David Burke Maynooth University Department of Experimental Physics Optical Simulations David Burke Maynooth University Department of Experimental Physics

MODAL MODAL (Maynooth Optical Design and Analysis Laboratory) Uses Physical Optics and GBM Verified against GRASP

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 obtained by exciting horn with an on-axis plane wave

Farfield pattern of Horn: 220 GHz

Farfield pattern of Horn: Comparison with Mario’s result

Farfield pattern of Horn:150 GHz

Farfield pattern of Horn: Asymmetry of the E and H planes 150 GHz 220 GHz

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

Spreading of beams due to bandwidth: Results

Spreading of beams due to bandwidth: Central cut The spread data provided a reduction of the FWHM of the central peak

3. Coldstop Restricted to 200 mm diameter (maximum) circular coldstop due to filter size that can be made in Cardiff Performed 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

Coldstop footprint

Coldstop affected beams Some beams are affected when the coldstop gets small enough (specifically at 165 mm)

Coldstop: X21Y06

Coldstop: X17Y02

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 pattern The lower and higher frequency bands were examined

0.05 mm tolerance: 130 and 190 GHz

0.05 mm tolerance: 150 and 220 GHz

0.05 mm tolerance: 170 and 250 GHz

240 GHz 0.05 mm Also Lateral shifts, thicker plates

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

Calibration source simulation Simulated results in MODAL matched the results obtained from GRASP 6.57% power from emitted beam captured at focal plane

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)

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%

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%

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