Suspension springs

In this section, we will discuss vibration isolation systems based on suspension springs with eddy-current damping. To date, it is probably the most efficient vibration isolation system. The design and choice of springs are also discussed. An elementary theory of helical springs, sufficient for all the applications in STM and AFM, is presented in Appendix F. 

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To achieve atomic resolution, vibration isolation is essential. There are two ways to achieve a suitable solution. The first is to make the STM unit as rigid as possible. The second is to reduce the transmission of environmental vibration to the STM unit. A commonly used vibration isolation system consists of a set of suspension springs and a damping mechanism. 

It is clear that the lower the natural frequency wo is, the better the vibration isolation. The natural frequency is the prime parameter of a vibration isolation system. In a realistic STM system, the reduction of natural frequency is not unlimited. If a suspension spring is used, the elongation of the suspension spring with stiffness k due to the weight of the mass M is... 

To make a suspension-spring system with a natural frequency of 1 Hz, the weight of the mass should stretched the spring by 25 cm. Notice that Eq. (10.23) is exactly the formula for the natural frequency of a simple pendulum with length AL. To isolate the horizontal vibration, a pendulum is the... 

The suspension-spring vibration isolation system has a disadvantage It is large. Gerber et al. (1985) developed a vibration isolation system using a stack of metal plates separated by rubber pieces. It was first used in the pocket-size STM, which will be described in Section 13.1. By increasing the number of metal plates, reasonably good vibration isolation can be achieved in a modest space (see Fig. 10.8). 

Hz because of its small size. The isolation is effective only for vibrations with relatively high frequencies (>50 Hz). To suppress the low-frequency vibrations, an additional suspension-spring stage is needed. 

Even with the foot, the vibration problem in such STM designs has not been resolved sufficiently. In fact, the tripod scanner has a relatively low natural vibration frequency, and the approaching mechanism is relatively bulky. In actual application, a four to-six element metal-plate stack with viton separators is used for vibration isolation. In order to achieve atomic resolution, a spring stage, either suspension spring or compression spring, is neces-... 

Surface structure determination 325—331 Suspension springs 244—248 Takayanagi model See DAS model Tamm states... 

Fig. 8.25. Integration of stiff active mounts into car suspensions a integration into Me Pherson front suspension, b design example for rear suspension spring mounting...

Fig. 15.6 a Hydrogen embrittlement corrosion crack initiated from a pit in high strength steel for suspension spring, b SEM intergranular appearance of the corrosion area... 

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