stefan hild 1ilias wg1 meeting, june 2005 title beam clipping problems in geo 600 ??...
TRANSCRIPT
Stefan Hild 1 Ilias WG1 meeting, June 2005
Title
Beam clipping Problemsin GEO 600 ??
Max-Planck-Institut für Gravitationsphysik(Albert-Einstein-Institut)
Stefan Hild Ilias WG1 meeting, June 2005
Stefan Hild 2 Ilias WG1 meeting, June 2005
Introduction
• After installation of new Power Recycling mirror less light power was observed than expected:
• Hypothesis: Mode matching into PR cavity is not too bad (?)
• Hypothesis: beam is clipping somewhere inside the cavity
Expected (simulations) 4.5 kWMeasured 1.5 kW
Stefan Hild 3 Ilias WG1 meeting, June 2005
Simple model cavityIn
trac
avity
pow
er [
W]
refle
cted
pow
er [
W]
Losses in cavity
overcoupled undercoupled
Simple model: 2 mirror cavity, 1.7 W incident, T1 = 900ppm, T2 represents losses
Looking for intracavity losses of the order of 500 ppm
reality
expected
Stefan Hild 4 Ilias WG1 meeting, June 2005
Power Recycling reaction mass
CCD
CCD
Clearly much light on the reaktion mass, but at least beam seems to be centered (in respect to the reaction mass)
Main beam
Stefan Hild 5 Ilias WG1 meeting, June 2005
Potential clipping spots in TCC
MPR
dark port
east arm
north arm
Stefan Hild 6 Ilias WG1 meeting, June 2005
Power Recycled Michelson
Used HeNe-Laser from endstadions to project the free aperture onto MPR reaction mass.
Result: no clipping inside the power recycling cavity
Stefan Hild 7 Ilias WG1 meeting, June 2005
Signal Recycling cavity
We definitely see clipping between beamsplitter and MSR (see blue line)
HeNe from far end locked DRMI
Side note: there is also clipping on MSR reaction mass.
Stefan Hild 8 Ilias WG1 meeting, June 2005
Smoking gun: BDBSs1
CC
D
Suspect the beam to clip the beam dump (blue arrows)
Stefan Hild 9 Ilias WG1 meeting, June 2005
E n d
Stefan Hild 10 Ilias WG1 meeting, June 2005
Misalignment of MSR
Stefan Hild 11 Ilias WG1 meeting, June 2005
Dark port image
Stefan Hild 12 Ilias WG1 meeting, June 2005
Strange beam pattern @ MFE