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SMV-2023-52: Full servis of Dewar vessels for liquid helium
Srnka, Aleš ; Krejčí, Pavel
The goal of the research is optimalization of operation of Dewar vessels with economical profitability and security during permanent changes of operating conditions. All important data are tracked for a long time and using is optimalized to achieve the smallest loses. We use long time know-how in the field of cryogenics and our specialized cryogenics equipments and apparatuses.
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Design of a nitrogen Dewar vessel for electron microscopes
Brauner, Tomáš ; Voňka,, Jakub (referee) ; Urban, Pavel (advisor)
Observation of biological samples in electron microscopes in a state closest to the native state requires reaching cryogenic temperatures, most often with the use of liquid nitrogen (LN2). For this purpose a Dewar vessel with cooled copper thumb for cooling the sample holder and anticontamination shield inside the vacuum chamber of the scanning electron microscope (SEM) and focused ion beam (FIB) source was designed. Characteristics of the designed LN2 Dewar vessel were validated by measuring executed on the real functional sample. The reached temperature at the tip of the thumb under estimated heat load 2 W was 90,8 K. Corresponding refilling interval of LN2 is about 11 h. Experimentally measured data correlate with theoretically calculated characteristics. The designed Dewar vessel with a cooled thumb fulfills the required properties specified in the thesis assignment with a margin.
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SMV-2022-58: Full servis of Dewar vessels for liquid helium
Srnka, Aleš ; Krejčí, Pavel
Long-term active operation of Dewar vessels for liquid helium is economically exacting. The goal of the research is optimalization of operation with economical profitability and security during permanent change of input and output data. All important data are tracked for a long time and use is optimalized to achieve smallest loses. We use long time know-how in the field of cryogenics and our specialized cryogenics equipments and apparatuses. The research is conducted according Contract between MU - CEITEC and ÚPT AV ČR Brno, v. v. i., signed on the 20. 1. 2022.
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SMV-2021-61: Professional servis of Dewar vessels for LHe
Srnka, Aleš
Long-term active operation of Dewar vessels for liquid helium is connected with the risk of their damage that could caused significant financial losses and as well danger for their operators. The goal of the research is to guarantee the safe operation and its economical benefit. Vessels are periodically tested for vacuum tightness and relevant boil of rate is measured. Simultaneously are tested security valves and cooling processes of vessels are optimized. We use long time know-how in the field of cryogenics and also our specialized cryogenics equipments and apparatuses. The research is conducted according Contract between MU - CEITEC and ÚPT AV ČR Brno, v. v. i., signed on the 3.2.2020.
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SMV-2020-40: Professional servis of Dewar vessels for LHe
Srnka, Aleš
Long-term active operation of Dewar vessels for liquid helium is connected with the risk of their damage that could caused significant financial losses and as well danger for their operators. The goal of the research is to guarantee the safe operation and its economical benefit. Vessels are periodically tested for vacuum tightness and relevant boil of rate is measured. Simultaneously are tested security valves and cooling processes of vessels are optimized. We use long time know-how in the field of cryogenics and also our specialized cryogenics equipments and apparatuses. The research is conducted according Contract between MU - CEITEC and ÚPT AV ČR Brno, v.v.i., signed on the 3.2.2020. \n
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SMV-2019-29: Professional servis of Dewar vessels for LHe
Srnka, Aleš
The aim of the project is optimalization of the operation of Dewar vessels for liquid helium with\naccent to the safe operation and its economical benefit. Vessels are periodically tested for vacuum tightness and relevant boil of rate is measured. Simultaneously are tested security valves and cooling processes of vessels are optimized. We use long time know-how in the field of cryogenics and also our specialized cryogenics equipments and apparatuses. The research is conducted according Contract between MU - CEITEC and ÚPT AV ČR Brno, v.v.i., signed on the 17.1.2019. \n
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SMV-2019-76: Maintenance and commissioning of liquid nitrogen Dewar vessel
Králík, Tomáš
The contractor needs a handy storage of liquid nitrogen for some analytical apparatuses in his laboratory. The contractor decided to utilize an older LN2 Dewar vessel with unknown state of its insulation and evaporation rate. A professional commissioning of a Dewar vessel need special know how and specialised equipment. It was done cleaning of the pumping valve of the vessel from old and hardened sealing grease, change of the O-ring sealing, visual check of the insulation inside the vessel, application of new silicone grease on the pumping valve plug, pumping out of the vacuum space and its outgassing, leak test with a helium leak detector, closing of the pumping valve and its filling with silicon grease, cool down and filling with the liquid nitrogen, long term measurement of the evaporation rate. The measured evaporation rate is 0.3 litres per day and the time of the cold state of the Dewar vessel is nearly hundred days.
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SMV-2014-14: Baffle plates for the 75 mm neck of the helium Dewar CH-500
Srnka, Aleš
Research and development in the field of thermal shielding of cryogenic vessels. It included selection of material with suitable emisivity and absorptivity of thermal radiation, analysis of cryogenic vessel from the point of parasitic thermal fluxes and calculation of baffles quantity and position in the vessel neck. Experimental tests proved rightness of calculation and showed that only by use of properly designed baffles it is possible to reach minimal helium evaporation rate.
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