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Early-Time (E1) High-Altitude Electromagnetic Pulse Effects on Trip Coils

Sanabria, David E.; Bowman, Tyler B.; Guttromson, Ross G.; Halligan, Matthew H.; Le, Ken L.; Lehr, J.M.

A High-Altitude Electromagnetic Pulse (HEMP) is a potential threat to the power grid. HEMP can couple to transmission lines and cables, causing significant overvoltages which can be harmful to line connected equipment. The effects of overvoltages on various types of power systems components need to be understood. HEMP effects on trip coils were tested and presented in this report. A high voltage pulser was built to replicate the induced voltage waveform from a HEMP. The pulser was used to test breaker trip coils with increasing pulse magnitudes ranging from 20 kV to 80 kV. The State-of-Health of each trip coils was measured via mechanical operation and impedance measurements before and after each insult to identify any damage or degradation to the trip coils. Dielectric breakdown was observed at the conductor leads during testing, causing the HEMP insult to be diverted to the grounded casing. However, the dielectric breakdown did not cause interference with regular device operation.

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Early-Time (E1) High-Altitude Electromagnetic Pulse Effects on Transient Voltage Surge Suppressors

Llanes, Rodrigo E.; Halligan, Matthew H.; Guttromson, Ross G.; Lehr, J.M.; dougan, nikita d.; Le, Ken L.; diaz, david d.

Determining the effectiveness of surge and pulse protection devices in the United States power grid against effects of a High-Altitude Electromagnetic Pulse (HEMP) is crucial in determining the present state of grid resilience. Transient Voltage Surge Suppressors (TVSS) are used to protect loads in substations from transient overvoltages. Designed to mitigate the effects of lightning, their response to a HEMP event is unknown and was determined. TVSSs were tested in two unique configurations using a pulser that generates pulses in the tens of nanoseconds scale to determine their protective capability as well as to determine their self-resilience against HEMP pulses. Testing concluded that TVSS devices adequately protect against microsecond scale pulses like lightning but do not protect against pulses resembling HEMP events. It suggests that TVSS devices should not be relied upon to mitigate the effects of HEMP pulses.

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Impact of time-varying loads on the programmable pulsed power driver called genesis

Digest of Technical Papers-IEEE International Pulsed Power Conference

Glover, Steven F.; Davis, Jean-Paul D.; Schneider, Larry X.; Reed, Kim W.; Pena, Gary P.; Hall, Clint A.; Hanshaw, Heath L.; Hickman, Randy J.; Hodge, K.C.; Lemke, Raymond W.; Lehr, J.M.; Lucero, D.J.; McDaniel, Dillon H.; Puissant, J.G.; Rudys, Joseph M.; Sceiford, Matthew S.; Tullar, S.J.; Van De Valde, D.M.; White, F.E.; Warne, Larry K.; Coats, Rebecca S.; Johnson, William Arthur.

The success of dynamic materials properties research at Sandia National Laboratories has led to research into ultra-low impedance, compact pulsed power systems capable of multi-MA shaped current pulses with rise times ranging from 220-500 ns. The Genesis design consists of two hundred and forty 200 kV, 80 kA modules connected in parallel to a solid dielectric disk transmission line and is capable of producing 280 kbar of magnetic pressure (>500 kbar pressure in high Z materials) in a 1.75 nH, 20 mm wide stripline load. Stripline loads operating under these conditions expand during the experiment resulting in a time-varying load that can impact the performance and lifetime of the system. This paper provides analysis of time-varying stripline loads and the impact of these loads on system performance. Further, an approach to reduce dielectric stress levels through active damping is presented as a means to increase system reliability and lifetime. © 2011 IEEE.

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Status of genesis a 5 MA programmable pulsed power driver

Digest of Technical Papers-IEEE International Pulsed Power Conference

Glover, Steven F.; White, F.E.; Foster, P.J.; Lucero, D.J.; Schneider, Larry X.; Reed, Kim W.; Pena, Gary P.; Davis, Jean-Paul D.; Hall, Clint A.; Hickman, Randy J.; Hodge, K.C.; Lemke, Raymond W.; Lehr, J.M.; McDaniel, Dillon H.; Puissant, J.G.; Rudys, Joseph M.; Sceiford, Matthew S.; Tullar, S.J.; Van De Valde, D.M.

Genesis is a compact pulsed power platform designed by Sandia National Laboratories to generate precision shaped multi-MA current waves with a rise time of 200-500 ns. In this system, two hundred and forty, 200 kV, 80 kA modules are selectively triggered to produce 280 kbar of magnetic pressure (>500 kbar pressure in high Z materials) in a stripline load for dynamic materials properties research. This new capability incorporates the use of solid dielectrics to reduce system inductance and size, programmable current shaping, and gas switches that must perform over a large range of operating conditions. Research has continued on this technology base with a focus on demonstrating the integrated performance of key concepts into a Genesis-like prototype called Protogen. Protogen measures approximately 1.4 m by 1.4 m and is designed to hold twelve Genesis modules. A fixed inductance load will allow rep-rate operation for component reliability and system lifetime experiments at the extreme electric field operating conditions expected in Genesis. © 2011 IEEE.

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Surface interactions involved in flashover with high density electronegative gases

Warne, Larry K.; Jorgenson, Roy E.; Lehr, J.M.

This report examines the interactions involved with flashover along a surface in high density electronegative gases. The focus is on fast ionization processes rather than the later time ionic drift or thermalization of the discharge. A kinetic simulation of the gas and surface is used to examine electron multiplication and includes gas collision, excitation and ionization, and attachment processes, gas photoionization and surface photoemission processes, as well as surface attachment. These rates are then used in a 1.5D fluid ionization wave (streamer) model to study streamer propagation with and without the surface in air and in SF6. The 1.5D model therefore includes rates for all these processes. To get a better estimate for the behavior of the radius we have studied radial expansion of the streamer in air and in SF6. The focus of the modeling is on voltage and field level changes (with and without a surface) rather than secondary effects, such as, velocities or changes in discharge path. An experiment has been set up to carry out measurements of threshold voltages, streamer velocities, and other discharge characteristics. This setup includes both electrical and photographic diagnostics (streak and framing cameras). We have observed little change in critical field levels (where avalanche multiplication sets in) in the gas alone versus with the surface. Comparisons between model calculations and experimental measurements are in agreement with this. We have examined streamer sustaining fields (field which maintains ionization wave propagation) in the gas and on the surface. Agreement of the gas levels with available literature is good and agreement between experiment and calculation is good also. Model calculations do not indicate much difference between the gas alone versus the surface levels. Experiments have identified differences in velocity between streamers on the surface and in the gas alone (the surface values being larger).

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Streamer initiation in volume and surface discharges in atmospheric gases

Proceedings of the 2008 IEEE International Power Modulators and High Voltage Conference, PMHVC

Lehr, J.M.; Warne, Larry K.; Jorgenson, Roy E.; Wallace, Z.R.; Hodge, K.C.; Caldwell, Michele C.

It is generally acknowledged that once a highly conductive channel is established between two charged and conducting materials, electrical breakdown is well established and difficult to interrupt. An understanding of the initiation mechanism for electrical breakdown is crucial for devising mitigating methods to avoid catastrophic failures. Both volumetric and surface discharges are of interest. An effort is underway where experiments and theory are being simultaneously developed. The experiment consists of an impedance matched discharge chamber capable of investigating various gases and pressures to ten atmospheres. In addition to current and voltage measurements, a high dynamic range streak camera records streamer velocities. The streamer velocities are particularly valuable for comparison with theory. A streamer model is being developed which includes photo-ionization and particle interactions with an insulating surface. The combined theoretical and experimental effort is aimed at detailed comparisons of streamer development as well as a quantitative understanding of how streamers interact with dielectric surfaces and the resulting effects on breakdown voltage. © 2008 IEEE.

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A 5-megavolt, 600-kiloampere laser-triggered gas switch for use on Z-R: Comparison of experiments and simulations

Digest of Technical Papers-IEEE International Pulsed Power Conference

Woodworth, Joseph R.; Rosenthal, Stephen E.; Lehr, J.M.; Maenchen, John E.; Elizondo, J.; Johnson, D.L.; Corley, J.P.; Hodge, K.C.; Drennan, S.A.; Guthrie, D.W.

The Z Refurbishment project is designed to increase the peak current to the load on Z to ∼26 MA in a 100-ns wide power pulse. This current is achieved by summing the current from 36 independent pulse-power modules. To meet these requirements, we have designed and constructed an SF6-insulated gas switch that can hold off 5.5 MV and conduct a peak current of 600 kA for over a hundred shots. The gas switch is charged by a Marx generator in ∼1 microsecond and transfers about 200-kilojoules of energy and 0.25 Coulombs of charge to a pulse-forming line in a ∼150-ns-wide power pulse peaking at 2.5 TW. The gas switch oonsists of a laser-triggered section holding off 15% of the voltage followed by 25 self-breakdown gaps. The self-breaking gaps are designed to provide multiple breakdown arcs in order to lower the overall inductance of the switch. The gas switch is submerged in transformer oil during operation. In this work, we show how simulation and experiment have worked together, first to verify proper operation of the switch, and then to solve problems with the switch design that arose during testing. © 2005 IEEE.

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Performance of self-closing diverter switches for ZR/Z20 marx and intermediate store protection

Digest of Technical Papers-IEEE International Pulsed Power Conference

Douglas, J.; Banister, J.; Corcoran, P.; Goyer, J.; Miller, R.; Morton, D.; Nishimoto, H.; Smith, I.; Corley, J.; Drennan, S.; Guthrie, D.; Hodge, K.; Lehr, J.M.; Maenchen, John E.; Smith, D.; Sears, R.

The ZR refurbishment project [1] at Sandia National Laboratories (SNL) required a set of diverter switches to protect the Marx generators and intermediate storage (IS) capacitors from Marx pre-fire and/or laser triggered output switch (LTS) no-fire. Thirty-six such diverters, one for each Marx-IS set, will need to operate reliably over the full range of Marx charge voltages and LTS anticipated closure times. Operating voltage is up to 6 MV. A self-closing oil switch diverter was selected and design work began in late 2002. The first diverter (Phase I or just P1) was delivered in the summer of 2003 and tested on SNL's Z20 test-bed. Based on test results, operational experience and overall project budgetary concerns, it was decided to re-design the diverter, resulting a simpler, less costly switch. This new self-closing oil switch (Phase II or P2) was fielded at SNL on the Z20 test-bed in late 2004. Both designs include adjustable electrodes to control the closure time. Also incorporated is a mechanical clamp that minimizes or shorts the oil gap until Marx charge is complete. Both diverters feature liquid resistors sized to safely absorb the energy stored in the Marx or IS. This paper describes the design and test results from these diverters. © 2005 IEEE.

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Transient electromagnetic modeling of the ZR accelerator water convolute and stack

Digest of Technical Papers-IEEE International Pulsed Power Conference

Pasik, Michael F.; Coats, Rebecca S.; Johnson, William Arthur.; Elizondo-Decanini, Juan M.; Pointon, Timothy D.; Turner, C.D.; Bohnhoff, William J.; Lehr, J.M.; Savage, Mark E.

The ZR accelerator is a refurbishment of Sandia National Laboratories Z accelerator [1]. The ZR accelerator components were designed using electrostatic and circuit modeling tools. Transient electromagnetic modeling has played a complementary role in the analysis of ZR components [2]. In this paper we describe a 3D transient electromagnetic analysis of the ZR water convolute and stack using edge-based finite element techniques. © 2005 IEEE.

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Copy of An overview of pulse compression and power flow in the upgraded Z pulsed power driver

Savage, Mark E.; Maenchen, John E.; McDaniel, Dillon H.; Pasik, Michael F.; Pointon, Timothy D.; Owen, Albert C.; Seidel, David B.; Stoltzfus, Brian S.; Struve, Kenneth W.; Warne, Larry K.; Bennett, Lawrence F.; Woodworth, Joseph R.; Bliss, David E.; Clark, Waylon T.; Coats, Rebecca S.; Elizondo-Decanini, Juan M.; LeChien, Keith R.; Harjes, Henry C.; Lehr, J.M.

Abstract not provided.

Multimegavolt laser-triggered gas switching with a green laser and beam transport through water

IEEE Transactions on Plasma Science

Zameroski, Nathan D.; Lehr, J.M.; Woodworth, Joseph R.; Blickem, Jim R.; Hodge, Keith C.; Wallace, Zachariah R.; Anaya, Victor; Corley, John P.; Lott, John A.

Ultraviolet (UV) laser-triggered gas switching using laser beams at 266 nm has greatly improved the simultaneity of many large multimodule accelerators. This UV beam however cannot be transmitted significant distances through water or oil. Since the switches in these accelerators are typically submerged in water or oil, the laser beams are often conveyed to the switches through gas-filled "laser crossover tubes."These crossover tubes are difficult to field grade properly and are subject to frequent mechanical and electrical failures in the pulse-power environment. We have demonstrated that a 4.6-MV multistage gas switch insulated with SF6 can be triggered with a jitter of less than 10 ns using 110-mJ pulses of a green (532-nm) laser beam that has been transported through 67 cm of 1-MΩcm water on its way to the switch. These results may allow elimination of the laser crossover tubes in future accelerators. © 2007 IEEE.

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Fundamental science investigations to develop a 6-MV laser triggered gas switch for ZR: first annual report

Maenchen, John E.; Savage, Mark E.; Struve, Kenneth W.; Woodworth, Joseph R.; Lehr, J.M.; Warne, Larry K.; Bliss, David E.; Jorgenson, Roy E.; LeChien, Keith R.; McKee, George R.; Pasik, Michael F.; Rosenthal, Stephen E.

In October 2005, an intensive three-year Laser Triggered Gas Switch (LTGS) development program was initiated to investigate and solve observed performance and reliability issues with the LTGS for ZR. The approach taken has been one of mission-focused research: to revisit and reassess the design, to establish a fundamental understanding of LTGS operation and failure modes, and to test evolving operational hypotheses. This effort is aimed toward deploying an initial switch for ZR in 2007, on supporting rolling upgrades to ZR as the technology can be developed, and to prepare with scientific understanding for the even higher voltage switches anticipated needed for future high-yield accelerators. The ZR LTGS was identified as a potential area of concern quite early, but since initial assessments performed on a simplified Switch Test Bed (STB) at 5 MV showed 300-shot lifetimes on multiple switch builds, this component was judged acceptable. When the Z{sub 20} engineering module was brought online in October 2003 frequent flashovers of the plastic switch envelope were observed at the increased stresses required to compensate for the programmatically increased ZR load inductance. As of October 2006, there have been 1423 Z{sub 20} shots assessing a variety of LTGS designs. Numerous incremental and fundamental switch design modifications have been investigated. As we continue to investigate the LTGS, the basic science of plastic surface tracking, laser triggering, cascade breakdown, and optics degradation remain high-priority mission-focused research topics. Significant progress has been made and, while the switch does not yet achieve design requirements, we are on the path to develop successively better switches for rolling upgrade improvements to ZR. This report summarizes the work performed in FY 2006 by the large team. A high-level summary is followed by detailed individual topical reports.

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Resistance of a water spark

Warne, Larry K.; Jorgenson, Roy E.; Lehr, J.M.

The later time phase of electrical breakdown in water is investigated for the purpose of improving understanding of the discharge characteristics. One dimensional simulations in addition to a zero dimensional lumped model are used to study the spark discharge. The goal is to provide better electrical models for water switches used in the pulse compression section of pulsed power systems. It is found that temperatures in the discharge channel under representative drive conditions, and assuming small initial radii from earlier phases of development, reach levels that are as much as an order of magnitude larger than those used to model discharges in atmospheric gases. This increased temperature coupled with a more rapidly rising conductivity with temperature than in air result in a decreased resistance characteristic compared to preceding models. A simple modification is proposed for the existing model to enable the approximate calculation of channel temperature and incorporate the resulting conductivity increase into the electrical circuit for the discharge channel. Comparisons are made between the theoretical predictions and recent experiments at Sandia. Although present and past experiments indicated that preceding late time channel models overestimated channel resistance, the calculations in this report seem to underestimate the resistance relative to recent experiments. Some possible reasons for this discrepancy are discussed.

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LASER TRIGGERED GAS SWITCHES UTILIZING BEAM TRANSPORT THROUGH 1 MO-cm DEIONIZED WATER

Woodworth, Joseph R.; Lehr, J.M.; Zameroski, Nathan D.

We report on the successful attempts to trigger high voltage pressurized gas switches by utilizing beam transport through 1 MO-cm deionized water. The wavelength of the laser radiation was 532 nm. We have investigated Nd: YAG laser triggering of a 6 MV, SF6 insulated gas switch for a range of laser and switch parameters. Laser wavelength of 532 nm with nominal pulse lengths of 10 ns full width half maximum (FWHM) were used to trigger the switch. The laser beam was transported through 67 cm-long cell of 1 MO-cm deionized water constructed with anti reflection UV grade fused silica windows. The laser beam was then focused to form a breakdown arc in the gas between switch electrodes. Less than 10 ns jitter in the operation of the switch was obtained for laser pulse energies of between 80-110 mJ. Breakdown arcs more than 35 mm-long were produced by using a 70 cm focusing optic.

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Analysis of the polarity effects in the electrical breakdown of liquids

Proposed for publication in Physical Review E.

Woodworth, Joseph R.; Lehr, J.M.

Electrical breakdown simulations are carried out for liquids in response to a sub-microsecond ({approx}100-200 ns) voltage pulse. This model builds on our previous analysis and focuses particularly on the polarity effect seen experimentally in point-plane geometries. The flux-corrected transport approach is used for the numerical implementation. Our model adequately explains experimental observations of pre-breakdown current fluctuations, streamer propagation and branching as well as disparities in hold-off voltage and breakdown initiation times between the anode and cathode polarities. It is demonstrated that polarity effects basically arise from the large mobility difference between electrons and ions. The higher electron mobility leads to greater charge smearing and diffusion that impacts the local electric field distributions. Non-linear couplings between the number density, electric field and charge generation rates then collectively affect the formation of ionized channels and their temporal dynamics.

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SATPro: the system assessment test program for Z-R

Lehr, J.M.

In the mid-90's, breakthroughs were achieved at Sandia with z-pinches for high energy density physics on the Saturn machine. These initial tests led to the modification of the PBFA II machine to provide high currents rather than the high voltage it was initially designed for. The success of z-pinch for high energy density physics experiments insured a new mission for the converted accelerator, known as Z since 1997. Z now provides a unique capability to a number of basic science communities and has expanded its mission to include radiation effects research, inertial confinement fusion and material properties research. To achieve continued success, the physics community has requested higher peak current, better precision and pulse shaping versatility be incorporated into the refurbishment of the Z machine, known as ZR. In addition to the performance specification for ZR of a peak current of 26 MA with an implosion time of 100 ns, the machine also has a reliability specification to achieve 400 shots per year. While changes to the basic architecture of the Z machine are minor, the vast majority of its components have been redesigned. Moreover the increase in peak current from its present 18 MA to ZR's peak current of 26 MA at nominal operating parameters requires significantly higher voltages. These higher voltages, along with the reliability requirement, mandate a system assessment be performed to insure the requirements have been met. This paper will describe the System Assessment Test Program (SATPro) for the ZR project and report on the results.

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Capacitance and effective area of flush monopole probes

Basilio, Lorena I.; Warne, Larry K.; Johnson, William Arthur.; Higgins, Matthew B.; Lehr, J.M.

Approximate formulas are constructed and numerical simulations are carried out for electric field derivative probes that have the form of flush mounted monopoles. Effects such as rounded edges are included. A method is introduced to make results from two-dimensional conformal mapping analyses accurately apply to the three-dimensional axisymmetric probe geometry

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Electromagnetic analysis and modeling of the coax-to-triplate transition for the pulse-compression section of the ZR accelerator

Digest of Technical Papers-IEEE International Pulsed Power Conference

Johnson, William Arthur.; Coats, Rebecca S.; Jorgenson, Roy E.; Kotulski, J.D.; Lehr, J.M.; Pasik, Michael F.; Rosenthal, Stephen E.; Turner, C.D.; Warne, Larry K.

Transverse electromagnetic (TEM) wave analysis is used to estimate the efficiencies of the coax to triplate transition in Sandia's Z-20 test module. The structure of both the TEM mode and higher order TE modes in the triplate transmission line are characterized. In addition, three dimensional time domain simulations are carried out and used in conjunction with the modal analysis to provide insight into the wave structure excited in the triplate transmission line.

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Development/tests of 6-MV triggered gas switches at SNL

Digest of Technical Papers-IEEE International Pulsed Power Conference

Corley, John P.; Hodge, K.C.; Drennan, S.A.; Guthrie, D.W.; Navarro, J.M.; Johnson, David L.; Lehr, J.M.; Rosenthal, Stephen E.; Elizondo-Decanini, Juan M.

Gas switch development for application in Z refurbishment (ZR) has continued since PPPS Conference 2001. Several iterations have been tested both in oil and water dielectrics. The first switch tested was an evolved version of the Sandia designed HERMES III switch. The 6MV ZR Baseline Switch consists of a self-breakdown (cascade) section in which the discharge current flows in several parallel channels, and a trigger section where the current flows through a single spark channel. The second switch tested is a Cantilevered Switch. The entire cascade section is cantilevered on a plastic support rod allowing for a single continuous insulator housing but having the same characteristics as the Baseline. The third switch tested is a Sandia Hybrid switch. The laser triggered section of the Hybrid switch includes 5 Cascade like electrodes connected in parallel to a triggered gap via a ∼2μH series isolation inductor. The discharge current in the Hybrid switch trigger section flows in several parallel channels eliminating the single channel flow as in the Baseline Switch trigger section. The design iterations of these switches and results of these tests are presented.

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Measurement of the dielectric properties of dispersive materials over a wide frequency range

Bacon, Larry D.; Bacon, Larry D.; Lehr, J.M.; Molina, Luis L.; Salazar, Robert S.

The propagation of electromagnetic waves through dispersive media forms the basis for a wide variety of applications. Rapid advances in materials have produced new products with tailored responses across frequency bands. Many of these new materials, such as radar absorbing material and photonic crystals, are dispersive in nature. This, in turn, has opened up the possibility for the exploitation of these dispersive dielectric properties for a variety of applications. Thus, it is desirable to know the electromagnetic properties of both man-made and natural materials across a wide frequency range. With the advent of transient pulsers with sub-nanosecond risetimes and rates of voltage rise approaching 10**16 V/s, the frequencies of interest in the transient response extend to approximately the 2 GHz range. Although a network analyzer can provide either frequency- or time-domain data (by inverse transform), common TEM cells are only rated to 0.5 to 1.5 GHz--significantly below the maximum frequency of interest. To extend the frequency range to include 2 GHz, a TEM cell was characterized and a deembedding algorithm was applied to account, in part, for the limitations of the cell. The de-embedding technique is described along with such measurement issues such as clear time and sneak around. Measurements of complex permittivity of common drinking water are shown. This frequency extension will lead to more expansive testing of dielectric materials of interest.

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52 Results
52 Results