Narrow Results

A workshop on practical problems in biological applications of micro-PIXE analysis was held in one of the evening sessions at the 8th International Conference on Nuclear Microprobe Technology and Application which was held in Takasaki, Japan, throughout September 8-13, 2002. We summarize the participants' exchange of observations and suggestions on technical aspects of biological sample target preparation and specimen damage due to beam irradiation, which occur in micro-PIXE analysis under vacuum.

Analysis of cultural heritage samples by PIXE involves the risk of damaging precious samples due to MeV-proton irradiation. To investigate appropriate methods to detect invisible damage due to PIXE analysis, we analyzed the change in chemical bonding of the sample surface subjected to PIXE and RBS measurement by Fourier Transform InfraRed spectroscopy (FT-IR). We used Japanese hemp paper as a simulated cultural property sample. The proton irradiation for the PIXE/RBS measurement was performed in a vacuum with an incident beam energy of 2.5 MeV, a beam current of 1 nA, and an irradiation time up to 10 min. The corresponding beam flux and fluence were 0.06 nA/mm² and 4 $\mu$Coulomb/cm², respectively. When the irradiation time was 10 min, the absorbed dose was 480 kGy on the sample surface. We identified neither change of elemental composition nor visible change such as discoloration due to irradiation. However, we found changes in peak heights in the measured FT-IR spectra, which suggest the destruction of chemical bonds such as O–H and C–O due to proton-induced radiation damage.

Scanning nuclear microprobes using Rutherford backscattering (RBS) and particle-induced X-ray emission (PIXE) with light ions have been formed using variable objective slits and a magnetic quadrupole doublet. Beam optics, focusing techniques, factors limiting the minimum beam-spot size, and data acquisition systems are discussed. Two- and three-dimensional RBS mapping and channeling contrast mapping of processed semiconductor layers such as multilayered wiring and focused ion-implanted layers are demonstrated. Problems with microbeam analysis such as radiation damages due to the probe beams are discussed.

The effect of radiation damage on copper clusters has been investigated by performing molecular-dynamics simulation using empirical potential energy function for interaction between copper atoms. The external radiation is modeled by giving extra kinetic energy in the range of 5–50 eV to initially chosen atom in the cluster. It has been found that the atom having extra kinetic energy dissociates independently from the amount of given energy in the studied range.

The Mu2e experiment being designed at Fermilab will be searching for a rare event — conversion of muon into electron in the field of a nucleus without emission of neutrinos — observation of which would provide unambiguous evidence for physics beyond the Standard Model, making use of an 8 GeV 8 kW proton beam. As an experiment to be performed at the Intensity Frontier, taking advantage of high-intensity proton beams, the Mu2e experimental setup will be residing in a harsh radiation environment created by secondary particle fluxes.

Radiation quantities in different parts of the Mu2e apparatus, such as neutron flux, peak power density, displacements per atom (DPA), absorbed dose, dynamic heat load simulated using the MARS15 code are reviewed in this work. Radiation levels and requirements for Heat and Radiation Shield (HRS), Transport Solenoid (TS), residual dose and decay heat from the Mu2e target, beam dump design, rates in Cosmic Ray Veto (CRV) counters as well as stopping target monitor (STM) are considered. Airflow, surface and ground water activation are estimated. Recent developments in the MARS15 DPA model applied in this work are described, their consequences are discussed.

The heavy ion irradiation simulation of neutron and/or proton irradiation has been verified experimentally by the detailed study of radiation damage in α-Al₂O₃ irradiated at the equivalent dose by 5.28×10¹⁵cm^-285 MeV¹⁹F ions and by 3×10²⁰cm^-2 E_n≥1MeV neutrons, respectively. The radiation damage created by irradiation was examined by a positron annihilation lifetime technique. The positron annihilation parameters of lifetime and intensity obtained for both irradiations in α-Al₂O₃ are all in good agreement. This demonstrates that the heavy ion irradiation can well simulate the neutron and/or proton irradiation.

This paper presents a new stochastic model to describe the progression of cells subject to radiation damage, through their cell cycles. The expected number of cells in various phases in the transient and steady state are obtained. Several interesting cases like quiescence in tumor cell population, effects of split dose and holding time on cell survival are also discussed using the developed model. The phase structured model offers quiescence and variable cell cycle time as contributing factors for the retardation of cell growth and the ultimate cell population reaching a steady state.

In this paper, we introduce a model to analyze the manufacturing of an implanted-junction rectifier. The model gives a possibility to analyze dependence of charge carriers mobility on the value of dose of implanted ions. Also, we introduce an analytical approach to analyze mass transfer. The approach gives a possibility to make the analysis in a more common situation, as was recently done in the literature. Analysis of the introduced model shows an increae in the spread of distribution of dopant and decrease of mismatch-induced stresses in multilayer structures with increase of dose of implanted ions.

The effect of radiative impacts on the structure of boron carbide has been studied by both classical and ab initio simulations. As a part of this study, a new forcefield was developed for use in studying boron carbide materials. Impact scenarios in boron carbide were simulated in order to investigate the exceptional resistance of this material, and other icosahedral boron solids, to high-energy impact events. It was observed that interstitial defects created by radiative impacts are likely to be quenched locally, utilizing the high substitutional disorder of chains and cages in the boron carbide structure, rather than via impacted atoms recombining with their vacated lattice site.

Radiation damage in structural materials is of major concern and a limiting factor for a wide range of engineering and scientific applications, including nuclear power production, medical applications, or components for scientific radiation sources. The usefulness of these applications is largely limited by the damage a material can sustain in the extreme environments of radiation, temperature, stress, and fatigue, over long periods of time. Although a wide range of materials has been extensively studied in nuclear reactors and neutron spallation sources since the beginning of the nuclear age, ion beam irradiations using particle accelerators are a more cost-effective alternative to study radiation damage in materials in a rather short period of time, allowing researchers to gain fundamental insights into the damage processes and to estimate the property changes due to irradiation. However, the comparison of results gained from ion beam irradiation, large-scale neutron irradiation, and a variety of experimental setups is not straightforward, and several effects have to be taken into account. It is the intention of this article to introduce the reader to the basic phenomena taking place and to point out the differences between classic reactor irradiations and ion irradiations. It will also provide an assessment of how accelerator-based ion beam irradiation is used today to gain insight into the damage in structural materials for large-scale engineering applications.

Charge strippers play a critical role in many high intensity heavy ion accelerators. Here we present some history of recent stripper technology development and indicate the capabilities and limitations of the various approaches. The properties of solid, gaseous, and liquid strippers are covered. In particular, the limitations of solid strippers for high intensity, high atomic number heavy ions and the unique features of helium gas and liquid lithium for high intensity applications are covered. The need for high quality simulation of stripper performance as important input for system optimization is explained and examples of the current simulation codes are given.

This section updates Volume 4 of the Reviews of Accelerator Science and Technology titled “Accelerator Applications in Industry and the Environment,” published in 2011 [A. W. Chao and W. Chou (eds.), Reviews of Accelerator Science and Technology, Accelerator Applications in Industry and the Environment, Vol. 4 (World Scientific, 2011)]. We also include the new material available about this field following the publication of “The Beam Business: Accelerators in Industry” in 2011 [R. W. Hamm and M. E. Hamm, Physics Today 46–51 (June 2011)] and “Industrial Accelerators and Their Applications” in 2012 [R. W. Hamm and M. E. Hamm, Industrial Accelerators and Their Applications (World Scientific, 2012)], both written and co-edited by one of us (RWH). We start with some general trends in industrial accelerator developments and applications and then move on to bringing the up-to-date developments in each article of Volume 4. In this regard, we owe a debt of gratitude to many of the authors of sections of RAST-$4$, and they are gratefully acknowledged in each of their individual update submissions.

A fast neutron (E> MeV) irradiation facility is under development at the 70 MeV SPES proton cyclotron at LNL (Legnaro, Italy) to investigate neutron-induced Single Event Effects (SEE) in microelectronic devices and systems. After an overview on neutron-induced SEE in electronics, we report on the progress in the design of ANEM (Atmospheric Neutron EMulator), a water-cooled rotating target made of Be and W to produce neutrons with an energy spectrum similar to that of neutrons produced by cosmic rays at sea-level. In ANEM, the protons from the cyclotron alternatively impinge on two circular sectors of Be and W of different areas; the effective neutron spectrum is a weighted combination of the spectra from the two sectors. In this contribution, we present the results of thermal-mechanical Finite Element Analysis (ANSYS) calculations of the performance of the ANEM prototype. The calculations at this stage indicate that ANEM can deliver fast neutrons with an atmospheric-like energy spectrum and with an integral flux ${\mathrm{\Phi }}_n$(1-70 MeV) $\sim$10⁷ n cm${}^{-2}$s${}^{-1}$ that is 3×10⁹ more intense than the natural one at sea-level: a very competitive flux for SEE testing.

High detection efficiency and good room temperature performance of Schottky barrier CdTe semiconductor detectors make them well suited especially for X-ray and gamma-ray detectors. In this contribution, we studied the effect of electron irradiation on the spectrometric performance of the Schottky barrier CdTe detectors manufactured from the chips of size $4\times 4\times 1$ mm³ with In/Ti anode and Pt cathode electrodes (Acrorad Co., Ltd.). Electron irradiation of the detectors was performed by 5 MeV electrons at RT using a linear accelerator UELR 5-1S. Different accumulated doses from 0.5 kGy up to 1.25 kGy were applied and the consequent degradation of the spectrometric properties was evaluated by measuring the pulse-height gamma-spectra of ${}^{241}\mathrm{Am}$ radioisotope source. The spectra were collected at different reverse voltages from 300 V up to 500 V. The changes of selected significant parameters, like energy resolution, peak position, detection efficiency and leakage current were monitored and evaluated to quantify the radiation hardness of the studied detectors. The results showed remarkable worsening of their spectrometric parameters even at relatively low applied doses of 1.25 kGy.

This section updates Volume 4 of the Reviews of Accelerator Science and Technology titled “Accelerator Applications in Industry and the Environment,” published in 2011 [A. W. Chao and W. Chou (eds.), Reviews of Accelerator Science and Technology, Accelerator Applications in Industry and the Environment, Vol. 4 (World Scientific, 2011)]. We also include the new material available about this field following the publication of “The Beam Business: Accelerators in Industry” in 2011 [R. W. Hamm and M. E. Hamm, Physics Today 46–51 (June 2011)] and “Industrial Accelerators and Their Applications” in 2012 [R. W. Hamm and M. E. Hamm, Industrial Accelerators and Their Applications (World Scientific, 2012)], both written and co-edited by one of us (RWH). We start with some general trends in industrial accelerator developments and applications and then move on to bringing the up-to-date developments in each article of Volume 4. In this regard, we owe a debt of gratitude to many of the authors of sections of RAST-4, and they are gratefully acknowledged in each of their individual update submissions.

The dependence of radiation damage in the modified 316L stainless steel on irradiation temperature from room temperature to 802 °C and on irradiation dose up to 100 dpa has been investigated by the heavy ion irradiation simulation and positron annihilation lifetime techniques. The largest vacancy cluster is detected at 580 °C that contains 14 vacancies and has an average diameter of 0.7 nm. The size of the vacancy clusters increases with the increasing of irradiation dose, and the vacancy cluster contains 8 vacancies and reaches 0.55 nm in diameter for a 100 dpa irradiation at room temperature. There is a tendency that the saturation of the vacancy cluster size starts at 75 dpa. The experimental results also reveal that the radiation damage is more sensitive to irradiation temperature than irradiation dose.

The CDF Run II silicon detector is the largest operating silicon detector in High Energy Physics. Its 750,000 channels spread over 6 m² of silicon microstrip sensors allow precision tracking and vertexing. The CDF silicon detector played a critical role in the discovery of B_s mixing and is used extensively for the current Higgs Boson searches. The observed effects of aging are presented followed by the expected performance to the end of the Tevatron Run II program, where 5.8-8.5 fb^-1 is expected to be delivered. The impact of radiation damage upon the performance of the detector is shown including the status and expectations of the two inner most layers which have already inverted. The infrastructure (cooling, power supplies) aging problems dealt with during the 2007 sumer shutdown are also discussed.

Charge Coupled Devices (CCDs) have been successfully used in several high energy physics experiments over the past two decades. Their high spatial resolution and thin sensitive layers make them an excellent tool for studying short-lived particles. The Linear Collider Flavour Identification (LCFI) collaboration is developing Column-Parallel CCDs (CPCCDs) for the vertex detector of the International Linear Collider (ILC). The CPCCDs can be read out many times faster than standard CCDs, significantly increasing their operating speed. The results of detailed simulations of the charge transfer inefficiency (CTI) of a prototype CPCCD are reported and studies of the influence of gate voltage on the CTI described. The effects of bulk radiation damage on the CTI of a CPCCD are studied by simulating the effects of two electron trap levels, 0.17 and 0.44 eV, at different concentrations and operating temperatures. The dependence of the CTI on different occupancy levels (percentage of hit pixels) and readout frequencies is also studied. The optimal operating temperature for the CPCCD, where the effects of the charge trapping are at a minimum, is found to be about 230 K for the range of readout speeds proposed for the ILC. The results of the full simulation have been compared with a simple analytic model.

The evaluation of radiation damage in nuclear reactors is an issue with increasing importance.

In new reactors (GEN-IV and fusion reactors) novel materials will be used, for which extensive experimental information is still lacking. This obviously leads to the need to accurately simulate the expected radiation damage. For the ageing existing nuclear reactor population accurate estimates of radiation damage are required for surveillance and plant-life management purposes.

Radiation damage was formerly usually estimated by the calculation of the DPA using deterministic neutronics analyses. Currently, reactor physics simulations are more and more performed with 3-dimensional Monte Carlo codes, like MCNP.

In this paper a novel method is presented, which uses the strength of the Monte Carlo method. Using the detailed information which is available in the neutronics simulation an accurate calculation of the DPA may be carried out in conjunction with the neutron transport calculation. No additional data libraries are needed, guaranteeing the consistency between neutron transport data and DPA calculation. Moreover, the method may be used for all types of reactors, both thermal and fast.

The underlying DPA-data are shown to be in good agreement with the deterministic data. The method is applied to a gas-cooled reactor design.

Charge Coupled Devices (CCDs) have been successfully used in several high energy physics experiments over the past two decades. Their high spatial resolution and thin sensitive layers make them an excellent tool for studying short-lived particles. The Linear Collider Flavour Identification (LCFI) Collaboration has been developing Column-Parallel CCDs for the vertex detector of a future Linear Collider which can be read out many times faster than standard CCDs. The most recent studies are of devices designed to reduce both the CCD's intergate capacitance and the clock voltages necessary to drive it. A comparative study of measured Charge Transfer Inefficiency values between our previous and new results for a range of operating temperatures is presented.