Experimental chamber 1: Complex plasma diagnostics
Experimental chamber 1: Complex plasma diagnostics
The "octagon chamber" is the largest of our three experimental chambers. Thanks to its ample volume we can employ several diagnostic systems simultaneously. Most components have been equipped with motors controlled from outside for moving them during experiments, when the chamber is under vacuum. The motion is observed by cameras or through vacuum-tight windows, see picture:
Chamber interior: The target holder (right of the center) with motors and the target (a metal-coated glass plate). On the left side you see the parabolic mirror (black block with reflecting surface to the right), again with motorized adjustment.
The target holder defines the chamber’s geometrical center. It is used for rotating the target precisely and for moving it in three dimensions. In the experiments our targets (often flat and smooth metal plates) are hit by the laser pulses. The laser interaction creates plasma which we investigate in detail by various methods. Our research topics:
- Emission of fast electrons: The laser blasts electrons out of the plasma into different directions. We try to understand and to influence the underlying processes. An electron spectrometer yields the electron's velocity distribution. Other detectors are used for detecting the angular distribution.
- Emission of hard x-rays: Many electrons are pushed into the target during plasma generation at the surface. These electrons generate x-ray radiation which is detected and investigated by an x-ray camera and other devices. The results give information about the plasma, for example its temperature or energy content.
- Plasma development: What happens after the plasma generation? How will it expand and cool, and how will the energy be distributed? Most of this happens within several picoseconds – much too fast for standard diagnostics. We use a small portion of the laser pulse for obtaining "photographs" of the plasma. When this probe pulse's path is made shorter or longer, we observe earlier or later plasma phases. This sheds light on the temporal plasma development.