• R K Bhandari

      Articles written in Pramana – Journal of Physics

    • 6.4 GHz ECR ion source at VECC

      G S Taki D K Chakraborty R K Bhandari

      More Details Abstract Fulltext PDF

      The 6.4 GHz ECR ion source that was indigenously developed a few years ago has been operating continuously for injecting oxygen and neon beams to the cyclotron since 1997. VEC-ECR is a single stage high magnetic field ion source provided with a negatively biased electron repeller placed on the axis, near the injection mirror point. The supply of cold electrons and use of low mass mixing gas improve the stability of ECR plasma. Very recently, the effect of aluminum oxide coating on the copper plasma chamber wall has been studied. The plasma chamber wall was coated with aluminum by vacuum evaporation method and then exposed to oxygen gas to form aluminum oxide. It was noticed that the process substantially shifts the charge state distribution to the higher charge state with an enhancement of ion current by an order of magnitude. With the aluminized plasma chamber, the VEC-ECR can now produce 12 µA of O7+, 6.5 µA of Ar12+, 1.5 µA of Kr20+ and 1.0 µA of Xe31+.

    • Experimental study of the dependence of beam current on injection magnetic field in 6.4 GHz ECR ion source

      G S Taki P R Sarma D K Chakraborty R K Bhandari P K Ray

      More Details Abstract Fulltext PDF

      The ion current from an electron cyclotron resonance (ECR) heavy ion source depends on the confining axial and radial magnetic fields. Some efforts were made by earlier workers to investigate magnetic field scaling on the performance of the ECR source. In order to study the dependence of the ion current on the injection magnetic field in the 6.4 GHz ECR source, we have measured the current by varying the peak injection field and have inferred that the variation of the current is exponential up to our maximum design injection field of 7.5 kG. An attempt has been made to understand this exponential nature on the basis of ion confinement time.

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