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Design and performances of an Imager Fourier Transform Spectrometer in the UV (IFTSUV). Claudia Ruiz de Galarreta. Thèse dirigée par: Philippon,J.-C. Vial & T. Appourchaux. TABLE OF CONTENTS. SCIENTIFIC BACKGROUND IFTSUV DEFINITION METROLOGY FURTHER WORK. SCIENTIFIC BACKGROUND.
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Claudia Ruiz de Galarreta
Thèse dirigée par:
Philippon,J.-C. Vial & T. Appourchaux
UNDERSTAND THE PHYSICS OF THE OUTER SOLAR ATMOSPHERE
UNSOLVED CORONA HEATING PROBLEM
Requires the study in the UV linesformed in the Chromosphere, the Transition Region and the Corona
T ~ 4500 – 1 000 000K
SPECTRAL DOMAIN (VUV) ~80–140nm
SoHO, EIT (May 1998)
Lymanα, λ = 121.567 nm is the STRONGEST emission line in the VUV
Set of Lα profiles obtainedatdifferent positions in a Prominence, each profile isseparatedbyonearcsecond (SUMER, SoHO).
FOV is not defined!
LαProminence and Filament observed by VAULT.
Lαradiance and profile provide important information on the structure of the outer Solar atmosphere
The study of the outerSolaratmosphererequirescombiningimaging and spectroscopy
The study of the outerSolaratmosphererequires UV adapted instruments
Each pixel records the interferogramproduced by th controlled Optical PathDifference(OPD) betweenarms
The spectrumisrecovered by taking the Fourier Transform (FT) of the interferogram
A face of the cube is an OPD image. A line in the z-direction corresponds to the interferogram
δ = opticalpathdifference(OPD), σ = wavenumber, 2L = max. OPD, dx =samplingstep, N = number of samplingsteps
- Two identical gratings (R1,R2) for splitting and then recombining the beam
- Four mirrors, one of them moves to scan the OPD
- The interfering beam is focused on the 2D detector by an off-axis parabola
* TBD = tobedefined
Solar dynamicsaimsforfastscanand asymmetricalacquisition
,S(s) = measuredsignal
Signal to Noise Ratio (SNR) Budget
Ms = Modulationfunction
Zs = noisecontributions
Signal maybeimproved by the aperture optics of the system
Interfetometer and optics
METROLOGY SYSTEM Dynamicservo-control
HOMODYNE MICHELSON INTERFEROMETER
Interferometer DC output
‘Symmetric’ with IFTSUV
Every fringe corresponds to a path difference of half a wavelength
CLOSED LOOP PIEZO ACTUATORS
MULTIPLE REFLECTIONS CONFIGURATION
l = 632.8 nm
1. OPTICAL FRINGE SUBDIVISION (OFS)
α = angle of incidence of theray(+M)
Θ = anglebetween +M and M
N = number of reflections in +M beforefolding back
2. ANGLE DEVIATION AMPLIFICATION
1.Mirrors: Travel + Diameter + Surfacequality
2. Laser: beamdiameter + Power + Stability
Environmentparameters (pressure, temperature, humidity) have to bepreciselycontrolled and mechanical parts have to bevery stable in order to achievenanopositioning of the system
1. OPTICAL ALIGNMENT
PZT CLOSED LOOP CONTROL
3. HOMODYNE MICHELSON INTERFEROMETER
2 PHASE QUADRATURE DETECTION
ELLIPTICAL CORRECTION ALGORITHM
2.Test & Results