The Visa Fel Undulator (open access)

The Visa Fel Undulator

The Visible-Infrared SASE Amplifier (VISA) FEL is an experimental device designed to show Self Amplified Spontaneous Emission (SASE) to saturation in the visible light energy range. It will generate a resonant wavelength output from 800--600 nm, so that silicon detectors may be used to characterize the optical properties of the FEL radiation. VISA is the first SASE FEL designed to reach saturation, and its diagnostics will provide important checks of theory. This paper includes a description of the VISA undulator, the magnet measuring and shimming system, and the alignment strategy. VISA will have a 4 m pure permanent magnet undulator comprising four 99 cm segments, each with 55 periods of 18 mm length. The undulator has distributed focusing built into it, to reduce the average beta function of the 70--85 MeV electron beam to about 30 cm. There are four FODO cells per segment. The permanent magnet focusing lattice consists of blocks mounted on either side of the electron beam, in the undulator gap. The most important undulator error parameter for a free electron laser is the trajectory walkoff or lack of overlap of the photon and electron beams. Using pulsed wire magnet measurements and magnet shimming, the authors expect …
Date: August 16, 1998
Creator: Carr, R.; Cornacchia, M.; Emma, P.; Nuhn, H. D.; Fuland, R.; Johnson, E. et al.
Object Type: Article
System: The UNT Digital Library
Wall-confined high beta spheromak (open access)

Wall-confined high beta spheromak

The spheromak could be extended into the high beta regime by supporting the pressure on flux-conserving walls, allowing the plasma to be in a Taylor state with zero pressure gradient and thus stable to ideal and resistive MHD. The concept yields a potentially attractive, pulsed reactor which would require no external magnets. The flux conserver would be shaped to be stable to the tilt and shift instabilities. We envision a plasma which is ohmically ignited at low beta, with the kinetic pressure growing to beta > 1 by fueling from the edge. The flux conserver would be designed such that the magnetic decay time = the fusion burn time. The thermal capacity of the flux conserver and blanket would exceed the fusion yield per discharge, so that they can be cooled steadily. Ignition is estimated to require minimum technology: 30-100 MJ of pulsed power applied at a 0.5 GW rate generates an estimated bum yield > 1 GJ. The concept thus provides an alternate route to a fusion plasma that is MHD stable at high beta, yielding a reactor that is simple and cheap. The major confinement issue is transport due to grad(T), e.g. driven by high beta modes related …
Date: March 16, 1998
Creator: Fowler, T. K.; Hopper, E. B.; Moir, R. W. & Pearlstein, L. D.
Object Type: Article
System: The UNT Digital Library
Waste form development and characterization in pyrometallurgical treatment of spent nuclear fuel. (open access)

Waste form development and characterization in pyrometallurgical treatment of spent nuclear fuel.

Electrometallurgical treatment is a compact, inexpensive method that is being developed at Argonne National Laboratory to deal with spent nuclear fuel, primarily metallic and oxide fuels. In this method, metallic nuclear fuel constituents are electrorefined in a molten salt to separate uranium from the rest of the spent fuel. Oxide and other fuels are subjected to appropriate head end steps to convert them to metallic form prior to electrorefining. The treatment process generates two kinds of high-level waste--a metallic and a ceramic waste. Isolation of these wastes has been developed as an integral part of the process. The wastes arise directly from the electrorefiner, and waste streams do not contain large quantities of solvent or other process fluids. Consequently, waste volumes are small and waste isolation processes can be compact and rapid. This paper briefly summarizes waste isolation processes then describes development and characterization of the two waste forms in more detail.
Date: April 16, 1998
Creator: Ackerman, J.
Object Type: Article
System: The UNT Digital Library
What is the symmetry of the high T{sub c} order parameter? (open access)

What is the symmetry of the high T{sub c} order parameter?

In recent years, there has been a raging controversy regarding the orbital symmetry of the superconducting order parameter (OP) in the high temperature superconductors. Many experiments were interpreted in terms of a d{sub x{sup 2}-y{sup 2}}-wave OP, but many others were interpreted in terms of a more conventional s-wave OP. We review the problems of both intrinsic and extrinsic natures with the phase-sensitive experiments on YBCO. The authors further show that the photoemission experiments of the purported superconducting gap in Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub g+{delta}} are entirely consistent with charge- and/or spin-density wave formation in that material. The presence of such density waves greatly complicates the analysis of most experiments. Hence, we conclude that the orbital symmetry of the superconducting OP is still unknown in any of the high temperature superconductors.
Date: April 16, 1998
Creator: Klemm, R. A.
Object Type: Article
System: The UNT Digital Library
YUCCA MOUNTAIN SITE CHARACTERIZATION PROJECT (open access)

YUCCA MOUNTAIN SITE CHARACTERIZATION PROJECT

None
Date: January 16, 1998
Creator: United States. Department of Energy.
Object Type: Report
System: The UNT Digital Library
D-Zero Cryogenic System VLPC & Solenoid Vacuum System Instrumentation, Control, and Logic (open access)

D-Zero Cryogenic System VLPC & Solenoid Vacuum System Instrumentation, Control, and Logic

The DZERO VLPC Cryostat and the Superconducting Solenoid both require an insulating Vacuum of 10{sup -5} Torr or less. There is a vacuum system on the Detector Platform consisting of 2 Turbomolecular vacuum pumps and their associated piping, valves, instrumentation that are dedicated to this task. This vacuum equipment requires an operator interface and control logic in order to function properly. The operator interface allows an operator to monitor, control and configure the proper pumping setup required at any given time. The control logic is needed to protect the Vacumm vessels and Vacuum equipment from catastrophic events that may harm them. This is typically done with interlock chains or strings.
Date: January 16, 1998
Creator: Markley, D.
Object Type: Report
System: The UNT Digital Library
Zinc Bromide Combustion: Implications for the Consolidated Incinerator Facility (open access)

Zinc Bromide Combustion: Implications for the Consolidated Incinerator Facility

In the nuclear industry, zinc bromide (ZnBr2) is used for radiation shielding. At Savannah River Site (SRS) zinc bromide solution, in appropriate configurations and housings, was used mainly for shielding in viewing windows in nuclear reactor and separation areas. Waste stream feeds that will be incinerated at the CIF will occasionally include zinc bromide solution/gel matrices.The CIF air pollution systems control uses a water-quench and steam atomizer scrubber that collects salts, ash and trace metals in the liquid phase. Water is re-circulated in the quench unit until a predetermined amount of suspended solids or dissolved salts are present. After reaching the threshold limit, "dirty liquid", also called "blowdown", is pumped to a storage tank in preparation for treatment and disposal. The air pollution control system is coupled to a HEPA pre-filter/filter unit, which removes particulate matter from the flue gas stream (1).The objective of this report is to review existing literature data on the stability of zinc bromide (ZnBr2) at CIF operating temperatures (>870 degrees C (1600 degrees F) and determine what the combustion products are in the presence of excess air. The partitioning of the combustion products among the quencher/scrubber solution, bottom ash and stack will also be evaluated. …
Date: December 16, 1998
Creator: Oji, L.N.
Object Type: Report
System: The UNT Digital Library