Name :
Date
of Birth :
Address
at Work : Scientist,
BETA Lab, FEL Program,
Institute for Plasma
Research,
Near
Gandhinagar
382 428,
FAX : + 91- 79- 3969017
(office)
Phone : + 91- 79- 3969001 to
015 Extn.272 (office)
Phone
:
+91-79-286 5724 (residence)
Telex : 121 - 7016 IPR IN
E-mail : <ravi@ipr.res.in>
URL
: http://www.ipr.res.in/~ravi
Educational
Profile :
Degree
:
Doctor of
Philosophy (Ph.D., 1993)
Period
of study :
1986 - 1992 (thesis submitted in December 1992)
University :
Title
of Thesis :
"Applications of Laser Induced Photo-acoustic
Effect to the Study of Gases
and
Solids”
Degree : Diploma in Foreign Language
Period
of Study : 1986-1988
University : Department of
Foreign Languages,
Technology,
Subject : Russian
Degree : Master of Science (M.Sc., 1986)
Period
of study : 1984 - 1986
University :
College
: Maharaja’s
College,
Subject :
Physics with specialization in Electronics
Degree : Bachelor of Science (B.Sc., 1983)
Period
of study : 1981 - 1983
University :
College
:
Subject :
Physics with Chemistry & Mathematics
1991-1993 Senior Research Fellowship Council of Scientific
& Industrial Research (CSIR),
Government of
1999-2001 Post-doctoral fellowship Japan Society
for Promotion of Science (JSPS),
Government of
SUMMARY
OF Ph.D. WORK :
Title
of Ph.D.Thesis : "Applications of Laser Induced Photo-acoustic Effect
to the Study of Gases and Solids”
THESIS
ADVISOR : Prof.
C. P. Girija Vallabhan Ph.D.,
Professor
& Director,
The major
area of the Ph.D. work is in the applications of lasers to trace detection,
characterization and analysis of
atmospheric pollutant gases like oxides
of nitrogen, sulfur dioxide and
formaldehyde using laser induced
photo - acoustic (PA) technique
in the gas
phase. The
phenomenon of absorption of modulated light and the subsequent heat
released in the
process of non-radiative
de-excitation is used in the PA technique.
The many advantages of this technique makes it an ideal tool for in-situ trace
gas detection and analysis.
Laser produced plasma
studies and laser
induced damage studies in polymers,
metals and high
temperature superconducting
materials using laser produced ultrasonics
have also been carried out. The technique has also been used to estimate the
laser fluence in laser-plasma experiments.
The experiments for
the PA detection of
some of the pollutant gases were undertaken using both Argon ion (cw) and Nd:YAG (pulsed) lasers, both pumping
Rhodamine 6G dye lasers. A Single cavity PA cell and a double cavity,
differential PA cell were designed
and fabricated for pulsed and cw applications respectively and the
cell characteristics studied in detail.
The detection of some common atmospheric pollutants was
carried out in the laboratory scale using laser-photoacoustic
spectroscopy. By the two-photon absorption (TPA) technique induced by
the pulsed dye laser, the TPA spectrum of formaldehyde vapor was established for the first time in
the 550- 560nm region.
The PA
signature spectra of nitrogen dioxide was established in the 550-560nm and in the
560- 610nm regions using both the pulsed
and cw dye lasers.
The dependence
of the PA signals with
various parameters were also
studied in detail and the detection limits obtained in the period of research were a few tens
of ppm.
An attempt was also
made in recording
the high resolution spectra of
nitrogen dioxide using
a mode-locked ring dye laser, but due to the complexity of the
results, a complete analysis of the data was beyond the
scope of the PhD.
The PA
technique was also applied to detect
the laser induced damage on various kinds
of materials ranging from
laser optics (coated and uncoated)
to metals and bulk polymers. The abrupt change in the PA signal from
an acoustic transducer attached
to the
sample under test indicates
the onset of
the damage. It was
also observed that
this technique could differentiate between the surface and
bulk damage which occurs
in that order. The different kinds of
laser produced damages on perspex and quartz optical plates were
also studied using
metallurgical microscope. This technique can be
applied to in-situ
monitoring of high power laser optics
to protect them from damage.
TECHNIQUES
AND EXPERTISE :
·
Laser induced Fluorescence
·
Opto-galvanic spectroscopy
·
Photoacoustic & Photothermal
deflection technique
·
Laser produced plasma emission spectroscopy
·
Working experience with Argon ion laser, ring dye laser, Nd:YAG laser, Carbon dioxide and Nitrogen lasers.
·
Boxcar-averaging and phase locked
(lock-in amplifier) detection techniques
·
High voltage systems : HV capacitor banks, Tesla transformers,
Relativistic Electron Beam and its diagnostics, pulsed magnet systems and their
synchronization/control etc.
·
Far-infra red experimental techniques, cooled FIR detectors,
spectrometers.
·
Data acquisition from instruments and scientific data analyzing
software like MathCad, Origin and also CAD package
like AutoCad etc.
·
Experience in using FEL simulation tools like TDA-3D and Genesis.
Though not as a part of my Ph.D. program, I have also worked extensively in the field of laser induced plasma produced by pulsed Nd:YAG laser. Studies include optimization, spectroscopic determination of the components in the plasma, spatial and temporal evolution of the different species in the plasma of metals, polymers, graphite and high-temperature superconductor samples (Y-Ba-Cu-O and Gd-Ba-Cu-O species). Preliminary work in the field of laser assisted deposition of thin films have been also done. I also have been associated with the design and development of a 30watt cw CO2 laser in our laser laboratory during my Ph.D. work.
JOB
Profile :
NATURE
OF WORK AT THE PRESENT JOB :
Since April 1993,
I have been working as a
Scientist at the Institute
for Plasma Research,
which is an autonomous research Institute of the Government of India. I have been involved in
the Free-Electron Laser (FEL)
project. The main work assigned was to develop a pulsed, high
power, mm wave FEL and its
diagnostics with the aim of using the laser for
plasma heating application in the tokamak
research being undertaken by our Institute.
My involvement in the FEL activities at our Institute include;
1.
Initial planning of the FEL work including design of wigglers, power
supplies, control systems etc.
2.
Characterization and optimization of the 400 kV, 1 kA pulsed relativistic electron beam (REB) system, including beam current, beam
voltage and energy measurements.
3.
Design, fabrication, optimization and characterization of the 5, 20 and
50 period electromagnetic wigglers. The maximum obtained field-on-axis is ~ 4 kG with a pulsed current of ~ 9 kA
4.
Integration of the electron-beam and the wiggler systems and their
power supplies, high voltage, high current switching circuits including design
of trigger synchronization between wiggler and REB pulses.
5.
Setting up of in-situ
diagnostics system for the electron beam, electromagnet wiggler, as well as a 6
channel, 18-170 GHz (K,
Ka, U, E, F & D bands) detector system for the FEL microwave output.
6.
Electron beam propagation through the 5 and 20 period wiggler system and its optimization.
7.
FEL work with a 15 period, 45 cm length
rare-earth permanent magnet wiggler system in collaboration with
8.
Using the 20-period electromagnet wiggler, we have been able to produce E-band (84
GHz) microwave radiation of a few hundred watts power using this setup. This is the first lasing of an FEL in India. Current experiments are directed towards increasing the laser output power by
at least an order of magnitude and also upgrade the 20 period wiggler to a 50
period wiggler.
9.
Fabrication, characterization and integration of the 50-period
wiggler has been completed and beam propagation studies are underway.
Completed
a two post-doctoral research
program at the Institute for Scientific and Industrial Research,
Affiliations :
1. Indian Laser Association,
2. Plasma Science Society Of
Research
Publications :
Over 20 research publications in peer reviewed journals
and technical reports. About 12 research
papers have been accepted for presentation in International conferences and have presented my
work in five International conferences. Have presented more
than 30 papers in various National Conferences in
Research
Interests :
Free electron laser related experimental and
simulation work. Electron beam accelerators and insertion
devices. Pulsed HV systems, sub nano
second signal detection.
Other
Interests & hobbies :
Photography, Camping/Hiking, Web related art designing
and layout work, music, electronics and computer hardware/software.
Date :
Place :
MAIN RESEARCH PUBLICATIONS (in Journals/Books/Research Reports)
Non-FEL
based research publications
:
|
1 |
"Two-Photon Absorption Spectrum
Of Formaldehyde Using Pulsed Gas Phase
Photoacoustic spectroscopy" A.V.
RAVI KUMAR, G. Padmaja, V.P.N. Nampoori and C.P.G. Vallabhan, In the book `Photoacoustics and Photothermal Phenomena II', Ed. by J.C. Murphy,
Springer-Verlag ( |
|
2 |
"Spectral Features Of Laser Induced Plasma From Y-Ba-Cu-O
And Gd-Ba-Cu-O High Tc
Superconductors" G. Padmaja, A.V. |
|
3 |
"Time Evolution Of Laser Induced Plasma From Gd-Ba-Cu-O
High Tc Superconductors"
G Padmaja, A.V. |
|
4 |
"Photoacoustic Detection of Two Photon Absorption in
Formaldehyde Using Pulsed Dye Laser" A.V.RAVI KUMAR,
G. Padmaja, V.P.N. Nampoori
and C.P.G. Vallabhan, Pramana-J.of
Physics, (India), Vol.33, p.L621, 1989. |
|
5 |
"Photoacoustic
Detection Of Two Photon Absorption In Formaldehyde At 1.06 mm Laser
Wavelength"
A.V. RAVI KUMAR, G. Padmaja, V.P.N. Nampoori and C.P.G. Vallabhan, J. Acoust.Soc.India,
vol.17, p.355, 1989 |
|
6 |
"Photoacoustic Detection Of High Resolution Spectra Of
Caf:Nd3+ Using Ring Dye Laser" S.Gopikrishnan, A.V.
RAVI KUMAR, R. Navil Kumar, V.P.N. Nampoori and C.P.G. Vallabhan, J.Acoust.Soc.India,
vol.17, p.69, 1990. |
|
7 |
"Detection Of Air Flow From Laser Irradiated Target Using Photothermal
Deflection Technique" K. Rajasree, A.V.RAVI
KUMAR, P. Radhakrishnan, V.P.N. Nampoori and C.P.G.Vallabhan, J.Acoust.Soc.India, vol.17, p.24, 1990. |
|
8 |
"Pulsed Photoacoustic Spectrum Of Nitrogen Dioxide : Pressure And Laser Power Dependence In The
560-570 nm Region" A.V. RAVI KUMAR, G. Padmaja, V.P.N. Nampoori and C.P.G.Vallabhan, J.Acoust.Soc.India,
vol.17, p.44, 1990. |
|
9 |
"Photoacoustic Detection Of Modulated CO2
Laser Beam" K. Ratnakaran, A.V.RAVI
KUMAR, and C.P.G. Vallabhan, J.Acoust.Soc.India,
vol.17, p.48, 1990. |
|
10 |
"Observation of Two Photon
Induced Photoemission Optogalvanic Effect"
P.R. Sasi Kumar, G. Padmaja,
A.V.RAVI KUMAR, V.P.N. Nampoori and
C.P.G. Vallabhan, Pramana-J.of
Physics (India), no.36, p.423, 1991. |
|
11 |
"Characteristics Of Laser Induced Plasma From High Tc
Superconductor" G. Padmaja, A.V.RAVI
KUMAR, P. Radhkrishnan, V.P.N. Nampoori and C.P.G. Vallabhan, Bull. Material Sci., ( |
|
12 |
"Evaluation Of Laser Ablation Threshold In Polymer Samples Using
Pulsed Photoacoustic Technique" A.V.RAVI
KUMAR, G.Padmaja, P.Radhakrishnan,
V.P.N. Nampoori and C.P.G.Vallabhan,
Pramana-J.of
Physics ( |
|
13 |
"Damage Threshold Determination Of Bulk Polymer Samples By Photothermal Deflection Technique" K.Rajasree, A.V. |
|
14 |
"Pulsed Photoacoustic Technique
For The Measurement Of Laser
Damage Threshold In Bulk Polymers" A.V.R. KUMAR, G. Padmaja, P. Radhakrishnan,
V.P.N. Nampoori
and C.P.G. Vallabhan,
In the book `Photoacoustics and Photothermal
Phenomena III', Ed.
Dane Bicanic, Springer-Verlag ( |
|
15 |
"Spatial And Temporal Analysis Of Laser Induced Plasma From A Polymer
Sample" G.Padmaja, A.V. RAVI KUMAR, P.Radhkrishnan, V.P.N. Nampoori
and C.P.G. Vallabhan, J.Phys.D:(Appl.Phys) ( |
|
1 |
"Diagnostics For Pulsed, High Power Microwave FEL Radiation" A.V.RAVI
KUMAR and K.K.Jain, Technical Report, Institute for Plasma
Research, IPR/TR-52/94, April, 1994 |
|
2 |
"Propagation Of Sheet Electron Beam Through A Planar, Five Period
Electromagnetic Wiggler" A.V.RAVI
KUMAR and K.K. Jain, Appl.Phys.Lett.,
( |
|
3 |
"Experimental Study Of Plasma Charging In A Multi-gap Pseudospark
Discharge", D.Sriram, A.V. |
|
4 |
“Generation Of Microwave Free-Electron Laser Radiation Using Sheet
Electron Beam And Electromagnet Wiggler”, A.V.RAVI KUMAR,
K. K. Mohandas and K. K. Jain, IEEE Trans.Plasma
Sci., (U.S.A.), vol. 26, No.3, pp.556-560,
June, 1998. |
|
5 |
“ Peak-Detector-Hold Based Circuit For Trigger Synchronization Of The
Electron Beam and Wiggler In A Free-Electron Laser Experiment”, A.V. |
|
6 |
“An
Off-axis Fifty Period Electromagnet Wiggler for Millimeter Wave Free Electron
Laser Experiment” K.K. Mohandas, A.V.
RAVI KUMAR and K.K. Jain, IEEE Trans.Plasma
Sci., (U.S.A.), 28, No.3, p.621,(2000) |
|
7 |
“Basic
study of self-amplified spontaneous emission in the infrared region with
L-band linac at Osaka University” R Kato, R.A.V. KUMAR, T. Okita,
S Kondo, T Igo, T. Konishi,
S.Okuda, S. Suemine and
G. Isoyama, Nucl.Instr.and
Meth. A 445, (2000), 164-168 |
|
8 |
“Simulation Studies Of The Proposed
Far-Infrared FEL
Amplifier At ISIR,
|
|
10 |
“Wavelength
Spectrum of Self-Amplified Spontaneous Emission in the Far-Infrared Region” R. Kato, T. Okita,
R. A. V. Kumar, T. Igo, T. Konishi, M. Kuwahara, M. Fujimoto, S. Mitani,
S. Okuda, S. Suemine and G. Isoyama,
Nucl.Instr.and Meth. A 475,
334-338, (2001)
|
|
11 |
“Study on the Focusing Property of a Planar Wiggler for the Infrared
FEL” M. Fujimoto, R. Kato, M. Kuwahara,
T. Igo, T. Okita, T. Konishi, R. A.
V. Kumar,
|