PLASMA CHANNELS IN AIR PRODUCED BY UV LASER BEAM: MECHANISMS OF PHOTO IONIZATION AND

POSSIBLE APPLICA TIONSa

V.D. ZVORYKIN, A.A. IONIN, S.1. KUDRYASHOV, A.O. LEVCHENKO, A.G. MOLCHANOV, L.V. SELEZNEV, D.V. SINITSYN, N.N. USTINOVSKII

P.N. Lebedev Physical Institute of RAS, Leninskii prospect 53, 119991 Moscow, Russia

Plasma channels in atmospheric air can be produced by UV laser beam combined of high-intensity 100-fs pulses for an effective 3- or 4-photon ionization and 100-ns pulses for maintaining the electron density. Ti:SapphirelKrF laser facility GARPUN-MTW is described to be able producing -1.5/1 00-) energies in short / long pulses at 1.=248 nm. It is a fine tool to create plasma channels for triggering a long-distance HV discharge (lightning) and for other applications. The pilot experiments were performed with both short and long UV pulses to demonstrate I-m long perfectly guided HV discharge and to study ionization mechanisms in different gases (atmospheric air, nitrogen, argon).

1. Introduction

Plasma channels produced by laser radiation in atmospheric air or some other gases are of great interest for many fundamental problems and technical applications. Among them there are triggering and diverting of lightning [1], directing of microwave radiation to overcome its original divergence [2], laser­driven acceleration and guiding of electrons [3]. In contrast to early experiments with CO2 laser pulses of Ils-Iength [4, 5] where opacity of the dense plasma produced via avalanche ionization restricted the length and continuity of the channel, recent approaches based on the use of UV [I] or fs-Iength [6] laser pulses can produce long-distance partially ionized tracks in a gas due to multi­photon ionization either with or without filamentation of radiation. As primary photoelectrons are quickly (~lO ns) attached to molecular oxygen, additional impact of visible or UV light should be further anticipated to keep the electron density for long enough time. Therefore, combination of a short intensive pulse followed by the long pulse seems to be the most attractive.

Here we present the current status of hybrid Ti:Sapphire/KrF laser facility GARPUN-MTW [7], which will be able soon to produce combined subpicosecond/IOO-nanosesecond UV laser pulses at wavelength 248 nm with

• This work is supported by Advanced Energy Technologies Ltd, Moscow, Russia.

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energies of ~ 1.5/1 00 J, respectively. The pilot experiments on triggering of high­voltage (HV) discharges over the length ~ I m are described being performed with long pulses. Photo ionization of some gases (air, N2, Ar) by long (~20 ns) or short (~100 fs) laser pulses was measured and probable ionization mechanisms are discussed.

2. Prospects for Ti:Sapphire/KrF laser Facility GARPUN-MTW

Hybrid Ti:Sapphire/KrF multiterawatt laser facility GARPUN-MTW [7] combines the previous version of e-beam-pumped multistage GARPUN KrF laser [8] with recently constructed Ti: Sapphire front-end "START-248 M". The final large-aperture GARPUN amplifier with an active volume of 16 x 18 x 100 cm3 is pumped by two-side counter-propagating 350-keV, 60-kA (50 A/cm\ 100-ns e-beams guided by magnetic field of ~0.08 T. It produces up to 100 J in 100-ns pulses when operating in free-running or injection-controlled operation modes. Another lOx lOx 11 0-cm3 BERDYSH module pumped by a single-side magnetic field-guided 350-keV, 50-kA (50 Alcm\ 100-ns e-beam produces up to 25 J in free-running oscillation. A high-voltage power supply of electron guns consists of two 7-stage Marx generators with 14 kJ (GARPUN) and 3.0 kJ (BERDYSH) energy storage at 500-kV pulsed voltage and five water-filled Blumlein pulse forming lines (PFLs) of 7.6 n wave impedance, which supply pulses of ~350 kV voltage to four cathodes in GARPUN's vacuum diodes and one cathode in BERDYSH module. All PFLs are synchronized by means of laser­triggered switches. KrF master oscillator (Lambda Physik EMG TMSC 150 laser) produces 200-mJ, 20-ns pulses, which are seeded into the unstable resonator of GARPUN module (in injection-controlled operation) or successively amplified in Berdysh and GARPUN amplifiers. Master oscillator is also used to fire the PFL's switches.

Ti:Sapphire front-end "START-248 M" (Avesta Project Ltd.) was designed to produce 0.5-mJ, 60-fs pulses at wavelength ;\=248 nm matched with KrF amplification band [7]. In recent experiments on successive amplification of 100-fs pulses in Berdysh (single pass) and GARPUN (double-pass) amplifiers output energy of 0.5 J was attained. The output pulse was broadened by spectral dispersion of laser windows and air along the amplification path up to ~500 fs, resulting in a peak power of the amplified pulse ~ I TW. Pulse duration as short as ~50 fs might be expected when negative spectral chirp will be introduced in ongoing experiments. Numerical simulations [7] predict that these short pulses can be amplified up to 1.5 J and combined together with long ones of 100-J energy and 100-ns duration.

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3. Guiding of High-Voltage Discharge by tOO-ns UV Laser Pulse

KrF laser beam

t=1 00 ns E=40-0,1 J AF248 nm

q_,mm

I lO~50'm if :::r: :::r: :::r:

C=0.03 ~F :::r: U=300-500 kV :::r:

Figure 1. Layout of experiments on HV discharge guiding.

Pilot experiments on HV discharge guiding were performed with GARPUN laser operating in injection-controlled

mode. Laser beam was focused by the lens (F=8 m) in a

discharge gap through a hole of 18-mm diameter in grounded electrode (Fig. 1). The latter was in the form of semi-sphere of 75-mm diameter, surrounded by a ring of 250-mm diameter to uniform electric field . The lens focal plane lied at the distance 112 to 113 of total inter-electrode gap L being counted off HV

electrode. Inter-electrode distance L was varied in experiments from 50 to 100 cm. HV

electrode in the form of semi-sphere of 30-mm diameter was connected with 7-stage Marx generator (pulsed capacitance C = 0.036 flF) capable to produce pulsed voltage U up to 500 kV.

Different discharge regimes are illustrated in Fig. 2. The time-integrated images were obtained with CCD camera for variable laser energy, inter-electrode gap, applied voltage and its polarity. For the highest laser energy Elas = 40 J in these experiments, pulse duration 'las = 75 ns at FWHM and beam diameter d ~ 1 mm in lens caustic of - lO-cm length laser intensity was J = Ela.J TtasClfcfl4) -7* 10 10 W Icm2

. At such intensity air breakdown did occur in the focal region even if no voltage was applied to the discharge gap. Its luminosity was rather weak compared with the electric discharge, which happened when breakdown voltage was applied. When positive pulsed voltage with U = 390 kV amplitude, 0.3 fls leading front and 4.5 fls decay time (see Fig. 3) was applied to the discharge gap with L ::; 50 cm a self-breakdown (without laser triggering) happened with 100% probability and its trajectory was occasional. For L =60 cm self-breakdown probability became rather low, while laser-triggered discharge happened with 100% probability, if laser pulse energy exceeded the threshold value of E!;\. = 40 m1. Partial discharge guiding along the laser beam was observed in the region of lens caustic in this case. Perfect electric guiding along

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the whole inter-electrode distance L =80 cm was achieved for higher energies. For negative applied voltage full-length guided discharge was attained at rather low laser energy Etas= 0.3 J, which corresponded to laser intensity in the lens focus ~5*108 W/cm2 and even lower out of the lens caustic. For L 2: 80 cm probability of discharge triggering at the given voltage U = 390 kY became low.

I, -I

- 11/

L=80 em E=Z5J U--O

L=80 em E=19.2J U=+390kV

L=60 em E=2S.6J U=+390kV

L=60 em E=O.17J U=+390kV

L=60 em E=O.044J U=+390 kV

L=60 em E=o.o30J U=+390kV

L=60 em

E=O.29J U--390kV

Figure 2. Time-integrated images of electric discharge at various experimental conditions.

Oscilloscope traces of laser pulse (I) and discharge current (2) are compared in Fig. 3 with applied voltage (3) (the latter pulse is shown for the case without discharge triggering). As laser pulse was delayed respective the beginning of voltage pulse by 2 Ils, instant value of the voltage fell down by ~20% compared with the maximal one. The discharge current arose with time delay r, which depended on applied voltage U, its polarity, inter-electrode gap L, and laser pulse energy Etas.

Time,f.J.ffi

Figure 3. Oscilloscope traces of laser pulse (I), discharge current (2) and applied voltage (without discharge triggering - 3).

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Time delay of electric discharge respective laser pulse in dependence on its energy is shown in Fig. 4. It is seen that for E/a\' ~ 10 J the delay of discharge does not exceed T ~ 0.1 Ils

independently on voltage polarity. For lower energies the delay grows rapidly, especially for positive polarity. Decrease of the voltage was apparently a significant reason why the discharge could not happen for laser energies below the threshold.

+

+

0.1

+ +

<>

+ + + Posith'r- pol.rl~'

<> <> <> Nt'glIUn polarity

+ + +

+

1 10 Lase-r pulse enCI'gy, J

817

Figure 4. Time delay of the discharge vs laser energy.

From discharge current oscillation period T=4 Ils, exponential damping time Tdee= 4.5 IlS, and known Marx generator capacitance C = 0.036 IlF both circuit inductance Le = 10 IlH and resistance Rc were found. The latter is a sum of resistances of Marx generator switches and connectors (they were measured to be 1.6 n in a short-circuited performance) and the discharge itself. Thus, the self-breakdown discharge and laser-triggered discharge resistances were determined in experiments being of 0.4-0.5 nand 0.2-0.4 n, respectively. The difference is apparently caused by variation in discharge trajectory lengths.

4. Measurements of Conductivity and Electron Density in Plasma Channels Produced by 20-ns UV Laser Pulse

Low-threshold discharge triggering and guiding indicates that high enough conductivity and density of electrons are produced by UV laser light in atmospheric air. The experiments were performed (Fig. 5) with KrF master oscillator to measure these values in dependence on laser intensity. Laser pulses with variable energy 5-200 mJ and 22-ns duration at FWHM were focused with various

I Laser "I Beam -=t

Oscilloscope C=500 pF

Rose Cose RJoad

T Figure 5. Layout of conductivity measurements.

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lenses (F = 0.5, 2 and 8 m) through ring electrodes (to eliminate a photoeffect) into inter-electrode gap I, which length was varied from 2 to 10 mm in adjustment with the lenses caustic lengths. A steady voltage Uo was applied to the gap. In all, laser intensity was varied in the range 3*106- 7*10 10 W/cm2 just below avalanche air breakdown for nanosecond UV pulses.

Laser pulse and different waveforms of voltage signals u(t) produced by ionization current i(t) on different oscilloscope load resistors R/oad and measured in different time scales are shown in Fig. 6 (a-d). For R/oad = 50 Q (a) and low­impedance oscilloscope input ROJc= 50 Q the signal u(t) = i(t)-R/oad is proportional to the current pulse with time resolution R/oacrRo",c"Co'\'cJ(R/oaa+RoJc) -2.5 ns (where Cose-IOO pF includes both oscilloscope input and measurement circuit capacitances), while for R/oad = I MQ (b) and high-impedance input Rosc= I MQ the signal is proportional to the current integrated over time - 50 fls .

t

mI 1. ~ 6-_ 20:40 <10Hz

(a) R/oad =50 0, 10 ns/div

.... .. ...... _.

, ... - . .. . "" ·11."".", ••• ,.,.,·"""" . . ..... ", .. ",· . . . - . . . .

IIIiI ,~~~~~~~~~~~~.~

<10Hz

(c) R /oad = 1 MO, 50 J,.ls/div

~~~~~~~~~~~~~ Action ... PRINT

.. . . . . ''': '' . .. .. , ... . , . ... Bulton

"""":"";"";")"";",,i,,,, ;,,,,;,, ... . Select FokIe,

Abwt Save All

~~~~~~~~~~~~'7~

2- .m-oo 16:35 <1(1iz

(b) R/oad =1 MO, 0.5 J,.ls/div

. ... j\ .. " ......... : .. .. j .... ; .... ! .. ": ......... Em

, . \-.-,,: .. .. . ..... II

IIIiI ~~~~~~~~~~~~.~

OIl <1(1iz

(d) R/oad = 1 MO, 500 J,.ls/div

Figure 5. Oscilloscope traces of laser pulse (CH I) and voltage signals produced by ionization

current on various load resistors (CH2) in different time scales.

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By analyzing the signals in Fig. 5 one can see that there were three current components with sufficiently different carrier mobility in a steady electric field Uol!: (i) the fastest one is synchronous with laser pulse and lasts slightly longer (a) - it is attributed to electrons; (ii) more slower component attains the maximum value by ~ 100 /lS - is attributed to positive or negative ions 0/, N/, Oz", and so on, being formed from the main air species oxygen and nitrogen in ionization and electron attachment processes; (iii) very slow component has a maximum at ~ 1 ms - it might be microscopic charged aerosol particles or very large cluster ions. The latter was removed if air flow was organized perpendicular to the discharge gap.

Let us pay attention to the electronic component. The simplified kinetic equations for electrons and negative oxygen ions can be written as:

aNe (k 2 2 Da 1 --=Se-Ne INo +k2NO NHO)-k3 Ne --2 Ne+-No·O-ph at 2 2 2 A hv 2

(I)

where Ne, No , No·' N HOare concentrations of electrons, oxygen molecules, 2 2 2

negative ions, and water vapor molecules, respectively. Se is a rate of electrons

generation in different ionization processes; klNb2 + k2N O2 N H20 ~ 108 S"l is

probability of electron attachment to oxygen molecule in normal atmospheric conditions and humidity.

Rate coefficients of three-particle electron attachment processes are kl~2.5* 10"30 cm6s"1 and kz~ 1.4* 10"29 cm6s"l; k3 ~ 1.3* 10"8 cm3s"1 is electron-ion recombination coefficient [9]; Do ~ 200 cmZs"1 is ambipolar diffusion coefficient, A = RI2.4, R is a radius of laser beam [10]; 1 and hv = 5 eV are intensity and energy quantum ofKrF laser; aph = 3*10"18 cmz is approximated cross section of electron photo-detachment off O2" by KrF laser radiation [11]. For KrF laser direct 3-photon ionization of O2 molecule (with ionization potential 1;=12.2 eV) is usually considered as a primary ionization process, as 4-photon ionization of Nz molecule (/;=15.6 eV) is significantly less probable [12,13].

From equations (1) one can estimate that for Ne :::; 1016 cm"3 the main mechanism of electrons losses in atmospheric air is their attachment to oxygen, which establishes a quasi-stationary concentration in competition with ionization. It is clearly seen in Fig.5a, where electron current follows laser pulse being slightly delayed. Photo-detachment partially suppresses attachment electrons losses at higher laser intensities 12': 3*107 W/cmz. Note that in pure nitrogen the attachment process does not take place and electronic current in

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experiments continued for few hundred nanoseconds after laser pulse termination.

From oscilloscope signals (Fig. 5a, b) specific electron conductivity CT. and electron density Ne in plasma channel were found by using the formulas

(2)

where S is a cross section area of laser beam, fie ~ 104 cm2y-1s-1 is electrons mobility in air [14]. Firstly, Ohm's law (proportionality i(t)IUo) has been proven.

The dependences of CTe

and Ne on peak laser intensity of laser pulse are shown in Fig. 6. For higher intensities /= 3*108_7*10 10 W/cm2

experimental dots are well approximated by the power law Ne ~ P that testifies to a two-step cascade ionization (2h v+h v) of O2 molecules through resonance excitation of intermediate highly-excited Rydberg levels . For direct 3-photon O2 ionization the slope should be steeper as shown by lines (1) and (2), being plotted by using the literature data [12, 13].

~ § i. ~ 1012

~

i 1011

ill

10'

Figure 6. Electron density and specific electron conductivity vs. laser intensity. Different dots correspond to various focus ing conditions; (I) and (2) are calculations for 3-photon ionization.

At lower /= 3*106-3*108 W/cm2 linear dependence Ne ~ / is observed that might be an ionization of impurity molecules with low ionization potential or photoemission from aerosol microscopic particles as discussed before. An influence of impurities on the conductivity has been confirmed experimentally: additives of some organic vapors (i.e. kerosene) to the air increased the ionization current by 3 orders of magnitude and was linear in the whole intensity range 3*106-7* 1010 W/cm2

. The similar effect was also observed in smoked atmosphere.

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5. Ionization of Gases by Intense Femtosecond UV Pulses

To establish ionization mechanisms for short UV pulses experiments were also performed with Ti:Sapphire front-end on nonlinear absorption and photoionization of argon [15] and nitrogen [16] by 100-fs pulses at 248-nm wavelength. Complementary studies were carried out by means of photogalvanic (a) and photo acoustic (b) techniques (Fig. 7) in the intensity range 1 = 3*101°-4*10 13 W/cm2

. Laser energy (maximum 0.4 mJ) was attenuated by combining various reflective dielectric mirrors (FM). The 6-mm diameter laser beam was

(a) SM u~ .~C) focused by a spherical mirror (SM) ~~ with F = 1 m into the gas-filled cell in ~~.OIOknJ· 2~' a focal volume of200 11m x 200 11m x

I'M 0.,,110"""'.... 1-1 10 mm. In some additional cases laser (b)

~ (d) intensity 1 was varied by translation of Ii the lens focus. Ion current (c) was

. ___ .~._)V! v'f." ~ lIS i' measured in the. discharge gap formed

O>cillo><op' by two semi-spherical electrodes with

Figure 7. Layout of photogalvanic (a) and 20-mm radii separated by 1= 3-5 mm. photoacoustic (b) measurements, typical DC voltage U = 0.4-3 kV was applied waveforms of current i(l) (c) and acollstic to the gap, which was perpendicular to pressure pet) (d): FM, SM are flat and spherical mirrors; U is applied voltage; K and M are laser beam, in difference with acoustic concentrator and microphone; PD is longitudinal geometry used for photodiode. nanosecond pulses.

Multi-photon gas ionization by femtosecond pulses caused an ambipolar drift of the resulting plasma cloud in applied electric field until it reached electrodes with 100-ns delay. The arrival of the plasma to electrodes initiated non-self-sustained discharge with current i(t) decay caused by plasma recombination. In the photoacoustic technique a [17] electrical signals (d) were acquired from capacitive microphone (M), which registered acoustic pressure P produced by gas photo-excitation in defocused laser beam and acoustically amplified in the cell by a concentrator (10.

Electric current i and pressure P peak values were measured in argon and nitrogen in dependence on peak laser intensities (Fig. 8). They were approximated by power laws with adjusted exponent indexes k. It is seen that for relatively low 1 = 3* 101°-8* I 011 W/cm2 photoacoustic measurements in argon give kac = 3.2±0.4 and in nitrogen kac = 3.0±0.1. Approximately the same values close to 3 were obtained with photogalvanic method: kef, I = 3.38±O.07 (in Ar)

a The authors are grateful to B.A Tikhomirov for performance of this technique.

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and kef,1 = 3.3±0,1 (in N2) It means that absorption ofUV quanta and ionization run like as 3-photon process, Three UV quanta of hv=5.0±0,02 eV energy even with accounting for the spectral width are not sufficient to ionize argon (Ii = 15.76 eV) and nitrogen (Ii = 15,6 eV) in a one-step action, A two step cascade process (3h v + h v) is required with an excitation of intermediate resonance Rydberg states that might be 4d [5/2] , J=3 (Eex=14.97 eV) state in argon [18] and b' I.E:, c' I.E: , c f IJ." 0 J fl." and H 3 (/Ju states in nitrogen [19].

Ar 10' 103

~

. ~ 102 K" '~ !

1\" .• ···· 3.38 ± 0.07

10" ,-=-----"--'---'--L..L-LW.'-,---'----' 10- ' 10-2 10-'

10'

I (TWicm' j

Nz

K.-3.0iO.1

K ... 1 " 3.3 t 0.1

lD''----~-~--~~...J 0.1

10'

Ar

10

( (TWlcmZ)

Nz

10" 5'--~~''''''0--~-~---'50

I (lW/cm') I (lW/cm')

Figure 8. Electric current and acoustic pressure amplitudes in argon (top graphs) and nitrogen (bottom graphs) vs. peak laser intensity in low (left hand graphs) and high intensity (right hand graphs) ranges. Approximations by power law are shown by solid lines with corresponding exponent indexes kac (for acoustic measurements) and kel, l or k el.2 (for electric measurements).

In contrast, in high-intensity range 3*10 12-4*10 13 W/cm2 i(I) curves increase steeper with I: kef,2 = 3.83±0.17 (in Ar) and kef,2 = 3,7±0.1 (in N2). Thus, exponent indexes are close to 4 that means direct non-resonant 4-photon ionization takes place in both gases. The transition from the cascade (3h v + h v)

to the direct 4-photon ionization at high intensities might be caused by dynamic Stark detuning of the resonance Rydberg states, along with effective ponderomotive shift of the ionization potentials.

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References

1. X.M. Zhao, Y.e. Wang, J.-e. Diels and J. Elizondo, IEEE J Quant. Electron. 31,599 (1995).

2. M. Chateauneuf, S. Payeur, J. Dubois and J.-C. Kieffer, Appl. Phys. Lett. 92, paper 091104 (2008).

3. T.P. Rowlands-Rees, e. Kamperidis, S. Kneip, et al., Phys. Rev. Lett. 100, paper 105005 (2008).

4. D.V. Koopman and T.D. Wilkenson, J Appl. Phys. 42, 1883 (1971). 5. V.D. Zvorykin, F.A. Nikolaev, LV. Kholin, et al., Phisika Plasmy 5, 1140

(1979) (in Russian). 6. S. Tzortzakis, M.A Franco, Y.-B. Andre, et al., Phys. Rev. E. 60, R3505

(1999). 7. V.D. Zvorykin, N.V. Didenko, AA lonin, et al., Laser and Particle Beams

25, 435 (2007). 8. N.G. Basov, V.G. Bakaev, AV. Bogdanovskii, et al., J Sov. Laser Res. 14,

326 (1993). 9. M. Miki and A Wada, J Appl. Phys. 80,3208 (1996). 10. Yu.P. Raizer, Gas Discharge Physics, Springer Verlag, 1997. 11. D.S. Burch, SJ. Smith and L.M. Branscomb, Phys. Rev. 112, 171 (1958). 12. J. Schwarz, P.Rambo and J.e. Diels, Appl. Phys. B 72,343 (2001). 13. N. Khan, N. Mariun, 1. Aris and J. Yeak, New Journal of Physics 4, paper

61 (2002). 14 L.G.H. Huxley and R.W. Crompton, The Diffusion and Drift of Electrons in

Gases, John Wiley & Sons, 1974. 15. V.D. Zvorykin, A.A. lonin, SJ. Kudryashov, et al., JETP Lett. 88, 10

(2008). 16. AA. lonin, S.L Kudryashov, Yu.N. Ponomarev, et al., Opt. Commun. 282,

45 (2009). 17. D.V. Kartashov, A.V. Kirsanov, A.M. Stepanov, et al., Opt. Express, 14,

7552 (2006). 18. CJ.G.J. Uiterwaal, D. Xenakis, D.Charlambidis, et al., Phys. Rev. A 57, 392

(1998). 19. LS. Grigor'ev and E.Z. Mel'nikov (Eds.), Physical Quantities,

Energoatomizdat, Moscow, 1991 (in Russian).

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