Commissioning the DARHT-II scaled accelerator downstream transport

2013

Rev. Accl. Sci. Tech.

Particle beam radiography, which uses a variety of particle probes (neutrons, protons, electrons, gammas and potentially other particles) to study the structure of materials and objects noninvasively, is reviewed, largely from an accelerator perspective, although the use of cosmic rays (mainly muons but potentially also high-energy neutrinos) is briefly reviewed. Tomography is a form of radiography which uses multiple views to reconstruct a three-dimensional density map of an object. There is a very wide range of applications of radiography and tomography, from medicine to engineering and security, and advances in instrumentation, specifically the development of electronic detectors, allow rapid analysis of the resultant radiographs. Flash radiography is a diagnostic technique for large high-explosive-driven hydrodynamic experiments that is used at many laboratories. The bremsstrahlung radiation pulse from an intense relativistic electron beam incident onto a high-Z target is the source of these radiographs. The challenge is to provide radiation sources intense enough to penetrate hundreds of g/cm 2 of material, in pulses short enough to stop the motion of high-speed hydrodynamic shocks, and with source spots small enough to resolve fine details. The challenge has been met with a wide variety of accelerator technologies, including pulsed-power-driven diodes, air-core pulsed betatrons and high-current linear induction accelerators. Accelerator technology has also evolved to accommodate the experimenters' continuing quest for multiple images in time and space. Linear induction accelerators have had a major role in these advances, especially in providing multiple-time radiographs of the largest hydrodynamic experiments.

Section: Darht Axis-iimentioning

confidence: 99%

Section: Darht Axis-iimentioning

confidence: 99%

See 1 more Smart Citation

Particle Beam Radiography

Peach

2013

Rev. Accl. Sci. Tech.

“…The 2-kA, 20-MeV Axis-I LIA creates a single 60-ns radiography pulse. The 1.7-kA, 16.5-MeV Axis-II creates multiple radiography pulses by kicking them out of a 1600-ns long pulse from the LIA [3,4,5].…”

Section: Introductionmentioning

confidence: 99%

Emittance growth in the DARHT Axis-II Downstream Transport

Schulze

2015

Using a particle-in-cell (PIC) code, we investigated the possibilities for emittance growth through the quadrupole magnets of the system used to transport the high-current electron beam from an induction accelerator to the bremsstrahlung converter target used for flash radiography. We found that even highly mismatched beams exhibited little emittance growth (< 6%), which we attribute to softening of their initial hard edge current distributions. We also used this PIC code to evaluate the accuracy of emittance measurements using a solenoid focal scan following the quadrupole magnets. If the beam is round after the solenoids, the simulations indicate that the measurement is highly accurate, but it is substantially inaccurate for elliptical beams.

“…The injector voltage is about 2.1 MV. The Axis-II beam can be chopped into bunches for multipulse radiographic experiments [3,4,5]. This work refers specifically to Axis-II.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of methods to increase beam pulse width on the DARHT Axis-II accelerator

Rose

2013 19th IEEE Pulsed Power Conference (PPC)

Crawford

et al. 2013

The second axis (Axis II) of the Dual-Axis Radiographic Hydrodynamic Test (DARHT) facility at Los Alamos National Laboratory (LANL) is an electron linear induction accelerator (LIA) using 74 induction cells, each driven by a separate pulse-forming-networkbased Marx (PFN). The ability to perform precise multipulse radiography is heavily influenced by the temporal beam-energy spread, beam-pulse width, related beam motion, and other focusing and target factors. The nominal beam-pulse flattop width is about 1.6 µs. A wider beam pulse would allow for increased spacing between kicked pulses and hence more information in radiographic experiments. A flattop pulse-width increase of even 50 to 100 ns would be of significant value.In this paper, we present analyses, simulations and data for three low-cost, relatively easy means of lengthening the beam pulse for multipulse radiography. The first involves optimizing the PFN charging voltages such that their respective cell pulse widths are nearly the same. The second method studies the utility of timing the cell voltage pulses such that their trailing edges are aligned instead the leading edges. And the third method, presents experimental data on the effects of increasing the cell core reset currents which increases the available volt-second (V-s) products in the cores yielding increased pulse width.