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Radiographic imaging is an omnipresent tool in basic research and applications in industry, material science and medical diagnostics. Often, the information contained in more than one modality can be valuable, but difficult to access simultaneously. This talk reviews developments in laser-plasma-accelerators for protons, electrons and x-rays from solid and gas targets for multimodal imaging. Laser-driven ion acceleration and x-ray generation have been investigated using tungsten micro-needle-targets at the Texas Petawatt laser [1]. The experiments and supporting numerical simulations reveal peaked proton spectra around 10 MeV with significant particle count and a strong keV level x-ray source. The source size for both has been measured to be in the few-µm range. Both sources were eventually applied to simultaneous radiographic imaging of biological and technological samples. In recent experiments at BELLA Center’s high repetition rate 100 TW dual-arm laser, steps were taken towards bi-modal x-ray and electron imaging of dynamic events such as hydrodynamic shocks, in which often both density and electro-magnetic fields are important quantities to measure. Here, a shock was driven by a 1 Joule, 200 ps laser focused in a 30 µm wide water jet. A laser wakefield accelerator was driven by a second 2 Joule, 40 fs laser in a gas-jet target, providing both 150 MeV electrons and broadband betatron x-rays up to ˜10 keV for projection imaging. This research aims to leverage unique properties readily available in laser plasma accelerators for applications. Specifically, the emission of pulsed, bright, multimodal bursts of radiation can open new ways in biological imaging (e.g., with ns-synchronized ions and x-rays) and in high-resolution diagnostics for high-energy density science (e.g., with fs-synchronized electrons and x-rays). [1] T. M. Ostermayr et al., “Laser-driven x-ray and proton micro-source and application to simultaneous single-shot bi-modal radiographic imaging,” Nat. Commun., vol. 11, no. 1, pp. 1–9, Dec. 2020. This work was supported by the DFG via the Cluster of Excellence Munich-Centre for Advanced Photonics (MAP) and Transregio SFB TR18. This work has been carried out within the framework of the EUROfusion Consortium and has received funding, through the ToIFE, from the European Union’s Horizon 2020 research and innovation program under grant agreement number 633053. The authors acknowledge funding by the Air Force Office of Scientific Research (AFOSR)(FA9550-14-1-0045, FA9550-17-1-0264). Work supported by DOE FES under grant DE-SC0020237. Work supported by US DOE NNSA DNN R&D, by Sc. HEP, by the Exascale Computing Project and by FES LaserNetUS under DOE Contract DE-AC02-05CH11231.

Transition Edge Sensor (TES) is a key component for Hot Universe Baryon Survey (HUBS), which is proposed in China to address the so-called “missing baryon problem”. A stable heat sink below 100 mK is needed for the detector’s noise suppression and high resolution. Since HUBS is a satellite based observation mission, a complicated cooling system suitable for space application becomes an important supporting sub-system. A compounded cooling system, including a mechanical cryocooler and an adiabatic magnetization refrigerator (ADR), has been proposed for HUBS. The mechanical cryocooler is used as the pre-cooling 4 K stage, and the ADR is responsible for further reducing the temperature to below 100 mK. High-frequency pulse tube cryocooler (HPTC) and HPTC combined with Joule Thompson cooler (J-T) are two candidates for the mechanical pre-cooling stage, both of which are currently under development. The ADR is being designed and processed. In this paper, we will present the preliminary architecture of the HUBS cooling system, as well as the latest states of HPTC, J-T, and ADR.

In this paper, a novel method to generate optical frequency combs (OFCs) using nanoscale structures is explored. The growing demand for on-chip photonic processing dictates the need for multi-wavelength light sources, such as OFCs, that can be densely integrated with low processing power. Photonic crystal structues provide a viable method to generate all-optical modulation with sub-femto joule switching power and high density integration potential. This method of all-optical modulation is utilised here to generate an OFC from photonic crystal nanocavities and waveguides. Very- at-topped optical frequency combs with a small intensity variation can be generated based on theoretical predictions via detailed analysis of coupled mode theory for photonic crystal nanocavities and waveguides.

SPIE Conference on EUV and E-ray Optics, SPIE LASE, Prague, Czech republic, 3 Apr 2019 - 4 Apr 2019; Proceedings of SPIE 11270, 1127002 (2019). doi:10.1117/12.2563450, The generation and use of THz radiation for electron acceleration and manipulation of electron bunches has progressed over the last decade to a level where practical devices for THz guns, acceleration and a wide range of beam manipulations have become possible. Here, we present our progress on generation of single-cycle THz pulses at the two-hundred micro- Joule level to drive advanced acceleration and beam manipulation devices. Specifically, we use pulses centered at 0.3 THz to power a segmented terahertz electron accelerator and manipulator (STEAM) capable of performing multiple high-field operations on the 6D-phase-space of ultrashort electron bunches. Using this STEAM device, we demonstrate record THzacceleration of >60 keV, streaking with 2 kT/m strength, compression to ~100 fs as well as real-time switching between these modes of operation. The STEAM device demonstrates the feasibility of THz-based electron accelerators, manipulators and diagnostic tools enabling science beyond current resolution frontiers with transformative impact., Published by SPIE, Bellingham, Wash.

Recently, non-fullerene n-type organic semiconductors (n-OS) have attracted significant attention as acceptors in organic photovoltaics (OPVs) due to their great potential to realize high power conversion efficiencies (PCEs). In this regard, a rational design of central fused ring unit of the n-OS molecules is crucial to maximize the state-of-the-art PCEs. Here, we report a new class of n-OS acceptor, Y series, that employ a ladder-type electron-deficient-core-based central fused ring to fine tune its absorption and energy levels. Among these new acceptors, the Y6-based OPVs exhibit a high efficiency of 15.7 % (both in conventional or inverted structures), and a certified efficiency of 14.9 % by an inverted structure. The electron-deficient-core-based fused ring reported in this work opens a new way in the molecular design of high performance n-OS acceptors for OPVs. References: [1] Nat. Commun., 2019, 10: 570 [2] Adv.Mater., 2019, 31: 1807577 [3] Joule, 2019, 4:1140-1151

TRUMPF Scientific Lasers provides ultrafast laser sources for the scientific community with high pulse energies and high average power. All systems are based on the industrialized TRUMPF thin-disk technology. Regenerative amplifiers systems with multi-millijoule pulses, kilohertz repetition rates and picosecond pulse durations are available. Record values of 220mJ at 1kHz could be demonstrated originally developed for pumping optical parametric amplifiers. A huge step will be to combine high energies, 1J per pulse, with average powers of several hundred watts to a kilowatt. Multipass amplifiers based on the thin-disk technology were successfully used to realize picosecond amplifiers with more than 2kW of average power. Nevertheless, the pulse energy was in the μJ or low mJ range. At TRUMPF Scientific Lasers these experiences will lead the way to set-up a system running at 1kHz repetition rate and a target pulse energy of 1J. Within the paper the roadmap to a Joule system will be presented as well as first results from a laboratory set-up.

With the exponential growth of bandwidth requirement of data centers and supercomputers, energy already limits our ability to process and communicate information. There is an urgent need to develop low-energy photonic devices and systems that can push the energy efficiency to attojoule/bit level. Traditional silicon photonic modulators rely on the plasma dispersion effect by free-carrier injection or depletion, which occupies a large footprint and consumes relatively high energy for optical interconnects. Here we report an ultra-compact hybrid silicon-conductive oxide electro-optic modulator with total device footprint of 0.6 × 8 μm2. The device was built by integrating voltage-switched transparent conductive oxide with one-dimensional silicon photonic crystal nanocavity. The active modulation volume is only 0.06 µm3, which is less than 2% of the lambda-cubic volume. The device operates in the dual mode of cavity resonance and optical absorption by exploiting the refractive index modulation from both the conductive oxide and the silicon waveguide induced by the applied gate voltage. Such a metal-free, hybrid silicon-conductive oxide nanocavity modulator also demonstrates only 0.5 dB extra optical loss, high E-O efficiency of 250pm/V, and low energy consumption of 3fJ/bit. In addition, we will discuss strategy to further improve the energy efficiency below 1fJ/bit and to achieve high-speed modulation above 10Gbps. The combined results achieved through the holistic design opened a new route for the development of next generation electro-optic modulators that can be used for future on-chip optical interconnects.

Kilo-joule Laser System (KLS) is constructed as a X-ray backlighting resource, to provide X-ray for performing X-ray diagnostic experiments. As a crucial component of KLS, backlighting terminal system has such function as frequency conversion, color separation, laser transport, beam focusing, target alignment and debris shielding, enabling focal spot energy(2ω) of 500J in 1ns pulse, with target alignment accuracy of ≤±25 μm.

The Galaxy Evolution Probe (GEP) is a proposed far infrared-optimized observatory designed for zodiacal-light-limited imaging and spectroscopy in the 10 to 250 micron band. The GEP telescopes and instruments are planned to be actively cooled with the system in a sun-earth L2 halo orbit. A detailed description of the GEP mission concept is documented in [1]. Crucial to the scientific performance of GEP is the thermal architecture; it must support a range of cryogenic elements, ranging from the full telescope optical assembly at around 4 K to the far-IR focal planes consisting of kinetic inductance detector (KID) arrays cooled to 100 mK. Given the mass operating at these low temperatures, the thermal system is one of the main drivers of mission cost and complexity. We present a solution to the GEP thermal design that is realizable within a probe-class envelope. The baseline system utilizes a multi-stage adiabatic demagnetization refrigerator (ADR) for the 100mK base; the ADR system also provides an intercept at 1K. ADR systems similar to that in our design have flown, and among sub-K options, ADRs offer high Carnot efficiency. The ADR rejects heat to a hybrid Joule Thompson (JT) and Stirling or PT Cryocooler with a lowtemperature stage at 4 K as well as an intercept at 20 K. These coolers are also mature systems with flight heritage on most subcomponents.

A multipurpose laser damage test facility delivering pulses from 1ns to 20ns and designed to output energy 40 Joule at 351nm is presented. The laser induced damage threshold (LIDT) measurement and test procedure are performed. The original system consist of the online detection system based on the microscopy and an energy detection device based on the scientific grade Charge Coupled Device (CCD) which provides the method to measure the LIDT with high accuracy. This method is an efficient way that allows measuring a small area fluence which the defect exposed. After complete test procedure and data treatment the damage position of the defect has been found. Then we can obtain the local fluence of small area when the damage occurred. This procedure provides a straightforward means of laser-damage threshold obtained from the test method. Damage correlation of measures is discussed in connection with present theoretical understanding of laser damage phenomenon. The damage process in transparent dielectric materials being the results of complex processes involving multi-photon ionization, avalanche ionization, electron-phonon coupling, and thermal effects. Those complex processes lead to the damage on the optical surface. We performed a method to measure the local fluence which defects irradiated with high accurate.

Progress in the development of highly brilliant pump modules based on novel high-energy-class diode laser bars is presented, targeting long-pulse (2 ms) application in pumping Yb:CaF2 amplifier crystals. Bars with long resonators and high fill factors are used for low resistance and efficient cooling. Advanced extreme-double asymmetric epitaxial structures are used for high efficiency at high power. Facet passivation is used for long life at high powers, enabling operation at 600 W per bar (1.2 J). Performance of bars and passively cooled stacks is summarized and prospects for further performance enhancements are reviewed.

SOFRADIR was selected in the late 90’s for the production of 320×256 MW detectors for major European missile programs. This experience has established our company as a key player in the field of missile programs. SOFRADIR has since developed a vast portfolio of lightweight, compact and high performance JT-based solutions for missiles. ALTAN is a 384x288 Mid Wave infrared detector with 15μm pixel pitch, and is offered in a miniature ultra-fast Joule- Thomson cooled Dewar. Since Sofradir offers both Indium Antimonide (InSb) and Mercury Cadmium Telluride technologies (MCT), we are able to deliver the detectors best suited to customers’ needs. In this paper we are discussing different figures of merit for very compact and innovative JT-cooled detectors and are highlighting the challenges for infrared detection technologies.

Most of space instruments and research facilities require test equipment with demanding opto-mechanical stability. In some specific cases, when the stability performance directly drives the final performance of the scientific mission and when feasibility is questionable, specific methods must be implemented for the associated technical risk management. In present paper, we will present our heritage in terms of methodology, design, test and the associated results for two specific systems : the SOPAC-POS and the MOTA, generating new references for future developments. From a performance point of view, we will emphasis on following key parameters : design symmetry, thermal load management, and material and structural choices. From a method point of view the difficulties arise first during design, from the strong coupling between the thermal, mechanical and optical performance models, and then during testing, from the difficulty of conceiving test setup having appropriate performance level. We will present how these limitations have been overcome. SOPAC-POS is the target alignment system of the LMJ, Laser Mega Joule, the French inertial confinement fusion research center. Its stability has been demonstrated by tests in 2014 after 10 years of research and development activities, achieving 1μm stability @ 6m during one hour periods. MOTA is an Optical Ground Support Equipment aiming at qualifying by tests the Flexible Combined Imager (FCI). FCI is an instrument for the meteorological satellite MTG-I, a program of and funded by the European Space Agency and under prime contractorship of Thales Alenia Space. Optimized design will allow to get better than 0.2 μrad stability for one hour periods, as required for MTF measurement.

A new generation of diode-pumped high-energy-class solid-state laser facilities is in development that generate multijoule pulse energies at around 10 Hz. Currently deployed quasi-continuous-wave (QCW) diode lasers deliver average inpulse pump powers of around 300 W per bar. Increased power-per-bar helps to reduce the system size, complexity and cost per Joule and the increased pump brilliance also enables more efficient operation of the solid state laser itself. It has been shown in recent studies, that optimized QCW diode laser bars centered at 940…980 nm can operate with an average in-pulse power of > 1000 W per bar, triple that of commercial sources. When operated at pulsed condition of 1 ms, 10 Hz, this corresponds to > 1 J/bar. We review here the status of these high-energy-class pump sources, showing how the highest powers are enabled by using long resonators (4…6 mm) for improved cooling and robustly passivated output facets for high reliability. Results are presented for prototype passively-cooled single bar assemblies and monolithic stacked QCW arrays. We confirm that 1 J/bar is sustained for fast-axis collimated stacks with a bar pitch of 1.7 mm, with narrow lateral far field angle (< 12° with 95% power) and spectral width (< 12 nm with 95% power). Such stacks are anticipated to enable Joule/bar pump densities to be used near-term in commercial high power diode laser systems. Finally, we briefly summarize the latest status of research into bars with higher efficiencies, including studies into operation at sub-zero temperatures (-70°C), which also enables higher powers and narrower far field and spectra.

In order to solve the problem of noncontact, wireless and nonmagnetic displacement sensing with nanometer resolution within critical limited space for ultraprecision displacement monitoring in the Joule balance device, a novel wireless digital capacitive displacement sensor (WDCDS) is proposed. The WDCDS is fabricated with brass and other nonmagnetic material and powered with a small battery inside, a small integrated circuit is assembled inside for converting and processing of capacitive signal, and low power Bluetooth is used for wireless signal transmission and communication. Experimental results show that the WDCDS proposed has a resolution of better than 1nm and a nonlinearity of 0.077%, therefore it is a delicate design for ultraprecision noncontact displacement monitoring in the Joule balance device, meeting the demand for properties of wireless, nonmagnetic and miniaturized size.

Since the dawn of precursory revolution in the seismology and electromagnetic radiation platform., F.T. Freund (2010) et.al, have used piezoelectric effect on the crustal geo-materials and emanation of seismic pre signals frequently. Their effect in form of ULF and VHF are commonly detected (by Greece and American seismologists)in the upper ionosphere from surface of globe. TEC, OLR. MMC are the consequent instrumentation in acquiring data to these pre-earthquake signals. Our attempt is to detect the signals prior to earthquake due to impending stress in the area and store the spreading destructive energy to electrical voltage applying the mathematics of piezoelectric equations and algebra. Energy released during seismic eruption is in the range of 10 13 to 1018 Joule for each event of 6 to 8 Mw. Spread and propagation of energy follows the Maxwell theory of wave equation and fundamental law of electricity and electromagnetism. Stress accumulated within the crustal block is triggered into bringing about geophysical and geochemical changes within the reservoir rocks interacting stress. Study made by pioneers in the seismic precursory development states generation of charge and coronal discharge prior seismicity within the rocks under stress. This is consequence to admixing of positive charge developed at unstressed volume and negative at stressed sub volume of rocks1 [F.T.Freidemann2010]. Ionosphere proturbance in form of ULF, ELF, ELS and EQL, EQS are the projected consequence of electromagnetic wave propagation 2 [10,11,15 ] Harnessing of electrical components from the energy propagated due to stress inducing EM waves is the aim of paper. Electrical discharge prior to seismicity within geo-materials is established phenomena which can be calibrated with the piezoelectric sensors application implanted for detection and harnessing the signals. These prior signals induced in form of electromagnetic response are felicitated into being converted into electrical energy with the suitable circuit diagram of capacitors, condensers and diodes in the piezoelectric mesh of sensors implication implanted within the ground of seismic prone area.

Highly oriented nylon and polyethylene fibres shrink in length when heated and expand in diameter. By twisting and then coiling monofilaments of these materials to form helical springs, the anisotropic thermal expansion has recently been shown to enable tensile actuation of up to 49% upon heating. Joule heating, by passing a current through a conductive coating on the surface of the filament, is a convenient method of controlling actuation. In previously reported work this has been done using highly flexible carbon nanotube sheets or commercially available silver coated fibres. In this work silver paint is used as the Joule heating element at the surface of the muscle. Up to 29% linear actuation is observed with energy and power densities reaching 840 kJ m-3 (528 J kg-1) and 1.1 kW kg-1 (operating at 0.1 Hz, 4% strain, 1.4 kg load). This simple coating method is readily accessible and can be applied to any polymer filament. Effective use of this technique relies on uniform coating to avoid temperature gradients.

We are developing one joule energy and one picosecond pulse duration laser system at the repetition rate of 120 Hz based on Yb-doped solid-state materials. The amplified output from the thin disk regenerative amplifier is amplified by a cryogenically conduction cooled single slab amplifier. In this work, we also present a new measurement method of a gain distribution insensitive to mode matching. One of the advantages of this method is a fact that it provides real dimensions of the gain distribution. Knowledge about it allows one to find the optimum spatial mode matching to maximize the output energy.

We analyzed the transient response characteristics of Yb:YAG thin disk in to clarify the experimentally obtained advantages of pulsed pumping in 1-kHz repetition rate reported in ref. 2. We applied commercial 2D FEA software which can calculate transient response of thermal effects. The temperature distributions of thin disk in both the CW power of 125-W and the average power of pulsed 125-W have been calculated. Even the net heat power were same in both CW and pulsed pumping, the temperature distribution was lower in pulsed pumping which can provide higher O-O efficiency and smaller beam distortion. The time evolution of OPD in the pulsed pumping has been analyzed, too.

Nowadays, more powerful and challenging laser systems are built to meet the need of evolving technology. In this context, the aim of the HiLASE project [1] is to develop a multi-joule picosecond laser system working in kHz repetition rate regime. The outputs of the project will provide not only unique source for both scientific and industrial applications, but also great challenge for supporting technologies. The key parameter of all optical components in laser and beam delivery structure is the laser induced damage threshold, which limits intensities manageable by the system. The following paper presents results of LIDT test of mirrors intended to use in laser system built within the HiLASE project as well as advanced LIDT test station desi gn, which will use HiLASE laser as source. Keywords: LIDT, ISO 21254, laser, laser damage 1. INTRODUCTION Pulsed lasers operating in picosecond an d femtosecond regime have evolved rapidly in the past years, mainly regarding the intensity and repetition rate. Purely scientific setups, designed for fundamental research, have extended into application in many fields, as metrology, machining or medical devices. Apparent achievements in laser physics and progress in engineering and material science gave a rise to cutting-edge projects, as ELI-Beamlines [2] or PETAL. Utilizing of gathered knowledge and state-of-the-art then allows construction of compact devices in applied research, which can reach substantial output powers and energy densitie s. Parallel application projects, as for example HiLASE, has important role in providing engineering background for the fundamental research as well as transfer scie ntific results into application level. For this purpose, HiLASE is developing three kW class thin-disk laser lines, delivering 1-2 picosecond pulses of energy up to 1 Joule with repetition rate of 1 kHz and beam diameter 15 mm, and one multislab system delivering 2-10 nanosecond pulses of energy 100 Joules with repetition rate up to 10 Hz and beam diameter 45 mm. Due to the fast evolution of laser systems and consequent increase of the output powers, requirements on laser system components are now more demanding. Research and development of novel materials and novel measurement methods for optical coatings, mirrors, crystals and other components is highly desirable. Output parameters described above can be unattainable by common industrial lasers. Consequently, there is a significant demand for the beam time at the high power, high repetition rate devices, both fr om research laboratories and industrial companies. However, such lasers are in majority designed for scientific experiments, requiring complicated set-up to fit particular workplace, than for "test-and-go" approach. One of the main goals of application program in HiLASE project will be to remove this deficit and provide valuable workplaces allowing fast set-up and exposure variety of samples. In particular, design of highly advanced station for measuring laser induced damage threshold, utilizing HiLASE lasers, will be described further. This station will be in compliance with series of ISO 21254 standards, fully computer controlled and offering beams with parameters described in previous paragraph. Station design will employ also online detecting devices, allowing precise control of damage threshold measurement as well as observation of non-damaging effects occurring under the high-energy beams. Further, particular measurements of mirrors intended for beam delivery system in HiLASE will be presented. These measurements are focused on LIDT and effects occurred after 10

The work described here is based on the optical design, simulation and on-going implementation of a pulsed (Q-switch) Yb 3+ -doped, 1-um diffraction-limited fibre laser with pico-second, 10 micro-Joule-range energy pulses for producing the right energy pulses which could be of benefit for patients who suffer chronic headache, photophobia, and even nausea which could is sometimes triggered by a series of factors. The specific therapeutic effect known as acupunctural analgesia is the main objective of this medium-term project. It is a simple design on which commercially available software was employed for laser cavity design. Monte Carlo technique for skin light-transport, thermal diffusion and the possible thermal de-naturalization optical study and prediction will also be included in the presentation. Full optical characterization will be included and a complete set of recent results on the laser-skin interaction and the so called moxi-bustion from the laser design will be extensively described.

A few Petawatt lasers are operative now in the world and a few more are under construction in several places. One of them is under construction at Salamanca, Spain, in the framework of a Consortium between the Central Government of Spain, the regional Government of Castilla y Leon and the University of Salamanca. The Spanish PW will reach that extreme power with 30 Joule / 30 femtosecond pulses, using Ti:Sapphire CPA technology and delivering one shot per second. The Salamanca laser will allow synchronized pump/probe experiments with a unique 200 TW probe sharing the same front end. The laser is now under construction and full operation is expected in less than two years. That laser will be a user facility opened to the national and the international scientific community. To understand the meaning of such a system, a review of the technology and its extreme applications in the foreseen range of powers and intensities is presented.

A phenomenological approach is herein followed to describe several superimposed effects occurring within the structure of microswitch for radio frequency application (RF-MEMS). This device is operated via a nonlinear electromechanical action imposed by applied voltage. Unfortunately, it is usually affected by residual stress, after microfabrication, therefore axial and flexural behaviors are coupled. This coupling increases actuation voltage to achieve the so-called "pull-in" condition. Moreover, temperature may strongly affect strain and stress distributions, respectively. Environmental temperature, internal dissipation of material, thermo-elastic and Joule effects play different roles on the microswitch flexural displacement. Sometimes buckling phenomenon evenly occurs. Finally, if stress concentration on microbeam cross section is sufficiently large, plastic behavior may arise. All those aspects make difficult an effective computation of pull-in voltage, understanding actual behavior of microsystem, particularly when several loading cycles are applied, and predicting its life. Analysis, experiments and numerical methods are herein applied to test case suggested by industry to investigate step by step the microswitch operation. Effects on pull-in and switch contact are investigated. Multiple electro-thermo-mechanical coupling is finally modeled to have a preliminary and comprehensive description of microswitch behavior and of its structural reliability.

This paper describes the synchronisation system under development on the Laser Megajoule (LMJ) in order to synchronize the laser quads on the target to better than 40ps rms. Our architecture is based on a Timing System (TS) which delivers trigger signals with jitter down to 15ps rms coupled with an ultra precision timing system with 5ps rms jitter. In addition to TS, a sensor placed at the target chamber center measures the arrival times of the 3ω nano joule laser pulses generated by front end shots.

X-ray imaging technology is highly developed to meet the needs of high-energy physics and diagnostics of inertial confinement fusion. In this paper, we describe the design of a non coplanar toroidal mirrors microscope. It consists of three off-axis revolution concave toroidal mirrors working at grazing incidence. Non-periodic W/SiC multilayer coatings have been deposited on each mirror, in order to increase until 10 keV the bandpass of reflectivity of the microscope. These super mirrors have been designed to work at 0.6° grazing incidence angle and display a reflectivity better than 40% in the entire energy range 2-10 keV. Concerning the imaging performances, we have almost achieved 5 μm of spatial resolution in a field of 500 μm. Regarding to these results, this prototype of microscope, the so-called "Plasma Imageur X pour les Experiences Laser Mega Joule" (PIXEL), will be used for 2D spatial and 1D time resolved imaging of dense plasmas produced during inertial confinement fusion experiments at the future Laser Mega Joule French facility (LMJ).

The stability of the carbon nanotube subjected to Joule's heating is investigated by means of classic molecular dynamics simulation. The systems without side heat sink and with side heat sunk were considered. The later consisted of a nanotube loosely incorporated into diamond nanocristal. The results of the molecular dynamics simulation have shown that a carbon nanotube is able to conserve its regular structure under high electric power dissipation rates (up to 10 mkW for a nanotube of the length of 4 nm). The efficiency of heat sink can be increased by means of diamond matrix.

In the past decade, the Thin Disk laser design was very successful as a high power laser design for cw lasers with good beam quality and high efficiency. Several numerical models show that the actually demonstrated output powers are far below the scaling limits due to amplified spontaneous emission (ASE). Also pulsed lasers based on Thin Disk amplifiers achieved comparable high average power, but only with medium pulse energies (about 100 mJ). Numerical models show that ASE effects limit the possible pulse energy to values of a few Joule, using the typical high power cw Thin Disk laser design. To evaluate designs for higher pulse energies a time resolved numerical model of pump absorption and ASE was developed and combined with a model of pulse amplification. The evaluation is focused on quasi-cw pumped pulse amplifiers. It includes the analysis of temperature, stress, deformation and thermal lensing, using finite element methods. This numerical model is used to develop thin disk designs for high output energies.

The development of XeF(C-A) lasers by optical pumping in Northwest Institute of Nuclear Technology during recent 10 years is described in this paper. A joule level of XeF(C-A) laser optically pumped by a sectioned surface discharge was studied with the total efficiency of 0.1%. A more efficient XeF(C-A) laser was developed with the maximum outpup energy of 18.6 joules by two-side optically pumping and repetition mode operating.

Joule heated resistive emitter arrays are presently limited to pixel temperatures on the order of 1000 K. A phase 2 SBIR program is underway to develop material sets with the goal of increasing the operating temperatures of these arrays by up to a factor of 3. Preliminary work indicates that transition metal oxides and carbides are the most promising materials for 3000 K pixel temperatures. An overview of the project and current status is presented. Thin films will be deposited by numerous vendors using a variety of techniques, and annealed at ultra-high temperatures in vacuum to select the most stable materials. Test emitter pixel arrays will be fabricated and tested.

Theoretical simulation and experimental studies of optical limiting characteristics in thin stimulated Brillouin scattering (SBS) cell of CCl4 have been given. Temporal coupling equations of stimulated Brillouin scattering initiated by thermally excited acoustic wave's field-uniformity existing in thin SBS cell are used. In order to reveal optical limiting performance, several limiting parameters are discussed. The dependences of SBS limiting parameters on pump energy and length of thin SBS cell are studied numerically firstly. The results showed that non-focusing thin SBS cell can limit energy as high as several Joule magnitudes. Power and output energy limiting behaviors have been studied experimentally in our experimental regime. For 1cm thin cell, when laser pulses transmit through the SBS medium CCl4; the output power and energy are limited fainlyt: the output peak power is limited and pulse narrowed without evident power limiting in the following edge; as for 2cm and 4cm cell, both show evident power limiting "step" and energy limiting characteristics, when pump energy increases from 5mJ to 100mJ, the output energy is limited under 20mJ for 2cm SBS cell and 12mJ for 4 cm SBS cell, which are quite agree with theoretical calculations in low input energy level.© (2005) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The Ligne d’Integration Laser (LIL) is a prototype installation at scale 1 of one of the 30 lasers of future Laser Mega Joule. It is intended to validate technological choices made for LMJ and to prepare its exploitation. The facility will contain nearly 10.000 optics and over 4000 m 2 of mirrors. Cleanliness will be an essential matter in the facility since contamination of optics can reduce their laser damage threshold. Hence, airborne molecular contamination (AMC) has been sampled near optics in strategic places of the LIL. These samplings have shown high levels of organic compounds, notably in the amplifying section, which is expected to be th e most sensitive part in the LIL. Suspecting a local source of contamination, outgassing tests of typical materials const ituting the amplifying section have been carried out. Among them, one sealing material has been identified as a source of organic contamination near the optics. Effects of this pollution have been investigated by a measurement of laser damage threshold after intentional contamination of optics. This work shows the complexity of the outgassing contamination issue, since several steps are necessary to evaluate the effects of this contamination on optical surfaces: air samplings, identification of sources, outgassing tests, intentional contamination of optics and finally measurement of laser damage threshold.

Laser system generating optical pulses with the duration of subnanosecond range is considered in this paper. Optical neodymium glass generator (GOS-1001) is used as the basis installation. Such choice lets us to increase the total energy of the laser generation pulse up to 9 joule. Sources of the generation energy restriction are also considered. Longitudinal photorefractive effect in the feedback coupling DKDP element is mentioned as one of them. Conclusions on the restriction of the application field of such medium for the high-energy lasers dynamics control are carried out.

Sonic, or thermosonic nondestructive testing, which is based on the vibrothermography method introduced in the late 1970’s, has attracted a great deal of recent interest as a means for detection of cracks that were previously considered to be undetectable using thermographic inspection methods. Excitation of a solid sample with bursts of high-energy (500 - 3000 Joule), low-frequency (10 - 50 kHz) acoustic energy has been demonstrated to be effective in generating transient localized heating at crack sites, making them detectable by an infrared camera. Despite the apparent simplicity of the scheme, there are a number of experimental considerations that can complicate, or in some cases even prevent, the implementation of vibrothermography-based inspection. Factors including acoustic horn location, horn-crack proximity, horn-sample coupling, and effective detection range all significantly affect the degree of excitation (or whether any excitation occurs at all) that occurs at a crack site for a given energy input. In cases where the experimental objective is precise measurement of crack length, the method used to visualize the data from the IR camera and its optic must also be taken into consideration.

The use of the infrared thermography techniques is progressively showing as an important tool in the research of very different thermal applications, in this case air conditioning systems. The Instituto de Ingenieria Energetica de la Universidad Politecnica de Valencia has developed a Joule Project, financed by the European Community for the Study and Characterization of propane heat pumps, adapted to the use in the South European countries. The substitution of the fluorocarboned refrigerants by natural fluids as propane is the main objective of this project. With the study, important efficiency improvements have been obtained, in relation with the use of the classical refrigerants, for both summer and winter conditions. The use of the thermography in this project has been quite useful in the achievement of several important tasks as the study of the compressor start up process, as it is described in the paper.

We model recent experiments done using the COMET laser at Lawrence Livermore National Laboratory to illuminate slab targets of Pd up to 1.25 cm long with a two joule, 600 ps prepulse followed 700 psec later by a six joule, six psec drive pulse. The experiments measure the two-dimensional near-field and far-field laser patterns for the 14.7 nm Ni-like Pd x-ray laser line. The experiments are modeled using the LASNEX code to calculate the hydrodynamic evolution of the plasma and provide the temperatures and densities to the CRETIN code, which then does the kinetics calculations to determine the gain. Using a ray tracing code to simulate the near and far-field output the simulations are then compared with experiments. In addition we model recent experiments that used a streak camera to measure the time duration of the Pd X-ray laser when pumped with a constant energy short pulse with different time durations that ranged from 0.5 to 27 ps.

Uniform current spreading is desirable for both light emitting diodes (LEDs) performance and reliability. It enhances optical efficiency because the joule losses due to current crowding in some parts of the die would be eliminated. The LED design for optimal light extraction and uniform current spreading is therefore a necessity. In this paper we report on preliminary current spreading results obtained from circuit simulation, using Pspice and Aimspice, for LED designs with and without an n-metal ring as well as the epi-up and flip chip LEDs. For the epi-up, both the lateral and vertical resistances of the transparent metals were taken into account. Whereas in the flip chip, the lateral resistance was negligibly small thus only the vertical component contributed to the total p-lump resistance. The n-lateral resistance in the active mesa was critical to uniform current spreading. It was found that the lower the n-lateral resistance, the more uniform the current spreads and flows through the active region. In both the epi-up and flip-chip structures, the contact resistance of the p-metal (including the thin Ni/Au transparent metal) dominated the total p-lump resistance. The larger this value, with fixed n-layer lateral resistance, the more uniform the current spreads in the device. However, high p-contact resistance is not desirable as it reduces the overall efficiency of the device due to excessive heating and increased leakage current. Therefore, for uniform current spreading, the n-lateral resistance should be made small while maintaining an optimum p-lump resistance to achieve a high efficiency.

A new Compton backscatter imaging (CBI) technique, described as lateral migration radiography (LMR), has been developed and applied successfully to two difficult diagnostic problems: Detection of buried, plastic landmines, and detection of material flaws which lie close to, and parallel to, a surface, the method is based on image contrast generated by alteration of photon lateral migration relative to the illuminating beam direction. It is extraordinarily sensitive to density and/or atomic number variation along the photon lateral-direction travel paths. In LMR, relevant information-carrying photon detection efficiencies are two to three orders-of-magnitude greater than other CBI techniques such that the electric energy requirement for x-ray generation is only about one joule per acquired image pixel. The resulting small product of pixel illumination dwell time and x-ray generator electric power implies that current, easily accessible technology can be used to fabricate LMR systems with practical usage protocols. Three have been designed and built at the University of Florida: A laboratory device for perfecting buried landmine acquisition; a mobile system for field-demonstrating landmine detection; and, a laboratory system for detection of material defects in small structural parts. The LMR images, acquired in a laboratory landmine detection setting, are so definitive that identification of the mine-type, as well as presence, can be often accomplished. Results of a field test are near-perfect, both in determining buried landmine presence and in lack of false positive response. Images acquired in material flaw detection indicate ability to detect lateral cracks or delaminations with thickness less than 100 microns, as well as corrosion on surfaces between layers of structural sheets. These applications provide evidence of the viability of a new, one-sided x-ray radiography technique which images hidden structures of objects which have here-to-fore been difficult, or impossible, to detect with practical image aquisition times.

This paper reports on a space-qualified cooling system for submillimeter SIS mixer receiver (SIS: superconductor- insulator-superconductor). Designed cooling capacity of the system is 20 mW at 4.5 K, 200 mW at 20 K, and 1000 mW at 100 K. The combination of two-stage Stirling cooler and Joule- Thomson one has demonstrated the capacity with a power consumption of less than 300 W, including losses of drive electronics. The cryostat has a thermal insulation structure of S2-GFRP straps to fasten its 100 K stage. 20 K stage of the cryostat is held with GFRP pipes on the 100 K stage, while 4 K stage is supported with CFRP pipes on the 20 K stage. The cooling system accommodates two SIS mixers at 4.5 K, two IF amplifiers at 20 K, and two more IF amplifiers at 100 K. The mass of the cooling system is 40 kg for the mechanical cooler itself, 26 kg for the cryostat, and 24 kg for the driver electronics. The system has been developed for a 640 GHz receiver for an atmospheric limb-emission sounder SMILES, which is to be aboard the International Space Station in 2005. The engineering model of the system has been built and tested successfully.

Magnetoelasticity encompasses a wide range of phenomena including, but not limited to, volume and Joule magnetostriction, the Villari effect, direct and inverse Wiedemann effects, the (Delta) E effect, and a magnetoelastic contribution to the apparent magnetic anisotropy. These effects are conveniently codified in a magnetoelastic energy density which, together with the magnetic (including exchange) and elastic energy densities, provides a consistent thermodynamic description of magnetoelasticity. In this review I shall briefly examine each of these effects and the corresponding terms of the energy density. This energy density is described by a collection of material constants which, in principle, are derivable from theory. The physical coordinates which are maintained constant in any experiment dictate the relevant combination of these material constants which is ultimately observed. Static and dynamic measurements are generally carried out with different constraints and, not surprisingly, these experiments measure different combinations of material parameters. For example, the highly magnetostrictive smart material Terfenol-D (Dy 0.73 Tb 0.27 Fe 1.95 ) has a static magnetic anisotropy which is markedly different from the anisotropy exhibited in a dynamic measurement.

The purpose of this paper is to present a grating-assisted nonlinear limiting method based on the principle of index mismatching and grating diffraction. In addition, various nonlinear organic materials have been tested in the optical limiting system. A few examples with experimental results are presented. Using a YAG nanosecond pulse laser at 532 nm as a simulated threat laser source, we tested the optical limiting characteristics of the methyl-red doped nematic liquid crystal films. In the meantime, we observed some quite interesting optical phenomena, such as self-defocusing diffraction rings, dark spots in the far-field behind the cell. Our experimental results presented in the paper show that the methyl-red doped nematic liquid crystal films posses a good optical limiting performance. When the input energy focused on the cell increases from approximately zero micro Joule to approximately 200 micro Joule, the output energy on the far-field exit plane is kept under 1 micro Joule. We will describe a completed optical limiting system with Q-switched frequency-doubled 12- ns Nd:YAG laser, dual-channel detectors, and computer processing units based on Lab-view software and its design considerations.

Studies of the lasing characteristics of three pyrromethene laser dyes (pyrromethene 567, 580 and 597) in modified polymethyl methacrylate have been carried out under flashlamp excitation. Comparison are made of the optical qualities, output energy and other lasing properties. Output energies of over 1 Joule per shot have been achieved with an electrical stored energy to output energy efficiency of almost 0.5%.

Theoretical and numerical analysis of energetic characteristics of gasdynamic lasers on active media containing diatomic metastable molecules H2, D2, N2 and halogen molecules was carried out. It was estimated that the most promising from the point of view of receiving the highest specific radiation energy and conversion efficiency of vibrational energy are mixtures D2-DCl, D2-HBr, N2-DCl, N2-DJ, N2-DBr, D2-HJ and H2-HCl. At thermal excitation they allow to achieve efficiency from 1% to 4% and at electrodischarge excitation from 10% to 25%, the specific radiation energy reaching 60 - 300 Joule/g.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Very high damage threshold Haihia Silica mirror coating have been developed successfully thanks to a clear understanding of the main limitations of the available mirrors. Coating with a 3ns pulse width threshold above 100J/cm2are reported. These coatings proved to be much more resistant than very high quality bare silica substrate tested the sameway. The limitation ofthese coatings is still extrinsic. The potential of this technology for large size high damage mirrorsfor fusion laser application is discussed.Keywords: Coating, Laser Damage, Mirror, Hathia, Silica, Fusion laser1.I1MTRODUCTIONThe development of coating must parallel the development of laser materials in order to improve laser technology. Therequest of high damage threshold large surface components for the new laser fusion like LMJ in France or NIF in USAtriggers a lot of efforts to reach the tremendously high specification requested. This paper focuses on the point reached atLETI concerning high performance omega coatings. These coatings, either mirrors or polarizers, have been developedwith the aim of reaching the highest possible damage threshold in order to have a significant production yield of largeoptics. In the first part of the paper, we describe our current understanding of laser induced mirror damage at 1.O6m.This understanding allows us to develop a strategy for coating improvement. This strategy is presented in part 3. The mainresults concerning the mirrors are presented in part four.

A high energy flashlamp pumped Ti:sapphire laser has been developed for the pumping source of Yb:glass chirped pulse amplification. The free running oscillator generates 12 Joule/pulse at 793 nm at 1 Hz repetition. The output energy of 6 Joule/pulse at 920 nm has been obtained.

We present the design of a diode-pumped Neodymium glass amplifier delivering one Joule output pulses with a 1 Hz to 10 Hz repetition rate, good stability due to diode pumping and good beam properties due to the uniformity of energy deposition. The amplifier architecture is simple and rugged. We show that, when an amplifier with an amplification section of about 1 cm3 is considered, 5 J useful stored energy yields an output pulse with a more than 1 J energy and with low spatial and temporal distortions.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

We developed a number of active devices for use in the regenerative amplifier, which is one of the specific sub- assemblies of the preamplifying section in the french L.M.J. design. The first one is a modular-square-diode pumped laser head, which provides 0.65 Joules pumping energy at 800 nm into a 4 mm side Nd3+:phosphate glass, in the form of a close coupling-uniform-configuration. Our original side pumping scheme makes use of symmetric diode stacks and optimized rod holders with a thermal conductivity. Some heat is waste in the volume of glass, as a result of the pumping process, and it is efficiently--since very closely--removed by the latter holders. A (pi) /2 rotation of one pumping section with respect to the next one allows uniform pumping and thermal conduction together with birefringence reduction. No water is required. A complete 3D thermal model is developed, in order to describe temperature and stress distributions, inside the laser head and glass rod. Peak stress values in glass at F equals 10 Hz, with flexible rod holders including Indium parts, equal 5.8 Mpa when the mean thermal power is 22 watts. Preliminary laser tests are experienced at 10 Hz with two similar laser heads around a square Nd3+:LHG750 glass rod. With 1.3 Joule pump energy at 400 microsecond(s) pumping duration, the assembly is placed inside a Qswitched stable, multimode plano-concave, resonator. The output energy is 40 mJ, within 80 ns fwhm pulses.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.