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CHANGING THE SAFETY CULTURE IN HANFORD TANK FARMS (open access)

CHANGING THE SAFETY CULTURE IN HANFORD TANK FARMS

In 2000 the Hanford Tank Farms had one of the worst safety records in the Department of Energy Complex. By the end of FY08 the safety performance of the workforce had turned completely around, resulting in one of the best safety records in the DOE complex for operations of its kind. This paper describes the variety of programs and changes that were put in place to accomplish such a dramatic turn-around. The U.S. Department of Energy's 586-square-mile Hanford Site in Washington State was established during World War II as part of the Manhattan Project to develop nuclear materials to end the war. For the next several decades it continued to produce plutonium for the nation's defense, leaving behind vast quantities of radioactive and chemical waste. Much of this waste, 53,000,000 gallons, remains stored in 149 aging single-shell tanks and 28 newer double-shell tanks. One of the primary objectives at Hanford is to safely manage this waste until it can be prepared for disposal, but this has not always been easy. These giant underground tanks, many of which date back to the beginning of the Manhattan Project, range in size from 55,000 gallons up to 1.1 million gallons, and are buried …
Date: January 6, 2009
Creator: MV, BERRIOCHOA & LJ, ALCALA
System: The UNT Digital Library
Resonance--Continuum Interference in Light Higgs Boson Production at a Photon Collider (open access)

Resonance--Continuum Interference in Light Higgs Boson Production at a Photon Collider

We study the effect of interference between the Standard Model Higgs boson resonance and the continuum background in the process {gamma}{gamma} {yields} H {yields} b{bar b} at a photon collider. Taking into account virtual gluon exchange between the final-state quarks, we calculate the leading corrections to the height of the resonance for the case of a light (m{sub H} < 160 GeV) Higgs boson. We find that the interference is destructive and around 0.1-0.2% of the peak height, depending on the mass of the Higgs and the scattering angle. This suppression is smaller by an order of magnitude than the anticipated experimental accuracy at a photon collider. However, the fractional suppression can be significantly larger if the Higgs coupling to b quarks is increased by physics beyond the Standard Model.
Date: January 6, 2009
Creator: Dixon, Lance J.; Sofianatos, Yorgos & /SLAC /Stanford U., Phys. Dept.
System: The UNT Digital Library
STATUS OF MECHANICAL SLUDGE REMOVAL AND COOLING COILS CLOSURE AT THE SAVANNAH RIVER SITE - F TANK FARM CLOSURE PROJECT - 9225 (open access)

STATUS OF MECHANICAL SLUDGE REMOVAL AND COOLING COILS CLOSURE AT THE SAVANNAH RIVER SITE - F TANK FARM CLOSURE PROJECT - 9225

The Savannah River Site F-Tank Farm Closure project has successfully performed Mechanical Sludge Removal using the Waste on Wheels (WOW) system within two of its storage tanks. The Waste on Wheels (WOW) system is designed to be relatively mobile with the ability for many components to be redeployed to multiple tanks. It is primarily comprised of Submersible Mixer Pumps (SMPs), Submersible Transfer Pumps (STPs), and a mobile control room with a control panel and variable speed drives. These tanks, designated as Tank 6 and Tank 5 respectively, are Type I waste tanks located in F-Tank Farm (FTF) with a capacity of 2839 cubic meters (750,000 gallons) each. In addition, Type I tanks have 34 vertically oriented cooling coils and two horizontal cooling coil circuits along the tank floor. DOE intends to remove from service and operationally close Tank 5 and Tank 6 and other HLW tanks that do not meet current containment standards. After obtaining regulatory approval, the tanks and cooling coils will be isolated and filled with grout for long term stabilization. Mechanical Sludge Removal of the remaining sludge waste within Tank 6 removed {approx} 75% of the original 25,000 gallons in August 2007. Utilizing lessons learned from Tank …
Date: January 6, 2009
Creator: Jolly, R
System: The UNT Digital Library
What's Inside the Black Box - Explaining Performance Assessment to Stakeholders (open access)

What's Inside the Black Box - Explaining Performance Assessment to Stakeholders

The performance assessment (PA) process is being applied to support an increasing variety of waste management decisions that involve the whole spectrum of stakeholders. As with many technical tools, the PA process can be seen as a black box, which can be difficult to understand when implemented. Recognizing the increasing use of PA and the concerns about difficulties with understanding, the Savannah River Site Citizens Advisory Board (CAB) made a recommendation that the U.S. Department of Energy (DOE) provide a Public Educational Forum on PAs. The DOE-Headquarters Environmental Management (DOE-EM) Office of Compliance and the DOE-Savannah River (DOE-SR) responded to this recommendation by supporting the Savannah River National Laboratory (SRNL) in developing several presentation modules that can be used to describe different aspects of the PA process. For the Public Educational Forum, the PA modules were combined with presentations on DOE perspectives, historical modeling efforts at the Savannah River Site, and review perspectives from the U.S. Nuclear Regulatory Commission (NRC). The overall goals are to help the public understand how PAs are implemented and the rigor that is applied, and to provide insight into the use of PAs for waste management decision-making.
Date: January 6, 2009
Creator: Seitz, R. & Elmer Wilhite, E.
System: The UNT Digital Library
REFERENCE CASES FOR USE IN THE CEMENTITIOUS BARRIERS PARTNERSHIP (open access)

REFERENCE CASES FOR USE IN THE CEMENTITIOUS BARRIERS PARTNERSHIP

The Cementitious Barriers Project (CBP) is a multidisciplinary cross cutting project initiated by the US Department of Energy (DOE) to develop a reasonable and credible set of tools to improve understanding and prediction of the structural, hydraulic and chemical performance of cementitious barriers used in nuclear applications. The period of performance is >100 years for operating facilities and > 1000 years for waste management. The CBP has defined a set of reference cases to provide the following functions: (1) a common set of system configurations to illustrate the methods and tools developed by the CBP, (2) a common basis for evaluating methodology for uncertainty characterization, (3) a common set of cases to develop a complete set of parameter and changes in parameters as a function of time and changing conditions, and (4) a basis for experiments and model validation, and (5) a basis for improving conceptual models and reducing model uncertainties. These reference cases include the following two reference disposal units and a reference storage unit: (1) a cementitious low activity waste form in a reinforced concrete disposal vault, (2) a concrete vault containing a steel high-level waste tank filled with grout (closed high-level waste tank), and (3) a spent …
Date: January 6, 2009
Creator: Langton, C
System: The UNT Digital Library
Search for Lepton Flavour Violating Decays tau- to l- Ks with the BaBar experiment (open access)

Search for Lepton Flavour Violating Decays tau- to l- Ks with the BaBar experiment

A search for the lepton flavor violating decays {tau}{sup -} {yields} l{sup -} K{sub S}{sup 0} (l = e or {mu}) has been performed using a data sample corresponding to an integrated luminosity of 469 fb{sup -1}, collected with the BABAR detector at the SLAC PEP-II e{sup +}e{sup -} asymmetric energy collider. No statistically significant signal has been observed in either channel and the estimated upper limits on branching fractions are {Beta}({tau}{sup -} {yields} e{sup -} K{sub S}{sup 0}) < 3.3 x 10{sup -8} and {Beta}({tau}{sup -} {yields} {mu}{sup -}K{sub S}{sup 0}) < 4.0 x 10{sup -8} at 90% confidence level.
Date: January 6, 2009
Creator: Aubert, B.; Bona, M.; Karyotakis, Y.; Lees, J. P.; Poireau, V.; Prencipe, E. et al.
System: The UNT Digital Library
Thick target measurement of the 40Ca(alpha,gamma)44Ti reaction rate (open access)

Thick target measurement of the 40Ca(alpha,gamma)44Ti reaction rate

The thick-target yield for the {sup 40}Ca({alpha},{gamma}){sup 44}Ti reaction has been measured for E{sub beam} = 4.13, 4.54, and 5.36 MeV using both an activation measurement and online {gamma}-ray spectroscopy. The results of the two measurements agree. From the measured yield a reaction rate is deduced that is smaller than statistical model calculations. This implies a smaller {sup 44}Ti production in supernova compared to recently measured {sup 40}Ca({alpha},{gamma}){sup 44}Ti reaction rates.
Date: February 6, 2009
Creator: Sheets, S A; Burke, J T; Scielzo, N D; Phair, L; Bleuel, D; Norman, E B et al.
System: The UNT Digital Library
2009 Photosynthesis to be held June 28 - July 3, 2009 (open access)

2009 Photosynthesis to be held June 28 - July 3, 2009

The capture of solar energy by photosynthesis has had a most profound influence on the development and sustenance of life on earth. It is the engine that has driven the proliferation of life and, as the source of both energy and oxygen, has had a major hand in shaping the forms that life has taken. Both ancient and present day photosynthetic carbon fixation is intimately tied to issues of immediate human concern, global energy and global warming. Decreasing our reliance on fossil fuels by tapping photosynthesis in a more direct way is an attractive goal for sustainable energy. Meeting this challenge means understanding photosynthetic energy conversion at a molecular level, a task requiring perspectives ranging through all disciplines of science. Researchers in photosynthesis have a strong history of working across conventional boundaries and engaging in multidisciplinary collaborations. The Gordon conference in photosynthesis has been a key focal point for the dissemination of new results and the establishment of powerful research collaborations. In this spirit the 2009 Gordon conference on biophysical aspects of photosynthesis will bring together top international researchers from diverse and complementary disciplines, all working towards understanding how photosynthesis converts light into the stable chemical energy that powers so …
Date: July 6, 2009
Creator: Bruce, Doug
System: The UNT Digital Library
Investigations of Cadmium Manganese Telluride Crystals for Room-Temperature Radiation Detection (open access)

Investigations of Cadmium Manganese Telluride Crystals for Room-Temperature Radiation Detection

Cadmium manganese telluride (CMT) has high potential as a material for room-temperature nuclear-radiation detectors. We investigated indium-doped CMT crystals taken from the stable growth region of the ingot, and compared its characteristics with that from the last-to-freeze region. We employed different techniques, including synchrotron white-beam X-ray topography (SWBXT), current-voltage (I-V) measurements, and low-temperature photoluminescence spectra, and we also assessed their responses as detectors to irradiation exposure. The crystal from the stable growth region proved superior to that from the last-to-freeze region; it is a single-grain crystal, free of twins, and displayed a resistivity higher by two orders-of-magnitude. The segregation of indium dopant in the ingot might be responsible for its better resistivity. Furthermore, we recorded a good response in the detector fabricated from the crystal taken from the stable growth region; its ({mu}{tau}){sub e} value was 2.6 x 10{sup -3} cm{sup 2}/V, which is acceptable for thin detectors, including for applications in medicine.
Date: October 6, 2009
Creator: Yang, G.; Bolotnikov, A.; Camarda, G.; Cui, Y.; Hossain, A.; Kim, K. et al.
System: The UNT Digital Library
Molecular beam epitaxy of GaNAs alloys with high As content for potential photoanode applications in hydrogen production (open access)

Molecular beam epitaxy of GaNAs alloys with high As content for potential photoanode applications in hydrogen production

The authors have succeeded in growing GaN1?xAsx alloys over a large composition range (0 < x < 0.8) by plasma-assisted molecular beam epitaxy. The enhanced incorporation of As was achieved by growing the films with high As{sub 2} flux at low (as low as 100 C) growth temperatures, which is much below the normal GaN growth temperature range. Using x-ray and transmission electron microscopy, they found that the GaNAs alloys with high As content x > 0.17 are amorphous. Optical absorption measurements together with x-ray absorption and emission spectroscopy results reveal a continuous gradual decrease in band gap from -3.4 to < 1 eV with increasing As content. The energy gap reaches its minimum of -0.8 eV at x - 0.8. The composition dependence of the band gap of the crystalline GaN{sub 1?x}As{sub x} alloys follows the prediction of the band anticrossing model (BAC). However, our measured band gap of amorphous GaN{sub 1?x}As{sub x} with 0.3 < x < 0.8 are larger than that predicted by BAC. The results seem to indicate that for this composition range the amorphous GaN{sub 1?x}As{sub x} alloys have short-range ordering that resembles random crystalline GaN{sub 1?x}As{sub x} alloys. They have demonstrated the possibility of …
Date: October 6, 2009
Creator: Novikov, S. V.; Staddon, C. R.; Foxon, C. T.; Yu, K. M.; Broesler, R.; Hawkridge, M. et al.
System: The UNT Digital Library
Possible Diamond-Like Nanoscale Structures Induced by Slow Highly-Charged Ions on Graphite (HOPG) (open access)

Possible Diamond-Like Nanoscale Structures Induced by Slow Highly-Charged Ions on Graphite (HOPG)

The interaction between slow highly-charged ions (SHCI) of different charge states from an electron-beam ion trap and highly oriented pyrolytic graphite (HOPG) surfaces is studied in terms of modification of electronic states at single-ion impact nanosizeareas. Results are presented from AFM/STM analysis of the induced-surface topological features combined with Raman spectroscopy. I-V characteristics for a number of different impact regions were measured with STM and the results argue for possible formation of diamond-like nanoscale structures at the impact sites.
Date: January 6, 2009
Creator: Sideras-Haddad, E.; Schenkel, T.; Shrivastava, S.; Makgato, T.; Batra, A.; Weis, C. D. et al.
System: The UNT Digital Library
Economics of residential gas furnaces and water heaters in United States new construction market (open access)

Economics of residential gas furnaces and water heaters in United States new construction market

New single-family home construction represents a significant and important market for the introduction of energy-efficient gas-fired space heating and water-heating equipment. In the new construction market, the choice of furnace and water-heater type is primarily driven by first cost considerations and the availability of power vent and condensing water heaters. Few analysis have been performed to assess the economic impacts of the different combinations of space and water-heating equipment. Thus, equipment is often installed without taking into consideration the potential economic and energy savings of installing space and water-heating equipment combinations. In this study, we use a life-cycle cost analysis that accounts for uncertainty and variability of the analysis inputs to assess the economic benefits of gas furnace and water-heater design combinations. This study accounts not only for the equipment cost but also for the cost of installing, maintaining, repairing, and operating the equipment over its lifetime. Overall, this study, which is focused on US single-family new construction households that install gas furnaces and storage water heaters, finds that installing a condensing or power-vent water heater together with condensing furnace is the most cost-effective option for the majority of these houses. Furthermore, the findings suggest that the new construction residential …
Date: May 6, 2009
Creator: Lekov, Alex B.; Franco, Victor H.; Wong-Parodi, Gabrielle; McMahon, James E. & Chan, Peter
System: The UNT Digital Library
Chemical and electronic characterization of cobalt in Lanthanumperovskites. Effects of Strontium substitution (open access)

Chemical and electronic characterization of cobalt in Lanthanumperovskites. Effects of Strontium substitution

Two different cobaltites, LaCoO{sub 3} and La{sub 0.5}Sr{sub 0.5}CoO{sub 3-{delta}}, have been prepared and characterized by means of high energy Co K-edge and low energy O K-edge X-ray absorption spectroscopy (XAS). The partial substitution of La(III) by Sr(II) species induces important changes in the reactivity and electronic state of the perovskite, while little or no changes can be detected in the formal oxidation state of cobalt atoms. The presence of strontium cations induces two main effects in the chemical and electronic behavior of the perovskite. The charge balance with Sr(II) species is reached by the formation of oxygen vacancies throughout the network, which increases the reactivity of the perovskite, now more reducible than the original LaCoO{sub 3} perovskite. O K-edge XAS experiments indicate that the Sr(II) species cause d electrons of cobalt cations to change from low to high spin configuration. Our data allow us to propose that this change in spin multiplicity is induced by the bigger size of Sr(II) cations, which aligns the Co-O-Co atoms, and favors the overlapping of {pi}-symmetry cobalt and oxygen orbitals, reducing the splitting energy of e{sub g} and t{sub 2g} levels.
Date: February 6, 2009
Creator: Hueso, Jose L.; Holgado, Juan P.; Pereniguez, Rosa; Mun, Simon; Salmeron, Miquel & Caballero, Alfonso
System: The UNT Digital Library
Analysis of the Wakefield Effects in the PEP-II SLAC B-FACTORY (open access)

Analysis of the Wakefield Effects in the PEP-II SLAC B-FACTORY

We present the history and analysis of different wake field effects throughout the operational life of the PEP-II SLAC B-factory. Although the impedance of the high and low energy rings is small, the intense high current beams generated a lot of power. The effects from these wake fields are: heating and damage of vacuum beam chamber elements like RF seals, vacuum valves , shielded bellows, BPM buttons and ceramic tiles; vacuum spikes, vacuum instabilities and high detector background; beam longitudinal and transverse instabilities. We also discuss the methods used to eliminate these effects. Results of this analysis and the PEP-II experience may be very useful in the design of new storage rings and light sources.
Date: July 6, 2009
Creator: Novokhatski, A; Seeman, J.; Sullivan, M.; Wienands, U. & /SLAC
System: The UNT Digital Library
DEVELOPING A SPATIAL DATA INFRASTRUCTURE FOR THE HANFORD SITE (open access)

DEVELOPING A SPATIAL DATA INFRASTRUCTURE FOR THE HANFORD SITE

Summary of this report is: (1) aggressive implementation of metadata; (2) higher confidence in spatial data and organizational structure; (3) improved data sharing between Hanford and neighboring government agencies; and (4) improved data sharing and management reduce unnecessary cost to DOE and the American taxpayer.
Date: November 6, 2009
Creator: SF, RUSH
System: The UNT Digital Library
Beam Diagnostic by Outside Beam Chamber Fields (open access)

Beam Diagnostic by Outside Beam Chamber Fields

Fields induced by a beam and penetrated outside the beam pipe can be used for a beam diagnostic. Wires placed in longitudinal slots in the outside wall of the beam pipe can work as a beam pickup. This has very small beam-coupling impedance and avoids complications of having a feed-through. The signal can be reasonably high at low frequencies. We calculate the beam-coupling impedance due to a long longitudinal slot in the resistive wall and the signal induced in a wire placed in such a slot and shielded by a thin screen from the beam. We present a field waveform at the outer side of a beam pipe, obtained as a result of calculations and measurements. Such kind of diagnostic can be used in storage rings, synchrotron light sources, and free electron lasers, like LINAC coherent light source.
Date: July 6, 2009
Creator: Novokhatski, A; Heifets, S. & Aleksandrov, A.
System: The UNT Digital Library
Thermodynamics of Neptunium (V) Complexes with Phosphate at Elevated Temperatures (open access)

Thermodynamics of Neptunium (V) Complexes with Phosphate at Elevated Temperatures

None
Date: April 6, 2009
Creator: Xia, Yuanxian; Friese, Judah I.; Bachelor, Paula P.; Moore, Dean A. & Rao, Linfeng
System: The UNT Digital Library
Longitudinal Beam Stability in the SUPER B-FACTORY* (open access)

Longitudinal Beam Stability in the SUPER B-FACTORY*

We give an overview of wake fields and impedances in a proposed Super B project, which is based on extremely low emittance beams colliding at a large angle with a crab waist transformation. Understanding the effects that wake fields have on the beam is critical for a successful machine operation. We use our combined experience from the operation of the SLAC B-factory and DA{Phi}NE {Phi}-factory to eliminate strong HOM sources and minimize the chamber impedance in the Super B design. Based on a detailed study of the wake fields in this design we have developed a quasi-Green's function for the entire ring that is used to study bunch lengthening and beam stability. In particular, we check the stability threshold using numerical solutions of the Fokker-Plank equation. We also make a comparison of numerical simulations with the bunch lengthening data in the B- factory.
Date: July 6, 2009
Creator: Novokhatski, A. & Zobov, M.
System: The UNT Digital Library
Reversibility Aspect of Metal Borohydrides (open access)

Reversibility Aspect of Metal Borohydrides

None
Date: April 6, 2009
Creator: Au, M. & Tom Walters, T.
System: The UNT Digital Library
Results from the CLIC X-Band Structure Test Program at NLCTA (open access)

Results from the CLIC X-Band Structure Test Program at NLCTA

As part of a SLAC-CERN-KEK collaboration on high gradient X-band structure research, several prototype structures for the CLIC linear collider study have been tested using two of the high power (300 MW) X-band rf stations in the NLCTA facility at SLAC. These structures differ in terms of their fabrication (brazed disks and clamped quadrants), gradient profile (amount by which the gradient increases along the structure, which optimizes efficiency and maximizes sustainable gradient) and HOM damping (use of slots or waveguides to rapidly dissipate dipole mode energy). The CLIC goal in the next few years is to demonstrate the feasibility of a CLIC-ready baseline design and to investigate alternatives that could increase efficiency. This paper summarizes the high gradient test results from NLCTA in support of this effort.
Date: July 6, 2009
Creator: Adolphsen, Chris; Bowden, Gordon; Dolgashev, Valery; Laurent, Lisa; Tantawi, Sami; Wang, Faya et al.
System: The UNT Digital Library
HYDROGEN STORAGE SOLUTIONS IN SUPPORT OF DOD WARFIGHTER PORTABLE POWER APPLICATIONS (open access)

HYDROGEN STORAGE SOLUTIONS IN SUPPORT OF DOD WARFIGHTER PORTABLE POWER APPLICATIONS

From Personal Digital Assistants (PDAs) to cell phones our high-tech world, today, is demanding smaller, lighter weight and higher capacity portable power devices. Nowhere has this personal power surge been more evident than in today's U.S Warfighter. The modern Warfighter is estimated to carry from 65 to 95 pounds of supplies in the field with over 30 pounds of this dedicated to portable power devices. These devices include computer displays, infrared sights, Global Positioning Systems (GPS), night vision and a variety of other sensor technologies. Over 80% of the energy needed to power these devices comes from primary (disposable) batteries. It is estimated that a brigade will consume as much as 7 tons of batteries in a 72 hour mission at a cost of $700,000. A recent comprehensive study on the energy needs of the future warrior published by the National Academy of Science in 2004 made a variety of recommendations for average power systems from 20 to 1,000 watts. For lower power systems recommendations included pursuing science and technology initiatives focused on: (1) 300 watt-hours per kilogram (Wh/kg) secondary battery technologies; (2) smart hybrids; and (3) fuel cells (with greater than 6 wt% hydrogen storage). Improved secondary (rechargeable) batteries …
Date: January 6, 2009
Creator: Motyka, T.
System: The UNT Digital Library
Klystron Cluster Scheme for ILC High Power RF Distribution (open access)

Klystron Cluster Scheme for ILC High Power RF Distribution

We present a concept for powering the main linacs of the International Linear Collider (ILC) by delivering high power RF from the surface via overmoded, low-loss waveguides at widely spaced intervals. The baseline design employs a two-tunnel layout, with klystrons and modulators evenly distributed along a service tunnel running parallel to the accelerator tunnel. This new idea eliminates the need for the service tunnel. It also brings most of the warm heat load to the surface, dramatically reducing the tunnel water cooling and HVAC requirements. In the envisioned configuration, groups of 70 klystrons and modulators are clustered in surface buildings every 2.5 km. Their outputs are combined into two half-meter diameter circular TE{sub 01} mode evacuated waveguides. These are directed via special bends through a deep shaft and along the tunnel, one upstream and one downstream. Each feeds approximately 1.25 km of linac with power tapped off in 10 MW portions at 38 m intervals. The power is extracted through a novel coaxial tap-off (CTO), after which the local distribution is as it would be from a klystron. The tap-off design is also employed in reverse for the initial combining.
Date: July 6, 2009
Creator: Nantista, Christopher & Adolphsen, Chris
System: The UNT Digital Library
Crystal structure of Thermotoga maritima TM0439: implications for the mechanism of bacterial GntR transcription regulators with Zn2+-binding FCD domains (open access)

Crystal structure of Thermotoga maritima TM0439: implications for the mechanism of bacterial GntR transcription regulators with Zn2+-binding FCD domains

The GntR superfamily of dimeric transcription factors, with more than 6200 members encoded in bacterial genomes, are characterized by N-terminal winged helix (WH) DNA-binding domains and diverse C-terminal, regulatory domains, which provide a basis for the classification of the constituent families. The largest of these families, FadR, contains nearly 3000 proteins with all a-helical regulatory domains classified into two related Pfam families: FadR{_}C and FCD. Only two crystal structures of the FadR family members, i.e. the E. coli FadR protein and the LldR from C. glutamicum, have been described to date in literature. Here we describe the crystal structure of TM0439, a GntR regulator with an FCD domain, found in the Thermotoga maritima genome. The FCD domain is similar to that of the LldR regulator, and contains a buried metal binding site. Using atomic absorption spectroscopy and Trp fluorescence, we show that the recombinant protein contains bound Ni{sup 2+} ions, but it is able to bind Zn{sup 2+} with K{sub D} < 70 nM . We conclude that Zn{sup 2+} is the likely physiological metal, where it may perform either or both structural and regulatory roles. Finally, we compare the TM0439 structure to two other FadR family structures recently deposited …
Date: June 6, 2009
Creator: Zheng, Meiying; Cooper, David; Grossoehmerb, Nickolas; Yu, Minmin; Hung, Li-Wei; Cieslik, Murcin et al.
System: The UNT Digital Library
The Effect of an Oxide Layer on Resistive-Wall Wakefields (open access)

The Effect of an Oxide Layer on Resistive-Wall Wakefields

Shorter and shorter electron bunches are now used in the FEL designs. The fine structure of the wall of a beam vacuum pipe plays more noticeable role in the wake field generation. Additionally to the resistance and roughness, the wall may have an oxide layer, which is usually a dielectric. It is important for aluminium pipe, which have Al2O3 layer. The thickness of this layer may vary in a large range: 1-100 nm. We study this effect for the very short (20-1000 nm) ultra relativistic bunches in an infinite round pipe. We solved numerically the Maxwell equations for the fields in the metal and ceramics. Results showed that the oxide layer may considerably increase the wavelength and the decay time of the resistive-wall wake fields, however the loss factor of the very short bunches does not change much.
Date: July 6, 2009
Creator: Novokhatski, A.
System: The UNT Digital Library