J. Harrison

Initial electron-beam results from the DARHT-II linear induction accelerator

The DARHT-II linear-induction accelerator has been successfully operated at 1.2-1.3 kA and 12.5-12.7 MeV to demonstrate the production and acceleration of an electron beam. Beam pulse lengths for these experiments were varied from 0.5 /spl mu/s to 1.2 /spl mu/s full-width half-maximum. A low-frequency inductance-capacitance (LC) oscillation of diode voltage and current resulted in an oscillation of the beam position through interaction with an accidental (static) magnetic dipole in the diode region. There was no growth in the amplitude of this oscillation after propagating more than 44 m through the accelerator, and there was no loss of beam current that could be measured. The results of these initial experiments are presented in this paper.

Long-pulse beam stability experiments on the DARHT-II linear induction accelerator

When completed, the DARHT-II linear induction accelerator (LIA) will produce a 2-kA, 17-MeV electron beam in a 1600-ns flat-top pulse. In initial tests, DARHT-II accelerated beams with current pulse lengths from 500 to 1200 ns full-width at half-maximum (FWHM) with more than 1.2-kA, 12.5-MeV peak current and energy. Experiments have now been done with a /spl sim/1600-ns pulse length. These pulse lengths are all significantly longer than any other multimegaelectronvolt LIA, and they define a novel regime for high-current beam dynamics, especially with regard to beam stability. Although the initial tests demonstrated insignificant beam-breakup instability (BBU), the pulse length was too short to determine whether ion-hose instability would be present toward the end of a long, 1600-ns pulse. The 1600-ns pulse experiments reported here resolved these issues for the long-pulse DARHT-II LIA.

Microcomputer Based Dual Energy Photon Absorptiometric Bone Mineral Analyzer (VCH)

Measurement of mineral content in trabecular bone with reproducible precision can have significant effect on patient management with osteopenic conditions. Commercial instruments measure single cross sections of the upper extremity which, unless uniform bone sections are measured, produce large errors. Forearm bones, that are primarily cortical and therefore less reflective of rapid bone turnover, are usually measured. Utilizing experience gained with rectilinear scanning for large area mineral estimation on Apollo and Skylab astronauts, we designed hardware and software that is compact, can use single or dual photon sources in a rectilinear fashion with precise repositioning, scan in a vertical or horizontal plane, perform on-line data storage and reduction, and provide continuous visual evaluation of the data profile.

First beam at DARHT-II

The second axis of the Dual Axis Radiographic HydroTest (DARHT) facility will provide up to four short (< 150 ns) radiation pulses for flash radiography of high-explosive driven implosion experiments. To accomplish this the DARHT-II linear induction accelerator (LIA) will produce a 2-kA electron beam with 18-MeV kinetic energy, constant to within /spl plusmn/ 0.5% for 2-/spl mu/s. A fast kicker will cleave four short pulses out of the 2-/spl mu/s flattop, with the bulk of the beam diverted into a dump. The short pulses will then be transported to the final-focus magnet, and focused onto a tantalum target for conversion to bremsstrahlung pulses for radiography. DARHT-II is a collaborative effort between the Los Alamos, Lawrence Livermore, and Lawrence Berkeley National Laboratories of the University of California.

Design of the RSX11M Q System

The present LAMPF Q data acquisition/analysis software system is being converted to run under the RSX-1lM operating system. Major subsystems have been redesigned to be compatible with RSX-11M and to provide enhanced functionality. In addition, two new major subsystems have been designed: a test package subsystem and a real-time parameter array subsystem.

Commissioning the darht-II scaled accelerator

When completed, the DARHT-II accelerator will produce a 2-kA, 17-MeV beam in a 1600-ns pulse. After exiting the accelerator, the long pulse will be sliced into four short pulses by a kicker and quadrupole septum and then transported for several meters to a tantalum target for conversion to bremsstrahlung for radiography. In order to provide early tests of the kicker, septum, transport, and multi-pulse converter target we assembled a short accelerator from the first available refurbished cells, which are now capable of operating of operating at over 200 kV. This scaled accelerator was operated at ~8 MeV and ~1 kA, which provides a beam with approximately the same beam dynamics in the downstream transport as the final 17-MeV, 2-kA beam.

Commissioning the DARHT-II scaled accelerator downstream transport

The DARHT-II accelerator will produce a 2-kA, 17-MeV beam in a 1600-ns pulse when completed mid-2007. After exiting the accelerator, the pulse is sliced into four short pulses by a kicker and quadrupole septum and then transported for several meters to a tantalum target for conversion to X-rays for radiography. We describe tests of the kicker, septum, transport, and multi-pulse converter target using a short accelerator assembled from the first available refurbished cells. This scaled accelerator was operated at ~8 MeV and ~1 kA, providing a beam with approximately the same v/gamma as the final 18-MeV, 2-kA beam, and therefore the same beam dynamics in the downstream transport. The results of beam measurements made during the commissioning of this scaled accelerator downstream transport are described.

The status of the LAMPF control system upgrade

Abstract This paper discusses the present state of the LAMPF accelerator control computer upgrade. This includes a summary of our recent operational experience and the status of the application programs in the new system. In addition, we describe several optimization techniques which have been used to improve system-wide performance, and a limited VAX/VMS operating system environment which has been made available to the accelerator operators. We also describe our plans for upgrading the LAMPF control system computer network.

Performance Results for the New RSX-11M Q System

The new RSX-11M version of the Q data acquisition and data replay system has been in use for approximately one year. The structure and flow of data through the system is described. Performance data is presented on the Q system event acquisition, event distribution, histogramming, data testing and tape writing.

The Q Memory Resident Histogramming System

The LAMPF Data Acquisition System Q includes a subsystem to allow the user to create, delete, enter data in and retrieve data from histograms stored in memory. The system is implemented on PDP-11 computers under RSX-IlM V4.0 as an I/O driver with user-callable subroutines interfacing to the driver. A system with an identical user interface will soon be available on VAX computers under VMS V3.2.