Target fabrication technologies and noncontact delivery systems to develop a free-standing target factory operating in the repetition mode at the IFE relevant level

Abstract

Realization of fusion energy imposes considerable challenges in the areas of producing cryogenic targets with an isotropic fuel structure and developing noncontact target delivery means. It was shown that the FST-layering method using high cooling rates (1–50 K s−1) and high-melting additives to fuel content (0.3%–25%) makes solid layers isotropic and free of local defects. FST-layering in line-moving shells is usually realized in a vertical single-spiral layering channel. Here we present our first results with a double-spiral layering channel (DS-LC). The cryogenic layers (D2 + 20% Ne) were formed in 5 shells (2R ∼ 1.8 mm) during their rolling in the DS-LC, and then they were gravitationally injected to the test chamber at T = 5 K. The obtained isotropic layers (W ∼ 87 μm) are stable in the temperature range from 5 K to T tp = 18.7 K of D2. The total layering time <20 s. Another critical issue is the noncontact target delivery. It is shown that using transport of high-temperature superconductors in the magnetic fields provides stable noncontact target acceleration placed in a superconducting sabot. The proof-of-principle experiments have shown that using only 1 field coil allows one to accelerate such sabot up to 1 m s−1. Computationally, it has been shown that acceleration up to a velocity of 200 m s−1 will require about 200 field coils (0.25 T each) along the 5 m-length of the linear accelerator with overloads a = 400 g; the velocity of 400 m s−1 will require the acceleration length of 20 m at the same a = 400 g. First steps are made to reduce the dimensions of the linear accelerator using a cyclic permanent magnet guideway with less than 10 field coils to achieve target injection velocities in the range of V inj = 200–400 m s−1.

A high-pinning-Type-II superconducting maglev for ICF target delivery: main principles, material options and demonstration models

“…Thus, the ability of the DT target to withstand overloads and overheating is a key in the target accelerator design. The scientific and technological issues associated with this task are as follows: (1) design bases must provide a noncontact target acceleration (i.e., without mechanical friction) to avoid heating the DT ice layer; (2) as a consequence, it removes the issue of developing cryogenic lubricants, the effectiveness of which at cryogenic temperatures (<20 K) is highly questionable; (3) it is desirable for accelerations imposed on the target to be within acceleration limitations; (4) design solutions must be rather compact to significantly reduce the target production costs; (5) design solutions must also be compatible with mass target fabrication and operation at high repetition rate (HRR) conditions [5] .…”

“…A cost-effective approach for ICF target supply was proposed at the LPI (see Figure 2). It is based on using free-standing and line-moving targets [5][6][7][8] to develop target fabrication and delivery technologies with an emphasis on repetition systems, which is referred to as the FST approach. Figure 2 uses the following notations: 1 -target, 2 -holder (working with a single target), 3 -a batch of free-standing shells filled with fuel, 4 -shell container (SC), 5 -layering module (LM), 6 -layering channel (LC), 7 -test chamber (TC).…”

“…A detailed description of the in-line FST production and multiple target protection methods for target delivery at HRR laser facilities, including the results achieved to date (experimental and theoretical), can be found in Refs. [5][6][7][8].…”

“…However, it is desirable to work at lower accelerations since the target must reliably survive the injection overloads without damage. In Section 3 we will define the conditions to achieve the required injection velocity without exceeding acceleration limitations.

Figure 1 Assembly of the HTSC-sabot + target, or HTSC-projectile (not to scale): (a) 1 – HTSC-housing, 2 – polymer insert with a target nest on its top, 3 – MgB 2 driving coils, 4 – cryogenic target; (b) 5 – mock-up of the HTSC-housing made from superconducting ceramics, ρ = 4 g/cm 3 [ 4 , 5 ] , 6 – hole for the polymer insert; (c) 7 – target shell, 8 – solid fuel layer, 9 – vapor fuel.

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“…Assembly of the HTSC-sabot + target, or HTSC-projectile (not to scale): (a) 1 – HTSC-housing, 2 – polymer insert with a target nest on its top, 3 – MgB 2 driving coils, 4 – cryogenic target; (b) 5 – mock-up of the HTSC-housing made from superconducting ceramics, ρ = 4 g/cm 3 [ 4 , 5 ] , 6 – hole for the polymer insert; (c) 7 – target shell, 8 – solid fuel layer, 9 – vapor fuel.…”