FST transmission line for mass-

manufacturing of IFE targets:

Results of the IAEA RC #20344 (project duration 2016-2018)

Elena Koresheva (Chief Scientific Investigator),

Irina Aleksandrova, Evgeniy Koshelev, Andrei Nikitenko

P.N. Lebedev Physical Institute of the Russian Academy of Sciences, Moscow, Russia

8th IAEA RCM on"Physics and Technology of Inertial Fusion Energy Targets and Chambers",

March 8-9, 2018, Tashkent, Uzbekistan

IAEA RC #20344: FST transmission line for mass-manufacturing of

IFE targets (2016-2018).

MOTIVATION

■ A vital goal of IFE research is development of high-precision, mass production

techniques for cryogenic targets fabrication and their delivery to the reaction

chamber.

■ For laser IFE, these techniques must work with moving free-standing targets

(FST), and must be integrated into an FST production line capable of producing

~1 million targets each day.

■ Moving targets co-operate all stages of the fabrication and injection processes

in the FST transmission line that is considered as a potential solution of the

problem of mass target manufacturing.

THE PROJECT GOAL IS MATHEMATICAL & EXPERIMENTAL

MODELING of the FABRICATION & INJECTION PROCESSES of the FST

TRANSMISSION LINE for MASS MANUFACTURING of IFE TARGETS

■ The FST layering method developed at

the P.N. Lebedev Physical Institute (LPI) is

a promising candidate for development of

ICF transmission line at a high rep-rate

capability.

■ FST layering method works with moving

free-standing targets, which allows one to

economically fabricate large quantities of

such targets and to continuously (or at a

required rate) inject them at the laser focus.

■ In the project #20344 we consider a baseline design of high gain direct-drive

target developed by BODNER and coauthors [1]. We use this BODNER-Target to

examine issues affecting the possibility of its fabrication by the FST-layering

method.

PROJECT TARGET

[1] S. E. Bodner, D. G. Colombant, A. J. Schmitt, et al. High Gain Target Design for Laser Fusion. Phys. Plasmas,7, 2298, 2000

PROJECT BACKGROUND (1): Principle of the FST-layering method is the operation with moving free-standing targets

Cryogenic experiment

FST Layering Method Provides Rapid

Symmetrization & Formation of Solid Ultra-fine

Fuel Layers

(a) Schematic of the FST-layering module

(b) Target before layering («liquid+vapor» state of fuel)

(c) Target after FST-layering (symmetrical solid layer)

Target injection at a rate of 0.1 Hz from the

layering channel (LC) to the target chamber

a b

c

5

Test chamber

Fill Facility

Sabot shop

BLOCK #2

BLOCK #3

BLOCK #1

Rep-rate laser

SC

FS

T-l

ay

erin

g

mo

du

le

Assembly device

SC BLOCK #1: Reactor shells production - 2 - 4 mm

BLOCK #2: Cryogenic targets FST producing & assembly – D2-layer of 200-300 um-thick

BLOCK #3: Cryogenic injector Т < 20 К, v > 200 m/sec, ~ 5-15 Hz

PROJECT BACKGROUND (2): FST-TRANSMISSION LINE is a modular setup

for mass-manufacturing the IFE targets and their rep-rate delivery

SC = shell container

2ND YEAR ACTIVITY PROGRAM (2017)

I. Expert analysis of the basic requirements relevant to the

key science and technology issues

II. The existed mathematical model optimization relevant to

the shell container (SC) depressurization and IFE target

fabrication.

III.Experimental modeling on testing & benchmarking the

operational conditions of key elements of the FST

transmission line.

I. EXPERT ANALYSIS: FST-layering method developed at LPI

is the most promising technology for reactor applications

FST layering Performance data Meet the requirements

■ High cooling

rates

(1− 50 K/s)

Isotropic ultra-fine fuel

Shock wave propagation

via isotropic fuel layer

Minimal layering time

(~15 s)

Tritium inventory

minimization

■ High-melting

additives

(0.5% − 20%)

■ Vibration

loa ing

Grain size stabilization

Acceptable surface finish

High mechanical

strength &

high thermal stability

Target survival during

delivery

Fuel layering

in rolling

free-standing

targets

Uniform layer

formation

Acceptable target

quality

High rep-rate

fabrication &

Injection

Mass production &

sufficient price

- Depending on the cooling rate and the

experimental conditions (additives,

vibrations), the solid fuel layer can be in the

state with different grain size: isotropic ultra-

fine layers or anisotropic molecular crystals.

- Isotropic ultra-fine micro-structure of fuel

ensures the operating efficiency of IFE

power plant.

- The FST-layering method is a promising

candidate for creation of the FST-

transmission line intended for mass

manufacturing of IFE cryogenic targets.

Success of FST-layering method is use of

high cooling rates and high melting additives

to hydrogen isotopes. The amount of

additives was 20% of Ne in order to

modeling the role of tritium in DТ fuel.

METHOD FST + large additives: Fourier-spectrum of bright

band shows that layer roughness < 0.15 m for modes 20-30

MATHEMATICAL MODELING:

FST-layering time of the BODNER-target has been calculated

SCHEMATICS OF A DYNAMICAL LAYER

SYMMETRIZATION

In a moving batch, the shell rotation causes a liquid

fuel spread over the inner surface of the shell

BODNER-TARGET

FST-layering time – Results of calculations

■ D2−fuel

Temperature Time

ΔT = 35.0 К ― 18.73 K τform = 22.45 s

ΔT = 27.5 К ― 18.73 K τform = 12.05 s

■ D-T−fuel

Temperature Time

ΔT = 37.4 К ― 18.30 K τform = 28.52 s

ΔT = 28.0 К ― 18.30 K τform = 14.25 s

MOCKUP of a 3-FOLD SPIRAL LAYERING CHANNEL (LC): dimensions & results of experiment

− Number of spirals n = 3 − Tube diameter: ID = 4.4 mm, OD = 6 mm

− Spiral diameter ID = 30 mm, OD = 42 mm − Total spiral length L = 5136 mm

− Spiral height Н = 880 mm − Residence time:

− Inclination angle of the spiral = 16.70 ► Iron ball → τ = 31.3 s

− Total number of turns = 77 ► CH shell → τ > 35 s

■ Resume. BODNER-TARGETS CAN BE FABRICATED in the 3-FOLD SPIRAL LC BECAUSE the

FST-LAYERING TIME DOES NOT EXCEED 30 s for BOTH D2 and D-T FUEL.

R&D PROGRAM INCLUDES:

■ Measurements of the polymer shells strength with the goal to

optimize the stage of shell container (SC) depressurization.

■ Experimental modeling of the free-standing shells moving in

different layering channel (LC) mockups made from different materials.

■ Experimental modeling of the conditions of target positioning and

transport between the elements of the FST transmission line using type-

II superconductors.

EXPERIMENTAL MODELING:

Topic of the stu y − testing & benchmarking the operational

conditions of key elements of the FST transmission line

MEASUREMENTS OF THE POLYMER SHELLS STRENGTH with the goal to optimize the shell container (SC) depressurization stage

Tensile strength measurement at cryogenic temperatures (shells filled with H2 gas)

The moment of the shell

damage by H2-gas inner

pressure, T = 300 K

T = 35 K, inner gas

pressure P~ 14 atm

Damage of 3 shells.

T = 41.5 K, P~ 18 atm Damage of the last shell.

T = 61.5 K, P~ 32 atm

Pdamage= 2 (R/R)

RESUME: TENSILE STRENGTH OF POLYSTYRENE SHELLS IS INCREASED AT

TEMPERATURE DECREASING

- it is increased on average by a factor of ~ 1.9 at temperature decreasing from 300 K to 200 K

- it is increased on average by a factor of ~ 4.5 at temperature decreasing from 300 K to 60−40 K

Tensile strength for different T and

different shell aspect ratios

calculated from the measured

pressures

R/ΔR

1, kg/сm2 2, kg/сm

2

1/2 Т =300К Т = 200К

50 140 250 1.79

42 126 246 1.95

33 99 216 2.18

Tensile strength of the polystyrene shells

at cryogenic temperatures

Pfill

(atm)

Shell

diam.

(µm)

Layer

thickness

(µm)

Damage

T

(K)

Damage

P

(atm)

Tensile

strength

(kg/cm2)

205 955 27 61.5 32 670

305 940 39 63.5 47 552

445 949 54 46 35 415

765 983 88 43 38 465

EXPERIMENTAL MODELING: measurements of the time of targets

movement in the layering channel mockups

A number of mockups of the LC of different geometry have been fabricated

over the period of 1st and 2nd Project Year (2016-2017), and used in the

experimental modeling of the 2nd Project Year

Schematics of measuring

the time of target movement

inside a spiral LC (1 is the optronic pair made from the IR-

diodes).

(a) (b)

(c)

LAYERING CHANNEL MOCKUPS

a – single-spiral LC,

b – double-spiral LC,

c – 3-fold-spiral LC

Time of targets movement in the LC mockups (measurement results)

3-M1

tmov:

21.4 s

(iron ball)

3-M2

tmov: 31.3 s (i. ball),

> 35 s (CH shell)

2-M1

tmov:

18 s (i. ball),

23.5 s (shell)

1-M2

tmov:

16.4 s

(CH shell)

1-M1

tmov: 9.8 s

(CH shell)

GLASS MOCKUP

tmov :

2.7 s (iron ball),

8.4 s (CH shell)

RESUME

Main requirement: form < tmov

1. The calculated FST-layering

time does not exceed 30 s,

which is a necessary condition

for target mass manufacturing

form = 12.05 -to- 22.45 s (D2)

form = 14.25 -to- 28.52 (DT)

2. The BODNER-target can be

uniformly fabricated in n-fold-

spiral LC at n = 2, 3

SABOT is used for

Concept of the device for Target-&-Sabot high rep-rate assembly

• to transfer target from the LM to injector

• to transfer the pulse of movement on a

target inside the injector

• to protect target from the heat- & g- loads

arising during acceleration

“Sabot + Target” assembly

Works at T < 20 K

PROJECT BACKGROUND (3): SABOT is used at a stage of target

acceleration and injection into a reaction chamber

FST-LM

Sabot

loader E-m

linear accelerator

The method of cryogenic fuel target noncontact

delivery using the HTSC sabot has been patented

in RF in 2017. (with the Lebedev Phys.

Institute as the patentee)

EXPERIMENTAL MODELING: “Sabot + Target” acceleration in

linear electromagnetic accelerator

1. Anderson [1] and Chan [2] have proposed to apply

superconducting solenoid as a projectile. Unfortunately in

such acceleration scheme the translational movement of the

projectile has transverse instability.

2. In [3,4] we have proposed to use the noncontact delivery

system, which can stabilize the projectile (i.e. sabot)

movement in the accelerator. This delivery system is a

combination of the acceleration system and the levitation

system, which keeps a friction-free motion for providing an

efficient magnetic acceleration of the levitating HTSC-sabot.

3. POP experiments confirmed the benefits of our approach

Refs: [1] D. Anderson, et al. Z. Naturforsc. 26a, 1415, 1971; [2] K.W. Chen, et al. IEEE Trans. Nucl. Sci. NS-26(3), 1979;

[3] I.V. Aleksandrova, et al. J. Rus. Laser Res., 2018 (to be published); [4] E.R. Koresheva, et al. RF Patent №2635660,

November 15, 2017

SABOT material: high temperature superconductors

(HTSC) are under consideration in the IAEA RC # 20344

UNIQUE FEATURES OF THE NONCONTACT DELIVERY SYSTEM

It is a combination of the acceleration system (field coils for

generating the traveling magnetic waves) and HTSC levitation

system with a magnetic rail for providing the stable

levitation of the assembly «HTSC-sabot + Target»

Superconducting sabot which comprises not only the

accelerated HTSC-coils (as driving body), but also the HTSC-

plates providing the HTSC-sabot levitation.

1

2 (a)

(b)

ACCELERATION

EXPERIMENTS:

the gap between

HTSC-sabot & magnetic

rail is keeping unvarying

with time

NEW RESULT: NONCONTACT DELIVERY SYSTEM keeps a

friction-free motion for providing an efficient magnetic acceleration

of the levitating HTSC-sabot

EXPERIMENTAL MODELING:

Levitating HTSC-sabots acceleration by an electromagnetic pulse

along the permanent magnet guideway (PMG) system

Sequential frames of the HTSC-sabot

motion over the PMG under the action

of the driving electromagnetic pulse

generated by the field coil

a − HTSC-Sabot #1, v = 0.1 m/s

b − HTSC-Sabot #2, v = 1 m/s

Field Coil: 98 turns

ID 18.5 mm, OD 27 mm, H = 13.6 mm

Pulse: 200 A, 1 s, Bmax = 0.35 T

a b

(a) HTSC-Sabot #1 – “open parallelepiped” (b) HTSC-Sabot #2 – “hollow parallelepiped” HTSC: 2nd generation tape (SuperOx, Ltd.)

(a) (b)

MATHEMATICAL MODELING: Estimation of the main

parameters of the proposed noncontact acceleration system

■ MgB2-Driving Body Acceleration Efficiency for the BODNER-Target

TASK

PARAMETERS

INITIAL

PARAMETERS

RESULTS for MgB2-DRIVING

BODY at Ts = 20 K

Vinj − require spee 200 m/s

Msab − sabot mass ~ 0.5 g

r/rs − rfield coil/rMgB2-coil 5

B0 − external fiel → 1 T 0.5 T 0.25 T

Jc − critical current → 2500 А 4000 А 5000 А

a − acceleration → 800g 640g 400g

La − acceleration length → 2.5 m 3.125 m 5.0 m

HTSC-Sabot used in

calculations (schematics)

HTSC plate for sabot levitation

MgB2 coils as driving body

BODNER Target

OPERATIONAL PARAMETERS

■ ACCELERATION → а = 400g

■ INJECTION SPEED → Vinj = 200 m/s

■ ACCELERATION LENGTH → La =5 m

■ EXTERNAL MAGNETIC INDUCTION → B0 = 0.25 T

■ CRITICAL CURRENT in MgB2-DRIVING BODY → Jc = 5000 A.

Polymer matrix

MATHEMATICAL MODELING: Estimation of the levitation force

& levitation height for the HTSC-sabots used in POP experiments

LEVITATION PARAMETERS FOR DIFFERENT HTSC-SABOTS

►SABOT #1 (Gd123) − «open parallelepiped»: total mass 1.25 g

The levitation force is 0.0125 N that corresponds to a 3-mm levitation height

►SABOT #2 (Gd123) − «hollow parallelepiped»: total mass 0.97g

The levitation force is 0.0097 N that corresponds to a 2.5-mm levitation height

► SABOT #3 (Y123) − «open parallelepiped»: total mass 1.25 g

The levitation force is 0.0125 N that corresponds to a 5-mm levitation height

Sabot #3

■ Acceleration of sabot #1 over a linear PMG (a) and a

circular PMG (b) at T = 80 K (load capacity:1 spherical

target has 0.6 mg, 1 cylindrical target has 1.1g)

Sabot #1

Sabot #1 Sabot #1

Sabot #2

(a) (b)

SUMMARY RESULTS of IAEA RC #20344 (2nd year activity)

I. EXPERT ANALYSIS

- Depending on the cooling rate and the experimental conditions (additives, vibrations), the solid fuel layer

can be in the state with different grain size: isotropic ultra-fine layers or anisotropic molecular crystals.

- Isotropic ultra-fine micro-structure of fuel ensures the operating efficiency of IFE power plant.

- The FST-layering method is a promising candidate for creation of the FST-transmission line intended for

mass manufacturing of IFE cryogenic targets.

II. MATHEMATICAL MODELING

- The FST-layering time for IFE target : form = 12.05 -to- 22.45 s (D2) form = 14.25 -to- 28.52 s (DT)

- IFE target can be uniformly fabricated in n-fold-spiral layering channel at n = 2, 3

- Suitable choice of HTSC materials allows reaching the IFE target injection velocities 200 m/s under 400g at

5-m-acceleration length using the driving body from MgB2 superconducting coils at the external magnetic

induction 0.25 T and the critical current 5000 A

III. EXPERIMENTAL MODELING

- Target residence time in the 3-fold layering channel (LC) is about 35 s, and in 2-fold LC is about 23.5 s

which allows developing the FST-layering module using IFE target batch rolling along the LC.

- Tensile strength of polystyrene shells is increased at temperature decreasing, namely: it is increased on

average by a factor of ~ 1.9 at temperature decreasing from 300 K to 200 K, and it is increased on average

by a factor of ~ 4.5 at temperature decreasing from 300 K to 60−40 K. This data will allow to optimize the

stages of the shells depressurization and fuel layering.

- POP experiments have shown that HTSCs can be successfully used to maintain a friction-free motion of the

HTSC-sabot, and also to provide a required stability of the levitation height over the whole acceleration

length due to pinning effect.

The results obtained in the 2nd Year of the project has been published in a number of scientific Journals and reported on International conference

• List of publications and report

1. I.V. Aleksandrova and E.R. Koresheva. Review on high rep-rate and mass-production of the cryogenic targets for laser IFE. High Power Laser Sci. Engin., 5, e11 (1- 24), 2017

2. I.V.Aleksandrova, et al. Cryogenic hydrogen fuel for controlled inertial confinement fusion (Cryogenic target factory concept based on FST-layering method). Physics of Atomic Nuclei, 80 (7), 1-22, 2017

3. I.V.Aleksandrova, et al. Magnetic acceleration of the levitating sabot made from type-II superconductors. J. Russian Laser Research (accepted for publication)

4. I.V.Aleksandrova, et al. HTSC-maglev transport systems for non-contact manipulation, positioning and delivery of the IFE targets. Report #19, XLIV International conference on Plasma Physics and Controlled Fusion (Russia, Zvenigorod, Feb. 13-17, 2017); http://www.fpl.gpi.ru/Zvenigorod/XLIV/ I.html#SekcijaI

R&D PROGRAM of the 3rd YEAR ACTIVITY (IAEA RC # 20344)

■ Development of a concept of the FST transmission line for mass

manufacturing of IFE targets, including:

1. Mathematical modeling: computation a set of optimization LC parameters

(such as: number of spirals, inclination angle of the spiral, total length of the spiral,

its lead and diameter) for the BODNER-Target fabrication by the FST layering

method.

2. Experimental modeling:

― Determination of the target residence time during its transport through a LC

mockup with a spiral angle variation for the purpose of its optimization according

to the computation,

― Further study of the optimization conditions of noncontact target positioning and

transport between the elements of the FST transmission line.

3. Connection diagram of the key elements of the FST transmission line (FST-TL)

4. Functional description (compositions and processes) of the key elements of the

FST-TL taking into account the results obtained in the project.

Expected outputs for the 3rd year of the Project: a final version of the FST-

transmission line concept (it can be slightly changed by the 3rd year results)