The proposal of novel design of temperature control system for scanning tunneling microscope: The closed surface capsule

This article describes the design of temperature control system for a scanning tunneling microscope using a spherical closed surface capsule. To verify the advantage of the structure of the spherical closed surface capsule, the preliminary simulation and experiment are performed. Both simulation result and experimental result show that transfer functions of the capsule can be estimated as the of first order systems. The characteristic of transfer functions are analyzed to verify the performance of the temperature control system against the existence of an external disturbance temperature and an internal disturbance temperature. The simulation results show that the large time constant of transfer function has an advantage to isolate the system against the external disturbance in ambient environment very well. However, robustness of the temperature control system against the internal disturbance temperature is reverse to the time constant of a heat exchanging process. We believe that the temperature control system for a scanning tunneling microscope using the closed surface capsule with the fluctuation of temperature in the level of 0.01degC over the period of 1 hour can be constructed by redesigning of the structure of a spherical closed surface capsule based on the result of these preliminary experiments.