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The interaction of relativistic short-pulse lasers with matter produces fast electrons with over megaampere currents, which supposedly heats a solid target isochorically and forms a hot dense plasma. In a picosecond timescale, however, thermal diffusion from hot preformed plasma turns out to be the dominant process of isochoric heating. We describe a heating process, fast thermal diffusion, launched from the preformed plasma heated resistively by the fast electron current. We demonstrate the fast thermal diffusion in the keV range in a solid density plasma by a series of one-dimensional particle-in-cell simulations. A theoretical model of the fast thermal diffusion is developed and we derive the diffusion speed as a function of the laser amplitude and target density. Under continuous laser irradiation, the diffusion front propagates at a constant speed in uniform plasma. Our model can provide a guideline for fast isochoric heating using future kilojoule petawatt lasers.

A counter-propagating laser-beam platform using a spherical plasma mirror was developed for the kilojoule-class petawatt LFEX laser. The temporal and spatial overlaps of the incoming and redirected beams were measured with an optical interferometer and an x-ray pinhole camera. The plasma mirror performance was evaluated by measuring fast electrons, ions, and neutrons generated in the counter-propagating laser interaction with a Cu-doped deuterated film on both sides. The reflectivity and peak intensity were estimated as ∼50% and ∼5 × 1018 W/cm2, respectively. The platform could enable studies of counter-streaming charged particles in high-energy-density plasmas for fundamental and inertial confinement fusion research.

Fast isochoric heating of a pre-compressed plasma core with a high-intensity short-pulse laser is an attractive and alternative approach to create ultra-high-energy-density states like those found in inertial confinement fusion (ICF) ignition sparks. Laser-produced relativistic electron beam (REB) deposits a part of kinetic energy in the core, and then the heated region becomes the hot spark to trigger the ignition. However, due to the inherent large angular spread of the produced REB, only a small portion of the REB collides with the core. Here, we demonstrate a factor-of-two enhancement of laser-to-core energy coupling with the magnetized fast isochoric heating. The method employs a magnetic field of hundreds of Tesla that is applied to the transport region from the REB generation zone to the core which results in guiding the REB along the magnetic field lines to the core. This scheme may provide more efficient energy coupling compared to the conventional ICF scheme., It is desirable to deposit more energy in the dense plasma core to trigger the fusion ignition. Here the authors demonstrate enhanced energy coupling from laser to plasma core by using solid targets and guiding the transport of relativistic electron beam with external magnetic field.

Fast isochoric laser heating is a scheme to heat a matter with relativistic-intensity ($>$ 10$^{18}$ W/cm$^2$) laser pulse or X-ray free electron laser pulse. The fast isochoric laser heating has been studied for creating efficiently ultra-high-energy-density (UHED) state. We demonstrate an fast isochoric heating of an imploded dense plasma using a multi-picosecond kJ-class petawatt laser with an assistance of externally applied kilo-tesla magnetic fields for guiding fast electrons to the dense plasma.The UHED state with 2.2 Peta-Pascal is achieved experimentally with 4.6 kJ of total laser energy that is one order of magnitude lower than the energy used in the conventional implosion scheme. A two-dimensional particle-in-cell simulation reveals that diffusive heating from a laser-plasma interaction zone to the dense plasma plays an essential role to the efficient creation of the UHED state., 8 pages, 4 figures, 1 table

A mechanism of isochoric heating of a solid density plasma by a kilojoule (kJ) class laser with relativistic intensity and a ten picosecond (ps) pulse duration is delineated by collisional Particle-in-Cell (PIC) simulations. Before an emergence of kJ class lasers, plasma heating by the laser-accelerated relativistic electron beam (REB) has been studied as the dominant isochoric heating process by intense lasers. A recent experiment using a kJ class laser indicates that the thermal diffusion from the hot plasma surface becomes the dominant process of the isochoric heating in the ps scale laser irradiation. In this article, we demonstrate that a transition of the dominant isochoric heating process from the REB heating to the thermal diffusion happens in the 10 ps laser irradiation. The diffusion heat front propagates with the speed approximately 2 μm/ps in an Aluminum target. Additionally, the hot dense plasma expands to create a steep laser-plasma interface, which is found to reduce REB energy.

High-power lasers in the relativistic intensity regime with multi-picosecond pulse durations are available in many laboratories around the world. Laser pulses at these intensities reach giga-bar level radiation pressures, which can push the plasma critical surface where laser light is reflected. This process is referred to as the laser hole boring (HB), which is critical for plasma heating, hence essential for laser-based applications. Here we derive the limit density for HB, which is the maximum plasma density the laser can reach, as a function of laser intensity. The time scale for when the laser pulse reaches the limit density is also derived. These theories are confirmed by a series of particle-in-cell simulations. After reaching the limit density, the plasma starts to blowout back toward the laser, and is accompanied by copious superthermal electrons; therefore, the electron energy can be determined by varying the laser pulse length., Different energy transport mechanisms come into play when intense laser pulses interact with dense plasma. Here the authors provide a limit on the plasma density reachable with an intense laser and an insight into the hole boring process.

The plasmid encoding His-tagged organophosphorus hydrolase (OPH) cloned from Sphingobium fuliginis was modified to be transferred back to this bacterium. The replication function of S. amiense plasmid was inserted at downstream of OPH gene, and S. fuliginis was transformed with this plasmid. The transformant produced larger amount of active OPH with His-tag than E. coli.

The interaction of dense plasmas with an intense laser under a strong external magnetic field has been investigated. When the cyclotron frequency for the ambient magnetic field is higher than the laser frequency, the laser's electromagnetic field is converted to the whistler mode that propagates along the field line. Because of the nature of the whistler wave, the laser light penetrates into dense plasmas with no cutoff density, and produces superthermal electrons through cyclotron resonance. It is found that the cyclotron resonance absorption occurs effectively under the broadened conditions, or a wider range of the external field, which is caused by the presence of relativistic electrons accelerated by the laser field. The upper limit of the ambient field for the resonance increases in proportion to the square root of the relativistic laser intensity. The propagation of a large-amplitude whistler wave could raise the possibility for plasma heating and particle acceleration deep inside dense plasmas., Comment: 8 pages, 8 figures, accepted for publication in PRE

We study the plasma expansion dynamics in over-picosecond relativistic laser-foil interactions using one-dimensional particle-in-cell (PIC) simulations. A new expansion mode ‘isofield expansion’ appears after the well-known isothermal expansion due to the continuous energy input from the laser light to the plasma. The blowout of the heated plasma at the front surface triggers the transition from the isothermal mode to the new mode. In the new expansion mode, electrons and ions expand quasi-neutrally with a constant sheath electric field, and a large scale low density plasma is formed where superthermal electrons are produced efficiently. A two-dimensional PIC simulation confirms the appearance of the isofield expansion mode after the plasma blowout for a large focal spot laser.

We study the one-dimensional expansion of a thin foil plasma irradiated by a high intensity laser with multi-picosecond (ps) pulse durations by using particle-in-cell simulation. Electrons are found to recirculate around the expanding plasma for many times, which results in stochastic heating leading to increase of the electron temperature in the multi-ps time scale beyond the ponderomotive scaling. The conventional isothermal model cannot describe such an expansion of plasmas in the long time scale. We here developed a non-isothermal plasma expansion theory that takes the time dependence of electron temperature into account for describing the multi-ps interactions in one-dimensional geometry. By assuming that the time scale of electron temperature evolution is slow compared with the plasma expansion time scale, we derived a non-self-similar solution. The time evolution of ion maximum energy obtained by the non-isothermal theory explains the details of that observed in the simulation.

Bactericidal effects of phosphate buffered saline treated with electrically neutral oxygen radicals on Escherichia coli (E. coli) are studied using an atmospheric pressure radical source and colony counting method. To clarify the bactericidal mechanism, the chemistry in phosphate buffers treated with oxygen radicals with and without saline has been quantitatively investigated using the well-established chemical reporters N,N-diethyl-p-phenylenediamine reagent and Amplex Red for residual chlorine (HClO and ClO−) and hydrogen peroxide (H2O2), respectively. From the results, we have found that the presence of chlorine in the solutions treated with oxygen radicals is the most important factor in the further chemical reactions to generate hypochlorous acid in E. coli death, and H2O2 is also linked to the bactericidal effect via an indirect chemical pathway.

We have developed a new formula for a relativistic ponderomotive force of transversely localized laser fields based on the noncanonical Lie perturbation method by finding proper coordinates and gauges in the variational principle. The formula involves new terms represented by second and third spatial derivatives of the field amplitude, so that the ponderomotive force depends not only on the local field gradient, but also on the curvature and its variation. The formula is then applicable to a regime in which the conventional formula is hardly applied such that nonlocal and/or global extent of the field profile becomes important. The result can provide a theoretical basis for describing nonlinear laser-plasma interaction including such nonlocal effects, which is examined via particle-in-cell simulation of laser propagation in a plasma with a super Gaussian transverse field profile.

In order to study the particle dynamics in strongly nonuniform and/or localized laser fields, we extend the theory of the ponderomotive force by taking into account the laser field structure up to the higher order with respect to 𝜖, the ratio between the particle excursion length and the scale length of the laser field amplitude variation. This extension is realized by keeping the rigorous phase space Lagrangian structure utilizing the noncanonical Lie perturbation up to higher orders. As a result, the equations of motion in a oscillation center coordinate is derived up to the third order of 𝜖, which include the second and third spatial derivatives of the laser field amplitude. This denotes that the ponderomotive force depends not only on the local field gradient, but also on the curvature and its derivative. The additional higher-order force originates from the nonlocal particle motion around the oscillation center, which could have an influence especially in the case of tight focusing in the level of laser wavelength., IFSA 2011 - Seventh International Conference on Inertial Fusion Sciences and Applications

Interaction between media composed of clusters and high intensity lasers in the radiation dominant regime, i.e., intensity of 1022−23 W/cm2, is studied based on the particle-in-cell simulation that includes the radiation reaction. By introducing target materials that have the same total mass but different internal structures, i.e., uniform plasma and cluster media with different cluster radii, we investigate the effect of the internal structure on the interaction dynamics, high energy radiation emission, and its reaction. Intense radiation emission is found in the cluster media where electrons exhibit non-ballistic motions suffering from strong accelerations by both the penetrated laser field and charge separation field of clusters. As a result, the clustered structure increases the energy conversion into high energy radiations significantly at the expense of the conversion into particles, while the total absorption rate into radiation and particles remains unchanged from the absorption rate into particle...

Dialysis patients often develop constipation and changes in intestinal bacterial flora. Indoxylsulfuric acid (IS) levels rise as glomerular filtration decreases, and patients with renal failure have high IS. Elevated IS is also caused by increased indole due to altered intestinal flora (Takayama et al, Am J Kidney Dis. 2003). We investigated whether administering partially hydrolyzed guar gum (PHGG) (Sunfiber: a product of Taiyokagaku Co., Ltd., Japan) ameliorates constipation and improves nutritional status in dialysis patients, while decreasing IS levels. Thirty-five patients on maintenance dialysis (mean age, 71 ± 9; male/female= 22/13) ingested PHGG (10 g/day) for 6 weeks. Defecation was scored before and after PHGG intake using a modified Constipation Assessment Scale-Long Term (Japanese version). Nutritional status was rated according to the Geriatric Nutritional Risk Index (GNRI) before and after PHGG intake. IS was measured in 8 patients taking PHGG orally for 24 weeks, for comparison with those in 8 patients not on PHGG. Constipation scores decreased from 7.9 to 5.0 (p 〈.01) and GNRI increased from 95.0 ± 5.0 to 95.9 ± 5.7 (p 〈.05), reflecting amelioration of constipation and improved nutritional status. The ratio of IS after to that before PHGG intake was calculated to analyze the magnitude of IS change. The ratio in patients not on PHGG was 1.2 ± 0.3, i.e. IS rose, while that in patients taking PHGG was significantly reduced (0.8 ± 0.3, p 〈.05). Our results indicate PHGG consumption to ameliorate constipation and improve nutritional status, and that continued intake reduces IS, in dialysis patients.

In order to study the nonlocal particle dynamics in tightly focused laser fields in the order of wave length, we present a theoretical framework of relativistic ponderomotive force by using the noncanonical Lie perturbation theory based on the phase space Lagrangian formalism that keeps the Hamiltonian structure rigorously. Introducing a smallness parameter e, the ratio of the particle excursion length to the scale length of the gradient of the laser field amplitude, we perform the perturbation analysis up to the second order e2, which contain the effect of the field curvature, and obtain the oscillation center equation of motion averaged over the fast laser period. A betatron-like oscillation which corresponds to a confinement state of the particle in the laser field without suffering ejection due to the field curvature is analytically found.

In recent years, high power short pulse lasers in the range of 1018–22 W/cm2 have been developed and explored new science and applications. One of them is the fast ignition-based laser fusion, which is expected as one of clean and abundant energy sources. In determining the interaction between such high intensity lasers and plasmas, the ponderomotive force (light pressure) plays an essential role due to the strong non-uniformity of the laser field strength originated from tight focusing of the laser light. The force has been expressed as that proportional to the gradient of the laser field amplitude at the oscillation center of the particle. However, under the tight focusing, not only the gradient, which corresponds to the first-order perturbation to the uniform field, but also the higher order structures, e.g. field curvature to the second order, becomes important in determining the particle orbit. In order to precisely describe the relativistic ponderomotive force including such effects, here, we introduce the noncanonical Lie perturbation theory. We successfully derived the oscillation-center equation of motion up to the second order keeping the Hamiltonian structure rigorously. The resulting equation is found to be same as that of the first order indicating that no additional force appears up to the second order due to the symmetric nature of the field curvature.

Gout is a disorder of uric acid metabolism potentially associated with deposition of urate crystals in soft tissues and joint inflammation. With recent advances in the diagnosis/treatment of gout, gouty tophi are rarely encountered, except those caused by poor treatment. Patients with tophi should be treated carefully, because uric acid lowering in these patients can precipitate gout attacks. Here, we report a patient with giant gouty tophi in whom a fierce gouty attack was precipitated after urgent hemodialysis. An 80-year-old man was admitted to our hospital with gastrointestinal hemorrhage. He had a long history of renal failure and gout and had routinely taken nonsteroidal antiinflammatory drugs (NSAIDs) for gout attacks by preference. Therefore, because of insufficient treatment, he developed numerous gouty tophi in multiple joints (Fig. 1a). On admission, he had anemia (hemoglobin 5.7 g/ dl), renal failure (serum creatinine 4.2 mg/dl, blood urea nitrogen 85.7 mg/dl), and hyperkalemia (serum potassium 6.3 mmol/l). In view of the renal failure and upper gastrointestinal endoscopy revealing a bleeding duodenal ulcer, we performed urgent hemodialysis. After dialysis initiation, the patient complained of fierce pain in multiple joints, which had become red and swollen (Fig. 1c). Body temperature increased to 39.5 C and serum C-reactive protein level to 22.5 mg/dl. Since knee joint aspiration revealed urate crystals, we concluded that the gout attack was triggered by acute mobilization of uric acid by dialysis. However, despite the inflammation, the persistent renal failure necessitated continuation of the hemodialysis. Furthermore, despite the severe pain, NSAID use was contraindicated because of the duodenal ulcer. Therefore, oral steroid therapy (prednisolone 30 mg daily, then gradually reduced) was initiated, which reduced the inflammatory reaction and joint swellings (Fig. 1d). Finally, dialysis was discontinued after 8 sessions as renal function improved. After the acute phase, allopurinol (100 mg daily) was started to lower uric acid production; however, it led to liver dysfunction (total bilirubin 12.1 mg/dl). After recovery of liver function, therefore, treatment with febuxostat was initiated (10 mg daily for 2 weeks, then 20 mg daily for a further 4 weeks), which safely decreased the serum uric acid, without any side-effects; eventually, the treatment resulted in marked resolution of the tophaceous gout (Fig. 1b). Urate crystals are normally coated with serum proteins (apolipoprotein E or B) which inhibit urate crystal-induced inflammatory responses [1]. Serum urate reduction causes partial dissolution of microtophi with release of uncoated urate crystals. Macrophages recognize uncoated urate crystals by specific Toll-like receptors, and activate the innate immune system; then, production of interleukin-1 triggers a cascade of pro-inflammatory cytokines [2]. Febuxostat, a potent xanthine oxidase inhibitor, is metabolized mainly by glucuronide formation and oxidation in the liver, and can therefore be safely used in patients with renal failure [3]. We achieved successful control of the inflammation with the steroid and resolution of the gouty tophi with febuxostat. Our findings emphasize the need to bear the N. Iwata H. Maeda (&) J. Yoshimura S. Sakai Shimonoseki City Hospital, 1-13-1 Koyo-cho, Yamaguchi 750-8520, Japan e-mail: gridlejp@yahoo.co.jp

A theory of relativistic ponderomotive force of transversely localized laser fields is presented by taking into account the nonlocal effects that correspond to higher order terms of the expansion parameter ϵ≡l/L, i.e., the ratio between particle excursion length and scale length of the field amplitude gradient, while the existing local theory is the first order of ϵ. As a method for preserving the Hamiltonian structure up to higher orders, we employ the variational principle in noncanonical phase space coordinates incorporated with the Lie transformation. By finding noncanonical coordinates and gauges, we obtain a new formula for the ponderomotive force that involves new terms in the third order represented by the second and third spatial derivatives. The force then depends not only on the local field gradient but also on the curvature and its variation which represent the effects of higher-order nonlocal particle motion. The higher-order terms are found to be subject to the symmetry of the field structur...

Relativistic particle motion in a non-uniform linearly polarized high intensity laser field is analyzed by using the noncanonical Lie perturbation method, which is based on the perturbation theory of the phase space Lagrangian. By introducing the smallness parameter e as the ratio between the excursion length l and the scale length of the laser field amplitude L, the relativistic ponderomotive force and particle motion are derived up to the second order with respect to e, which correspond to the nonlocal extension of the conventional ponderomotive force. Specifically, the particle is found to exhibit a betatron-like oscillation with long period characterized by the curvature of the laser field amplitude. c

A methodology describing the particle motion in a spatially localized high-power laser field in the relativistic regime is presented based on the noncanonical Lie perturbation method, which is comprehensive compared with those based on the conventional averaging method to the equation of motion. We successfully derived the relativistic ponderomotive force in a laser field with a radial intensity gradient and the corresponding particle dynamics up to the first order with respect to the expansion parameter e ∼ λ/L (= laser wavelength/scale length of the transverse laser amplitude). The longitudinal motion was found to be secular and characterized by a growing oscillation exhibiting a cubic dependence on the laser amplitude.