We measured the infrared beam size last Friday and calculated the beam waist size and position:(set the front surface of the BS mirror as origin) the position of the beam waist is z=-12.0623 cm, size is 98.0277 um.

Then we measured the distance between the origin and FI in the PR chamber, and between the origin and 2inch mirror in the BS chamber.

The calculation process is as below:

The distance between the O and FI(z1)=277.5(The path length on the bench)+63.65(From the last hole of the bench to the window)+13.5(the depth of the viewport)+26.5(the distance between the chamber wall and the first mirror)+5.5(the length between and the FI)=386.65cm

The distance between the O and mirror(z2)=z1+16(the FI length plus the distance between FI output and the second mirror)+16(the second mirror to the dichoric mirror)+37(dichoric mirror to the chamber wall)+162(the distance between two chambers)+15(the BS chamber wall to the chamber bench)+57.5(the edge of the bench to the mirror)=648.15cm

The first lens is already put with focal length of 500mm at 48.5cm. Then there are other conditions need to be satisfied.

1.The beam waist should be around the 2inch mirror in BS chamber, and the size should be less than 103 um

2. The size of the beam at FI should also less than 103um.

3. All the lens should on the bench which means should located in the position z<=270 cm, because the last mirror is at 270cm.

I am trying to find a good combination with other two lens, but until now I did not get any result, I will try with more combination or I will add one more lens. Also today I measured the green beam path, but actually I did not know if I should trust the measure result or not, since the green beam is almost the same size or even larger than the size of the beam profiler, so I will try to put another lens first and try to measure it again.