Fig. 1. Three different designs of the fuel target. (a) DD target; (b) ID (i.e., hohlraum) target; (c) FI target. 1, shell wall; 2, D–T fuel layer; 3, D–T fuel vapor; 4, cylindrical converter; 5, guiding cone.

Fig. 2. Foam shells made in General Atomics (taken from Refs. [44, 65]). (a) A batch of foam DVB shells; (b) polished DVB shell of a 4 mm diameter with a 300 $\unicode[STIX]{x03BC}\text{m}$ wall, it is a prototype for the NRL IFE target design; (c) the scanning electron microscope (SEM) image shows the foam structure of a DVB foam; (d) SEM image of a section of the foam DVB shell with double outer coating from PVP and GDP.

Fig. 3. Sequence of video frames showing accelerated centering of inner silicone oil droplet by intentionally inducing elongation of the outer shell. (a) Before application of voltage; (b) a strong electric field $Eo=23~\text{kV}/\text{m}$ at 100 kHz is applied for ${\sim}15$ s; (c) field strength is reduced to 13 $\text{kV}/\text{m}$. The time required for the inner droplet to achieve centering is reduced from ${\sim}80$ to ${\sim}45$ s and this lower field strength sustains the concentric condition indefinitely (taken from Ref. [72]).

Fig. 4. Fuel pellets for laser fusion (taken from Refs. [37, 38]). (a) Plastic shells (CH, CD, CD–T) with diameter range of 0.5–5 mm; (b) plastic foam shell coated by plastic gas barrier.

Fig. 5. A batch of the re-entrant cones (taken from Ref. [39]).

Fig. 6. Fluidized bed with a massive of Au/Pd-coated PAMS shells of a 4 mm diameter. (a) Bed is out of the cryostat; (b) bed is inside the cryostat. Bed fluidized at 9 K (taken from Ref. [54]).

Fig. 7. First demonstration of dielectrophoretic behavior in a cryogenic liquid: electrostatic field has been used to levitate a column of liquid $\text{D}_{2}$ and form a droplet of the desired volume (taken from Ref. [77]).

Fig. 8. Schematics of target production via a multilayer cryogenic reactor (taken from Ref. [42]).

Fig. 9. Deposition of a protective cryogenic layer onto the outside of the shells placed in the R&B cell. (a) Shells with a crystalline powder of solid $\text{O}_{2}$ on their tops: (a1) shell #1 with an outer Pd coating of 15 nm thick and (a2) shell #2; (b) the same shells with uniformly distributed solid $\text{O}_{2}$: (b1) shell #1 and (b2) shell #2.

Fig. 10. High repetition rate and mass production of inexpensive fuel targets can be developed on the bases of the FST-transmission line as an integral part of any IFE reactor.

Fig. 11. FST-layering method provides a rapid symmetrization and formation of solid ultra-fine layers. (a) Schematic of the FST-LM (100-projection micro-tomograph is used for cryo target control^[97–99]); (b) target before layering (‘liquid $+$ vapor’ state of fuel); (c) target after FST layering (symmetrical solid layer); (d) single-spiral LC (1); (e) single-spiral LC (1) mounted with a TC (2); (f) fill chamber for filling the shells with highly pressurized gas fuel (1000 atm at 300 K); (g) elements of the SC.

Fig. 12. Spiral LCs in a (a) and (b) single- or (c) double-coiling geometry. The spiral material is copper in (b) and (c) and stainless steel in (a).

Fig. 13. Combined layering channel (CLC) which consists of two spirals: acceleration spiral (spiral 1, red coiling) and deceleration spiral (spiral 2, blue coiling). (a) CLC schematics; (b) mock-up of the acceleration spiral channel; (c) mock-up of the deceleration spiral channel.

Fig. 14. Illustrates of the operation principle of the FST-LM and shows the mutual alignment of the basic units. (a) An SC with a shell batch for repetition-rate injection of the filled shells to the LC [material for work with D–T fuel are low-carbon austenitic stainless steels, GOST 5632-72: 03Kh18N12 (304L), 03Kh18N10T, 03Kh17N14M3 (316L)]; (b) assembly procedure (1, cryogenic transport mechanism; 2, SC; 3, LC; 4, TC mounted in position 5); (c) cryostat (overall dimensions: $0.21~\text{m}\times 1.3$ m).

Fig. 15. In our research we have used the CH shells made at different laboratories. (a) The Thermonuclear Target Lab (diameter ${\leqslant}1.8$ mm LPI, Russia); (b) large CH shells (diameter ${\geqslant}1.8$ mm) have been delivered by the Science and Technology Facility Council (STFC, UK); (c) CH shells covered with a thin Pb layer have been delivered by the Institute for Laser Engineering (ILE, Osaka Univ., Japan).

Fig. 16. Repetition-rate target injection under gravity from the LC to the TC. (a) Target during injection, $T=4.2$ K; (b) target injection rate is 0.1 Hz (free target location in the TC, $T=4.2$ K); (c) target injection in to a cylindrical cavity (1, cavity before injection; 2, injected target inside the cavity).

Fig. 17. Other options for target injection and location in space. (a) Using tripod at room temperature; (b) using HTSC for noncontact manipulation, positioning and transport of the free-standing cryogenic targets to develop maglev systems (b).

Fig. 18. The FST facility for levitation experiments below 20 K: (1) closed-cycle optical helium cryostat (CryoTrade & CryoMech); (2) vacuum-pumping system (Pfeiffer); (3) optical control system; (4) sample holder with CH shell inside it; (5) CH shell.

Fig. 19. Levitation of CH shell with an outer Y123-layer. (a) Photo of ‘CH shell $+$ Y123-layer’ at room temperature (300 K); (b) ‘CH shell $+$ Y123-layer’ levitation at $T=80$ K over linear PMG; (c) ‘CH shell $+$ Y123-layer’ levitation at $T=18$ K in the TC of the cryostat.

Fig. 20. FST supply system (SS) for 300 kJ laser facility (ISKRA-6). (a) Geometrical arrangement of the FST-SS in the target chamber of the laser facility; (b) cryogenic target fabrication and gravitational delivery at the center of the target chamber.

Fig. 21. Different cooling rates give rise to the cryogenic $\text{H}_{2}$-layer formation with a different granularity. No additives are used in these experiments.

Fig. 22. High-melting additives to fuel (frames 2 and 4) are critically important as stabilizing agents to prevent the grain size growth.

Fig. 23. Success of FST-layering method is conditioned by synchronous use of high cooling rates and high-melting additives to hydrogen isotopes. (a) 550 $\unicode[STIX]{x03BC}\text{m}$ diameter glass shell; (b) 1.23 mm diameter CH shell. The amount of additives was 20% of Ne in order to modeling the role of tritium in D–T fuel; (c) a Fourier spectrum of the bright band of the cryogenic layer given in (b).

Fig. 24. Assembly of the R&B cell with the FST-LM. (a) Schematic of the experiment; (b) a general view of the optical TC with targets placed onto the cryogenic piezo-substrate (frames 1 and 2).

Fig. 25. Solid layers formation with a different microstructure using the cryogenic piezo-vibrator placed in the R&B cell. (a) $\text{D}_{2}$ (diameter ${\sim}1.35$ mm, $P_{\text{f}}=350$ atm); (b) $\text{H}_{2}$ (diameter ${\sim}1.5$ mm, $P_{\text{f }}=445$ atm).

Fig. 26. Design of the target SS based on the FST technologies: FST layering, protective cover generation (solid Xe, Ne or $\text{D}_{2}$), ‘target $+$ sabot $+$ cover’ repetition-rate assembly and positioning at starting point of the injector (coil or gas gun, or hybrid).

Fig. 27. Sabot used for test experiments on electromagnetic acceleration at cryogenic temperatures. (a) Target-&-sabot assembly; (b) general view of a set of sabots made from soft-magnetic iron of the ARMKO type; (c) cryogenic electromagnetic injector with one coil [c1, insert into the cryostat with the coil mounted on its top (c2)], (d) experimental results on the sabot velocity $v$ ($\text{m}/\text{s}$) at the coil output versus the parameter $J\unicode[STIX]{x1D714}$ (here $J$ is the current amplitude, and $\unicode[STIX]{x1D714}$ is the amount of turns of the coil) – maximal overloads achieved is $a=320$ g at $v=8~\text{m}/\text{s}$.

Fig. 28. Levitation of different HTSC-sabots. Linear PMG-system is three permanent magnets (NdFeB) and several soft ferromagnetic inserts; circular PMG-system is an NdFeB disk commercial permanent magnet (outer diameter $=$ 100 mm, inner diameter $=$ 50 mm), which is placed inside the soft ferromagnetic holder.

Fig. 29. Creation of the IFE power plant with number of reactors $N>5$ requires creation of the target factory of line production capable to work effectively with the $N$-number of reactors according to the following scheme: one driver – one target factory – $N$ reactors.