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Experimental studies of the properties of a condensate of cesium excited states are analyzed. Theoretical and experimental data of different authors are compared. We discuss the concept of the practical use of the Rydberg matter in the working process of a low-temperature thermionic converter (TIC) of energy at the emitter temperature below 1600 K, the collector temperature below 700 K, and the generalized index of energy loss in a TIC (barrier index) of V b ~ 1.6 eV.
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ISSN 19907931, Russian Journal of Physical Chemistry B, 2015, Vol. 9, No. 4, pp. 546–551. © Pleiades Publishing, Ltd., 2015.
Original Russian Text © V.I. Yarygin, A.S. Mustafaev, 2015, published in Khimicheskaya Fizika, 2015, Vol. 34, No. 8, pp. 42–48.
546
1. INTRODUCTION
The metastable form of existence of matter in the
form of a condensate of excited states of atoms or a
Rydberg matter (RM) has been in the focus of a large
group of researchers of fundamental and applied
aspects of this phenomenon from the end of the 1960s.
The issue firstly appeared in the theoretical works of
L.V. Keldysh and the group of Russian scientists led by
E.A. Manykin. The experimental studies began by the
group of Prof. L. Holmlid at the University of Goth
enburg (Sweden) in the beginning of the 1990s and,
from the end of 1990s, by the group led by V.I. Yarygin
at the Institute of Physics and Power Engineering
(Obninsk, Russia) and other scientists. More than a
hundred of publications are known on the research
findings in the field of the Rydberg matter; among
them, the results of [1–19] are the most interesting,
obtained in the interelectrode space of lowtempera
ture weakly ionized cesium plasma of a thermionic
energy converter.
The main findings of the studies of a condensate of
excited states (CES) of cesium, obtained by electro
physical and optical methods, published in the Pro
ceedings of the Kaluga Regional Scientific Center
[20–25] and other national publications, are discussed
in this paper. The concept of using TICs with the Ryd
berg matter in direct energy conversion units is dis
cussed in [26–29]. The following results can give some
material for theorists, because the main difference
between our experiments and the others is a vast statis
tical material, reproducible results, the possibility to
compare conventional (nonRM) and unconventional
(with RM) modes under the same conditions of TIC
interelectrode space, and the assessment of possible
applications in modern terrestrial energetics.
2. BASIC CONCEPTS OF THE RYDBERG
MATTER
According to modern notions, the Rydberg matter
is a condensate of clusters of a substance (usually,
alkali metal vapor), consisting of a large number of
excited atoms (up to 1000 atoms [10]). At the excita
tion energy close to the ionization energy, alkali metal
atoms increase their sizes to values of the order of
10
–6
to
10
–5
cm and, at a density of
10
17
–10
18
cm
–3
, form a
metastable CES with a free gas of valence electrons.
Cesium (an interelectrode medium of thermionic
converters) in the CES has a density characteristic of
gases (
~10
17
cm
–3
), a low electron work function (0.2–
0.7 eV), and high conductivity (
~10
–3
Ω
m). Under
certain conditions, the CES of cesium can occur in a
gaseous ordered form through the formation of a so
called plasma crystal (Fig. 1). The condensate of
cesium excited states has other attractive properties:
—Melting point of 450–550 K.
—Internal energy of
~4
eV/atom.
—Lifetime of up to 100 h (a huge value, far supe
rior to the lifetime of the isolated excited atoms).
The existence of the Rydberg matter is not only the
result of the fundamental physics of collisional plasma
but also attracts by possible applications of a number
of technical solutions, such as thermionic converters,
infrared lasers, and others. The mentioned basic char
acteristics of the Rydberg matter, certainly, are not
exhaustive of alkali metals. Among the latter, cesium is
Condensate of Cesium Excited States (Rydberg Matter)
in the Plasma of Thermionic Energy Converters
V. I. Yarygin
a
and A. S. Mustafaev
b
a
Leipunskii Institute of Physics and Power Engineering, Obninsk, Kaluga oblast, 249020 Russia
b
National University of Mineral Resources (Mining University), St. Petersburg, 199106 Russia
email: alexmustafaev@yandex.ru
Received November 9, 2014
Abstract
—Experimental studies of the properties of a condensate of cesium excited states are analyzed. The
oretical and experimental data of different authors are compared. We discuss the concept of the practical use
of the Rydberg matter in the working process of a lowtemperature thermionic converter (TIC) of energy at
the emitter temperature below 1600 K, the collector temperature below 700 K, and the generalized index of
energy loss in a TIC (barrier index) of
V
b
~ 1.6 eV.
Keywords
: condensate of cesium excited states, Rydberg matter, lowtemperature cesium plasma, clusters,
thermal energy thermionic converter, arc discharge
DOI:
10.1134/S199079311504034X
ELEMENTARY PHYSICOCHEMICAL PROCESSES
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY B Vol. 9 No. 4 2015
CONDENSATE OF CESIUM EXCITED STATES (RYDBERG MATTER) 547
particularly interesting as a low work function and
high electric conductivity of its CES should signifi
cantly reduce energy losses in the TIC, which in the
conventional modes of operation (without CES) are
primarily associated with a relatively high work func
tion of the collector (
ϕ
c
~ 1.5
eV), energy consump
tions for the ionization of cesium atoms, and charge
transfer in the electrode space resulted in arc loss of
output voltage
V
d
. The value of
V
d
0.5
eV is character
istic of weakly ionized cesium plasma of TIC, when
the electrical current of density
j
= 1–100 A/cm
2
flows
through the plasma.
3. EXPERIMENTAL
Key experimental studies confirmed the formation
of the Rydberg matter in the interelectrode medium of
TIC were performed by two groups of researchers:
Led by L. Holmlid at the University of Gothenburg
(Sweden) in the 1990s;
—Supervised by V.I. Yarygin at the Institute of
Physics and Power Engineering (Obninsk, Russia) in
the early 2000s.
The results of both the Gothenburg and Obninsk
groups were obtained in a lowtemperature laboratory
TIC (a plasma diode with the electrodes of flat geom
etry). The conversion of thermal energy into electric
energy was performed using cesium vapor dynamically
supplied into the interelectrode space through a perfo
rated collector coated with carbon. An arc discharge
was created in the TIC with lowtemperature cesium
plasma between an emitter (molybdenum in Gothen
burg and platinum Obninsk) and a nickel collector. The
condensate of excited states of cesium atoms in such a
converter occurred only after electricaldischarge acti
vation of the collector at temperatures 650–750 K,
which led to a substantial increase (2–3 times) of its
efficiency.
It was found that the increase in the TIC efficiency
is directly related to a decrease in the work function of
the collector electrons and a reduction in the inter
electrode resistance and the associated energy con
sumption to maintain the arc mode between the emit
ter and collector in the quadrant of the current–volt
age characteristic, in which the generation of constant
current and voltage occurs. To quantify such con
sumption, a generalized efficiency index, that is, the
barrier index (
V
b
), is used, which is the sum loss of the
potential energy of an electron released from the emit
ter as a result of thermal emission as it moves through
the interelectrode medium and through the surface of
the collector into the external circuit (the resistance of
useful electrical load)
V
b
ϕ
c
+
V
d
.
The lower the barrier index, the higher electrode
efficiency (excluding loss for the “external” electrical
resistance). Recently attained values of the barrier
index for TICs in conventional (nonRydberg) modes
are approximately 2.2–2.1 eV; the electrode efficiency
is 8 and 12% at the corresponding emitter temperature
of 1600 K or higher. It follows from the results of long
term research on the efficiency of TICs with different
materials of electrode pairs and workflow patterns of
the thermionic energy conversion.
The efficiency factor of the order of 20–26% was
obtained in the Gothenburg University and the Insti
tute of Physics and Power Engineering in the TIC only
with the CES of cesium. Let us consider these results
in more detail.
3.1. Experimental Thermionic Converter
The group of Prof. L. Holmlid conducted complex
investigations, in which the Rydberg matter was exper
imentally discovered for the first time, in an “open”
TIC. In this device, cesium vapor was continuously fed
to the molybdenum emitter through a mesh nickel col
lector, which was coated with a thin layer of carbon by
depositing a colloidal solution of graphite (“aquadag”).
After clusters of cesium vapor passed through the
interelectrode medium with the formation of the Ryd
berg matter, cesium was condensed on the cold walls of
the vacuum chamber, into which the “open” TIC was
placed. In these experiments, the highest at that time
effectiveness of TIC was first recorded, corresponding
to
V
b
= 1.64 eV at the work function of
ϕ
c
= 0.64 eV in
the interelectrode medium with the Rydberg matter.
The formation of the Rydberg matter was confirmed
by mass spectrometry of the interelectrode medium
and the appropriate form of the current–voltage char
acteristic (CVC).
Electron
gas density
Free
electrons
Io
n core
R
n
Fig. 1.
Schematic diagram of the formation of a plasma
crystal of the cesium CES (Rydberg matter);
R
n
is the
radius of a Rydberg atom, and
n
is the principal quantum
number.
548
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY B Vol. 9 No. 4 2015
YARYGIN, MUSTAFAEV
Surprisingly, these results of the Holmlid group
were accepted by scientific community in the field of
thermal emission with incredulity. The latter was
because the Holmlid group used a simplified workflow
pattern of the thermionic process in a diode with a belt
directchannel emitter (made of a molybdenum foil
2
×
1
×
0.02
cm in size) and a mesh poorcooled collec
tor with uncontrolled temperature. Using this diode, it
was impossible to compare the TIC characteristics in
the conventional equilibrium feed of saturated cesium
vapor into the interelectrode space and in the uncon
ventional supply of cesium vapor through the collector
(we will call this dynamic supply). The latter was pro
posed and patented by Holmlid and colleagues [12].
Indeed, nonisothermality, nonequipotentiality of
electrodes, possible effect of impurities from residual
gases in the vacuum chamber, presence of poorly con
trolled edge effects at the electrodes, and inability to
compare the characteristics of the “open” and con
ventional TIC, certainly, increase the systematic
experimental error of measurements and their inter
pretation. All this has made the findings of the Holm
lid group ambiguous and reasonably criticized by
experts in the field of thermal emission.
Unfortunately, these circumstances slowed down
the practical application of the Rydberg matter in
TICs. It took a decade to realize the importance of
these results and create a better experimental TIC, in
which the above disadvantages have been eliminated.
We compared for the first time the characteristics of
the processes with conventional and dynamic supply
of cesium vapor into the interelectrode space under
the same conditions. The original collector unit for
such a TIC has been kindly provided by R. Svensson
from the Holmlid group.
Experimental studies of the characteristics of the
TIC not only qualitatively confirmed the experimental
results of Holmlid, but also significantly expanded the
physical representation of a highperformance low
temperature TIC of new generation. The range of vari
ation of energy performance and internal parameters
of the thermionic workflow with the dynamic feeding
of cesium vapor was quantitatively determined.
Studies were conducted using a laboratory TIC
with the flat geometry of electrodes and the electrode
pair of Pt (emitter)–Ni + C (collector). A laserperfo
rated nickel foil (
4
×
4
mm
2
, 121
holes of diameter
0.1 mm at a pitch of 0.4 mm) was used as a collector.
The emitter 14 mm in diameter and 11 mm in thick
ness was made of polycrystalline molybdenum of vac
uum melting; a platinum coating 3
μ
m in thickness
was deposited to its end surface by magnetron sputter
ing. The emitter was heated by electron bombardment.
Its temperature was measured by five tungsten–rhe
nium thermocouples and an optical micropyrometer.
The collector temperature was measured using three
chromel–alumel thermocouples. The interelectrode
gap was adjusted in the range of 0.1–1.5 mm. Non
working surfaces of the emitter and collector were
shielded by ceramic rings and bushings of leucosap
phire. At the stage of degassing and preparation for
filling with cesium, the vacuum cesium communica
tion and the TIC were pumped with NORD100 high
vacuum magnetic discharge pumps. The thermionic
energy converter included two leucosapphire win
dows, through which optical measurements were per
formed, such as visual observation, photo and video
recording of the processes in the interelectrode gap
and the surrounding space, measurement of the gap
(
d
), spectrometric measurements of radiation, and
laser scanning of the interelectrode medium.
Conventional mode of TIC
is the equilibrium supply
of cesium vapor into the interelectrode gap. The equi
librium vapor pressure of cesium in the working cavity
of the TIC was set by temperature (
Т
Cs
) of the cold
zone at the working tank with cesium (Csthermostat).
Unconventional mode of TIC with the formation of
the cesium CES (Rydberg matter)
is the dynamic sup
ply of cesium vapor into the interelectrode gap.
Cesium vapor was fed through a separate highpres
sure path to the perforated collector, passes through it,
fell into the gap, and took part in the working process
with the formation of the Rydberg matter, and then fell
into the TIC working cavity and, condensing on the
cold walls of the vacuum–cesium system and low
pressure paths, flew down into a collector of liquid
cesium. The amount of cesium was enough for several
hours of measurements. Then, a special warmed valve
was opened, and cesium was returned back from the
collector of liquid cesium into the working thermostat.
After that, the working cycle of measurements was
repeated.
A datameasuring system was used to measure the
total current–voltage characteristic of the TIC, taking
into account a hysteresis of the characteristic and
changes in the current direction. The current–voltage
characteristics were measured by pulsed scanning the
TIC electric current from the static operating point (at
current density
j
and output voltage
V
) usually selected
in the diffusion mode (nondischarge mode). The com
plex ensured the synchronization of the CVC mea
surement with the recording of the optical emission
spectrum of the interelectrode medium by generating
an external trigger pulse of the optical spectrometer at
three different points of the current–voltage charac
teristic of the TIC.
The procedure for the thermal activation of the
collector under the dynamic supply of cesium vapor
was similar to that described in the publications of the
Holmlid group.
3.2. Optical Measurements
To record the spectral composition of the TIC radi
ation, a spectrometric complex based on an S1502
3648USB highspeed spectrometer was applied. The
plasma radiation was transmitted through the con
denser by a twochannel optical fiber to the spectrom
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY B Vol. 9 No. 4 2015
CONDENSATE OF CESIUM EXCITED STATES (RYDBERG MATTER) 549
eter. The position the inlet of the optical fiber was
installed in the image plane of the gap formed by the
condenser and adjusted to the maximum emission
intensity of the plasma. The recording system of the
spectrometer was connected to a USBport of a per
sonal computer. A reliable synchronization of the
detector controller with the recording of the TIC char
acteristics during the measurements was assured. The
exposure time of the spectrometer ranged from 7.4 to
22 ms.
Figure 2 demonstrates the photographs of the
interelectrode space of the laboratory TIC (a) in the
conventional mode (without CES) and (b) upon the
dynamic supply of cesium vapor (with CES). Drop–
plasma fractions observed in the experiment with the
cesium CES were pale shade of light green.
It can be stated from the measurements that the
optical spectra obtained in the modes with conven
tional and dynamic supply of cesium are not signifi
cantly different within the first ~25 h after the dynamic
supply up to the wavelength of nm. The
peculiarities of the spectrum at higher values of
λ
are
currently being analyzed.
Single bright (luminous) “objects” (condensed
cesium clusters), detected in the medium containing
the cesium CES, are of particular interest. The mea
surements were carried out by raster laser scanning,
which is commonly used to determine the coordinates
and velocities of microparticles in gas flows. A contin
uous He–Ne laser with power 25 mW and
λ
= 632 nm
was applied. These “objects,” seems to be clusters of
cesium CES combined in “large” conglomerates, can
be divided into two categories: “small objects,” which
appeared in the frames as thin rectilinear trajectories,
and “large objects” of irregular shape. The velocities of
“small objects” were evaluated as a ratio of the path
length to the exposure time, which in our experiments
was
10
–4
s, and were in the range of 1020 m s
–1
.
“Large” luminous “objects” resembled decaying
“fog” and had linear dimensions of 1–4 mm. Drops of
λ
1050
liquid cesium (not in the CES state) usually appeared
as dark spots and scatter with a substantially lower
speed of 0.05–0.1 m s
–1
. Unfortunately, more detailed
information about the luminous “objects” in the
medium containing the cesium CES is yet to be given.
3.3. Electrophysical Measurements
Recall the main features of formation and the exist
ence of the Rydberg matter, established by the Holm
lid group:
—The main condition are the presence of carbon
at the collector, dynamic supply of cesium vapor into
the interelectrode gap through a perforated nickel col
lector, arc discharge in the cesium thermionic inter
electrode medium, and preliminary (preceding the
formation of the Rydberg matter) activation of the
electrodes (collector) in the lowtemperature cesium
discharge.
—The main features of the formation of the Ryd
berg matter are a gradual transition of the current–
voltage characteristic from the 2nd to the 1st quadrant
(quadrant of the electric power generation) with a
gradual decrease in
V
b
, achieving high performance of
TIC and
V
b
~ 1.6
eV, and lowering of the work function
of the collector to
ϕ
c
~ 0.7
eV in the interelectrode
medium with the Rydberg matter, which is manifested
in the growth of reverse electron current.
The most important for the “open” TIC experi
mental results obtained by the Holmlid group, which
stimulated the beginning of our research, are mass
spectrometric measurements: a peak of
Cs
+
clusters
containing 5 to 13 atoms was found in the mass spec
trum. The quadrant of CVC, corresponding to the
generation of electricity, is called a “ECSmode.” It is
found that in the “ECSmode” with a Mo–(Ni + C)
collector, an increase in
j
yields a broad peak of the
RM clusters (CES) of cesium, which can combine up
to a few thousand (
~2000
amu) of excited cesium
atoms.
Emitter
Luminescence
of Csclusters
(drop–plasma
fraction)
Collector
(a) (b)
Fig. 2.
Interelectrode space of the arc cesium TIC in the working process of energy conversion (a) without CES and (b) with CES
of cesium.
550
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY B Vol. 9 No. 4 2015
YARYGIN, MUSTAFAEV
Reviewing our main experimental results obtained
in the TIC with the PT–Ni electrode pair, we compare
them, on the one hand, with the data of the Holmlid
group and, on the other hand, with the characteristics
of the same TIC at the equilibrium supply of cesium
vapor into the interelectrode gap. First of all, it should be
noted that, indeed, in the activation process at the
dynamic supply of cesium, a gradual shift of the current–
voltage characteristic from the 2nd to the 1st quadrant is
observed with the simultaneous decrease in
V
b
.
In the process of optimization of the CVC for
T
c
,
T
Cs
, and
d
, we managed to obtain performance supe
rior to the results of the Holmlid group. The results of
the emission measurement of the collector work func
tion
Φ
c
=
f
(
T
c
/
T
Cs
)
are shown in Fig. 3. Here, curve
2
corresponds to the mode of equilibrium supply of
cesium after 25 h of operation of TIC with the Rydberg
matter, and data points
1
present the experimental
data for the mode of dynamic feeding of cesium.
For pure metals in cesium vapor, the minimum
work function is at
Φ
c
= (1.5
±
0.1)
eV. In our case, the
work function of the collector reaches in minimum
value
Φ
c
= 1.0 eV. Approximately 25 h after the forma
tion of the cesium CES, the minimum work function
of the collector, even at the equilibrium supply of
cesium, changed in size only slightly.
It is found for the first time that after the formation
of the cesium CES in the dynamic mode, the emission
characteristics of the TIC collector were practically
the same after 25 h, and they occurred to be much
more effective than the characteristics obtained in the
conventional mode. At time more than 25 h, the char
acteristics of the TIC with the cesium CES deteriorated
and gradually become conventional with
V
b
2
eV.
Apparently, we can state that after formation of the
cesium CES at the collector CES, this state can be
maintained for at least 25 h.
The characteristic features of the current–voltage
characteristic of the TIC with the cesium CES and
with the Pt–Ni electrode pair in optimizing the mode
with the dynamic supply of cesium vapor at a relatively
low temperature emitter of
~1300
K are presented in
Fig. 4. It should be noted that, according to our esti
mates, the partial pressure of cesium vapor in the
interelectrode gap after its reduction and with the
dynamic supply of cesium to the holes of perforated
collector is approximately ten times less than the equi
librium pressure corresponding to
T
Cs
in the cesium
reservoir of the system for supplying cesium vapor into
the gap. Optimization of the modes of TIC with the
cesium CES for different applications in the terrestrial
thermionic energetics of direct conversion, according
to our experiments, demonstrates that high efficiency
of TICs (20%) can be achieved, and, accordingly, they
are attractive to potential practical applications [26–29]
implemented at a low calorific intensity of TIC (
Т
e
~
1400
K,
Т
c
~700
K). Low
Т
c
and the longterm exist
ence of the cesium CES correlate with a relatively high
melting point of the Rydberg matter and the possibility
of its longterm (metastable) existence, predicted by
theorists.
4. CONCLUSIONS
In the first stage of comprehensive experimental
research of the characteristics of a laboratory TIC with
the dynamic supply of cesium vapor through a perfo
rated (Ni + C)collector into the interelectrode space,
the qualitative results on the formation of the cesium
0.9 1.61.0 1.41.2
1.0
1.1
1.2
T
c
/
T
Cs
Work f unc t io n, e V
1
2
Fig. 3.
Work function of Nicollector of the TIC in the
modes with the formation of the cesium CES: (
1
) dynamic
supply of Cs and (
2
) conventional mode with equilibrium
supply of Cs (after 25 h of operation in the mode with
CES).
0.1 0.8–0.2 0.60.40.20
1
10
40
1
2
3
4
5
V
b
= 1.75 eV
V
b
= 1.59 eV
Current density, A/cm
2
Vol ta ge , V
Fig. 4.
Optimization of the TIC characteristics under the
dynamic supply of cesium vapor into the interelectrode
gap (
d
= 0.3 mm) at the following temperatures: (
1
)
T
e
=
1302 K,
T
c
= 776 K, and
T
Cs
= 648 K; (
2
) 1301, 740, and
653 K; (
3
) 1300, 726, and 655 K; (
4
) 1290, 718, and 657 K;
and (
5
) 1294, 696, and 662 K.
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY B Vol. 9 No. 4 2015
CONDENSATE OF CESIUM EXCITED STATES (RYDBERG MATTER) 551
CES (Rydberg matter), obtained by the Holmlid
group, are confirmed. In the second stage, the experi
mental database on emission–adsorption characteris
tics of the electrode and the current–voltage charac
teristics of TICs with the interelectrode medium con
taining the cesium CES is greatly expanded
Reducing the barrier index to
V
b
1.6
eV and,
thereby, increasing the electrode efficiency factor up
to 20–25% at relatively low emitter temperature
Т
e
=
1600–1800 K and collector temperature
Т
c
~ 700
K are
surely related to a decrease in the loss of voltage gener
ated by TIC by means of the formation of cesium CES.
In addition, the work function of the collector (
ϕ
c
1
eV
compared with
ϕ
c
1.5
eV in the conventional mode)
is associated with a decrease in transport (arc) losses
for the formation of cesium ions and their transfer
across the interelectrode space from the emitter to the
collector.
The resulting experimental database with the cur
rent–voltage characteristics of the TIC with the inter
electrode medium containing the cesium CES sets us
in a position to proceed for the first time to the stage of
project justification of the possibility of creating high
efficiency lowtemperature cogeneration thermionic
power generating systems.
The results of studies of the Rydberg matter by dif
ferent groups at the current stage of research efforts is
difficult to overestimate, because any knowledge of the
existence of a new form of matter, in this case, the
proof of formation of a metastable form of matter in
the form of a Rydberg substance or a condensate of
excited states, are priceless.
ACKNOWLEDGMENTS
Experimental studies in the field of plasma thermi
onic energetics are supported by the Russian Science
Foundation and the Ministry of Education of the Rus
sian Federation from 2003 to 2013.
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Translated by O. Zhukova
... The surface of the collector, free of holes, was previously covered with a thin layer of graphite. At the same time, according to authors [3,12,13], it was necessary to activate the electrodes for at least one hour before the experiment under the following conditions: emitter temperature TE = 1570 K, collector temperature TC = 670 K, temperature of the cesium reservoir TCs = 570 K. ...
... This methodology allowed the authors of [3,12,13] to perform experiments with laboratory TECs that made it possible to compare the characteristics of the converter both when pumping Cs vapor through the collector (dynamic feed) and when feeding them into the IEG from the cesium reservoir (equilibrium feed) in single experiment. ...
... Microanalysis of experimental TEC collector surface was performed by authors of [3,12,13]. Fig. 5 shows the scanning electron microscopy (SEM) image of the collector surface (the secondary electron mode at beam energy of 20 keV) [13]. To find out the nature of dark concentric rings visible around the holes in Fig. 5, SEM images with higher magnification were obtained in [3,12,13] both inside the ring region and outside of it. ...
... We performed an independent study of similarly pre- pared TIC but introduced some improvements. [21][22][23] We com- pared TIC operation in a standard configuration where Cs was introduced into inter-electrode gap from a side and in the enhanced regime where cesium vapor was flowing through the collector holes. The thermionic energy converter with such a collector demonstrated high heat-to-electric power conversion efficiency up to ∼20% at Т Е = 1570 K and Т С = 670 K. ...
... In the central part of the collector (4 × 4 mm), 121 holes of 0.07 mm diameter were drilled by a pulsed laser. 22,23 The emitter was heated by an electron beam. The mea- surement of the electrodes temperature was performed by five tungsten-rhenium micro thermocouples as well as an optical micropyrometer. ...
... It is well known that energy efficiency of TIC most depends on the so-called barrier index-sum of the Φ C and the volume losses of energy for the plasma creation w C (which cannot be really adjusted in TIC construction). Achieved value of col- lector work function Φ C ¼ 0:95 eV and w C ¼ 0:64 eV 22,23 corresponds to Barrier index of 1.59 eV. As can be seen from Fig. 3, 22,23 the TIC estimated efficiency rate is more than 20%. ...
Article
A thermionic energy converter with a nickel collector and cesium vapor as a working gas was studied, and an abnormally low value of the surface work function of ≈1 eV was obtained if the collector was covered by a thin carbon layer. Scanning electron microscopy x-ray microanalysis data of the elemental composition of the collector's surface after its long exposure to plasma indicate that the carbon structure was intercalated with cesium atoms, and this change to surface structure can be a reason for the anomalously low work function ∼1 eV. The thermionic energy converter with such a collector demonstrated high heat-to-electric power conversion efficiency up to ∼20%.
Article
Full-text available
The phase diagram of cesium is complemented by an isolated region of metastable states of a strongly nonideal plasma.
Article
The field reversal method was used to study the kinetics of Cs and Cs+ desorption from a pyrolytic graphite basal surface. Double-exponential decay was observed especially at high temperatures. Desorption of ions using an external flux from a Cs beam gave the primary rate parameters 2.60 eV and 5.3 × 1014 s−1, at T = 1100–1600 K. The secondary rate parameters were 0.28 eV and 2.2 × 105 s−1, observed at T = 1250–1600 K. Due to the high sensitivity of the method, the kinetics of desorption of the previously absorbed Cs, diffusing out from the bulk crystal, could also be studied. These processes were more complex, giving the primary rate parameters 1.87 eV and 1.1 × 1014 s−1, and the secondary rate parameters 2.07 eV and 1.97 × 1011 s−1 for T = 1400–1600 K. The variation of the primary and secondary rates and the field reversal peak heights as functions of retarding field time were also studied, as well as the field reversal peak variation with temperature. These results, as well as the ones found in previous studies of this system, indicate the existence of three adsorbed states on the more or less polycrystalline graphite surface. One apparently ionic state correlates with the diffusing state in the crystallites and with ionic states outside the surface. Conversion processes to and from this state, induced by the external field, were also observed.
Article
Experimental thermionic energy converters of an open type, i.e. with no closely located surrounding walls, as proposed here, have many advantages compared to conventional enclosed converters. Interactions with and problems of the enclosure do not interfere with the fundamental plasma and surface processes, which can be studied efficiently in an open converter, for example by mass spectrometry, optical spectroscopy, electron energy analysis and surface analytical methods. An open converter has been built and tested, where the necessary alkali vapour is supplied by a molecular beam type source with 400 laser bored effusion holes. The source acts as collector in front of a directly heated emitter. An ignited mode behaviour can be reached easily. The examples of results presented for Mo and Pt emitters at 1600–1700 K, a Cs plasma and nickel collector give a power density of 1–2 W cm–2 and a minimum barrier index of 1.95–2.1 eV and indicate a behaviour similar to enclosed converters. Thus, results for new surfaces, new additives etc. found in open converters should be of direct relevance for the development of normal enclosed converters.
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The condensation of excited atoms in a gas discharge is studied experimentally. A wide band shifted toward the red part of the spectrum is found to appear in the Rydberg series of the sodium spectral range when sodium vapor is added to an argon discharge. The formation of spherical plasma objects is observed.
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Results are presented from theoretical investigations of Rydberg matter in beryllium, magnesium, and calcium by the Hartree-Fock method with allowance for the width of the atomic levels. It is shown that conditions can be created for the formation of Rydberg matter in beryllium, magnesium, and calcium in the optical range of the excitation energies. On the whole, calcium is the most perspective for the search of condensate of long-living excited states.
Article
The results of experimental study of a condensate of cesium excited states (Rydberg matter) are presented. The possibility of condensate formation was predicted theoretically first by Prof. É.A. Manykin and coauthors from the Russian Research Center Kurchatov Institute and experimentally observed by L. Holmlid and coauthors from the Chalmers University, Sweden. In a thermionic energy converter with interelectrode medium, where, according to the data of Swedish researchers, Rydberg matter is formed, we observed similarities and distinctions between our and Swedish data on the formation of a condensate of cesium excited states.
Article
Theoretical investigations of the properties of Rydberg matter, more precisely, a nonideal ultracold plasma, which is one of the forms of this matter, are reviewed. Monte Carlo and molecular dynamics studies indicate that structures with both short- and long-range orders can be formed and that the recombination coefficient in the case of strong nonideality, can be several orders of magnitude smaller than that under ideal conditions. These and other results obtained in the past several years are discussed.
  • V I Yarygin
  • V N Sidel'nikov
  • I I Kasikov
V. I. Yarygin, V. N. Sidel'nikov, I. I. Kasikov, et al., Tr. Regional. Konkursa Nauch. Proekt. Obl. Estestv. Nauk, RFFI KNTs, No. 8, 199 (2005).
  • E A Manykin
  • M I Ozhovan
  • P P Poluektov
E. A. Manykin, M. I. Ozhovan, and P. P. Poluektov, Priroda (Moscow, Russ. Fed.), No. 1, 22 (2001).