An ultra-broadband beam splitter arrangement, with a spectral amplitude response that is over seven orders-of-magnitude more uniform than broadband, multi-layer dielectric beam splitters, can be created by the combination of multiple Fresnel events on an uncoated, optical flat when used at a specific angle-of-incidence. This beam splitter arrangement produces three, spectral copies of the original, two of which have identical spectral phase. In this manuscript we derive the precise angle at which this maximally flat spectral amplitude response occurs for any material and present this angle's material and polarization dependence.

On December 5, 2022, an indirect drive fusion implosion on the National Ignition Facility (NIF) achieved a target gain G_{target} of 1.5. This is the first laboratory demonstration of exceeding "scientific breakeven" (or G_{target}>1) where 2.05 MJ of 351 nm laser light produced 3.1 MJ of total fusion yield, a result which significantly exceeds the Lawson criterion for fusion ignition as reported in a previous NIF implosion [H. Abu-Shawareb et al. (Indirect Drive ICF Collaboration), Phys. Rev. Lett. 129, 075001 (2022)PRLTAO0031-900710.1103/PhysRevLett.129.075001]. This achievement is the culmination of more than five decades of research and gives proof that laboratory fusion, based on fundamental physics principles, is possible. This Letter reports on the target, laser, design, and experimental advancements that led to this result.

A numerical analysis of spatially chirped beams produced by single-pass grating pairs is presented. It is shown that focused pulse structures can deviate significantly relative to standard linear spatial chirp approximations depending upon the pulse bandwidth, the angle of incidence, and groove density of the gratings used.

A novel method of measuring an electron beam's energy spectrum and divergence using Compton-scattered x rays created by colliding a laser with an electron beam has been developed and tested using the compact laser-Compton x-ray source at LLNL. The method only requires an x-ray imaging device and a filter material whose K-edge energy matches that of the Compton-scattered x rays. K-edge filtering of energy-angle correlated Compton x rays causes large variations in intensity over the viewing angle. These intensity variations contain information about the electron beam's properties. By using simulation tools and adjusting the beam parameters to match the shape of the acquired image, the electron beam can be characterized. As a demonstration of this technique, a 75-mu m Sn foil was used to filter 30-keV Compton x rays created from Compton scattering of a 532-mu m laser beam by a 30-MeVelectron beam. The measured parameters were mean energy E = 28.51 +/- 0.06 MeV, energy spread sigma(E) < 0.3%, and beam divergence sigma(theta) = 1.8 +/- 0.1 mrad.

Electro-optic frequency comb compressed pulse durations scale by ~1/ n for modulators optimally seeded with n optical carrier frequencies. Uniform, ultrafast pulses with multi-GHz repetition rates are obtainable if the resulting adjacent frequency combs are phase locked, frequency locked, and compressed with a liquid crystal spatial light modulator.

This paper presents the ideal spatio-temporal pulse structure that is required to produce exawatt-scale pulses based on simultaneous chirped beam and chirped pulse amplification in a Nd:Mixed-glass laser system. It is shown, that a 100 fs Fourier transform-limited pulse is created from a 20 ns duration stretched beam-pulse after propagating through an appropriate six-grating compressor arrangement. Quantitative results, from a ray-tracing model of the six-grating compressor, provide the detailed spatio-spectral and spatio-temporal pulse distributions of the stretched pulse along with the higher-order phase distortions compensated by this pulse compression scheme.

Generalized design of an exawatt-class, high-peak-power laser based on a single-aperture, NIF-like, Nd:Glass beamline is presented. Results of a ray-trace model of the underlying, novel compressor configuration and gain effects in the amplifier are discussed.

A novel, witness-sample-based technique for detection of isotope-specific material signatures excited by quasi-mono-energetic gamma sources is presented. Proof of principle demonstrations involving the detection, assay, and imaging of 7Li are reviewed.

For more than half a century, researchers around the world have been engaged in attempts to achieve fusion ignition as a proof of principle of various fusion concepts. As recently reported, a burning plasma state, where the alpha-heating in the plasma is the primary source of heating, was achieved in laboratory experiments. Following the Lawson criterion, an ignited plasma is one where the fusion heating power is high enough to overcome all the physical processes that cool the fusion plasma, creating a positive thermodynamic feedback loop with rapidly increasing temperature. In inertially confined fusion, ignition is a state where the fusion plasma can begin ``burn propagation'' into surrounding cold fuel, enabling the possibility of high energy gain. While ``scientific breakeven'' (i.e. unity target gain) has not yet been achieved, this talk reports the first controlled fusion experiment on the National Ignition Facility to produce capsule gain greater than unity (here 5.8) and reach ignition by many different formulations of the Lawson criterion. In the talk, we will discuss some key basic physics inertial confinement fusion (ICF) principles behind the burning plasma and ignition results as well as discuss future challenges.

We demonstrate the possibility to directly detect microgram amounts of the isotope 7 L i using a quasi-monochromatic high-energy photon beam. The isotope selective detection is based on a witness scatterer absorbing and re-emitting photons via nuclear resonance fluorescence. This enables the detection of isotopes with microgram accuracy at long distances from the actual sample. Further, we demonstrate that the technique can deliver quantitative information without specific knowledge of the photon flux and no spectral capabilities or knowledge of the resonance fluorescence cross section. Detection of low-atomic-weight isotopes screened by heavy shielding is also shown. The techniques described are applicable to all next-generation, ultrahigh brilliance, laser-Compton light sources currently under construction.

rf photoinjectors produce incredibly bright electron beams enabling advanced photon science applications such as the current generation of free electron lasers and high energy x-rays and gammarays via laser-Compton scattering. A second generation 5.59 cell X-band rf gun has been developed, installed, conditioned, commissioned, tuned, and used to produce laser-Compton x-rays and multiple electron bunches. A charge per bunch from a few pC to 500 pC has been measured, consistent with a quantum efficiency of 5 x 10(-5) using a 263 nm 10 Hz photocathode drive laser. The rf gun has operated close to design performance at high gradient, and more reliably at lower gradient achieving a root mean square normalized emittance of 0.3 mm mrad at both 80 pC at 185 MV/m, and 40 pC at 165 MV/m. Thermal emittance is estimated at 0.55 mmmrad/mm. Energy spread of 0.03% has been achieved. These results agree very well with modeling predictions for the operating conditions under which the measurements were made. Unusually disruptive breakdowns were observed with an applied magnetic field of 0.5T used for emittance compensation.

Measured highly elevated gains of proton–boron (HB11) fusion (Picciotto et al. , Phys. Rev. X 4 , 031030 (2014)) confirmed the exceptional avalanche reaction process (Lalousis et al. , Laser Part. Beams 32 , 409 (2014); Hora et al. , Laser Part. Beams 33 , 607 (2015)) for the combination of the non-thermal block ignition using ultrahigh intensity laser pulses of picoseconds duration. The ultrahigh acceleration above $10^{20}~\text{cm}~\text{s}^{-2}$ for plasma blocks was theoretically and numerically predicted since 1978 (Hora, Physics of Laser Driven Plasmas (Wiley, 1981), pp. 178 and 179) and measured (Sauerbrey, Phys. Plasmas 3 , 4712 (1996)) in exact agreement (Hora et al. , Phys. Plasmas 14 , 072701 (2007)) when the dominating force was overcoming thermal processes. This is based on Maxwell’s stress tensor by the dielectric properties of plasma leading to the nonlinear (ponderomotive) force $f_{\text{NL}}$ resulting in ultra-fast expanding plasma blocks by a dielectric explosion. Combining this with measured ultrahigh magnetic fields and the avalanche process opens an option for an environmentally absolute clean and economic boron fusion power reactor. This is supported also by other experiments with very high HB11 reactions under different conditions (Labaune et al. , Nature Commun. 4 , 2506 (2013)).

The Laser Beam Delivery (LBD) system technical design report covers the interface between the High Power Laser System (HPLS) and the experiments, together with the pulse quality management. The laser transport part of the LBD has a number of subsystems as follows: the beam transport lines for the six main outputs of HPLS, the additional short and long pulses and the synchronization system including the timing of the laser pulses with the Gamma Beam System (GBS) and the experiments on femtosecond timescale. Pulse quality management, discussed further here, consist in the generation and delivery of multiple HPLS pulses, coherent combining of the HPLS arms, laser pulse diagnostics on target, laser beam dumps, shutters and output energy adaption.

After the very long consideration of the ideal energy source by fusion of the protons of light hydrogen with the boron isotope 11 (boron fusion HB11) the very first two independent measurements of very high reaction gains by lasers basically opens a fundamental breakthrough. The non-thermal plasma block ignition with extremely high power laser pulses above petawatt of picosecond duration in combination with up to ten kilotesla magnetic fields for trapping has to be combined to use the measured high gains as proof of an avalanche reaction for an environmentally clean, low cost and lasting energy source as potential option against global warming. The unique HB11 avalanche reaction is are now based on elastic collisions of helium nuclei (alpha particles) limited only to a reactor for controlled fusion energy during a very short time within a very small volume.

Get PDF Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text D. J. Gibson, G. G. Anderson, Y. Hwang, R. A. Marsh, and C. P. J. Barty, "Multi-bunch Operation of a Laser-Compton X-ray Source Based on Compact X-band Accelerator Technology," in High-Brightness Sources and Light-Driven Interactions, OSA technical Digest (online) (Optica Publishing Group, 2016), paper EM1A.3. Export Citation BibTex Endnote (RIS) HTML Plain Text Get Video Citation alert Save article

Fusion energy from reacting hydrogen (protons) with the boron isotope 11 (HB11) resulting in three stable helium nuclei, is without problem of nuclear radiation in contrast to DT fusion. But the HB11 reaction driven by nanosecond laser pulses with thermal compression and ignition by lasers is extremely difficult. This changed radically when irradiation with picosecond laser pulses produces a non-thermal plasma block ignition with ultrahigh acceleration. This uses the nonlinear (ponderomotive) force to surprizingly resulting in same thresholds as DT fusion even under pessimistic assumption of binary reactions. After evaluation of reactions trapped cylindrically by kilotesla magnetic fields and using the measured highly increased HB11 fusion gains for the proof of an avalanche of the three alphas in secondary reactions, possibilities for an absolutely clean energy source at comptitive costs were concluded.

Lasers and laser-based sources are now routinely used to control and manipulate nuclear processes, e.g. fusion, fission and resonant nuclear excitation. Two such “nuclear photonics” activities with the potential for profound societal impact will be reviewed in this presentation: the pursuit of laser-driven inertial confinement fusion at the National Ignition Facility and the development of laser-based, mono-energetic gamma-rays for isotope-specific detection, assay and imaging of materials.

The National Ignition Facility (NIF) at Lawrence Livermore National Laboratory is the first of a kind megajoule-class laser with 192 beams capable of delivering over 1.8 MJ and 500TW of 351nm light [1], [2]. It has been commissioned and operated since 2009 to support a wide range of missions including the study of inertial confinement fusion, high energy density physics, material science, and laboratory astrophysics.In order to advance our understanding, and enable short-pulse multi-frame radiographic experiments of dense cores of cold material, the generation of very hard x-rays above 50 keV is necessary. X-rays with such characteristics can be efficiently generated with high intensity laser pulses above 10(17) W/cm(2) [3]. The Advanced Radiographic Capability (ARC) [4] which is currently being commissioned on the NIF will provide eight, 1 ps to 50 ps, adjustable pulses with up to 1.7 kJ each to create x-ray point sources enabling dynamic, multi-frame x-ray backlighting.This paper will provide an overview of the ARC system and report on the laser performance tests conducted with a stretched-pulse up to the main laser output and their comparison with the results of our laser propagation codes.