The opportunity of use self-maintained plasma-beam discharge in an extended pulsing plasma diode of low pressure

for making powerful sources of the soft X-rays is investigated. Conditions of formation of the self-maintained plasmabeam

discharge are determined. The mode of making of dense high-temperature plasma on the basis of stannum ions in

the discharge is shown. The stannum ions are used as a working element of a radiation sources at pulsing power of

electron beam Ɋ~10…100 MW. Results of the examination on formation of the dense (np~1016

 cm

3

), small sizes

(l<1 cm) plasma with the electron temperature Ɍe~100 eV in conditions of working material evaporation from the anode

are given. The total contribution of energy to the discharge has made W < 20 J

Borisko, V.N.

Lazurik, V.T.

Tarasov, I.K.

Tseluyko, A.F.

Zinov’ev, D.V.

Наукова електронна бібліотека періодичних видань НАН України (Vernadsky National Library of Ukraine)

Problems of Atomic Science and Technology. 2006, ? 6. Series: Plasma Physics (12), p.  225-227 225THE FORMATION OF THE LOW-SIZED HIGH DENSITY PLASMASTRUCTURES IN THE SELF-MAINTAINED PLASMA-BEAM DISCHARGEV.N. Borisko1, A.F. Tseluyko1, D.V. Zinov’ev1, V.T. Lazurik1, I.K. Tarasov21V.N.Karazin Kharkov National University, Kurchatov av. 31, Kharkov, 61108, Ukraine,e-mail: Zinoviev@htuni.kharkov.ua;2Institute of Plasma Physics, National Science Center “Kharkov Institute of Physics andTechnology”, Academicheskaya str. 1, Kharkov, 61108, UkraineThe opportunity of use self-maintained plasma-beam discharge in an extended pulsing plasma diode of low pressurefor making powerful sources of the soft X-rays is investigated. Conditions of formation of the self-maintained plasma-beam discharge are determined. The mode of making of dense high-temperature plasma on the basis of stannum ions inthe discharge is shown. The stannum ions are used as a working element of a radiation sources at pulsing power ofelectron beam? ?~10…100 MW. Results of the examination on formation of the dense (np~1016 cm3), small sizes(l<1 cm) plasma with the electron temperature ?e~100 eV in conditions of working material evaporation from the anodeare given. The total contribution of energy to the discharge has made W < 20 J.PACS: 537.52INTRODUCTIONNow progress in the area of nano-technology is boundup with development of a photolithography which isbased on use of radiation with wave length ? ~ 10nanometers. In this case the specific optical systems andintensive point sources of radiation are used. As aradiating element for radiation sources the dense plasma(np ~ 1016…1018 cm3) with the electron temperature?? ~ 50…100 eV is used frequently. High electrontemperature is necessary for obtaining of multiply ionizedions which at the subsequent recombination form theradiation in a necessary range.One of problems, which arises at the creation of soft X-radiation sources for a photolithography in nano-dimensional area, is the big impulse energy contribution(W ~ 104…106 J) in devices which are used for this purposenow (pinch [1-3] and plasma accelerators [4]). The attemptto increase of the radiated power in these devices results tovery large thermal loadings on constructional elements andto quick destruction of these elements.For decrease of energy, which is brought to a dischargecell, in this work the opportunity of formation low-sizedhigh-temperature plasma under the action of self-maintainedplasma-beam discharge (SMPBD) is investigated [5].The presence in plasma, which transfers a currentthrough a discharge gap, the double electric layer of aspace charge with large voltage drop is the feature of suchdischarge. In a double layer there is a counter accelerationof powerful electron and ion beams. Between doublelayer and anode the discharge current is transferred by theelectron beam. Thus there is an intensive heating ofplasma due to collective beam-plasma interacting.Under conditions (Fig. 1) when the dense plasma HDHPis formed in the near anode area of the discharge, and doublelayer DL is localized on the external boundary of thisplasma, it is possible to carry out the effective heating of thedense plasma. Thus, the dense plasma can be created by thesame electron beam due to vapor ionization of the anode. Inthis case one part of the beam energy goes on theevaporation of the anode material, and other part - on aheating of plasma up to necessary temperature.Fig. 1. The scheme of discharge area (?) and qualitativelongitudinal distribution of potential ? (z) in thedischarge (b): C - cathode; A - anode; I - isolator;LDCP - love temperature plasma; DL - double layer;HDHP - dense high-temperature plasma; Vd - potential ofthe discharge; VDL - double layer potential;EB - electron beam; IB - ion beamBecause of a small amount of channels forconsumption of energy in a discharge cell, the use ofSMPBD can reduce the energy contribution to systemessentially. It opens up the prospects for creation ofeffective dot source of the soft X-rays.Important moment at the creation of a source ofradiation on the basis SMPBD is search of ways of hold-in the double layer in the near anode area.THE SHAME OF THE EXPERIMENTALDEVICEExperiments on formation of small size hightemperature plasma in conditions of SMPBD were carriedout in the extended pulse plasma diode of low pressure.The shame of the diode is shown on Fig. 2.HDHPLDCP DL? AI?Vd?(z)zVDL0IBEBb226Fig. 2. The shame of the experimental deviceThe plasma diode consists of the cathode C and theanode A, which are located in the center of the vacuumchamber to provide the large distance to its walls (~20 cm).The cathode was a tubular copper electrode (length is30 mm, external diameter is 10 mm and internal diameter is9 mm). Inside of the cathode in the ceramic isolator theconical copper trigger electrode IE by length 30 mm anddiameter at the basis 5 mm is located. The rod copper anodeA has diameter 4 mm. The lateral surface of the anode isprotected by glass tubular isolator. Working surfaces of allelectrodes have been covered by a stannum layer withthickness of 0,5 mm. The distance between end-walls ofcathode and anode could be changed from 3 up to 10 cm.For decrease of the inductance of a discharge circuitthe switching device was not used. The cathode and theanode directly connected to the battery of pulsecondensers Cp with capacity of 0,5…2,0 mF which wascharged from the power supply +Vd up to a voltage1…15 kV. The anode was as a high-voltage electrode, andthe cathode have the ground potential. The discharge wasignited with the help of a trigger electrode due to electricbreakdown on a surface of dielectric inside the tubularcathode. The voltage to trigger electrode yielded throughthe switchboard S from the battery of condensers Ci withcapacity 0,25…1,5 mF. The condensers were charged fromthe power supply +Vi up to a voltage 1…5 kV. With thehelp of inductance Li the duration and the current of atrigger pulse changed.For definition of localization of a double layer twomovable single probes ?1 and ?2 which registered theplasma potential were used. Besides that, with the help ofprobes the speed of expansion of the initial plasma wasdefined. Signals from the probes were stored by means ofcapacitor dividers of a voltage with the effective capacity~1 pF.THE EXPERIMENTAL RESULTSThe investigations were carried out at the residual gaspressure ?~10-5 torr when the basic working environmentfor the maintenance of the discharge is the stannumvapours. On Fig. 3 the oscillograms of a discharge currentand a discharge voltage, and probe potentials (?? = 1 mF,+Vd = 6 kV, Ci = 1,5 mF,  +Vi = 4 kV, Li = 7 mH) areshown.The experiments have shown that the formation ofsmall-size high-temperature plasma in the system occursin three stages.Fig. 3. Oscillograms of discharge current 1) - 5 kA/div,discharge voltage; 2) - 2 kV/div., and also probepotentials located on distance of 2 cm; 3) - 2 kV/divand 1 cm; 4) - 2 kV/div from the cathode.a) - sweep 5 msec/div; b) - sweep 1 msec/divAt the first stage (0 < T1 < 10 ms, Fig. 3a) the densecathode plasma is formed due to surface breakdown andextended to the anode direction. At that the mode of thevacuum diode with the plasma emitter of electrons takesplace. The electron beam, which is formed in an intervalbetween the front of cathode plasma and the anode,bombards of the anode surface and causes occurrence ofstannum vapours in the anode area. The beam intensityand intensity of evaporation of the anode material growwith the approach of cathode plasma front to the anode.The first stage Duration is defined by speed of extensionof cathode plasma vf, which was ~106 cm/s according toprobe measurements.The second stage of the discharge evolution comesafter shorting of the discharge gap by cathode plasma(10 < T2 < 23 ms). At that in the discharge gap filled byplasma a double layer forms. At first (10 < t21 < 12 ms)one double layer CDL formed near the cathode area. Totalvoltage drop of the discharge concentrated on this layer(VCDL » Vd). Then (12 < t22 < 14 ms) one more doublelayer ADL is formed near the anode area. Voltagebetween the layers is progressively redistributed. DuringVp1 Vp2+Vi+VdVdCiIdCoIELiACP1 P2Sab227time 14 < t23 < 23 ms in the discharge there are twoconsistent double layers with voltage drop VCDL » 1,5 kVand VADL » 4,5 kV.At the second stage the electron beam which is ignitedin a layer near the anode, prolongs to evaporate and ionizethe anode material intensively. It results to formation ofdense plasma. The layer in the cathode area heats up otherplasma of the discharge gap.After creation of the dense hot plasma on the basis ofstannum vapors in the discharge gap the third stage therecomes. At this stage the inductive discharge occurs(23 < T3 < 25 ms), and the discharge voltage isredistributed on inductance of a discharge circuit.However, during the period (23,4 <t31 < 23,8 ms) in thedischarge there is a layer in the anode area again. Theelectron beam with a current 6 kA heats up the anodeplasma to a level when it is capable to provide the currentdensity to the anode jA » 70 kA/cm2. The characteristicsizes of dense plasma in anode area are commensurablewith the sizes of the anode working surface.CONCLUSIONSAs a result of experiments the opportunity to useSMPBD for formation of the small-sizes high-temperaturedense plasma on the basis of stannum ions in anode areaof the extended plasma diode is shown. For effectiveevaporation of the anode material, vapour ionization andcollective hitting of plasma the opportunity of generationof the electron beam in the double layer of a space chargenear to a anode working surface is present. Forconfinement of a double layer in the anode area theseveral conditions is necessary to carry out. First, thepower supply should provide current Io greater, than athermal current of plasma in the field of a minimum ofconductivity:( )( )( )( )( )sdmtrTtrnesdtrjIeetSptSorrrrrr××»×> òò p,84,,min,where S (t) - external border of dense anode plasma.Second, the minimum of density of the basic plasma( )trnp ,minr  of the discharge gap should be near externalborder of the dense plasma S (t).For decrease of sizes of dense plasma it is necessary toreduce of the anode working surface.This work has been supported STCU Project # 3368.REFERENCES1. Borisov V.M. et al.// Plasma Physics. 2002, v.28,?10, p. 952-956 (in Russian).2. Usenko P.L. et al.// Priboru i tehnika experimenta.2002, ?3, p.93-100 (in Russian).3. G. Niimi et al.// J. Phys. D. Appl. Phys. 2001, v. 34,p. 1-4.4. S. Hussain, S. Ahmad et al.// Physics Letters. 2006,v.349, Iss. 1-4, p. 236-244.5.  E.I. Lutsenko, N.D. Sereda , A.F. Tselujko// Journalof Technical Physics. 1988, v.58, ? 7, p. 1299-1309.????????????? ????????????? ?????????? ??????????????????? ???????????????????????????????????????????????????????. ???????, ?? . ???????, ???. ????????, ???. ???????, ???. ??????????????? ???????????? ?????????????? ????????????????? ???????????????????? ???????? ?? ?????????????????????? ??????????? ?????? ???????? ????????? ???? ????????? ??????? ??????????? ???????? ???????????????????????. ??????????? ???????? ?? ???????? ??????? ????????????? ?? ?????? ???????? ??????????????????????????? ??????? ??? ??????? ?????? ?????? ???? ????????? ????????? ?????????? ?????????? ?????????????? ????????? ????????????? ????? ?~10¼100 ???. ?????????? ??????????? ????????????? ??????????????? ????????????? (l<1 ??) ??????? (np~1016???-3) ??????????? ????????? ?? ?????????????????????? ??~100 ???????????????????????????????????????????????????????????????????????????W<20 ??.??????????? ????????????? ????????? ???????????????? ??????????????????????? ??????????????????????????? . ???????, ?? . ???????, ???. ????????, ???. ???????, ???. ?????????????????? ??????????? ????????????? ????????????? ??????????????????? ???????? ?? ?????????????????????? ??????????? ?????? ????????? ?????? ???? ?????????? ????????? ??????? ???????? ?????????????????????????????. ?????????? ?????? ??? ?????????? ??????? ??????????? ?? ??????? ???????? ?????????????????????????? ??????? ??? ??????? ?????? ?????? ?? ??????? ????????? ????????? ???????? ????????????????????????????? ??????????? ????????????? ????? ?~10¼100 ???. ????????? ??????????? ??????????? ?? ??????????????????????? (l<1 ??) ??????? (np~1016???-3) ?????????? ????????? ?? ????????????? ?????????? ??~100 ??? ???????????????????????????????????????????????????????????????????W<20 ??.

The formation of the low-sized high density plasma structures in the self-maintained plasma-beam discharge

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Наукова електронна бібліотека періодичних видань НАН України (Vernadsky National Library of Ukraine)