Sample Introductory Slide · Title: Sample Introductory Slide Author: rkneale Created Date: 11/4/2010 11:21:59 AM

Visible SpectroPolarimeter (ViSP)SWG Meeting Nov. 24, 2010

R. Casini with P. Nelson, A. de Wijn, M. Knölker,

and P. Huang

ViSP Science Justifications

Science Case: to study the emergence, evolution, and decay of magnetic flux in the solar atmosphere, and the dynamics of solar atmospheric structures

Examples: • formation and decay of active regions• smallscale evolution of quietSun magnetism• magnetic stability of prominences and filaments• magnetic structure of flare and CME precursors• plasma oscillations in the photosphere and chromosphere• kinetic studies of filament eruption• spicules• deposition of mass and kinetic energy from the lower solar atmosphere into

the corona

ViSP Science Justifications

Methodology: • spectropolarimetric observations of magnetic regions• plasma dynamics from Doppler shifts of spectral lines• modeling of polarized line formation (Zeeman effect; atomic polarization;

radiative transfer in inhomogeneous media; radiationMHD simulations)

Requirements: • Highsensitivity, highcadence (not necessarily simultaneous) spectro

polarimetry• multiple spectral lines simultaneously (improve magnetic inference; sample

different atmospheric heights)• high spatial resolution, 2D maps of solar regions• high spectral resolution

• Wavelength range: 380 – 900 nm, three lines simultaneously• Spatial resolution: 2£ ATST diffraction limit (0.07 arcsec @ 630nm)• Spatial FOV: 2£2 a rcmin2 [camera format may limit further]• Spectral Resolution: 3.5 pm @ 630 nm (< 1.7 km/s) → R ~ 180,000• Polarimetric Capability: 103 Icont polarimetry in 10 sec @ required

spectral/spatial res. [may not be possible over entire spectral range in all cases]• Simultaneous operation with:

— Visible Broadband Imager (VBI)— DiffractionLimited NearIR SpectroPolarimeter (DLNIRSP)— Visible Tunable Filter (VTF)

[no spectral overlap unless light from slitjaw is “recycled”]

ViSP Science Requirements

1) Continuous spectral coverage from 380 to 1100 nm2) Meets FOV and spatial resolution requirements [slit height to width is ~4,000:1!]3) Low order gratings (m < 20) allow for large free spectral range:

– observation of wide lines like Ca II H & K, Hα, Ca II IR Triplet [full capability requires 2K px spectral coverage per beam]– observation of multiple lines at different βangles with scientifically useful

spectrograph efficiencies [strongly dependent on grating choice]– reasonable number (~12) of order isolation filters to observe any line from

380 to 1100 nm [filters are relatively inexpensive: ~ 5 K$]4) Multiple gratings (3 to 5) to ensure wavelength diversity with good spectrograph

efficiency [may require custom gratings and associate design effort]5) Automated reconfiguration [a few minutes for three lines]6) Library of photoetched slits [3 provided at first light, corresponding to diffr. limit

@ 450, 650, and 850 nm (respectively: ~16, 23, and 30 µm)]7) Multislit compatible design

ViSP DesignEssential Features

ViSP Optical Concept

ViSP Mechanical Overview

ViSP Table

M8 OAP

M10 DM

BS1

BS2BS3

FM1

Con

text

Cam

Tab

l e

D-K Feed Telescope

(f=7m, F/35)

Context Cam Lens

Collimator Lens

GratingSlit

Counter Scanner

Cam3

Cam2

Cam1

CC

Cam LensPA

ATSTViSP Layout Overview

From slit

Air-gapped doublet collimator lens (f=2.6m, F/26)

Counter scanning fold mirrors

Air-gapped triplet camera lens1 (f=0.85m) Conic 1st surface

Order sorting filter

ProFlux polarization beam

splitter

FMCMOS detector array

Combiner prism

Collimator/Camera #1Detailed View

Typical Wavelength Selection(from SWG Use Cases)

Prominences 587.6 He I (D3) 656.3 Hα 854.2 Ca II1083.0 He I

AR Filaments 630.2 Fe I 656.3 854.21083.0

Photo/Chromosphere 517.3 Mg I (b2) 630.2 656.3 849.8 Ca II 854.21083.0

Photosphere517.3525.0 Fe I553.8 Mn I630.2

Weak Fields453.6 Ti I455.4 Ba II460.7 Sr I589.0 Na I (D2)589.6 Na I (D1)

Other lines of interestOther lines of interest(accessible with versatile gratings in at least one of the beams)

...and more lines, as science and diagnostic capabilities improvebetween now and ATST first light

393.3 Ca II (K)396.8 Ca II (H)486.1 Hβ518.4 Mg I (b1)

617.3 Fe I676.8 Ni I769.9 K I849.8 Ca II

866.2 Ca II 874.1 Mn I1526.0 Mn I1565.0 Fe I

Typical Wavelength Selection(from SWG Use Cases)

Wavelength Selection(from SWG Use Cases)

Prominences 587.6 He I (D3) 656.3 Hα 854.2 Ca II1083.0 He I

AR Filaments 630.2 Fe I 656.3 854.21083.0

Photo/Chromosphere 517.3 Mg I (b2) 630.2630.2 656.3 849.8849.8 Ca II 854.2854.21083.01083.0

Photosphere517.3525.0 Fe I553.8 Mn I630.2

Weak Fields453.6 Ti I455.4 Ba II460.7 Sr I589.0 Na I (D2)589.6 Na I (D1)

Multiple Gratings for Spectral Diversity

Newport RGL53*451E316 l/mm63° blaze

204£408 mm2

α = 71.9°β−α=(29.9°,3.6°)

Scalar Efficienciescalculation

600 650 700 750 800 850 900 950 1000 1050 1100

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

Wavelength vs Order for a Fixed Alpha

5 6 7 8 9 10 11 12 13 14

Wavelength, nm

Esti

ma

ted

Eff

icie

nc

y

0 10 20 30 40 50 60 70 80 90 100

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

Estimated Efficiency vs. Order

5 6 7 8 9 10 11 12 13 14

Beta

Esti

mat

ed

Eff

icie

ncy

Multiple Gratings for Spectral Diversity

TE & TM Efficiencieswith MRCWA

(Rathgen 2008)

Newport RGL53*451E316 l/mm63° blaze

204£408 mm2

α = 71.9°β−α=(29.9°,3.6°)

ViSP Grating Optimization

Iterative search ofoptimal gratings

(both stockand custom)

Prominence Use Case Grating: 254.8 l/mm, blaze = 67.2˚, = 68.7˚α

Wavelength (nm) Diffr. Order ( )˚α β Approx. Efficiency

He I D3 587.6 12 8.8 0.61

Ha 656.3 11 3.5 0.58

Ca II 854.2 8 14.7 0.55

He I 1083.0 6 22.3 0.59

AR Filament Use Case Grating: 305.6 l/mm, blaze = 67.8˚, = 67.8˚α


Fe I 630.2 9 14.0 0.57

Ha 656.3 9 6.3 0.61

Ca II 854.2 7 3.5 0.57

He I 1083.0 5 21.0 0.62

Photo/Chromosphere Use Case Grating: 301.5 l/mm, blaze = 58.3˚, = 65.5˚α


Mg I b2 517.3 11 11.9 0.48

Fe I 630.2 9 12.4 0.48

Ca II 849.8 7 3.5 0.34

Ca II 854.2 6 26.1 0.34

He I 1083.0 5 19.3 0.57

ViSP Grating Optimization

Some use cases, and corresponding optimized custom gratings(not closed; gratings still untested for TE/TM efficiency)

Some Examples ofViSP Configurability

Prominence Use Case – Grating: 213.3 l/mm, blaze = 61.7˚, = 67.4˚α

Ha 656.3

He I D3 587.6

He I 1083.0


AR Filament Use Case – Grating: 305.6 l/mm, blaze = 67.8˚, = 67.8˚α

He I 1083.0

Fe I 630.2

Ca II 854.2


Photo/Chromosphere Use Case – Grating: 267.4 l/mm, blaze = 60.3˚, = 67.2˚α

Ca II 854.2

Ca II 849.8

Fe I 630.2

Air-gapped triplet context camera lens

(f=0.51m, M=0.16)

Conic 1st surface

Bandpass filter at exit pupil

CMOS detector array

From BS3FM1

Feed-M2

Context CameraDetailed View

Center

Slit end

FOV right edge

FOV right corner FOV left corner

FOV left edge

Context CameraOptical Performance

Airy disk@ 630 nm

5 pi

xels

Spectrograph Ch1Optical Performance (NIR)

F = 0.85 m

Center

Slit end

FOV right edge


FOV left edge5

pixe

ls

Spectrograph Ch1Optical Performance (Vis)

F = 0.85 m

Center

Slit end

FOV right edge


FOV left edge5

pixe

ls

Spectrograph Ch1Optical Performance (UV)

F = 0.85 m

Center

Slit end

FOV right edge


FOV left edge5

pixe

ls


F = 1.10 m

Center

Slit end

FOV right edge


FOV left edge5

pixe

ls


F = 1.10 m

Center

Slit end

FOV right edge


FOV left edge5

pixe

ls


F = 1.10 m

Center

Slit end

FOV right edge


FOV left edge5

pixe

ls


F = 1.40 m

Center

Slit end

FOV right edge


FOV left edge5

pixe

ls


F = 1.40 m

Center

Slit end

FOV right edge


FOV left edge5

pixe

ls


F = 1.40 m

Center

Slit end

FOV right edge


FOV left edge5

pixe

ls

• ViSP design meets or exceeds science requirements:– Continuous wavelength coverage over 380 – 1100 nm– Good spectrograph efficiency over entire spectral range

(needs multiple, and likely custom, gratings)– Spatial, spectral resolution, FOV requirements met (camera

format my limit the FOV further)– Quickly reconfigurable– Multislit compatible

• Design is well understood and is relatively low risk – Design heritage from ASP/SPINOR

ViSP Instrument Summary

Documents

Sample Introductory Slide · Title: Sample Introductory Slide Author: rkneale Created Date: 11/4/2010 11:21:59 AM