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Wendelstein 7-X, a superconducting optimized stellarator built in Greifswald/Germany, started its first plasmas with the last closed flux surface (LCFS) defined by 5 uncooled graphite limiters in December 2015. At the end of the 10 weeks long experimental campaign (OP1.1) more than 20 independent diagnostic systems were in operation, allowing detailed studies of many interesting plasma phenomena. For example, fast neutral gas manometers supported by video cameras (including one fast-frame camera with frame rates of tens of kHz) as well as visible cameras with different interference filters, with field of views covering all ten half-modules of the stellarator, discovered a MARFE-like radiation zone on the inboard side of machine module 4. This structure is presumably triggered by an inadvertent plasma-wall interaction in module 4 resulting in a high impurity influx that terminates some discharges by radiation cooling. The main plasma parameters achieved in OP1.1 exceeded predicted values in discharges of a length reaching 6 s. Although OP1.1 is characterized by short pulses, many of the diagnostics are already designed for quasi-steady state operation of 30 min discharges heated at 10 MW of ECRH. An overview of diagnostic performance for OP1.1 is given, including some highlights from the physics campaigns.

Recent developments in accelerator physics have led to new challenges for radiation protection dosimetry. As is well known, the ambient dose equivalent indicated by area monitors in high-energy neutron fields behind shielding is often unreliable. Therefore, it is desirable to measure the spectrum and to do "in-field" calibrations using the spectral information as reference. For this purpose, the PTB NEMUS (an extended-range Bonner sphere spectrometer) was modified with a new active thermal neutron detector based on silver activation capable of measuring in intense pulsed fields with high energies and fluence rates.

Recent developments in accelerator physics have led to new challenges for radiation protection dosimetry. Doses have to be determined for workplace fields which are characterized by high-energy radiation, a dominant contribution from neutrons, high intensities and pulsed time structure This may present problems for active measuring devices. As is well known, the ambient dose equivalent is often underestimated by area monitors operating in high-energy neutron fields behind shielding. Therefore, it is desirable to calibrate survey monitors in a characterized neutron field with the type of spectral fluence distribution that is expected behind shielding, i.e. where the main dose from neutrons arises from two peaks with mean energies of about 1 MeV and 100 MeV, respectively. Such a neutron fluence distribution is produced by the irradiation of a Fe-target with 200 MeV/u 12C-ions. Measurements with the extended range Bonner sphere spectrometer NEMUS of PTB were performed at two positions inside the experimental area Cave A of the heavy-ion synchrotron SIS at GSI. The measured neutron spectra show different fluence contributions for the two peaks at the two positions. The results were compared to Monte Carlo Simulations with MCNPX and FLUKA.

The European Commission has funded within its 6th Framework Programme a three-year project (2005–2007) called CONRAD, COordinated Network for RAdiation Dosimetry. The organizational framework for this project was provided by the European radiation Dosimetry Group EURADOS. Work Package 6 of CONRAD dealt with “complex mixed radiation fields at workplaces” and in this context it organised a benchmark exercise, which included both measurements and calculations, in a stray radiation field at a high-energy particle accelerator at GSI, Germany. The aim was to intercompare the response of several types of active detectors and passive dosemeters in a well-characterised workplace field. The Monte Carlo simulations of the radiation field and the experimental determination of the neutron spectra with various Bonner Sphere Spectrometers are discussed in Rollet et al. (2008) and in Wiegel et al. (2008). This paper focuses on the intercomparison of the response of the dosemeters in terms of ambient dose equivalent. The paper describes in detail the detectors employed in the experiment, followed by a discussion of the results. A comparison is also made with the H*(10) values predicted by the Monte Carlo simulations and those measured by the BSS systems.

In neutron reference radiation fields, the conventional true value of the personal dose equivalent, H(p)(10), is derived from the spectral neutron fluence and recommended conversion coefficients. This procedure requires the phantom on which the personal dosemeter is mounted to be irradiated with a broad and parallel beam. In many practical situations, the change of the neutron fluence and/or the energy distribution over the surface of the phantom may not be neglected. For a selection of typical irradiation conditions in neutron reference radiation fields, the influence of this effect has been analysed using numerical methods. A further problem, which is of relevance for the calibration of dosemeters measuring both the neutron and the photon component of mixed fields, is the 'double counting' of the dose equivalent due to neutron-induced photons. The relevance of this conceptual problem for calibrations in mixed-field dosimetry was analysed.

Wendelstein 7-X (W7-X) is a large optimized stellarator (B=2.5T, V=30m3) aiming at demonstrating the reactor relevance of the optimized stellarators. In 2015 W7-X will begin its first operation phase (OP1.1) with five inertially cooled inboard limiters made of graphite. Assuming the heat loads can be spread out evenly between the limiters, 1 second discharges at 2 MW of ECRH heating power could be run in OP1.1. The expected plasma parameters will be sufficient to demonstrate the readiness of the installed diagnostics and even to run a first physics program. The diagnostics available for this first operation phase, including some special limiter diagnostics, and their capabilities are being presented. A shorter version of this contribution is due to be published in PoS at: 1st EPS conference on Plasma Diagnostics

A detailed analysis of the neutron radiation field was performed at selected positions inside the Krummel boiling water reactor. The measurements were performed with the PTB Bonner sphere spectrometer and with a newly developed directional neutron spectrometer based on silicon detectors mounted onto the surface of a 30 cm diameter polyethylene sphere. Both, angle-integrated and angle-differential spectral neutron fluences were determined in this way.

An overview of the diagnostics which are essential for the first operational phase of Wendelstein 7-X and the set of diagnostics expected to be ready for operation at this time are presented. The ongoing investigations of how to cope with high levels of stray Electron Cyclotron Resonance Heating (ECRH) radiation in the ultraviolet (UV)/visible/infrared (IR) optical diagnostics are described.

A new thermal neutron calibration facility based on a moderator assembly has been set up at PTB. It consists of 16 (241)Am-Be radionuclide sources mounted in a graphite block, 1.5 m wide, 1.5 m high and 1.8 m deep. The sources are distributed to eight different positions, at a mean distance of ∼1.25 m from the front face of the moderator. The neutron field at the reference position, 30 cm in front of the moderator device and 75 cm above the floor, has been characterised using calculations, Bonner sphere measurements and gold foil activation. First results are shown. The field is highly thermalised: 99 % in terms of fluence. It is quite homogenous within a 20 cm×20 cm area, but the absolute value of the thermal neutron fluence rate is small and yields an ambient dose equivalent rate of 3 µSv h(-1).

A prototype of a highly sensitive active personal neutron dosemeter has been developed. It consists of a stack of four silicon detectors sandwiched between layers acting as neutron converters, moderators and absorbers. Its response to quasi-monoenergetic neutrons with energies up to 45 MeV and photons with energies up to 7 MeV has been measured and/or calculated for different angles of incident radiation. The personal dose equivalent determined from the readings obtained in some fields with broad energy distributions deviates by less than 30% from the reference values, both for normal incidence and incidence at 60° to the normal. The detectibn threshold is about 3 μSv for fast neutrons, 1 μSv for intermediate neutrons and 0.007 μSv for thermal neutrons, even in mixed fields with a photon dose higher by a factor of 20. In addition, the evaluation procedures described give spectral and directional information about the field.

In order to calibrate more accurately the neutron dosemeters involved in radiation protection, the concept of 'Realistic Neutron Calibration Fields' is considered as an appropriate alternative solution, making necessary new irradiation facilities which generate well-characterised neutron fields with energy and angular distributions replicating more closely practical workplace conditions. Several experienced laboratories have collaborated on a European project and proposed various approaches which are reviewed in this paper. A short description of the facilities currently in operation is given as well as a few characteristics of the available radiation fields. This description of the state of art is followed by a discussion of the problems to be solved for using such facilities for calibration purposes according to well-specified calibration procedures.

The applicability of CR-39 nuclear track detectors to the field of microdosimetry was experimentally investigated through a series of tests with monoenergetic charged particle fields. A special etching technique (intermittent etching and cleaning etch steps) was devised and employed to determine LET values along individual tracks on irradiated detector plates. The range of measurable LET values was inferred from the analysis of the etched track diameters created by monoenergetic protons, alpha particles and fission fragments. Based on these calibrations, measurements of track densities and LET distributions were performed at different depths in a CR-39 stack irradiated with 62 MeV protons.

The European Commission has funded within its 6th Framework Programme a three-year project (2005–2007) called CONRAD, COordinated Network for RAdiation Dosimetry . A major task of the CONRAD Work Package “ complex mixed radiation fields at workplaces ” was to organise a benchmark exercise in a workplace field at a high-energy particle accelerator where neutrons are the dominant radiation component. The CONRAD benchmark exercise took place at the Gesellschaft fur Schwerionenforschung mbH (GSI) in Darmstadt, Germany in July 2006. In this paper, the results of the spectrometry using four extended -range Bonner sphere spectrometers of four different institutes are reported. Outside Cave A the neutron spectra were measured with three spectrometers at six selected positions and ambient dose equivalent values were derived for use in the intercomparison with other area monitors and dosemeters. At a common position all three spectrometers were used to allow a direct comparison of their results which acts as an internal quality assurance. The comparison of the neutron spectra measured by the different groups shows very good agreement. A detailed analysis presents some differences between the shapes of the spectra and possible sources of these differences are discussed. However, the ability of Bonner sphere spectrometers to provide reliable integral quantities like fluence and ambient dose equivalent is well demonstrated in this exercise. The fluence and dose results derived by the three groups agree very well within the given uncertainties, not only with respect to the total energy region present in this environment but also for selected energy regions which contribute in certain strength to the total values. In addition to the positions outside Cave A one spectrometer was used to measure the neutron spectrum at one position in the entry maze of Cave A. In this case a comparison was possible to earlier measurements.

We started a research program using heavy ion beams at the GSI Darmstadt accelerator to investigate radiation effects of heavy ions in microelectronic devices. The understanding of these radiation effects is of particular importance to estimate the radiation rise for microelectronic parts exposed to the cosmic radiation during space missions. In order to expose static RAM devices to heavy ion beams a test system was installed. Additionally we use CCD image sensors to measure the amount of charge deposited inside the sensitive volume of single picture elements. Measurements will be performed with ions of different charge and energy up to 1 GeV/N to investigate the LET dependence of the effects and possible influence of the track structure. The experimental setup is described in this paper and first results are presented.

A new detector system has been developed for time resolved flux measurements of collimated D-D neutrons in large magnetic confinement fusion experiments. The novel detection concept, called the special absorber neutron detector moderator assembly, is to place a scatterer behind a collimator and to detect the scattered neutrons in a small Bonner sphere. The system has been optimized by means of the Monte Carlo neutron photon transport code (MCNP) simulations and is capable to be extended for a neutron profile camera. First tests and calibration measurements of a system using a 3 in. Bonner sphere have been carried out in the 2.5 MeV neutron field at the accelerator facility of the Physikalisch-Technische Bundesanstalt in Braunschweig. The numerical and experimental results are presented. The measurements differ from the calculated values by a factor of about 1.09. It is questionable if these discrepancies can be explained by differences in the shielding, moderator and detector characteristics employed in t...

In this paper we present a signaling mechanism of spacial divided network conditions in order to guarantee quality of service (QoS) in a vehicular ad hoc network (VANET) The target application shares information of sensed objects in the surrounding of the vehicles with its VANET neighbor nodes Therefore each vehicle broadcasts information of its surrounding periodically which leads to an unscalable bandwidth consumption as the density of communication nodes rises A higher network load will also lead to a higher latency of the transmitted data as the probability is that nodes have to wait for a free channel. The latency of data acquired from onboard sensors is critical if it is shared with other nodes as the validity of the data is1 ow. We present a signaling method based on a spatial partitioning in order to detect redundant source nodes for the same information. Avoiding redundant broadcasts will limit the application's bandwidth consumption and therefore the latency of the messages can be improved.

In recent years research on active safety systems with the main focus on environment sensing has been done. Therefore vehicles are equipped with sensors which record information about the nearby traffic situation and possible hazards. For anticipatory driving additional information outside of the range of the sensors' area needs to be collected. This can be done by introducing data transfer between vehicles, which allows to gather data of a larger area and therefore improves the anticipatory capabilities of the system. One main aspect in the data exchange between vehicles is the organization of the access to the medium. It has to be able to cope with all the problems of mobile ad-hoc networks. Especially the hidden station problem is an important factor in vehicular ad-hoc networks (VANETs). But also the high density of nodes, high dynamics and a limited data rate require a fair and efficient access to the medium. In this paper we present a medium access scheme for vehicular ad-hoc networks which is based on clustering of the vehicles. Thus the effect of hidden stations can be minimized, which leads to a more reliable data transfer than IEEE 802.11 based systems can provide.

Vehicle-to-vehicle communication is a promising technology for enhanced road safety as it provides the possibility to get a detailed knowledge about the traffic situation a long way ahead. Vehicles transmit information about nearby dangers like obstacles on the road as well as warning messages over long distances to all vehicles in a certain area. Therefore the dissemination of the data has to be done in broadcast transmission. This transmission concept causes severe problems regarding the organization of the medium access. The often used RTS/CTS mechanism is no longer feasible, which is especially problematic in road scenarios, where the hidden station problem is a major cause of data loss due to collisions. In addition the regarded data makes high demands on the provided quality of service. Especially reliability and delay are crucial for the efficiency of the warning system. In this paper we introduce a concept for a medium access control which minimizes the effects of the hidden station problem by introducing a clustering scheme. Therefore clusterheads among the vehicles are selected, which are then responsible for assigning bandwidth to the other vehicles in their clusters. This paper presents an algorithm for selecting the clusterheads along with a concept for assigning bandwidth to the nodes.

The European Commission is funding within its Sixth Framework Programme a three-year project (2005-2007) called CONRAD, COordinated Network for RAdiation Dosimetry. The organisational framework for this project is provided by the European Radiation Dosimetry Group EURADOS. One task within the CONRAD project, Work Package 6 (WP6), was to provide a report outlining research needs and research activities within Europe to develop new and improved methods and techniques for the characterisation of complex radiation fields at workplaces around high-energy accelerators, but also at the next generation of thermonuclear fusion facilities. The paper provides an overview of the report, which will be available as CERN Yellow Report. © The Author 2007. Published by Oxford University Press. All rights reserved.

In this poster we present a cross-layer design between packet routing and medium access control (MAC) for a vehicular ad hoc network (VANET) in order to guarantee special quality of service (QoS) requirements. As precondition we consider vehicles equipped with driving- assistant-systems that exchange environmental object information through the network. By the use of wireless communication the vehicles can share their environment data and extend their environment model. This collected object information gets obsolete after some time because of the fast changing surroundings of a vehicle. Therefore it should be distributed to other vehicles with a lower delay than the data gets outdated. This introduces a special low delay QoS requirement the VANET has to provide to the application.

The new CANEL/T400 facility has been set-up at the Institute for Radiological Protection and Nuclear Safety (IRSN) to produce a realistic neutron field. The accurate characterisation of this neutron field is mandatory since this facility will be used as a reference neutron source. For this reason an international measuring campaign, involving four laboratories with extensive expertise in neutron metrology and spectrometry, was organised through a concerted EUROMET project. Measurements were performed with Bonner sphere (BS) systems to determine the energy distribution of the emitted neutrons over the whole energy range (from thermal energy up to a few MeV). Additional measurements were performed with proton recoil detectors to provide detailed information in the energy region above 90 keV. The results obtained by the four laboratories are in agreement with each other and are compared with a calculation performed with the MCNP4C Monte-Carlo code. As a conclusion of this exercise, a reliable characterisation of the CANEL/T400 neutron field is obtained.

A directional spectrometer that uses a superheated emulsion of dichlorotetrafluoroethane at the centre of a 30 cm diameter moderating-sphere of nylon-6. The system has a telescope-design wherein the detector views a narrow solid angle of about 1/6 steradians. The hydrogenous sphere effectively attenuates laterally incident neutrons, thus providing a strong angular dependence of the response. The central detector is sequentially operated at seven temperatures between 25 and 55 degrees C in order to generate a matrix of nested response functions suitable for few-channel spectrometry. The response matrix of the system has been determined by calibrations with monoenergetic neutrons and by Monte Carlo neutron transport calculations. The double-differential unfolding method developed for this system applies the principle of maximum entropy and allows for the rigorous use of all a priori information. The spectrometer is intended for use in the mixed neutron/photon fields encountered in the nuclear power industry, being suitable for spatially distributed radiation sources with maximum neutron energies up to 10 MeV.

The long duration exposure facility (LDEF), launched into a 258 nautical mile orbit with an inclination of 28.5 degrees, remained in space for nearly 6 yr. The 21,500 lb NASA satellite was one of the largest payloads ever deployed by the Space Shuttle. LDEF completed 32,422 orbits and carried 57 major experiments representing more than 200 investigators from 33 private companies, 21 universities and nine countries. The experiments covered a wide range of disciplines including basic science, electronics, optics, materials, structures and power and propulsion. A number of the experiments were specifically designed to measure the radiation environment. These experiments are of specific interest, since the LDEF orbit is essentially the same as that of the Space Station Freedom. Consequently, the radiation measurements on LDEF will play a significant role in the design of radiation shielding of the space station. The contributions of the various authors presented here attempt to predict the major aspects of the radiation exposure received by the various LDEF experiments and therefore should be helpful to investigators who are in the process of analyzing experiments which may have been affected by exposure to ionizing radiation. The paper discusses the various types and sources of ionizing radiation including cosmic rays, trapped particles (both protons and electrons) and secondary particles (including neutrons, spallation products and high-LET recoils), as well as doses and LET spectra as a function of shielding. Projections of the induced radioactivity of LDEF are also discussed.

We analyzed several CR39 detector foils which had been exposed to the cosmic radiation during the Spacelab 1 mission. Particle tracks in the CR39 were detected and measured by an automatic measuring system. Methods of separation of the tracks from background structures on the foil surface which were also detected by the system are discussed in this paper. Due to the low registration threshold of the CR39 we can measure minimum ionizing iron nuclei, which form a peak in the differential LET-spectrum. Thus we get a point of calibration for each measured detector foil. An example of a measured LET-spectrum is presented and discussed.

We developed a completely automatic scanning and measuring system for nuclear track detectors. The video pictures of particle tracks seen through a microscope are digitized and analyzed in real time by MC 68000 microprocessors. In this paper we present some new developments: The picture analysis software is extended to separate overlapping tracks and to measure elliptical tracks even if these are flawed by surface structures. A software autofocus, a faster hardware version based on the contrast and a modified commercial laser autofocus are now available. A new picture analysis system based on the faster 32-bit microprocessor MC 68020 will operate on two pictures of 1024 × 1024 pixels resident in memory together. This will allow three dimensional track measurements.

The radiobiological properties of the heavy ions of cosmic radiation were investigated on Spacelab 1 by use of biostacks, monolayers of biological test organisms sandwiched between thin foils of different types of nuclear track detectors. Biostacks were exposed to cosmic radiation at several locations with different shielding environments in the module and on the pallet. Evaluations of the physical and biological components of the experiment to date indicate that in general they survived the spaceflight in good condition. Dosimetric data are presented for the different shielding environments.