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Design and verification of low temperature parts of UHV SEM/SPM stage
Pola, Tomáš ; Vlček, Ivan (referee) ; Urban, Pavel (advisor)
This thesis focuses on experimental verification and experimental-based improvements of designed low temperature parts of stage of the UHV SEM/SPM microscope, which operates in temperature range from 20 K to 700 K. The main focus is on the functionality verification of thermal insulation pad (InBallPad) as well as on the effect of length and contact quality of braid on minimal achievable temperature. The contact quality of sample holder with sample carrier realized with two springs is investigated together with influence of thermal contact resistances on achievable temperature. The thesis also contains a calculation model used for cooldown times and minimal temperature estimation. In the conclusion of this work several future experiments are suggested which could explain some of the observed, yet unexpected, phenomena.
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Design of a sample holder with electrical contacts for UHV SEM/SPM
Krutil, Vojtěch ; Vlček, Ivan (referee) ; Urban, Pavel (advisor)
The presented thesis focuses on designing a sample holder for an UHV SEM/SPM microscope suitable for using in low temperature (20 K - 300 K) applications. This newly designed sample holder is equipped with ten spring-loaded contacts for electrical connection of a transport pallet to the sample holder, which will be equipped with a temperature sensor and a heating element. Two quadruples of contacts are reserved for the sample and the temperature sensor and the remaining pair for the heating element. A thorough research study of commercially available sample holders indicates that the holders for the intended use are not available on the market. In the low-temperature tests of the newly designed sample holder, the limit temperature of the 24 K was reached in a test vacuum chamber with a flow cooling system. The ambient temperature was 300 K. The contact function was successfully verified by measuring the transient electrical resistance at the fixed and the spring contact sections. Additionally, a modification of the sample holder for high temperature (300 K - 700 K) was suggested.
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Cryogenic cell for study of water ice in ESEM microscope
Krutil, Vojtěch ; Kubíček, Jaroslav (referee) ; Urban, Pavel (advisor)
The presented thesis focuses on designing a cryogenic cell for the study of water ice in an environmental scanning electron microscope (ESEM). This cell allows the study ice in the temperature range 80 K – 300 K in a nitrogen gas environment with a pressure of up to 400 Pa. The cell is cooled by a flow cooling system, where liquid or gaseous nitrogen is used as a refrigerant. The cell consists of a double-walled vessel with vacuum insulation, a flow-through heat exchanger, a sample well, and a cooled cell lid. The heat exchanger was designed to be able to dissipate the heat load at the level of 1 W. The exchanger is equipped with an electric resistance heater with an output of approximately 60 W, enabling heating of the sample at speeds of up to 100 K·min-1. The design also includes an LN2 gateway located on the door of the vacuum chamber of the microscope, to which the capillaries of the heat exchanger for the intake and outlet of refrigerant are connected. During the experimental verification of the cryogenic cell in the test vacuum chamber with a pressure of GN2 ~ 400 Pa, the limit temperature of 77.5 K on the sample well was reached.
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Cryogenic cell for study of water ice in ESEM microscope
Krutil, Vojtěch ; Kubíček, Jaroslav (referee) ; Urban, Pavel (advisor)
The presented thesis focuses on designing a cryogenic cell for the study of water ice in an environmental scanning electron microscope (ESEM). This cell allows the study ice in the temperature range 80 K – 300 K in a nitrogen gas environment with a pressure of up to 400 Pa. The cell is cooled by a flow cooling system, where liquid or gaseous nitrogen is used as a refrigerant. The cell consists of a double-walled vessel with vacuum insulation, a flow-through heat exchanger, a sample well, and a cooled cell lid. The heat exchanger was designed to be able to dissipate the heat load at the level of 1 W. The exchanger is equipped with an electric resistance heater with an output of approximately 60 W, enabling heating of the sample at speeds of up to 100 K·min-1. The design also includes an LN2 gateway located on the door of the vacuum chamber of the microscope, to which the capillaries of the heat exchanger for the intake and outlet of refrigerant are connected. During the experimental verification of the cryogenic cell in the test vacuum chamber with a pressure of GN2 ~ 400 Pa, the limit temperature of 77.5 K on the sample well was reached.
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Design of a sample holder with electrical contacts for UHV SEM/SPM
Krutil, Vojtěch ; Vlček, Ivan (referee) ; Urban, Pavel (advisor)
The presented thesis focuses on designing a sample holder for an UHV SEM/SPM microscope suitable for using in low temperature (20 K - 300 K) applications. This newly designed sample holder is equipped with ten spring-loaded contacts for electrical connection of a transport pallet to the sample holder, which will be equipped with a temperature sensor and a heating element. Two quadruples of contacts are reserved for the sample and the temperature sensor and the remaining pair for the heating element. A thorough research study of commercially available sample holders indicates that the holders for the intended use are not available on the market. In the low-temperature tests of the newly designed sample holder, the limit temperature of the 24 K was reached in a test vacuum chamber with a flow cooling system. The ambient temperature was 300 K. The contact function was successfully verified by measuring the transient electrical resistance at the fixed and the spring contact sections. Additionally, a modification of the sample holder for high temperature (300 K - 700 K) was suggested.
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Design and verification of low temperature parts of UHV SEM/SPM stage
Pola, Tomáš ; Vlček, Ivan (referee) ; Urban, Pavel (advisor)
This thesis focuses on experimental verification and experimental-based improvements of designed low temperature parts of stage of the UHV SEM/SPM microscope, which operates in temperature range from 20 K to 700 K. The main focus is on the functionality verification of thermal insulation pad (InBallPad) as well as on the effect of length and contact quality of braid on minimal achievable temperature. The contact quality of sample holder with sample carrier realized with two springs is investigated together with influence of thermal contact resistances on achievable temperature. The thesis also contains a calculation model used for cooldown times and minimal temperature estimation. In the conclusion of this work several future experiments are suggested which could explain some of the observed, yet unexpected, phenomena.
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