S.Hild and A.Freise

January 2009

Warming up for the OSD workshop

S. Hild January 2009 Slide 2

Reference layout of NDRC

QUESTION => How much astigmatism is introduced by: Divergent beam (strong lens

in input mirrors) passing BS and CP?

Off axis telescopes of PRM1-3 and SRM1-3?

QUESTION => How much astigmatism driven loss we can accept in PRC and SRC?

QUESTION => How to suspend PRM1, PRM3, SRM1 and SRM3?

See talk by Matteo

See talk by Massimo

S. Hild January 2009 Slide 3

NDRC with lenses moved to the BS In case the astigmatism

from the BS and the CPs is too strong…

IDEA: Move lenses out of input mirrors and put them close to the BS (out of IFO arms).

QUESTION => How to suspend the lenses in the BS tank?

QUESTION => Can we buy such lenses (quality, size, …)

QUESTION => Does the Non-Degeneracy still work in this setup?

See talk by Roberto/ Giovanni

S. Hild January 2009 Slide 4

Long NDRC without lenses In case we want/need a design without

any lenses we have to make the recycling cavities as long as possible…

IDEA (from Julien): Move PRM2 into north input tank, passing the beam underneath BS and suspend PRM2 from IM reference mass.

QUESTION => Does non-degeneracy still work?

QUESTION => Is it possible to suspende PRM2 from the reference mass?

QUESTION => Can we fit beams into the vacuum?

QUESTION => Could we fit suspended 35 cm optics onto the injection and detection benches?

See talk by Carlo/Antonio

See talks by Benoit and Eric ?

See slides from Andreas

See talk by Julien

S. Hild January 2009 Slide 5

Pick-off beams

QUESTION => Which pick-off beams are necessary for ISC? BSAR? IM/CP?

Proposed Strategy: all secondary beams (4 beams from each CP, 2 beams from each IM, 3 beams from BS = TOTAL about 15 large beams) are either detected or properly dumped.

S. Hild January 2009 Slide 6

Pick-off beams from IM and CP

QUESTION => Can pick-offs, consisting of several beams, be used for ISC purpose?

QUESTION => Is it possible to deal with divergent pick-off beams (up to about 1m diameter!)

QUESTION => Do we have the space direct pick-offs in 4 different directions (below, above, left and right of main beam)?This plot is only to show effects qualitatively. A proper CAD drawing is required…

S. Hild January 2009 Slide 7

Eliminating pick-offs from IM and CP?

We could get rid of the pick-off beams from the IM-AR by making them etalons: QUESTION: Are the etalons required for reducing noise couplings? QUESTION: Would it be possible to control an IM etalon?

In principle we could get rid of CP secondary beams by aligning the CPs to the main beam: QUESTION: Any noise problems from additional low finesse Fabry Perot? QUESTION: Is it possible to keep the CPs aligned (refernce mass moves when

actuating on main test masses)?

S. Hild January 2009 Slide 8

Extraction of pick-off from BS-AR Pick-off from BS-AR coating needs to

separated from the main beam before being reflected back into the interferometer from the Signal-Recycling mirror.

IDEA: Extract the BSAR-pickoff close to the beam waist between SRM2 and SRM3 (should work even without BS wedge).

QUESTION => Is it possible install a beam director between SR tower and detection tower?

QUESTION => How to dump the other secondary beams of the BS-AR?

S. Hild January 2009 Slide 9