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Model of beam head erosion

Description: An analytical model of beam head dynamics is presented, leading to an estimate of the erosion rate due to the combined effects of Ohmic dissipation and scattering. Agreement with the results of a computer simulation and detailed one-dimensional computations is good in all respects except for the scaling of the erosion rate with net current.
Date: August 8, 1980
Creator: Lee, E.P.
Partner: UNT Libraries Government Documents Department

Sausage mode of a pinched charged particle beam

Description: The axisymmetric oscillations of a self-pinched charged particle beam are analyzed using a dispersion relation derived from a 3/2 dimensional model. This calculation includes the effects of rounded profiles, finite conductivity, a steady return current, and phase mix damping among particle orbits. However, only the lowest order radial mode of distortion is treated, and this is done in an approximate fashion.
Date: February 10, 1981
Creator: Lee, E.P.
Partner: UNT Libraries Government Documents Department

Thermal cooling of a cylindrical gas bubble

Description: An analytic calculation of the cooling by thermal conduction of a hot, cylindrically symmetric gas bubble is presented. The results are in good agreement with an exact numerical calculation. 1 figure, 4 tables.
Date: August 14, 1978
Creator: Lee, E.P.
Partner: UNT Libraries Government Documents Department

Gaussian-profile beams

Description: The growth rate of the hose instability is derived for a beam with Gaussian radial profile, using the spread mass model of phase mix damping. It is found that the maximum growth rate of a convecting wave packet is 49% larger than that derived for a beam with the Bennett profile, and the inverse group velocity (dz/d tau) is also increased by about this amount. A general discussion of spread mass models is presented along with an explanation of the regurgitation phenomena seen in their numerical treatment.
Date: November 3, 1982
Creator: Lee, E.P.
Partner: UNT Libraries Government Documents Department

Filamentation during final transport in a high pressure gas

Description: The filamentation instability has been identified as a possible pathology afflicting final transport even when gas pressure is high enough to eliminate the two-stream mode. This phenomenon is characterized by the spontaneous appearance of many narrow magnetic pinches within the pulse, with a corresponding increase in transverse temperature and emittance. If the time of flight of an ion exceeds one magnetic plasma period of the beam, then there is a danger of filamentation. However, large electrical conductivity (generated by the passage of the beam through the gas) inhibits mode growth for a pulse of finite duration. In addition, transverse thermal velocity damps perturbations of small transverse dimension, and therefore also acts to suppress mode growth. These ideas are developed here in a brief analytical treatment.
Date: December 1, 1978
Creator: Lee, E.P.
Partner: UNT Libraries Government Documents Department

Calculation of a tracking force

Description: The original calculation (1975-76) of an electromagnetic mechanism for beam-channel tracking is presented. The system model is not realistic because only a flat profile channel which completely encloses the beam is considered. However, a clear demonstration of the existence of a tracking force is made, as a point of departure for the more recent studies which incorporate a realistic model of the beam head and conductivity profile.
Date: January 10, 1983
Creator: Lee, E.P.
Partner: UNT Libraries Government Documents Department

Model equations for high current transport

Description: The use of distribution functions to model transverse beam dynamics is discussed. Emphasis is placed on envelope equations, moments, the Vlasov equation, and the Kapchinski-Vladimirskij distribution. 10 refs.
Date: June 1, 1985
Creator: Lee, E.P.
Partner: UNT Libraries Government Documents Department

High temperature experiment for accelerator inertial fusion

Description: The High Temperature Experiment (HTE) is intended to produce temperatures of 50 to 100 eV in solid density targets driven by heavy ion beams from a multiple beam induction linac. The fundamental variables (particle species, energy, number of beamlets, current and pulse length) must be fixed to achieve the temperature at minimum cost, subject to criteria of technical feasibility and relevance to the development of a Fusion Driver. The conceptual design begins with an assumed (radiation-limited) target temperature and uses limitations due to particle range, beamlet perveance, and target disassembly to bound the allowable values of mass number (A) and energy (E). An accelerator model is then applied to determine the minimum length accelerator, which is a guide to total cost. The accelerator model takes into account limits on transportable charge, maximum gradient, core mass per linear meter, and head-to-tail momentum variation within a pulse.
Date: May 1, 1985
Creator: Lee, E.P.
Partner: UNT Libraries Government Documents Department

Resistance-driven bunching mode of an accelerated ion pulse

Description: Amplification of a longitudinal perturbation of an ion pulse in a linear induction accelerator is calculated. The simplified accelerator model consists only of an applied field (E/sub a/), distributed gap impedance per meter (R) and beam-pipe capacity per meter (C). The beam is treated as a cold, one-dimensional fluid. It is found that normal mode frequencies are nearly real, with only a very small damping rate proportional to R. This result is valid for a general current profile and is not restricted to small R. However, the mode structure exhibits spatial amplification from pulse head to tail by the factor exp(RCLv/sub o//2), where L is pulse length and v/sub 0/ is drift velocity. This factor is very large for typical HIF parameters. An initially small disturbance, when expanded in terms of the normal modes, is found to oscillate with maximum amplitude proportional to the amplification factor.
Date: October 16, 1981
Creator: Lee, E.P.
Partner: UNT Libraries Government Documents Department

Radiation damping of betatron oscillations

Description: The emission of synchrotron radiation damps the incoherent betatron oscillations of a pinched beam, causing its radius to shrink. However, the rate of shrinkage is small compared with the rate of expansion caused by scattering for typical propagation parameters.
Date: April 20, 1982
Creator: Lee, E.P.
Partner: UNT Libraries Government Documents Department

Accelerator and final focus model for an induction Linac based HIF system study

Description: An overview of the assumptions and models incorporated in the ongoing Induction-Linac-based, HIF System Assessment is presented. Final transport, compression and final focus pose constraints which form a critical link between the accelerator and target requirements. A recent analysis has shown that system costs may be considerably reduced by the use of multiply charges ions. The assumptions underlying this direction are described.
Date: July 1, 1986
Creator: Lee, E.P.
Partner: UNT Libraries Government Documents Department

Transport of intense ion beams. [HIBALL II]

Description: The maximum transportable current for an ion beam is determined by considerations of focal strength, space charge equilibrium and stability, structural practically and emittance. These factors are described within the context of a heavy ion driver for Inertial Confinement Fusion. Recent supporting results from particle-in-cell simulations and transport experiments will be described.
Date: June 1, 1986
Creator: Lee, E.P.
Partner: UNT Libraries Government Documents Department

Determination of the radius of a self-pinched beam from its energy integral

Description: The total transverse energy (kinetic plus potential) of a self-pinched beam may be used to predict the final equilibrium radius when the beam is mismatched at injection. The dependence of potential energy on the current profile shape is characterized by a dimensionless parameter C(z), variations of which are correlated with the change of emittance.
Date: January 2, 1980
Creator: Lee, E.P.
Partner: UNT Libraries Government Documents Department

Velocity distribution in a pinched beam

Description: An explicity procedure is given for distributing transverse velocities to simulate a self pinched beam of specified density profile. The flat top, Bennett and Gaussian profiles are worked examples.
Date: September 17, 1979
Creator: Lee, E.P.
Partner: UNT Libraries Government Documents Department

Achromatic beam combiner and bend system for ILSE (Induction Linac System Experiment)

Description: The lattice configuration of the beam combiner and bend system of the proposed Induction Linac System Experiment (ILSE) is described. These subsystems must transport high current ion beams with large momentum variations within a single pulse (..delta..P/P/sub 0/ less than or equal to +-.1), with minimal beam loss or emittance growth. Configurations which are achromatic through first order, including the effect of image fields have been developed. Calculations of the beam envelope and centroid motion are made with beam dynamics code HICURB, which includes strong space charge effects and chromatic effects through all orders. 5 refs., 5 figs.
Date: June 1, 1988
Creator: Lee, E.P.
Partner: UNT Libraries Government Documents Department

P Division monthly report, May 1949

Description: This progress report discusses activities for the P Division for the month of May 1949. The nominal operating level for both B and F Piles was 275 megawatts (MW) throughout the month except for outages listed under Area Activities. The D Pile operated at 275 MW until May 23 when the nominal level was raised to 290 MW in the first step of the program covered in Production Test No. 105-260-P to evaluate the feasibility of operating piles at higher power levels. A total of 44 tons of metal, at an average concentration of 285 megawatt days/ton (MWD/ton), was discharged from the piles during the month. Considerable difficulty was experienced during the month with stuck tubes containing Class IV (alpha-rolled, triple-dipped, randomly transformed) metal. A total of nine tubes with concentrations in the range of 320--370 MV/ton was encountered. As a result of these difficulties with the Class IV material, future discharges of this type metal will be limited to concentrations in the range 300--320 MWD. Approximately one ton of Class V (alpha-rolled, triple-dipped, completely transformed) metal was discharged at a concentration of 368 MV/ton for test purposes. Inspection of this material indicated that all the slugs were in satisfactory condition. All three piles were scheduled down on May 4 and May 25 to allow the Electrical Division to make a tie-in to the 230 KV lines for 100-H Area.
Date: June 15, 1949
Creator: Lee, E.P.
Partner: UNT Libraries Government Documents Department

P Division monthly report, December 1948

Description: This progress report discusses activities at the P Division for the month of December 1948. All piles operated at 275 megawatts throughout the month except for the outages listed under Area activities in this report. An unscheduled power outage occurred in the 300 Area on December 2. No difficulties were encountered except for the lost operating time. A total of 103 tons of metal was discharged from the piles during the month. Operating schedules in the 300 Area were reduced from a six-day week to a five-day week on December 20 because of the favorable status of the inventory of canned slugs. All processes are now working one shift a day except Canning and Machining which work two shifts a day.
Date: January 14, 1949
Creator: Lee, E.P.
Partner: UNT Libraries Government Documents Department

P Division monthly report, September 1949

Description: This progress report discusses the activities of the P Division for the month of September, 1949. The B and F piles operated at 275 megawatts (MW) and the D pile at 305 MW throughout the month except for cutages listed under Area Activities. A total of 60.22 tons of metal, at an average concentration of 396 megawatt days/ton (MWD/ton) was discharged from the piles during the month. The 105-H Building was accepted from the Construction Division on September 28 with certain exceptions noted under the Operating Experience section of this report. At month end P Division operating personnel are making preparations for activation of the H pile. On September 28 the operation of the 300 Area oxide burning process was reduced from a two shift to a one shift five day operation. This change in schedule was possible as a result of working off the backlog of uranium oxide. The shipment of 200 tons of canned slugs to Building 105-DR for storage was completed on September 9 and the shipment of 250 tons of canned slugs to Building 105-H for the initial loading charge was completed on September 26.
Date: October 6, 1949
Creator: Lee, E.P.
Partner: UNT Libraries Government Documents Department

P Division monthly report, March 1949

Description: This progress report discusses activities at P Division for the month of March, 1949. All piles operated at 275 megawatts throughout the month except for the outages listed under Area Activities in this report. The average time operating efficiency''was 91.4%. A total of 47 tons of metal was discharged from the piles during the month. During the month, 16.6 tons of alpha-rolled, triple-dipped metal were discharged without difficulty at a nominal concentration of 320 megawatts day (MWD) per ton. Inspection of selected tubes of this material indicated that exposures at this level are satisfactory. In view of these results the programs of stepwise increases in concentration will be continued, with the next test tonnages being discharged at a nominal concentration of 360 MWD per ton. The nominal monthly production rate of acceptable canned pieces was reduced from 90 tons to 60 tons on March 28. This curtailment of production was possible in view of the favorable inventory of slugs available for charging DR and H piles.
Date: April 14, 1949
Creator: Lee, E.P.
Partner: UNT Libraries Government Documents Department

P Division monthly report, July 1949

Description: The progress report discusses activities of the P Division for the month of July, 1949. The B and F piles operated at 275 megawatts and the D pile at 305 megawatts throughout the month except for outages listed under Area Activities. A total of 57.5 tons of metal, at an average concentration of 363 megawatt days/ton (MWD/ton) was discharged from the piles during the month. This included 41.9 tons of Class V (alpha-rolled, triple-dipped, completely transformed) metal at an average concentration of 397 MWD/ton which was discharged without difficulty. A portion of this material was inspected and appears to be satisfactory for exposures at this concentration.
Date: August 5, 1949
Creator: Lee, E.P.
Partner: UNT Libraries Government Documents Department

Fringe fields for the N channel permanent magnet array

Description: Analytical expressions are obtained for fringe field multipoles of an N channel permanent magnet quadrupole array. It is assumed that the system of magnetic wedges starts at some transverse (x, y) plane located at z = 0, and it continues to a magnet length z = l, where it stops. The iron yoke continues to z = {+-} {infinity}, but it will be shown that only a small overhang is actually required to maintain the quadrupole and translational symmetries. Recall the 2-d solution for the magnetic potential (H = {del}{phi}): {phi}{sub 2} = A [(x-x{sub i}){sup 2} - (y-y{sub i}){sub 2}], where A = -M{sub 0}/4b, M{sub 0} is the remnant field of the wedges, and (x{sub i}, y{sub i}) are the coordinates for the center of box (i). Boxes have dimensions 2b x 2b and alternate between vacuum fill (for beams) and magnetic wedge fill. The 2-d system looks like a portion of an infinite transverse lattice with periodicity lengthy = 4b in both the x and y directions. For the magnetic potential {phi}, the periodicity length is 2b.
Date: April 1, 1996
Creator: Lee, E.P.
Partner: UNT Libraries Government Documents Department

The beam envelope equation-systematic solution for a periodic quadrupole lattice with space charge

Description: Many approximate solutions for matched beam envelope functions with space charge have been developed; they generally have errors of 2-10% for the parameters of interest and cannot be reliably improved. The new, systematic approach described here provides the K-V envelope functions to high accuracy as a power series in the quadrupole gradient. A useful simplification results from defining the sum and difference of the envelope radii; S = (a+b)/2 varies only slightly with distance z along the system axis, and D = (a-b)/2 contains most of the envelope oscillations. To solve the coupled equations for S and D, the quadrupole strength K(z) is turned on by replacing K with {alpha}K{sub 1} and letting {alpha} increase continuously from 0 to 1. It is found that S and D may be expanded in even and odd powers of {alpha}, respectively. Equations for the coefficients of powers of {alpha} are then solved successively by integration in z. The periodicity conditions and tune integration close the calculation. Simple low order results are typically accurate to 1% or better.
Date: April 1, 1995
Creator: Lee, E.P.
Partner: UNT Libraries Government Documents Department