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#weekendusers The coolest high-energy synchrotron experiment


A French team of researchers has created and tested a cryostat where scientists can carry out the coldest experiments in the high-energy range in a synchrotron.

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A photocopy of a drawing lies on the table of the control cabin of beamline ID12. It shows a cryostat and its heart: a spring-like metal tube and other components. Next to the drawing, lots of scribbles in different colours and on different dates, proof that this creation has been many years in the making. Steps away from the table, the real thing makes its appearance in the experimental hutch. Its majestic presence gives the beamline a new touch. It is the Très Basses Temperatures for miliKelvin (TBT-mK) cryostat.

Philippe Sainctavit, from the Institut de minéralogie, de physique des matériaux et de cosmochimie, together with Jean-Paul Kappler and Loïc Joly, from the Institut de Physique et Chimie des Matériaux de Strasbourg and synchrotron SOLEIL, are the fathers of this invention. “We started working on this project 20 years ago, and this is the third version of the machine”, explains Kappler. The team has installed the machine on ID12 for their experiments in magnetism. “Because this is quite a particular piece of equipment, we needed a very strong understanding with the beamline staff. Thanks to the fact that we were all in the same wavelength, the installation, which lasted 5 weeks spread throughout the year, went very smoothly. We could not have done this without the strong collaboration with the ID12 staff, namely Andrei Rogalev, Fabrice Wilhelm and Pascal Voisin”, explains Sainctavit. 

The TBT-mK reaches very low temperatures and it is used in synchrotron sources. At the ESRF they have just managed to carry out high-energy experiments in magnetism at a temperature as low as 0.5 Kelvins  (-272.65 Celsius). This is the lowest temperatures ever reached in a high-energy synchrotron. The team has another of their creations installed on the beamline DEIMOS at the synchrotron SOLEIL, where they also reach freezing temperatures but their experiments are dealing in the soft X-rays energy range. As comparison, these temperatures are slightly lower than one  found in the Boomerang Nebula, which is the coldest known object in the universe and shines about 5000 light-years from the Earth.

Scientists use this cryostat to carry out experiments in magnetism and using materials that exhibit certain characteristics at very low temperatures. The extreme temperature of the cryostat acts as if it multiplies the magnetic field by a factor of 4 during the experiments. At the ESRF, the team has successfully tested the machine by studying the building blocks for molecular magnets, whose properties appear at temperatures below 1 Kelvin. These materials are thought to become the building blocks of the next generation of computers. The samples were prepared by scientists of the Technical University of Denmark and the Centre de Recherche Paul Pascal (CNRS), in Bordeaux.

For now, the TBT-mK will stay at the ESRF: “We would like the cryostat to be useful for all the scientific community”, says Sainctavit. “It is very exciting to have this new instrument, which is fruit of a longstanding collaboration and which will be available to any user needing it from now on”, says Andrei Rogalev, scientist in charge of beamline ID12.

Text and video editing by Montserrat Capellas Espuny. Video images by Chantal Argoud.

Top image: The sketch of the TBT-mk. Credit: J.P. Kappler and P. Sainctavit