Today we could start to work on the ALS line on the EIB. A sketch of the pick off is shown in fig.1.



We started by characterizing the beam at the input of the EIB.
Since there are 45W coming from the LB, we could only analyze the beam after M1c, which is a beam splitter 97/3 made from the LMA (the characterization of the mirrorgives  made by the LMA gives transmittivity of 2.7% at 45°  polar S. The AR coating on the second surface has a reflectivity of 260 ppm). We added another BS 97/3 in order to further attenuate the beam for the beam scan.
%beam at the input of EIB
Z=[54 95.5 124 175]*1e-2; %beam at the input of EIB
Wx=[1367 1516 1706 2144]*1e-6*0.5; Wy=[1370 1511 1685 2055]*1e-6*0.5;
The waist position is z0 = 13 cm from the EIB border, and its value w0 = 638 um. (fig.2 )

This is quite consistent with the values taken from the optocad (on which Matthieu based the telescope, shown in fig 3). Since the telescope is designed positioning L1 29cm away from the waist of the beam which is 638 um, we positioned L1 13 cm + 29 cm from the EIB border. We characterized it (shown in fig 4):
%beam after L1
Z=[54 95.5 124 175]*1e-2; %beam after L1
Wx=[1001 855 1147 1622]*1e-6*0.5; Wy=[999 900 1167 1562]*1e-6*0.5; 

We installed after 75cm from L1 the diverging -70mm lens and the 150mm lens, spaced by around 8.6cm (verifying after these two that we have the good waist with the beam scan).