©Planeterrella The polar light simulator
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The first Grenoble planeterrella

Technical details about Planeterrella

For this experiment, and with the assistance of the SERAS office Study (CNRS), I use a vacuum chamber with a volume of fifty liters. The enclosure is made in Plexiglas, which filters ultraviolet correctly. The base is in aluminum. You can also use copper, more expensive and less convenient. It needs to be a non-ferromagnetic metal. On the inside, I have an electric duct mounted on a wheel, wich I can tilt and move on a gallow. The spheres are mounted on bases which can move up and down as umbrella feet. The potency and the feets are madi in plexiglass, and I use brass screws. You can also use of nylon, teflon, ABS plastic or any other not electrically conducting materials.

The spheres are hollow. We produced two spheres of diameter five and ten centimeters. They are made of two half-spheres which are screwed
one each other (you can also use sockets. The important thing is that the junction between the half-spheres is smooth).

The package was manufactured by the company Technicoplas (16 rue Fernand Pelloutier, 38130 Echirolles. Telephone: Fax:, which made for fast and cheap, an excellent job.

I use a power supply 10 kV Leybold Didactic GmbH, D = 30 A. What is necessary is actually voltage exceeding 300 V, but values up to 10 keV are not wanted (too much tension even creates problems). The experiment requests a low intensity, of the order of mA. To use an adjustable tension is not so interresting. When the intensity becomes too high, it leads to points of discharge and too much ionization.
I use a vaccuum pump Alcatel pallet type 2020 A. It is a primary oil pump. One usually finds equivalent pumps in all high schools in France.
I ordered rare-earth magnets to Radiospares code 179-5951. The experiment takes at least 4 of them. They are given for 11 000 G, but they are half powerful.

My pressure sensor is a Leybold vacuum france. It is a PIRANI TTR 91, flange DN 16 KF. I bought it with the digital display Display-one (E 314) and a cable connector type A. There is no need for a sensor to have the experiment working, but it is much better to have information on the pressure.

To make measurements of the emitted spectrum, I have just order a spectro to Ocean Optics, but it is a bit complicated for the public. I will soon put spectra on this site.

The manip is displayed on a small table on wheels that I have recovered. It is about one square meter.

The cost of this experiment is around 6000 € which revolve around :
Vaccuum chamber: 1500 €
Vacuum pump: 1500 €
Power supply : 1400 €
Pressure gauge: 600 €
Permanent magnets: 120 €
Metallic spheres: 400 €
Potency: 300 €
Cable: 100 €

Institut de Planétologie et d'Astrophysique de Grenoble (IPAG)