Transcript CQM multimoded horns

Experimental « Optical » characterization of Planck multimoded horn
Experimental « Optical » characterization of Planck multimoded horn
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)
IWG – 22,23 June 2003 IAP, Observatoire de Paris, J. BROSSARD (IAS)
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Experimental « Optical » characterization of Planck multimoded horn
OBJECTIVE :
Insure that the « optical » behaviour of the CQM multimoded horns is correct.
 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).
IWG – 22,23 June 2003 IAP, Observatoire de Paris, J. BROSSARD (IAS)
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Linear scale
Experimental « Optical » characterization of Planck multimoded horn
Setup of the test bench dedicated to multimoded horn characterisation (IAS)
IWG – 22,23 June 2003 IAP, Observatoire de Paris, J. BROSSARD (IAS)
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Experimental « Optical » characterization of Planck multimoded horn
PRONAOS mirror segment
Feed : black body at 1023 K
During the 1’st and 2’nd campaign, « ecosorb AN 72 »
where added around the different elements.
IAS Sub-mm mirror
Offset paraboloidal
(f=400 mm, f/D=1)
Horn under test
with a integrating
sphere
IWG – 22,23 June 2003 IAP, Observatoire de Paris, J. BROSSARD (IAS)
SPM Cryostat
(4 large detection bands)
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Experimental « Optical » characterization of Planck multimoded horn
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 (101 mm) / predicted ( ~ 6 mm)…….
Isolevel at –3, -6 and –10 dB
 12 dB of dynamique
Not excellent…
but it was the first measurement…!!
IWG – 22,23 June 2003 IAP, Observatoire de Paris, J. BROSSARD (IAS)
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Experimental « Optical » characterization of Planck multimoded horn
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.
Isolevel at –3, -6 and –10 dB
22 dB of dynamique at least (maybe more)
(10 dB better than the 1’st campaign)
IWG – 22,23 June 2003 IAP, Observatoire de Paris, J. BROSSARD (IAS)
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Experimental « Optical » characterization of Planck multimoded horn
Second campaign (August & September 2001 )
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1.25mm Bandpass
0,9
2mm Bandpass
0,8
0,7
I normalised
0,6
Variation of the phase
center location function
of the frequency
0,5
0,4
250 GHz
150 GHz
0,3
0,2
0,1
150 GHz prototype horn
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0,00
10,00
20,00
30,00
40,00
50,00
60,00
70,00
80,00
90,00
Location from horn aperture - Zap (mm)
IWG – 22,23 June 2003 IAP, Observatoire de Paris, J. BROSSARD (IAS)
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Experimental « Optical » characterization of Planck multimoded horn
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.
Alignement of the mirors with a laser
We hope 30 dB of dynamique at least.
Start….in few days on Archeops horn (for the moment)…...first result for the next month….
IWG – 22,23 June 2003 IAP, Observatoire de Paris, J. BROSSARD (IAS)
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Experimental « Optical » characterization of Planck multimoded horn
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).
Far field
beam
power of
the
antenna
vs
defocus
Angular resolution vs defocus
Absolute gain (arbitrary unit) vs defocus
1,4 dB
Horn position
4 mm
z-axis defocus (mm)
z-axis defocus (mm)
IWG – 22,23 June 2003 IAP, Observatoire de Paris, J. BROSSARD (IAS)
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Experimental « Optical » characterization of Planck multimoded horn
Grasp8 modelling : variation of the PLANCK CQM beam
shape versus horn defocus along his axis(545_1 horn)
0.3 dB
Tolerancement valide if :
4 mm
- 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…..)
IWG – 22,23 June 2003 IAP, Observatoire de Paris, J. BROSSARD (IAS)
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Experimental « Optical » characterization of Planck multimoded horn
The End
IWG – 22,23 June 2003 IAP, Observatoire de Paris, J. BROSSARD (IAS)
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Experimental « Optical » characterization of Planck multimoded horn
IWG – 22,23 June 2003 IAP, Observatoire de Paris, J. BROSSARD (IAS)
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