Received 28 February 2011DOI:https://doi.org/10.1103/PhysRevLett.106.109903© 2011 American Physical Society

We demonstrate the hohlraum radiation temperature and symmetry required for ignition-scale inertial confinement fusion capsule implosions. Cryogenic gas-filled hohlraums with 2.2 mm-diameter capsules are heated with unprecedented laser energies of 1.2 MJ delivered by 192 ultraviolet laser beams on the National Ignition Facility. Laser backscatter measurements show that these hohlraums absorb 87% to 91% of the incident laser power resulting in peak radiation temperatures of T(RAD)=300 eV and a symmetric implosion to a 100 μm diameter hot core.

The National Ignition Facility (NIF) is a 192-beam laser fusion driver operating at Lawrence Livermore National Laboratory. NIF relies on three large-scale pulsed power systems to achieve its goals: the Power Conditioning Unit (PCU), which provides flashlamp excitation for the laser's injection system; the Power Conditioning System (PCS), which provides the multi-megajoule pulsed excitation required to drive flashlamps in the laser's optical amplifiers; and the Plasma Electrode Pockels Cell (PEPC), which enables NIF to take advantage of a four-pass main amplifier. Years of production, installation, and commissioning of the three NIF pulsed power systems are now complete. Seven-day-per-week operation of the laser has commenced, with the three pulsed power systems providing routine support of laser operations. We present the details of the status and operational experience associated with the three systems along with a projection of the future for NIF pulsed power.

Summary form given only. The Power Conditioning System of the National Ignition Facility provides the pulsed excitation required to drive flashlamps in the laser's optical amplifiers. Modular in design, each of the 192 Main Energy Storage Modules (MESMs) stores up to 2.2 MJ of electrical energy in its capacitor bank before delivering the energy to 20 pairs of flashlamps in a 400 mus pulse (10% power points). The peak current of each MESM discharge is 0.5 MA. Production, installation, commissioning and operation of the NIF Power Conditioning System continue to progress rapidly, with the goals of completing accelerated production in late 2007 and finishing commissioning by early 2008, all the while maintaining an aggressive operations schedule. To date, more than 60% of the required modules have been assembled, shipped and installed in the facility, representing more that 240 MJ of stored energy available for driving NIF flashlamps. The MESMs have displayed outstanding reliability during daily, multiple-shift operations.

At its design level, PEP-II will circulate asymmetric beams at 9 GeV and 1.5 A in a High Energy Ring and 3.1 GeV with 2.1 A in a Low Energy Ring. In addition, the vacuum systems of both rings will be designed to operate at a maximum current of 3 A to provide for higher current operation in the future. Pumping for both rings is provided by sputter ion pump systems. In the High Energy Ring, high gas loads, deriving from the intense photon radiation, are calculated at 1.06×10-6 Torr liters s-1 m-1 using a desorption coefficient (eta) of 2×10-6 molecules photon-1. To maintain an average pressure of 5 nTorr or less in the are cells, lumped ion pumps are used in the 2 m long straight sections and distributed ion pumps are used in the 6 m long dipole chambers where the conductance of the vacuum chamber is prohibitively low. To achieve these pressures, the distributed ion pump system is required to have pumping speeds of 110 liters s-1 m -1 however, a design level of 165 liters s-1 m-1 has been set to provide a factor of safety of 50% based on pumping alone

A new timing system has been designed to meet the requirements for the one megawatt test set (MWTS). This test set is a system of power supplies, support systems, controls, and monitors that will be used for the development of 1-MW gyrotrons. The purpose of the timing system is to provide timing signals for control of the gyrotron's cathode, anode, and heater power supplies as well as oscilloscope, digitizer, and other control or diagnostic triggers. Some unique timing requirements include four main operating modes: single pulse, repetitive pulse, continuous wave (CW), and CW cathode with repetitively pulsed anode. Timing adjustments can be made while the tube is running with no adverse effects. This modular, distributed timing system is implemented using two CAMAC modules: the master timing controller and the two channel timing generator. A single master timing controller provides real-time control and synchronization for all timing generators in the system. The timing generators provide triggers having adjustable delay and duration to the various system components

The authors describe the installation and operation of the 400 kW 140 GHz gyrotron used for plasma heating on the Microwave Tokamak Experiment (MTX). The gyrotron system comprises a high-voltage (80 kV) modulated power supply, a multistation CAMAC computer control, a 5 T superconducting magnet, a series of conventional copper magnets, a circulating fluorinert (FC75) window cooling system, a circulating oil cooling system, a water cooling system, and microwave frequency and power diagnostics. The microwave power measured at the MTX tokamak input is typically 200 kW for a gyrotron output of approximately 400 kW. Losses in the system arise from power in modes other than the desired TE 15,2 mode, transport losses in the Vlasov sidelobes, small waveguide losses to the Vlasov, and small losses in the quasi-optical beamline. Individual MTX shots with the gyrotron have shown a stored energy increase of 1 kJ in the plasma in high density plasmas, and central electron temperature increases of up to 800 eV have been obtained. Even larger temperature increases have been observed recently in low density plasmas

A new precision timing system has been installed on the Microwave Tokamak Experiment (MTX). The purpose of the system is to synchronize the tokamak's plasma discharge with a 140 GHz, 2 GW microwave pulse generated by a free-electron laser (FEL). The installation involved modifying the existing sequencer system and adding digital delay generators, three in-house-designed CAMAC modules, and other components. The system controls placement of the 30 ns FEL pulse during the MTX plasma discharge and provides decision triggers for the microwave plasma diagnostics. These triggers are distributed over 100 Mb/s fiber-optic links. The MTX interlock system has been expanded to provide personnel safety during FEL experiments, to protect the FEL and related equipment, and to control the path of the FEL beam starting from the FEL's output, through the beam transport system, and into the tokamak. How the existing MTX timing and interlock systems were upgraded to accommodate these new FEL experiments is described.<>

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTAssociation Reactions for Poly(alkylene Oxides) and Polymeric Poly(carboxylic Acids)K. L. Smith, A. E. Winslow, and D. E. PetersenCite this: Ind. Eng. Chem. 1959, 51, 11, 1361–1364Publication Date (Print):November 1, 1959Publication History Published online1 May 2002Published inissue 1 November 1959https://doi.org/10.1021/ie50599a029Request reuse permissions Article Views381Altmetric-Citations160LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (397 KB) Get e-Alerts