Extreme Vibration Attenuation
The Micro-G is a Cryogenic Vibration Attenuation System designed based on the LIGO/KAGRA Seismic Attenuation System (SAS) of gravitational wave detectors. The system can be incorporated into a cryostat which includes:
- Low vibration Pulse-Tube (PT) cryocooler mounted to rigid support structure. The rigid structure is mounted to the lab floor or lab ceiling. The pulse tube cooler requires a water circulating chiller.
- Temperature controller with heaters and thermometers on all relevant temperature stages for experimental control, monitoring, and system diagnostics.
- Roughing pump, turbo pump, vacuum gauge and respective controllers for vacuum system control and monitoring. Cryo adsorber pumps included inside vacuum chamber and cold spaces.
- 4K and 40K radiation shields. These shields are rigid with respect to the vacuum chamber (no vibration isolation) and optimized for good thermal conduction to the cryocooler. The floating cold platform for the cryogenic cavity is suspended inside the 4K shield through small openings in the top of the rigid shields. The only mechanical contact made between the rigid shields and floating plates is the soft, high thermal conductivity straps connecting the 4K/40K floating plates to the 4K/40K shields, respectively. These thermal links are user configurable as experimental needs evolve.
- One Inverted Pendulum (IP) isolation stage for horizontal (XYΘ) vibration attenuation. This stage is designed for future additions such as: eddy current damping or closed-loop (3 mode) position control.
- Three Geometric Anti-Spring (GAS) filter stages for vertical (Z) vibration attenuation. Each GAS filter includes a coarse mass compensating scheme for large user payload changes. Each stage is integrated with an auto level voice coil and position sensor for fine mass and micron positional drift compensation. Space is available for future integration of a third filter.
- Large vacuum chamber, roughly 28"x28"x30", constructed with large side access doors and all necessary viewports and feedthrough ports.
System Specifications:
- < 4K Base Temperature on floating sample plate
- Available user payload configurability: 0-1kg
- 50-60dB of isolation @ 100Hz / per single GAS filter
- < 1E-6 g/rtHz
- 30cm x 30cm x 50cm cold space volume
Micro-G Stand-alone Module
The Micro-G vibration attenuation module may be applied equally well to room temperature systems. It attenuates mechanical noise by a factor of 1,000-10,000 for important frequencies over 5 Hz.
The graph above shows the system transmissibility of a single filter versus frequency. Attenuations are greater than 1000:1 for frequencies over 5 Hz. When multiple filters are used, their performance is superimposed.