The paper presents results of the spectroscopic and corpuscular measurements of pulsed plasma streams generated within the RPI-IBIS experimental device, which was operated with the pure deuterium puffing. Particular attention was paid to time-integrated and time-resolved measurements of selected spectral lines, i.e. Da, Db and Dg, emitted from deuterium discharges. The measurements made possible an assessment of the basic plasma parameters. The achievement of the local thermal equilibrium (LTE) was investigated. Energies of emitted ions, their total numbers, as well emissions of soft X-rays and fusion-produced neutrons vary considerably with a change of gas conditions

Baranowski, J.

Czaus, K.

Pisarczyk, T.

Sadowski, M.J.

Skladnik-Sadowska, E.

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

CHARACTERISTICS OF HIGH-TEMPERATURE DEUTERIUM PLASMA IN RPI-TYPE DEVICESE. Skladnik-Sadowska1, J. Baranowski1, K. Czaus1, M.J. Sadowski1, and T. Pisarczyk 21 The Andrzej Soltan Institute for Nuclear Studies (IPJ), 05-400 Otwock-Swierk, Poland e-mail: eskladnik@ipj.gov.pl2 Institute of Plasma Physics and Laser Microfusion (IPPLM), 00-908 Warsaw, PolandThe paper presents results of the spectroscopic and corpuscular measurements of pulsed plasma streams generated within the RPI-IBIS experimental device, which was operated with the pure deuterium puffing. Particular attention was paid to time-integrated and time-resolved measurements of selected spectral lines, i.e. Dα, Dβ and Dγ, emitted from deuterium  discharges.  The  measurements  made  possible  an  assessment  of  the  basic  plasma  parameters.  The achievement of the local thermal equilibrium (LTE) was investigated. Energies of emitted ions, their total numbers, as well emissions of soft X-rays and fusion-produced neutrons vary considerably with a change of gas conditions.PACS: 52.70.-m; 52.30.-g1. INTRODUCTIONSpectroscopic  measurements  of  the  pulsed  plasma streams  deliver  important  information  about  dynamics and characteristics of the investigated plasmas. Studies of high-energy  ions,  which  are  emitted  from  plasma discharges, provide also information about dynamics of plasma  phenomena  and  mechanisms  of  the  charged particle  acceleration.  On the  other  hand,  spectroscopic and  corpuscular  measurements  are  of  importance  for various technological applications of plasma facilities.The pulsed plasma streams, generated by coaxial multi-rod  injectors,  so-called  RPI-  or  IONOTRON-type facilities, have been studied at IPJ for many years [1-3]. The  studies  performed  during  recent  two  years  shed some new light on the operation of such devices [4-7]. The main aim of this paper was to summarize the recent spectroscopic and corpuscular studies. 2. EXPERIMENTAL SETUPThe recent studies have been performed mainly within the  RPI-IBIS  facility  [5],  which  was  powered  from a current pulse generator charged to U0 = 30 kV, W0 = 33 kJ.  The facility  was equipped with a  set  of  diagnostic tools, as shown in Fig. 1. Fig. 1. Scheme of the RPI-electrode system with the basic diagnostic equipment.During the described experiments  the RPI-IBIS device was  operated  mostly  with  the  pure  deuterium puffing. Time-integrated  and  time-resolved  measurements  of selected  spectral  lines,  mainly  those  of  deuterium species,  were  performed  with  the  MECHELLE900 optical spectrometer equipped with an intensified CCD readout.  It  made possible  optical  measurements  within the wavelength range from 200 nm to 1100 nm, at an exposition time ranging from 100 ns up to 50 ms. Time-integrated and time-resolved measurements of ions were carried out by means of Faraday-type collectors and a  Thomson-type  mass-spectrometer.  In  order  to  record low-energy ions the Thomson spectrometer was equipped with  an  input  ion-acceleration  system.  The  time-integrated  measurements  were  performed  mainly  with the use of solid-state nuclear track detectors of the CR-39 type. 3. SPECTROSCOPIC STUDY OF PLASMA-ION STREAMSDuring the spectroscopic studies particular attention was paid to observations of the Balmer spectral lines of the working gas, i.e. Dα – 656.10 nm, Dβ – 486.029 nm and Dγ –  433.298  nm.  Some  spectral  lines  from  remnant gases  and  the  electrodes  (Mo)  were  also  observed,  as shown in Fig. 2. Fig. 2. Optical spectra of the pulsed plasma streams emitted from the IBIS-RPI facility, as recorded for shots at U0 = 30 kV, W0 = 33 kJ, D2 -puffing, t = 190 µs, with the spectrometer exposition equal to 5 µs and 100 µs.Problems of Atomic Science and Technology. 2002. № 4. Series: Plasma Physics (7). P. 123-125                  123400 450 500 550 600 65005000100001500020000250003000035000Mo396.61Mo392.95texp = 100 µ sτ  = 190 µ sRPI-IBIS-60D-gammaD-betaD-alphashot 02012804Intensity [a.u.]Wavelength [nm]400 450 500 550 600 6500200040006000800010000shot 02012805NΙ465.70OΙ Ι464.80D-gammaD-betaD-alphatexp = 5µ sτ  = 190µ sRPI-IBIS 60Intensity [a.u.]Wavelength [nm]A half-period of the discharge current was equal to about 7  µs, and the detection system of the spectrometer was usually  opened  with  a  time  delay  of  3  µs  after  the beginning of the current pulse, i.e. close to the current peak.  In  order  to  embrace  the  characteristic  current peculiarities,  several  series  of  the  observations  were performed with the spectrometer exposition equal to 5 µs.  Other  measurements  were  carried  out  with  the exposition of 100  µs, i.e. practically as time-integrated. On  the  basis  of  the  spectrum  recorded  with  the  5-µs exposition it was estimated that an average deuterium ion temperature amounted to about 1 keV. It was also found that the impurity lines from the electrode material (Mo) appear during later phases of the discharge. To  study  influence  of  the  initial  gas  conditions,  the detailed spectroscopic measurements were performed at different time delays (τ) between the gas puffing and the application of the voltage (current) pulse. FWHM values of selected spectral lines were measured at the different operational conditions, as shown in Fig. 3.Fig 3. FWHM values as a function of the time delay, as measured for the described experiment with the spectrometer exposition equal to 5 µs and 100 µs.Those measurements confirmed a strong dependence of the  plasma  parameters  on  the  initial  gas  conditions, varied by a change of the delay time (τ). A selection of the optimal operational conditions could be performed on the basis of the observation of the selected spectral lines. The  intensity  and  widening  of  Dβ line  was  evidently largest at the time delay τ = 190 µs, as shown in Fig. 4. The time delay  τ = 190 µs corresponds to the so-called medium operational-mode, when a role of  the remnant gases seems to be negligible (see Fig. 4). The finding that the  ions  from  the  electrode  material  appear  in  later phases of the discharge, is of particular importance for technological applications of the RPI devices.Fig. 4. Intensity of the spectral lines vs. the time delay,  as measured for the chosen spectrum part (near Dβ line)  at the exposition time equal to 5 µs.4. MASS-AND ENERGY-ANALYSIS OF IONSTime-integrated  measurements  of  the  investigated plasma-ion streams were performed with the Thomson-type  spectrometer  adjusted  along  the  z-axis.  It  was equipped with the input ion-acceleration system and CR-39 nuclear-track detectors, as described above. Thomson parabolas, which were visible on the track detectors after their appropriate etching, were analyzed with an optical microscope. To perform an accurate analysis of the ion tracks,  the  use  was  made  of  an  automatic  system consisted  of  a  CCD  camera  coupled  with  a  fast  PC (Pentium II) equipped with the Image-Pro-Plus software. That analysis enabled a dependence of track diameters on their mass and energy to be found. It determined also the energy distribution  of  the accelerated  primary  protons, deuterons and nitrogen ions, as shown in Fig. 5.Fig. 5. Energy spectra of deuterons, protons and nitrogen ions, as determined on the basis of  measurements performed with the Thomson mass-spectrometer. Bars show the experimental errors.The protons and nitrogen ions originated evidently from the remnant gases, which were occluded or absorbed in the  electrodes  used  before  in  experiments  with  other working gases.124140 160 180 200 220 240 2600,00,51,01,52,02,53,03,5D-alphashots 020128/01,02,05,06,09RPI-IBIS 60D-betaD-gammatexp= 5µ sFull width at half maximum FWHM [nm]Dalay time τ  [µ s]140 160 180 200 220 240 2600,00,51,01,52,02,53,03,5D-betaD-gammaD-alphashots 020128/08, 04,03,07texp=100µ sRPI-IBIS 60Full width at half maximum FWHM [nm]Delay time τ  [µ s]100 1000110100 x10620nitrogen ionsprotonsdeuteronsNi/Ei [ions/cm2  MeV]Energy of ions Ei [keV]Analyzing ion-spectrum from various shots, which were performed with the deuterium puffing at different time delays (τ), it was possible to determine average energy values and the total numbers of the emitted deuterons, as shown in Fig. 6.Fig. 6. Average energy values <E> and total numbers of  deuterons (ND) emitted from the deuterium discharges  within IBIS-RPI device..5. MEASUREMENTS OF NUCLEAR FUSION PRODUCTSDuring experiments performed with the pure deuterium puffing,  the  RPI-type  facilities  can  also  emit  fusion-produced neutrons and protons. In order to determine the optimal  operational  conditions,  the  neutron  yield measurements  have  been  carried  out  at  different  time delay times (τ), as shown in Fig. 7.Fig. 7. Average neutron yield <Yn> from pure deuterium discharges within IBIS-RPI device, as a function of the time delay (τ ) between the deuterium puffing and the application of a voltage/current pulse.The  detailed  measurements  have  also  shown  that  the energy  spectrum  of  fusion-produced  protons  depends considerably on the initial  gas conditions  within IBIS-RPI facility, as shown in Fig. 8. 6. SUMMARY AND CONCLUSIONSThe results of this work can be summarized as follows:- The  recent  spectroscopic  studies,  as  performed within  IBIS-RPI device,  have confirmed a strong dependence of  plasma characteristics on the initial gas conditions (varied by changing a time delay τ).Fig. 8. Typical energy spectra of fusion-reaction protons emitted from IBIS-RPI device operated with the pure deuterium filling.- A considerable delay in the emission of metal ions, which  originate  from  the  electrode  material,  has been  proved.  It  appeared  to  be  of  particular importance  for  technological  applications  of  RPI-type devices.- Time-integrated measurements of ions, which were performed with pinhole cameras and the Thomson-type analyzer, have determined a dependence of ion yields and energies on the initial gas conditions. - Ion measurements have also shown that the average energy value of deuterons varies from about 70 keV down to a  few keV with an increase  in  the  delay time  τ,  while the total number of deuterons is  the highest at a delay time τ = 170-190 µs.- It was confirmed that the RPI-type devices produce also  fusion  products  (fast  neutrons  and  protons), depending on the operational mode.One  might  conclude  that  further  spectroscopic  studies should be performed with shorter exposition times (e.g. 100-200  ns)  during  over-voltage  pulse  and  discharge-current  peculiarities.  In  further  ion  studies  particular attention should be to heavy ions emitted from the rod electrodes.REFERENCES1. M.Gryzinski,  J.Nowikowski,  M.Sadowski, S.Suckewer: Nukleonika 13 (1968) 719.2. E.Skladnik-Sadowska,  J.Baranowski,  M.Gryzinski, J.Langner, M.Sadowski: J. Physique 43 (1982) 715.3. J.Baranowski,  M.Sadowski,  E.Skladnik-Sadowska, J.Stanislawski, J.Zebrowski:  Proc. ICPP’98 (Praha, 1998); ECA Vol. 22C  (1998) 1662.4. J. Baranowski, K. Czaus, M. Sadowski, E.Składnik-Sadowska  and  A.Tsarenko: Proc. 27th EPS  Conf.  CFPP (Budapest 2000); ECA Vol. 24B (2000) 848.5. E.Skladnik-Sadowska,  J.Baranowski,  K.Czaus, M.J.Sadowski,  A.Tsarenko:  Probl.  Atom.  Sci.  & Techn. 6, Plasma Ser. 6 (2000) 169.6. J.Baranowski,  E.Skladnik-Sadowska,  K.Czaus, M.Sadowski:  Proc.  Int.  Symp.  PLASMA-2001 (Warsaw 2001) Paper P8.3.1252,50 2,75 3,00 3,25 3,50 3,750,00,51,01,52,0x105τ = 290 µ s, φ=0oNp=2.06x105 [cm-2]δ E= 150 keVτ = 200µ s, φ =0oNp=2.86x105 [cm-2]δ E= 250 keVN p/Ep [protons/cm2 MeV] Energy of protons  Ep [MeV]7. E.Skladnik-Sadowska,  J.Baranowski,  K.Czaus, M.J.Sadowski,  T.Pisarczyk:  Proc.  20th  SPPT (Prague 2002); Czech.  J. Phys.  52, Suppl. D (2002) D182.126

Characteristics of high-temperature deuterium plasma in RPI-type devices

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Characteristics of high-temperature deuterium plasma in RPI-type devices

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