Our experiments

Every experiment begins with careful planning. Although many experiments have been conducted in the Fragmentation lab of the Department of Earth Sciences of LMU Munich, each one has its own specifications and requires the design and construction of new components.

In this project, we study how the quantity of ash particles relates to the numbers of observed flashes. To do so, we need several autoclaves, which are objects in which the particles are being pressurized, of varying capacities. We designed three experimental setups, each consisting of six different pieces, with a special attention paid to the sealing integrity and the resistance of all parts to high pressure.

Our lab

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The Spots

They guarantee a good quality of the videos

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THE TANK

Instead of blowing up the ash particles directly in the atmosphere, we blow them in a big tank, where we can deploy instruments to study the jet. In the left picture, a Faraday cage is visible, but we can also set-up lightning antenna, pressure sensors, and almost every instrument (particles are ejected by the nozzle at the center of the tank.

And above all, the tank prevents to spread ash in all the lab, and limits the surface to clean after each experiment!

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THE DIAPHRAGM SYSTEM

Diaphragms are thin cooper or steel disks designed to break around a defined pressure that close the autoclave. Pressurized gas is injected in the system by the tubes (left of the picture). Riddle: How would you design a system that break at exactly 100 bars, using two diaphragms breaking at an unknown pressure between 60 and 80 bar ?

A steel diaphragm before (left) ​and a cooper diaphragm after an experiment (right).
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THE AUTOCLAVE

The autoclave is this long black tube where the sample is pressurized before being blown up. Made of steel or allies metals, it can be heated up to 1200°C and can hold up to 200 bars! Pressure sensors and thermometers can be connected to monitor the pressure and temperature conditions within the autoclave during the pressurisation process and the burst.

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THE HIGH SPEED CAMERA

Flashes are so fast that we need high speed cameras to see them. Our Phantom v711 (the same as used on the field) is able to record 20 000 images per second. At this rate, 1 second of recording represent 10 Go of data!
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THE PRESSURIZED GAS CONSOLE

On the console, the gas pressure can be adjusted. The capillaries are connected to a highly pressurized argon bottle (200-500 bar). The pressure in the autoclave, but also between the different diaphragms is simply controlled by a system of valves.

​Riddle: Why do we usually use Argon and not volcanic gas ?

Experimental Volcanology

Study volcanism in Munich? There are four experimental volcanoes to study the phenomena of explosive volcanism at the department. The laboratories of experimental volcanism at the Ludwig Maximilians University of Munich provide unique opportunities to study the physics of mechanisms that are beyond direct access. Experiments are designed to analyse the behavior of magma under conditions as close to nature as possible. Experiments meet physical volcanism and numerical modeling. International projects and cooperation are the basis of our success.

The equipment at the FragLab comprises

  • 4 high temperature shock tubes
  • 2 internally heated high pressure autoclaves
  • 1 laser particle sizer (Coulter Beckmann)
  • 1 He pycnometry (Micromeritics)
  • 1 Nitrogen sorption (Micromeritics)
  • 1 vacuum furnace
  • 1 vacuum rotation extraction, video equipment
  • 1 high speed video system

Our research

  • Mechanisms of magma fragmentation
  • Speed of magma fragmentation
  • Fragmentation energy
  • Influence of permeability

Volcanoes under examination

  • USA: Mt. St. Helens, Augustine
  • Indonesia: Krakatau, Kelut, Merapi
  • Japan: Unzen
  • Russia: Shiveluch, Bezymiany
  • Italy: Etna, Vesuv, Stromboly, Campi Flegrei
  • Mexico: Colima
  • Greece: Santorini