Our group is engaged in a broad range of research topics in the field of laser-produced and Z-pinch plasmas, encompassing experimental investigations, the development of advanced diagnostic techniques, as well as theoretical studies and numerical simulations. The basis for our activities is our laboratory at the Department of Physics at the Faculty of Electrical Engineering CTU.
Our Laboratory
The heart of our Plasma Physics Laboratory is the PFZ-200 plasma focus, a unique device capable of achieving D–D nuclear fusion reactions. It is a pulsed high-current discharge system in which, due to the extremely high current exceeding 200 kA, a so-called Z-pinch implosion occurs, heating the plasma to temperatures comparable to those found in stellar cores. When an appropriate working gas is used – heavy hydrogen (deuterium) – fusion nuclear reactions take place, accompanied by the generation of intense neutron pulses. In addition to nuclear fusion, the comprehensive set
of diagnostics enables the investigation of numerous physical phenomena, including plasma implosion, instability dynamics, fast neutron, X-ray and EMP emission, among many others.
Research in this field finds applications in a wide range of areas of fundamental science, as well as in potential practical applications such as materials engineering, fast probing using neutron, X-ray, and proton pulses, and related technologies.
The laboratory also hosts courses in Plasma Diagnostics and Physics for Electroenergetics, as well as student research projects and thesis work at all academic levels.
Photo of the PFZ-200 Plasma focus device and selected diagnostics
The PFZ-200 Plasma Focus Device
The PFZ-200 plasma focus device consists of a capacitor bank composed of four 4.7 μF capacitors, which can be charged up to 20 kV. Each capacitor is equipped with a fast high-pressure spark-gap switch. Triggering these spark gaps applies the voltage to the electrodes by coaxial cables, resulting in the discharge of the capacitors by a current pulse with a rise time of approximately 1.5 μs and a peak current of about 230 kA.
| Capacitor battery | 4 4.7 µF |
| Charging voltage | 18 – 20 kV |
| Peak current | 230 kA |
| Current pulse rise time | 1.5 µs |
| Maximum fusion yield (Neutron output) | 108 |
PFZ-200 discharge chamber with the electrode system
The current pulse generated by the process described above is applied to a coaxial electrode system consisting of a central conductor – the anode and several cathode rods forming the outer conductor of the coaxial structure. The electrode system is located inside a discharge chamber, which is first evacuated to a vacuum level of up to 10-5 mbar and subsequently filled with the working gas, typically deuterium (heavy hydrogen 2H).
Principle of Plasma Focus
The operating principle of the plasma focus device is illustrated in the figure below. The source of electrical energy for a discharge carrying such a high current is typically a capacitor bank formed by connecting the required number of capacitors in parallel. In the case of our PFZ-200 system, the capacitor bank is charged to a high voltage of 18-20 kV. The charged capacitor bank is connected to the electrode system through coaxial cables, used to achieve low inductance, and a fast switching element, typically a spark gap switch.
The electrode system has a coaxial configuration, with the anode located at the center along the axis and an array of cathode rods forming the outer conductor. When a high voltage is applied, electrical breakdown occurs along the surface of the insulator separating the anode from the cathodes, ionizing the gas in close proximity to the insulator surface. This ionized gas, known as plasma, is electrically conductive. As a result, an electric current begins to flow between the cathodes and the anode, generating a strong magnetic field. This magnetic field acts on the current sheath through the Lorentz force, accelerating it in the axial direction toward the end of the coaxial electrode system. When the accelerated plasma sheath reaches the end of the coaxial electrode system, it is slightly pushed beyond its edge by the Lorentz force, forming the so-called “umbrella shape.” The central part of this plasma structure, through which the current flows toward the anode, is compressed by the magnetic field generated by the current itself through a phenomenon known as the pinch effect.
Using the nanosecond four-frame X-ray camera available in our laboratory, we are able to observe hot imploding Z-pinch plasma with high temporal and spatial resolution. This enables us to investigate the physics of the implosion, the development of instabilities, the disruption of the current channel, and other related phenomena. An example of such a sequence, capturing imploded Z-pinch plasma with characteristic instabilities, is shown in the figure below.
It should be noted that the green color in the image above does not represent the actual color of the discharge, but it is the characteristic emission color of the phosphor screen of the gated MCP (Micro Channel Plate) image amplifier, which simultaneously serves as a converter of X-ray radiation into visible light subsequently recorded by a CCD camera.
During such a Z-pinch implosion in our plasma focus device, up to 108 D–D nuclear fusion reactions may occur, accompanied by a corresponding number of emitted neutrons.
Data acquisition and control system
During plasma focus discharges, various processes lead to the generation of intense electromagnetic pulses (EMP). Such pulses may interfere with diagnostic and control signals and can potentially damage sensitive electronic equipment. For this reason, all sensitive electronics must be protected from EMP effects by means of Faraday shielding.
Theory and simulations
In addition to experimental research, our group is also engaged in numerical simulations of both electrical discharges and laser-produced plasma, with a particular focus on magnetohydrodynamic models and in-house developed ion tracking simulation codes.
Magnetohydrodynamic (MHD) simulations
Numerical modeling of Z-pinch and laser-produced plasmas using magnetohydrodynamic (MHD) simulations provide insight into plasma dynamics, instability development, shock formation, and energy transport processes under extreme conditions. A significant part of our computational research is based on the FLASH simulation code, which is widely used for high-energy-density plasma and astrophysical applications.
Interpretation of experimental data by numerical simulations
Our group also study magnetic fields in Z-pinch plasmas using ion and proton deflectometry techniques. By analyzing the deflection of probing charged particles in the plasma environment, these diagnostics enable the reconstruction of magnetic field structures and their temporal evolution. Numerical modeling is employed alongside experimental measurements to support the interpretation of the acquired data and to improve the understanding of plasma dynamics during the implosion process and particle emission.
Electronics and fine-mechanic development workshop
Our group is actively involved in the development of new diagnostic tools for plasma physics research. For these purposes, the Department of Physics operates a fully equipped workshop for precision mechanical work, high-voltage, high-frequency electronics, and microelectronics. In addition to extensive measurement instrumentation and facilities for the development of electronic devices, the workshop is equipped with a laser cutter and two 3D printers.
The workshop is used not only for the development of new diagnostics subsequently employed in experiments, but also by students at all academic levels in the course of their thesis projects and research work.