Optical Simulations David Burke - PowerPoint Presentation

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Optical Simulations

David Burke

Maynooth University

Department of Experimental Physics

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MODAL

MODAL (Maynooth Optical Design and Analysis Laboratory)

Uses Physical Optics and GBM

Verified against GRASP

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1. Farfield pattern

of Horn (w/ M.

Zannoni

)

Mario measured the pattern of the horn in the far field in the Lab (at 60 cm)In MODAL the beam profile was investigated at 10, 20, 30, 40, 50 and 60 cm

The 60 cm data was compared to the data that was obtained by Mario

Results obtaine

d by e

xciting horn

with an on-axis plane wave

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Farfield pattern of

Horn: 220 GHz

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Farfield pattern of Horn: Comparison with Mario’s result

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Farfield pattern of Horn:150 GHz

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Farfield pattern of Horn: Asymmetry

of th

e E and H planes

150 GHz

220 GHz

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2. Spreading of beams due to bandwidth

Due to QUBIC operating at a broad range of frequencies the spread of the beam was investigated

Specifically looked at the lower range (130-170 GHz)

Compared the spread with the central frequency in the lower band

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Spreading of beams due to bandwidth:

Results

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Spreading of beams due to bandwidth:

Central cut

The spread data provided a reduction of the FWHM of the central

peak

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3. Coldstop

Restricted to

200

mm diameter (maximum)

circular coldstop due to filter size that can be made in CardiffPerformed tests in MODAL, only including the mirrors and the

coldstop

, to see if this smaller coldstop would have much of an effect on the beams on the focal plane

Also tested to see what is the minimum circular diameter at which the instrument shows measurable difference

This occurred at 165 mm diameter

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Coldstop footprint

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Coldstop affected beams

Some beams are affected when the

coldstop

gets small enough (specifically at 165 mm)

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Coldstop: X21Y06

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Coldstop: X17Y02

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4. Horn ring radii tolerance

Created geometry files with radii variations

of

0.05 mm

SCATTER was used to generate the far field plots and these were compared with the ‘perfect’ far field patternThe lower and higher frequency bands were examined

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0.05 mm tolerance: 130 and 190 GHz

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0.05 mm tolerance: 150 and 220 GHz

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0.05 mm tolerance: 170 and 250 GHz

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240 GHz 0.05 mm

Also Lateral shifts, thicker plates

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5. Calibration source simulation (w/ M. De Petris)

Winston cone (calibration

source) was put on the edge of the horn array

The specifications were obtained from D.

Buzi and M. De

Petris

Positioned at (0,-181.11,0) mm in GRF

50

º

FWHM

Simulations were performed in MODAL only including the mirrors

Results were compared with GRASP

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Calibration source simulation

Simulated results in MODAL matched the results obtained from GRASP

6.57% power from emitted beam captured at focal plane

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Calibration source

simulation

When the source was rotated (24

º

as recommended by D. Buzi and M. De

Petris

) to be centred on the primary, the

power

on the focal plane was still

low (only

3.37% of the emitted power captured)

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Calibration source simulation

Source

was put in centre of the horn array to check the power

Power on the primary – 80.18%Power on the secondary – 73.98%Power on the focal plane

– 9.51

%

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Calibration source (30 º FWHM)

Investigated the power collected by a cone that had a beam with a FWHM of 30

º

This gave a collected power

of 15.58%

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Future Work

Examine the effect of a raised ring on the mirrors

Test tolerance/

allignment

of the mirror positions in the technical demonstrator at room temperature.Most urgent, using

Zemax