Laser plasma interaction in nano-particle copper targets

S. Chaurasia1, D. S. Munda1, Nitish Kumar2 , N. Kulkarni*, P. Ayyub3, N. K. Gupta, L. J. Dhareshwar1

1. Laser & Neutron Physics Section, Physics Group, Bhabha Atomic research Centre, Mumbai,

2. Cochin University of Science and Technology, Cochin, Kerala.

3. Department of condensed matter physics, Tata Institute of Fundamental Research, Mumbai.

e-mail –shibu@apsara.barc.gov.in

•Theme of our work on Laser plasma Interaction has been to study several target designs involving composite as well as mixtures of materials of varying density and target structuring over these past few years ( Au-Cu alloy, High Z doped polymers, Cu,Au coated with nanop- crystalline particle layers etc.)

•Effect of various laser parameters such as laser wavelength, intensity, pulse duration, different spatial and temporal shapes etc on laser-target coupling has also been studied extensively to achieve maximum x ray conversion efficiency and ion emission.

• A mixed metallic alloy of Au-Cu was observed to yield higher x ray conversion efficiency* and also the ion dynamics were studied**.

* X ray and ion measurements in laser produced plasma from gold-copper alloy targetsS. Chaurasia, D. S. Munda, C. G. Murali, N. K. Gupta and L. J. Dhareshwar, Accepted for publication-J. Appl.Phy.

** Ion dynamics in laser produced plasmas from mixed high Z targets, S.Chaurasia*, L. J. Dhareshwar and N.K. Gupta, accepted for publication- Radiation Effects and defects in solids.

Introduction :

Interaction of intense lasers with nano-particles and clusters has become a subject of intensive study in the recent times. Significant enhancement in soft and hard X-ray emission has been reported by several authors in targets with structured surfaces. Significant enhancement in laser light coupling in plasmas created from copper nano-particle targets using 100-2000 fsec laser pulses at 806nm at intensity 1015 to 1016 W/cm2

has been reported.Extremely energetic ( MeV) and highly stripped ionshave been produced by Intense laser interaction in noble gas clusters. Free standing Metal clusters( Ag,Pt) have been also used to generate highly charged and energetic ions. Nano particles embedded within host matrix (glass)

Motivation for our work

What happens at long laser pulse durations- Sub nanosecond ( 300-800psec), memory of initial laser pulse absorption by nano-particles retained?

What is the difference between free-standing metal clusters and layer of nano particles on bulk material?

Dependence of Laser absorption in nano-particle layers on laser parameters ( Energy, pulse duration, polarization, wavelength etc).

In our experiments reported here, we have compared-

solid polished copper targets having a 1µm and 3µm thick layer of copper nano-crystalline particles of about 15nm size with plain polished copper targets.

1. Ion emission from plasmas- Ion flux, Ion energy, Ion velocity etc.

2. X-ray emission in various spectrum range namely soft x-ray

(B10 filter > 0.7 keV), harder x-ray (Ti Filter 3.2 to 4.96 keV ) and

hard x-ray (Ni filter 4.6 to 8.3 keV)

3. Effect of Laser field polarization on x-ray and ion emission.

Experiments12 J / 500 ps Nd:glass laser operated at

Energy-2Joules.Pulse duration- 300-500 psec.Intensity-1013 -1014W/cm2

Targets-Polished copper solid target,1 µm, 3µm thick coating of copper nano-particles of 15nm size on

top of solid target.

Diagnostics-1. Langmuir probe array2. Faraday cup ion collectors 3. X-ray semiconductor detector cover with 12 µm titanium (3.2 to 4.96 keV)

and 5 µm nickel filter ( 4.6 to 8.32 keV ). 4. X-ray vacuum photodiode cover with B10 filter ( > 0.7 keV)

Picosecond laser laboratory

30GWatt/500 psec Nd:glass laser system

Lens

VERSA Disk laser

Oscillator150 mJ/ 300- 800 ps

MAmp 1 Amp 2

Amp3Amp 5

FaradayIsolator

Amp 4

Beam exp1.3 X

Beam exp2.4 X

M

M

M

M

P

Spatial Filter

VISAR

12Joule/500ps1014 W/cm2

Laser foot print at the final stage

45 mm

Laser system

(b)

Amp 1

OSC

Amp 2Amp 3

Amp 4

Amp 5

Experimental chamber outside view and inside view:

X-ray diagnostics-

• 3 channel X-ray semiconductor detector (quantrad make)

• 2 channel X-ray semiconductor detector (UDT sensor)

• X-ray pinhole camera.

• 7-channel x-ray vacuum biplanar photodoide

• X-ray transmission grating spectrograph

• X-ray crystal spectrograph

• X-ray CCD camera

Ion diagnostics-•Langmuir probes

•Ion collectors

•Electrostatic IEAEOS studies –

•Optical streak camera – shock velocity

• VISAR set-up – Particle velocity

Sputter-deposition at relatively high pressures (~20-200mTorr) and low substrate temperatures (~100-300K) is known to produce nanocrystalline films [1]. The average particle size can be controlled by proper choice of sputtering voltage, gas pressure and substrate temperature. In the present case, the nanocrystalline copper sample was prepared by dc magnetron sputtering (at 325V)from a 50 mm dia copper target at 100 mtorr pressure on a bulk copper substrate held at 300 K. The average particle size (as obtained from a masurement of the x-ray diffraction line broadening) was about 15-25 nm.

Target preparation

[1]P. Ayyub, R. Chandra, P. Taneja, A. K. Sharma, and R. Pinto, Appl. Phys. A 73, 67 (2001)

Array of Langmuir Probe• In our experiment we have used 3 Langmuir probe at different

angle (130, 30o and 45o) biased negatively with -30V.

• The Langmuir probes are cylindrical type with dia 0.5mm and

of length 4mm placed inside the vacuum chamber at a distance

of 11cm from target.

0

0

R2

50

C1

0.01uF

V1 -40V TO +40V

R1

10K

TO OSC.LANGMUIR PROBE

(a)(b)

( c )

Schematic of Faraday cup (Ion collector)

-0.000001 0.000000 0.000001 0.000002 0.000003-0.1

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7 E=1876.5mJ

ampl

itude

(V)

Time of flight( µs)

Cu plane target

(a) Schematic of Ion collector,

(b) Photograph of ion collector,

(c) Recorded signal of copper

plasma

Three Channel X-ray Detection Head For Diagnostics Of Plasma

A compact, three channel noise resistant detection head based onsemiconductor detectors (PIN diode, 100PIN250, by Quantrad Corporation, USA) has been built for the diagnostics of the x-ray emission from plasma as shown in fig. a.

Multi systems detection systems give the possibility of evaluating the level of x-ray emission at different ranges of wavelength.

The K-edge filter foils (Ni – 5 µm, Ti - 12 µm) are mounted on the filter holder which is held in position 5 mm from the diode in front at the PIN diode by the foil holder supporter.

Ti

Ni

20ns/divTi

Ni

X-ray vacuum photodiode array

•7 channel,

• 150 ps rise time,

•cover with B10 filter,

•negatively biased at 1kV00

0

C12nF R

250

D1D1N400

7

V1

-1 to -2KV

R11M

TO OSC.FILTER

Anode (Mesh Grid)

Cathode

X-ray measurement

0 2000 4000 6000 8000 100000.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

Tran

smis

sion

X-ray Energy (eV)

12micronTi 5micronNi

3.2KeV4.4 KeV

Ti - 3.2 KeV- 4.906 KeVNi - 4.4 KeV- 8.3 KeV

200 400 600 800 1000 1200 14000

1

2

3

4

5

6

7

8

9

10

structered Cu

Polished Cu

Ni Filter

Ti Filter

X-ra

y di

ode

sign

al(V

)

Laser energy (mJ)

Schematic of the polarization of laser light on normal incident target

Ion Detector

Laser beam

Pa

Pe

200 400 600 800 1000 1200 1400 1600 1800 2000 22000

200

400

600

800

1000

1200

1400

1600

1800

2000

2200

2400

2600

2800

3000

Pe -pol, 500 psec

Lang

mui

r pro

be s

igna

l (m

V)

Laser Energy (mJ)

Cunano13 Cunano30 Cunano 45 Cu13 Cu30 Cu 45

200 400 600 800 1000 1200 14000

200

400

600

800

1000

1200

1400

1600

1800

2000

2200

Lang

mui

r pro

be s

igna

l (m

V)

Laser Energy (mJ)

coppernano 13 coppernano 30 coppernano 45 copper 13 copper 30 copper 45

320 psec, Pe pol

Experimental Results with 1µm thick layer

Ion amplitude variation with Pe – polarized laser energy on copper and nano-copper targets

200 400 600 800 1000 1200 1400 16000

200

400

600

800

1000

1200

1400

1600

Pa-Pol, 500 psec

Lang

mui

r pro

be S

igna

l Am

plitu

de(m

V)

Laser Energy (mJ)

coppernano 13 coppernano 30 coppernano 45 copper 13 copper 30 copper 45

Ion amplitude variation with laser energy for a Pa polarized laser incident on copper and nano-copper targets

200 400 600 800 1000 1200 1400 16000

200

400

600

800

1000

1200

1400

1600

500 psec Pe and Pa pol

Lang

mui

r pro

be s

igna

l am

plitu

de (m

V)

Laser Energy (mJ)

copper S 13 copper S 30 copper S 45 copper P 13 copper P 30 copper P 45

200 400 600 800 1000 1200 14000

200

400

600

800

1000

1200

1400

1600

Effect of Pe and Pa polarized laser light on polished copper and nano-copper targets-

500 psec, Peand Pa- PolNano copper

Lang

mui

r pro

be s

igna

l am

plitu

de (m

V)

Laser Energy (mJ)

CunanoP13 CunanoP30 Cunano P45 CunanoS13 CunanoS30 Cunano S45

Ion velocity for copper and nano-copper target at three angle as a function of laser energy

0 200 400 600 800 1000 1200 140010

15

20

25

30

35 nano10degre Cu10

Ion

velo

city

(x10

6 cm

/sec

)

Laser Energy (mJ)

Ion velocity at 130 to target normal

0 200 400 600 800 1000 1200 1400

5

10

15

20

25

30 nano30degre Cu30

Ion

velo

city

(x10

6 cm

/sec

)

Laser Energy (mJ)

0 200 400 600 800 1000 1200 1400

6

8

10

12

14

16

18

20

22 Cu -nano 45 Cu 45

Ion

velo

city

(x10

6 cm

/sec

)

Laser Energy (mJ)

Observations:

1. It is observed that the behaviour of plasma generated from copper nano-particle coated target is different from that of plain copper target.

2. The ion flux in case of nano-particle coated copper targets is higher for Pa polarization of the laser pulse as compared to Pe polarization.

3. Nano-particle coated targets show higher ion flux compared to plain copper. The same is observed for ion velocity also.

4. No difference in ion flux ablated between Pa and Pe polarized light for a polished copper target.

5. Laser absorption is higher for a nano-coated surface as compared to a plane polished surface.( because ion velocity is found higher for nano)

Experiments with 3 micron thick layer of copper nano particle on copper substrate

In these experiments a copper nano particle layer of 3 micron is coated on copper base.

For the ion parameter detection an array of Langmuir probes and ion collector used.

For the x-ray detection we have used semiconductor pIn diode cover with titanium filter and indigenously developed x-ray vacuum photodiodes cover with B10 filter ( tranmission > 0.7 keV). This B-10 foil had a Polycarbonate base film of thickness 2 µm and had a density of 0.24 mg/cm2. 80% of this density was due to the thickness of the base film and 20% due to the 0.6µm thick Aluminum coating. From the manufacturer’s data, the equivalent thickness of one B-10 foil was calculated as 0.05 mg/cm2, 0.15mg/cm2 and 0.0376 mg/cm2 of aluminium, carbon and oxygen respectively.

Comparison of copper and nano-copper targets for Pa (p) polarized light

0 200 400 600 800 1000 1200 1400 1600 1800 20000

100

200

300

400

500

600

700

800

900

1000 CuP5 NanoP5

Ion

ampl

itude

(a.u

.)

Laser energy (mJ)

0 200 400 600 800 1000 1200 1400 1600 1800 20000

100

200

300

400

500

600

700

800

900

1000 CuP10 NanoP10

Ion

ampl

itude

(a.u

.)

Laser energy (mJ)

0 200 400 600 800 1000 1200 1400 1600 1800 20000

100

200

300

400

500

600

700

800

900

1000

CuP25 NanoP25

Ion

ampl

itude

(a.u

.)

Laser energy (mJ)

0 200 400 600 800 1000 1200 1400 1600 1800 20000

50

100

150

200

250

300

350

400

fc v

olta

ge

Energy

fcpeaknano fcpeakCu

Comparison of copper and nano-copper for Pe (s)polarized light

0 200 400 600 800 1000 1200 1400 1600 1800 20000

100

200

300

400

500

600

700

800

900

1000 CuS nanoS

Ion

ampl

itude

at 5

0 (a.u

.)

Laser energy (mJ)

0 200 400 600 800 1000 1200 1400 1600 1800 20000

100

200

300

400

500

600

700

800

900

1000 CuS nanoS

Ion

ampl

itude

at 1

00 (a.u

.)

Laser energy (mJ)

0 200 400 600 800 1000 1200 1400 1600 1800 20000

100

200

300

400

500

600

700

800

900

1000

CuS nanoS

Ion

ampl

itude

at 2

50 (a.u

.)

Laser energy (mJ) 0 200 400 600 800 1000 1200 1400 1600 1800 20000

100

200

300

400

CuS nanoS

Ion

ampl

itude

(a.u

.)

Laser energy (mJ)

Faraday cup

Comparison of nano copper target with Pe (S) and Pa (P) Laser beam

0 200 400 600 800 1000 1200 1400 1600 1800 20000

100

200

300

400

500

600

700

800

900

1000

nanoS5 NanoP5

Ion

ampl

itude

(a.u

.)

Laser energy (mJ)0 200 400 600 800 1000 1200 1400 1600 1800 2000

0

100

200

300

400

500

600

700

800

900

1000

NanoS10 NanoP10

Ion

ampl

itude

(a.u

.)

Laser energy (mJ)

0 200 400 600 800 1000 1200 1400 1600 1800 20000

100

200

300

400

500

600

700

800

900

1000

nanoS25 NanoP25

Ion

ampl

itude

(a.u

.)

Laser energy (mJ)

400 500 600 700 800 900 10001100120013001400150016001700180050

100

150

200

250

300

350

400

nanoS nanop

Fara

day

Cup

sig

nal (

mV)

Laser Energy (mJ)

800 1000 1200 1400 1600 1800 2000

50

100

150

200

250

300

350Y

Axi

s Ti

tle

X Axis Title

CufcP CuS

Comparison of copper target with Pe (S) and Pa (P) Laser beam

-0.000001 0.000000 0.000001 0.000002 0.000003-0.1

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7 E=1876.5mJ

ampl

itude

(V)

Time of flight( µs)

Cu plane target

0.0 1.0x10-6 2.0x10-6 3.0x10-60.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

Am

plitu

de(V

)

Time of flight(sec)

E=1737mJ

CU nano target

Faraday cup record of copper and nano copper coated plasma

Fast ion velocity Vs Laser energy

200 400 600 800 1000 1200 1400 1600 1800

5.0x107

1.0x108

fast

ion

velo

city

(cm

/ se

c)

Laser Energy (mJ)

nanocopper Copper

Kinetic energy Vs Laser energy for fast ions

200 400 600 800 1000 1200 1400 1600 18000

50

100

150

200

250

300

350

400

450

500

aver

age

ion

Ene

rgy

(keV

)

Laser Energy (mJ)

K.E.nano K.E.Cu

1000 1200 1400 1600 1800 2000

1.5

2.0

2.5

3.0

3.5

4.0

4.55.0

5.5

6.0

6.5

7.0

7.5

8.0

8.5

xraynano xrayCu

x ra

ysig

nal w

ith T

i (V

)

energ y (mJ)

400 600 800 1000 1200 1400 1600 1800 2000 2200 24000

1

2

3

4

5

6

Cuch2 nanoch2

x ra

y ch

2 vo

ltage

(V)

energy (mJ)

biplanar Ch2

X-ray measurement from copper and nano-copper plasma using x-ray semiconductor diodes covered with Ti filter and x-ray vacuum photodiode covered with B10 filter

Recent publications

1. “Enhancement of x-ray emission and ion velocity in laser plasmas from gold – copper mixed target”-S.Chaurasia*, D.S.Munda, C.G.Murali, N.K.Gupta and L.J.Dhareshwar, Accepted for publication in J. Appl. Phys.

2. Ion dynamics in laser produced plasmas from mixed high Z targets, S.Chaurasia*, L.J.Dhareshwar and N.K.Gupta, accepted for publication in Radiation Effects and Defects in Solids.

3. “Generation and measurements on a variable duration, short pulse, cavity dumped Nd:YAG laser”- S. Chaurasia, C.G.Murali,L.J.Dhareshwar, R.Vijayan, A.C.Shikalgar, B.S.Narayan, In press Laser and Optics Technology.

4. “Production of high-current heavy ion jets at the short-wavelength subnanosecond laser-solid interaction”- J. Badziak, A. Kasperczuk, P. Parys, T Pisarczyk, M.Rosiński,L.Ryć,J.Wołowski, S. Jabłoński, R. Suchańska, E. Krousky, L. Láska, K. Masek, M. Pfeifer, J. Ullschmied, L. J. Dareshwar,I. Foldes ,L. Torrisi,P. Pisarczyk, APPLIED PHYSICS LETTERS 91, 081502 2007

5. Induced birefringence in optically isotropic glass by a short pulsed Nd:YAG laser”-Paramita Deb, K.C.Gupta, C.G.Murali, L.J. Dhareshwar, B.K. Godwal, Journal of Optics A-pure and Applied Optics,vol8, 903, 2006.

Cont…6. Amol R. Holkundkar, N. K. Gupta and L. J. Dhareshwar, “Hydrodynamic

Investigations of Intense sub-picosecond laser mater interaction”, IEEE transactions on plasma science, 34, 2572-2578, (2006).

7. “ X-ray and ion emission characteristics of plasmas ablated from solid materials using a high power Nd:glass laser”-L.J.Dhareshwar,S.Chaurasia, C.G.Murali,N.K.Gupta, B.K.Godwal,Journal of Material Science Vol41(2006), 1623-1630.

8. “ Measurement of laser driven shock wave transit time through thin aluminiumtargets by optical shadowgraphy”- L.J.Dhareshwar,N.Gopi,C.G.Murali,N. K.Gupta, B.K.Godwal, Shock Waves,Vol 14(4),231-237(2005).

L. J. Dhareshwar