High field nanoplasmonics for nuclear fusion

Eur. Phys. J. Spec. Top. https://doi.org/10.1140/epjs/s11734-025-01522-1 THE EUROPEAN PHYSICAL JOURNAL SPECIAL TOPICS Regular Article High field nanoplasmonics for nuclear fusion Norbert Krooa Wigner Research Center for Physics, NAPLIFE Programme, Konkoly Thege Miklós str 29-33, 1121 Budapest, Hungary Received 5 December 2024 / Accepted 7 February 2025 © The Author(s) 2025 Abstract Surface plasmon polaritons are the light of the nanoworld, with a broad spectrum of special properties. These properties open the field for a high number of applications, both in the fields of low and high intensities. In polymer samples, localized surface plasmon polaritons (LSPPs) have been resonantly excited by ultrashort (n. 10 fs), high intensity (up to n. 1017 W/cm2 ) pulses of a Ti:Sa laser on gold nanoparticles, implanted into the transparent polymer, and this the laser shots created craters. The volume of these craters is presented as the function of the exciting laser intensity for the samples with and without resonant gold nanoparticles, and the creation of deuterium in the nanoparticle-seeded sample was studied with Raman and laser-induced breakdown spectroscopy (LIBS). The preliminary data indicate significant energy production and nuclear transmutation (hydrogen to deuterium), clearly proving the decisive role of the unique properties of the LSPPs. Preliminary data of some nuclear (CR-39) methods are also described. Thompson parabola energy analysis of particles after laser shots indicates proton–boron fusion reaction. 1 Introduction It has been found by us already in the late 1970s that tunneling electrons can be emitted from gold surfaces by nanosecond laser pulses, with intensities in the 1010 W/cm2 range in contradiction with the expected 1014 W/cm2 range. We have found that the field enhancement of surface plasmon polaritons is responsible for this significant discrepancy [1]. This enhancement is, e.g., due to laser pulses, exciting optical near fields either on the surface of a negative refractive index material, e.g., metal (surface plasmon), or on small, typically nanosized particles (localized surface plasmons), collecting the laser pulse energy in small volumes. The diffraction limit does not apply for these excitations and, therefore, penetrate into miniscule volumes. This means that these plasmons can be considered as the light of the nanoworld. In the visible range of electromagnetic radiation, gold and silver are the best materials for plasmonic excitations. The number of plasmonic applications is increasing due to their positive properties in a broad field of technologies, from informatics, sensorics, metrology, medicine, etc. Perhaps one of the most promising field of applications is the exploitation of intense laser field interaction with matter. The work is an attempt to explore plasmonic phenomena in nuclear fusion processes [2, 3]. Why have we chosen (localized) surface plasmons to boost the nuclear fusion process? Because (1) they generate high EM fields by collecting EM energy of laser light in nanosized volumes (hot spots), resulting in screening of the repulsive forces, e.g., of proton–proton pairs [2, 3]; (2) they generate ponderomotive acceleration of particles (e.g., protons) in the near field at the surface of the nanoparticles [4]; (3) the motion of electrons in these localized plasmons is correlated; therefore, their momentum is added, resulting in a large momentum, which can be transferred to nearby protons, leading also to acceleration [5]. These effects in high laser fields with resonant gold nanoparticles in a transparent material with high hydrogen content (polymer) have been modeled. It has been found that multi-MeV protons are generated, and the protons move together with the plasmonic electrons in a correlated way [6]. What are the basic ideas of the NAPLIFE team’s preliminary experiments? Many laser fusion programs (e.g., NIF) copy the basic features of the fusion process in the Sun, by replacing the gravitational force with the reaction force of surface evaporation to squeeze the fusion material (typically DT) to reach high density and temperature. This is a “slow” process (in the few ten nanoseconds range), resulting in instabilities. The aim of the NAPLIFE a e-mail: (corresponding author) 0123456789().: V,-vol 123 Eur. Phys. J. Spec. Top. project is to bring the laser energy into the fusion material with speed of light, and collect it simultaneously into miniscule volumes by resonant plasmonic nanoparticles (e.g., gold) and explore the above-mentioned positive effects of the localized surface plasmons [7]. 2 Experimental results The first problem to be solved has been the influence of the well-known plasma mirror effect. The plasma mirror reflects the light and, therefore, it does not reach the nanoparticles within the sample. It is known, however, that at high intensities the reflection drops down [8]. The NAPLIFE experiments proved this result. Approaching the 1017 W/cm2 laser intensity of the ∼ 40 fs pulses of a Ti:Sa laser, the reflection drops down to a very small level. It has also been observed that the difference between the gold nanorod seeded and the “clean” polymer sample in negligible. It has also been found that the light absorbed in the ∼ 60 μ thick samples is above 98% for both types. Therefore, laser light at higher intensities penetrates into the used polymer (UDMA) samples, excite localized plasmons on the resonant Au nanorods and the above-mentioned effects are expected to be observed by measurable changes. The intense laser shots lead to crater formation in the sample and their volume is proportional with the energy of the laser pulse [9]. In Fig. 1, it is shown for 25/27.5 mJ laser pulse energy, that the white light interferometry [10] images of the clean and nanorod seeded samples are significantly different. The clean sample crater is smooth, while the seeded one is much bigger and structured. When the laser pulse energy is kept constant, but the intensity changes, the clean sample volume does not change, while the seeded one does. It is up to about seven times bigger (Fig. 1). This indicates a significant excess energy, which can originate only from nuclear processes. One potential source could be H–D fusion. The first test of this idea was the study of deuterium production by Raman scattering on the surface of the craters produced by the laser shots. It has been found [11] that in the seeded samples C–H vibration lines could be found, while in the clean sample cases, they were absent (Fig. 2). The deuterium content is increasing both with increasing energy and nanoparticle concentration. The second test was the direct observation of D atoms in the plume, emitted backwards from the craters after the laser shot [12]. Laser-induced breakdown spectroscopy (LIBS) method equipped with a high-resolution spectrometer has been used to detect the Dα line in the plume, being 0.17 nm shorter than the Hα line (656.27 nm). This has been (...truncated)