Idefix (or Dogmatix in English) in the French comic serves a major part of the plot but usually stays in the background. In Prague,  he complements the big laser Asterix. Picture: EUROfusion

Idefix (or Dogmatix in English) in the French comic serves a major part of the plot but usually stays in the background. In Prague, he complements the big laser Asterix. Picture: EUROfusion

Sometimes it needs a couple of good friends to accomplish big things. In the French comic, Asterix had a little friend called Idéfix (*) who mostly stayed in the background to solve a major part of the plot in the end. This is a different story of Asterix and his friend. It’s about the main characters of the Prague Asterix Laser System, one of only a few European laser labs which enable the examination of high density plasmas.

The laser ASTERIX arrived in the Czech Republic as a German immigrant. This arrival was the starting point for a joint laser laboratory founded by the Institute of Plasma Physics and the Institute of Physics established by the Czech Academy of Sciences (CAS) in Prague.

Until 1997, the Max Planck Institute of Quantum Optics (MPQ) in Garching (Germany) had operated the powerful iodine photo dissociation laser under its official name ASTERIX IV. Following an EURATOM-assented agreement, the Czech Academy of Sciences offered ASTERIX an entirely new home.

The Prague Asterix Laser System

In fact, the arrival of the German laser was the birth of a facility that is difficult to find in Europe. It offers a base for X-ray laser experiments using kilojoule-class pulses with a typical duration of 350 picoseconds. Therefore, ASTERIX IV was upgraded with a new beam distribution and delivery system. The target chambers of the Prague Asterix Laser System (PALS) were designed to provide a flexible capability for a broad spectrum of laser-plasma experiments, the X-ray laser application experiments in particular.

Playmobil figures should demonstrate the size of the laser. Picture: EUROfusion

Playmobil figures should demonstrate the size of the laser. Picture: EUROfusion

Get behind the flow

In fact, the study of plasma under conditions of extreme pressure and temperature serves fusion in many different ways. Hot plasma fuels a fusion experiment, but its characteristics are not yet fully understood.

Combining the short and ultra-short laser pulses

In fact, the by then newly set up laser lab in Prague enables the further investigation of hot laser-produced plasmas.

But the power of Asterix alone is not sufficient to unveil the secrets of plasma. Every Asterix needs a small canine friend. Sometime later, the former German kilo-joule gas laser was joined by a small but useful friend, a solid-state-laser CPA (Chirped Pulse Amplification) system providing ultra-short pulses which carry energy of only several Joules. The addition helped to realise synchronised short and ultra-short pulses in order to control the time delay between these two pulses.

The combination now provides us with the unique chance to carry out sophisticated time-resolved experiments. This means that a pulse can be stretched out in order to further investigate the influence of the shot on the plasma. Being smaller, but serving as the perfect team player to the powerful Asterix laser, the CPA laser was consequently named after the French comic character’s dog.

Pump-and-probe experiments

Libor Juha, Head of the Laser Plasma Department and of the Department of Radiation and Chemical Physics at the Institute of Physics CAS is very proud. Since 2000, the PALS facility has been one of the few in Europe which offers a considerable number of so called “pump-and-probe experiments” in both high-energy-density physics and high-energy chemistry. A pump pulse creates a special state of matter and a probe pulse is used for probing the state after an adjustable delay time.

Libor doesn’t need to advertise PALS any further: “Our lab is very busy and full of people most of the time.“ This is proven by the high number of shots which have been fired in the Czech laser lab. Last year, the laser lab celebrated a total amount of 50,000 shots – a huge number of tiny but powerful explosions which only a strong friendship can persist.

The real Prague Asterix Laser System. Picture: PALS

The real Prague Asterix Laser System. Picture: PALS

(*the English translation would be Dogmatix)