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1

Calorimetric studies of the energy deposition on a material surface by plasma jets generated with QSPA and MPC devices

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Chuvilo A. A. , Garkusha I. E. , Makhlaj V. A. , Petrov Y. V.

Nukleonika

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2012

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tom Vol. 57, No. 1

49-53

EN

Studies of the energy deposition by plasma jets incident on a material surface are of topical interest for both the fusion and plasma technology applications. In this paper the results are reported of a comparative study of plasma energy deposition on different material surfaces exposed to plasma jets of various duration and energy density, generated using the QSPA Kh-50 and the MPC devices. The spatial distribution of plasma energy density and the heat load on the surface were measured with a movable calorimeter. The measurements demonstrate that in the case of an exposure to QSPA plasma jets the absorbed heat load is approximately equal to 55-60% of the energy in the incident plasma jet. In the case of plasma jets generated using the MPC device the heat load on the target surface and was practically the same as for the QSPA jets, and additional shielding effects were found to be negligible due to the short duration of plasma jets.

2

The experimental and theoretical investigations of damage development and distribution in double-forged tungsten under plasma irradiation-initiated extreme heat loads

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Väli B. , Laas T. , Paju J. , Shirokova V. , Paduch M. , Gribkov V. A. , Demina E. V. , Pimenov V. N. , Makhlaj V. A. , Antonov M.

Nukleonika

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2016

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tom Vol. 61, No. 2

169--177

EN

The influence of extreme heat loads, as produced by a multiple pulses of non-homogeneous flow of slow plasma (0.1–1 keV) and fast ions (100 keV), on double-forged tungsten (DFW) was investigated. For generation of deuterium plasma and fast deuterons, plasma-focus devices PF-12 and PF-1000 are used. Depending on devices and conditions, the power flux density of plasma varied in a range of 107–1010 W/cm2 with pulse duration of 50–100 ns. Power flux density of fast ions was 1010–1012 W/cm2 at the pulse duration of 10–50 ns. To achieve the combined effect of different kind of plasmas, the samples were later irradiated with hydrogen plasma (105 W/cm2, 0.25 ms) by a QSPA Kh-50 plasma generator. Surface modification was analysed by scanning electron microscopy (SEM) and microroughness measurements. For estimation of damages in the bulk of material, an electrical conductivity method was used. Investigations showed that irradiation of DFW with multiple plasma pulses generated a mesh of micro- and macrocracks due to high heat load. A comparison with single forged tungsten (W) and tungsten doped with 1% lanthanum-oxide (WL10) reveals the better crack-resistance of DFW. Also, sizes of cells formed between the cracks on the DFW’s surface were larger than in cases of W or WL10. Measurements of electrical conductivity indicated a layer of decreased conductivity, which reached up to 500 µm. It depended mainly on values of power flux density of fast ions, but not on the number of pulses. Thus, it may be concluded that bulk defects (weakening bonds between grains and crystals, dislocations, point-defects) were generated due to mechanical shock wave, which was generated by the fast ions flux. Damages and erosion of materials under different combined radiation conditions have also been discussed.

3

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

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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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tom 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

4

Characterization of dense plasma streams generated by MPC and their interaction with material surfaces

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Makhlaj V. A. , Chebotarev V. V. , Chuvilo A. A. , Garkusha I. E. , Ladygina M. S. , Marchenko A. K. , Petrov Y. V. , Solyakov D. G.

Nukleonika

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2012

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tom Vol. 57, No. 2

197-200

EN

Comparative studies of the parameters both pure helium and helium-xenon plasma have been fulfilled in a magneto-plasma compressor (MPC). The current-voltage characteristics of MPC accelerating channel and the maximum plasma velocity of (6-8) x 106 cm/s changed negligibly under local xenon injection to compression zone. Nevertheless, the xenon addition causes a growth of maximal plasma pressure up to of 2.3 MPa, an increase of plasma radiation from the compression zone. The plasma density achieved 1018 cm.

5

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

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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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tom 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.