Master of Science in Mechanical Engineering, Physics or Electrical Engineering

Karlsruher Institut für Technologie
January 24, 2023
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together unique

Organizational unit

Institute of Microstructure Technology (IMT)

Job description

Cryo-coolers are versatile systems for different scientific and industrial applications, ranging from sample preparation in biology and medicine to application of sensors in science and industry. For these objectives, pulsed tube coolers (PTC) have been experimentally investigated. Sensors can be cooled down to very low temperatures as well as the samples can. Signal over noise ratio can be reduced, and sensitivity of the whole analytical system can thus be increased significantly. This could allow enhanced infrared and other optical sensors as well as micro nuclear magnetic resonance systems applying supercooled coils for high magnetic fields in very small devices.

In the last decades, miniaturization has been at the centre of many research and development fields. Scaling to mini, micro or even nano scales allows integration of a multitude of specific functionalities into a single device, or improves the performances of devices (i.e. time or spatial resolution of sensor devices, sometimes by orders of magnitude). This holds also for systems running at cryogenic temperatures, namely analytical devices. Cooling such systems with liquefied gases kept in well-insulated large volumes is feasible for non-portable applications. To allow mobility and, therefore, more flexibility of, e.g., measurement equipment, miniaturization is targeted. Here, proper insulation and transport of liquefied gas volume vessels is not feasible due to the dangers associated to cryo temperature liquids. Other techniques, among which PTCC systems, have to be explored and implemented into miniaturized systems. All PTCC need a compressor, which causes vibrations transferred by the tubing into the system. For macro scale devices this is not much of a problem, because damping arrangements can be implemented, cutting off the vibrations. This changes when the system dimensions are scaled down to the microscale. Due to the decrease of dimensions, vibrational distortion cannot be settled with any regular known countermeasures anymore. This is especially true for miniaturized measurement and sensing systems, in which the spatial resolution is in the range of some µm or below, and the time resolution is in the µs or even ns range. Thus, the implemented compressor has to work without moving parts, generating neither friction nor vibrations in any way.

Knudsen pumps are versatile tools for generation of gas movements by thermal transpiration obtained by temperature differences only. A mass flow is obtained from a cold to a hot region when their connecting channel is small enough. By combining in a cascade system several hot and cold spots with alternatively small and large channels, a net mass flow is generated and a significant pressure difference between inlet and outlet can be reached.

The objective of this PhD topic is to develop, construct and optimise a tunable modular micro cryo cooling system, based on a micro pulsed tube cryo cooler, to be combined with a miniaturised Knudsen pump developed within the same project but by another researcher. By combining with micro heat exchangers as regenerators and heat transfer parts, very versatile systems can be obtained. A tunable design of the miniaturized PTCC will provide additional benefit, because the efficiency of the system can be adjusted to the desired application. The pulse frequency has to be controlled, and the tube length should be adjusted.

You will be working in a French-German joint project between the Institute of Microstructure Technology IMT at the Karlsruhe Institute of Technology KIT and the Institut Clément Ader, Toulouse. Your working place will be at KIOT, but shorter visits to the partner organization are foreseen.

Starting date Personal qualification
  • M.Sc. in Mechanical Engineering, Physics, or Electrical Engineering
  • Enthusiastic to work in a highly interdisciplinary environment
  • Experience in at least three of the following: microfluidic design and fabrication, heat transfer and thermal management, thermodynamics, cryo temperature systems, low temperature measurement and control
  • Working in teams
  • Language competence in English (and German, if possible)
  • Salary

    Salary category 13, depending on the fulfillment of professional and personal requirements.

    Contract duration

    3 years

    Application up to

    31.01.2023

    Contact person in line-management

    For further information, please contact Prof. Dr. Jürgen Brandner, juergen.brandner@kit.edu.

    Please apply online using the button below for this vacancy number 830/2022.

    Ausschreibungsnummer: 830/2022

    We prefer to balance the number of employees (f/m/d). Therefore we kindly ask female applicants to apply for this job. Recognized severely disabled persons will be preferred if they are equally qualified.

    Contact

    Personnel Support is provided by: Personalservice (PSE) - Human Resources Ms Gätcke Phone: +49 721 608-25010,

    Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany

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