Plasma Focus Devices and Applications
Dense Plasma Focus (DPF) devices is a co-axial plasma accelerator which involves the storage of energy in a capacitor and pumping this energy in to a pinch plasma column during rapid collapse phase. The energy from the capacitor is discharged across a coaxial electrode geometry with the anode at the center and the cathode around it. The discharge initiates across a glass sleeve and a low energy plasma of energy ~ eV is set up. The Lorentz force brought about by the current pushes the plasma first axially and then radially to compress the plasma into a tight plasma column. At this stage the energy of the plasma increases from a few eV to a keV. If the design of the plasma focus is such that the pinch occurs at the current maximum, the compression is maximum and the plasma temperature can go upto > 100 keV. The formation of the pinch plasma column leads to the formation of plasma instabilities which can lead to the production of electric fields at certain regions in the plasma column and thus the resulting plasma temperature can be as high as a few MeV. This entire operation of the dense plasma focus device occurs in a few µs.
Depending on the operating conditions, the dense plasma focus device is capable of producing pinch plasmas of different temperatures. So this device can be used as a source for neutrons, hard and soft x-rays, energetic ions etc which can be used for a variety of applications. DPF attracted much attention during 1960 as an efficient fusion device, producing intense burst of neutrons when operated with Deuterium/ Deuterium-Tritium as filling gas. The interest in the plasma focus device is in 3 different directions – (1) as a source for thermonuclear fusion and neutrons, (2) as an x-ray source for lithography and (3) material processing using high energy density plasmas.
The major application of DPF devices that has emerged very strongly in last two decade is its application for material synthesis and processing. The DPF device based approach can also be used for both surface treatment and also thin film deposition of heavy metals using anode ablation. This field is growing very fast due to several intrinsic key features of DPF devices that are not available in other plasma devices used for material synthesis and processing. The beauty of this device is that large volume of material can be deposited onto the surface of the sample within a few ms. Also since the energy of the plasma is very high, nitrides of tungsten can be easily synthesized within the time scale of operation. This can be useful in increasing the resistance to fusion conditions.
DPF devices are one of the main research focus area of our group. Currently our group is focusing on
1. Plasma focus device and diagnostics for plasma and fusion-relevant education
2. High energy density pulsed plasma based alternate carbon overcoat deposition technology to push hard disk drives
storage density beyond 4 Tb/in2
3. Plasma processing of tungsten substrates to improve the surface hardness for Plasma facing materials in Tokamak
Our previous work involves
1. Design and Development of a 2.5 kJ Plasma Focus Device with Experiments on Electrical and Soft X-ray Optimizations
2. Understanding physics and technology of High Repetition Rate Plasma Focus Neutron Source and Its Application in
3. Fast Neutron Activation AnalysisNeutron emission studies from miniature and medium size plasma focus device
4. Vertical CNT growth on Si/Fe substrate