RU2534507C1 - Method of initiating nuclear fusion reaction and apparatus therefor - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: disclosed method of initiating a nuclear fusion reaction includes use of two targets, selecting as material of the first target deuterated polyethylene (CD₂)_n with thickness l₁ in the range of 1-10 mcm, generating deuterium ions from the back side of the ionised material of the first target under the action, on the front surface of said target, of a high-contrast laser beam of relativistic intensity and ultra-short duration with energy in the range of 10-500 J and contrast in the range of 10⁸-10¹⁰. The method provides acceleration of deuterium ions towards the second target to expose the surface layer thereof to the accelerated deuterium ions. The second target is a titanium target, the front surface of which is pre-activated with helium ions ³He. The second target is placed in a vacuum at a distance of 10-50 mm from the first target and deuterium ions moving towards its surface are accelerated to an energy which is sufficient to conduct the reaction D+³He→⁴He+p+18.3 MeV to obtain α-particles (⁴He) and protons p.

EFFECT: use of the invention with interaction of intense laser pulses with solid-state targets enables to lower special requirements for radiation safety when designing an apparatus for initiating nuclear fusion reactions.

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Description

The invention relates to nuclear and laser physics and technology, and can be used as a research tool and as a technological means of particle acceleration in laser physics to solve the problems of direct ignition of inertial fusion targets (see Nuclear fusion with inertial confinement. Current status and prospects for energy // Edited by B.Yu. Shirkov. - M.: FIZMATLIT, 2005 .-- 264 p.). Especially promising is the use of the invention to initiate promising nuclear fusion reactions in the interaction of intense laser pulses with solid targets (see Belyaev BC et al. Generation of fast charged particles and superstrong magnetic fields in the interaction of ultrashort intense laser pulses with solid targets // Uspekhi Fizicheskikh Nauk, t .178, No. 8, p. 823-843, 2008).

A known method of initiating a nuclear fusion reaction by generating neutrons in the constriction of a Z-pinch from low-density deuterated polyethylene (see Akunets A.A. et al. "Generation of neutrons in the constriction of a Z-pinch from low-density deuterated polyethylene." Plasma Physics 2010, t .36, No. 8, XXXVI International (Zvenigorod) Conference on Plasma Physics and Fusion, February 9–13, 2009), which can be taken as the first analogue.

The disadvantage of the method of initiating a nuclear fusion reaction in the article Akunets A.A. - the first analogue of the proposed method for initiating a nuclear fusion reaction - is the irrational choice of the target material, which does not allow to obtain α-particles ( ⁴ He) and protons p.

Another analogue of the claimed method is also known, which is technically close to the claimed invention.

This invention (RF patent for the invention No. 2449514, priority of the invention on August 24, 2010) can be selected as a prototype of the claimed invention with the name "Method for initiating a nuclear fusion reaction and a device for its implementation".

The method for initiating a nuclear fusion reaction in the prototype is based on the generation of ions from the ionized target material from its rear side under the influence of a high-contrast laser beam of relativistic intensity and ultrashort duration on the frontal surface of the target, with the acceleration of ions orthogonally to the rear surface of the first target when they move to the second target. In this case, deuterated polyethylene (CD₂)_n thickness l_oneat range l_one≈1 μm ÷ 10 μm. Under the influence of a high-contrast laser beam of relativistic intensity I in the range I≈10 on the frontal surface of the target^eighteen÷ 10^twenty W / cm² with energy E in the range E≈10 J ÷ 500 J and ultrashort duration t in the range t≈100 fs ÷ 1 ps with a contrast k in the range k≈10⁸÷ 10¹⁰ ensure the generation of deuterium ions from the back surface of the first target, and as a receiver of deuterium ions, a second target of the same material activated by accelerated deuterium ions of thickness l₂ in the range of l₂≈100 μm ÷ 1 mm, which is located at a distance L in the range L≈10 mm ÷ 50 mm from the first target, while the deuterium ions moving towards the second target are accelerated to an energy sufficient to overcome the Coulomb barrier between colliding ions and to ensure the implementation of a promising nuclear synthesis reaction D + D →³He + n + 3.27 MeV to obtain helium³He and neutrons n.

The disadvantage of the method of initiating a nuclear fusion reaction in the prototype is the irrational choice of the target material, which does not allow to obtain α-particles ( ⁴ He) and protons p.

The objective of the invention is the selection of target material to ensure a technical result - the initiation of promising nuclear fusion reactions to produce α-particles ( ⁴ He) and protons p.

In the method of initiating a nuclear fusion reaction using two targets, selecting deuterated polyethylene (CD ₂ ) _n as the first target material with a thickness l ₁ in the range l ₁ ≈ ₁ μm ÷ 10 μm, generating ions from the back of the ionized material of the first target under the influence on the frontal surface of this target of a high-contrast laser beam of relativistic intensity I in the range of 10 ¹⁸ ÷ 10 ²⁰ W / cm ² ultrashort duration t in the range of 100 fs ÷ 1 ps with a contrast k in the range of 10 ⁸ ÷ 10 ¹⁰ providing acceleration of ions of when they move to the second target for the action of accelerated deuterium ions on the surface layer of the second target, a titanium target with a thickness of ~ 500 μm is used as the second target, the front surface of which is preliminarily activated with ³ He helium ions to a depth in the range of 1 μm ~ 10 μm, In this case, the second target is placed in vacuum at a distance L in the range of 10 mm ÷ 50 mm from the first target and accelerate the deuterium ions moving to its surface to an energy sufficient to overcome the Coulomb barrier between colliding ions and deuterium and helium and ensuring the implementation of a promising reaction for the synthesis of D + ³ He → ⁴ He + p + 18.3 MeV to produce α-particles ( ⁴ He) with an energy of 3.67 MeV and protons p with an energy of 14.67 MeV.

Additionally, in the method of initiating a nuclear fusion reaction, the frontal surface of a second target selected from titanium is preliminarily activated by helium ³ He ions accelerated to an energy of ~ 1 MeV to a depth of ~ 1 ÷ 10 μm to form a layer of ³ He ions with a thickness of about 1-10 μm with a maximum concentration ³ He of the order of 1 × 10 ²³ cm ^-3 .

A device is known for implementing a method for initiating a nuclear fusion reaction by using ion acceleration in England patent No. 1138212, filed May 23, 1966, MKI H05h, H01j (H1D), in which an ion source and accelerator are proposed. This device, proposed in England patent No. 1138212, is technically close to the claimed device for implementing the method of initiating a nuclear fusion reaction and can be selected as the first analogue of the device for implementing the method for initiating a nuclear fusion reaction by ion acceleration.

The first analogue of the device for implementing the method in England patent 1138212 contains a target of ionizable material located in the path of the light beam of the laser. A ray of light in England patent No. 1138212 is concentrated by a special device to bombard the target surface with an energy sufficient to ionize the target material and produce a plasma. There are electrodes for extracting the desired ions from the plasma created by the laser beam incident on the target. An electrostatic accelerator is designed to form an electric field that accelerates ions.

The disadvantages of the first analogue of the device for implementing the method of initiating a nuclear fusion reaction by accelerating ions are its low efficiency for initiating promising nuclear fusion reactions, as well as the complexity and cumbersomeness of the involved equipment for creating and implementing the method.

There is another device for implementing a method for initiating promising reactions for the synthesis of nuclear particles by accelerating ions in the interaction of intense laser pulses with solid targets, which provides the effects of a device for implementing a method for initiating promising reactions for synthesis according to the invention (RF patent for the invention No. 2449514 with priority dated 08.24.2010 g) and can be selected as the second analogue and prototype of the claimed invention with the name "Method for initiating a nuclear reaction of synthe for and a device for its implementation. "

A device for implementing a method for initiating promising nuclear particles - the prototype contains an energy concentrator located in a vacuum chamber, a target and a receiver of accelerated ions, and outside the chamber there is a pulsed laser with parameters of relativistic intensity I of ultrashort duration t and high contrast k, oriented through the concentrator to the front surface of the first target which is made of solid polyethylene deuterated (CD _{2) n} thickness in the range of ₁ l ₁ l ≈1 mm ÷ 10 mm, and a distance l from the first Ishenim ranging L≈10 mm ÷ 50 mm set second target of the same material thickness in the range of l ₂ l ₂ ≈100 mm ÷ 1 mm, wherein the pulse laser has a relativistic intensity I I≈10 in the range ¹⁸ -10 ²⁰ W / cm ² , energy E in the range E≈10 J ÷ 500 J, ultrashort duration t in the range 100 fs ÷ 1 ps and contrast k in the range k≈10 ⁸ ÷ 10 ¹⁰ , and detectors with helium counters and / or neutron counters.

The disadvantage of the second analogue of the prototype of the ion acceleration method is its inefficiency for initiating promising nuclear fusion reactions to produce α particles ( ⁴ He) with an energy of 3.67 MeV and / or protons p with an energy of 14.67 MeV.

The task of the invention is to provide a technical result - the initiation of promising nuclear reactions for the synthesis of nuclear particles of deuterium D and helium-3 ³ He to produce α-particles ( ⁴ He) with an energy of 3.67 MeV and protons p with an energy of 14.67 MeV.

In a device for implementing a method for initiating promising nuclear reactions for the synthesis of these particles, containing an energy concentrator located in a vacuum chamber and two targets located at a distance L from each other in the range L≈10 mm ÷ 50 mm, as well as a pulsed laser located outside the chamber with parameters relativistic intensity I in the range 10 ¹⁸ ÷ 10 ²⁰ W / cm ² , energy E in the range 10 J ÷ 500 J, ultra-short duration t in the range 100 fs ÷ 1 ps and radiation contrast k in the range 10 ⁸ ÷ 10 ¹⁰ . The first target is made of solid state deuterated polyethylene (CD ₂ ) _{n of} thickness l ₁ in the range of 1 μm ÷ 10 μm, the second target is made of titanium with a thickness of ~ 500 μm, the front surface of which is activated by ³ He helium ions to a depth in the range of 1 μm ~ 10 μm and in the zone in front of the frontal surface there are detectors capable of detecting α-particles ( ⁴ He) with an energy of 3.67 MeV and / or protons p with an energy of 14.67 MeV to solve the technical problem of providing a technical result - initiating promising nuclear fusion reactions.

The method for initiating a nuclear fusion reaction and a device for its implementation are illustrated by a time chart of various types of background radiation arising from amplification of a relativistic ultrashort laser pulse, in FIG. 1 and the flowchart in FIG. 2 of a device for implementing a method for initiating a nuclear fusion reaction.

According to figure 1 on the timing diagram of various types of background radiation are presented:

1 - superluminescence (duration - hundreds of microseconds);

2 - residual pulses of the master oscillator (repetition interval ~ 10 ns);

3 - pulses arising from reflections from the surfaces of optical elements (10-100 ps);

4 - residual pulses of the master laser, which made a complete round-trip through the resonator of the regenerative amplifier (10-100 ps);

5 - prepulses resulting from distortion of the spectrum and incomplete compensation of the modulation phase of the amplified radiation (units of picoseconds).

In the flowchart of figure 2 devices for implementing the method of initiating a nuclear fusion reaction are shown:

- a pulsed laser 6, the output of which is focused on the hub;

- a laser beam 7 at the output of a pulsed laser directed through a porthole to a concentrator;

- porthole 8;

- a vacuum chamber 9 with targets mounted inside the chamber;

- frontal surface 10 of the first target;

- the first target of deuterated polyethylene (CD ₂ ) _n 11;

- the back surface 12 of the first target;

- plasma formation (PO) 13 on the back surface of the target;

- toroidal plasma current sheet (TPTS) 14 inside the software;

- the second target 15 of titanium inside the vacuum chamber;

- energy concentrator 16 inside the vacuum chamber;

- CR-39 track detectors for detecting α-particles ( ⁴ He) 17 with Al (aluminum) filters with a thickness of 10-50 microns;

- plasma current sheet (TPTS) 18 in approach to the second target of titanium;

- an activated layer of 19 ions of ³ He on the receiving surface of the second target of titanium;

- CR-39 track detectors for detecting p 20 protons with Al (aluminum) filters 0.5-1 mm thick.

When the device for implementing the method of ion acceleration is operating, a plasma formation (PO) 13 is formed on the back surface 12 of the target, and a toroidal plasma current sheet (TPTS) is formed inside the PO 13 with the deuterium D ions included in it (see paragraph 14 in FIG. 2 )

In this case, between the first and second targets, the deuterium D ions of item 14 are shown in the plasma current sheet (TPTS), which are shown as p. 18 at the stage of approaching the second target.

In the surface layer of the second target 15, as a result of the interaction of accelerated deuterium ions with 15 helium ions embedded in the surface layer of the second target, a promising nuclear reaction D + ³ He → ⁴ He + p + 18.3 MeV is initiated to produce α-particles ( ⁴ He) with energy 3.67 MeV and protons p with an energy of 14.67 MeV.

Moreover, the method for carrying out a promising nuclear fusion reaction in a device for its implementation is implemented as follows.

According to a block diagram of a device for carrying out a promising nuclear reaction in FIG. 2, a pulsed laser 6 is installed at the input of the vacuum chamber 9. The laser beam 7 at the laser output is guided through the porthole 8 and the energy concentrator 16 to the front surface 10 of the target 11 mounted on coordinate platform (not shown in the block diagram) in the vacuum chamber 9. After pumping the chamber, work is started to ensure a controlled effect on the front surface 10 of the target 11 of the laser beam 7 of the relativistic Intensity. In this case, a pulseless laser beam of a relativistic intensity laser is formed in the range of ~ 10 ¹⁸ W / cm ² -10 ²⁰ W / cm ^{2 of} ultra-short duration ~ 1 × 10 ^-12 s, which is focused with focus on the front surface of the target 10 and proceed with the adjustment of the pulsed laser 6 .

When operating a pulsed laser 6, the main pulse of relativistic intensity at its output is indicated in figure 1 with an inscription near the largest pulse. There are several reasons for the occurrence of background radiation during the operation of a pulsed laser, which manifests itself differently at different time intervals of the operation of a pulsed laser.

The most typical cases of background radiation are depicted in figure 1:

1 - superluminescence (duration - hundreds of microseconds);

2 - residual pulses of the master oscillator (repetition interval ~ 10 ns);

3 - pulses arising from reflections from the surfaces of optical elements (10 ps-100 ps);

4 - residual pulses of the master laser, which made a complete round-trip through the resonator of the regenerative amplifier (10 ps-100 ps);

5 - prepulses resulting from distortion of the spectrum and incomplete compensation of the modulation phase of the amplified radiation (units of picoseconds).

In the microsecond range, the main source of noise is superluminescence in the active medium of amplification stages. For typical solid state active media, such as neodymium glass or sapphire with titanium, the power of amplified spontaneous emission usually does not exceed several hundred watts. It has a high angular divergence and is quite effectively suppressed by spatial filters.

Another type of noise radiation is associated with the periodic nature of the generation of an ultrashort pulse and its subsequent amplification in a regenerative amplifier (RU). The intracavity radiation of solid-state lasers generating ultrashort pulses, as a rule, is a train of pulses following with an interval of ~ 10 ns. When a single pulse is allocated as a result of the finite transmission of an electro-optical shutter and other elements of optical selection, incomplete suppression of neighboring train pulses is possible. At the exit from the switchgear, similar residual pulses may arise with a repetition period that is a multiple of the time by which radiation passes through the amplifier cavity.

In addition to pulses following a nanosecond time interval, pulses can occur with a repetition interval of units and tens of picoseconds, in particular, as a result of reflection from the surfaces of optical elements. There is another possibility of the appearance of background radiation in this interval - as a result of amplification of incompletely suppressed pulses of a train of a master oscillator, ahead of the main pulse. When the Q factor of Q is turned on at the moment of arrival of a high-intensity pulse, the preceding residual pulse of the train manages to complete a complete round-trip of the RU resonator and starts to amplify along with the main pulse. The time interval between the main and residual pulses of this type is determined by the mismatch of the lengths of the resonators of the generator and amplifier. Since the resonators of the switchgear and the master laser have similar lengths, the characteristic repetition times of such pulses are in the range of tens of picoseconds.

A decrease in the contrast of radiation can also occur as a result of distortion of the spectrum and self-modulation of the radiation during amplification. To suppress self-action, a linearly chirped pulse amplification mode is usually used, obtained from the initial spectrally-limited pulse by forced quadratic modulation of the radiation phase using a stretcher that provides linear positive dispersion. However, even in this case, when a sufficiently large power is reached, the pulse can acquire an additional chirp in the amplification process. If the acquired chirp is nonlinear in nature, it is not possible to completely compensate for it with a compressor on diffraction gratings providing a negative linear dispersion of the group velocity. Spectrum modulation and incomplete compensation of a nonlinear chirp can lead to the appearance of a precursor pulse ahead of the main pulse by times comparable to the duration of the latter.

In order to increase contrast and minimize the effect of noise radiation, it is necessary to provide reliable control of the temporal and energy characteristics of radiation in a large dynamic range. Measurements of background radiation parameters in the micro- and nanosecond time ranges are carried out by conventional laser photometry (using high-speed photodetectors and high-speed oscilloscopes). To control the shape of an ultrashort pulse at intervals comparable to its duration, sufficiently effective methods have been developed using nonlinear optical processes of the second and third orders based on measuring dynamic spectrograms of the autocorrelation function of radiation. Such methods make it possible to fairly accurately reconstruct the temporal shape of the investigated pico- or femtosecond pulse.

The greatest difficulty is the measurement of the characteristics of background radiation pulses having an intermediate delay of tens or hundreds of picoseconds. For direct registration of such speed pulses and the dynamic range of existing electronic devices, as a rule, it is not enough. Nonlinear optical measurement methods allow, in principle, solving the indicated problem, but are too complicated for the operational control of radiation parameters directly during the experiment, in particular for measurements in the time interval of ~ 100 ps per laser flash (which is especially important for systems with a low frequency repetition). In more detail, the development and experimental implementation of a fairly simple and effective diagnostic method for monitoring the output parameters of high-power picosecond laser complexes in the subnanosecond time range is given in the work of the inventors B.C. Belyaev, A.P. Matafonova et al. “Measurement of ultrashort duration radiation parameters by the method of spectral interferometry of chirped pulses” // Quantum Electronics, 2000, v.30, No. 3, p.229. The method based on the use of spectral interferometry of chirped pulses uses the fact that in picosecond and femtosecond laser systems, to reduce the influence of self-action, amplification of chirped pulses obtained from a spectrally-limited initial pulse by forcing it to elongate to ~ 0.5 ns in a dispersion stretcher is used . Measurement of the spectral composition of the radiation with interferometric accuracy directly at the output of the amplifier stages provides information on the contrast and time delay of the background pulses, which can be expected after phase modulation is compensated by passing the time compressor.

On the implementation of future nuclear fusion reaction (see FIG. 2) D + He → ^{3 4} He + p + 18.3 MeV collide with the accelerated deuterium ions D (cm. Claim 18) and contained in a second target 15 ions ³ He (cm 19) to obtain the energy of relativistic laser radiation with an intensity (~ 10 ¹⁸ W / cm ² -10 ²⁰ W / cm ² ) of ultrashort duration t in the range of ~ 1 × 10 ^-12 s to produce α-particles ( ⁴ He) with an energy of 3.67 MeV and protons p with an energy of 14.67 MeV are judged by the readings of the detectors installed in the zone between the first and second targets: detector 17 based on track detectors of the CR-39 type Al filters with a thickness of 10 ÷ 50 microns for registration α-particles ^(4He) with an energy of 3.67 MeV and 20 39 CR-type detector with filters thick Al 0.5 ÷ 1 mm for registration p protons with an energy of 14.67 MeV (see FIG. 2, track detectors CR-39 for detecting p 20 protons with Al (aluminum) filters 0.5-1 mm thick and track detectors CR-39 for detecting α particles 17 with Al filters 10-50 μm thick )

Claims (3)

1. A method for initiating a nuclear fusion reaction, which consists in generating deuterium ions from the back side of the ionized material of the first target from solid-state deuterated polyethylene (CD ₂ ) _{n of} thickness l ₁ in the range of 1 μm to 10 μm under the influence of a high-contrast laser beam of relativistic intensity on its front surface I in the range 10 ¹⁸ ÷ 10 ²⁰ W / cm ² , ultrashort duration t in the range 100 fs ÷ 1 ps, with energy E in the range 10 J ÷ 500 J and contrast k in the range 10 ⁸ ÷ 10 ¹⁰ , acceleration of deuterium ions in vacuum when they move and to the second target to an energy sufficient to overcome the Coulomb barrier between colliding ions when exposed to accelerated deuterium ions on the surface layer of the second target and to ensure the implementation of a promising nuclear fusion reaction, characterized in that titanium with a thickness of 500 μm is chosen as the material of the second target front surface preactivated ^helium-3 He ions to a depth of 1 mm within the range 1 ÷ 10 microns, thus promising a nuclear fusion reaction D + He → ^{3 4} He + p + 18.3 MeV provide collisional it deuterium and helium ions to obtain α-particles ^(4He) with an energy of 3.67 MeV and p protons with an energy of 14.67 MeV, measuring the energy of said particles. 2. The method for initiating a nuclear fusion reaction according to claim 1, characterized in that the helium ions, which activate the frontal surface of the second target, are accelerated to an energy of ~ 1 MeV, providing their maximum concentration of the order of 1 × 10 ²³ cm ^-3 . 3. A device for implementing a method for initiating a nuclear fusion reaction, comprising an energy concentrator located in a vacuum chamber, a first target made of solid state deuterated polyethylene (CD ₂ ) _n with a thickness l ₁ in the range 1 ÷ 10 μm, a second target with activated helium ions ³ He a frontal surface located at a distance L in the range L≈10 mm ÷ 50 mm from the first target, a pulsed laser installed outside the chamber with a relativistic intensity I on the target surface in the range 10 ¹⁸ ÷ 10 ²⁰ W / cm ² , duration t in the range of 100 fs ÷ 1 ps, energy E in the range of 10 J ÷ 500 J and contrast k in the range of 10 ⁸ ÷ 10 ¹⁰ , as well as detectors for detecting α particles and protons installed in the registration zone of these particles, characterized in that the second target is made of titanium with a thickness of ~ 500 μm, and its frontal surface is activated by helium ions ³ He to a depth of 1 in the range of 1 μm ~ 10 μm, while the detectors for detecting α particles ( ⁴ He) have aluminum filters with a thickness of ~ 10- 50 μm, and the proton p detectors have aluminum filters with a thickness of 0.5-1 mm.

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