Study of fusion neutron yield from PF-360 facility equipped with solid-state or gas-puffed targets
The paper reports on results of Plasma-Focus (PF) investigation carried out within the PF-360 device, which was equipped with exchangeable targets made of heavy-ice (D2O) layers or D2-gas puffs. The main aim of these studies was to increase a neutron yield from PF discharges by using fast deuteron b...
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| Zitieren: | Study of fusion neutron yield from PF-360 facility equipped with solid-state or gas-puffed targets / J. Zebrowski, J. Baranowski, L. Jakubowski, M.J. Sadowski, J. Stanislawski // Вопросы атомной науки и техники. — 2000. — № 6. — С. 91-93. — Бібліогр.: 10 назв. — англ. |
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Zebrowski, J. Baranowski, J. Jakubowski, L. Sadowski, M.J. Stanislawski, J. 2015-03-18T19:09:51Z 2015-03-18T19:09:51Z 2000 Study of fusion neutron yield from PF-360 facility equipped with solid-state or gas-puffed targets / J. Zebrowski, J. Baranowski, L. Jakubowski, M.J. Sadowski, J. Stanislawski // Вопросы атомной науки и техники. — 2000. — № 6. — С. 91-93. — Бібліогр.: 10 назв. — англ. 1562-6016 https://nasplib.isofts.kiev.ua/handle/123456789/78553 533.9 The paper reports on results of Plasma-Focus (PF) investigation carried out within the PF-360 device, which was equipped with exchangeable targets made of heavy-ice (D2O) layers or D2-gas puffs. The main aim of these studies was to increase a neutron yield from PF discharges by using fast deuteron beams, which are usually emitted from a pinch column and which can interact with additional targets. This work was partially supported by the US-AF EOARD contract no. F61775-99-WE088 (SPC99-4088) en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Plasma dynamics and plasma-wall interaction Study of fusion neutron yield from PF-360 facility equipped with solid-state or gas-puffed targets Article published earlier |
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Study of fusion neutron yield from PF-360 facility equipped with solid-state or gas-puffed targets |
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Study of fusion neutron yield from PF-360 facility equipped with solid-state or gas-puffed targets Zebrowski, J. Baranowski, J. Jakubowski, L. Sadowski, M.J. Stanislawski, J. Plasma dynamics and plasma-wall interaction |
| title_short |
Study of fusion neutron yield from PF-360 facility equipped with solid-state or gas-puffed targets |
| title_full |
Study of fusion neutron yield from PF-360 facility equipped with solid-state or gas-puffed targets |
| title_fullStr |
Study of fusion neutron yield from PF-360 facility equipped with solid-state or gas-puffed targets |
| title_full_unstemmed |
Study of fusion neutron yield from PF-360 facility equipped with solid-state or gas-puffed targets |
| title_sort |
study of fusion neutron yield from pf-360 facility equipped with solid-state or gas-puffed targets |
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Zebrowski, J. Baranowski, J. Jakubowski, L. Sadowski, M.J. Stanislawski, J. |
| author_facet |
Zebrowski, J. Baranowski, J. Jakubowski, L. Sadowski, M.J. Stanislawski, J. |
| topic |
Plasma dynamics and plasma-wall interaction |
| topic_facet |
Plasma dynamics and plasma-wall interaction |
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2000 |
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English |
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Вопросы атомной науки и техники |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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Article |
| description |
The paper reports on results of Plasma-Focus (PF) investigation carried out within the PF-360 device, which was equipped with exchangeable targets made of heavy-ice (D2O) layers or D2-gas puffs. The main aim of these studies was to increase a neutron yield from PF discharges by using fast deuteron beams, which are usually emitted from a pinch column and which can interact with additional targets.
|
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1562-6016 |
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https://nasplib.isofts.kiev.ua/handle/123456789/78553 |
| citation_txt |
Study of fusion neutron yield from PF-360 facility equipped with solid-state or gas-puffed targets / J. Zebrowski, J. Baranowski, L. Jakubowski, M.J. Sadowski, J. Stanislawski // Вопросы атомной науки и техники. — 2000. — № 6. — С. 91-93. — Бібліогр.: 10 назв. — англ. |
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2025-11-26T12:47:18Z |
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UDC 533.9
Problems of Atomic Science and Technology. 2000. № 6. Series: Plasma Physics (6). p. 91-93 91
STUDY OF FUSION NEUTRON YIELD FROM PF-360 FACILITY
EQUIPPED WITH SOLID-STATE OR GAS-PUFFED TARGETS
J.Zebrowski, J.Baranowski, L.Jakubowski, M.J.Sadowski and J.Stanislawski
Department of Plasma Physics and Technology (P-V)
The Andrzej Soltan Institute for Nuclear Studies (IPJ)
05-400 Otwock-Swierk by Warsaw, Poland; e-mail: msadowski@ipj.gov.pl
The paper reports on results of Plasma-Focus (PF) investigation carried out within the PF-360 device, which was
equipped with exchangeable targets made of heavy-ice (D2O) layers or D2-gas puffs. The main aim of these studies
was to increase a neutron yield from PF discharges by using fast deuteron beams, which are usually emitted from a
pinch column and which can interact with additional targets.
1. Introduction
Studies of neutrons and other products of fusion
reactions, as well as studies of high-energy ions, fast
electrons, and X-rays, have been carried out in plasma
laboratories all over world. Numerous Plasma-Focus
experiments, which were performed at different
laboratories, showed a promising scaling of the neutron
yield (Yn) from D-D fusion reactions. Some
investigation extended this scaling to a multi-MJ and
multi-MA level [1], but this hypothesis has not been so
far verified experimentally. On contrary, it was found
that the neutron emission saturates or even decreases
when the initial energy input and discharge current are
increased above certain threshold values [2-3]. Hence,
the record neutron yields from the largest PF machines
operated at W0 < 800 kJ, reached only about 1012
neutrons/shot.
The first PF-20 device was constructed in Swierk in the
60s, and the PF-360 machine was built during the turn
of the 70s and 80s [4]. Measurements of charged
particles emitted from the PF-360 device were carried
out in the 90s [5-8]. For that purpose various time-
integrated and time-resolved diagnostic techniques were
applied.
2. Experimental set-up
The PF-360 facility was equipped with Mather-type,
coaxial electrodes made of pure copper. The inner
electrode was 120 mm in diameter, and the outer one
was 170 mm in diameter. Both electrodes were about
300 mm in length, and the basis of the inner electrode
(anode) was embraced with a ceramic insulator tube of
80 mm in length.
The main experimental chamber of the PF-360 machine
was filled up with pure deuterium under the initial
pressure varied from 5.15 mbar to 12.0 mbar. The PF-
discharges were powered from a capacitor bank of 288
μF (or sometimes 252 μF). The initial charging voltage
was limited to 30 kV for safety reasons, and the most
PF-360 experiments were performed within the energy
range from 122 kJ to 130 kJ. The general view of the
modernized PF-360 facility has been shown in Fig. 1.
In order to increase the neutron yield it was proposed to
make use of fast deuterons, which escape from the PF-
region. In the first case a planar target, which was
equipped with a thick metal plate connected with a
Dewar type tube for a cooling liquid-nitrogen flow, was
design. The construction enabled the target plate to be
positioned on the z-axis, at a variable distance from the
PF electrode outlet. In order to make possible the
formation of a heavy-ice (D2O) layer upon the target
plate there was installed an additional vacuum valve,
which supplied a small amount of heavy water. The
thickness of the D2O-ice layer was varied by a change in
amount of the injected heavy water and cooling medium
flow.
In order to make use of accelerated deuterons moving in
the radial direction (mainly during the current-sheath
callapse and the PF-pinch phase), there was proposed
another version of the cryogenic target. It was designed
as a thin-wall copper tube of about 5 mm in diameter,
and 150 mm in length. That needle-like cryogenic target
was cooled down by an inside flow of a liquid nitrogen
stream, and it was also covered with a thin heavy-ice
layer.
Another experimental method, as proposed in order to
increase the neutron yield, was based on the application
of an additional deuterium-gas target produced within
the PF region. A special fast-acting gas valve was
installed inside the inner electrode. That valve was
powered before the current-sheath collapse, with the
time shift τ of about 400 – 500 μs.
Several diagnostic techniques in the PF-360 experiment
were applied simultaneously. Neutron yields were
measured with two silver-activation counters placed in
the plane of the electrode ends, but at different radial
and angular positions. Time-resolved neutron signals
and very hard X-ray signals were measured with two
scintillator-photomultiplier probes placed side-on at the
distances: d1 = 266 cm and d2 = 383 cm from the pinch
region. Time-integrated measurements of the X-ray
were carried out with an X-ray pinhole camera and two
VAJ-type radiometers. Time-resolved measurements of
Fig. 1. General view of the PF-360 device
92
X-ray pulses were performed with a scintillation set of
the XET type.
3. Experimental results
3.1. D2O-ice planar target
Several series of PF shots were performed with the
planar target placed on z-axis of device at different
dis
opt
considerable increase in the average neutron yield (from
2.4 x 1010 to 3.8 x 1010) at determined experimental
conditions (p0 = 8.0 mbar D2, Uo = 30 kV, Wo = 130 kJ).
The optimal position of the target was at a distance l0 =
225 mm from the electrodes ends, as shown Fig. 2.
The X-ray pinhole pictures, which were taken side-on
the electrode outlet, showed that the X-ray emission
from the PF pinch column did not change considerably
when the planar cryogenic target was placed in different
axial positions. Some examples of the X-ray pinhole
pictures have been presented in Fig. 3.
A comparison of the voltage and current-waveforms
showed that the position of the planar cryogenic target
did not influence PF discharges considerably, provided
that it was placed not too close to the electrode outlet
(i.e., at a distance lo > 80 mm). Example of time-
resolved neutron signals has been presented in Fig. 4.
3.2. D2O-ice needle type target
It was proved, by the modeling computations of ion
trajectories within the collapsing current-sheath and the
region of the PF pinch column (which were performed
Fig
a p
36
tar
pe
pi
w
t
f
p
ax
p
fo
l
p0
Yn
Fig.2. Average neutron yields versus the initial D2-
illing pressure, as measured for PF-360 discharges
erformed with the D2O-ice planar target at different
ial position. The initial conditions were U0 = 30 kV
and W = 130 kJ
tances from the electrode outlet. Preliminary
imization measurements have demonstrated a
with taking into account the appearance of current
filaments [9]), that a considerable portion of accelerated
deuterons can move in the radial direction. Therefore, it
was reasonable to try to apply a “needle- like”
cryogenic target (described in the previous section).
There were carried out several series of the PF-360
experiments with the needle-like target. The neutron
yield measurements showed that the placement of such
a target near the PF-360 electrode outlet (at lo = 20 mm)
did not influence the average neutron emission very
much. However, it should be mentioned, that in general
a small decrease of Yn was observed (especially for the
target position at lo = 65 mm position). In that case one
could also achieve an increase in the neutron yield,
particularly at higher initial pressures in the
experimental chamber D2-filling, and at lo = 100 mm. It
that experiment the highest neutron yield Yn = 2.3 x 1010
neutrons/shot, as measured for series of several
successive shots, was obtained at the initial deuterium
pressure po = 10 mbar D2. In general the needle-like
target disturbed the pinch column too much (see another
paper in this conference [10]).
The detailed X-ray measurements, which were
performed with the X-ray pinhole camera placed side-
on the main experimental chamber, showed that the
.3. Soft X-ray pinhole pictures, which were taken with
inhole camera, for discharges performed in the PF-
0 facility. It was equipped with the planar cryogenic
get placed in different axial positions. The shots were
rformed at U0 = 30 kV, and W0 = 122 kJ. The upper
cture shows the pinch region, when the planar target
ithout cooling down was applied. The lower one was
aken with the target covered with the D2O-ice layer
0
Fig.4. Time-resolved traces from the scintillator-
hotomultiplier neutron probes, which were obtained
r PF-shots with the D2O-ice planar target, at U0 = 30
kV, and W0=130 kJ. Also shown are the discharge
current (I) and hard X-rays (Xn) signals
Fig.5. Examples of soft X-ray pinhole pictures, as
taken with a pinhole camera, for PF-360 machine
operated at U0 = 30 kV and W0 = 122 kJ, with the
needle-like cryogenic target. That target was placed
along the z-axis, within the PF pinch region
0 = 230 mm
= 10.3 mbar
= 2.7 x 1010
93
application of the needle cryogenic target did not
influence the X-ray emitted region considerably. Such
results were obtained when the top of the needle-like
target was placed not too close to the electrode outlet
(i.e., at l0 > 20 mm). Some examples of the soft X-ray
pinhole pictures, as obtained in condition described
above, have been shown in Fig. 5.
3.3. D2 gas – puffed target
Several series of the PF experiments with deuterium-
gas puffed targets were performed. The fast acting gas
valve, as described in the previous Section 2, was
operated mainly at pv = 21 bar D2, Uv = 3.2 - 3.5 kV.
The gas valve was activated 400 μs or 500 μs before the
triggering of the main PF discharge. Several series of PF
shots were performed at various initial pressures in the
main chamber. With the application of such a gas target
the PF-360 facility was able to operate at slightly lower
initial pressures.
During the experiments described the pressures varied
from about 5.15 mbar D2 to about 8.2 mbar D2. The
neutron measurement from PF-360 shots, which were
performed with described above target, showed that an
average neutron yield depends also strongly on the gas
conditions. The neutron emission dependence as a
function of valve parameters has been shown in Fig. 6.
For the deuterium-puffed PF discharges the highest
Fig.6. Average neutron yields versus the initial deuterium
pressure as measured for PF-360 experiments, performed with
additional gas-puffed target at V0 = 30 kV and W0 = 122 kJ.
The different values of valve time shift (τ) and valve voltage
(Uv ) were applied
Fig.7. Soft X-ray pinhole pictures, which were taken with a
pinhole camera for discharge performed in the PF-360 facility
equipped with the gas-puffing equipment at U0 = 30 kV and
W0= 122 kJ. The different values of valve time shift (τ) were
applied
neutron yield (equal to Yn = 2.3 x 1010 neutrons/shot),
was obtained at the initial pressure po = 5.6 mbar D2,
and at a lower density of the deuterium target. Such
conditions were achieved when the gas-valve was
operated at lower voltage (U v = 3.2 kV), and the main
discharge was triggered later (τ = 400 μs). The X-ray
measurements, which were carried out with the X-ray
pinhole camera, showed noticeable differences in the X-
ray emission. That emission depended on the initial gas
conditions and the gas-puffed target formation. Some
examples of the X-ray pinhole pictures have been
shown in Fig. 7.
It was observed that the gas-puffed target could change
dynamics of the PF-compression phase, but under
appropriate gas conditions an average neutrons yield
could also be increased considerably.
4. Summary and conclusions
The most important results of the neutron yield studies
described above can be summarized as follows:
- Preliminary optimization measurements with planar
cryogenic target have demonstrated a considerable
increase in average neutron yield (from 2.4 x 1010 to 3.8
x 1010) at determined experimental conditions.
- The experiments with the needle-like cryogenic
target have shown insignificant increase in the average
neutron yield (up to 2.3 x 1010) at the investigated
experimental conditions.
- The use of the gas-puffed target showed a change in
dynamics of the PF-compression phase, but the neutron
yield was changed slightly. More detailed neutron
optimization studies are needed.
- The described measurements of neutron yields, with
the use of different additional targets, should be
performed also in other PF facilities in order to
determine the neutron scaling.
Acknowledgements
This work was partially supported by the US-AF EOARD
contract no. F61775-99-WE088 (SPC99-4088)
References
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Current Trends in Intern. Fusion Research – Proc. 2nd
Symp. (Ed. E.Panarella, Publ. Plenum Press, New York,
1997), p. 11.
[2] H.Herold, A.Jerzykiewicz, M.Sadowski, and H.Schmidt:
Nuclear Fusion 29 (1989), p. 1255.
[3] M.Sadowski: J. Moscow Phys. Soc. 8 (1998), p. 197.
[4] A.Jerzykiewicz, M.Bielik, L.Jakubowski, Z.Jankowicz, et al.:
Proc. 10th Conf. on Plasma Phys. and Controlled Nuclear
Fusion Research, London 1984, Nuclear Fusion Supplement
1985, p. 591.
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Mashhadani: Proc. 19th EPS Conf. on Controlled Fusion
and Plasma Physics, Innsbruck, June 1992, Pt.I, p.691.
[6] M.Sadowski, J.Zebrowski, and E.M.Al-Mashhadani: Proc
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April 1993, AIP Conference Proceedings 299 - Dense Z-
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[8] M.Sadowski, and J.Zebrowski: J.Tech. Phys. 39 Spec. Suppl.
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(Alushta, Ukraine, Sept. 11-16, 2000).
J.Zebrowski, J.Baranowski, L.Jakubowski, M.J.Sadowski and J.Stanislawski
Acknowledgements
References
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