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Richard - 1 Transmission Degradation for TSIS SIM SSI Variations Workshop 2/ 28- 3/1, 2012 (NIST Gaitherburg)
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The TSIS Spectral Irradiance Monitor: Prism Optical Degradation Studies
Erik Richard, Dave Harber, Joel Rutkowski, Matt Triplett, Kasandra O’Malia Laboratory for Atmospheric and Space Physics (LASP)
University of Colorado, Boulder, Colorado USA
Special thanks to entire NIST SURF and SIRCUS Teams!!
Richard - 2 Transmission Degradation for TSIS SIM SSI Variations Workshop 2/ 28- 3/1, 2012 (NIST Gaitherburg)
• SORCE SIM saw > 30% transmission degradation in 5 years at 220nm
• What caused this degradation? – Which wavelengths were
responsible? – Surface contamination or
bulk volume effect? • Can we mitigate this
degradation on TSIS? • Can we reduce uncertainties
in quantifying over mission?
TSIS Optical Degradation Trade Study
Richard - 3 Transmission Degradation for TSIS SIM SSI Variations Workshop 2/ 28- 3/1, 2012 (NIST Gaitherburg)
TSIS SIM Development Approach TSIS SIM designed for long-term spectral irradiance measurements (climate research) Incorporate lessons learned from SORCE SIM (& other LASP programs) into TSIS SIM to meet measurement requirements for long-term JPSS SSI record
Specific areas addressed in TSIS SIM development
Reduce uncertainties in prism degradation correction to meet long-term stability requirement
• Ultra-clean optical environment to mitigate contamination • Addition of 3rd channel to reduce calibration uncertainties
Improve noise characteristics of ESR and photodiode detectors to meet measurement precision requirement
• ESR : Improved ESR thermal & electrical design • Photodiodes : Larger dyn. range integrating ADC’s (21-bits)
Improve absolute accuracy pre-launch calibration • NIST SI-traceable Unit and Instrument level pre-launch spectral calibrations (SIMRF-SIRCUS)
SORCE SIM
TSIS SIM
Richard - 4 Transmission Degradation for TSIS SIM SSI Variations Workshop 2/ 28- 3/1, 2012 (NIST Gaitherburg)
TSIS SIM Design Overview
Féry prism spectrometer covering the full wavelength range from the UV to IR using only one optical element for spectral dispersion and image quality
Richard - 5 Transmission Degradation for TSIS SIM SSI Variations Workshop 2/ 28- 3/1, 2012 (NIST Gaitherburg)
Richard - 6 Transmission Degradation for TSIS SIM SSI Variations Workshop 2/ 28- 3/1, 2012 (NIST Gaitherburg)
Aperture area ESR
Absorptance
prism transmission
Slit diffraction
Spectral Transfer function
Measurement Equation Overview
ESR detected power
Richard - 7 Transmission Degradation for TSIS SIM SSI Variations Workshop 2/ 28- 3/1, 2012 (NIST Gaitherburg)
Overview of TSIS SIM
Vacuum Door Mechanism
ESR Detector Assy
Fery Prism Assy Shutter/Photodiode Assy
CCD Assy
Fine Sun Sensor
Focal Plane Module
CCD Aperture Ch. A Aperture Ch. B Aperture Ch. C Aperture
Rotational Prism Carrier
External Flex
Richard - 8 Transmission Degradation for TSIS SIM SSI Variations Workshop 2/ 28- 3/1, 2012 (NIST Gaitherburg)
Train wreck occurs here!
Prism Assembly
Richard - 9 Transmission Degradation for TSIS SIM SSI Variations Workshop 2/ 28- 3/1, 2012 (NIST Gaitherburg)
• Transmission window
• Dispersion (dn/dλ) • Absorption
– Leads to heating producing temperature dispersion (dn/dT) causing wavefront error
• Bubble & inclusion content – Leads to scatter
• Striae layers – Leads to wavefront distortion and scatter
• Radiation hardness – Energy or power density
– Compaction & Color center formation
Material Considerations for Refractive Optics
Richard - 10 Transmission Degradation for TSIS SIM SSI Variations Workshop 2/ 28- 3/1, 2012 (NIST Gaitherburg)
Fresnel Refl. Loss Suprasil 1 / 2A Suprasil 311 / 312 Suprasil 300 / 3001
TSIS SIM Level 1 wavelength range
Suprasil (Fused Silica) Transmission
Richard - 11 Transmission Degradation for TSIS SIM SSI Variations Workshop 2/ 28- 3/1, 2012 (NIST Gaitherburg)
• Suprasil 3001 is a high purity synthetic fused silica manufactured by flame hydrolysis of SiCl4
• High index homogeneity – ∆n/n ≤ 1 ppm over CA volume (optically isotropic “3D”-material) – No striations
• Low NIR absorption – Low OH & trace impurities
• 0.25 ppm/cm @ 1064 nm
• 1 ppm/cm @ 1319 nm
Suprasil 3001 Properties
Richard - 12 Transmission Degradation for TSIS SIM SSI Variations Workshop 2/ 28- 3/1, 2012 (NIST Gaitherburg)
< 300 ppb/cm!
Refractive Index Homogeneity
Richard - 13 Transmission Degradation for TSIS SIM SSI Variations Workshop 2/ 28- 3/1, 2012 (NIST Gaitherburg)
Richard - 14 Transmission Degradation for TSIS SIM SSI Variations Workshop 2/ 28- 3/1, 2012 (NIST Gaitherburg)
Full Spatial & Spectral Transmission Mapping Prism measurement geometry is for ESR optical path Stabilized SIRCUS lasers cover 211 – 2400 nm range
Transmission measured over 10 x 10 grid for both s and p-polarizations
Refraction vs. wavelength (Suprasil 3001 fused silica)
Richard - 15 Transmission Degradation for TSIS SIM SSI Variations Workshop 2/ 28- 3/1, 2012 (NIST Gaitherburg)
Richard - 16 Transmission Degradation for TSIS SIM SSI Variations Workshop 2/ 28- 3/1, 2012 (NIST Gaitherburg)
Prism Transmission
55 λ’s x 100 spatial points x 2 polarizations x 4 prisms = 44,000 measurements! (5 months effort)
Richard - 17 Transmission Degradation for TSIS SIM SSI Variations Workshop 2/ 28- 3/1, 2012 (NIST Gaitherburg)
• Fabricate 6 super-polished (SR < 1 ÅRrms ) Suprasil 3001 window samples (same material and process as prisms) and 2 super polished Suprasil 312 windows
• Measure initial transmission from 200-850nm • Expose different windows to the equivalent of a 5-year solar dose
(15 orbits/day 218 days/year) at three different wavelength regions: – 2.5-15 nm : SURF facilities at 380 MeV beam energy – 5-85 nm : SURF facilities at 229 MeV beam energy – 112-165 nm : LASP facilities D2 lamp
• Measure transmission after exposure
• Use results in TSIS SIM exposure scenario (Channel duty-cycling)
Suprasil 3001 Degradation Study
Richard - 18 Transmission Degradation for TSIS SIM SSI Variations Workshop 2/ 28- 3/1, 2012 (NIST Gaitherburg)
Soft X-ray / EUV Exposure (NIST SURF)
SURF BL-2 (100 mA)
Richard - 19 Transmission Degradation for TSIS SIM SSI Variations Workshop 2/ 28- 3/1, 2012 (NIST Gaitherburg)
Mount to filter mech
3001 window (qty 3) 312 window
Interface holes to filter mech
Left to right positioning in beam line
Alignment view port
AXUV100 diode
To beam
Filter mech for diode Filter mech for window holder
BNC access
Exposed to 380 MeV beam
Exposed to 229 MeV beam
SURF Beamline-2 Setup
Richard - 20 Transmission Degradation for TSIS SIM SSI Variations Workshop 2/ 28- 3/1, 2012 (NIST Gaitherburg)
SURF Solar Equivalent Exposures
5-year solar equivalent for 5-85 nm
5-year solar equivalent for 2-15 nm
12 year solar equivalent
22 year solar equivalent
BL-2 current (m
A)
Richard - 21 Transmission Degradation for TSIS SIM SSI Variations Workshop 2/ 28- 3/1, 2012 (NIST Gaitherburg)
229 MeV 380 MeV 70 A-min. dose 12 yr. SE (5-85 nm)
4.5 A-min. dose 22 yr. SE (2-15 nm)
Unprotected Suprasil 3001
Richard - 22 Transmission Degradation for TSIS SIM SSI Variations Workshop 2/ 28- 3/1, 2012 (NIST Gaitherburg)
The unprotected 3001 Window exposed to the 380 MeV beam showed 0.8% change at 200nm
380 MeV 4.5 A-min. dose 22 yr. SE (2-15 nm)
380 MeV Induced Degradation
Richard - 23 Transmission Degradation for TSIS SIM SSI Variations Workshop 2/ 28- 3/1, 2012 (NIST Gaitherburg)
“Wet”, SS312 Protection Window
2.5-15nm at 22 years solar equivalent
Protected Window
This window protected behind the SS312 window, both of which were exposed to the 380 MeV beam. This window saw no significant degradation
SS312 Window saw small but significant loss of transmission (~0.5% at 200nm)
312
“Protected” Suprasil 3001: 380 MeV
Richard - 24 Transmission Degradation for TSIS SIM SSI Variations Workshop 2/ 28- 3/1, 2012 (NIST Gaitherburg)
Rotational feed thru
D2 light Into chamber
Window splitter
Mounting plate
Window mounting arm Chamber Interior
Diodes MgF2 Beam Splitter
Aperture 2
Window Identical, empty aperture
Second diode is used to account for the D2 lamp variability over exposure time
Window Housing
FUV Exposure Setup: “Frankentank”
Richard - 25 Transmission Degradation for TSIS SIM SSI Variations Workshop 2/ 28- 3/1, 2012 (NIST Gaitherburg)
Time integrated energy per unit area seen by the window (from D2 lamp) and solar output in 5 years (1AU). Result: 5+ year solar equivalent dose from about 112-165 nm.
FUV Exposure (112-165 nm)
Baked out tank until “clean” • criteria: considered clean if all masses above 50 amu are below 10-10 torr p.p.
Measured before and after irradiation
320 hours Total D2 lamp exposure
Residual Gas Analyzer (RGA) Scans
Richard - 26 Transmission Degradation for TSIS SIM SSI Variations Workshop 2/ 28- 3/1, 2012 (NIST Gaitherburg)
The unprotected 3001 Window exposed to 112-165 nm Showed 8% change at 200nm
FUV Induced Degradation
Richard - 27 Transmission Degradation for TSIS SIM SSI Variations Workshop 2/ 28- 3/1, 2012 (NIST Gaitherburg)
Initial
Richard - 28 Transmission Degradation for TSIS SIM SSI Variations Workshop 2/ 28- 3/1, 2012 (NIST Gaitherburg)
Final
Richard - 29 Transmission Degradation for TSIS SIM SSI Variations Workshop 2/ 28- 3/1, 2012 (NIST Gaitherburg)
Surface Cleaning
Richard - 30 Transmission Degradation for TSIS SIM SSI Variations Workshop 2/ 28- 3/1, 2012 (NIST Gaitherburg)
Surface Re-polish : 20 um removed
Richard - 31 Transmission Degradation for TSIS SIM SSI Variations Workshop 2/ 28- 3/1, 2012 (NIST Gaitherburg)
Protected Window Degradation
The protected 3001 Window exposed to λ > 200 nm Showed 2% change at 200nm
Richard - 32 Transmission Degradation for TSIS SIM SSI Variations Workshop 2/ 28- 3/1, 2012 (NIST Gaitherburg)
• One final test was done to test the Suprasil 3001 NUV degradation
• A sample of Stycast 2850FT was added to the tank
• The RGA scans of before and after the test still appeared to be fairly clean.
• In this test we saw an 18% difference at 200 nm in our transmission, from 90% down to 73%. To compare: previous tests gave transmission degradations of only 8%.
• This gives impetus for rigidly cleaning and baking out all optical cavity components before assembly.
*Note the sample was not baked- out before this test
Contamination: Stycast 2850FT
Richard - 33 Transmission Degradation for TSIS SIM SSI Variations Workshop 2/ 28- 3/1, 2012 (NIST Gaitherburg)
Exposure Degradation over Mission Life