Ultra-Low Vibration Laboratory based on a Cylindrical Inertia Block

Scanning tunneling microscopy (STM) is exponentially sensitive to vibrational and acoustic noise that perturb the tip-sample distance. Low vibration facilities employing massive inertial blocks and pneumatic isolators can mitigate this effect. We describe a new low-vibration facility at Harvard University that employs a cylindrical, rather than prismatic block, to minimize the coupling of acoustic standing waves between the straight walls and the curved block face. Here, we apply a frequency chirp to a speaker and use a movable microphone to measure the acoustic response throughout the room, to map out the spatial eigenmodes. We also use an accelerometer to measure the vibration response of the cylinder. To support this measurement, we use COMSOL Multiphysics to simulate the response of the cylindrical block to the acoustic standing waves in the room.