68 Matching Results

Search Results

Advanced search parameters have been applied.

LDRD 102610 final report new processes for innovative microsystems engineering with predictive simulation.

Description: This LDRD Final report describes work that Stephen W. Thomas performed in 2006. The initial problem was to develop a modeling, simulation, and optimization strategy for the design of a high speed microsystem switch. The challenge was to model the right phenomena at the right level of fidelity, and capture the right design parameters. This effort focused on the design context, in contrast to other Sandia efforts focus on high-fidelity assessment. This report contains the initial proposal and the annual progress report. This report also describes exploratory work on micromaching using femtosecond lasers. Steve's time developing a proposal and collaboration on this topic was partly funded by this LDRD.
Date: August 1, 2007
Creator: Mattsson, Ann Elisabet; Mitchell, Scott A. & Thomas, Stephen W.
Partner: UNT Libraries Government Documents Department

A low power ultra-fast current transient measuring device.

Description: We have studied the feasibility of an innovative device to sample 1ns low-power single current transients with a time resolution better than 10 ps. The new concept explored here is to close photoconductive semiconductor switches (PCSS) with a Laser for a period of 10 ps. The PCSSs are in a series along a Transmission Line (TL). The transient propagates along the TL allowing one to carry out a spatially resolved sampling of charge at a fixed time instead of the usual timesampling of the current. The fabrication of such a digitizer was proven to be feasible but very difficult.
Date: October 1, 2004
Creator: Doyle, Barney Lee; Rossi, Paolo; Armendariz, Marcelino G.; Sullivan, John Patrick; Foltynowicz, Robert J. & Zutavern, Fred J.
Partner: UNT Libraries Government Documents Department

High-speed, sub-pull-in voltage MEMS switching.

Description: We have proposed and demonstrated MEMS switching devices that take advantage of the dynamic behavior of the MEMS devices to provide lower voltage actuation and higher switching speeds. We have explored the theory behind these switching techniques and have demonstrated these techniques in a range of devices including MEMS micromirror devices and in-plane parallel plate MEMS switches. In both devices we have demonstrated switching speeds under one microsecond which has essentially been a firm limit in MEMS switching. We also developed low-loss silicon waveguide technology and the ability to incorporate high-permittivity dielectric materials with MEMS. The successful development of these technologies have generated a number of new projects and have increased both the MEMS switching and optics capabilities of Sandia National Laboratories.
Date: January 1, 2008
Creator: Spahn, Olga Blum; Brewer, Steven; Olsson, Roy H.; Bogart, Gregory R.; Luck, David L.; Watts, Michael R. et al.
Partner: UNT Libraries Government Documents Department

Active RF Pulse Compression using Electrically Controlled Semiconductor Switches

Description: In this paper, we will present our recent results on the research of the ultra-fast high power RF switches based on silicon. We have developed a switch module at X-band which can use a silicon window as the switch. The switching is realized by generation of carriers in the bulk silicon. The carriers can be generated electrically or/and optically. The electrically controlled switches use PIN diodes to inject carrier. We have built the PIN diode switches at X-band, with <300ns switching time. The optically controlled switches use powerful lasers to excite carriers. By combining the laser excitation and electrical carrier generation, significant reduction in the required power of both the laser and the electrical driver is expected. High power test is under going.
Date: January 30, 2008
Creator: Guo, J. & Tantawi, S. G.
Partner: UNT Libraries Government Documents Department

Active RF Pulse Compression Using Electrically Controlled Semiconductor Switches

Description: In this paper, we present the recent results of our research on the ultra-high power fast silicon RF switch and its application on active X-Band RF pulse compression systems. This switch is composed of a group of PIN diodes on a high purity silicon wafer and has achieved a switching time of 300ns. The wafer is inserted into a cylindrical waveguide operating in the TE01 mode. Switching is performed by injecting carriers into the bulk silicon through a high current pulse. The RF energy is stored in a room-temperature, high-Q 375 ns delay line; it is then extracted out of the line in a short time using the switch. The pulse compression system has achieved a gain of 8, which is the ratio between output and input power.
Date: March 21, 2007
Creator: Guo, J. & Tantawi, S.
Partner: UNT Libraries Government Documents Department

Device Technology Investigation: Subsystems Packaging Study: Feasibility of PCSS - Based Pulser for Highly Portable Platforms

Description: This report summarizes an investigation of the use of high-gain Photo-Conductive Semiconductor Switch (PCSS) technology for a deployable impulse source. This includes a discussion of viability, packaging, and antennas. High gain GaAs PCSS-based designs offer potential advantages in terms of compactness, repetition rate, and cost.
Date: July 1, 2002
Creator: MAR, ALAN; BACON, LARRY D. & LOUBRIEL, GUILLERMO M.
Partner: UNT Libraries Government Documents Department

High gain GaAs photoconductive semiconductor switches: Switch longevity

Description: Optically activated, high gain GaAs switches are being tested for many different pulsed power applications that require long lifetime (longevity). The switches have p and n contact metallization (with intentional or unintentional dopants) configured in such a way as to produce p-i-n or n-i-n switches. The longevity of the switches is determined by circuit parameters and by the ability of the contacts to resist erosion. This paper will describe how the switches performed in test-beds designed to measure switch longevity. The best longevity was achieved with switches made with diffused contacts, achieving over 50 million pulses at 10 A and over 2 million pulses at 80 A.
Date: July 1, 1998
Creator: Loubriel, G.M.; Zutavern, F.J. & Mar, A.
Partner: UNT Libraries Government Documents Department

Doped Contacts for High-Longevity Optically Activated, High Gain GaAs Photoconductive Semiconductor Switches

Description: The longevity of high gain GaAs photoconductive semiconductor switches (PCSS) has been extended to over 100 million pulses. This was achieved by improving the ohmic contacts through the incorporation of a doped layer that is very effective in the suppression of filament formation, alleviating current crowding. Damage-free operation is now possible with virtually infinite expected lifetime at much higher current levels than before. The inherent damage-free current capacity of the bulk GaAs itself depends on the thickness of the doped layers and is at least 100A for a dopant diffusion depth of 4pm. The contact metal has a different damage mechanism and the threshold for damage ({approx}40A) is not further improved beyond a dopant diffusion depth of about 2{micro}m. In a diffusion-doped contact switch, the switching performance is not degraded when contact metal erosion occurs, unlike a switch with conventional contacts. This paper will compare thermal diffusion and epitaxial growth as approaches to doping the contacts. These techniques will be contrasted in terms of the fabrication issues and device characteristics.
Date: December 17, 1999
Creator: MAR,ALAN; LOUBRIEL,GUILLERMO M.; ZUTAVERN,FRED J.; O'MALLEY,MARTIN W.; HELGESON,WESLEY D.; BROWN,DARWIN JAMES et al.
Partner: UNT Libraries Government Documents Department

Longevity improvement of optically activated, high gain GaAs photoconductive semiconductor switches

Description: The longevity of high gain GaAs photoconductive semiconductor switches (PCSS) has been extended to over 100 million pulses at 23A, and over 100 pulses at 1kA. This is achieved by improving the ohmic contacts by doping the semi-insulating GaAs underneath the metal, and by achieving a more uniform distribution of contact wear across the entire switch by distributing the trigger light to form multiple filaments. This paper will compare various approaches to doping the contacts, including ion implantation, thermal diffusion, and epitaxial growth. The device characterization also includes examination of the filament behavior using open-shutter, infra-red imaging during high gain switching. These techniques provide information on the filament carrier densities as well as the influence that the different contact structures and trigger light distributions have on the distribution of the current in the devices. This information is guiding the continuing refinement of contact structures and geometries for further improvements in switch longevity.
Date: March 2, 2000
Creator: MAR,ALAN; LOUBRIEL,GUILLERMO M.; ZUTAVERN,FRED J.; O'MALLEY,MARTIN W.; HELGESON,WESLEY D.; BROWN,DARWIN JAMES et al.
Partner: UNT Libraries Government Documents Department

A Collective Impact Ionization Theory of Lock-On

Description: PhotoConductive semiconductor switches (PCSS's), such as optically-triggered GaAs switches, have been developed for a variety of applications. Such switches exhibit unique properties associated with lock-on, a phenomenon associated with bistable switching. In this paper lock-on is explained in terms of collective impact ionization.
Date: September 2, 1999
Creator: HJALMARSON, HAROLD P.; KAMBOUR, CHARLES; KANG, SAMSOO; LOUBRIEL, GUILLERMO M.; MYLES, CHARLES W.; WAKE, DOUGLAS RAYMON et al.
Partner: UNT Libraries Government Documents Department

Doped Contacts for High-Longevity Optically Activated, High Gain GaAs Photoconductive Semiconductor Switches

Description: The longevity of high gain GaAs photoconductive semiconductor switches (PCSS) has been extended to over 50 million pulses. This was achieved by improving the ohmic contacts through the incorporation of a doped layer beneath the PCSS contacts which is very effective in the suppression of filament formation and alleviating current crowding to improve the longevity of PCSS. Virtually indefinite, damage-free operation is now possible at much higher current levels than before. The inherent damage-free current capacity of the switch depends on the thickness of the doped layers and is at least 100A for a dopant diffusion depth of 4pm. The contact metal has a different damage mechanism and the threshold for damage ({approximately}40A) is not further improved beyond a dopant diffusion depth of about 2{micro}m. In a diffusion-doped contact switch, the switching performance is not degraded when contact metal erosion occurs. This paper will compare thermal diffusion and epitaxial growth as approaches to doping the contacts. These techniques will be contrasted in terms of the fabrication issues and device characteristics.
Date: August 5, 1999
Creator: Baca, A.G.; Brown, D.J.; Donaldson, R.D.; Helgeson, W.D.; Hjalmarson, H.P.; Loubriel, G.M. et al.
Partner: UNT Libraries Government Documents Department

Photoconductive Semiconductor Switch Technology for Short Pulse Electromagnetics and Lasers

Description: High gain photoconductive semiconductor switches (PCSS) are being used to produce high power electromagnetic pulses foc (1) compact, repetitive accelerators, (2) ultra-wide band impulse sources, (3) precision gas switch triggers, (4) optically-activated firesets, and (5) high power optical pulse generation and control. High power, sub-nanosecond optical pulses are used for active optical sensors such as compact optical radars and range-gated hallistic imaging systems. Following a brief introduction to high gain PCSS and its general applications, this paper will focus on PCSS for optical pulse generation and control. PCSS technology can be employed in three distinct approaches to optical pulse generation and control: (1) short pulse carrier injection to induce gain-switching in semiconductor lasers, (2) electro-optical Q-switching, and (3) optically activated Q-switching. The most significant PCSS issues for these applications are switch rise time, jitter, and longevity. This paper will describe both the requirements of these applications and the most recent results from PCSS technology. Experiments to understand and expand the limitations of high gain PCSS will also be described.
Date: August 5, 1999
Creator: Denison, Gary J.; Helgeson, Wesley D.; Hjalmarson, Harold P.; Loubriel, Guillermo M.; Mar, Alan; O'Malley, Martin W. et al.
Partner: UNT Libraries Government Documents Department

Time-dependent simulations of filament propagation in photoconducting switches

Description: The authors present a model for investigating filamentary structures observed in laser-triggered photoswitches. The model simulates electrons and holes in two-dimensional cylindrical (r-z) geometry, with realistic electron and hole mobilities and field dependent impact ionization. Because of the large range of spatial and temporal scales to be resolved, they are using an explicit approach with fast, direct solution of the field equation. A flux limiting scheme is employed to avoid the time-step constraint due to the short time for resistive relaxation in the high density filament. Self-consistent filament propagation with speeds greater than the carrier drift velocity are observed in agreement with experiments.
Date: May 1, 1994
Creator: Rambo, P. W.; Lawson, W. S.; Capps, C. D. & Falk, R. A.
Partner: UNT Libraries Government Documents Department

Fiber-optic control of current filaments in high gain photoconductive semiconductor switches

Description: The discovery of current filaments in GaAs photoconductive semiconductor switches (PCSS) raised concerns about the location and density of the current distribution during high gain switching. This paper describes experiments using fiber-optic coupled laser diode arrays (LDA) to control the location and number of current filaments in GaAs PCSS. Infrared (IR) images of the recombination radiation, that is emitted from the surface of the PCSS, show precisely where the current is concentrated. These were recorded as the fiber-optic configuration and switch test parameters were varied. Up to twenty individually-coupled laser diodes and fibers were used to initiate multiple, simultaneous filaments. Fibers were configured in a row both parallel and perpendicular to the direction of current. Two types of experiments were performed: high current and high voltage. System impedances of 0.25 {Omega} and 50 {Omega} were used with switch currents up to 5.2 kA and initial charging voltages up to 100 kV, respectively. Switch sizes were 1{times}5 mm{sup 2} and 15{times}38 mm{sup 2} (parallel {times} perpendicular to the current). With the 0.25 {Omega} system charged to 4 kV (40 kV/cm across the PCSS), individual filaments were triggered with 150 nJ of optical trigger energy. In this case, filaments were triggered at both ends near the contacts with pairs of 250 {mu}m fibers, each of which delivered 75 nJ in 140 ps. The use of multiple fiber pairs to distribute the current more uniformly across the switch improved switch performance. It allowed higher total currents to be switched with narrower switches. With the 50 {Omega} system charged to 100 kV (67 kV/cm across the PCSS), individual filaments were triggered with as little as 90 nJ of optical trigger energy. The trigger pulse was delivered in 2 ns through one fiber which was 400 {mu}m in diameter.
Date: August 1, 1994
Creator: Zutavern, F. J.; Loubriel, G. M.; Helgeson, W. D.; O`Malley, M. W.; Gallegos, R. R.; Baca, A. G. et al.
Partner: UNT Libraries Government Documents Department

Longevity of optically activated, high gain GaAs photoconductive semiconductor switches

Description: The longevity of high gain GaAs photoconductive semiconductor switches (PCSS) has been extended to well over 10 million pulses by reducing the density of carriers at the semiconductor to metal interface. This was achieved by reducing the density in the vertical and lateral directions. The first was achieved by varying the spatial distribution of the trigger light thereby widening the current filaments that are characteristic of the high gain switches. The authors reduced the carrier density in the vertical direction by using ion implantation. These results were obtained for currents of about 10 A, current duration of 3.5 ns, and switched voltage of {approximately}2 kV. At currents of {approximately}70 A, the switches last for 0.6 million pulses. In order to improve the performance at high currents new processes such as deep diffusion and epitaxial growth of contacts are being pursued. To guide this effort the authors measured a carrier density of 6 x 10{sup 18} electrons (or holes)/cm{sup 3} in filaments that carry a current of 5 A.
Date: August 1, 1997
Creator: Loubriel, G.M.; Zutavern, F.J. & Mar, A.
Partner: UNT Libraries Government Documents Department

Photoconductive semiconductor switches: Laser Q-switch trigger and switch-trigger laser integration

Description: This report provides a summary of the Pulser In a Chip 9000-Discretionary LDRD. The program began in January of 1997 and concluded in September of 1997. The over-arching goal of this LDRD is to study whether laser diode triggered photoconductive semiconductor switches (PCSS) can be used to activate electro-optic devices such as Q-switches and Pockels cells and to study possible laser diode/switch integration. The PCSS switches we used were high gain GaAs switches because they can be triggered with small amounts of laser light. The specific goals of the LDRD were to demonstrate: (1) that small laser diode arrays that are potential candidates for laser-switch integration will indeed trigger the PCSS switch, and (2) that high gain GaAs switches can be used to trigger optical Q-switches in lasers such as the lasers to be used in the X-1 Advanced Radiation Source and the laser used for direct optical initiation (DOI) of explosives. The technology developed with this LDRD is now the prime candidate for triggering the Q switch in the multiple lasers in the laser trigger system of the X-1 Advanced Radiation Source and may be utilized in other accelerators. As part of the LDRD we developed a commercial supplier. To study laser/switch integration we tested triggering the high gain GaAs switches with: edge emitting laser diodes, vertical cavity surface emitting lasers (VCSELs), and transverse junction stripe (TJS) lasers. The first two types of lasers (edge emitting and VCSELs) did activate the PCSS but are harder to integrate with the PCSS for a compact package. The US lasers, while easier to integrate with the switch, did not trigger the PCSS at the US laser power levels we used. The PCSS was used to activate the Q-switch of the compact laser to be used in the X-1 Advanced Radiation Source.
Date: December 1, 1997
Creator: Loubriel, G.M.; Mar, A.; Hamil, R.A.; Zutavern, F.J. & Helgeson, W.D.
Partner: UNT Libraries Government Documents Department

Properties of high gain GaAs switches for pulsed power applications

Description: High gain GaAs photoconductive semiconductor switches (PCSS) are being used in a variety of electrical and optical short pulse applications. The highest power application, which the authors are developing, is a compact, repetitive, short pulse linear induction accelerator. The array of PCSS, which drive the accelerator, will switch 75 kA and 250 kV in 30 ns long pulses at 50 Hz. The accelerator will produce a 700 kV, 7kA electron beam for industrial and military applications. In the low power regime, these switches are being used to switch 400 A and 5 kV to drive laser diode arrays which produce 100 ps optical pulses. These short optical pulses are for military and commercial applications in optical and electrical range sensing, 3D laser radar, and high speed imaging. Both types of these applications demand a better understanding of the switch properties to increase switch lifetime, reduce jitter, optimize optical triggering, and improve overall switch performance. These applications and experiments on the fundamental behavior of high gain GaAs switches will be discussed. Open shutter, infra-red images and time-resolved images of the current filaments, which form during high gain switching, will be presented. Results from optical triggering experiments to produce multiple, diffuse filaments for high current repetitive switching will be described.
Date: September 1, 1997
Creator: Zutavern, F.J.; Loubriel, G.M.; Hjalmarson, H.P.; Mar, A.; Helgeson, W.D.; O`Malley, M.W. et al.
Partner: UNT Libraries Government Documents Department

Final report of LDRD project: Electromagnetic impulse radar for detection of underground structures

Description: This report provides a summary of the LDRD project titled: Electromagnetic impulse radar for the detection of underground structures. The project met all its milestones even with a tight two year schedule and total funding of $400 k. The goal of the LDRD was to develop and demonstrate a ground penetrating radar (GPR) that is based on high peak power, high repetition rate, and low center frequency impulses. The idea of this LDRD is that a high peak power, high average power radar based on the transmission of short impulses can be utilized effect can be utilized for ground penetrating radar. This direct time-domain system the authors are building seeks to increase penetration depth over conventional systems by using: (1) high peak power, high repetition rate operation that gives high average power, (2) low center frequencies that better penetrate the ground, and (3) short duration impulses that allow for the use of downward looking, low flying platforms that increase the power on target relative to a high flying platform. Specifically, chirped pulses that are a microsecond in duration require (because it is difficult to receive during transmit) platforms above 150 m (and typically 1 km) while this system, theoretically could be at 10 m above the ground. The power on target decays with distance squared so the ability to use low flying platforms is crucial to high penetration. Clutter is minimized by time gating the surface clutter return. Short impulses also allow gating (out) the coupling of the transmit and receive antennas.
Date: March 1, 1998
Creator: Loubriel, G.; Aurand, J.; Buttram, M.; Zutavern, F.; Brown, D. & Helgeson, W.
Partner: UNT Libraries Government Documents Department

Testing results for the HCT-1400 switch

Description: The High Current Thyristor (HCT)-1400 was characterized for switching performance. This is a Soviet switching device that has recently become available to the U.S. community. Substantial claims have been made regarding the performance of this switch. In particular, the switch was claimed to be able to switch high currents, with very short risetime without any significant jitter. This is an independent evaluation of the high current thyristor.
Date: July 1, 1996
Creator: Hoeberling, R.F. & Wheeler, R.B.
Partner: UNT Libraries Government Documents Department

Final report task order number B239641 between the Regents of the University of California and Institute of Experimental Physics task 2: Switch development.

Description: The LLNL project of the pulsed power system for the National Ignition Facility requires a switch with the following operational parameters: peak current of 400 kA, the transferred charge of 150 C, operating voltage of 25 kV, and reliable operating life of 10,000 shots. A review of high-power switches is given with detailed studies on vacuum switches and semiconductor switches.
Date: December 31, 1994
Creator: Galakhov, I.V.; Gruzin, I.A.; Gudov, S.N.; Kirillov, G.A.; Logutenko, S.L.; Murugov, V.M. et al.
Partner: UNT Libraries Government Documents Department

Design and preliminary results for a fast bipolar resonant discharge pulser using SCR switches for driving the injection bump magnets at the ALS

Description: A fast (4.0 us half period) resonant discharge pulser using SCRs has been designed and constructed to drive the injection bump magnet system at the Advanced Light Source (ALS). The pulser employs a series-parallel arrangement of Silicon Controlled Rectifiers (SCRS) that creates a bipolar high voltage ({plus_minus}10 KV), high peak current (6600 amps.) and a high di/dt (6000 amp/us) switch network that discharges a capacitor bank into the magnet load. Fast recovery diodes in series with the SCRs significantly reduces the SCR turn-off time during the negative current cycle of the magnet. The SCR switch provides a very reliable and stable alternative to the gas filled Thyratron. A very low impedance transmission system allows the pulser system to reside completely outside the storage ring shielding wall.
Date: May 1, 1993
Creator: Stover, G. & Reginato, L.
Partner: UNT Libraries Government Documents Department

Design and test of a low jitter metal to metal contact solid dielectric switch

Description: A low jitter metal to metal contact solid dielectric switch was designed and tested. A metal to metal contact solid dielectric switch with a jitter of less than 25 ns is required for the 150 kJ experiment. Since this is one fourth the 100 ns jitter reported using exploding bridge foil (EBF) triggers, experiments to optimize this trigger were performed. A jitter of 25 ns was achieved using the EBF trigger and it was also achieved using a new type of trigger called the magnetic push trigger. This trigger uses the magnetic force between the two plates of a parallel plate transmission line to push the dielectric. It was found to be better than the EBF trigger because it was easier to design, easier to implement and did less damage to switch components.
Date: March 1, 1993
Creator: Domning, E. E.
Partner: UNT Libraries Government Documents Department