study of wave propagation and potential structures in an expanding helicon plasma

201 Pages·2014·6.13 MB·English

STUDY OF WAVE PROPAGATION AND POTENTIAL
STRUCTURES IN AN EXPANDING HELICON PLASMA
By
KSHITISH KUMAR BARADA
PHYS06200704009
Institute for Plasma Research, Gandhinagar

A thesis submitted to the
Board of Studies in Physical Sciences
In partial fulfillment of requirements
For the Degree of
DOCTOR OF PHILOSOPHY
Of
HOMI BHABHA NATIONAL INSTITUTE

August, 2013

“There is nothing in a caterpillar that tells you it's going to be a butterfly”
……… Richard Buckminster Fuller
Architect, systems theorist, author, designer, inventor, and futurist
Dedicated to
My Family
ACKNOWLEDGEMENT

This thesis is complete because of numerous supports I have got from different people. First and
foremost I thank my supervisor Dr. Prabal Kumar Chattopadhyay for his guidance and support
throughout this thesis work. Though I have done experiments in my university, he introduced me
to experimental techniques through the study of electrical noise. I would like to thank him for the
freedom and openness he provided me with. Discussions with him always started from
experimental techniques and ended in nice physics. I would also like to thank Dr. Joydeep Ghosh
for encouragement in the rough periods of my thesis and also for fruitful physics discussions.
Thanks are due to Prof. Yogesh Saxena for constant encouragement and constructive criticism
which gave favorable direction to this thesis. I would also like thank Dr. Devendra Sharma for
the understanding I have on sheaths and double layers.
I am indebted to Dr. R. Ganesh, Dr. Sudip Sengupta, Dr. Devendra Sharma, Prof. R. Jha and
Prof. Amita Das for excellent teaching during the course work which helped me to understand
basics of plasma physics. I express my sincere thanks to Academic Dean, Dr. Mukherjee for his
timely help. I would like to extend my sincere gratitude to Shravan bhai, Shilpa mam, Smita
mam, Pragnya mam, Arundhati mam, Hemant bhai, Shailendra bhai, Sutapa mam and all Library
and Computer Centre Staff members for their support on many occasions. I extend my thanks to
Atrey Sir, Chamunde ji, Harvey ji, Sourbhan ji, Khanduri ji, Vartak ji, Savai ji, Sirin mam, Silel
ji and Hitesh bhai for all the administrative helps.
Staying in a hostel away from home never turned out to be difficult because of my friends,
juniors and seniors with whom I discussed my life, my Physics problems. Playing in the
weekends was utmost a necessity in these seven years. I would like thank every one of them for
their love and support they have provided me with during this period. I thank you Ujjwal,
Gurudatt, Vikram, Sita, Prabal, Ashwin, Deepak for always reminding me that we are the best. I
thank Neeraj bheya, Pintuda, Ritudi, Rajneesh bheya, Manas bheya, Bhaskar bheya, Anuraga
bheya, Mayadi, Kishor bheya, Vikrant bheya, Sunitadi, Shekhar bhai, Jugal bhai, Satya bhai,
Sharad bhai, Sushil, Rameswar, Sanat, Pravesh, Manjeet, Sayak, Soumen, Aditya, Vara, Mangi,
Vidhi, Deepa, Akanksha, Neeraj, Chandrasekhar, Meghraj, Harish, Rupendra, Bibhu, Samir,
Arghya, Debu, Bhumika, Anup, Ratan, Amit, Sonu, Umesh, Surabhi and Modhu.

I cannot forget those relaxing moments while trekking in the forests of Gujarat with Govind bhai,
Mahesh and Ghate in the frustrating periods of my life in between. Surprisingly, it was awesome
to know you three and I hope I have made a lasting impression on you as you have on me. In the
lab Sayak, Manjit and Soumen always provided a conducive and joyful atmosphere for physics
study. Thank you friends. Arindam bheya, it’s you who triggered the interest in diagnostics in
me. What a time we had! Thank you very much for being a part of my life even today. I would
like to thank Acharya ji, Sadrakhiya ji, Vishnu bhai, Swadesh bhai, Narendra bhai, Madan ji and
Variaji for their support in building up my experimental set up and Madan ji for showing the
Ahmedabad market. Thanks are due to Jignesh bhai, Praveenlal and all electronics group
member for their help in electronics circuits for diagnostics. Jiba’s food has always been blended
with his love for us which made the hygienic and healthy food tastier. When I used to go home, I
always missed his food.

This work would not have completed without the constant support, patience and encouragement
from my parents and family members. Dear Daddy, I learnt honesty from you and Mummy, I
learnt determination from you. My sweet younger sisters and brother, your love will remain
always with me. Finally, I would like to thank all those who have come into my life, putting an
unforgettable impression in my life including my classmates and teachers at school, college and
University.

Kshitish Kumar Barada
LIST OF PUBLICATIONS

1. Kshitish K. Barada, P. K. Chattopadhyay, J. Ghosh, Sunil Kumar, and Y. C. Saxena.
“A linear helicon plasma device with controllable magnetic field gradient.” Review of
Scientific Instruments 83, 063501 (2012).

2. Kshitish K. Barada, P. K. Chattopadhyay, J. Ghosh, Sunil Kumar, and Y. C. Saxena.
“Observation of low magnetic field density peaks.” Under review Physics of Plasmas
20, 042119 (2013)

3. Kshitish K. Barada, P. K. Chattopadhyay, J. Ghosh, Sunil Kumar, and Y. C. Saxena.
"Experimental Observation of Left Polarized Wave Absorption near Electron Cyclotron
Resonance Frequency in Helicon Antenna Produced Plasma." Physics of Plasmas 20,
012123(2013)

4. Kshitish K. Barada, P. K. Chattopadhyay, J. Ghosh, D.Sharma, and Y. C. Saxena.
“Charging of a plasma filled dielectric glass wall wrapped in a helicon antenna” to be
submitted.

5. Kshitish K. Barada, P. K. Chattopadhyay, J. Ghosh, D. Sharma, and Y. C. Saxena.
“Diverging magnetic field near helicon antenna increases antenna coupling efficiency in
low magnetic field operation.” To be submitted.

6. Kshitish K. Barada, P. K. Chattopadhyay, J. Ghosh, D. Sharma, and Y. C. Saxena.
“Transition from a quasi double layer to a multiple double layer containing current free
plasma” to be submitted.

7. Kshitish K. Barada, P. K. Chattopadhyay, J. Ghosh, D. Sharma, and Y. C. Saxena. “The
downstream density peak in low magnetic field helicon discharge” to be submitted.
Contents
Abstract…………………………………………………………………………………………. iv
List of Figures…………………………………………………………………………………… v
List of Tables…………………………………………………………………………………….xi
Chapter 1: Introduction
1.1 History of Helicon Sources ....................................................................................................... 1
1.2 Review of Relevant Previous Work .......................................................................................... 3
1.3 Motivation and objective .......................................................................................................... 6
1.4 Description of chapters and main findings ............................................................................... 7
References ..................................................................................................................................... 11
Chapter 2: Helicon Physics
2.1 Introduction ............................................................................................................................. 16
2.2 Derivation of dispersion relation ............................................................................................ 17
2.2.1 Vacuum Waves ................................................................................................................ 17
2.2.2 Plasma Waves .................................................................................................................. 20
2.3 Oblique propagation and Resonance cone .............................................................................. 32
2.4 Helicon waves in a cylinder .................................................................................................... 34
2.5 Helicon mode structure in non uniform radial density ........................................................... 37
2.6 Models of Helicon Power Deposition ..................................................................................... 38
2.7 Mode Transitions in Helicon Discharge ................................................................................. 39
2.8 Summary of the Chapter ......................................................................................................... 41
References ..................................................................................................................................... 42
Chapter 3: Experimental Set up and Diagnostics
3.1 Introduction ............................................................................................................................. 45
i