Laser Target Design Research Articles

Design and Development of a Laser Warning Sensor Prototype for Airborne Application


 
 
 Due to recent developments in high-energy laser systems, the laser is becoming one of the most potential choices in battlefield applications. Laser of a laser range finder used to find target distance may be of nanosecond pulse width and a single pulse may be sufficient to gather the instantaneous range information. A laser target designator is a similar laser with higher energy and with programmable pulse repetition frequencies5,7. Detection of such a specific battlefield laser radiation along with recognizing friend or foe is required for countermeasures. Designing a laser detection system that is capable of detecting such low-power level laser pulses of nanosecond pulse width at a long distance is a critical design and a challenging task. Again detecting a wide wavelength band that can start from 500 nm to around 1700 nm range using a single detector or device is also a challenging task. In this work, a sensor system is being designed and a prototype is developed to cover such a long band detection using a single detector for high-energy lasers. Also, in addition to detecting hostile code, the direction of an incoming laser beam is tried to incorporate into this sensor. The sensor can be utilized to detect unknown or non-friendly laser illumination from within a specific angular cone and distance.
 
 

Shielded radiography with gamma rays from laser-accelerated electrons in a self-trapping regime

Very efficient generation of a high-charge electron beam by a laser pulse propagating in a self-trapping mode in near-critical density plasma makes it possible to produce a high yield of gamma rays for radiography of samples located deep in a dense medium. The three-dimensional particle-in-cell and Monte Carlo simulations performed with end-to-end modeling from laser–plasma interaction to the final gamma-imaging of deeply shielded objects located at distances up to several meters clearly demonstrate the promise of laser pulses of several hundred TW for single-shot radiography by using a high-performance scheme of electron acceleration in the laser pulse self-trapping regime. This is illustrated by two examples with the same laser–target design used for a bremsstrahlung gamma source and an all-optical nonlinear inverse Compton source.

Laser-triggered stochastic volumetric heating of sub-microwire array target

The interaction of an ultrashort laser pulse of moderate intensity ( ≳ 1018 W/cm2) with an innovative high-average-density target consisting of numerous sub-microwires was examined using 3D PIC simulations. We geometrically optimize the target to increase the absorption of laser light and energy (temperature) and the number of hot electrons. To explain the production of super-ponderomotive electrons (with energies significantly exceeding the ponderomotive energy), we use the test particle approach and stochastic dynamics methods to study the electron dynamics in a complicated EM field consisting of incident and reflected laser waves, the Coulomb field of charge separation at wire–vacuum interfaces, and the quasistatic magnetic field. The research demonstrates the stochastic nature of high-energy electron production in such a complicated EM field using Lyapunov exponent analysis. We describe the practical fabrication of such targets in the context of possible experiments. The considered laser–target design has a potential for use in compact laser-based neutron, x-ray sources.

Efficient Embedded Hardware Architecture for Stabilised Tracking Sighting System of Armoured Fighting Vehicles

A line-of-sight stabilised sighting system, capable of target tracking and video stabilisation is a prime requirement of any armoured fighting tank vehicle for military surveillance and weapon firing. Typically, such sighting systems have three prime electro-optical sensors i.e. day camera for viewing in day conditions, thermal camera for night viewing and eye-safe laser range finder for obtaining the target range. For laser guided missile firing, additional laser target designator may be a part of sighting system. This sighting system provides necessary parameters for the fire control computer to compute ballistic offsets to fire conventional ammunition or fire missile. System demands simultaneous interactions with electro-optical sensors, servo sensors, actuators, multi-function display for man-machine interface, fire control computer, logic controller and other sub-systems of tank. Therefore, a complex embedded electronics hardware is needed to respond in real time for such system. An efficient electronics embedded hardware architecture is presented here for the development of this type of sighting system. This hardware has been developed around SHARC 21369 processor and FPGA. A performance evaluation scheme is also presented for this sighting system based on the developed hardware.

A quantitative method for calculating irradiation area of laser target designator

In laser-guided bomb attacking process, the target indication from the laser target designator is the premise for the bomb to hit the target accurately. Considering the lack of quantitative study of the irradiation area of the laser target designator, this paper, based on the existing aircraft motion model and the laser transmission model, uses two aircraft as respectively the carrier of the laser-guided bomb and the carrier of the laser designator and proposes a method to calculate the global irradiation area of the airborne laser designator. By using the proposed algorithm, the global irradiation area when attacking a large flat target or a large spherical target is simulated respectively. Finally, according to the simulation results, the influences of different factors on the shapes of the irradiation area are discussed in detail.

用于目标指示器的激光器研究进展

用于目标指示器的激光器研究进展

Design and realization of a compact and multi-purpose passively Q-switched ND:YAG laser system

In this paper, a passively Q-switched pulsed Nd:YAG laser system is designed and realized for defense applications. Our previously published generalized mathematical model for passively Q-switched lasers is used to help extract the design parameters of the proposed Q-switched Nd:YAG laser system. The proposed laser system is a simple and compact laser source which can be employed for many applications. The laser system operates at 1064 nm, its free running output energy is 150 mJ, while its Q-switched laser output contains a train of pulses with pulse width varies from 47 nm to 85 nm and with maximum measured total output energy of 52.4 mJ. The output pulse series contains 6 pulses with maximum peak power of 468 kW, while the minimum obtained peak power is 18.8 kW. The total duration of the Q-switched output pulse series is about 150 μs. This system can be used in many applications such as Laser-induced breakdown spectroscopy (LIBS), LIDAR, laser target designation (LTD), range finding, and some medical applications.

Two-dimensional turning of thermal flux from normal to lateral propagation in thin metal film irradiated by femtosecond laser pulse

There are various geometrical variants of laser illumination and target design. Important direction of investigations is connected with tightly focused action (spot size may be less than micron) onto a thin metal film: thickness of a film is just few skin-layer depths. Duration of a pulse is τL ∼ 0.1 ps. In these conditions energy absorbed in a skin layer first propagates normally to a surface: gradient ∂Te/∂x dominates, here and below x and y are normal and lateral directions. This process in 1–2 ps homogenizes electron temperature Te along thickness of a film. We consider conditions when a film or is supported by weakly conducting substrate, or is free standing. Therefore all absorbed energy is confined inside the film. At the next stage the internal energy begin to flow along the lateral direction—thus direction of energy expansion is changed from x to y because of the heat non-penetrating boundary condition imposed on the rear-side of the film. At the short two-temperature stage of lateral expansion the thermal conductivity κ is high. After that electron and ion temperatures equilibrates and later on the heat propagates with usual value of κ. Lateral expansion cools down the hot spot on long time scales and finally the molten spot recrystallizes. Two-dimensional approach allows us to consider all these stages from propagation in x direction (normal to a film) to propagation in y direction (along a film).

장거리 레이저 거리측정기 및 레이저 표적지시기 성능 평가를 위한 모사기 구현

In this paper, we propose a signal processing board of an optical delay simulator for evaluating a long-range laser range finder and a laser target designator . We improved the accuracy by applying the clock multiplication and the correction of error gradient. To evaluate the performance of the proposed method, we implemented a prototype board and performed experiments. As a result, we implemented the optical delay simulator with resolution less than 0.7m in measuring distance 60km and a standard deviation of 0.041m . The PRF code detection logic and generation logic have a stability less than 0.03% and 0.08% compared to the NATO standard, respectively.

Compact, diode-pumped, solid-state lasers for next generation defence and security sensors

Low-cost semiconductor laser diode pump sources have made a dramatic impact in sectors such as advanced manufacturing. They are now disrupting other sectors, such as defence and security (D&S), where Thales UK is a manufacturer of sensor systems for application on land, sea, air and man portable. In this talk, we will first give an overview of the market trends and challenges in the D&S sector. Then we will illustrate how low cost pump diodes are enabling new directions in D&S sensors, by describing two diode pumped, solid- state laser products currently under development at Thales UK. The first is a new generation of Laser Target Designators (LTD) that are used to identify targets for the secure guiding of munitions. Current systems are bulky, expensive and require large battery packs to operate. The advent of low cost diode technology, merged with our novel solid-state laser design, has created a designator that will be the smallest, lowest cost, STANAG compatible laser designator on the market. The LTD delivers greater that 50mJ per pulse up to 20Hz, and has compact dimensions of 125×70×55mm. Secondly, we describe an ultra-compact, eye-safe, solid-state laser rangefinder (LRF) with reduced size, weight and power consumption compared to existing products. The LRF measures 100×55×34mm, weighs 200g, and can range to greater than 10km with a single laser shot and at a reprate of 1Hz. This also leverages off advances in laser pump diodes, but also utilises low cost, high reliability, packaging technology commonly found in the telecoms sector. As is common in the D&S sector, the products are designed to work in extreme environments, such as wide temperature range (-40 to +71°C) and high levels of shock and vibration. These disruptive products enable next- generation laser sensors such as rangefinders, target designators and active illuminated imagers.

Characterization and Modulation of High Power Diode Laser Module as a Target Designator

In a laser tracking system (LTS) the objective is to track the reflected or scattered modulated laser beam. A four-quadrant is essentially required to center and align the optical axis of the quad detector (QD) with the main laser beam. This paper shows an experimental characterization of a high power diode laser module as a laser target designator source (LTD) used in the tracking system. It includes the (I-V) characteristic, output optical power verses driving electrical currents, slope efficiency, the laser beam profile and the wavelength dependence of temperature. Like all practical designation and tracking system, a modulation of a high power laser source with pulse repetition frequencies (PRF) mode of operation is required. So the effect of different frequencies on both of the pulse to pulse stability and wavelength stability are measured, analyzed and investigated.

Detection and analysis on versatile coding strategies of high frequency active Q-switched Nd:YVO4 laser for irradiance of different targets

Abstract We report an active Q-switching with different coded schemes generated in the high power diode end pumped Nd:YVO 4 laser (DEPSS) using two different techniques of special combination of optical choppers and acousto-optic modulator (AOM) at higher repetition rates of 100 kHz for the first time to the best of our knowledge in any practical laser target designation (LTD) systems. The highest peak power of 95.4 kW with the lowest pulse repetition frequency of 222 Hz and pulse width of 46 ns at FWHM with the pulse-to-pulse stability of ~95% was measured at certain regime of operation. Special modulation and coding of high stable, high peak power Nd:YVO 4 laser pulses at 1064 nm using the combination of different optical chopper blades were achieved. A high peak power of more than 4.84 kW with the shortest pulse width of 25 ns at FWHM has been obtained using an acousto-optic modulator (AOM) as an active Q-switched. The pulse-to-pulse stability was measured and improved to be ~97% at high repetition rate ranges from 10 kHz to 100 kHz. The correlation between the coded laser irradiation (transmitted) and the scattered (received) laser signals for three different targets materials of sand, wood and metal using this laser designation system are examined and discussed.

Fast ignition with laser-driven proton and ion beams

Fusion fast ignition (FI) initiated by a laser-driven particle beam promises a path to high-yield and high-gain for inertial fusion energy. FI can readily leverage the proven capability of inertial confinement fusion (ICF) drivers, such as the National Ignition Facility, to assemble DT fusion fuel at the relevant high densities. FI provides a truly alternate route to ignition, independent of the difficulties with achieving the ignition hot spot in conventional ICF. FI by laser-driven ion beams provides attractive alternatives that sidestep the present difficulties with laser-driven electron-beam FI, while leveraging the extensive recent progress in generating ion beams with high-power density on existing laser facilities. Whichever the ion species, the ignition requirements are similar: delivering a power density ≈1022 W cm−3 (∼10 kJ in ≈20 ps within a volume of linear dimension ≈20 µm), to the DT fuel compressed to ∼400 g cm−3 with areal density ∼2 g cm−2. High-current, laser-driven beams of many ion species are promising candidates to deliver such high-power densities. The reason is that high energy, high-power laser drivers can deliver high-power fluxes that can efficiently make ion beams that are born neutralized in ∼fs–ps timescales, making them immune to the charge and current limits of conventional beams. In summary, we find that there are many possible paths to success with FI based on laser-driven ion beams. Although many ion species could be used for ignition, we concentrate here on either protons or C ions, which are technologically convenient species. We review the work to date on FI design studies with those species. We also review the tremendous recent progress in discovering, characterizing and developing many ion-acceleration mechanisms relevant to FI. We also summarize key recent technological advances and methods underwriting that progress. Based on the design studies and on the increased understanding of the physics of laser-driven ion acceleration, we provide laser and ion-generation laser-target design points based on several distinct ion-acceleration mechanisms.

基于二阶振动系统响应模型的激光制导信号动态模拟

The process analysis of the two-order dynamic response of Laser Target Designators(LTD) and the aiming errors are introduced in the Air-borne platform LTD random position jittering simulation.The Gauss white noises and the filtered colored noises are used to simulate the dynamic statistical characters of LTD jittering facula's time-response position and diffuse reflected energy under the simplified model of targets,together with the test results of the two different kinds of materials.The analysis shows that the dynamic diffuse reflected energy is related to the movement between platform and targets,the target's surface diffuse reflection characters and surface reflection characters.The method and the results can be used in the dynamic simulation of LTD signals' atmosphere propagation and detection.

Influence of a density mismatch on TMPTMA shells nonconcentricity

AbstractSome laser target designs require low‐density organic foam shells to study fusion on the French high‐power laser laser mega joule. Low‐density trimethylolpropane trimethacrylate foam shells composed of C, H, and O, 2 mm diameter, 100‐μm wall thickness, and 250 mg cm−3 density are synthesized by a microencapsulation technique using a droplet generator. These shells have to reach a sphericity higher than 99.9% and a nonconcentricity (NC) lower than 1%. The wall thickness variation is one of the most difficult specifications to meet. An important factor in reducing this defect is the density matching between the three phases of the emulsion at polymerization temperature. The influence of a density mismatch between the internal water phase and the organic phase on the NC of TMPTMA foam shells was studied. The best NC results and yields of shells are obtained with a density gap between the internal water phase and the organic phase of 0.078 g cm−3 at 60°C, with an average NC around 2%. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

MO‐D‐BRD‐03: Laser‐Driven Targetry: The Road to Clinical Applications

Purpose: Significant efforts have been made through federal, industrial and institutional funding to develop cost‐effective alternatives to conventional accelerator‐based particle therapy. This presentation reviews the development of laser‐accelerated particle beams as an alternative to conventional accelerators for particle therapy. Method and Materials: Many institutions and research groups have focused on their research on the applications of laser‐accelerated proton and ion beams for medical applications, in particular for radiotherapy treatments. These include extensive investigations of optimal laser parameters and target designs to achieve therapeutic particle energies, compact particle selection and beam collimation designs for novel compact particle therapy systems, dose calculation and treatment optimization for laser‐accelerated proton beams, and system and shielding designs for clinical prototype machines. Fox Chase Cancer Center has established a laser‐ion acceleration facility that consists of a commercial 150 TW laser, custom‐made laser‐pulse compression and target chambers, particle selection and beam collimating devices, dosimetry monitoring systems and shielding constructions. Initial laser‐proton acceleration experiments were performed with thin aluminum and plastic foils as target materials. Particle‐in‐cell (PIC) simulations were carried out to investigate the optimal laser parameters and target configurations to facilitate laser‐proton acceleration and dosimetric studies. Results: The maximum proton energy achieved by laser acceleration was 58 MeV. Our initial testing with a 1018 W/cm2 laser intensity (at 20 TW) produced up to 4 MeV protons with a broad energy spectrum, which confirmed the scalability of laser intensity and maximum proton energy. A compact shielding designed was investigated using Monte Carlo simulations that allows for the installation of the particle therapy head on a small rotating gantry. Conclusion: Laser‐accelerated proton and ion beams have a great potential to replace conventional radiotherapy systems due to its compact design and cost‐effectiveness. Many technical and engineering issues must be solved before a clinical prototype can be built for radiotherapy applications.

Direct-drive laser target designs for sub-megajoule energies

New direct-drive laser target designs with KrF laser light take advantage of the shorter wavelength to lower the laser energy required for substantial gain (>30×) to sub-MJ level. These low laser-energy pellets are useful in systems that could form an intermediate step towards fusion energy, such as the proposed Fusion Test Facility [S. P. Obenschain et al., Phys. Plasmas 13, 056320 (2006)]. The short wavelength laser should allow higher intensity (and higher pressure) without increasing the risk of laser-plasma instabilities. The higher pressure in turn allows higher velocities to be achieved while keeping the low aspect ratios required for hydrodynamic stability. The canonical laser energy has been chosen to be 500kJ. A target design is presented with various laser pulse shapes and both 1D and 2D simulation results are shown. The sensitivity of these targets to both low-mode and high-mode perturbations is examined. The analysis and simulations in this paper indicate that significant gain (G=57) can be achieved for these targets even in the presence of hydrodynamic instabilities.

Sub-mega joule laser target designs for direct-drive ignition and moderate gains

We report here exploratory studies of direct-drive target designs that require substantially less than a mega joule of laser energy for ignition and moderate gains. The target physics advantages of the Krypton Fluoride laser are exploited to achieve increased implosion velocities that allow ignition and gain at reduced energy. Use of increased laser irradiance allows use of limited aspect ratio targets. The highest performing designs make use of a short spike prepulse to set up an adiabat that can be favourable to gain. These designs have application in reducing the driver size needed for experimental laser fusion facilities and may be applicable to the gains needed for the energy application.

TU‐FF‐A2‐05: A Laser System and Target Design for Proton Acceleration

Purpose: The interaction of powerful laser pulses with solid‐state targets has recently been demonstrated to produce beams of energetic protons. The generation and characterization of laser accelerated protons is nowadays one of the most rapidly developing fields in accelerator physics. On the application side, the development of a cost‐effective and energy efficient way of producing proton beams represents a major breakthrough in hadron therapy. In this work we present a detailed study of the requirements imposed on the laser system in order to achieve extremely high peak intensities, necessary for proton acceleration. Different target designs are experimentally investigated. Method and Materials: The laser system consists of a chain of commercial lasers and amplifiers, based on Titanium doped sapphire crystal as active medium, followed by a custom‐design power amplifier. The technique of chirped‐pulse amplification is employed as the most efficient amplification scheme for ultra‐short laser pulses developed to date. Sharp focusing is achieved by an off‐axis parabolic mirror designed for low losses and minimal aberrations. Frequency resolved optical gating measurements provide the complete laser pulse characterization. Results: After pulse compression in vacuum we achieved 40 fs pulse duration with 1.1 J in each pulse at 10 Hz repetition rate. Focused beam spot size of 8 μm has been accurately measured. We demonstrate capability of obtaining pulses with characteristics suitable for proton acceleration. All stages of the pulse generation, amplification, compression, and conditioning are discussed in detail in this study. Different regimes of acceleration are discussed along with experimental evidence for their realization. Conclusion: We present a detailed characterization of the current state of our laser system and a novel target chamber design. The implications for proton acceleration along with optimization strategies for enhanced proton yield and collimation are discussed as well.

Fuel Cell Systems for the American Warfighter

Power generation and energy storage devices are essential components of the operational capabilities of the modern U. S. military. They are paramount to the tactical performance of advanced electronic systems such as Night Vision Goggles, GPS systems, and laser target designators. The modern “digitized” U.S. military relies extensively on these electronic technologies and others as they are fully integrated into combat environments. However, the demand for these electronic systems, as well as new tactical capabilities, is outpacing the supply of available power and energy devices. Recent studies from Iraq show that standard military power and energy systems, such as generators and batteries, were in high demand but short supply, which often limited operational speed and capabilities. In an effort to improve upon existing military power generation and energy storage devices, the Army’s Research, Development, and Engineering Centers (RDECs) are evaluating innovative technologies such as fuel cells for military applications. A variety of programs at the U.S. ARMY Communications-Electronics Research, Development, and Engineering Center (CERDEC) Fuel Cell lab are serving to fill the power and energy gap for soldier-based platforms. CERDEC serves as a test, evaluation, and program management center focused on transitioning integrated systems from the labs to the users. CERDEC has adopted a “systems of systems” approach to the development and testing of military fuel cell units and strives to develop completely packaged systems in order to rapidly transition fuel cell technology into the field. This paper will address current Army Communications-Electronics Research Development Engineering Center (CERDEC) fuel cell technology programs and their adaptation into military environments.