A continuous point-like laser discharge of record high temperature has been produced in argon at atmospheric pressure with focusing of the radiation of the Novosibirsk terahertz free electron laser ...(NovoFEL). According to spectral measurements, the temperature in the center of the millimeter-sized plasma sphere was 28000 K at a plasma density of 1.5×1017 cm-3 and an average NovoFEL power of 200 W at a wavelength of 130 μm (2.3 THz).
At the Budker Institute of Nuclear Physics, Siberian Branch, Russian Academy of Sciences, work is underway to create a new flat undulator with a variable period and an enlarged aperture. The magnetic ...blocks of this undulator can also be used to create a variable period spiral undulator. This article presents the results of calculations of the magnetic field of such a spiral undulator.
In many cases, users of contemporary undulator-based x-ray sources exploit the relatively narrow spectral width of the undulator radiation in the forward direction. In this paper, we discuss the use ...of a distributed optical klystron, i.e., an optical klystron with several magnetic bunchers, to minimize the linewidth of the undulator radiation. We compare this approach with the common use of high-order harmonics of the undulator radiation.
A new variable-period undulator for the Novosibirsk free electron laser facility (FEL) is being developed at the Budker Institute of Nuclear Physics. The undulator has an enlarged aperture, so it ...uses permanent magnets with a nonstandard shape. In this article, the design of the measuring stand is described and preliminary results of measurements of the parameters of the magnet are presented.
A possibility of fast rapid temperature changing for the studied compound makes it possible to study related phenomena, such as thermally induced trapping of metastable states in magnetoactive ...compounds and thermally activated catalytic and biological processes. The Electron Paramagnetic Resonance (EPR) spectroscopy station at the Novosibirsk Free Electron Laser (NovoFEL) allows one to study effects of powerful terahertz (THz) radiation on the spin state of paramagnetic systems. A change in the sample temperature as a result of radiation absorption is an inevitable consequence of such an exposure. However, the sample heating at the NovoFEL EPR station itself is of interest due to the record power of THz radiation and small sizes of the samples used. A combination of these two factors can provide a significantly high heating rate. The magnetoactive complex Cu(hfac)
2
L
Et
was chosen as a model system for studying the heating process, since the complex has a magnetostructural transition at ∼125 K with substantially different spin states above and below the transition temperature. The heating processes with the amplitudes above 60 K were studied, the heating and cooling rates of the sample in similar experiments were estimated, and prospects for using the method to study various thermally induced effects are discussed.
Variable period undulators (VPUs) have a number of advantages over conventional undulators, but until recently they have not been used in free electron lasers (FELs). In the summer of 2021, such an ...undulator was installed on the second track of the Novosibirsk free electron laser, and lasing in the spectral range of 15–120 μm was obtained. This article describes the design of this undulator and presents the results of measurements of the radiation parameters.
This paper proposes ideas based on triply periodic surfaces of the minimum energy. A large number of structures can be described by a limited number of minimal surfaces. There is a certain connection ...between the symmetry of the surfaces, space groups, and structures.
In this study, we accurately measured the breakdown thresholds in four atmospheric gases using the high-power terahertz radiation of the Novosibirsk free electron laser (NovoFEL). The breakdown ...intensities of the 130-μm radiation in a form of 74-ps pulses were equal to 1.1–1.4 GW/cm
2
. These data have been compared with calculations based on a phenomenological criterion for a breakdown and the classical theory of stochastic microwave heating of electrons. Presented are threshold conditions for a quasi-continuous plasma discharge that is maintained by means of a sequence of pulses of the NovoFEL. At a pulse repetition rate of 5.6 MHz, the discharge quenching thresholds are 15–60% lower than the breakdown thresholds depending on the amount of plasma emerging.
Using computer methods (the ToposPro software program), a combinatorial-topological analysis and modeling of the self-assembly of crystal structures of the Sr
12
Mg
20
Ge
20
-
oP
52 (
a
= 21.707 Å,
b
...= 4.483 Å, c = 18.456 Å, V = 1795.88 Å
3
,
Pnma
), Sr
2
LiInGe
2
-
oP
24 (
a
= 7.503,
b
= 4.619,
c
= 17.473 Å, V = 605.63 Å
3
,
Pnma
), and Sr
2
Mg
2
Ge
2
-
oP
12 (
a
= 10.882 Å,
c
= 5.665 Å, V = 670.8 Å
3
,
Pnma
) families is carried out. For the crystal structure of Sr
12
Mg
20
Ge
20
-
oP
52, 17 variants of the cluster representation of a 3D atomic grid with 2 (5 variants), 3 (6 variants), and 4 (6 variants) structural units are established. The variant of the self-assembly involving the triple rings
K
3 = 0@3(SrMgGe) and
K
3 = 0@3(Mg
2
Ge) and double tetrahedra
K
6 = 0@6(Sr
2
Mg
2
Ge
2
) with symmetry –1, forming a suprapolyhedral cluster-trimer A from clusters (SrMgGe)(Sr
2
Mg
2
Ge
2
)(SrMgGe) and the cluster trimer B from clusters (Mg
2
Ge)(Sr
2
Mg
2
Ge
2
)(Mg
2
Ge), is considered. For the crystal structure (Sr
2
Li)
2
(InGe
2
)
2
-
oP
24, framework-forming polyhedra in the form of double tetrahedra
K
6 = 0@6(Sr
2
Mg
2
Ge
2
) and triple rings
K
3 = 0@3(SrMgGe) are defined. For the crystal structure of Sr
2
Mg
2
Ge
2
-
oP
12, the framework-forming polyhedra are defined in the form of double tetrahedra
K
6 = 0@6(Sr
2
Mg
2
Ge
2
). The symmetry and topological code of the processes of self-assembly of 3D structures from clusters-precursors has been reconstructed in the following form: primary chain → layer → framework.
The combinatorial-topological analysis and self-assembly of crystal structures of Yb
72
Sn
46
-
tP
118 (
a
= 11.076 Å,
c
= 36.933 Å,
V
= 4530.86 Å
3
, pr. group
P
4/
mbm
) intermetallic compounds is ...modeled using computer methods (the ToposPro software program). For the crystal structure of Yb
72
Sn
46
-
tP
118, 195 variants of a cluster representation of a 3D atomic grid with 5 (24 variants), 6 (86 variants), and 7 (85 variants) structural units are established. The variant of the fastest self-assembly involving three types of clusters-precursors forming layers of octahedra
K
6 = 0@6(Yb
4
Sn
2
) with symmetry
g
= 4/
m
, from polyhedra
K
11 = Sn@10(Yb
8
Sn
2
) with symmetry
g
= –1, and polyhedra
K
15 = Yb@14(Yb
10
Sn
4
) with symmetry
g
= 2 mm, as well as Yb and Sn spacer atoms, is considered. The symmetry and topological code of the processes of the self-assembly of 3D structures from clusters-precursors are reconstructed in the following form: primary chain → layer → framework.
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