At the very top
Research with a view
Beauty and decay are the researchers' companions at the highest workplace in Germany: the Zugspitze. They research cosmic radiation using snow in plastic buckets and a few spheres. A report
The word "timeless" comes to mind when looking at the Wetterstein mountain range, but up here it is completely misplaced. Perhaps nowhere else in Germany has time left such deep traces. There is the Southern Schneeferner: a former glacier that has long since lost its accumulation zone, "dead ice". Next to it lies the Northern Schneeferner, which up until two years ago was covered with reflecting tarpaulins to slow down its melting. This has been stopped now; it is likely to have completely disappeared 30 years from now. Some snowcats are engaged in "snow farming"; they push together the snow and compact it to slow down its melting and to allow its redistribution again in winter, for when the skiers arrive.
When radioactive matter is contained in the air, rain washes it down to the ground – a process called deposition. Using models, one can precisely calculate how fast a certain amount falls. This is important, for example, when after the release of radioactive matter reliable information about the contamination is required within a short period. Yet what if it does not rain but snows? "So far, this was untrodden ground in the field of radioecology", says Kerstin Hürkamp. Yet snow carries even more radioactive matter to the ground than rain.
Hürkamp needs to pay great attention to detail in order to understand the process: How much snow falls in how short a period of time? What is its temperature? Where does the wind blow from? What is the consistency of the snow? The shape of the individual snowflakes is particularly important. The larger their surface, the more radionuclides they absorb. This is why Hürkamp differentiates between the crystal forms. When six-armed crystals fall, it is a "dendritic event". When more than half of the snowflakes look different, for example like needle crystals, it is a "mixed event".
Hürkamp is assisted by a 2D video disdrometer that stands on the measuring terrace of the Schneefernerhaus. This is a metallic cylinder that is open at the top and into which the snowflakes fall. They are scanned by two laser cameras offset against each other, so that each individual snowflake produces two two-dimensional images. A software that was newly developed by the Helmholtz Zentrum München analyses these images and assesses the type of snow. Using images and measured data, Hürkamp calculates the degree of contamination snowing down to Earth.
This leads to the second questions the Zugspitze researchers pursue: What effect does radiation have on humans? Here, Kerstin Hürkamp and Werner Rühm are particularly interested in so-called secondary radiation. It originates when cosmic particles, such as a proton from space, hit other particles, such as an oxygen nucleus. This nucleus bursts and releases ions and neutrons – secondary radiation.
About half of the radiation arriving on Earth is accounted for by neutrons. Secondary neutrons from cosmic radiation can be measured at the Schneefernerhaus – not only their number but also their energy, that is, the speed at which they travel.
Rühm stands in a tiny wooden house on the measuring terrace. It looks like an extremely high and steep triangular tent. Its interior reveals why the scientists call the building the "Kugelalm", the alpine pasture of spheres: 15 white, spherical neutron detectors of varying size are mounted at half the hut's height. Each sphere registers neutrons that rain down onto the detectors with varying degrees of energy.
Every human absorbs a dose of about 300 microsievert per year due to cosmic radiation; that is about six times less than through medical applications such as taking X-rays. However, this fluctuates greatly: flight personnel are subjected to significantly higher amounts of radiation. The Helmholtz Zentrum München has developed a programme to calculate the dose absorbed by flight personnel; it varies depending on flight altitude, duration and route. The programme is used by Lufthansa and Air France, among others. Up here, the thus calculated values can be verified.
When only its red rays illuminate the mountain range. Alpenglow, they call it, but that is an understatement. Actually it looks as if all was on fire. This is an event that is different to all events she and Rühm investigate in their lives as researchers, different to incidents, mixed events, radiation. It is predictable but not reproducible, has long since been explained, is actually totally trivial, almost banal. But unique. Each time newly so.
Three Helmholtz centres are represented at Germany's highest research station. The Helmholtz Zentrum München has researchers from the Institute of Radiation Protection and from the Department of Environmental Science working at the Zugspitze. Scientists from the Institute for Meteorology and Climate Research at the Karlsruhe Institute of Technology research the distribution of water vapour in the atmosphere. To do so, the scientists shoot short laser light pulses vertically up into the air and then measure in what chronological order the light is reflected by the atmosphere. On the one hand, water vapour is the most important greenhouse gas and therefore co-responsible for global warming; on the other, it contributes to the formation of clouds and precipitation, which can also have a cooling effect.
The German Aerospace Center is likewise represented at the Zugspitze: with the German Remote Sensing Data Center, the Remote Sensing Technology Institute and the Institute of Atmospheric Physics. Moreover, the Deutscher Wetterdienst (German Meteorological Service), the LMU Munich university, the Max Planck Society, the TU München technical university, the Umweltbundesamt (German Federal Environmental Agency), the University of Augsburg, the Free State of Bavaria and changing research partners work at the Schneefernerhaus.