LIGO Document E1200162-x0
- Document tree for the ISC tables in the End Stations.
Each end station has one ISC optical table. Each table includes:
1) ALS laser; dual-frequency outputs (532 nm & 1064 nm). The 532 nm output is directed into the end station chamber, through the Transmission Monitor to the ETM. The 532nm beam is reflection locked to the arm cavity as part of ALS system. ISCTEnd contains the opto-mechanical/electronic hardware for this reflection locking.
2) Sample of the corner station PSL beam, delivered via single mode optical fiber. The ALS 1064 nm beam is heterodyned with this PSL light, and the ALS laser frequency is controlled to stabilize it to this (80 MHz) beat signal; the ALS laser is thus offset-locked to the PSL.
3) Sample beam of the arm cavity transmitted 1064 nm light. The IR beam that is transmitted by the ETM goes to the Transmission Monitor. There it is split between an in-vacuum path (TransMon), and this beam that comes out onto ISTEnd. The beam is used for power monitoring and triggering during lock acquisition. In low noise operation of the interferometer, this beam is blocked on the TransMon by a beam diverter.
4) A fraction of the ALS 532 nm beam that is reflected by the ETM is directed to a Hartmann Wavefront Sensor. This is part of TCS, and is designed to measure optical distortion produced by cavity beam absorption in the ETM HR coating.
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