Optics ResumeM.Carter

2000-10-25Summary

This is a brief note to bring everyone up on the progress of the optics package. At the Tucsonmeeting, as reported in the summary given by James Lamb and given by myself at the followingtelecom meeting of the 2000-10-25, a design was reached. This design is shown below. Asdescribed in James' summary there are 3 separate styles for the optics.1. Bands 1 and 2; Consist of a cooled horn an ambient lens, which will probably be the cryostat

vacuum seal.2. Bands 3 and 4; Consist of a horn at 4K, cooled lens probably at 77K, an ambient elliptical

mirror, and a flat pick off mirror.3. Bands 5-10; Consist of horn and OMT for 5 and 6, horns plus quasi-optical polarisation

splitting for bands 7-10, which will be followed by a train of mirrors which will put thetelescope waist at the surface of the cryostat. These different designs will be determined bythe different cartridge groups.

Since then I have tried to make this design more concrete with the help of Mark Harman, BernardLazareff and Wes Grammer. The design is shown in figures below.There are some differences from before. The main one is that Mark has been able to increase thediameters of the bands 3 and 4 cartridges to 140 mm. He has done this by moving them into a335mm radius and rotating them by 10 degrees in the direction of the WVR.

Figure 1 optics with cartridges with 4K plate, but no Dewar top

Figure 2 as figure 1

_________________ J tYT l~k4'~-~--- ,~t-vjvp,

Fig 3 Beam on Cryostat top

*1

t-

h t

Beams with cryostat top

Table 1 horn parameters

Band horn horn R 1/2 angle horn waistlength diameter deg waist position

frommouth

1 132.5 29.9 165.75 5.18 9.39 7.582 66.3 15 84.4 5 4.7 3.763 61.1 13.6 68.5 5.7 4.2 5.44 76 12.7 86.4 4.2 3.9 7.25 57.2 9.7 66.2 4.2 3 5.076 66.2 9.4 77 3.5 2.9 5.847 70.4 9.1 80.26 3.25 2.8 6.88

9

10

Band horn length horn R 1/2 angle deg horn waist waist position

diameter from mouth

1 132.5 29.9 165.75 5.18 9.39 7.582 66.3 15 84.4 5 4.7 3.76

3 61.1 13.6 68.5 5.7 4.2 5.44 76 12.7 86.4 4.2 3.9 7.25 57.2 9.7 66.2 4.2 3 5.07

6 66.2 9.4 77 3.5 2.9 5.847 70.4 9.1 80.26 3.25 2.8 6.88

9

10

lens/mirror temp Tk increase mirror waist reflection angle X-polar loss distortion loss mirror temp spillover loss Total ohmic loss Total optic loss Rx temp

increase

300K 12K 4% 12K

300K 13.5K 4.50% 13.5K

70 5K 22.8 50 0.13% 0.26% 300K 0.5%x2 1% 8.90% 12K70 5K 17.5 50 0.09% 0.18% 300 0.5%x2 1% 9.50% 11K

4 0 12.4 33 0.05% 0.10% 4 0.50%

4 0 13.3 33 0.05 0.1 4 0.5

4 0 12.2 40 0.05 0.1 4 0.5

Band: The frequency designation given in the ALMA specificationsHorn length: Length required to give a horn with waist given a delta of about 0.1D1: distance horn phase centre to first focusing deviceFl: focal distance of first focusing deviceD2: distance between first and second focusing devicesF2: focal length of second focusing deviceD3: distance to secondary focus2ndary focus: the difference of the secondary focus, putting the nominal secondary focus between the secondary and the dewar front faceDistance off axis: distance of the window/mirror from the telescope axisReflection angles:the reflection angle going from the feed to the subreflector

band horn dl fl d2 f2 d3 lensi dia lens2 dia win dia secondary focus window/mirror reflection feed distance cartridge

distance off dewar /transmission off cartridge

waist axis angles axis diameter1 9.1 193 190 186 -380 260 0/2.8 35 1702 4.6 96.5 96.5 93 -190 260 0/2.6 35 1703 4.2 107 62 250 105.1 200 120 110 30 40 200 0/50/52 0 1404 3.9 115.2 66 250 96.5 180 110 84 26 20 200 0/50/52 0 1405 3 88.5 42.3 150 62.4 175 67 65 55 0 242.7 33/35.4 45 1706 2.9 82.5 41.4 150 62.4 175 70 66 43 0 238 33/35.2 32 1707 2.8 82.2 43 170 70.7 185 52 58 33 0 92 90/30/40/100 0 1708 23 0 -90 170

9 15 0 -90 170

10 11 0 -90 170WVR 0

cartridge axis win position beam angle to

subreflector

fromdewar axis above cryostat degrees295 120 2.8295 36 2.8

335 30 2.6335 30 2.6295 0 2.6295 0 2.6150 0 1

150 0 1

150 0 1

150 0 1

TBD 0