Zero Kelvin – the temperature known as absolute zero. Since heat is energy, lower temperatures mean less energy, but there is no such thing as negative energy. Expressed in the more familiar temperature scale, zero Kelvin is −273.15 degrees Celsius: nothing can get colder than that. Some researchers at PSI are conducting experiments at temperatures close to absolute zero; others are tinkering with technical means of reducing the temperature as efficiently as possible
Protein sample
Ice crystals can be seen on the tube-shaped sample holder at the end of the robot arm, which has travelled horizontally from the right-hand edge of the image to just in front of the circle of light. The robot automatically retrieves protein samples from a cooling bath of liquid nitrogen and transports them to the experimental position that can be seen, like a needle, opposite the end of the sample holder. The protein crystals are then irradiated with X-ray light from the Swiss Light Source SLS. The three-dimensional structure of the protein can be calculated from the diffraction pattern. This allows researchers to gain insights into the molecular architecture and thus into how the proteins function © Paul Scherrer Institute PSI/Markus Fischer
Ice crystals can be seen on the tube-shaped sample holder at the end of the robot arm, which has travelled horizontally from the right-hand edge of the image to just in front of the circle of light. The robot automatically retrieves protein samples from a cooling bath of liquid nitrogen and transports them to the experimental position that can be seen, like a needle, opposite the end of the sample holder. The protein crystals are then irradiated with X-ray light from the Swiss Light Source SLS. The three-dimensional structure of the protein can be calculated from the diffraction pattern. This allows researchers to gain insights into the molecular architecture and thus into how the proteins function © Paul Scherrer Institute PSI/Markus Fischer
Cold atoms
Green light spreads out from the evacuated experimental chamber. Inside it are the atoms that are to be cooled. The green light comes from a laser and hits the atoms in a precisely synchronised manner. When they absorb the energy of individual light packets, they release a larger amount of energy immediately afterwards – each time becoming even colder than before. The principle is called laser cooling. It brings the atoms close to absolute zero, at −273.15 degrees Celsius. This makes it possible to determine and analyse their quantum nature. At the PSI Center for Photon Science, researchers use this approach to gain new insights in the field of quantum mechanics. © Paul Scherrer Institute PSI/Markus Fischer
Green light spreads out from the evacuated experimental chamber. Inside it are the atoms that are to be cooled. The green light comes from a laser and hits the atoms in a precisely synchronised manner. When they absorb the energy of individual light packets, they release a larger amount of energy immediately afterwards – each time becoming even colder than before. The principle is called laser cooling. It brings the atoms close to absolute zero, at −273.15 degrees Celsius. This makes it possible to determine and analyse their quantum nature. At the PSI Center for Photon Science, researchers use this approach to gain new insights in the field of quantum mechanics. © Paul Scherrer Institute PSI/Markus Fischer
Pulsating heat pipes
These delicate, silvery heat pipes contain a dualphase flow of helium or neon; that means the substances are partly gaseous and partly liquid. The vertical pipes are connected, at their lower end, to a heat source. At their upper end, a condenser is connected to a cryocooler: a refrigeration device that is able to maintain a constant low temperature below −240 degrees Celsius. In this design, known as pulsating heat pipes, the flow of helium or neon leads to an efficient passive heat transfer. Such a thermal connection is a key element for the optimisation of superconducting systems that need to be cooled to low temperatures. The development and implementation of this arrangement is part of the joint efforts of PSI’s magnet section and the company VDL ETG. © Paul Scherrer Institute PSI/Markus Fischer
These delicate, silvery heat pipes contain a dualphase flow of helium or neon; that means the substances are partly gaseous and partly liquid. The vertical pipes are connected, at their lower end, to a heat source. At their upper end, a condenser is connected to a cryocooler: a refrigeration device that is able to maintain a constant low temperature below −240 degrees Celsius. In this design, known as pulsating heat pipes, the flow of helium or neon leads to an efficient passive heat transfer. Such a thermal connection is a key element for the optimisation of superconducting systems that need to be cooled to low temperatures. The development and implementation of this arrangement is part of the joint efforts of PSI’s magnet section and the company VDL ETG. © Paul Scherrer Institute PSI/Markus Fischer
Tissue sections
A cold mist of nitrogen hovers around the interior of a microtome, a cutting device used to produce tissue sections. A diamond knife is mounted in a blue holder. Directly behind the cutting surface of the knife are the very small, frozen tissue samples, which are fixed in a kind of drill chuck. The sample is moved up and down while the knife advances towards the sample, producing ultrathin sections, typically between 50 and 150 nanometres thick. To preserve the sample in its natural state in amorphous ice, it must be very cold: −150 degrees Celsius. In the Laboratory of Biomolecular Research, the ultra-thin tissue samples are used to improve our understanding of physiological processes. From there, new therapeutic possibilities can be explored. © Paul Scherrer Institute PSI/Markus Fischer
A cold mist of nitrogen hovers around the interior of a microtome, a cutting device used to produce tissue sections. A diamond knife is mounted in a blue holder. Directly behind the cutting surface of the knife are the very small, frozen tissue samples, which are fixed in a kind of drill chuck. The sample is moved up and down while the knife advances towards the sample, producing ultrathin sections, typically between 50 and 150 nanometres thick. To preserve the sample in its natural state in amorphous ice, it must be very cold: −150 degrees Celsius. In the Laboratory of Biomolecular Research, the ultra-thin tissue samples are used to improve our understanding of physiological processes. From there, new therapeutic possibilities can be explored. © Paul Scherrer Institute PSI/Markus Fischer
Quantum material
Inside this cryostat – a two-metre refrigeration device that is unique in the world and that achieves temperatures close to absolute zero – is a quantum magnet. Its properties are being studied using light from the X-ray free-electron laser SwissFEL. At very low temperatures around one Kelvin and below, the quantum material assumes a magnetic state that can be directly imaged using X-ray scattering. Here researchers can study, for example, the influence of quantum effects on magnetic domains and the possibility of controlling them with microwave pulses. © Paul Scherrer Institute PSI/Markus Fischer
Inside this cryostat – a two-metre refrigeration device that is unique in the world and that achieves temperatures close to absolute zero – is a quantum magnet. Its properties are being studied using light from the X-ray free-electron laser SwissFEL. At very low temperatures around one Kelvin and below, the quantum material assumes a magnetic state that can be directly imaged using X-ray scattering. Here researchers can study, for example, the influence of quantum effects on magnetic domains and the possibility of controlling them with microwave pulses. © Paul Scherrer Institute PSI/Markus Fischer
