Influence of intense coherent electromagnetic radiation on several types of radioactive decay

Many configurations have been proposed to use highpower laser radiation for acceleration of the charged particles [1]. Required power density for such experiments varied from 10 W/cm up to 10 W/cm. For example, X-rays of MeV energy have been produced by accelerated plasma electrons when laser beam with intensity of 5*10 W/cm was focused on tantalum sheet. Energy of these X-rays was high enough to initiate a set of nuclear reactions, which have been registered experimentally [2]. We investigate an influence of coherent electromagnetic radiation on different types of radioactive decay. Our experiments indicate that some nuclear reactions can be initiated even at laser beam intensity about 1*10 W/cm. The key feature is the presence of metallic (chemically inactive Au as a rule) nanoparticles. In plasmon resonance regime the wave field near nanoparticles can be concentrated up to the necessary level. Layout of the typical experiment is shown on fig. 1.


Optical laser radiation
Many configurations have been proposed to use highpower laser radiation for acceleration of the charged particles [1].Required power density for such experiments varied from 10 18 W/cm 2 up to 10 20 W/cm 2 .For example, X-rays of MeV energy have been produced by accelerated plasma electrons when laser beam with intensity of 5*10 18 W/cm 2 was focused on tantalum sheet.Energy of these X-rays was high enough to initiate a set of nuclear reactions, which have been registered experimentally [2].
We investigate an influence of coherent electromagnetic radiation on different types of radioactive decay.Our experiments indicate that some nuclear reactions can be initiated even at laser beam intensity about 1*10 12 W/cm 2 .The key feature is the presence of metallic (chemically inactive Au as a rule) nanoparticles.In plasmon resonance regime the wave field near nanoparticles can be concentrated up to the necessary level.Layout of the typical experiment is shown on fig. 1.We have observed partial Hg transmutation into Au inside heavy water D 2 O [3].Laser irradiation in presence of Au nanoparticles initiates the decay of 232 Th [4].Very exciting result was a significant (up to 50%) decrease of gamma-activity of 238 U and 235 U series after laser irradiation in presence of beryllium nanoparticles [5].

Microwave radiation
There are some similar experiments in microwave and radiofrequency regions.3 GHz radiation caused increasing the 51 Cr activity at 1% [6].0.07% of the 137 Cs activity growth was registered during irradiation of the sample by 4.1 MHz and 1.55 MHz radiation with a maximum power of 50 kW [7].Our experiment using 30 GHz FEM shows about 1.5% variation of the 152 Eu activity [8].In all these experiments there were no special measures to increase the power density.

Field concentrators in microwave experiment
We assume that all changes in the rate of the radioactive decay were caused by the charged particles accelerated in the plasma, produced in focal region in presence of field concentrators (metal nanoparticles).We have in mind that the power density about 1*10 18 W/cm 2 is enough to produce some types of nuclear reaction without special field concentrators.Estimation of the maximal energy of the proton inside the electromagnetic wave with wavelength λ and intensity I can be done by [9]: where E max is in MeV, λ in microns, I in W/cm 2 .Indeed, the wave with length of 1 micron and intensity of 1*10 18 W/cm 2 can accelerate protons up to 3.6 MeV, which is more than the threshold of many nuclear reactions.In our experiments with power densities of 1*10 12 W/cm 2 the presence of field concentrators (nanoparticles) can increase the field intensity up to 10 5 and (nanoparticles dimers) to 10 6 times.Let us estimate the necessary rate of field concentration in microwave region.For wavelength of 1 cm (10 4 microns) the desired proton energy of 3.6 MeV requires the field intensity of 1*1010 W/cm 2 .The diffraction limits the area of focal spot by 1 cm 2 , so we need or 10 GW radiation source, or 10 MW radiation source and 1*10 3 times field concentrators.For microwave region the role of the field concentrators can play metal sawdust.The layout of proposed experiment is shown on fig. 4.

Fig. 1 .
Fig. 1.Layout of the experiment on irradiation of water solution of the radioactive salt by the medium-power laser in presence of the metallic nanoparticles We use several types of optical and near-infrared lasers -Cu vapor, femtosecond Ti:sapphire, 90-ps Nd:YAG, 350-ps Nd:YAG, 10-ns Nd:YAG, Their pulse energy varied from 0.1mJ up to 40 mJ, repetition rate varied from 10 Hz up to 20 kHz.Power density in focal region without influence of the nanoparticles varied from 1*10 11 W/cm 2 up to 1*10 12 W/cm 2 .Nanoparticles being used in our experiments are produced by laser ablation by metal target in the water.We have observed partial Hg transmutation into Au inside heavy water D 2 O[3].Laser irradiation in presence of Au nanoparticles initiates the decay of 232 Th[4].Very exciting result was a significant (up to 50%) decrease of

Fig. 2 .
Fig. 2. 234 Th activity during several sessions of laser irradiation of UO 2 Cl 2 water solution in presence of Au nanoparticles as the laser wave concentrators. 134Cs is a reference sample Figure 2 presents the results of long-time measurement of the 234 Th activity during several sessions of laser irradiation.Each session decrease the activity.Effect of each next irradiation is less than the previous one due to fragmentation of nanoparticles and their escape from the plasmon resonance.

Fig. 4 .
Fig. 4. Proposed layout of the experiment on the RF irradiation of the radioactive sample.Metal sawdust should be the RF field concentrators