Laser Induced Plasma Diagnostics

LASER INDUCED PLASMA DIAGNOSTICS

Prof. Dr. M. Khaleeq-ur-Rahman Chairman Physics Department University of Engineering and Technology , Lahore, Pakistan

RESEARCH GROUP Prof. Dr. M. Khaleeq-ur-Rahman (Group Incharge /Director Advanced Physics Lab/Chairman Physics Deptt.)  Dr. M. Shahid Rafique  Dr. Khurram Siraj  Mr. Anwar Latif  Mr. Khurshid Aslam Bhatti  Ms. Safia Anjum  Mr. Hamid Latif  Mr. Arsalan Usman 

RESEARCH LABORATORIES

•

Laser and Optronics Center

•

Advanced Physics Labs, Research Center

RESEARCH FACILITIES       



Ti Sapphire Laser Nd-YAG Laser (First and second harmonics) Excimer Laser (KrF, XeCl) Diode Laser Nitrogen Laser (Indigenously Fabricated) Carbon dioxide Laser (Under Fabrication) Vacuum Systems Comprising Rotary, Diffusion and Turbo- Molecular pumps Penning, Pirani and Ionization vacuum gauges

CONT…..           

Plasma Plume IMAGING Systems Soft and Hard X-RAYS Detection Systems High Resolution Monochromator (UV-VIS) SEM (HITACHI 300 S) SPM/AFM XRD (Philips PAN Analytical), Raman Spectrometer Optical Microscope (MOTIC DB) High Resolution Reflecting CCD based Microscope (Olympus) Faraday Cups, SSNTD's, Langmuir Probes

EXPERIMENTATION FOR LASER MATTER INTERACTION

Layout of the Talk Plume Dynamics Time Integrated, Space resolved Image Capturing using CCD Time Resolved Image Capturing using ICCD

Radiation Emission Ions, Electrons, X-Rays and EUV

Conclusions

Plume Dynamics

EXPERIMENTAL SET UP FOR TIME INTEGRATED SPACE RESOLVED IMAGE CAPTURING USING CCD Laser: Nd: YAG Laser (1064 nm, 9-14 ns, 1.1 MW) Targets: 4N, Annealed, (1 x 1 x 0.1 ) cm3 Copper. Monochrome camera (BOSCH 0510) Computer Image System

CCD LTC

controlled Grabbing

TIME INTEGRATED IMAGES OF CU AT 10-3 TORR

Intensity, Density and temperature is maximum at the central region (core) Of LIP. It decreases as the distance varies on the either side of this region

(b) Pseudo Colored Image 180

Intensity (A. U.)

(a) Original Image

Cu

160 140 120 100 80 60 40 20 0

50

100

150

Distance (Pixels)

(c) Intensity Profile

200

EXPERIMENTAL SET UP FOR TIME RESOLVED IMAGE CAPTURING USING ICCD CAMERA Laser: Nd: YAG (532 nm, 6-8 ns, 6.75 MW)  Targets: 4N, Annealed, (1 x 1 x 0.1 ) cm3 Copper  ICCD (ICCD-5760/ IR-UV M0595310) Computer Controlled Image Capturing System

TIME RESOLVED ICCD IMAGES OF COPPER PLUME UNDER VACUUM ~ 10-3 TORR 10 ns

20 ns

70 ns

470 ns

970 ns

1970ns

Expansion is faster in the axial direction as compared to the radial direction and plume seems to vanish after 1970 ns delay time

Time Resolved ICCD Pseudcolored Images Different colors

pseudo show

10 ns

20 ns

the

intensity/density variation within the 70 ns

plume.

470 ns

At 70 ns delay time intensity

at

centre

becomes

maximum

images

970ns

1970 ns

as

compared other

the

to

time

the

delayed

which

is

indicative of hot and dense plasma

Figure 8: Pseudo Colored ICCD images of Au target at Operating Voltage 1.2 k V under Vacuum ~ 10-3 torr

Radiation Emission

EXPERIMENTAL SETUP FOR IONS INVESTIGATION BY SSNTDS Laser: Nd: YAG (1064 nm, 9-14 ns, 1.1 MW)

Targets: 4N, Annealed, (1 x 1 x 0.1 ) cm3 Copper.

Detectors: SSNTD’s

Results obtained from SSNTDs (Cu Target)

Ion Energies Vs Track radii Flux of ions depends on the

track diameter and is maximum for the larger track radius

Ion Flux Vs Angles

Ion Energy Vs Ion Flux

Ion flux decreases linearly The ions flux for energy is with the increase in the angle 100 keV is maximum and is with the normal to the target minimum for 750 keV. surface

A SCHEMATIC OF EXPERIMENTAL SETUP FOR ION EMISSION USING FARADAY CUPS Laser: Nd: YAG (1064 nm, 9-14 ns, 1.1 MW)

Targets: 4N, Annealed, (1 x 1 x 0.1 ) cm3 Copper, Zinc, Silver, Cadmium, Platinum and Gold Detectors: Cups’

Faraday

FARADAY CUP SIGNALS, TARGET: CU

Angles: 00 (50 mV), 300 (30 mV)

Angles: 600 (50 mV),,900 (30 mV)

Ion flux decreases with the increase in the angle along the normal to target surface which exhibits anisotropy and forward peaking of ions. Signal Profile for Time of Flight Measurements for energy of Emitted Ions Calculated energy of Cu ions is 35 keV

ANGLE (DEGREE) VS IONS FLUX (S-1)

Atomic Number Vs Ions Flux Ion Energy (keV) Energy of emitted ions (for

160

transient metals) is higher for

number.

140

Ion Energy (keV)

the metals with higher atomic

Pt

120

100

Ag Cd

80

60

CuZn

40 30

40

50

60

Atomic Number

70

80

EXPERIMENTAL SETUP FOR ELECTRON EMISSION USING LANGMUIR PROBE Laser: Nd: YAG (1064 nm, 9-14 ns, 1.1 MW) Targets: 4N, Annealed, (1 x 1 x 0.1 ) cm3 Platinum Detector: Langmuir Probe

Oscilloscope Target Langmuir Probe

V Probe Circuit

Laser

PARAMETERS FOR ELECTRON EMISSION (PLATINUM) (I–V Characteristics Curve) Child’s Langmuir law can be applied to calculate probe current. The probe potential decreases with the decrease in biasing potential as positive sheath of ions is reduced as more electrons reach the probe tip that neutralizes the ions. Peak for electrons increases because new primary electrons are further producing electrons. Thus multiplication of electrons occurs. Increase in the biasing potential causes an increase in the number of electrons collected by the probe tip. In air, the secondary electrons are produced by the interaction of primary electrons with plasma. Child Langmuir Law Ip = Ioe-eV/ kT

BIASING POTENTIAL VS ELECTRON TEMPERATURE (PLATINUM) Electron temperature decreases with the increase in the biasing potential vacuum

of

the

probe

whereas

it

under follows

opposite trend in air. For higher potential (> 10V) the trend is overlapping Electron Temperature of plasma in vacuum is less than that in air. The

higher

temperature

of

plasma in air is attributed by the collisions of secondary charged particles with air species.

Te = [eVa/ kT] / ln(Ip/Io)

BIASING POTENTIAL VS NUMBER OF PARTICLES IN DEBYE’S LENGTH

As Debye’s length in vacuum is smaller that that of in air so are Number

of

electron

in

the

Debye's sphere. From +5 V onwards the number of particles in Debye’s sphere in vacuum and air become equal.

ND = ne 4 /3. πλD3

SCHEMATIC OF EXPERIMENTAL SET UP FOR SOFT AND HARD X-RAYS EMISSION Laser: Nd: YAG (1064 nm, 9-14 ns, 1.1 MW) Targets: 4N, Annealed, (1 x 1 x 0.1 ) cm3 Copper, Zinc, Silver, Cadmium, Platinum and Gold Soft X-Rays Detector: BPX 65 PIN Photodiode with 2 mironmicron thick Ag filter

Soft X-Rays Detector: Photomultier Tube with Scintillator

SIGNAL PROFILE OF SOFT X-RAYS FROM LIP The soft x rays signals show discontinuities at the start, due the radiative recombination mechanism occur in optically thick region of the plasma and is formed at the second stage of the plasma expansion. Sharp peaks appear in signals due to continuum radiation emission in the region near the critical surface.

Zinc

Cadmium

SIGNAL PROFILE OF HARD X RAYS EMISSION The signals have edges or discontinuities at the start. Due to radiative recombination mechanism that takes place in denser region of the plasma near the target a very sharp peak appears. Another peaks appear in signals due to

Zinc

continuum radiation emission in the region near the critical surface. .

Cadmium

CONCLUSIONS  o

o

 o

o

Plume Dynamics: Initially, the plume is spherical, but, later, it is sharpened for transient metallic Plasmas. Intensity of silver plume is maximum where as that for zinc is minimum. Ion Emission Maximum flux of ions is along the normal to the target surface obeying forward peaking. The ions of maximum energy from all the targets also follow forward Peaking.

CONCLUSIONS (CONT…..)        

Electron Emission The values of floating potential, electron temperature and Debye’s length are greater in air than those of under vacuum. Electron density and plasma frequency are reverse in trend. The value of floating potential is positive in both cases. Electron temperature against biasing potential decreases monotically under vacuum while it follows opposite trend in air. In the negative potential region electron density vs biasing potential, has a valley in air, which is absent under vacuum. Debye’s length follows monotonic increase initially then decreases steeply in air. Number of electrons in Debye’s sphere in air and under vacuum becomes equal after a certain value of biasing potential.

CONT……… Soft and Hard X-RAYS  Soft and hard x-ray have different time durations for both zinc and cadmium.  X rays from Cd has larger FWHM than that for x rays from Zn.  Zn is better emitter of soft x rays than Cd  Cd is better emitter of Hard x rays than Zn 

GROUP PUBLICATIONS 1.

“Irradiation Effects on Copper” M.Khaleeq-ur-Rahman, A.Latif, M.S.Rafique, K.A.Bhatti, M.Imran, Radiation Effects & Defects in Solids, 164, 68, (2009).

2. “Magnetic Field Effect on Electron Emission from Plasma” M. Khaleeq-ur- Rahman, K. A. Bhatti, M. S. Rafique, A. Latif, K. T. Chaudhary, Vacuum, 83, 936 (2009) 3. “A study of IR radiation from Laser Induced Silver Plasma”, Anwar Latif, M.S. Rafique, M. Khaleeq ur Rahman, Khurshid Aslam and Fayyaz Hussain, Pak. J of Engg. Sciences, 2, 38 (2008) 4. “Effect of External Magnetic Field on the Deposition of Ba Fe12 O19” M. S. Rafique, M. Khaleeq-ur-Rahman, Saif ur Rahman, S. Anjum, M. S. Anwar, K. A. Bhatti, S. Saeed, S. Awan, Vacuum. 82, 1157(2008).

REFERENCES [1] Cremers D A and L J Radziemski.. Laser-Induced Plasma Application. Marcel Dekker, Inc., New York, (1989) [2] Jorgen Schou, Salvatore Amoruso and J. G. Lunney, Applied Physics A, 92, 907-911 (2008) [3] Claude Phipps (Editor), “Laser Ablation and its Applications”, Springer (2006) [4] Ready J F. “Effects of high-power laser radiation”. Academic press, New York, (1971). [5]http://www.photonics.cusat.edu/Research_Laser%20Ind uced%20Plasma.html.