Graphene-based resistance standard (GRS)
Graphene makes it possible to observe the quantum Hall effect at relatively low magnetic fields and high temperatures. By utilising this possibility, Graphensic has developed a graphene-based resistance standard, the GRS.
The GRS is equipped with a superconducting magnet and comes with a graphene-based QHE chip. It is designed to operate together with a measurement bridge and utilises a liquid helium storage dewar for refrigeration. By utilising graphene, the GRS simplifies the process of conducting on-site comparisons of the quantum Hall effect resistance standard.
The GRS offers flexibility for your measurement system and the operating level can be adjusted to make it operate with liquid helium dewars of different sizes. This ability also allows for slow cooling the product during insertion, lowering the overall helium consumption. It is an easy and fast process to cool the GRS to the right temperature and it does not require a VTI.
To make it possible to conduct other types of measurements in the magnetic field, the GRS has a removable inner probe. The accompanying sample probe and superconducting magnet can be configured to fit specific needs. It is possible to compliment the GRS with extra equipment such as a liquid helium level meter.
We offer a baseline design that accommodates the needs for resistance calibrations.
The connection between the GRS and the storage dewar is a ISO KF50 to quick connect coupling. This makes it possible to adjust the operating level for the GRS to work with 60 l and 100 l storage dewars. The interface for the sample probe utilises the ISO KF25 standard. The support structure is made of stainless steel (AISI 304).
A superconducting magnet with 5 T field strength. This operates at 45 A, has an inductance of 1.1 H and a homogeneity of +/-0.05% over a 1 cm DSV. The GRS has a persistent mode switch installed. This enables the possibility to run the magnet without a current feed once it is charged, decreasing the liquid helium consumption. In static mode, the GRS consumes approximately 0.2 l of liquid helium per hour.
The GRS comes with a graphene-based QHE chip that has a total of 10 Hall bars intended for resistance calibrations. Since the graphene is made by sublimation of silicon carbide, the chip is of high quality and will offer accurate measurements. It is mounted on and bonded to a TO-8 header.