Joseph Magill

Observation of a highly directional γ-ray beam from ultrashort, ultraintense laser pulse interactions with solids

Novel measurements of electromagnetic radiation above 10 MeV are presented for ultra intense laser pulse interactions with solids. A bright, highly directional source of γ rays was observed directly behind the target. The γ rays were produced by bremsstrahlung radiation from energetic electrons generated during the interaction. They were measured using the photoneutron reaction [63Cu(γ,n)62Cu] in copper. The resulting activity was measured by coincidence counting the positron annihilation γ rays which were produced from the decay of 62Cu. New measurements of the bremsstrahlung radiation at 1019 W cm−2 are also presented.

Laser-driven photo-transmutation of 129I - a long-lived nuclear waste product

Intense laser–plasma interactions produce high brightness beams of gamma rays, neutrons and ions and have the potential to deliver accelerating gradients more than 1000 times higher than conventional accelerator technology, and on a tabletop scale. This paper demonstrates one of the exciting applications of this technology, namely for transmutation studies of long-lived radioactive waste. We report the laser-driven photo-transmutation of long-lived 129 I with a half-life of 15.7 million years to 128 I with a half-life of 25 min. In addition, an integrated cross-section of 97±40 mbarns for the reaction 129 I(γ ,n) 128 I is determined from the measured ratio of the (γ ,n) induced 128 I and 126 I activities. The potential for affordable, easy to shield, tabletop laser technology for nuclear transmutation studies is highlighted.

Fission of actinides with tabletop lasers

We report the first laser induced fission of actinide nuclei with high intensity tabletop lasers. The results are discussed in the context of laser plasma diagnostics and nuclear waste handling.

Bremsstrahlung production with high-intensity laser matter interactions and applications

In the last decade an evolution of experimental relativistic laser-plasma physics has led to highly sophisticated lasers, which are now able to generate ultra short pulses and can be focused to intensities in excess of 1021 W cm−2, with more than 500 J on target. In the intense electric field of the laser focus, plasma with temperatures greater than 10 billion degrees can be generated. The laser interactions with solid or gas targets can generate collimated beams of highly energetic electrons and ions. Experiments utilizing high-intensity laser systems turn out to be an interesting and versatile source for radiation, high-energy particles and nuclear reactions, without recourse to large-scale facilities such as nuclear reactors or particle accelerators. The possibility of accelerating electrons to energies over 200 MeV in such early experiments led to the utilization of high-energy bremsstrahlung radiation in order to investigate laser-induced gamma reactions. Many experiments of this type have been reported in several laboratories worldwide. However, to our knowledge, no dedicated investigations have been reported with respect to the characterization of the generated bremsstrahlung in such experiments. As it is not experimentally feasible to measure directly a bremsstrahlung spectrum, we report in the present paper on a dedicated series of calculations on the generated bremsstrahlung distributions from two experimental electron spectra measured using the giant pulse VULCAN laser and a gas jet target. Potential applications are also investigated.

Effect of target heating on ion-induced reactions in high-intensity laser–plasma interactions

Measurements of ion-induced nuclear reactions have been used to diagnose ion acceleration from the interaction of high-intensity (>1019 W cm−2) laser light with solid targets. Nuclear activation of catcher materials surrounding the interaction region has been studied using a high-resolution germanium detector. It was found that, when a 100 μm thick Al target foil was preheated, the proton flux produced from the laser–foil interaction was considerably reduced. Observed heavy-ion-induced reactions are used with calculated reaction cross sections to quantify ion acceleration.

Laser-generated nanosecond pulsed neutron sources: scaling from VULCAN to table-top

Neutron production capabilities of table-top laser accelerated protons based on data from a high-energy single-shot large laser are addressed. Recently, McKenna et al (2005 Phys. Rev. Lett. 94 084801) have analysed the energy spectrum for a beam of protons accelerated on the VULCAN laser. In this paper, we present a new analysis of the same experiment which demonstrates, for the first time, production levels in excess of 109 neutrons per laser shot within a nanosecond pulse through (p,xn) reactions on lead targets. We have used this natPb(p,xn) conversion analysis approach to make predictions on the neutron production capabilities of table-top laser systems. Neutron spectra for current state-of-the-art table-top lasers have been calculated, and we have estimated that current systems are capable of producing 106 neutrons per second in nanosecond pulses. Furthermore, we have found that nanosecond neutron pulses at a rate of 5 ? 109 neutrons per second are possible with the next generation of table-top lasers currently under construction.

Non-Proliferation Issues for Generation IV Power Systems

In the event of a revival of interest in nuclear energy, so-called Generation IV1 power systems will come into operation between 2030–2050. These systems should be highly economical, have enhanced safety features, give rise to a minimum of waste, and be proliferation resistant.

Application of Nucleonica's Gamma Spectrum Generator and easyMonteCarlo simulation tools on nuclear security issues

Modeling of gamma spectra is required in various fields. The growth of usage of spectrometric border monitoring methods to combat illicit trafficking of nuclear and other radioactive materials enhances the need for such techniques. With the development of the Gamma Spectrum Generator within the Nucleonica web-portal (www.nucleonica.net) a new ansatz is made, which allows authorized experts to perform spectrum modeling on a PC, wherever web access is available. The spectrum modeling toolkit (Gamma Spectrum Generator and easyMonteCarlo) must address various aspects, such as different detectors and their direct environment, various radioactive sources, their geometries and materials, distances and absorbers. After showing the accuracy of the modeling tools, more sophisticated scenarios can be dealt with. As a first example the nuclear security relevant masking issue is investigated experimentally and in extensive simulations using the described modeling tools.

The NUCLEONICA Nuclear Science Portal

NUCLEONICA (www.nucleonica.net) is a new nuclear science web portal which provides a customisable, integrated environment and collaboration platform using the latest internet “Web 2.0” technology. NUCLEONICA is aimed at professionals, academics and students working in nuclear power, health physics and radiation protection, nuclear and radio‐chemistry, and astrophysics. A unique feature of the portal is the wide range of user friendly web‐based nuclear science applications. The portal is also ideal for education and training purposes and as a knowledge management platform to preserve nuclear knowledge built up over many decades.

Electron and Proton Acceleration from Solid Targets by High-intensity Table-top Lasers

Electron and proton beams were investigated using a compact laser with intensities up to 2times1019 W/cm2 irradiating thin targets. For the direction of the electron beam theory and experiment disagree