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Rutherford scattering is used routinely for diagnostic purposes to reduce the intensity of ion beams in inertial-confinement-fusion experiments. A limitation of the scattering technique is the strong dependence of the Rutherford cross section on the scattering angle [σ ∞ 1/sin[sup 4] (θ[sub s]/2)] because the angular distribution of the beam ions is not precisely known and is difficult to measure. It is shown that this limitation can be overcome with the use of a thin scattering foil, and an analytic expression is derived that defines geometries for which the scattering probability is, to first order, independent of θ[sub s]. [ABSTRACT FROM AUTHOR]

A time-resolved magnetic spectrograph employing a gold Rutherford-scattering foil has been constructed to measure the parameters of the intense ion beams generated by Sandia National Laboratories' PBFA-II accelerator. The spectrograph operates by allowing the direct intense beam of PBFA-II to scatter from a thin gold foil to reduce its intensity for magnetic analysis. Details of the spectrograph's construction, detector package, and recent PBFA-II proton data are included in the paper. [ABSTRACT FROM AUTHOR]

We have developed a new ion pinhole camera to obtain energy density profiles of a focused multiterawatt ion beam as a function of ion energy. Beam ions that are elastically scattered from a thin gold foil are imaged through six baffled pinholes onto six separate areas of a sheet of CR-39 nuclear track detector. Each of the areas is covered by an aluminum range filter and records an image with a different lower bound on the ion energy. Subtracting images with adjacent cutoff energies results in images with upper and lower bounds on the ion energy. Ion images are read from the CR-39 with VERA, a fully automatic, image-processor-based nuclear track counting system. Images of the Particle Beam Fusion Accelerator-II (PBFA-II) proton beam have been obtained and show that the beam has been focused to achieve a horizontal FWHM of 5.7 mm and has delivered 9 kJ/cm² to a target. [ABSTRACT FROM AUTHOR]

A camera with a 3 ns time resolution and a continuous (> 100 ns) record length has been developed to image a 10[sup 12]-10[sup 13] W/cm² ion beam for inertial-confinement-fusion experiments. A thin gold Rutherford-scattering foil placed in the path of the beam scatters ions into the camera. The foil is in a near-optimized scattering geometry and reduces the beam intensity∼seven orders of magnitude. The scattered ions are pinhole imaged onto a 2D array of 39 p-i-n diode detectors; outputs are recorded on LeCroy 6880 transient-waveform digitizers. The waveforms are analyzed and combined to produce a 39-pixel movie which can be displayed on an image processor to provide time-resolved horizontal- and vertical-focusing information. [ABSTRACT FROM AUTHOR]

A time-resolved camera has been developed to image the intense ion beam focus on PBFA II. Focused ions from a sector of the ion diode are Rutherford scattered from a thin gold foil on the diode axis and pinhole imaged onto an array of up to 49 PIN detectors to obtain the spatially and temporally resolved images. The signals from these detectors are combined to provide a movie of the beam focus with a time resolution of about 3 ns and a spatial resolution of 2 mm over a 12 mm field of view. Monte Carlo simulations of the camera response are used with the measured ion energy to account for the time-of-flight dispersion of the beam and to convert the recorded signals to an intensity. From measurements on an 81° sector of the diode, average intensities on a 6 mm sphere of about 5 TW/cm² and energies approaching 80 kJ/cm² are calculated for standard proton diodes. Corresponding numbers for a lithium diode are less than those measured with protons. The details of the analysis and image reconstruction will be presented along with scaled images from recent ion focusing experiments. [ABSTRACT FROM AUTHOR]

A magnetic spectrograph employing a gold Rutherford scattering foil has been constructed and fielded on Sandia National Laboratories' PBFA-II accelerator to diagnose intense ion beams. The instrument simultaneously records time-integrated data on nuclear track recording film, CR-39, and time-resolved data on a set of p-i-n diodes. The details of the analysis of these data to provide time-resolved power density, ion current density, ion energy spectra (including mean ion energy), and ion species identification will be presented. [ABSTRACT FROM AUTHOR]

Inertial confinement fusion research efforts at Sandia National Laboratories center on generating and focusing high-intensity light ion beams on the Particle Beam Fusion Accelerator PBFA-II. A time-integrating three-frame ion beam spatial monitor was developed for these experiments to determine proton and lithium ion beam uniformity and orbit characteristics by imaging the ioninduced K[sub α] line radiation. The three views of the ion beam are made off axis in three diode quadrants at a 3.8-cm radius. This spatial monitor, in conjunction with other beam diagnostics, allows experimenters to determine the high-voltage focusing characteristics of the ion diode. [ABSTRACT FROM AUTHOR]

The 350-keV Cockroft-Walton accelerator at Sandia National laboratory's Ion Beam facility is being used to calibrate absolutely a total DT neutron yield diagnostic based on the 63Cu(n,2n)62Cu(β+) reaction. These investigations have led to first-order uncertainties approaching 5% or better. The experiments employ the associated-particle technique. Deuterons at 175 keV impinge a 2.6 μm thick erbium tritide target producing 14.1 MeV neutrons from the T(d,n)4He reaction. The alpha particles emitted are measured at two angles relative to the beam direction and used to infer the neutron flux on a copper sample. The induced 62Cu activity is then measured and related to the neutron flux. This method is known as the F-factor technique. Description of the associated-particle method, copper sample geometries employed, and the present estimates of the uncertainties to the F-factor obtained are given. [ABSTRACT FROM AUTHOR]

Ion beam divergence reduction will increase the power density deliverable to an ICF target and is one step towards demonstrating a credible path to target ignition, Measurement of the divergence is made with an ultracompact ion pinhole camera (UC-IPC). The UC-IPC is mounted in the PBFA II diode near the ion source at a 10° angle to compensate for beam bending in the diode's applied magnetic field. The beam is transported through an entrance pinhole and down an entrance tube to a gold scattering foil. The beam is scattered 90° through a second pinhole to CR39 film where the ion track count is recorded. This paper will describe the results of off-axis ion beam divergence measurements using the UC-IPC. Together with other diagnostics, the UC-IPC provides information about beam species and charge state, about particle energy and about divergence of the beam. This paper will also describe UC-IPC simulation using PICDIAG, a 2D code that models the ion transport and diagnostic response of experiments on Sandia's PBFA II accelerator. This work supported by the U. S. Department of Energy Contract No. DE-AC04-76DP00789. [ABSTRACT FROM AUTHOR]