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How to meet strict floor vibration criteria requirements in a very noisy environment? – TMC’s LaserTable-Base project at IFW Dresden

Introduction

The renowned scientist, Dr. Aliaksei Charnukha has been awarded a prestigious German national Emmy Noether Starting Grant funded by the German Research Foundation (DFG) in the amount of €2.3 million for a period of five years to establish an Independent Junior Research Group at the Leibniz Institute for Solid State and Materials Research (IFW) in Dresden. His group will investigate equilibrium and dynamic emergent phenomena in quantum matter using cryogenic nano-optical microscopy and spectroscopy. The aim of the project is to build a spectroscopic, low-energy and low-temperature, ultrafast optical probe with nanometer scale spatial resolution. The research will be conducted at cryogenic temperatures down to 1.6 K and attain a spatial resolution under 5 nm. When Aliaksei contacted TMC, the severe floor vibration caused by the heavy traffic in Dresden was the main obstacle to start his experiments. His nano-optical instruments are vibration sensitive and require a quiet research space, which meets the VC-E to F vibration criteria*. Aliaksei and his group needed a compact vibration cancellation solution, which reduces floor vibration effectively in all six degrees of freedom. It had to start isolating at very low frequencies but had to be able to achieve an outstanding vibration cancellation performance in the 10-12 Hz range. The solution was TMC’s LaserTable-Base.

How LaserTable-Base works

LaserTable-Base offers an extraordinary level of improvement over existing technology in the amount of vibration isolation attainable with an optical table. Typically, optical tables are supported by low-frequency pneumatic vibration isolation systems. Though very effective at isolating higher frequencies, these passive systems actually amplify vibration in the critical 1 to 3 Hz range due to their own natural resonance.

TMC STACIS technology overcomes these limitations through proprietary technology which incorporates piezoelectric actuators and inertial vibration sensors to cancel, not amplify, very low frequency vibration. LaserTable-Base combines these two technologies, air and STACIS, into one integrated cancellation system. The result is vibration cancellation at very low frequencies and unprecedented levels of high frequency isolation due to the combined effect of two isolation systems in series.

The upper, pneumatic portion of LaserTable-Base is modular and interchangeable. It can incorporate TMC's Gimbal Piston or MaxDamp air isolators, or rigid, non-isolating supports, depending on the application requirement. Due to the high center of gravity, the system for Dr. Charnukha uses a LaserTable-Base with MaxDamp isolators.

Combining the low frequency, passive MaxDamp air isolators with a piezoelectric active vibration cancellation system in series results in an overall transmissibility curve that is the sum of the two individual transmissibility curves. The resultant vibration isolation performance is so dramatic that over some frequency ranges, we are limited by measurement instrumentation noise, and unable to measure and demonstrate full isolation performance. That is, above 10-12 Hz, the actual performance of the combined system is expected to exceed that shown since the combined isolation is theoretically the sum of the isolation provided by the two sub-systems. See the transmissibility curves on the LaserTable-Base page.

After measuring the building’s vibration levels and comparing them with LaserTable-Base’s reduction factors (see image below), it was clear that LaserTable-Base provides the only possible solution.

Estimated vibration reduction factors of LaserTable-Base

LaserTable-Base’s configuration is always tailored for the specific application: both the table-top sizes, the height of the system, and the material (non-magnetic, cleanroom compatible, vacuum compatible etc.) are adjusted to our customers’ needs. After the production of the system the next big steps were setup and the installation.

The physical assembly and installation process of LaserTable-Base at IFW Dresden

The typical installation of a LaserTable-Base system consists of three stages:

  • LaserTable-Base’s physical assembly at the point of use
  • Installation of the customer’s instruments on the table-top
  • IOC = Initialization, Optimization, and Certification of the vibration isolation system

Stage 1 and 3 are performed by TMC. TMC’s rigging partner picks up the LaserTable-Base directly from TMC’s Central European warehouse in Bremen, Germany. All components are delivered to the customer site and are brought into the building.

In stage 2 the customer assembles and installs their instruments on the table-top. IOC can be executed only after the whole set-up is ready. We documented the main steps of stage 1 and stage 3.

The system gets uncrated before entering the building. It ensures an easier handling through the narrow corridors in the building.

The system will be placed in the middle of the lab over the white floor platform. The legs are already placed at the correct corners.

The heavy top arrives in the lab.

Our rigging partner needs special lifting equipment for transporting the massive table-top.

Positioning the STACIS isolators and assembling the frame.

Positioning the table legs, which already incorporate the MaxDamp isolators.

Air supply tubing and valve setup.

After placing the table-top, LaserTable-Base is ready for the next stages.

The installation is ready for the IOC (stage 3).

IOC is conducted via LaserTable-Base’s digital controller, DC-2020. The controller features an LCD with push-button operation. This is the secondary user interface.

The system's operation can also be monitored via the controller’s web-based GUI (Graphical User Interface) on a conventional PC. This is the controller's primary user interface that provides a more user-friendly operation. The GUI is accessible via Ethernet or USB interface.

The system is ready for operation. The user can immediately start working on his experiment.

LaserTable-Base sets the standard for hybrid (active and passive) vibration cancellation technology. It combines air and the active STACIS® technology in one integrated cancellation system. Its modular design allows for customizing the air sub-system for specific application requirements.

TMC would like to thank Dr. Aliaksei Charnukha and his team for choosing TMC and we wish them success with their research.

*VC-E to F specification means an extremely quiet research space, with an amplitude of 1.56-3.12 µm/s (62.5-125 µin/s). You can learn more about the Vibration Criteria (VC) curves in this article.


This article was published on LinkedIn on 12/03/2019. Link to original.

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