Glossary

Accelerators bring tiny, electrically charged particles to high speeds – almost to the speed of light, to nearly 300 000 kilometres per second. Strong radio waves accelerate the particles, while powerful magnets keep them on track. At PETRA, the accelerator acts as a light source, causing the particles to emit extremely short, intense X-ray flashes.

The experimental halls of the PETRA III research light source are named after famous scientists. One namesake is Ada Yonath. At DESY, the Israeli Nobel laureate carried out important work on her structural research on ribosomes, the “protein factories” of living cells.

A beamline is a part of an accelerator facility that guides the generated synchrotron radiation to a point of use – for example a measuring station.

The European XFEL is a unique research facility: It generates X-ray flashes that are billions of times brighter than the light from a storage ring and significantly shorter than a trillionth of a second. The 3.4-kilometre-long underground tunnel of the European XFEL begins on the DESY site in Hamburg-Bahrenfeld, runs in a north-westerly direction and ends behind the federal state border with Schleswig-Holstein in a huge experimental hall.

Since 2005, the free-electron laser has been generating a very special light: extremely intense, ultrashort pulsed X-ray laser flashes. Researchers from all over the world use it to track the movements of atoms and molecules.

A vacuum electron tube used as an oscillator or amplifier. In the klystron, an electron beam is velocity-modulated (periodically bunched) to produce large amounts of power.

The large experimental hall of DESY’s X-ray source PETRA III is named after the physics pioneer Max von Laue. He discovered X-ray beam interference, which is considered a milestone in the study of the atomic structure of matter. He was awarded the Nobel Prize for this achievement in 1914.

The material of permanent magnets has a strong magnetic field by itself, which exists without additional energy supply. At PETRA IV, a large number of these magnets will be used to save power.

Ring accelerator for electrons and positrons at DESY, later also for protons. Length: 2304 metres. The commissioning took place in 1978. Since 2010, PETRA has been one of the brightest storage ring X-ray radiation sources in the world.

In the 2.3-kilometre storage ring of PETRA III, electrons orbit at almost the speed of light. They are held on their paths by magnets. When they pass through special magnetic structures, called undulators, they are moved back and forth so strongly that they emit bundled X-ray light. This radiation is guided, shielded by tubes, to the measuring stations, where it can be used to examine a wide variety of samples.

A photon is one of the fundamental particles in nature and plays an important role in interactions with electrons. Depending on their frequency (and thus their energy), photons can have different names, such as visible light, X-rays and gamma rays. Photons are the most familiar particles in life: The light we see, the radiant heat we feel, the microwaves we cook with are all made up of photons of different energies. The most energetic of these particles are called X-rays and gamma rays. Lower-energy forms are, for example, ultraviolet light, infrared light and radio waves.

At PETRA III, quadrupole magnets (four magnets in a square opposite each other) focus the particle beams. These magnets are arranged in a row one behind the other in the ring. The quadrupole magnets are between five and seven metres long.

A circular (or nearly circular) particle accelerator in which either high-energy electrons and/or positrons or protons and/or antiprotons orbit many times. Because of the very different masses of protons and electrons, a storage ring must be designed for one type of particle or the other and cannot function for both.

Whenever a charged particle is accelerated, it radiates electromagnetic energy. An example is the emission of radio waves when electrons move back and forth in a radio antenna. A charged particle moving along an arc also experiences acceleration as it changes direction. The radiation emitted by such particles is called synchrotron radiation. It is particularly intense and highly directional when electrons moving at close to the speed of light are deflected in magnetic fields.

Special magnetic structures in which the electrons are made to emit X-ray light. When the electrons pass through the undulators, they are moved back and forth in them so strongly that they emit bundled X-ray light.