Next Generation Fast Shutter System for LIGO

Abstract

The proposal for the next generation Fast Shutter system intended to replace the current electromagnetic system used to block an optical pulse that is part of the LIGO observational setup is presented and discussed. The current system setup, problems solved with the new setup, and experiments guiding the new proposal design are detailed along with future work remaining to verify the operation of the next generation Fast Shutter system before it is used in LIGO s observatories. This system is an electro-mechanical device consisting of two coils of electrically conducting wires and a payload made up of two magnets of opposite polarity configured to move between the upper and lower parts of the device. The mirror is attached to the magnet payload and is used to reflect optical pulses. When a current is applied to the coils, the magnets and attached mirror can move vertically relative to the coils due to the Lorentz force from the current in the coils acting on the magnets. The system can be operated in air or in a vacuum environment over a wide range of temperature and cleanliness requirements. This system offers a novel and robust solution compared to LIGO s previously patented electro-magnetic ultra-fast shutter due to the design of a moving payload consisting of magnets and a mirror with no wires attached, compared to the prior design consisting of a moving coil requiring electrical attachment. As a result, this system avoids the failure mode associated with wire fatigue caused by repeated flexure of the coil attachment wires. With stationary coils, this system uses permanent magnets for the upward propulsion of the payload. Eddy current damping provided by copper interacting with the payload magnets is included to damp the oscillatory transient response of the payload. This newly designed system achieves the same critical performance specifications as the previously patented ultra-fast mechanical shutter, while being physically smaller, cheaper to build, and vastly more reliable.