COIL operation with COIL operation with iodine atoms generated in iodine atoms generated in a glow dischargea glow discharge

P.A. MikheyevP.A. Mikheyev, V.N. Azyazov, M.V. , V.N. Azyazov, M.V. Zagidullin, N.I. Ufimtsev, N.A. Khvatov, A.I. Zagidullin, N.I. Ufimtsev, N.A. Khvatov, A.I.

Voronov.Voronov.Samara Branch of P.N. Lebedev Physical Institute,Samara Branch of P.N. Lebedev Physical Institute, RussiaRussia

MotivationMotivation

II22 dissociation consumes ~10% of singlet dissociation consumes ~10% of singlet oxygen molecules. oxygen molecules.

II22 molecules are fast I* quenchers. molecules are fast I* quenchers. If iodine atoms are used instead of molecules If iodine atoms are used instead of molecules

it could increase COIL chemical efficiency up it could increase COIL chemical efficiency up to 40% to 40%

Madden et al 1998. Proc. of the Int. Conf. on Lasers '9Madden et al 1998. Proc. of the Int. Conf. on Lasers '988..

Carroll et al 1999. Proc. of the Int. Conf. on Lasers '99, p. Carroll et al 1999. Proc. of the Int. Conf. on Lasers '99, p. 6969..

Creating atomic iodineCreating atomic iodine

Electric discharge – most popularElectric discharge – most popular Chemical reactionsChemical reactions II2 2 thermal dissociation (>1200 ˚K)thermal dissociation (>1200 ˚K)

Carroll et al 1999 Proc. of the Int. Conf. on Lasers '99, p. Carroll et al 1999 Proc. of the Int. Conf. on Lasers '99, p. 6969..

HistoryHistory

First experiments with CW COIL: CW discharges with First experiments with CW COIL: CW discharges with II22 as the precursor in He carrier, RF and as the precursor in He carrier, RF and microwave discharges. Power enhancement at microwave discharges. Power enhancement at low [Ilow [I22], no enhancement at optimal [I], no enhancement at optimal [I22], ], incomplete Iincomplete I2 2 dissociation.dissociation.

Endo et al 2000. Jpn.J.Appl.Phys. Endo et al 2000. Jpn.J.Appl.Phys. 3939, 468; , 468; Wakazono et al 1998. Proc. SPIE. v. 3574, 290Wakazono et al 1998. Proc. SPIE. v. 3574, 290

Recent historyRecent history

DC discharge generation of iodine atoms in DC discharge generation of iodine atoms in supersonic COIL resulted in increase of Isupersonic COIL resulted in increase of I22 dissociation rate.dissociation rate.

Barmashenko et al 2007. Appl. Phys. Lett., 2007, Barmashenko et al 2007. Appl. Phys. Lett., 2007, 9090, , 161611112222..

Chemical technique of iodine atom Chemical technique of iodine atom generation and experiments with the generation and experiments with the supersonic COIL. No improvement in supersonic COIL. No improvement in chemical efficiency. chemical efficiency.

Špalek et al 2004. Proc. Špalek et al 2004. Proc. SPIE. v. 5777, 181SPIE. v. 5777, 181..

II22 dissociation and dissociation and recombinationrecombination

50-80% I50-80% I22 dissociates in MW & RF dissociates in MW & RF discharges, decreases with [Idischarges, decreases with [I22]]

Endo et al 2000. Jpn.J.Appl.Phys. Endo et al 2000. Jpn.J.Appl.Phys. 3939, 468, 468

Quillen and Schall 2003. COIL R&D Workshop, StuttgartQuillen and Schall 2003. COIL R&D Workshop, Stuttgart

Due to residual [IDue to residual [I22] the rates of recombination ] the rates of recombination

I+I+M I+I+M I I22+M (buffer gas)+M (buffer gas)

I+I+II+I+I22 2I 2I22

may be comparable at ~350 ˚Kmay be comparable at ~350 ˚K

CHCH33I as a precursorI as a precursor

Vapor: 400 Torr at room temperatureVapor: 400 Torr at room temperature Successfully used in laser experiments beforeSuccessfully used in laser experiments beforeVagin et al 1995. Quant. Electron. Vagin et al 1995. Quant. Electron. 2525 746 746..

DC discharge is less stable with IDC discharge is less stable with I22

I+I+M I+I+M I I22+M+M

MM k, cmk, cm66//c; 350 c; 350 KK

ArAr 5.35.31010‑33‑33

CHCH33II 2.52.51010‑31‑31 II22 1.1.881010‑30‑30

I recombination in the I recombination in the presence of CHpresence of CH33I and II and I22

PAr – 20 Torr

[I]+2[I2] – 1016 cm-3

[CH3I] – 1016 cm-3

[I2] – according to

initial degree of

dissociation

CHCH33I as a precursorI as a precursor

Ar found to be the best carrier for a DC Ar found to be the best carrier for a DC glow discharge ~50% of iodine was glow discharge ~50% of iodine was extracted out of CHextracted out of CH33I I

Mikheyev et al 2002. Quant. Electron. Mikheyev et al 2002. Quant. Electron. 32,32, 1 1

80%[I]+20%[I80%[I]+20%[I22] at the outlet of the glow ] at the outlet of the glow discharge generatordischarge generator

Azyazov et al 2009. Quant. Electron. Azyazov et al 2009. Quant. Electron. 39,39, 84 84

Output of the electric Output of the electric discharge iodine discharge iodine generatorgenerator

-6 -4 -2 0 2 4 60

1

2 a)C

once

ntr

atio

ns,

1016

cm

-3

Time, ms

CH3I HI

H2 CH

4

C2H

6 CH

3*10

A V Demyanov, I V Kochetov, A P Napartovich, V N Azyazov and P A Mikheyev

Study of iodine atoms production in Ar/CHStudy of iodine atoms production in Ar/CH33I dc glow dischargeI dc glow discharge Plasma Sources Science and Technology 19 (2010) 025017

Experiment: CHExperiment: CH33I as a I as a precursorprecursor

Decay rates of COIL Decay rates of COIL active medium with active medium with dependence on [I*] at dependence on [I*] at the I* peakthe I* peak

The rate of [OThe rate of [O22((11)])] removal was ~30% removal was ~30% smaller, with iodine smaller, with iodine produced from CHproduced from CH33I. I. 50%[I]+50%[I50%[I]+50%[I22] ] mixture injectedmixture injected

Mikheyev et al 2006. Proc. Mikheyev et al 2006. Proc. SPIE V.6346, 63460JSPIE V.6346, 63460J

Mikheyev and Azyazov 2008. Mikheyev and Azyazov 2008. J. Appl. Phys., J. Appl. Phys., 104,104, 123111 123111

0

500

1000

1500

2000

2500

3000

0 2 4 6 8 10

[I*], 1014cm-3

1/, s-1

CH3I

I2

CH3I_1

I2_1

Coaxial DC discharge iodine Coaxial DC discharge iodine generator with a segmented generator with a segmented cathodecathode

670 Ω each -

+

Ar/CH3I

Stainless steel

Thermo stabilized at 350 ˚K

DC discharge iodine DC discharge iodine generator with a segmented generator with a segmented cathodecathode

Iodine outputIodine output

power Discharge

rate flow I kJ/mole 234

Efficiency

In a good agreement with the model predictions

Idischarge – 2 A

COIL with the DC discharge COIL with the DC discharge iodine generator and the iodine generator and the centrifugal SOGcentrifugal SOG

Flow rates, mmole/s:Cl2 – 6.5;Primary He – 11;Secondary Ar – 3.5;CH3I – 0.1-0.2.

H2O/O2 – 0.15.

Pressure in the resonator – 8 Torr.

Teflon iodine duct and rake-type injector

OO22((11∆) + iodine flows∆) + iodine flows

With iodine generated in the electric discharge generator

With I2 without electric discharge

COIL power outputCOIL power output

Dependence of laser output upon iodine flow rate

ConclusionsConclusions

The cw COIL operation with external production The cw COIL operation with external production of of iodine atoms in CHiodine atoms in CH33I/Ar dc glow dischargeI/Ar dc glow discharge has has been demonstrated for the first time.been demonstrated for the first time.

Four times increase of laser output was Four times increase of laser output was observed in experimental conditions observed in experimental conditions unfavorable for a conventional COIL due to high unfavorable for a conventional COIL due to high water content and increased pressure in the water content and increased pressure in the resonator.resonator.

The results prove that a substantial amount of The results prove that a substantial amount of iodine atoms had been transported to the iodine atoms had been transported to the injection point.injection point.

The products of methyl iodide dissociation have The products of methyl iodide dissociation have little or no adverse effect on COIL performance.little or no adverse effect on COIL performance.