L-TYPE RAPID w. 55 mm puck and magnet

The Niels Bohr Institute is part of the Faculty of SCIENCE at the University of Copenhagen. The Niels Bohr Institute has a 100 year long tradition of excellence within science, in particular within the area of quantum physics. The institute was inaugurated on March 3, 1921, by Professor Niels Bohr. We are approx. 430 researchers, 70 administrative and technical staff, 100 PhD students and 400 students. The European Physical Society has declared the Niels Bohr Institute a Historic Site of great international importance for the development of physics and research.

We are looking to buy a dual-ADR refrigerator. It is a versatile system for cooling down sample all the way to 100 mK within 4 hours. Besides the two ADR magnets, it also has a third sample magnet up to 4 tesla. Such a tool will be essential for fast electrical characterization of the novel materials we plan to develop at NQCP. The system will simultaneously be used for teaching purposes, for which the fast cool down time is essential.

The following is crucial for our choice of cryostat for quick electrical characterization and teaching:

The cryostat must be able to maintain 300 mK and reach and hold 100 mK for >3 hour, to see certain physical phenomena.

We will be looking at low critical temperature superconductors like Al, as well as quantum phenomena like quantum point contact steps, quantum dots, and fractional quantum Hall effect where thermal broadening can blur the effects making them unmeasurable. For long scans, it is essential to maintain a constant temperature below 500 mK for many hours or days. Certain measurements require a temperature of 100 mK.

Must support temperature sweeps from base up to 200 K.

Temperature dependence of measurable quantities are need to extract certain material parameters. Therefore temperature sweeps from base up to 200 K are essential.

DC + RF in the same system

Some of our characterization tests will need a combination of DC and RF measurements making it essential to have options both available in the same cool down. To enable simultaneous cooldown of multiple devices on the same chip we want 48 or more DC lines and 4 or more RF lines.

Integrated filters for low electron temperatures

Besides the sample stage, our electrons also need to be cold for our experiments. Filters like the RF+RC QFilters are essential for all DC lines. Without proper filtering, the electrons will be much hotter than the measured stage temperatures.

Fast cooldown times below 4 hours.

We need a system that you can cool down in the morning and then have it at base in the afternoon. This allows a fast feedback loop for our characterization efforts which will be crucial for our material development efforts. Also, for teaching purposes, this allows students to experience loading, cooldown and measurements in a single day.

Magnetic fields of 4 tesla or more

Some of our experiments, like quantum Hall, will require multiple tesla applied perpendicular to our samples

ADR refrigeration is required.

We want to teach our students about ADR refrigeration, for which seeing and controlling the field and temperature curves in real life is an ideal learning experience.

Cross compatibility with QBoards

We aim to have all measurement setups using QBoards. This allows transfer of samples to different measurement setups without having to rewire. Rewiring can destroy devices and should therefore be avoided whenever possible.

If any of the above is unclear, then we can supply additional information.