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1

Studies of plasma interactions with tungsten targets in PF-1000U facility

Ladygina M. S., Skladnik-Sadowska E., Zaloga D. R., Sadowski M. J., Kubkowska M., Kowalska-Strzeciwilk E., Krawczyk N., Paduch M., Miklaszewski R., Garkusha I. E.

Nukleonika

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2016

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Vol. 61, No. 2

149--153

EN

This paper presents results of experimental studies of tungsten samples of 99.95% purity, which were irradiated by intense plasma-ion streams. The behaviour of tungsten, and particularly its structural change induced by high plasma loads, is of great importance for fusion technology. The reported measurements were performed within a modifi ed PF-1000U plasma-focus facility operated at the IFPiLM in Warsaw, Poland. The working gas was pure deuterium. In order to determine the main plasma parameters and to study the behaviour of impurities at different instants of the plasma discharge, the optical emission spectroscopy was used. The dependence of plasma parameters on the initial charging voltage (16, 19 and 21 kV) was studied. Detailed optical measurements were performed during interactions of a plasma stream with the tungsten samples placed at the z-axis of the facility, at a distance of 6 cm from the electrode outlets. The recorded spectra showed distinct WI and WII spectral lines. Investigation of a target surface morphology, after its irradiation by intense plasma streams, was performed by means of an optical microscope. The observations revealed that some amounts of the electrodes material (mainly copper) were deposited upon the irradiated sample surface. In all the cases, melted zones were observed upon the irradiated target surface, and in experiments performed at the highest charging voltage there were formed some cracks.

2

Research on interactions of plasma streams with CFC targets in the Rod Plasma Injector facility

Zaloga D. R., Kwiatkowski R., Skladnik-Sadowska E., Sadowski M. J., Nowakowska-Langier K.

Nukleonika

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2016

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Vol. 61, No. 2

179--183

EN

This paper present results of optical spectroscopy studies of interactions of intense plasma streams with a solid target made of carbon fibre composite (CFC). The experiments were carried out within the Rod Plasma Injector (RPI) IBIS facility. The optical measurements were performed first for a freely propagating plasma stream in order to determine the optimal operational parameters of this facility. Optical emission spectra (OES) were recorded for different operational modes of the RPI IBIS device, and spectral lines were identified originating from the working gas (deuterium) as well as some lines from the electrode material (molybdenum). Subsequently, optical measurements of plasma interacting with the CFC target were performed. In the optical spectra recorded with the irradiated CFC samples, in addition to deuterium and molybdenum lines, many carbon lines, which enabled to estimate erosion of the investigated targets, were recorded. In order to study changes in the irradiated CFC samples, their surfaces were analysed (before and after several plasma discharges) by means of scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) techniques. The analysis of the obtained SEM images showed that the plasma irradiation induces noticeable changes in the surface morphology, for example vaporisation of some carbon fi bres and formation of microcracks. The obtained EDS images showed that upon the irradiated target surface, some impurity ions are also deposited, particularly molybdenum ions from the applied electrodes.

3

Study of tungsten surface interaction with plasma streams at DPF-1000U

Ladygina M. S., Skladnik-Sadowska E., Zaloga D. R., Malinowski K., Sadowski M. J., Kubkowska M., Kowalska-Strzeciwilk E., Paduch M., Zielinska E., Miklaszewski R., Garkusha I. E., Gribkov V. A.

Nukleonika

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2015

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Vol. 60, No. 2

293--296

EN

In this note experimental studies of tungsten (W) samples irradiated by intense plasma-ion streams are reported. Measurements were performed using the modified plasma focus device DPF-1000U equipped with an axial gas-puffing system. The main diagnostic tool was a Mechelle®900 optical spectrometer. The electron density of a freely propagating plasma stream (i.e., the plasma stream observed without any target inside the vacuum chamber) was estimated on the basis of the half-width of the Dβ spectral line, taking into account the linear Stark effect. For a freely propagating plasma stream the maximum electron density amounted to about 1.3 × 1017 cm–3 and was reached during the maximum plasma compression. The plasma electron density depends on the initial conditions of the experiments. It was thus important to determine first the plasma flow characteristics before attempting any target irradiation. These data were needed for comparison with plasma characteristics after an irradiation of the investigated target. In fact, spectroscopic measurements performed during interactions of plasma streams with the investigated W samples showed many WI and WII spectral lines. The surface erosion was determined from mass losses of the irradiated samples. Changes on the surfaces of the irradiated samples were also investigated with an optical microscope and some sputtering and melting zones were observed.

4

Recent ion measurements within the modified DPF-1000U facility

Kwiatkowski R., Czaus K., Skladnik-Sadowska E., Sadowski M. J., Zaloga D. R., Paduch M., Zielinska E.

Nukleonika

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2015

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Vol. 60, No. 2

297--302

EN

In this note we describe measurements of ion beams emitted along the z-axis of the DPF-1000U facility operated at 23 kV, 334 kJ, and with the initial deuterium pressure of 1.6–2 hPa. The DPF-1000U device was recently renewed and equipped with a dynamic gas-puff valve placed inside the inner electrode. The investigated ions were recorded by means of ion pinhole cameras equipped with solid state nuclear track detectors of the PM-355® (PADC) type. The energy spectra of ions were determined using a Thomson spectrometer placed on the symmetry axis at a distance of 160 cm from the electrodes outlets. The ion images recorded during discharges performed under different experimental conditions show that the ion beams have a complex structure, usually in the form of a central bunch and an annular stream composed of many micro-beams. Energies of the registered deuterons have been in the range of 30–700 keV, while the fast protons (which originated from the hydrogen remnants) had energies in the range of 300–850 keV.

5

Comparison of optical spectra recorded during DPF-1000U plasma experiments with gas-puffing

Zaloga D. R., Skladnik-Sadowska E., Kubkowska M., Ladygina M. S., Malinowski K., Kwiatkowski R., Sadowski M. J., Paduch M., Zielinska E., Makhlaj V. A.

Nukleonika

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2015

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Vol. 60, No. 2

309--314

EN

The results are presented of the optical spectra measurements for free plasma streams generated with the use of the modifi ed DPF-1000U machine. This facility was recently equipped with a gas injection system (the so-called gas-puff) placed on the symmetry axis behind the central opening in the inner electrode. The DPF-1000U experimental chamber was fi lled up with pure deuterium at the initial pressure of 1.6 or 2.4 mbar. Additionally, when the use was made of the gas-puff system about 1 cm3 of pure deuterium was injected at the pressure of 2 bars. The gas injection was initiated 1.5 or 2 ms before the triggering of the main discharge. The investigated plasma discharges were powered from a condenser bank charged initially to 23 kV (corresponding to the energy of 352 kJ), and the maximum discharge current amounted to about 1.8 MA. In order to investigate properties of a dense plasma column formed during DPF-1000U discharges the use was made of the optical emission spectroscopy. The optical spectra were recorded along the line of sight perpendicular to the vacuum chamber, using a Mechelle®900 spectrometer. The recent analysis of all the recorded spectra made it possible to compare the temporal changes in the electron density of a freely propagating plasma stream for discharges without and with the gas-puffing. Using this data an appropriate mode of operation of the DPF-1000U facility could be determined.

6

Transient plasma loads to the ITER divertor surfaces : simulation experiments with QSPA Kh - 50

Garkusha I. E., Aksenov N. N., Chuvilo A. A., Landman I. S., Makhlaj V. A., Malykhin S. V., Pugachev A. T., Sadowski M. J., Skladnik-Sadowska E.

Nukleonika

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2012

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Vol. 57, No. 2

167-170

EN

Experimental simulations of International Thermonuclear Experimental Reactor (ITER) transient events with relevant heat load and particle load parameters have been performed with a quasi-stationary plasma accelerator QSPA Kh-50. Pulsed plasma guns PPA and IBIS were also used for comparative studies of surface damages appearing under varying plasma parameters and sorts of plasma ions. Particular attention is paid to the material erosion due to particles ejection from the tungsten surfaces both in the form of droplets and solid dust. Generation mechanisms of the dust in the course of ELM-like plasma impacts to the tungsten surfaces are discussed

7

Time - and space - resolved measurements of high - energy ion beams emitted from PF - type discharges

Kwiatkowski R., Sadowski M. J., Skladnik-Sadowska E., Zebrowski J., Malinowski K., Czaus K., Garkusha I. E.

Nukleonika

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2012

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Vol. 57, No. 2

211-214

EN

The paper presents experimental studies of the spatial-microstructure and temporal-characteristics of fast ion beams, which are emitted from high-current plasma-focus (PF) discharges performed within the PF-360 facility at National Centre for Nuclear Research (NCBJ) at Otwock/Świerk, Poland. The spatial structure of the ion beams was investigated by means of pinhole cameras equipped with solid-state nuclear track detectors shielded by absorption filters made of Al-foils of different thickness. In order to perform time-resolved measurements there were applied miniature scintillation detectors placed at different points of the ion-image plane.

8

Research on spatial and energetic characteristics of the ion beams emitted in the PF - 360 discharges

Kwiatkowski R., Skladnik-Sadowska E., Malinowski K., Sadowski M. J., Czaus K., Zebrowski J., Garkusha I. E.

Nukleonika

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2012

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Vol. 57, No. 1

67-74

EN

Experimental results are presented on the spatial structure and energetic characteristics of the fast ion beams produced by high-current discharges in a PF-360 device operated at the National Centre for Nuclear Research (NCBJ, Otwock/Świerk, Poland). The 105 kJ discharges were initiated at the initial deuterium pressure around p0 = 6 hPa and were powered from a 234 miF capacitor bank charged up to 30 kV. The spatial structure of the ion beams was recorded using pinhole cameras equipped with the solid-state nuclear track detectors of the PM-355 type, placed at two different angles (0 centigrade, 45 centigrade) relative to the discharge axis. The detectors were shielded by thin absorption filters made of pure Al foils of various thickness, which made it possible to record only ions with energies exceeding a chosen threshold value. Similarly as in other plasma focus (PF) experiments, energies of the emitted ions ranged from about 30 keV to about 3 MeV, i.e. they were much higher than the voltage applied to the electrodes. The recorded ion images showed a complex spatial structure of the fast ion beams, which consisted of many micro-beams of different energies. It is possible that these beams were emitted by various local micro-sources (e.g. plasma micro-diodes) the were formed inside the PF pinch column.

9

Optical emission spectroscopy of plasma produced from tungsten target irradiated within RPI - IBIS facility

Skladnik-Sadowska E., Malinowski K., Sadowski M. J., Nowakowska-Langier K., Ladygina M. S., Garkusha I. E.

Nukleonika

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2012

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Vol. 57, No. 2

193-196

EN

The paper presents recent research on characteristics of deuterium plasma streams generated within an RPI-IBIS (multi-rod plasma injector) facility, and optical spectra of plasma produced during the interaction of these streams with a tungsten target placed at a distance of 20 cm from the electrode outlets. Distinct WI- and WII-lines were recorded and the noticeable erosion of the W-target was observed for shots delivering more than 4 J/cm2 on the target surface.

10

Optical emission spectroscopy of plasma streams in PF-1000 experiments

Jakubowska K., Kubkowska M., Skladnik-Sadowska E., Malinowski K., Marchenko A. K., Paduch M., Sadowski M. J., Scholz M.

Nukleonika

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2011

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Vol. 56, No. 2

125-129

EN

The optical spectroscopy in the visible range was used to determine properties of the dense magnetized plasma generated in the PF-1000, a 1 MJ plasma focus device operating in the Institute of Plasma Physics and Laser Microfusion (IPPLM) in Warsaw, Poland. The experiments were performed in a vacuum chamber pumped out to the basic pressure of 2 x 10.5 hPa. The initial pressure of the pure deuterium filling was 2.9 hPa, while that of the deuterium--argon mixture was 1.07 hPa of D2 and 0.13 hPa of Ar. The deuterium-plasma emission contained the Balmer series (Dalfa, Dbeta and Dgamma) and a few distinct copper (Cu I) lines originating from the inner electrode material. The emission of the deuterium-argon plasma was rich in Ar II lines. The electron density (ne), averaged over line of sight, of order of 1016 cm.3 was calculated on the basis of the Dalfa and Dbeta emission only, because the D�ż line was strongly self-absorbed. A group of the Ar II spectral lines was used to estimate the excitation temperature (Texc = 3 eV) by means of a Boltzmann plot. Additionally, the temporal evolution of the electron density was determined on basis of the Stark broadening of the Dalfa and Dgamma lines.

11

Measurements of electron and ion beams emitted from the PF-1000 device in the upstream and downstream direction

Kwiatkowski R., Skladnik-Sadowska E., Malinowski K., Sadowski M. J., Czaus K., Zebrowski J., Karpinski L., Paduch M., Scholz M., Garkusha I. E., Kubeš P.

Nukleonika

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2011

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Vol. 56, No. 2

119-123

EN

In this paper we report on measurements of the energy spectra and other properties of the electron and fast ion beams emitted in the upstream and downstream direction along the z-axis of a large plasma focus device PF-1000, that was operated at 21-27 kV, delivering 290–480 kJ pulse. Measurements of the electron beam (EB) properties were performed using a magnetic analyzer. Properties of the ion beams were measured by means of pinhole cameras equipped with PM-355 nuclear track detectors and placed at various angles (0, 60 and 180 centigrade) to the discharge axis. Measurements revealed a complex spatial structure of the fast ion beams. The ion measurements behind the PF-1000 collector proved that some fast deuterons are emitted also in the upstream direction. Measurements of the EBs emitted in the upstream and downstream direction revealed electron energies in the range from approximately 40 keV to approximately 800 keV. These spectra confirm that in localized regions within the PF-1000 plasma column there appear strong fields accelerating charged particles in different directions along the discharge axis.

12

On the nature of changes in the optical characterization produced in sapphire on its irradiation with a pulsed powerful stream of hydrogen ions

Gribkov V., Ivanov L., Maslyaev S., Pimenov V., Sadowski M., Skladnik-Sadowska E., Banaszak A., Kopeć G., Cheblukov Y., Kozodaev M. A., Suvorov A. L., Smirnov I. S.

Nukleonika

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2004

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Vol. 49, nr 2

43-49

EN

Changes in the optical characteristics in synthetic sapphire specimens produced by microsecond pulse irradiation with a stream of hydrogen ions of energies ranging up to tens keV have been observed. Data on decrease in the optical reflection, measured within the wavelength range of 200 900 nm, are presented. This characterization is compared with the data received by optical and atomic force microscopy as well as by lattice structure analysis performed with X-rays. The measurements indicate that the changes of optical parameters are not a consequence of absorption increase and/or sapphire decomposition. They result from modifications of the morphology and structure of surface layer of the sapphire samples, induced by irradiation.

13

Investigation of corpuscular emission from the Prague Capillary Pinch

Skladnik-Sadowska E., Baranowski J., Sadowski M., Koláček K., Řipa M., Ctibor P., Kishinets A., Rupasov A.

Nukleonika

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2002

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Vol. 47, nr 1

31-37

EN

The paper presents results of preliminary measurements of the corpuscular radiation from fast z-pinch discharges, which were performed at the Prague Capillary Pinch facility within a frame of the Czech-Polish scientific collaboration programme. Time-integrated measurements were performed by means of a pinhole camera, equipped with nuclear track detectors of the CR-39 type. In order to perform time-resolved measurements the use was made of a single Faraday-type collector and a double-cup system. It was demonstrated that the fast capillary discharges can emit not only pulses of intense visible radiation and soft X-rays, but also pulses of the corpuscular radiation. An optical analysis of the particle tracks was performed. The particle flux at a distance of 20 cm from the collimator outlet was estimated to be 3.5×107 particles/cm2.

14

Influence of diaphragms on measurements of ions emitted from dense magnetized plasmas

Skladnik-Sadowska E., Sadowski M.

Nukleonika

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2001

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Vol. 46, suppl. 1

57--60

EN

The paper concerns the diagnostics of ions escaping from dense magnetized plasma (DMP) discharges. Particular attention is paid to the basic problem of the separation of such ions from the investigated plasma, under the condition that this process should not disturb the velocity (and energy) distribution functions of the measured ions.

15

Anisotropy of the neutron emission from PF-360 facility operated without and with solid-state targets

Czaus K., Baranowski J., Sadowski M., Skladnik-Sadowska E., Zebrowski J.

Nukleonika

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2001

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Vol. 46, suppl. 1

77--80

EN

The paper reports on detailed studies of an anisotropy of the fusion-produced neutrons emitted from the modernized PF-360 facility [10], which has been operated with a pure deuterium-gas filling, without and with some additional solidstate targets containing deuterium atoms. Under standard operational conditions, anisotropy of the neutron yield from the PF-360 facility is similar to that observed in other PF devices. For the first time the neutron emission anisotropy has been measured in the PF experiments performed with a planar cryogenic target covered with a heavy-ice (D2O) layer. Changes in the Yn(Φ)/Yn(90°) ratio, particularly for angles Φ = 0–60°, have been explained by the known features of the angular distribution of fast deuterons.

16

Comparison of characteristics of pulsed ion beams emitted from different small PF devices

Sadowski M., Skladnik-Sadowska E., Baranowski J., Zebrowski J., Kelly H., Lepone A., Marquez A., Milanese M., Moroso R., Pouzo J.

Nukleonika

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2000

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Vol. 45, nr 3

179-184

EN

The paper concerns studies of pulsed ion beams emitted from different small-energy (5–50 kJ) devices of the plasma focus (PF) type. Emission characteristics of the ion beams as measured with nuclear track detectors (NTDs), Faraday-type collectors (FC), and Thomson-type analyzers, are summarized. Common features of the ion emission are considered and some differences are discussed.