
The Spots
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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!
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).
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.
THE HIGH SPEED CAMERA
THE PRESSURIZED GAS CONSOLE

Riddle: Why do we usually use Argon and not volcanic gas ?
Construction
Every single experiment starts with a plan. Although many experiments have been lead in the “fragmentation lab” of theEarth Sciences Department of LMU Munich, each one has its own specifications, and requires to design and build newpieces.
Experiments
In the LMU facilities, we reconstruct the physical conditions of volcanic vents to create small-scale plumes.
In a sealed autoclave, volcanic rocks are pressurized. Then, pressure is suddenly released, blowing up the sample in ash-sized fragments. Several instruments can be simultaneously deployed to observe and measure the plume characteristics and the occurrence of flashes.
Field Work
The next stage will involve observations in the field with a view to identifying the parameters responsible for generating the lightning. As part of a large-scale project funded by a grant from the European Research Council (ERC), we have developed a unique set of instruments, with which we can measure and analyze these flashes. We used them on Cumbre Vieja, which provided an unmatched kick-off opportunity for our project.
The hard part – data evaluation
After the work in the field, we came home with a lot of datas, which have to be processed…