Deuterated Polyethylene Research Articles

The influence of target film material and coating on neutron yield and sputtering yield

The long-life, high yield deuterium-deuterium (D-D) neutron tube has become one of the research hotspots. Here, deuterated polyethylene target, heavy water target and titanium target were investigated by Stopping and Range of Ions in Matter (SRIM). The calculation showed that the deuterated polyethylene target, which was a potential target material, had the highest yield at an incident energy of 120 keV. Further, considering the unfavorable factors such as impurity ions and high temperature, the coating was used to protect the target material. Diamond, boron carbide, boron nitride, silicon carbide, and aluminum carbide were selected. The simulation results showed that the diamond composite deuterated polyethylene film had the best sputtering resistance, and the aluminum nitride composite heavy water target film had the lowest sputtering yield. The two coating materials shield the target, reduced the energy loss of incident ions, and provided a new method for the research of high yield and long life neutron tube.

Precision, Tunable Deuterated Polyethylene via Polyhomologation

The ability to introduce isotopic labeling in a controlled fashion into polymers has long been an area of keen interest, as it allows for analysis by methods such as small-angle neutron scattering. In this work, polyhomologation (also known as “C1 polymerization”) of a deuterated ylide was performed, yielding linear polyethylene of high deuterium content. Copolymerization with the protonated analog allowed for the preparation of statistical copolymers, in which linear polyethylene with a uniform and tunable amount of deuterium is obtained. The amount of deuterium present, as well as its uniform distribution, is supported by vibrational spectroscopy, size-exclusion chromatography with infrared detection, and 2H nuclear magnetic resonance spectroscopy. This technique was extended to prepare a precision triblock copolymer in which the chain-ends are selectively deuterated. All polymers reported are of narrow dispersity, and will find use in myriad measurements sensitive to deuterium labeling, most notably sm...

Implosion dynamics of condensed Z-pinch at the Angara-5-1 facility

The implosion dynamics of a condensed Z-pinch at load currents of up to 3.5 MA and a current rise time of 100 ns was studied experimentally at the Angara-5-1 facility. To increase the energy density, 1- to 3-mm-diameter cylinders made of a deuterated polyethylene−agar-agar mixture or microporous deuterated polyethylene with a mass density of 0.03–0.5 g/cm3 were installed in the central region of the loads. The plasma spatiotemporal characteristics were studied using the diagnostic complex of the Angara-5-1 facility, including electron-optical streak and frame imaging, time-integrated X-ray imaging, soft X-ray (SXR) measurements, and vacuum UV spectroscopy. Most information on the plasma dynamics was obtained using a ten-frame X-ray camera (Е > 100 eV) with an exposure of 4 ns. SXR pulses were recorded using photoemissive vacuum X-ray detectors. The energy characteristics of neutron emission were measured using the time-offlight method with the help of scintillation detectors arranged along and across the pinch axis. The neutron yield was measured by activation detectors. The experimental results indicate that the plasma dynamics depends weakly on the load density. As a rule, two stages of plasma implosion were observed. The formation of hot plasma spots in the initial stage of plasma expansion from the pinch axis was accompanied by short pulses of SXR and neutron emission. The neutron yield reached (0.4–3) × 1010 neutrons/shot and was almost independent of the load density due to specific features of Z-pinch dynamics.

Ion acceleration and D-D nuclear fusion in laser-generated plasma from advanced deuterated polyethylene.

Deuterated polyethylene targets have been irradiated by means of a 1016 W/cm2 laser using 600 J pulse energy, 1315 nm wavelength, 300 ps pulse duration and 70 micron spot diameter. The plasma parameters were measured using on-line diagnostics based on ion collectors, SiC detectors and plastic scintillators, all employed in time-of-flight configuration. In addition, a Thomson parabola spectrometer, an X-ray streak camera, and calibrated neutron dosimeter bubble detectors were employed. Characteristic protons and neutrons at maximum energies of 3.0 MeV and 2.45 MeV, respectively, were detected, confirming that energy spectra of reaction products coming from deuterium-deuterium nuclear fusion occur. In thick advanced targets a fusion rate of the order of 2 × 108 fusions per laser shot was calculated.

Observation of repetitive bursts in emission of fast ions and neutrons in sub-nanosecond laser-solid experiments

AbstractA massive deuterated polyethylene target was exposed to laser intensities of about 3 × 1016 W/cm2 employing the 3-TW Prague Asterix Laser System (PALS). We achieved a yield of 2 × 108 neutrons per laser shot. Average time-of-flight signals of scintillation detectors operated in current mode reveal broad energy spectra of fusion neutrons with dominating energy of about 2.45 MeV. The energy dependence of the neutron yield shows a consistency in results of nanosecond, picosecond and sub-picosecond experiments. Here we also show that ions emitted in the backward direction from the front target surface have a multi-peak energy spectrum, which is caused by burst emission mechanisms.

Interfacial structure of all-polyethylene laminate using scanning thermal microscope and nano-Raman spectroscope

The interfacial structure of all-polyethylene laminate (linear low density polyethylene (LLDPE)/deuterated polyethylene (D-PE)) was investigated using different microprobe methods, scanning thermal microscopy (SThM), and confocal laser nano-Raman spectroscopy. By scanning the thermal probe under isothermal conditions over a cross section of the laminate film, a high-contrast image of apparent thermal conductivity at the interfacial region was obtained even for the flat height region observed using an atomic force micrograph. The apparent thermal conductivity and the Raman intensity gradually change across the tapered interfacial region between the two PEs. The interfacial thickness was estimated to be in the micrometer-order depending on the thermal treatment of the laminate film. Additionally, the peel strength of the LLDPE/D-PE laminate increased as the interfacial thickness increased. This suggests that both the LLDPE and D-PE molecular chains were entangled with each other, and/or both crystalline lamellae were in an interlocking state during thermal treatment.

The production of a 2–20 MeV collimated monoenergetic neutron beam of known flux using the associated particle technique

An associated particle system employing the 2H(d, 3He)n reaction has been developed to produce a neutron beam with accurately known properties in the 2–20 MeV range. In these experiments a deuterated polyethylene target is bombarded with 4–26 MeV deuterons from the ANU cyclograaff facility. The 3He ions emitted within a small solid angle are detected with a solid state detector telescope using particle identification. The neutron beam associated with these detected ions has typically a fwhm energy width of 5–10% and a corresponding spatial width of 3–4°. Counting the 3He ions determines the neutron flux absolutely. Procedures have been developed at the higher incident deuteron energies to exclude counting 3He events from the 12C(d, 3He) 11B reaction where the recoils from the 2H(d, 3He)n reaction are of similar energy. The neutron flux obtained within the experimental beam is typically 3 neutrons/nA·s from a 3 mg/cm 2 thick deuterated polyethylene target depending on the kinematic scheme chosen. The facility has been used to obtain spectra and measure cross sections for the 6Li(n, α) 3H reaction using a 6LiI(Eu) scintillator as the 6Li target.

Effect of isotopic composition on free‐radical reactions in polyolefins

AbstractOn substitution of hydrogen by deuterium the radiation yield of free radicals in polyolefins decreases ca. 2‐fold. Under ultraviolet illumination (γ < 300 nm) in deuterated polyethylene (DPE), allyl radicals are converted into alkyl radicals (hfs constants a = 3.2 Oe, a = 4.4 Oe); in deuterated polypropylene (DPP), allyl and peroxide radicals are converted into alkyl radicals (a = 3.7 Oe). At 77°K under ultraviolet light in γ‐irradiated polyethylene (PE) and DPE, triene, tetraene, dienyl, trienyl, and tetraenyl radicals are formed. Deuterium substitution has no effect on absorption spectra of polyenyl radicals and polyenes. In polyolefins the quantum yields of photochemical reactions of allyl and peroxide radicals are 0.1–1.0. Photochemical reactions of peroxide radicals result in a radical concentration increase of ca. 3‐fold. In reactions of peroxide radicals in the dark, a kinetic isotope effect has been observed. Activation energies of substitution reactions of peroxide radicals are in PE, 9.3 ± 0.3 kcal/mole; in DPE, 10.2 ± 0.3 kcal/mole; in PP, 12.7 ± 0.4 kcal/mole; in DPP, 14 ± 0.5 kcal/mole. Possible mechanisms of the effect of polyolefin isotope composition on radical formation by high energy irradiation as well as on photochemical and dark reactions of free radicals are discussed. The effect of the energy released from phototransformations and radiationless deactivation of macroradicals on the migration of free valence is also considered.

Free radicals in irradiated, deuterated polyethylene and polypropylene

At 77°K G ( R) in deuterated polyethylene and polypropylene is only half that in the undeuterated polymers. In deuterated polyethylene ∼CD 2CDCD 2∼ alkyl radicals are produced by γ-irradiation at 77°K and at 77–300°K the isotopic composition of the polymer has no appreciable effect on radical recombination. It has been found that in the deuterated polymers allyl radicals are converted to alkyl radicals under the influence of ultraviolet light. When deuterated polypropylene is irradiated with ultraviolet light peroxide radicals are converted to alkyl radicals and the total concentration of radicals is increased threefold.

Preparation of Thin Film Deuterated Polyethylene Targets

Preparation of Thin Film Deuterated Polyethylene Targets