Engineering topics

Chowdhury, Abhishek

Publications and source records attributed to Chowdhury, Abhishek.

4 records

DOE OSTI2015

Rapid measurement of charged particle beam profiles using a current flux grating

The principle and physics issues of charged particle beam diagnostics using a current flux grating are presented. Unidirectional array of conducting channels with interstitial insulating layers of spacing d is placed in the beam path to capture flux of charge and electronically reproduce an exact beam current profile with density variation. The role of secondary electrons due to the impinging particle beam (both electron and ion) on the probe is addressed and a correction factor is introduced. A 2-dimensional profile of the electron beam is obtained by rotating the probe about the beam axis. Finally, a comparison of measured beam profile with a Gaussian is presented.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2014

Stopping potential and ion beamlet control for micro-resistive patterning through sub-Debye length plasma apertures

Focused multiple ion beamlets from a microwave plasma source is investigated for localized micron-scale modification of substrates in a patterned manner. Plasma electrodes (PE) with an array of through apertures having aperture diameters of the order of plasma Debye length are investigated for generating the beamlets. Extraction through sub-Debye length apertures becomes possible when the PE is kept at floating potential. It is found that the current – voltage characteristics of the extracted beamlets exhibits interesting features such as a space-charge-limited region that has a different behaviour than the conventional Child-Langmuir’s law and an extraction-voltage-limited region that does not undergo saturation but exhibits a Schottky-like behaviour similar to that of a vacuum diode. A switching technique to control the motion of individual beamlets is developed and the stopping potential determined. The beamlets are thereafter used to create localized micro-resistive patterns. The experimental results are compared with simulations and reasonably good agreement is obtained.

36 MATERIALS SCIENCE↗

DOE OSTI2012

Effect of beam limiting aperture and collector potential on multi-element focused ion beams

A compact microwave driven plasma based multi-element focused ion beam system has been developed. In the present work, the effect of reduced beam limiter (BL) aperture on the focused ion beam parameters, such as current and spot size, and a method of controlling beam energy independently by introducing a biased collector at focal point (FP) are investigated. It is found that the location of FP does not change due to the reduction of BL aperture. The location of FP and beam size are found to be weakly dependent on the collector potential in the range from -8 kV to -18 kV.

43 PARTICLE ACCELERATORS↗

DOE OSTI2010

Micron-focused ion beamlets

A multiple beam electrode system (MBES) is used to provide focused ion beamlets of elements from a compact microwave plasma. In this study, a honeycomb patterned plasma electrode with micron size apertures for extracting ion beamlets is investigated. The performance of the MBES is evaluated with the help of two widely adopted and commercially available beam simulation tools, AXCEL-INP and SIMION, where the input parameters are obtained from our experiments. A simple theoretical model based upon electrostatic ray optics is employed to compare the results of the simulations. It is found that the results for the beam focal length agree reasonably well. Different geometries are used to optimize the beam spot size and a beam spot {approx}5-10 {mu}m is obtained. The multiple ion beamlets will be used to produce microfunctional surfaces on soft matter like polymers. Additionally, the experimental set-up and plans are presented in the light of above applications.

43 PARTICLE ACCELERATORS↗