Experimental « Optical » characterization of Planck multimoded horn

1IWG – 22,23 June 2003 IAP, Observatoire de Paris, J. BROSSARD (IAS)

People involved in this activity are :

- J.M Lamarre……………………………(LERMA, Observatoire de Paris, France)

- B. Maffei………………………………………………...(Cardiff University, UK)

- A. Murphy, V.Yurchenko, E.Gleeson……………(Maynooth University, Ireland)

- I. Ristorcelli……………………………………………(CESR, Toulouse, France)

- B. Leriche, Y.Longval, J. Brossard……….…………………(IAS, Orsay, France)

Experimental « Optical » characterization of Planck multimoded horn

Experimental « Optical » characterization of Planck multimoded horn

2IWG – 22,23 June 2003 IAP, Observatoire de Paris, J. BROSSARD (IAS)

Needs to crosscheck the theoritical prediction realised by Maynooth’s team and the measurement made at IAS (Orsay) on a small antenna (D=400 mm, f/D=1).

We want to make a full pattern comparison as was done between Maynooth’s software and Grasp8 for multimoded horn modelling (example horn at 545 GHz) :

At last, we want to analyse the level of tolerancement relative the position of the B2B horn with respect to the 100 mK horn. (And maybe… explain the Archeops beam distorsion concerning the FPU reconstruction made on Jupiter during the last fly).

OBJECTIVE :

Insure that the « optical » behaviour of the CQM multimoded horns is correct.

Linear scale

Experimental « Optical » characterization of Planck multimoded horn

3IWG – 22,23 June 2003 IAP, Observatoire de Paris, J. BROSSARD (IAS)

Setup of the test bench dedicated to multimoded horn characterisation (IAS)

Experimental « Optical » characterization of Planck multimoded horn

4IWG – 22,23 June 2003 IAP, Observatoire de Paris, J. BROSSARD (IAS)

PRONAOS mirror segment

Horn under test with a integrating

sphere

Feed : black body at 1023 K

IAS Sub-mm mirrorOffset paraboloidal (f=400 mm, f/D=1)

During the 1’st and 2’nd campaign, « ecosorb AN 72 »

where added around the different elements.

SPM Cryostat(4 large detection bands)

Experimental « Optical » characterization of Planck multimoded horn

5IWG – 22,23 June 2003 IAP, Observatoire de Paris, J. BROSSARD (IAS)

First campaign (June 2001 ) - Horn : Archeops horn (monomode at 353 GHz and multimode at 545 GHz). - Detection in band 4 of SPM : 0 = 403 GHz, band width of 76 % (250< 0<550 GHz) - Source : Black body « Infrared Lab » (T=1023 K)

Phase center : measured (101 mm) / predicted ( ~ 6 mm)…….

12 dB of dynamique

Isolevel at –3, -6 and –10 dB

Not excellent…

but it was the first measurement…!!

Experimental « Optical » characterization of Planck multimoded horn

6IWG – 22,23 June 2003 IAP, Observatoire de Paris, J. BROSSARD (IAS)

Second campaign (August & September 2001 ) - Horn : prototype horn designed at 150 GHz - Detection « Cardiff cryostast » : 0= 150 GHz with a band width of 25 %. - Source : Mercury Arc lamp.

22 dB of dynamique at least (maybe more)(10 dB better than the 1’st campaign)

Isolevel at –3, -6 and –10 dB

Experimental « Optical » characterization of Planck multimoded horn

7IWG – 22,23 June 2003 IAP, Observatoire de Paris, J. BROSSARD (IAS)

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Location from horn aperture - Zap (mm)

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1.25mm Bandpass

2mm Bandpass

150 GHz prototype horn

Variation of the phase center location function

of the frequency

150 GHz

250 GHz

Second campaign (August & September 2001 )

Experimental « Optical » characterization of Planck multimoded horn

8IWG – 22,23 June 2003 IAP, Observatoire de Paris, J. BROSSARD (IAS)

Third campagne (June-September 2003…(?) ) - Horn : CQM multimoded horn (545 and 857 GHz) - Source : « Oriel » Mercury Arc lamp (100 Watts). - Absorbant used now are better than « Ecosorb AN 72 » used previously (for 1’st and 2’nd campaign) - Coupling between integrating sphere and bolometer has been improved with a lens between.

We hope 30 dB of dynamique at least.

Start….in few days on Archeops horn (for the moment)…...first result for the next month….

Alignement of the mirors with a laser

Experimental « Optical » characterization of Planck multimoded horn

9IWG – 22,23 June 2003 IAP, Observatoire de Paris, J. BROSSARD (IAS)

The measured beam will be compared with a GRASP8 multimoded computation (J. Brossard, with the help of CNES) using the « S21 » scattering matrix diffusion computed by Maynooth (E. Gleeson).

Example of beam variation wrt to defocus along horn axis for a multimoded horn at 545 GHz (central frequency only).

Angular resolution vs defocus

Horn position

Far field beam

power of the

antenna vs

defocus

Absolute gain (arbitrary unit) vs defocus

z-axis defocus (mm)z-axis defocus (mm)

4 mm

1,4 dB

Experimental « Optical » characterization of Planck multimoded horn

10IWG – 22,23 June 2003 IAP, Observatoire de Paris, J. BROSSARD (IAS)

Grasp8 modelling : variation of the PLANCK CQM beam shape versus horn defocus along his axis(545_1 horn)

4 mm

0.3 dB

Tolerancement valide if :

- all the modes are coupling from the B2B horn to the bolometer with the same efficency

- the band width effect is negligeable…….(see Anthony’s presentation for more details…..)

Experimental « Optical » characterization of Planck multimoded horn

11IWG – 22,23 June 2003 IAP, Observatoire de Paris, J. BROSSARD (IAS)

The End

Experimental « Optical » characterization of Planck multimoded horn

12IWG – 22,23 June 2003 IAP, Observatoire de Paris, J. BROSSARD (IAS)