RF and Microwave Ion Sources Study at Institute of Modern Physics

Intense ion beam production is of high importance for various versatile applications from accelerator injectors to secondary ion mass spectrometry (SIMS). For these purposes, different types of ion beams are needed and, accordingly, the optimum plasma to produce the desired ion beams. RF-type plasma features a simple structure, high plasma density and low plasma temperature, which is essential for negative ion beam production. A very compact RF-type ion source using a planar coil antenna has been developed at IMP for negative molecular oxygen ion beam production. In terms of high-intensity positive ion beam production, 2.45 GHz microwave power-excited plasma has been widely used. At IMP, we developed a 2.45 GHz plasma source with both ridged waveguide and coaxial antenna coupling schemes, tested successfully with intense beam production. Thanks to the plasma built with an external planar coil antenna, high O2− production efficiency has been achieved, i.e., up to 43%. With 2.45 GHz microwave plasma, the ridged waveguide can support a higher power coupling of high efficiency that leads to the production of intense hydrogen beams up to 90 emA, whereas the coaxial antenna is less efficient in power coupling to plasma but can lead to attractive ion source compactness, with a reasonable beam extraction of several emA.

Highly Efficient Small Anode Ion Source

We describe some modifications to a Bernas-type ion source that improve the ion beam production efficiency and source operating lifetime. The ionization efficiency of a Bernas type ion source has been improved by using a small anode that is a thin rod, oriented along the magnetic field. The transverse electric field of the small anode causes the plasma to drift in the crossed ExB field to the emission slit. The cathode material recycling was optimized to increase the operating lifetime, and the wall potential optimized to suppress deposition of material and subsequent flake formation. A three-electrode extraction system was optimized for low energy ion beam production and efficient space charge neutralization. An ion beam with emission current density up to 60 mA/cm2 has been extracted from the modified source running on BF3 gas. Space charge neutralization of positive ion beams was improved by injecting electronegative gases.

Structural Behaviour of Shredded Waste Paper Reinforced Concrete Beam

Cement, sand, coarse aggregate, water and reinforcing bar are the materials to make a reinforced concrete beam. The waste paper has been dumped as waste and causes environmental pollution behind mill or landfill. The industry paper wastage for every year is increasing gradually. More spaces are being needed for landfills, uses energy loss of natural resources and increase of expenditure and various types of pollutions. Utilizing waste paper as an addition in reinforced concrete beam production will reduce environmental pollutions. This research is conducted to investigate the structural behaviour of reinforced concrete beam containing 10% shredded mixed and cardboard waste paper as additions in concrete with three types of reinforcements such as full shear reinforcement with stirrup spacing (SS=100 mm) and reduced shear reinforcements with stirrup spacing (SS=150 mm) and (SS=200 mm). All specimens are subjected to air curing at 28 days. The results of load-deflection behaviour and ultimate load-bearing capacity are better with 10% shredded mixed and cardboard waste paper at 28 days of air curing with full and reduced shear reinforcements. The finding shows that reinforced concrete beam with full and reduced shear reinforcements containing 10% addition of shredded cardboard waste paper in concrete exhibits the highest load at yield (Py), ultimate load (Pu), maximum load (Pmax) representing the load-carrying capacity, load at first crack (P1) and the lowest yield deflection (δy), ultimate deflection (δu), maximum deflection (δmax) compared to 10% SCPWP and 0%. This study indicates that shredded mixed and cardboard waste paper can be used as additional materials in reinforced concrete beam production.