Uncertainty Modeling and Analysis of the European X-ray Free Electron Laser Cavities Manufacturing Process

This paper reports on comprehensive efforts on uncertainty quantification and global sensitivity analysis for accelerator cavity design. As a case study object the TESLA shaped superconducting cavities, as produced for the European X-ray Free Electron Laser (EXFEL), are selected. The choice for these cavities is explained by the available measurement data that can be leveraged to substantiate the simulation model. Each step of the manufacturing chain is documented together with the involved uncertainties. Several of these steps are mimicked on the simulation side, e.g. by introducing a random eigenvalue problem. The uncertainties are then quantified numerically and in particular the sensitivities give valuable insight into the systems behavior. We also compare these findings to purely statistical studies carried out for the manufactured cavities. More advanced, adaptive, surrogate modeling techniques are adopted, which are crucial to incorporate a large number of uncertain parameters. The main contribution is the detailed comparison and fusion of measurement results for the EXFEL cavities on the one hand and simulation based uncertainty studies on the other hand. After introducing the quantities of physical interest for accelerator cavities and the Maxwell eigenvalue problem, the details on the manufacturing of the EXFEL cavities and measurements are reported. This is followed by uncertainty modeling with quantification studies

Normal glucose tolerant women with low glycemia during the oral glucose tolerance test have a higher risk to deliver a low birth weight infant

BackgroundData are limited on pregnancy outcomes of normal glucose tolerant (NGT) women with a low glycemic value measured during the 75g oral glucose tolerance test (OGTT). Our aim was to evaluate maternal characteristics and pregnancy outcomes of NGT women with low glycemia measured at fasting, 1-hour or 2-hour OGTT.MethodsThe Belgian Diabetes in Pregnancy-N study was a multicentric prospective cohort study with 1841 pregnant women receiving an OGTT to screen for gestational diabetes (GDM). We compared the characteristics and pregnancy outcomes in NGT women according to different groups [(<3.9mmol/L), (3.9-4.2mmol/L), (4.25-4.4mmol/L) and (>4.4mmol/L)] of lowest glycemia measured during the OGTT. Pregnancy outcomes were adjusted for confounding factors such as body mass index (BMI) and gestational weight gain.ResultsOf all NGT women, 10.7% (172) had low glycemia (<3.9 mmol/L) during the OGTT. Women in the lowest glycemic group (<3.9mmol/L) during the OGTT had compared to women in highest glycemic group (>4.4mmol/L, 29.9%, n=482), a better metabolic profile with a lower BMI, less insulin resistance and better beta-cell function. However, women in the lowest glycemic group had more often inadequate gestational weight gain [51.1% (67) vs. 29.5% (123); p<0.001]. Compared to the highest glycemia group, women in the lowest group had more often a birth weight <2.5Kg [adjusted OR 3.41, 95% CI (1.17-9.92); p=0.025].ConclusionWomen with a glycemic value <3.9 mmol/L during the OGTT have a higher risk for a neonate with birth weight < 2.5Kg, which remained significant after adjustment for BMI and gestational weight gain

Ruimtevaartdosimetrie: karakterisatie van OSL Al3O3:C detectoren

Abstract Ruimtevaartdosimetrie: Karakterisatie van OSL α-Al2O3:C detectoren Auteur: Toon Roggen Interne promotor: lic. Bob Schaeken Externe promotor: dr. ir. Filip Vanhavere Eén van de grootste uitdagingen van de stralingsdosimetrie is een correcte dosisregistratie voor astronauten gedurende hun ruimtevaartmissie. Dit is niet vanzelfsprekend aangezien het stralingsveld opgebouwd is uit een groot aantal verschillende primaire deeltjes met een breed energiespectrum. Op hun beurt creëren deze primaire deeltjes via interacties met de wand van het ruimteschip, apparatuur… een complex gamma aan secundaire deeltjes met uiteenlopende energieën. Belangrijk in het onderzoek is de gevolgen te achterhalen van de blootstelling van verschillende biologische organismen aan deze dosissen. Uiteindelijke dosisregistratie zal gebeuren a.h.v. meerdere types detectoren. Passieve detectoren en kleine actieve detectoren gevoed door een batterij verdienen hierbij de voorkeur. α-Al2O3:C dosismeters zijn een uitstekend kandidaat o.a. omwille van hun hoge gevoeligheid. Deze gevoeligheid wordt nog verhoogd door gebruik te maken van een dosisuitlezing op basis van optisch gestimuleerde luminescentie (OSL). Aangezien OSL een relatief nieuwe dosimetrietechniek is waarover er nog relatief weinig geweten is, zeker op gebied van ruimtevaartdosimetrie, wordt er in internationaal verband onderzoek gedaan naar de eigenschappen ervan. Voor participatie in deze onderzoeken stelt de afdeling Dosimetrie van het SCK●CEN 2 types dosismeters ter beschikking: TLD500 (zuivere Al2O3:C kristallen) en Luxel™ (mengsel van Al2O3:C kristallen en polyester). Dit eindwerk betreft de karakterisatie van beide types detectoren en omvat een studie van herhaalbaarheid, lineariteit, detectiegevoeligheid, energie-efficiëntie, signaalverzwakking (fading), UV-gevoeligheid, resetmethoden (annealingmethoden), effect van resetten, individuele factorbepaling, detectorrespons op verschillende stralingskwaliteiten (60Co, 137Cs, 252Cf, X-stralen, neutronen…). Tot slot worden ook de resultaten van de uitgevoerde experimenten op het International Space Station (ISS), het CERN (gesimuleerd ruimtespectrum \u27CERF\u27), het JRC IRMM (Van de Graaff versneller)…besproken en geanalyseerd

A higher harmonic cavity at 800 MHz for HL-LHC

A superconducting 800 MHz second harmonic system is proposed for HL-LHC. It serves as a cure for beam instabilities with high beam currents by improving Landau damping and will allow for bunch profile manipulation. This can potentially help to reduce intra-beam-scattering, beam induced heating and e-cloud effects, pile-up density in the detectors and beam losses. An overview of the 800 MHz cavity design and RF power requirements is given. In particular the design parameters of the cavity shape and HOM couplers are described. Some other aspects such as RF power requirements and cryomodule layout are also addressed

Thermal Studies on the SPS Wideband Transverse Feedback Kicker

As part of the SPS wideband transverse feedback system in the framework of the LHC Injector Upgrade (LIU) project, a wideband kicker design is being proposed. Vertical beam instabilities due to intensity dependent effects (electron cloud instability (ECI) and transverse mode coupling instability (TMCI)) are potentially suppressed by using a feedback system driving such a kicker system. One of the options for a kicker is a one meter long slotted-coaxial kicker, providing a substantial vertical kick strength (10ˉ5 –10ˉ4 eV.s/m) over a bandwidth ranging from nearly DC to 1 GHz. The necessary kick strength requires a total power of 4 kW. This note describes thermal studies that assisted in the material choice of the feedthroughs of the slotted-coaxial kicker and guided the design choices

Measurements on the SPS 200 MHz Travelling Wave Cavity towards an Impedance Model

This note discusses the contribution of the SPS 200 MHz TWC (Travelling Wave Cavity) to the SPS longitudinal impedance model. The measurement method and setup is briefly explained and a comparison with simulations is discussed for both the fundamental pass band (FPB) as well as the Higher Order Modes (HOMs). In addition a number of improvements to the measurement setup are discussed

Stochastic Response Surface Method for Studying Microphoning and Lorenz Detuning of Accelerator Cavities

The dependence of the eigenfrequencies of a superconductive cavity on its geometry are represented by a stochastic response surface model. The model is constructed on the basis of both information on the eigenfrequencies as on their sensitivities with respect to the geometry. The eigenmodes are calculated using the 2D or 3D finite element method or finite integration technique. The stochastic representation does not only model uncertainties on the geometrical parameters but also inaccuracies of the eigenmode solvers, e.g. due to remeshing. Variations or optimisations of the geometry are carried out on the surrogate model. The model allows an efficient evaluation of microphoning and Lorentz detuning of accelerator cavities.status: publishe

Study of electron transport in a compact storage ring after interaction with target materials

A compact electron storage ring has been studied with tools for 3D electromagnetic field simulation. To produce an intense hard X-ray beam, the electrons interact with a target inside the system. If the impact on the electron trajectory after interaction is small, it is possible to reuse the electron several times as in a conventional synchrotron storage ring. We tracked the electrons in the 3D electromagnetic fields of the storage ring. From our numerical experiments we can determine the maximum thickness of the target materials.status: publishe

The SPS 200 MHz TWC impedance after the LIU upgrade

As a part of the LHC Injectors Upgrade project (LIU) the 200 MHz Travelling Wave Cavities (TWC) of the Super Proton Synchrotron (SPS) will be upgraded. The two existing five-section cavities will be rearranged into four three-section cavities (using two existing spare sections), thereby increasing the total voltage from 7 MV (I$_{RF}$ = 1.5 A) to 10 MV (I$_{RF}$ = 3.0 A). Projections of the HL-LHC (High Luminosity Large Hadron Collider) era are conceived by the macro-particle simulation code BLonD, that makes use of an impedance model of the SPS, developed from a thorough survey of machine elements. This paper analyses the impedance contribution of the 200 MHz cavities in the two configurations, using electromagnetic simulations. Measurements of the existing cavities in the SPS and a single-section prototype are also presented