Design of ICF Target Positioning Robot System

A method based on binocular vision servoing for positioning of a diagnostic package in inertial confinement fusion (ICF) experiments is presented. The general diagnostic instrument manipulator will provide precision three dimension positioning and alignment-to-target capability in ICF experiments. In this work, we focus on the final precise automatic positioning with a binocular vision system. A three dimension image projection vector (IPV), which has an almost linear relationship with the target position in 3D space under the condition of weak perspective, is introduced to extract target position information from binocular image. The difference of the IPV between the current image and the desired image will be used as the input of servo controller. A differential motion model was found for the hybrid manipulator with three degrees of freedom. With this model and the said IPV, the servo strategy will be dramatically simplified compare with general image based visual servo in which the image Jacobian matrix needs estimated online. The experiment result implies that the locating accuracy of the manipulator is less than two pixels. This method can also be used in micromanipulation visual servo field.

Discussion on: “Comparison of Different Multivariable Control Design Methods Applied on Half Car Test Setup”

At present, parallel robots show a great progress in their development due to their behaviour in multiple applications. In this sense, the Stewart-Gough platform with proper mechanical adaptations could be used for a climbing parallel robot. A climbing parallel robot with 6 degrees of freedom has been proposed and analysed. Parallel robots have great advantages compared to serial robots with legs using as climbing robots. Some advantages can be cited as the high weight payload capacity, robustness, simplicity of its mechanical design, etc. However, some difficulties have to be resolve too as the adaptation to the structure meanwhile the robot accomplishes the task or the singularities that can be produced in the movement on the structure. In this paper several options of a climbing parallel robot based in the S-G platform have been presented and analysed. First of all, an initial prototype to climb along tubular structures as pipes or palm trunks has been shown. The main features of this robot are the pneumatic actuators and the external control loop that allows centring the robot to the tubular structure. Taking into account this first prototype, another parallel robot to resolve the problem of displacement and climbing along metallic structures has been presented. The main features of this robot are the electrical actuators and the clamping device developed with the purpose of reducing possible collisions between the movement ring of the robot and the environment. The results achieved with both prototypes show the validity of these platforms to undertake tasks in which are necessary to climb on. In short, this paper tries to show the big potential of using parallel robots as climbing robots. Also, we are working in introducing teleoperation techniques to manage these parallel robots. So, the robots will be controlled in a semi-automatic way when it displaces along the tubular or metallic structures.

In the laser inertial confinement fusion (ICF) experiment, the high accuracy target field coordinate system should be found to monitor the target by all kinds of physics diagnose instrument. Before the testing target is shot, the coordinate system should be transferred to the testing target, and recurrent the coordinate system before each shooting. In order to solve this problem, two set microscope optics vision instruments are designed which has autocollimating and target position monitoring functions, and its working distance is 3.8 meters，and its optic resolution is 8 micron. Firstly, the optical coordinate axis of the two instruments is adjusted orthogonally by each other, then the ICF range coordinate is transferred to a testing target by a sensor, and ensure testing target located at the center of ICF range coordinate. The instrument has already been used in Shen Guang III device, and also can be used for object monitoring and tracing in a kind of field.

Summary form only given, as follows. The Z machine at Sandia National Laboratories is a z-pinch facility capable of producing a 1 MJ, 200 eV radiation source. At present, this source is being investigated as a potential driver for inertial confinement fusion (ICF) experiments. For optimum ICF capsule implosions, however, it will be necessary to generate shaped radiation pulses. Specifically, it will be necessary to generate a 10-20 ns foot prior to the main radiation pulse, with about 1/14 the amplitude of the peak radiation. One possible method of generating an appropriately shaped radiation pulse is to use nested wire arrays. The array parameters can in principle be chosen to allow different arrival times on axis, thereby producing a shaped radiation pulse. To investigate this possibility, we utilized a simple formulation for self and mutual inductances for the nested arrays. We added to this formulation a modification of the equations of motion by introducing instantaneous momentum transfer when the position of the two arrays coincides.

Radiography with x rays is a long-established method to see inside objects, from human limbs to weapon parts. Livermore scientists have a continuing need for powerful x rays for such applications as backlighting, or illuminating, inertial confinement fusion (ICF) experiments and imaging still or exploding materials for the nation's Stockpile Stewardship Program. X-radiography is one of the prime diagnostics for ICF experiments because it captures the fine detail needed to determine what happens to nearly microscopic targets when they are compressed by laser light. For example, Livermore scientists participating in the National Ignition Facility's (NIF's) 18-month-long Early Light experimental campaign, which ended in 2004, used x rays to examine hydrodynamic instabilities in jets of plasma. In these experiments, one laser beam irradiated a solid target of titanium, causing it to form a high-temperature plasma that generated x rays of about 4.65 kiloelectronvolts (keV). These x rays backlit a jet of plasma formed when two other laser beams hit a plastic ablator and sent a shock to an aluminum washer. Livermore physicist Kevin Fournier of the Physics and Advanced Technologies Directorate leads a team that is working to increase the efficiency of converting laser energy into x rays so the resulting images provide more information about the object being illuminated. The main characteristics of x-ray sources are energy and brightness. ''As experimental targets get larger and as compression of the targets increases, the backlighter sources must be brighter and more energetic'', says Fournier. The more energetic the x rays, the further they penetrate an object. The brighter the source--that is, the more photons it has--the clearer the image. historically, researchers have used solid targets such as thin metal foils to generate x rays. however, when photon energies are greater than a few kiloelectronvolts, the conversion efficiency of solid targets is only a fraction of 1 percent. Solid targets have low efficiencies because much of the laser energy is deposited far from the target's x-ray emitting region, and the energy is carried by the relatively slow process of thermal conduction. ''The laser beam ablates material from the massive target, and that material moves away from the target's surface'', says Fournier. With a nanosecond pulse or longer, the laser interacts with the blow-off plasma rather than the remaining bulk sample. As a result, much of the laser's energy goes into the kinetic energy of the blow-off material, not into heating the bulk of the foil.

This book is a collection of papers, written by specialists in the field, on advanced topics of nuclear fusion diagnostics. The 78 contributions were originally presented at the International Conference on Advanced Diagnostics for Magnetic and Inertial Fusion held at Villa Monastero, Italy in September 2001. Both magnetically confined and inertial fusion programmes are quite extensively covered, with more emphasis given to the former scheme. In the case of magnetic confinement, since the present international programme is strongly focused on next-step devices, particular attention is devoted to techniques and technologies viable in an environment with strong neutron fluxes. Indeed, in the first section, the various methods are considered in the perspective of performing the measurements of the relevant parameters in conditions approaching a burning plasma, mainly in the Tokamak configuration. The most demanding requirements, like the implications of the use of tritium and radiation resistance, are reviewed and the most challenging open issues, which require further research and development, are also clearly mentioned.The following three sections are devoted to some of the most recent developments in plasma diagnostics, which are grouped according to the following classification: `Neutron and particle diagnostics', `Optical and x-ray diagnostics' and `Interferometry, Polarimetry and Thomson Scattering'. In these chapters, several of the most recent results are given, covering measurements taken on the most advanced experiments around the world. Here the developments described deal more with the requirements imposed by the physical issues to be studied. They are therefore more focused on the approaches adopted to increase the spatial and time resolution of the diagnostics, on some methods to improve the characterisation of the turbulence and on fast particles. Good coverage is given to neutron diagnostics, which are assuming increasing relevance as the plasma parameters approach ignition. Spectroscopic systems and their recent developments are well represented, whereas edge diagnostics are somewhat thin on the ground. A dedicated section is devoted to the latest tests on radiation effects and technological issues. The problems of damage to optical components and the difficulties presented by the determination of the tritium inventory are described.In the last part, the new diagnostic systems of the most recent experiments (under construction or recently operated) are reported. Various aspects of some diagnostics not included in the three previous sections are also covered, with particular emphasis on microwaves and infrared diagnostics.The book is well suited for specialists and, more generally, for people involved in nuclear fusion, who need information about the most recent developments in the field of plasma diagnostics. The papers cover many aspects of the challenges and possible solutions for performing measurements in fusion machines approaching reactor conditions. On the other hand, the contributions are in general quite advanced and would be challenging for people without a significant background in plasma diagnostics and nuclear fusion. The quality of the paper is more than satisfactory both from the point of view of clarity and of graphics. Moreover, at the beginning of the book, several papers make a considerable effort to put diagnostic issues in the wider context of present day nuclear fusion research. For those topics, which are too involved to be completely described in a conference contribution, in general adequate references are provided for deeper investigation.A MurariApproximately one third of the papers included in this volume deal with diagnostics related to inertial confinement fusion plasmas (i.e., laser-produced plasmas and pulsed-power). These papers discuss recent developments in charged particle diagnostics, neutron diagnostics, optical and x-ray measurements along with laser and particle probing diagnostics. The resulting collection of papers is comprehensive and wide-ranging and all of the major laboratories in Europe, the US, and Japan are represented. There is important discussion on the development of diagnostics for the National Ignition Facility, LMJ, and future ultra-high intensity laser experiments as well as papers on wire array z-pinch experiments. It is especially useful to have the contributions from inertial confinement fusion experiments intermingled with those from magnetic confinement fusion. The separation between these two approaches to fusion is often unfortunately large, so one of the pleasing things about this book is that it is very easy for readers familiar with experimental research in one area to compare `state of the art' plasma diagnostics in the other area. Hopefully this will facilitate the development of new ideas in both areas. This book is a conference proceedings and as such, almost all of the papers included are quite brief and are highly technical. Consequently, the book is not particularly pedagogical and would be most useful to researchers already working in this area of physics. For these readers, however, Advanced Diagnostics for Magnetic and Inertial Confinement Fusion is an excellent overview of the present status of fusion plasma diagnostics.K Krushelnick

Building a sustainable burn platform in inertial confinement fusion (ICF) requires an understanding of the complex coupling of physical processes and the effects that key experimental design changes have on implosion performance. While simulation codes are used to model ICF implosions, incomplete physics and the need for approximations deteriorate their predictive capability. Identification of relationships between controllable design inputs and measurable outcomes can help guide the future design of experiments and development of simulation codes, which can potentially improve the accuracy of the computational models used to simulate ICF implosions. In this paper, we leverage developments in machine learning (ML) and methods for ML feature importance/sensitivity analysis to identify complex relationships in ways that are difficult to process using expert judgment alone. We present work using random forest (RF) regression for prediction of yield, velocity, and other experimental outcomes given a suite of design parameters, along with an assessment of important relationships and uncertainties in the prediction model. We show that RF models are capable of learning and predicting on ICF experimental data with high accuracy, and we extract feature importance metrics that provide insight into the physical significance of different controllable design inputs for various ICF design configurations. These results can be used to augment expert intuition and simulation results for optimal design of future ICF experiments.

Recent advancements in indirect-drive inertial confinement fusion (ICF) experiments at the National Ignition Facility (NIF) have achieved a significant milestone by demonstrating target gains greater than one, yet future applications necessitate much higher target gains. One approach to achieving improved implosion performance is to pursue increased fuel compression via a lowered implosion adiabat. Experiments have been performed testing a reduced adiabat by introducing small changes to the drive laser pulse shape and the resulting shock timing for an existing implosion design at 1.9 MJ laser drive with near-ignition performance (experiment N210808). Experiments using the updated design demonstrate, for the very first time, increased compression and fusion yield in ICF implosions on the NIF by using a lower fuel adiabat, and increased compression with a reduced adiabat in high-density carbon ablators. Compared to the previously best-performing experiment with a laser energy of 1.9 MJ, these experiments exhibit increases of up to 80% and 14% in nuclear fusion yield and fuel compression, respectively, and with repeatable performance. Further, it is the only implosion design to have achieved a target gain exceeding one with a laser energy of less than 2 MJ. These findings highlight the efficacy of reduced adiabat designs in achieving higher compression and fusion yields, offering a promising pathway for future ICF applications. This Letter not only addresses a long-standing question in ICF but also paves the way for achieving higher target gains with optimized implosion strategies.

Inertial Confinement Fusion (ICF) experiments performed on high-power laser facilities produce a high intensity short pulse of 14 MeV neutrons. The interaction of such an environment with coaxial cables widely used for signals transmission of diagnostic equipments induces parasitic transient currents. Depending on the magnitude and shape of those currents, measurement signals are likely to be altered and electric devices might be damaged. This paper reviews our knowledge about the generation of parasitic current in polyethylene (PE), PolyTetraFluorEthylene (PTFE) and PolyEtherEtherKetone (PEEK) insulators subjected to an ICF neutron pulse. It provides a clear evidence of the existence of a prompt neutron component and a very fast, nanosecond delayed radiation induced electromotive force (RIEMF) in insulator response to very short neutron pulses.

A central element of a power plant based on inertial confinement fusion (ICF) is a target with cryogenic hydrogen fuel that should be delivered to the center of a reactor chamber with a high accuracy and repetition rate. Therefore, a cryogenic target factory (CTF) is an integral part of any ICF reactor. A promising way to solve this problem consists in the FST layering method developed at the Lebedev Physical Institute (LPI). This method (rapid fuel layering inside moving free-standing targets) is unique, having no analogs in the world. The further development of FST-layering technologies is implemented in the scope of the LPI program for the creation of a modular CTF and commercialization of the obtained results. In this report, we discuss our concept of CTF (CTF-LPI) that exhibits the following distinctive features: using a FST-layering technology for the elaboration of an in-line production of cryogenic targets, using an effect of quantum levitation of high-temperature superconductors (HTSCs) in magnetic field for noncontacting manipulation, transport, and positioning of the free-standing cryogenic targets, as well as in using a Fourier holography technique for an on-line characterization and tracking of the targets flying into the reactor chamber. The results of original experimental and theoretical investigations performed at LPI indicate that the existing and developing target fabrication capabilities and technologies can be applied to ICF target production. The unique scientific, engineering, and technological base developed in Russia at LPI allows one to make a CTFLPI prototype for mass production of targets and delivery thereof at the required velocity into the ICF reactor chamber.

Experiments performed on an inertial confinement fusion (ICF) platform offer a unique opportunity to study nuclear reactions, including reaction branches that are useful for diagnostic applications in ICF experiments as well as several that are relevant to nuclear astrophysics. In contrast to beam-accelerator experiments, experiments performed on an ICF platform occur over a short time scale and produce a plasma environment with physical parameters that are directly relevant to big bang and/or stellar nucleosynthesis. Several reactions of interest, such as D(T,γ)5He, H(D,γ)3He, H(T,γ)4He, and T(3He,γ)6Li produce high-energy gamma rays. S factors or branching ratios for these four reactions have recently been studied using various temporally-resolved Cherenkov detectors at the Omega laser facility. This work describes these detectors as well as the current standard technique for performing these measurements. Recent results for reactions D(T,γ)5He, H(D,γ)3He, H(T,γ)4He, and T(3He,γ)6Li are reviewed and compared to accelerator-based measurements. Limitations associated with implosion experiments and use of the current standard gamma detectors are discussed. A basic design for a gamma spectrometer for use at ICF facilities is briefly outlined.

In the traditional three DOFs (degrees of freedom) PMs (parallel manipulators), the terminal constraints are constraint forces and torques. A recent study showed that the terminal constraints of some three DOFs PMs are screw-type constraints. However, determining the mobility of this class of PMs remains challenging. In order to solve the above problems, this paper discusses the mobility of PMs having independent screw-type terminal constraints by introducing the principal screws. Firstly, taking a 3-CCR (C: cylindrical joint, R: revolute joint) PM as an example, the problem of identifying the mobility of PMs having screw-type constraints is proposed. Secondly, combined with the analytical expression of the terminal constraint and theory of quadratic curve decomposition, the mobility determination approach is given. Finally, a numerical example for solving the principal screws and determining the mobility of the 3-CCR PM is provided. Furthermore, the axodes of four poses with three helical DOFs and four poses with three rotational DOFs were plotted. The results show that there is a special phenomenon in which three rotational DOFs and three helical DOFs exist alternately in the workspace of this PM. This paper provides a method for directly identifying the independent helical DOFs in parallel manipulators and for studying the distribution of helical DOFs within the workspace.

Analysis of a novel cylindrical 3-DoF parallel robot

Significant electromagnetic pulses (EMP) can be generated by the intensive laser irradiating solid targets in inertial confinement fusion (ICF). To evaluate the EMP intensity and distribution in and outside the laser chamber, we designed and fabricated a discone antenna with ultra-wide bands of over 10 GHz. The return loss (S11 parameter) of this antenna was below −10 dB and could even achieve under −30 dB at 3.1 GHz. The EMP intensity in this study at 80 cm and 40 cm away from the target chamber center (TCC) reached 400 kV/m and 2000 kV/m. The current results are expected to offer preliminary information to study physics regarding laser plasma interactions and will also lay experimental foundation for EMI shielding design to protect various diagnostics.