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Transport properties

Transport properties

Flash Physics: Diamond-defect FM-radio tunes in, Slovenia joins CERN, first plasma for WEST tokamak

21 Dec 2016 Hamish Johnston

Flash Physics is our daily pick of the latest need-to-know developments from the global physics community selected by Physics World's team of editors and reporters

Diamond FM: receiver uses nitrogen vacancies

Tiny radio is based on diamond defects

A radio receiver based on atomic-scale defects in diamond has been unveiled by physicists at Harvard University in the US and Element Six in the UK. The device uses nitrogen vacancies (NVs) in which two adjacent carbon atoms in a diamond crystal are replaced by a nitrogen atom and an empty lattice site. NVs are useful because they have an electronic spin that is extremely well isolated from the surrounding lattice. An NV will also emit fluorescent light when excited by a laser – and together these properties make NVs very attractive to physicists trying to build quantum computers. To create their receiver, Harvard’s Marko Loncar and colleagues use a green laser to “pump” a collection of NVs into an excited energy state. When a pumped NV is subjected to radio waves, it emits red light, which is then captured by a photodetector and converted into an electrical signal. The system was able to receive a frequency-modulated (FM) signal on a carrier frequency of 2.8 GHz. The receiver could be tuned over a frequency range of 300 MHz by applying an external magnetic field to the NV spins. The team says that “high-quality” audio signals at frequencies up to 91 kHz can be received by its radio. While the team used billions of NVs to create its device, a receiver based on just one NV would emit just one photon at a time – and could be used to convert quantum information from radio frequencies to visible light. Because diamond is a very tough material, Loncar says: “This radio would be able to operate in space, in harsh environments and even the human body, as diamonds are biocompatible.” The receiver is described in Physical Review Applied.

Slovenia moves towards full membership of CERN

CERN’s council has voted unanimously to admit Slovenia as an “associate member in the pre-stage to full membership” of the particle-physics lab in Geneva. The move means that the Balkan nation will be able to apply for full membership of CERN in five years. Slovenia applied to be a member of CERN in 2009, and the nation’s physicists have been contributing to CERN long before the country became an independent state in 1991. Slovenian physicists currently work on the ATLAS experiment on the Large Hadron Collider (LHC) and the country hosts a tier-2 data centre for processing data from the LHC. “Slovenia’s membership in CERN will on the one hand facilitate, strengthen and broaden participation and activities of Slovenian scientists (especially in the field of experimental physics), on the other it will bring full access of Slovenian industry to CERN orders, which will help to break through in demanding markets with products with a high degree of embedded knowledge,” says Maja Makovec Brenčič, Slovenian minister of education, science and sport.

First plasma for WEST tokamak in France

The WEST tokamak in Cadarache, France, has confined its first plasma. The facility is a refurbishment of the Tore Supra tokamak, and is designed to test “divertor” technology that is being created for the ITER fusion reactor – which is currently being built at Cadarache. The divertor will sit on the floor of the ITER vacuum vessel and will remove the helium “ash” that is created when hydrogen nuclei fuse in the reactor. The divertor must be able to withstand high fluxes of both heat and particles from ITER’s plasma, which will be heated to several million degrees. The plasma-facing portion of the divertor will be made from thousands of tungsten tiles and WEST will test the performance of different divertor designs under plasma operating conditions. Scientists will also be able to quantify how the divertor will age and be damaged in the harsh plasma environment. Scheduled for completion in 2025, ITER is a collaboration involving China, the EU, India, Japan, Russia, South Korea and the US that aims to demonstrate that nuclear fusion can generate useful energy.

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