Eleonora, Keiko

The P and Y coupling with a QPD before the lens 2 was double checked again, as last week we (Adam, Keiko, klog 11922) saw almost no coupling there, where the beam is very far field after the first lens. We confirmed that P and Y didn't couple for either EX or IX excitation.

If somehow the second lens is doing something bad, the beam just after lens1 is enough good. Now we are thinkingto put  one lens f=2000 as the first lens to have a larger waist size with one lens. We will try that tomorrow, and if it doesn't work (*), we will put just one QPD after the original first lens.

- Measured the beam profile after the original lens 1 (1st attachment)
- Beam profile with f=2000 lens as the first lens (2nd attachment)
- Diaggui data double-cheking the coupling again (the rest of the attachment, data is in /users/AOS/191210)
- There are phase differences between the QPD and EXC (????);
      (1) Oplev EX Y to QPD2 PIT (0 deg)
      (2) Oplev EX Y to QPD2 YAW (0 deg)
      (3) Oplev IX P to QPD2 PIT (180 deg)
      (4) Oplev IX Y to QPD2 YAW (0 deg) . .... do we want Y to have also minus between EX and IX?

(*) Akutsu-san is wondering if the near field is anyway bad with any gouy phase telescope design.

Memo: tomorrow we should bring many beam dumps, a 2 inch BS, a 2000mm lens, a 2inch lens mount, many folks to EX sta.