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An original system has been developed capable of performing three-dimensional Energy Recoil Detection Analysis (ERDA) of hydrogen in materials with scanned and finely focused heavy-ion beams. The technique is being used at the Lawrence Livermore National Laborotory Multi-user Tandem Laboratory to measure the hydrogen content in materials under consideration for use in the Yucca Mountain nuclear waste repository. From the measurement of hydrogen concentration profiles we can extrapolate reaction rates. A critical problem is the rate of dissolution of the glass being used. The HI-ERDA (Heavy Ion-ERDA) technique can provide this information which is needed in order to predict the overall rate of nuclear waste glass degradation in a waste repository. The technique is calibrated using a silicon wafer implanted with a known concentration of hydrogen. The sample is illuminated by a 35Cl ion beam that is micro-scanned across the sample. From these measurements we reconstruct three dimensional profiles of hydrogen content which can then be used to obtain spatially-resolved hydrogen depth profiles.

A wide variety of materials have been analyzed using the nuclear microprobe in Livermore, including metals, low density foams, compound semiconductors for room temperature detectors, glasses and particulates. A brief overview of our recent work is given, in addition to a broader discussion of three specific applications. In the first application, Ion Microtomography (IMT) is used to produce three-dimensional mass density maps of low density foams being developed as targets for Z-pinch physics experiments. In the second application, we produce two-dimensional elemental maps of CdZnTe crystals being developed as room temperature radiation detectors. The maps help determine the effect of local variations in stoichiometry on detector performance. Finally, we discuss the measurement of trace elements and radial diffusion profiles in superconducting wire using micro-scale Particle-Induced X-ray Emission (PIXE).

Nuclear microscopy is well suited for analyzing large particle populations as well as individual particles of interest in various types of collection samples. Unlike some commonly used in situ techniques, nuclear microscopy can quantitatively characterize particles embedded within the sample or particles that are too small to be reliably removed from their collection media. Additional advantages include its capability for the detection of minor and trace elements, its capability to simultaneously analyze multiple elements with little or no prior sample preparation, and its potential for automated analyses. Preliminary data are presented of particle size and composition measurements conducted on air filters. The potential of applying nuclear microscopy to the cataloging of micron-scale cometary remnants captured in low density aerogel collectors is also explored. Because of its importance to a variety of collection programs, an innovative high-throughput ion beam imaging and analysis system is being jointly developed by Sandia and Lawrence Livermore national laboratories for rapid quantitative particle characterization.

Lawrence Livermore National Laboratory (LLNL) and Sandia National Laboratories/California have jointly constructed a new nuclear microprobe beamline. This beamline is located on the LLNL 10 MV tandem accelerator and can be used for multidisciplinary research using PIXE, PIGE, energy loss tomography, or IBS techniques. Distinctive features of the beamline include incorporation of magnet power supplies into the accelerator control system, computer-controlled object and image slits, automated target positioning to sub-micron resolution, and video optics for beam positioning and observation. Mitigation of vibrations was accomplished with vibration isolators and a rigid beamline design while integral beamline shielding was used to shield from stray magnetic fields. Available detectors include a wavelength dispersive X-ray spectrometer, a High-Purity Germanium detector (HPGe), a Lithium-Drifted Silicon X-Ray detector (SiLi), and solid state surface barrier detectors. Along with beamline performance, results from recent measurements on determination of trace impurities in an International Thermonuclear Experimental Reactor (ITER) super conducting wire strand, determination of Ca/Sr ratios in seashells, and determination of minor and trace element concentrations in sperm cells are presented.

Nuclear muscopy uses focused MeV ion mubeams to non-destructively characterize materials and components with mun scale spatial resolution. Although a number of accelerator-based mubeam methods are available for materials analysis, this paper centers on the techniques of Ion mutomography (IMT) and Particle-Induced X-ray Emission (PIXE). IMT provides quantitative three-dimensional density information with mun-scale spatial resolution and 1% density variation sensitivity. Recently, IMT has become more versatile because greater emphasis has been placed on understanding the effects of reconstruction artifacts, beam spatial broadening, and limited projection data sets. PIXE provides quantitative elemental information with detection sensitivities to 1 μg/g or below in some instances. By scanning the beam, two-dimensional maps of elemental concentration can also be recorded. However, since X-rays are produced along the entire path of the ion beam as it penetrates the sample, these measurements only give depth-averaged information in general. PIXE tomography (PIXET) is the natural extension from conventional PIXE analysis to the full three-dimensional measurement and forms the bridge linking the complementary techniques of PIXE and IMT. This paper presents recent developments and applications of these ion beam techniques in a diverse range of fields including characterizing metal-matrix composites, biological specimens and inertial confinement fusion targets.

We have recently completed the construction of a new ion beamline primarily for particle-induced X-ray emission (PIXE) analysis. This will supplement our current ion microtomography (IMT) material characterization capabilities using accelerator microanalysis. In this paper we describe the PIXE beamline and give some results that characterize the system. We also report the results of some initial experiments.

We have developed and are in the process of testing an ion time-of-flight (TOF) detector system for use in our ion microtomography measurements. Using TOF, ion energy is determined by measurement of the ion's flight time over a certain path length. For ion microtomography, the principle advantage of TOF analysis is that ion count rates of several hundred thousand counts per second can be achieved as compared to a limit of about ten thousand ions per second when using a solid-state silicon surface barrier detector and associated electronics. This greater than 10-fold increase in count rate correspondingly shortens sample analysis time or increases the amount of data that can be collected on a given sample.

The complementary techniques of ion microtomography (IMT) and particle‐induced x‐ray emission (PIXE) are used to provide submicron‐scale characterization of inertial confinement fusion (ICF) targets for density uniformity, sphericity, and trace‐element spatial distributions. ICF target quality control in the laser fusion program is important to ensure that the energy deposition from the lasers results in uniform compression and minimization of Rayleigh–Taylor instabilities. We obtain 1% total electron density determinations using IMT with spatial resolution approaching 2 μm. Utilizing PIXE, we can map out dopant and impurity distributions with elemental detection sensitivities on the order of a few parts per million. We present examples of ICF target characterization by IMT and PIXE in order to demonstrate their potential impact in assessing target fabrication processes.

The Lawrence Livermore National Laboratory (LLNL) and the University of California (UC) now have in operation a large AMS spectrometer built as part of a new multiuser laboratory centered on an FN tandem. AMS measurements are expected to use half of the beam time of the accelerator. LLNL use of AMS is in research on consequences of energy usage. Examples include global warming, geophysical site characterization, radiation biology and dosimetry, and study of mutagenic and carcinogenic processes. UC research activities are in clinical applications, archaeology and anthropology, oceanography, and geophysical and geochemical research. Access is also possible for researchers outside the UC system. The technological focus of the laboratory is on achieving high rates of sample throughput, unattended operation, and advances in sample preparation methods. Because of the expected growth in the research programs and the other obligations of the present accelerator, we are designing a follow-on dedicated facility for only AMS and microprobe analysis that will contain at least two accelerators with multiple spectrometers.

Accelerators that use the T(d,n)4He reaction to generate 14-MeV neutrons are discussed. Most of the discussion concerns the Rotating Target Neutron Source II (RTNS-II) facility, which was the most ...

We present results of a measurement of the beta-decay half-life of {sup 8}Li using an {sup 8}Li radioactive ion beam implanted in a Si detector. The half-life is found to be 840.3{plus minus}0.9 ms.

Significant developments have occurred in the technology of room-temperature PbI2 nuclear sensors which lead to some improvements in the detection of high energy gamma-rays. Discussion of crystal growth, purification, monitoring purification, and detector processing are reviewed as they relate to device performance.

The Ion Micro-Analysis Group (IMAG) in Livermore conducts quantitative trace elemental analysis with PIXE and depth profiling with IBS using an MeV ion microbeam. The system has the capability to produce two-dimensional trace element and IBS images. PIXE analyses have been conducted on HgI2 and PbI2 crystals and detector materials in order to identify and quantify near surface trace contaminants. IBS measurements have been conducted to investigate elemental depth distributions in various materials. The results of measurements on several different samples are reported and a discussion of factors affecting quantitative in vacuo microanalysis of these materials is presented.

Measurements of the transmitted energy straggling are made using a silicon surface barrier detector for 2 to 7 MeV protons incident on thin foil targets of Al, Ti, Ag and W. The straggling widths are studied as a function of target thickness, proton energy and target species. The combination of several incident energies with many target thicknesses provides data for the investigation of energy straggling in the region where Tschalar's theory is applicable. The theoretical estimates are found to agree with the measured values for higher energy beams, but are about 10% lower than the data for lower incident energies. A simple empirical expression for the straggling is given which agrees with the experimental data for energy losses up to 60%.

Radiation-resistant optical fibers fabricated with purified silica glass were irradiated at room temperature with 14-MeV neutrons from the RTNS-II. The induced loss in light transmission was measured in situ during irradiation. It was found that the fusion neutron response of the optical fibers can be approximately classed in three types as follows: (1) a large induced loss with little recovery; (2) a large induced loss with a quick recovery; and (3) a small induced loss with a saturated tendency. The induced-loss rate has been calculated on the basis of damage components that depend mainly on neutron fluence and show little recovery. Fusion neutron irradiation effects on related optoelectronic devices and their hardness levels are shown. These are the neutron fluences at which important performance parameters of the devices begin to degrade. The data are useful for fiber-optics design for fusion diagnostic systems. >

Gamma rays have been observed from the 48Ca(p, γ) reaction de-exciting analogs of the 4.005 MeV ( f 5 2 ) and 4.024 MeV ( g 9 2 ) states in 49Ca. The resonances were observed at Ep(c.m.) = 5.933 ± 0.005 and 5.992 ± 0.005 MeV, respectively, with total widths 39 ± 5 and 18 ± 5 keV. The corresponding ground-state γ-widths were inferred to be 17 ± 5 and 22−11+22 eV. Decays of the lower resonance to excited states of 49Sc were also observed. A tentative lower limit of 1.7 eV was placed on the width of the transition to the 3 2 − (3.08 MeV ) level. The upper ( 9 2 + ) γ-ray (g.s.) resonance is depleted by a factor of 10–20 by the giant dipole resonance and cannot be used easily to extract structural information. The (tentative) lower limit on the M1 decay of the lower ( 5 2 − ) resonance to the 3 2 − state (Ex = 3.08 MeV) implies a strong 1 f 5 2 neutron admixture in the lower state which is not borne out by theoretical estimates of the effects of the core polarization. The M1 decay of this same resonance to the ground state is calculated to be 9–13 eV, with the Arima-Horie estimate for the effects of core polarization, and 16 eV in a three-particle, two-hole configuration mixing shell-model calculation. Both figures are consistent with the measurement and confirm the existence of strong magnetic moment renormalization effects.

Rotating Target Neutron Source-II (RTNS-II) is a national facility for fusion materials research. It contains two 14 MeV neutron sources. Deuterons are accelerated to ∼ 400 keV and transported to a rotating titanium tritide target. Present source strength is greater than 1 × 10 13 n/s and source diameter is 1 cm fwhm. An air-levitated vacuum seal permits rotation of the target at 5000 rpm with negligible impact on accelerator vacuum system gas load. Targets are cooled by chilled water flowing through internal channels in a copper alloy substrate. Substrates are produced by solid-state diffusion bonding of two sheets, one containing etched cooling channels. An electroforming process is being developed which will reduce substrate cost and improve reliability. Titanium tritide coating thickness is ∼ 10 μm giving an initial tritium inventory for the present 23 cm diameter targets of 3.7 × 10 7 MBq. Operating interval between target changes is typically about 80 h. Thirteen laboratories and universities have participated in the experimental program at RTNS-II. Most measurements have been directed at understanding defect production and low-dose damage microstructure. The principal diagnostic tools have been cryogenic resistivity measurements, mechanical properties assessment and transmission electron microscopy. Some engineering tests have been conducted in support of near-term magnetic confinement experiments and of reactor materials which will see small lifetime doses.

Results are reported for an ongoing effort to optimize D+ beam production by the MATS-III ion source used at RTNS-II. The characteristics of the source have been determined. Particular attention was paid to the extraction geometry and plasma production. The plasma spatial and temporal uniformity has been examined. The seven aperture triode geometry has been varied to optimize neutron production. This includes beamlet steering and electrode gapping as well as aperture shaping.

Proton beams with energies of 5 and 7 MeV are focused to 5 μm and used to produce tomograms of capillary tubes and low-density foams. In this energy range, proton energy loss is primarily due to interactions with electrons. Therefore, by measuring the residual energy of protons transmitted through samples in a manner similar to that used for Scanning Transmission Ion Microscopy (STIM), and reconstructing a cross-sectional image from multiple projections, we can map out spatial variations in electron density due to sample geometry and composition. In our experimental arrangement, the sample is translated and rotated in a stationary proton beam. Transmitted proton energies are measured using a silicon surface barrier detector. Tomographie reconstructions are produced from the calculated line-average densities using a procedure based on a filtered backprojection algorithm developed for X-ray computed tomography (CT) systems. The technique is especially useful in characterizing samples where large variations in Z or low total density limit the applicability of X-ray CT analysis.

New detailed angular distribution measurements are presented for $^{89}\mathrm{Y}(p, {\ensuremath{\gamma}}_{0})^{90}\mathrm{Zr}$ above the giant dipole resonance ($14 \mathrm{MeV}l~{E}_{p}l~27 \mathrm{MeV}$), which show pronounced effects of higher multipoles. Direct-semidirect calculations provide a good description of the data by including $E2$ and $E3$ as well as $E1$ radiation. The sensitivity of the reaction to a $T=1$ giant quadrupole resonance is demonstrated.

The Rotating Target Neutron Source II facility (RTNS-II) operated for over nine years. Its purpose was to provide high intensities of 14 MeV neutrons for materials studies in the fusion energy program. For the period from 1982–1987, the facility was supported by both the USA (Department of Energy) and Japan (Ministry of Education, Culture and Science). RTNS-II contains two accelerator-based neutron sources which use the T(d, n) 4 He reaction. In this paper we will summarize the operational history of RTNS-II. Typical operating parameters are given. In addition, a brief description of the experimental program is presented. The current status and future options for the facility are discussed.

The Rotating Target Neutron Source (RTNS-II) facility produces 14 MeV neutrons for materials damage studies. Initial operation for irradiations, which took place in 1979, began with a neutron source strength of 1013 n/s utilizing one of the accelerator-based neutron sources. Details are given on improvements which have resulted in both increased neutron production and neutron source strength and improved control and monitoring.

The Rotating Target Neutron Source (RTNS-II) facility provides an intense source of 14 MeV neutrons for the fusion energy programs of Japan and the United States. Each of the two identical accelerator-based neutron sources is capable of providing source strengths in excess of 3 × 1013n/s using deuteron beam currents up to 150 mA. At the present time, the facility operates a minimum total of twenty shifts (8 h) per week using both neutron sources. Because of funding cut-backs, future operations will be limited to one neutron source. The possibility exists to increase neutron output by combining the high voltage power supplies, thereby increasing the current capability of the operating neutron source. This would allow approximately a factor of three increase in neutron output. Using existing equipment, an ion source test stand has been constructed to improve ion source output. Conceptual design studies have been made concerning a factor of ten increase in neutron output. Detailed studies of needed target improvements have been made and will be discussed. The present status of the facility, as well as the various upgrade options, will be described in detail.

Results are reported for an ongoing effort to optimize D + beam production by the MATS-III ion source used at RTNS-II. The three seven-aperture electrodes, originally consisting of water-cooled copper, have now been tested using uncooled molybdenum and with water cooling on the second (decel) electrode only. Details of the change, the results of the testing, and the benefits in operation, performance and cost are given.

This guidebook is intended to provide training criteria, procedures and guidelines for operation of the RTNS-II neutron sources and ancilliary equipment. Use of this document requires full knowledge of the RTNS-II Facility Safety Procedure (FSP) and any Operational Safety Procedures (OSP) in effect. The RTNS-II FSP defines the hazards which may be encountered at RTNS-II and defines the procedures which must be followed in performing any task including operations. The purpose of this document is to provide a central source of detailed information concerning systems and equipment used in operating the RTNS-II neutron sources on a day-to-day basis. All members of the Operations Group are expected to be familiar with its contents. It is also intended to be used in training new members of the Operations Group.

Neutrons are produced at the Rotating Target Neutron Source-II (RTNS-II) by deuteron bombardment of a rotating tritium target. Tritium is released from these targets into the accelerator vacuum system. The vacuum system exhaust is first scrubbed and then vented via the facility stack. Tritium emission from the facility in normal operation with vacuum system exhaust flowing through the scrubber is extremely low