use in vacuum GP-B, LISA, GEO 600 GP-B: Hg UV UV LED Page 5

6 Sources for Charge Management II Studies and Proposals For use in vacuum Field emission cathodes 1 Ion & Electron guns 2 Thermal filaments Ion Gun IGL-2101 / IGPS eV to 2000eV 10eV to 1keV Spot : 1-20mm Field emission cathodes Electron Gun ELG-2/ EGPS eV to 2000eV 1nA to 10µA Spot : 0.5-5mm Page 6 Kimball Physics Inc. 1 GP-B Gyroscope Charge Control Using Field Emission Cathodes, S Buchman T. Quinn, M. Keiser and D. Gill, J. Vac. Sci. Technol. B 11, (1993) 2 Charge neutralization in vacuum for non-conducting and isolated objects using directed low-energy electron and ion beams S Buchman, R.L.Byer, D Gill, N A Robertson, and K-X Sun, Class. Quantum Grav. 25 (2008)

7 UV Lamps Lifetime UV Lamp A Intensity vs Operating Hours Normalized Discharge Rates vs Time - LAMP B, -3V Bias E+00 Intensity Monitor y = e x R 2 = Operating Hours Rate (DN/min/IM count) -1.0E E E E E-03 G1 G2 G3 G4-6.0E time (hours) UV Lamp B Intensity vs Operating Hours 1100 Intensity Monitor y = e x R 2 = UV lamp intensity decay time constant ~ 230 hours Large variability of discharge rates between gyroscopes Operating Hours Page 7 The GP-B Hg UV lamps met all requirements

8 GP-B Charge Management Charging Sources Ground Test/Analysis SM Results Levitation < 1V test mv He gas spin-up < 1V test Not observed: < 10 mv Cosmic radiation ~ mv/day (GEANT) mv/day Variations in cosmic radiation charging Shielding: Decreasing from Gyro #1 to Gyro # 4 Solar flares Rotor charge controlled with UV excited electrons 2 UV Hg lamps (254 nm line) 8 UV switches 2 UV fibers per gyroscope UV Lamp A UV Lamp B 1 mv = 1 pc Schematic of GP-B UV architecture 4 gyroscopes UV switch #1A UV switch #1B Gyro #1 Continuous measurement at the 0.1 mv precision Control to 5 mv (meets requirement of 15 mv) Page 8

9 GP-B Charge Control: Discharge of G#1 450mV UV Switches Gyro1 Charge (mv) 70mV/hour discharge Lamp A Lamp B UV Lamp Assembly 100mV 0 mv Day of year, 2004 Page 9 Charge controlled to < 5 mv UV Electrode

10 UV LED Lifetime and Radiation Testing ILX Precision Current Source Computer Function Generator UV LED Lifetime Testing System (both vacuum & nitrogen tests) Modulation (1 khz, 10% duty cycle) GPIB Amp Nitrogen/Vacuum Chambers UV LED UV Photodiode Oscilloscope Signal to UV LED Fast LED Driver and Photodetection PCB Signal from UV Photodiode Driving Signal Page 10

11 UV LED Based AC Charge Management Output fast modulated to generate electron packets Modulation of electrode phase locked for steering electrons Phase adjusted for bipolar charge management UV e - e - UV e - e - Page 11

12 Charging and Discharging of a proof mass potential of +/- 20 mv Results for AC charge transfer studies using a UV LED with observed power or ~11 µw at a center wavelength of nm UV test facility Page 12

13 UV LED Lifetime in Nitrogen, 1 atm Spectral Stability After 19,800 Hours Power Stability After 20,000 Hours UV LED emission spectrum Spectral shift 2 nm shorter UV LED power level No significant power variation Page 13 UV LED lifetime test in Nitrogen: > 28,000 hours (3.2 years)

14 UV LED Lifetime in Vacuum, 10-7 torr Initial Spectrum Power Stability After 9,000 Hours UV LED emission spectrum UV LED power level No significant power variation Page 14 UV LED lifetime test in vacuum: > 17,500 hours (2 years)

15 Proton Irradiation 63.8 MeV proton irradiation test Test at UC Davis Total fluence 2x10 12 proton/cm 2 > 100 years of dose at LISA orbit UV LEDs maintained light output Spectral shape unchanged Power intensity unchanged Page 15

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17 Proton Irradiation Setup at UC Davis Proton Accelerator Ames Chamber (removed for high flux proton irradiation) Protons 63.8 MeV Alignment Aperture Bread Board Stanford Platform Optics Table Lab Jack Page 17

18 Radiation Qualification Test Setup Si Photodiode Protons 63.8 MeV Beam current 20-15,000 pa Flat Window UV LED Ball Lens UV LED SiC Photodiode Aluminum Shielding Block Electronics Electronics Shielding Wall (>1 m Concrete) Page 18 Experimental setup (top view) for UV LED proton radiation tests.

19 UV LED Spectral Shift Measurements Before and After Proton Irradiation UV LED 63.8 MeV proton irradiation test Central wavelength 255 nm for both, no shift observed Page 19

20 Proton Irradiation Results UV LED + SiC Detector 80 pa Run 500 pa Run 15,000 pa Run Proton Fluence Proton Fluence Proton Fluence 1x10 10 p/cm 2 6.3x10 10 p/cm 2 2x10 12 p/cm 2 Proton energy: 59.0 MeV for 80 pa 59.0 MeV for 500 pa 63.8 MeV for 15,000 pa Space proton energy: 2~5 MeV Total fluence: > 100 year Proton fluence in LISA orbit Page 20 Reference for proton test of other LED and laser diodes: A. H. Johnston and T. F. Miyahira, Characterization of Proton Damage in Light- Emitting Diodes, IEEE Trans. Nuclear Science, 47 (6), 1999

21 Environmental Testing UV LED in TO39 packaging tested at Ames Center Shake: 3g + 7g random vibration in all three axes Bake: thermal vac chamber -30 C~+ 60 C, including soak Beam profile, spectra, V-I-P curves staged measurements Preliminary conclusion: PASS Fiber coupled UV LED UV LED mounted for testing Page 21

22 The Shake & Bake Setup at NASA Ames Z-direction shake test platform Bake Chamber x, y - direction shake test platform UV LED SMA Packaging Grating & Mount Page 22 UV LED TOS39 Packaging

23 Shake & Bake Results Beam Profile Spectrum V-I-P Curves Page 23 Before test After shake After shake & bake

24 UV LED s for LISA & LIGO Charge Control Long lifetime >28,000 hours to date Radiation hard Lower power consumption Lower mass AC modulation up to 1 GHz UV LED Performance UV LED Page 24

25 NASA- Stanford Gravity Reference NanoSatellites 1 pm/hz 1/2 Grating Cavity Displacement Sensor Towards ultra high precision gravitation reference sensors and multi vehicle space interferometry 256 nm Deep UV LED Roundest sphere and drag free sensor 1 nrad/hz 1/2 grating angular sensor The Program Frequent launches on ride-along platforms Standard low cost bus configurations month project duration The Benefits New science: Physical, Life, Engineering Critical technology demonstrations Fast advance of NASA mission objectives Train engineers & scientists for the future STANFORD NANOSAT AMES GENESAT NASA-Ames provides nanosatellite Platform, payload integration, and mission operations Technologies Roadmap UV Diode Grating & Laser Grating Displacement Grating Interferometer Other Instruments Tech. Integration Stanford provides gravitational reference technologies Platforms Caging Mechanism Drag Free Flight Other Capabilities Micro/Nanothrusters Formation Flying 3U Cubesat 6U Cubesat About one mission per year beginning in 2011 Estimated total cost per mission is $3-5M Page 25 Falcon 1 Launch Opportunities GeneBox ; Flown 16 July 2006 GeneSat-1; Flown 16 Dec 2006 Pharmasat-1; Launch 10 Dec 2007 Minotaur I Atlas V Minotaur IV Microsatellite Sorties Microsatellite Constellation 2Q 08 1Q 09 3Q 09 1Q 10 4Q 10 2Q 11 4Q 11 Overarching Goal: Provide Rewarding, Focused Objectives for the Next Generation of Space Scientists and Technologists

26 The First Planned Project UV LED Space Demonstration Charge management for high precision GRS Calibration source for UV and X-ray telescope Telescope surface and window de-charging Life maintaining system for space flight Nick Leindecker Payload Functional Components GENESAT Page 26 UV LED Performance UV LED

27 UV LED Testing to Date Lifetime Test Lifetime test in N 2 > 28,000 hours Llifetime test in vacuum: >17,500 hours The spectra in N 2 shifted to shorter wavelength ~2 nm Radiation Test 63.8 MeV proton irradiation test Output power maintained for total fluence 2x10 12 proton/cm 2 (>100 yr LISA ) Spectral shape and power intensity unchanged after proton irradiation Shake & Bake Shake test 3g + 7g random vibration in all three axes Bake: thermal vac chamber -30 C~+ 60 C, +soak Spectral shape and power unchanged 1) LED deep UV source for charge management of gravitational reference sensors, Ke-Xun Sun, B. Allard, S. Buchman, S. Williams, and R. L. Byer Class. Quantum Grav. 23 (2006) S141 S ) UV LED Space Qualification, Ke-Xun Sun, N. Leindecker, S. Higuchi, S. Buchman, R. L. Byer, J. Goebel, M. McKelvey, R. McMurray, Draft in refereeing Page 27