Coronagraphs

Classical Lyot

Pupil Masks

Two pupil masks are currently available, in addition to “open” (no mask).

Coronagraph Pupil Masks

fwpupil Position

Description

abs. throughput

design file

scale in telescope pupil [m/pix]

scale at coronagraph pupil [mm/pix]

open

No mask, just the telescope pupil. Note: design file includes mask over bump.

100%

magMask.fits.gz

0.0067528

0.0093501

bump-mask

Undersized pupil, oversized central obscuration, oversized spiders, and mask over bump

86.75%

bumpMask.fits.gz

0.0067528

0.0093501

fat-spider

Same as bump-mask, but one extra-oversized spider. Intended for kernel-phase type WFS.

Focal Plane Masks

There are two chrome dots on glass plates. Note: optical densities are estimated from standard chrome.

Small spot: 272 um diameter. fwfpm position: lyotsm

lyotsm characteristics

lambda [um]

spot radius [lam/D]

opt. dens.

0.600

3.285

5.0

0.656

3.00

4.75

0.700

2.82

4.56

0.800

2.46

4.11

0.900

2.19

3.67

1.000

1.97

3.22

Large spot: 453 um diameter. fwfpm position: lyotlg

lyotlg characteristics

lambda [um]

spot radius [lam/D]

opt. dens.

0.600

5.47

5.0

0.656

5.00

4.75

0.700

4.69

4.56

0.800

4.10

4.11

0.900

3.65

3.67

1.000

3.28

3.22

Lyot Stops

We have experimented with three Lyot stops with different characteristics. The labels “Large” and “Small” here refer to the clear aperture, i.e. large means a large clear aperture and therefore higher throughput. In practice we have used only LyotLg1 for observations. LyotSm is presently removed from the instrument.

LyotLg1

parameter

value

notes

fwlyot Position

LyotLg1

Throughput

63.8%

not incl. FPM

Image

../_images/coronagraph_LyotLg1.png

Outer Diam.

7.020 mm

at 9 mm pupil plane

Inner Diam.

4.620 mm

Spider Width

0.383 mm

Bump Diam

1.149 mm

FITS file

lyotMaskLarge1.fits.gz

FITS scale at M1

0.0067528

m/pixel

FITS scale at fwlyot

0.0093501

0.0093501

DXF File

LyotStop_large1.DXF

LyotLg2

parameter

value

notes

fwlyot Position

LyotLg2

Throughput

57.3%

not incl. FPM

Image

../_images/coronagraph_LyotLg2.png

Outer Diam.

8.041 mm

at 9 mm pupil plane

Inner Diam.

3.600 mm

Spider Width

0.383 mm

Bump Diam

1.149 mm

FITS file

lyotMaskLarge2.fits.gz

FITS scale at M1

0.0067528

m/pixel

FITS scale at fwlyot

0.0093501

0.0093501

DXF File

LyotStop_large2.DXF

LyotSm

parameter

value

notes

fwlyot Position

LyotSm

removed from instrument

Throughput

33.35%

not incl. FPM

Image

../_images/coronagraph_LyotSm.png

Outer Diam.

7.800 mm

at 9 mm pupil plane

Inner Diam.

3.800 mm

Spider Width

0.383 mm

Bump Diam

1.149 mm

FITS file

lyotMaskSmall.fits.gz

FITS scale at M1

0.0067528

m/pixel

FITS scale at fwlyot

0.0093501

0.0093501

DXF File

LyotStop_small.DXF

PIAA Classical Lyot Coronagraph (PIAACLC)

Phase-induced amplitude apodization (PIAA) optics reshape the beam in the pupil and focal planes, enabling more starlight suppression at low angular separations and higher throughput at large angular separations.

Inverse apodization optics after the focal plane mask correct for off-axis field effects to remove comatic distortions on companions. Inverse PIAA optics are identical to forward PIAA optics. Optical path according to naming convention is PIAA0->PIAA1->fpm->iPIAA1->iPIAA0.

The process of pupil remapping before and after the focal plane is illustrated in Guyon et al 2010:

Drawing of pupil remapping
PIAA optics

Optic name

Clear aperture diameter (mm)

design file

scale in pupil [m/pix]

Height map (um)

PIAA0

10

piaa0.fits.gz

0.151e-5

../_images/coronagraph_PIAA0.png

PIAA1

10

piaa0.fits.gz

0.151e-5

../_images/coronagraph_PIAA1.png

Coronagraph performance simulations

656nm simulations (λ/D = 20.81marcsec, BW = 651nm-661nm)

900nm simulations (λ/D = 28.56marcsec, BW = 855nm-945nm)

Throughput for different coronagraph arrangements at 656nm Throughput for different coronagraph arrangements at 900nm
Throughput for different coronagraph arrangements at 656nm Contrast for different coronagraph arrangements at 900nm
Inverse-Poisson SNR equivalent for different coronagraph arrangements at 656nm Inverse-Poisson SNR equivalent for different coronagraph arrangements at 900nm
Inverse-Speckle SNR equivalent for different coronagraph arrangements at 656nm Inverse-Speckle SNR equivalent for different coronagraph arrangements at 900nm

Simulated throughput data for 656nm

Simulated throughput data for 900nm

Simulated contrast data for 656nm

Simulated contrast data for 900nm

Vector Apodizing Phase Plate (vAPP)

To be documented.