Studies on 2.45 GHz microwave ion sources Abhishek Nag IISER, KOLKATA Presented By: G.O. Rodrigues IUAC, New Delhi Supervised By:

Contents Introduction of ion sources Advantage of microwave ion sources Aim of the project Experimental Setup Experimental observations Conclusion

INTRODUCTION Ion Sources:  Ion sources are devices from which ions can be extracted and used for various applications like 1.Ion implantation 2.Etching 3.Surface patterning 4.Nano fabrication 5.industrial polymerization  The field of ion sources encompasses a broad field of research areas

Advantages of Microwave ion sources:  They provides long life stable ion beams for a variety of ion species.  High-current beams of singly-charged ions can be extracted in various sizes and forms.  Rugged and compact.

 Ion beam current depends on: 1.Plasma density 2.Plasma electron temperature 3.Extraction voltage 4.Extractor geometry  The characteristics of an ion beam are determined by plasma and the extractor geometry.

AIM OF THE PROJECT The aim is to study the ion source characteristics like beam intensities, beam stability and variation of these parameters as a function of source parameters. The extraction efficiency of the ion source has been studied by varying the ion source parameters and the extraction voltage.

Experimental Setup Schematic Diagram of the Experimental Setup RF Source (Magnetron) DC Breaker RF Window Plasma electrode Experiment Chamber Faraday Cup Permanent Magnet Rings Gas Inlet RF Tuner Ceramic Cold Cathode Gauge Water Deionizer/Cooling System Vacuum Pump Ammeter Ridge Waveguide Permanent magnet for electron suppression Normal Waveguide Microwave cavity

View of Experimental Setup Ridge waveguide Gas Inlet Permanent Magnet Rings Experimental Chamber DC Break RF Window Normal waveguide Permanent Magnet for electron suppression Microwave cavity Multi-electrode extraction Gas needle valve Deionized cooling water line Faraday Cup

View of the microwave ion source Gas Inlet Water Cooling line Beam direction

Magnetic Field plot inside the Plasma Chamber R Z Coil positions

Simulated electric field distribution with 4-step ridge waveguide system for microwave coupling to the plasma chamber for 1W input power

Design of axial magnetic field with respect to RF electric field along the chamber axis.

We experimentally determine how beam current varies with a)Gas Pressure b)Microwave Power c)Suppression Voltage d)Distance between the Injection Magnet ring and the ridge waveguide.

a) Variation with Gas Pressure The beam current increases with decreasing Gas Pressure

b) Variation with Microwave power at constant Gas Pressure

c) Variation of beam intensity with distance between injection magnet ring and ridge waveguide:

d) Variation with Suppression Voltage at constant Microwave Power:

e) Variation with Suppression Voltage at various levels of microwave Power:

Simulations using TOSCA and OPERA Beam trajectory at 4 kV extraction voltage and -1 kV suppression voltage Beam trajectory at 4 kV extraction voltage and -3 kV suppression voltage

Beam trajectory at 6 kV extraction voltage and -1 kV suppression voltage Beam trajectory at 6 kV extraction voltage and -3 kV suppression voltage

As from the Simulations we can observe that at -3 kV suppression voltage the beam intensity is more than -1 kV suppression voltage at 4 kV and 6 kV extraction voltage. Also, at 6 kV extraction voltage and -3 kV suppression voltage, the beam intensity is maximum as the beam is completely focused as shown from the simulations.

Conclusion The beam intensity has been measured by varying the source parameters, viz., gas pressure, microwave power, magnetic field and extraction voltage. The extraction efficiency has been measured and found to be maximum at 8 kV The beam stability is found to be within 10% over a period of few hours. Needs further improvement.

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