Measurements of pulsed electron beams emitted from plasma-focus devices
A dense plasma column, which is formed by a pulsed discharge within facilities of the Plasma-Focus (PF) type, is a source of the intense X-ray emission, pulsed electron beams and ion streams. Investigation of the electron beams can deliver information about development of plasma instabilities, which...
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irk-123456789-789002015-03-23T03:01:59Z Measurements of pulsed electron beams emitted from plasma-focus devices Jakubowski, L. Sadowski, M.J. Plasma dynamics and plasma wall interaction A dense plasma column, which is formed by a pulsed discharge within facilities of the Plasma-Focus (PF) type, is a source of the intense X-ray emission, pulsed electron beams and ion streams. Investigation of the electron beams can deliver information about development of plasma instabilities, which induce the formation of high-temperature plasma micro-regions in the form of hot-spots and/or filaments. The paper reports on recent studies of the pulsed electron beams within PF-type facilities. Шнур щільної плазми, формований імпульсним розрядом на установках типу плазмовий фокус (ПФ), є джерелом інтенсивного рентгенівського випромінювання, імпульсних електронних пучків і потоків іонів. Дослідження електронних пучків може дати інформацію про розвиток плазмових нестійкостей, що викликають формування високотемпературних плазмових мікрообластей у виді «гарячих плям» і/або волокон. Робота присвячена останнім результатам вивчення імпульсних електронних пучків, генерируємих в установках типу ПФ. Шнур плотной плазмы, формируемый импульсным разрядом на установках типа плазменный фокус (ПФ), является источником интенсивного рентгеновского излучения, импульсных электронных пучков и потоков ионов. Исследование электронных пучков может дать информацию о развитии плазменных неустойчивостей, которые вызывают формирование высокотемпературных плазменных микрообластей в виде «горячих пятен» и/или волокон. Работа посвящена последним результатам изучения импульсных электронных пучков, генерируемых в установках типа ПФ. 2005 Article Measurements of pulsed electron beams emitted from plasma-focus devices / L. Jakubowski, M.J. Sadowski // Вопросы атомной науки и техники. — 2005. — № 1. — С. 89-91. — Бібліогр.: 5 назв. — англ. 1562-6016 PACS: 52.59 Hq; 52.70 La. http://dspace.nbuv.gov.ua/handle/123456789/78900 en Вопросы атомной науки и техники Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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Plasma dynamics and plasma wall interaction Plasma dynamics and plasma wall interaction |
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Plasma dynamics and plasma wall interaction Plasma dynamics and plasma wall interaction Jakubowski, L. Sadowski, M.J. Measurements of pulsed electron beams emitted from plasma-focus devices Вопросы атомной науки и техники |
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A dense plasma column, which is formed by a pulsed discharge within facilities of the Plasma-Focus (PF) type, is a source of the intense X-ray emission, pulsed electron beams and ion streams. Investigation of the electron beams can deliver information about development of plasma instabilities, which induce the formation of high-temperature plasma micro-regions in the form of hot-spots and/or filaments. The paper reports on recent studies of the pulsed electron beams within PF-type facilities. |
| format |
Article |
| author |
Jakubowski, L. Sadowski, M.J. |
| author_facet |
Jakubowski, L. Sadowski, M.J. |
| author_sort |
Jakubowski, L. |
| title |
Measurements of pulsed electron beams emitted from plasma-focus devices |
| title_short |
Measurements of pulsed electron beams emitted from plasma-focus devices |
| title_full |
Measurements of pulsed electron beams emitted from plasma-focus devices |
| title_fullStr |
Measurements of pulsed electron beams emitted from plasma-focus devices |
| title_full_unstemmed |
Measurements of pulsed electron beams emitted from plasma-focus devices |
| title_sort |
measurements of pulsed electron beams emitted from plasma-focus devices |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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2005 |
| topic_facet |
Plasma dynamics and plasma wall interaction |
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http://dspace.nbuv.gov.ua/handle/123456789/78900 |
| citation_txt |
Measurements of pulsed electron beams emitted from plasma-focus devices / L. Jakubowski, M.J. Sadowski // Вопросы атомной науки и техники. — 2005. — № 1. — С. 89-91. — Бібліогр.: 5 назв. — англ. |
| series |
Вопросы атомной науки и техники |
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2025-07-06T02:59:27Z |
| last_indexed |
2025-07-06T02:59:27Z |
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1836864784356605952 |
| fulltext |
MEASUREMENTS OF PULSED ELECTRON BEAMS EMITTED
FROM PLASMA-FOCUS DEVICES
L. Jakubowski and M.J. Sadowski
The Andrzej Soltan Institute for Nuclear Studies, 05-400 Otwock-Swierk n. Warsaw, Poland,
jakubowski@ipj.gov.pl
A dense plasma column, which is formed by a pulsed discharge within facilities of the Plasma-Focus (PF) type, is a
source of the intense X-ray emission, pulsed electron beams and ion streams. Investigation of the electron beams can
deliver information about development of plasma instabilities, which induce the formation of high-temperature plasma
micro-regions in the form of hot-spots and/or filaments. The paper reports on recent studies of the pulsed electron
beams within PF-type facilities.
PACS: 52.59 Hq; 52.70 La.
1. INTRODUCTION
The radial compression of a current sheath forms a
dense magnetized plasma pinch column (plasma-focus).
Numerous observations showed that inside the plasma
region there are formed micro-regions (hot-spots) of a
relatively dense (>1020 cm-3) plasma which achieves
considerably high electron temperatures (> 1 keV). The
whole PF pinch column, and particularly hot-spots are
sources of intense X-ray emission as well as pulsed
electron- and ion-beams [1, 2]. Measurements of the
pulsed electron beams can in particular deliver
information about the appearance of high-temperature
dense plasma micro-regions as well as about instabilities
of current filaments and local electromagnetic fields. The
emission of directed electron beams is a reason of
differences in the polarization of some X-ray spectral
lines emitted from the investigated plasma. Therefore,
simultaneously with the registration of the selected X-ray
spectrum lines, we studied their correlation with pulsed
electron beams emitted perpendicularly to the discharge
axis as well as in the upstream direction.
2. TIME-RESOLVED MEASUREMENTS
OF PULSED ELECTRON BEAMS
WITH ČERENKOV DETECTORS
In order to determine emission dynamics of the
pulsed electron beams one can apply detectors based on
the Čerenkov radiation, because the emission of that is
almost instantaneous (with a delay below 0.1 ns).
Intensity of the Čerenkov radiation is very high and such
detectors have very high temporal and spatial resolution.
The Čerenkov radiation appears if a charged particle
penetrates a transparent medium with a velocity v higher
than the phase velocity of light u in this medium which is
equal to c/n, where n is the refraction coefficient of the
material in question. The condition can be written as:
v > u or β n > 1 where β = v/c
From this equation it can be seen that the emission of
the Čerenkov radiation has an energy threshold. A
comparison of refraction index values and corresponding
minimal energy values for different materials show that to
record electron beams of lower energy it is necessary to
use radiators made of diamond or rutil.
In order to determine the spatial and temporal
localization of hot-spots, the X-rays were measured from
two chosen micro-regions: the first one placed in a close
proximity of the electrode outlet (XNS), and the second
one (XSF) placed at the distance of 20 mm along the z-
axis. An example of time-resolved electrons signals and
X-rays is presented in the oscillogram shown Fig 1.
In that case the recorded X-ray pulses were evidently
emitted from hot-spots formed in the selected micro-
regions. Detailed studies of the correlation of the electron-
induced signals and X-ray pulses confirmed the
hypothesis that the observed emissions originate from the
hot-spots simultaneously [3]. It should be noted that the
life-time of observed hot-spots is about 7-10 ns. These
hot-spots are formed successively along the z-axis (or
near by) and they are responsible for the successive X-ray
and electron pulses. The hot-spots are usually separated in
space and time. It should also be noted that the Čerenkov
detectors, which were placed at angles of 45o and 90o to
the z-axis, have also revealed electron streams emitted in
these directions.
The electron measurements, as performed in the
direction perpendicular to the discharge axis, have shown
that the pulsed electron beams appear about 100 ns before
Problems of Atomic Science and Technology. 2005. № 1. Series: Plasma Physics (10). P.89-91 89
Fig. 1. Correlation of the soft X-ray pulses emitted
from different hot-spots (near - X
NS
and far - X
SF
)
with fast e-beams (e-) and soft X-rays (X
S
) registered
from the whole pinch column
mailto:jakubowski@ipj.gov.pl
the voltage spike, as shown in Fig.2. This time
corresponds to an instant when the current sheath appears
in front of the electrode outlet. The emission of an intense
electron pulse of energy > 80 keV, as observed in the
radial direction, could be caused by some instabilities
which develop in the current sheath.
The emission of directed electron beams is a reason
of differences in the polarization of some X-ray spectral
lines emitted from the investigated plasma. In order to
study temporal changes in the selected X-ray lines the
detection systems of the spectrometers were modified, so
that the X-ray films were replaced by sets of miniature
scintillators of the NE102A type. Those scintillation
detectors could record the chosen spectral lines
separately. Therefore, simultaneously with the registration
of the selected X-ray spectrum lines, we studied their
correlation with pulsed electron beams emitted
perpendicularly (at 900) to the discharge axis [4] as well
as in the upstream direction (at 1800), towards the anode
opening (see Fig.2). One can easily see that the maximum
emission of the considered spectral lines, i.e. the
resonance line ArXVII-1P1, the inter-combination line
ArXVII-3P1, and the averaged satellite line ArXVI,
appears during the over-voltage peak (U). This effect is
accompanied by a dip (peculiarity) in the discharge
current and the emission of the “soft” X-rays (X-soft) as
well as fast electrons directed towards the anode – E1
(180o). It should be noted that the beginning of the
emission of the investigated X-ray lines correlates well
with the appearance of pulsed electron beams emitted
perpendicularly to the discharge axis. The considered
spectral lines and the radial-oriented electron beams
appear about 100 ns before the main current dip. In this
instant the current sheath is pushed from the inter-
electrode gap into the region in front of the electrode
ends. The emission of the X-ray lines as well as fast
electrons in this moment is probably induced by
Rayleigh-Taylor instabilities developing inside the
moving current sheath. It has been found that the emission
of highly ionized argon lines is well correlated with the
appearance of successive hot-spots and the emission of
electron beams from them.
During simultaneous measurements of fast ions, as
performed by means of a time-of-flight method, an
analysis of their correlation with pulsed e-beams made
possible to determine an energy distribution of deuterons,
as shown in Fig.3.
3. TIME-INTEGRATED MEASUREMENTS
OF ELECTRON BEAMS WITH MAGNETIC
SPECTROMETERS
In order to investigate electron beams of energy
below the Čerenkov threshold, and to determine the
whole energy spectrum of electrons emitted from plasma,
one can also apply magnetic spectrometers. If a
collimated electron beam penetrates through a constant
and uniform magnetic field, it may be deflected by a
given angle (e.g. 180o). Since a radius of the deflection is
proportional to the electron velocity (energy) values,
using an appropriate magnetic field it is possible to record
electrons within a chosen energy range (e.g. 5-700 keV).
The deflected electron beams can be recorded, e.g. upon
an X-ray film, which makes possible to determine the
90
Fig.3. A - Three electron induced signals, in the
comparison with three successive (superimposed) ion
signals, B - Energy distribution of deuterons, as
computed from ion signals registered from different
hot-spots.
A
B
Fig.2. Correlation of time-resolved signals
corresponding to the highly ionized argon lines
with electrons pulses emitted at the angle of 90o
to the z-axis (A), as well as with other
characteristics of the investigated discharge (B).
time-integrated energy spectrum of electrons even from a
single discharge, as shown in Fig.4.
The analysis of many experimental measurements has
shown that the investigated electron beams had energies
ranging from several keV to about 600 keV. The recorded
images and corresponding energy spectra have appeared to be
not very smooth and they have suggested that individual
micro-sources emit electrons within relatively narrow energy
bands. Such electron pulses could evidently be emitted by
individual hot-spots.
4. TIME-RESOLVED MEASUREMENTS
OF ELECTRON BEAMS WITH MAGNETIC
SPECTROMETERS
In order to study temporal changes in the emission of
electron beams within selected bands of the energy spectrum,
the use was made of miniature scintillation detectors, which
were installed in chosen points of the image plane of the
magnetic spectrometer. Those detectors produced light pulses
corresponding to electrons of the energy values with accuracy
of ±10%. In our experiments the chosen values were: 20, 50,
200 and 500 keV, respectively. An example of the
corresponding signals is presented in Fig.5.
The obtained results have confirmed that in the observed
energy bands the electron spectrum has a multi-spike
structure. Taking into consideration the shape, width and time
instants, when the electron-induced X-ray pulses appear, a
comparison with the images recorded with X-ray pinhole
camera can be performed. Such a comparison confirms that
individual electron peaks really correspond to different hot-
spots. It can also be stated that these hot-spots emit electron
beams within defined energy bands, what has been suggested
by the measurements of the integrated electron-energy spectra.
REFERENCES
[1] P. Choi, C. Deeney, C.S. Wong, et al. Investigation of
hotspot and electron beam formation in the DPF-78 Plasma
Focus // Proc. Intern. Workshop on PF and Z-pinch, Toledo,
1987, р.76-84.
[2] M. Sadowski, L. Jakubowski, J. Żebrowski. Studies of high
energy electron beams emitted from pf-type discharge //
Proc. 18th European Conference on Controlled Fusion and
Plasma Physics, Berlin, 1991. Part II, pp. 233-236.
[3] L. Jakubowski, M. Sadowski, E.O. Baronova. Eksperimental
studies of hot-spots inside pf discharges with argon admixtures //
Proc. Int. Conf. on Plasma Physics, Nagoya, 1996, Vol.2,
р.1326-1329.
[4] L. Jakubowski, M.J. Sadowski, E.O. Baronova. Temporal
characteristics of electron beams from Plasma-Focus and their
correlation with highly-ionized Ar-lines // Czech. J. Phys.
(54). 2004, Suppl. C, р.291-297.
[5] L. Jakubowski, M. Sadowski and J. Żebrowski.
Measurements of charged particle-beams from plasma-focus
discharges // Nuclear Fusion (41). 2001, N6, р.755-759.
91
Fig.4. On the top – a scheme of the magnetic spectrometer.
On the bottom – the electron energy spectrum recorded on
X-ray film for a single PF shot: (a) as registered on the first
emulsion layer, (b) as registered behind a filter, (c) the
corresponding electron spectrum
Fig.5. Time-resolved electron signals within different energy
bands. The pulses seem to correspond to different hot-spots
with various emission characteristics
ИЗМЕРЕНИЯ ИМПУЛЬСНЫХ ЭЛЕКТРОННЫХ ПОТОКОВ,
ЭМИТИРОВАННЫХ ИЗ УСТАНОВОК ТИПА ПЛАЗМЕННЫЙ ФОКУС
Л. Якубовский и М. Садовский
Шнур плотной плазмы, формируемый импульсным разрядом на установках типа плазменный фокус (ПФ), является
источником интенсивного рентгеновского излучения, импульсных электронных пучков и потоков ионов. Исследование
электронных пучков может дать информацию о развитии плазменных неустойчивостей, которые вызывают
формирование высокотемпературных плазменных микрообластей в виде «горячих пятен» и/или волокон. Работа
посвящена последним результатам изучения импульсных электронных пучков, генерируемых в установках типа ПФ.
ВИМІРИ ІМПУЛЬСНИХ ЕЛЕКТРОННИХ ПОТОКІВ,
ЕМІТОВАНИХ ІЗ УСТАНОВОК ТИПУ ПЛАЗМОВИЙ ФОКУС
Л. Якубовский и М. Садовский
Шнур щільної плазми, формований імпульсним розрядом на установках типу плазмовий фокус (ПФ), є джерелом
інтенсивного рентгенівського випромінювання, імпульсних електронних пучків і потоків іонів. Дослідження
електронних пучків може дати інформацію про розвиток плазмових нестійкостей, що викликають формування
високотемпературних плазмових мікрообластей у виді «гарячих плям» і/або волокон. Робота присвячена останнім
результатам вивчення імпульсних електронних пучків, генерируємих в установках типу ПФ.
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