General requirement

RP requires attenuation to XX mJ.

Pre-2022 RP attenuator

Currently installed

4 mirrors and thin-film polarisers

p-pol as input

Attenuates to 0.5*0.8*0.5*0.1 = 0.02 (2%)

Issues:

4 mirrors and s-pol as input.

Mirrors are 35%R from MPO, AR coating on back and 2 degree wedge.

Attenuation should be down to 0.35^4 = 0.015 (1.5%) or 800 mJ * 0.35^4 = 12 mJ

Reflectivity was tested:

Wedge orientation:

Quote for mirrors: