Advanced data acquisition system implementation for the ITER Neutron Diagnostic use case using EPICS and FlexRIO technology on a PXIe platform

In the framework of the ITER Control Breakdown Structure (CBS), Plant System Instrumentation & Control (I&C) defines the hardware and software required to control one or more plant systems [1]. For diagnostics, most of the complex Plant System I&C are to be delivered by ITER Domestic Agencies (DAs). As an example for the DAs, ITER Organization (IO) has developed several use cases for diagnostics Plant System I&C that fully comply with guidelines presented in the Plant Control Design Handbook (PCDH) [2]. One such use case is for neutron diagnostics, specifically the Fission Chamber (FC), which is responsible for delivering time-resolved measurements of neutron source strength and fusion power to aid in assessing the functional performance of ITER [3]. ITER will deploy four Fission Chamber units, each consisting of three individual FC detectors. Two of these detectors contain Uranium 235 for Neutron detection, while a third "dummy" detector will provide gamma and noise detection. The neutron flux from each MFC is measured by the three methods: . Counting Mode: measures the number of individual pulses and their location in the record. Pulse parameters (threshold and width) are user configurable. . Campbelling Mode (Mean Square Voltage): measures the RMS deviation in signal amplitude from its average value. .Current Mode: integrates the signal amplitude over the measurement period

Passive neutron area monitor with pairs of TLDs as neutron detector

A passive neutron area monitor has been designed using Monte Carlo methods; the monitor is a polyethylene cylinder with pairs of thermoluminescent dosimeters (TLD600 and TLD700) as thermal neutron detector. The monitor was calibrated with a bare and a thermalzed 241AmBe neutron sources and its performance was evaluated measuring the ambient dose equivalent due to photoneutrons produced by a 15 MV linear accelerator for radiotherapy and the neutrons in the output of a TRIGA Mark III radial beam port.

Determination of the crystal and magnetic structure of the DyCrO4-scheelite polymorph by neutron diffraction

Neutron diffraction data of DyCrO4 oxide, prepared at 4 GPa and 833 K from the ambient pressure zircon-type, reveal that crystallize with the scheelite-type structure, space group I41/a. Accompanying this structural phase transition induced by pressure the magnetic properties change dramatically from ferromagnetism in the case of zircon to antiferromagnetism for the scheelite polymorph with a T N= 19 K. The analysis of the neutron diffraction data obtained at 1.2 K has been used to determine the magnetic structure of this DyCrO4-scheelite oxide which can be described with a k = [0, 0, 0] as propagation vector, where the Dy and Cr moments are lying in the ab-plane of the scheelite structure. The ordered magnetic moments are 10 µB and 1 µB for Dy+3 and Cr+5 respectively

Why neutron guides may end up breaking down? Some results on the macroscopic behaviour of alkali-borosilicate glass support plates under neutron irradiation

In this paper we report on a first part of a study on the mechanisms leading to brittle fracture in neutron guides made of glass as structural element. Such devices are widely used to deliver thermal and cold neu tron beams to experimental lines in most large neutron research facilities. We present results on macroscopic properties of samples of guide glass substrates which are subjected to neutron irradiation at relatively large fluences. The results show a striking dependence of some of the macroscopic properties such as density, shape or surface curvature upon the specific chemical composition of a given glass. The relevance of the present findings for the installation of either replacement guides at the existing facilities or for the deployment of instruments for ongoing projects such as the European Spallation Source is briefly discussed.

High thermal neutron flux effects on structural and macroscopic properties of alkali-borosilicate glasses used as neutron guide substrate

The behaviour of four alkali-borosilicate glasses under homogeneous thermal neutron irradiation has been studied. These materials are used for the manufacturing of neutron guides which are installed in most facilities as devices to transport neutrons from intense sources such as nuclear reactors or spallation sources up to scientific instruments. Several experimental techniques such as Raman, NMR, SANS and STEM have been employed in order to understand the rather different macroscopic behaviour under irradiation of materials that belong to a same glass family. The results have shown that the remarkable glass shrinking observed for neutron doses below 0.5 · 10 18 n/cm 2 critically depends upon the presence of domains where silicate and borate network do not mix.

Design of a new neutron delivery system for high flux source

La construcción en la actualidad de nuevas fuentes para el uso de haces de neutrones así como los programas de renovación en curso en algunas de las instalaciones experimentales existentes han evidenciado la necesidad urgente de desarrollar la tecnología empleada para la construcción de guías de neutrones con objeto de hacerlas mas eficientes y duraderas. Esto viene motivado por el hecho de que varias instalaciones de experimentación con haces de neutrones han reportado un número de incidentes mecánicos con tales guías, lo que hace urgente el progresar en nuestro conocimiento de los susbtratos vítreos sobre los cuales se depositan los espejos que permiten la reflexión total de los neutrones y como aquellos se degradan con la radiación. La presente tesis se inscribe en un acuerdo de colaboración establecido entre el Institut Max von Laue - Paul Langevin (ILL) de Grenoble y el Consorcio ESS-Bilbao con objeto de mejorar el rendimiento y sostenibilidad de los sistemas futuros de guiado de neutrones. El caso de la Fuente Europea de Espalación en construcción en Lund sirve como ejemplo ya que se contempla la instalación de guías de neutrones de más de 100 metros en algunos de los instrumentos. Por otro lado, instalaciones como el ILL prevén también dentro del programa Endurance de rejuvenecimiento la reconstrucción de varias líneas de transporte de haz. Para el presente estudio se seleccionaron cuatro tipos de vidrios borosilicatados que fueron el Borofloat, N-ZK7, N-BK7 y SBSL7. Los tres primeros son bien conocidos por los especialistas en instrumentación neutrónica ya que se han empleado en la construcción de varias instalaciones mientras que el último es un candidato potencial en la fabricación de substratos para espejos neutrónicos en un futuro. Los cuatro vidrios tiene un contenido en óxido de Boro muy similar, approximadamente un 10 mol.%. Tal hecho que obedece a las regulaciones para la fabricación de estos dispositivos hace que tales substratos operen como protección radiológica absorbiendo los neutrones transmitidos a través del espejo de neutrones. Como contrapartida a tal beneficio, la reacción de captura 10B(n,_)7Li puede degradar el substrato vítreo debido a los 2.5 MeV de energía cinética depositados por la partícula _ y los núcleos en retroceso y de hecho la fragilidad de tales vidrios bajo radiación ha sido atribuida desde hace ya tiempo a los efectos de esta reacción. La metodología empleada en esta tesis se ha centrado en el estudio de la estructura de estos vidrios borosilicatados y como esta se comporta bajo condiciones de radiación. Los materiales en cuestión presentan estructuras que dependen de su composición química y en particular del ratio entre formadores y modificadores de la red iono-covalente. Para ello se han empleado un conjunto de técnicas de caracterización tanto macro- como microscópicas tales como estudios de dureza, TEM, Raman, SANS etc. que se han empleado también para determinar el comportamiento de estos materiales bajo radiación. En particular, algunas propiedades macroscópicas relacionadas con la resistencia de estos vidrios como elementos estructurales de las guías de neutrones han sido estudiadas así como también los cambios en la estructura vítrea consecuencia de la radiación. Para este propósito se ha diseñado y fabricado por el ILL un aparato para irradiación de muestras con neutrones térmicos en el reactor del ILL que permite controlar la temperatura alcanzada por la muestra a menos de 100 °C. Tal equipo en comparación con otros ya existences permite en cuestión de dias acumular las dosis recibidas por una guía en operación a lo largo de varios años. El uso conjunto de varias técnicas de caracterización ha llevado a revelar que los vidrios aqui estudiados son significativamente diferentes en cuanto a su estructura y que tales diferencias afectan a sus propiedades macroscópicas asi como a su comportamiento bajo radiación. Tal resultado ha sido sorprendente ya que, como se ha mencionado antes, algunos de estos vidrios eran bien conocidos por los fabricantes de guías de neutrones y hasta el momento eran considerados prácticamente similares debido a su contenido comparable en óxido de Boro. Sin embargo, los materiales N-BK7 and S-BSL7 muetran gran homogeneidad a todas las escalas de longitud, y más específicamente, a escalas nanométricas las subredes de Sílice y óxido de Boro se mezclan dando logar a estructuras locales que recuerdan a la del cristal de Reedmergnerita. Por el contrario, N-ZK7 y Borofloat muestran dominios separados ricos en Sílice o Boro. Como era de esperar, las importantes diferencias arriba mencionadas se traducen en comportamientos dispares de estos materiales bajo un haz de neutrones térmicos. Los resultados muestran que el N-BK7 y el S-BSL7 son los más estables bajo radiación, lo que macroscópicamente hace que estos materiales muestren un comportamiento similar expandiéndose lentamente en función de la dosis recibida. Por el contario, los otros dos materiales muestran un comportamiento mucho más reactivo, que hace que inicialmente se compacten con la dosis recibida lo que hace que las redes de Silicio y Boro se mezclen resultando en un incremento en densidad hasta alcanzar un valor límite, seguido por un proceso de expansión lenta que resulta comparable al observado para N-BK7 y SBSL7. Estos resultados nos han permitido explicar el origen de las notorias diferencias observadas en cuanto a las dosis límite a partir de las cuales estos materiales desarrollan procesos de fragmentación en superficie. ABSTRACT The building of new experimental neutron beam facilities as well as the renewal programmes under development at some of the already existing installations have pinpointed the urgent need to develop the neutron guide technology in order to make such neutron transport devices more efficient and durable. In fact, a number of mechanical failures of neutron guides have been reported by several research centres. It is therefore important to understand the behaviour of the glass substrates on top of which the neutron optics mirrors are deposited and how these materials degrade under radiation conditions. The case of the European Spallation Source (ESS) at present under construction at Lund is a good example. It previews the deployment of neutron guides having more than 100 metres of length for most of the instruments. Also, the future renovation programme of the ILL, called Endurance, foresees the refurbishment of several beam lines. This Ph.D. thesis was the result of a collaboration agreement between the ILL and ESS-Bilbao aiming to improve the performance and sustainability of future neutron delivery systems. Four different industrially produced alkali-borosilicate glasses were selected for this study: Borofloat, N-ZK7, N-BK7 and SBSL7. The first three are well known within the neutron instrumentation community as they have already been used in several installations whereas the last one is at present considered as a candidate for making future mirror substrates. All four glasses have a comparable content of boron oxide of about 10 mol.%. The presence of such a strong neutron absorption element is in fact a mandatory component for the manufacturing of neutron guides because it provides a radiological shielding for the environment. This benefit is however somewhat counterbalanced since the resulting 10B(n,_)7Li reactions degrade the glass due to the deposited energy of 2.5 MeV by the _ particle and the recoil nuclei. In fact, the brittleness of some of these materials has been ascribed to this reaction. The methodology employed by this study consisted in understanding the general structure of borosilicates and how they behave under irradiation. Such materials have a microscopic structure strongly dependent upon their chemical content and particularly on the ratios between network formers and modifiers. The materials have been characterized by a suite of macroscopic and structural techniques such as hardness, TEM, Raman, SANS, etc. and their behaviour under irradiation was analysed. Some macroscopic properties related to their resistance when used as guide structural elements were monitored. Also, changes in the vitreous structure due to radiation were observed by means of several experimental tools. For such a purpose, an irradiation apparatus has been designed and manufactured to enable irradiation with thermal neutrons within the ILL reactor while keeping the samples below 100 °C. The main advantage of this equipment if compared to others previously available was that it allowed to reach in just some days an equivalent neutron dose to that accumulated by guides after several years of use. The concurrent use of complementary characterization techniques lead to the discovery that the studied glasses were deeply different in terms of their glass network. This had a strong impact on their macroscopic properties and their behaviour under irradiation. This result was a surprise since, as stated above, some of these materials were well known by the neutron guide manufacturers, and were considered to be almost equivalent because of their similar boron oxide content. The N-BK7 and S-BSL7 materials appear to be fairly homogeneous glasses at different length scales. More specifically, at nanometre scales, silicon and boron oxide units seem to mix and generate larger structures somewhat resembling crystalline Reedmergnerite. In contrast, N-ZK7 and Borofloat are characterized by either silicon or boron rich domains. As one could expect, these drastic differences lead to their behaviour under thermal neutron flux. The results show that N-BK7 and S-BSL7 are structurally the most stable under radiation. Macroscopically, such stability results in the fact that these two materials show very slow swelling as a function or radiation dose. In contrast, the two other glasses are much more reactive. The whole glass structure compacts upon radiation. Specifically, the silica network, and the boron units tend to blend leading to an increase in density up to some saturation, followed by a very slow expansion which comes to be of the same order than that shown by N-BK7 and S-BSL7. Such findings allowed us to explain the drastic differences in the radiation limits for macroscopic surface splintering for these materials when they are used in neutron guides.

Neutron field characteristics of Ciemat's Neutron Standards Laboratory Hector Rene Vega-Carrillo

Monte Carlo calculations were carried out to characterize the neutron field produced by the calibration neutron sources of the Neutron Standards Laboratory at the Research Center for Energy, Environment and Technology (CIEMAT) in Spain. For 241AmBe and 252Cf neutron sources, the neutron spectra, the ambient dose equivalent rates and the total neutron fluence rates were estimated. In the calibration hall, there are several items that modify the neutron field. To evaluate their effects different cases were used, from point-like source in vacuum up to the full model. Additionally, using the full model, the neutron spectra were estimated to different distances along the bench; with these spectra, the total neutron fluence and the ambient dose equivalent rates were calculated. The hall walls induce the largest changes in the neutron spectra and the respective integral quantities. The free-field neutron spectrum is modified due the room return effect.

Homogeneous immunoconjugates for boron neutron-capture therapy: Design, synthesis, and preliminary characterization

The application of immunoprotein-based targeting strategies to the boron neutron-capture therapy of cancer poses an exceptional challenge, because viable boron neutron-capture therapy by this method will require the efficient delivery of 103 boron-10 atoms by each antigen-binding protein. Our recent investigations in this area have been focused on the development of efficient methods for the assembly of homogeneous immunoprotein conjugates containing the requisite boron load. In this regard, engineered immunoproteins fitted with unique, exposed cysteine residues provide attractive vehicles for site-specific modification. Additionally, homogeneous oligomeric boron-rich phosphodiesters (oligophosphates) have been identified as promising conjugation reagents. The coupling of two such boron-rich oligophosphates to sulfhydryls introduced to the CH2 domain of a chimeric IgG3 has been demonstrated. The resulting boron-rich immunoconjugates are formed efficiently, are readily purified, and have promising in vitro and in vivo characteristics. Encouragingly, these studies showed subtle differences in the properties of the conjugates derived from the two oligophosphate molecules studied, providing a basis for the application of rational design to future work. Such subtle details would not have been as readily discernible in heterogeneous conjugates, thus validating the rigorous experimental design employed here.

Synthesis and in vivo murine evaluation of Na4[1-(1′-B10H9)-6-SHB10H8] as a potential agent for boron neutron capture therapy

Reaction of the normal isomer of [B20H18]2− and the protected thiol anion, [SC(O)OC(CH3)3]−, produces an unexpected isomer of [B20H17SC(O)OC(CH3)3]4− directly and in good yield. The isomer produced under mild conditions is characterized by an apical–apical boron atom intercage connection as well as the location of the thiol substituent on an equatorial belt adjacent to the terminal boron apex. Although the formation of this isomer from nucleophilic attack of the normal isomer of [B20H18]2− has not been reported previously, the isomeric assignment has been unambiguously confirmed by one-dimensional and two-dimensional 11B NMR spectroscopy. Deprotection of the thiol substituent under acidic conditions produces a protonated intermediate, [B20H18SH]3−, which can be deprotonated with a suitable base to yield the desired product, [B20H17SH]4−. The sodium salt of the resulting [B20H17SH]4− ion has been encapsulated in small, unilamellar liposomes, which are capable of delivering their contents selectively to tumors in vivo, and investigated as a potential agent for boron neutron capture therapy. The biodistribution of boron was determined after intravenous injection of the liposomal suspension into BALB/c mice bearing EMT6 mammary adenocarcinoma. At low injected doses, the tumor boron concentration increased throughout the time-course experiment, resulting in a maximum observed boron concentration of 46.7 μg of B per g of tumor at 48 h and a tumor to blood boron ratio of 7.7. The boron concentration obtained in the tumor corresponds to 22.2% injected dose (i.d.) per g of tissue, a value analogous to the most promising polyhedral borane anions investigated for liposomal delivery and subsequent application in boron neutron capture therapy.

Internal molecular motions of bacteriorhodopsin: hydration-induced flexibility studied by quasielastic incoherent neutron scattering using oriented purple membranes.

Quasielastic incoherent neutron scattering from hydrogen atoms, which are distributed nearly homogeneously in biological molecules, allows the investigation of diffusive motions occurring on the pico- to nanosecond time scale. A quasielastic incoherent neutron scattering study was performed on the integral membrane protein bacteriorhodopsin (BR), which is a light-driven proton pump in Halobacterium salinarium. BR is embedded in lipids, forming patches in the cell membrane of the organism, which are the so called purple membranes (PMs). Measurements were carried out at room temperature on oriented PM-stacks hydrated at two different levels (low hydration, h = 0.03 g of D2O per g of PM; high hydration, h = 0.28 g of D2O per g of PM) using time-of-flight spectrometers. From the measured spectra, different diffusive components were identified and analyzed with respect to the influence of hydration. This study supports the idea that a decrease in hydration results in an appreciable decrease in internal molecular flexibility of the protein structure. Because it is known from studies on the function of BR that the pump activity is reduced if the hydration level of the protein is insufficient, we conclude that the observed diffusive motions are essential for the function of this protein. A detailed analysis and classification of the different kinds of diffusive motions, predominantly occurring in PMs under physiological conditions, is presented.

Preparation and properties of nido-carborane-specific monoclonal antibodies for potential use in boron neutron capture therapy for cancer.

As the first step of a research program aimed at developing a bispecific monoclonal antibody system for the delivery of boron-rich molecules to tumor cells for boron neutron capture therapy, monoclonal antibodies (mAbs) were produced against an anionic nido-carborane derivative, 4-[7,8-dicarbadodecahydroundecaborat(-1)-7-yl]butanoic acid. Two IgG subclass mAbs, designated HAW101 and HAW102, were identified that specifically bound the anionic nido-carborane hapten, as well as a variety of other anionic nido-carborane cage derivatives. By using surface plasmon resonance technology, the affinity constants of HAW101 and HAW102 were determined to be 1.9 x 10(9) and 6.8 x 10(8) M-1, respectively. A diverse array of 7-substituted and 7,8-disubstituted anionic nido-carborane derivatives reacted with the mAb HAW101 in competition ELISA, whereas anionic closo-polyhedral boranes showed negligible binding, suggesting a role for the open nido-carborane cage structure. These results suggest that mAbs such as HAW101, which bind anionic nido-carboranes, are useful in the development of bispecific mAbs for specific targeting and enhanced boron delivery to tumor sites.

Force-free twisted magnetospheres of neutron stars

Context. The X-ray spectra observed in the persistent emission of magnetars are evidence for the existence of a magnetosphere. The high-energy part of the spectra is explained by resonant cyclotron upscattering of soft thermal photons in a twisted magnetosphere, which has motivated an increasing number of efforts to improve and generalize existing magnetosphere models. Aims. We want to build more general configurations of twisted, force-free magnetospheres as a first step to understanding the role played by the magnetic field geometry in the observed spectra. Methods. First we reviewed and extended previous analytical works to assess the viability and limitations of semi-analytical approaches. Second, we built a numerical code able to relax an initial configuration of a nonrotating magnetosphere to a force-free geometry, provided any arbitrary form of the magnetic field at the star surface. The numerical code is based on a finite-difference time-domain, divergence-free, and conservative scheme, based of the magneto-frictional method used in other scenarios. Results. We obtain new numerical configurations of twisted magnetospheres, with distributions of twist and currents that differ from previous analytical solutions. The range of global twist of the new family of solutions is similar to the existing semi-analytical models (up to some radians), but the achieved geometry may be quite different. Conclusions. The geometry of twisted, force-free magnetospheres shows a wider variety of possibilities than previously considered. This has implications for the observed spectra and opens the possibility of implementing alternative models in simulations of radiative transfer aiming at providing spectra to be compared with observations.

A new code for the Hall-driven magnetic evolution of neutron stars

Over the past decade, the numerical modeling of the magnetic field evolution in astrophysical scenarios has become an increasingly important field. In the crystallized crust of neutron stars the evolution of the magnetic field is governed by the Hall induction equation. In this equation the relative contribution of the two terms (Hall term and Ohmic dissipation) varies depending on the local conditions of temperature and magnetic field strength. This results in the transition from the purely parabolic character of the equations to the hyperbolic regime as the magnetic Reynolds number increases, which presents severe numerical problems. Up to now, most attempts to study this problem were based on spectral methods, but they failed in representing the transition to large magnetic Reynolds numbers. We present a new code based on upwind finite differences techniques that can handle situations with arbitrary low magnetic diffusivity and it is suitable for studying the formation of sharp current sheets during the evolution. The code is thoroughly tested in different limits and used to illustrate the evolution of the crustal magnetic field in a neutron star in some representative cases. Our code, coupled to cooling codes, can be used to perform long-term simulations of the magneto-thermal evolution of neutron stars.

Unifying the observational diversity of isolated neutron stars via magneto-thermal evolution models

Observations of magnetars and some of the high magnetic field pulsars have shown that their thermal luminosity is systematically higher than that of classical radio-pulsars, thus confirming the idea that magnetic fields are involved in their X-ray emission. Here we present the results of 2D simulations of the fully coupled evolution of temperature and magnetic field in neutron stars, including the state-of-the-art kinetic coefficients and, for the first time, the important effect of the Hall term. After gathering and thoroughly re-analysing in a consistent way all the best available data on isolated, thermally emitting neutron stars, we compare our theoretical models to a data sample of 40 sources. We find that our evolutionary models can explain the phenomenological diversity of magnetars, high-B radio-pulsars, and isolated nearby neutron stars by only varying their initial magnetic field, mass and envelope composition. Nearly all sources appear to follow the expectations of the standard theoretical models. Finally, we discuss the expected outburst rates and the evolutionary links between different classes. Our results constitute a major step towards the grand unification of the isolated neutron star zoo.

The imprint of the crustal magnetic field on the thermal spectra and pulse profiles of isolated neutron stars

Isolated neutron stars (NSs) show a bewildering variety of astrophysical manifestations, presumably shaped by the magnetic field strength and topology at birth. Here, using state-of-the-art calculations of the coupled magnetic and thermal evolution of NSs, we compute the thermal spectra and pulse profiles expected for a variety of initial magnetic field configurations. In particular, we contrast models with purely poloidal magnetic fields to models dominated by a strong internal toroidal component. We find that, while the former displays double-peaked profiles and very low pulsed fractions, in the latter, the anisotropy in the surface temperature produced by the toroidal field often results in a single pulse profile, with pulsed fractions that can exceed the 50–60 per cent level even for perfectly isotropic local emission. We further use our theoretical results to generate simulated ‘observed’ spectra, and show that blackbody (BB) fits result in inferred radii that can be significantly smaller than the actual NS radius, even as low as ∼1–2 km for old NSs with strong internal toroidal fields and a high absorption column density along their line of sight. We compute the size of the inferred BB radius for a few representative magnetic field configurations, NS ages and magnitudes of the column density. Our theoretical results are of direct relevance to the interpretation of X-ray observations of isolated NSs, as well as to the constraints on the equation of state of dense matter through radius measurements.