Röntgen- Photoelektronenspektroskopie mit Silizium-Photomultipliern

In dieser Arbeit wird untersucht, inwieweit es möglich ist, mit einer Kombination aus Silizium-Photomultipliern und Hochspannungsfluoreszenzschirm einen Detektor zu realisieren, der wesentlich langlebiger ist als die üblicherweise verwendeten Kanalelektronenvervielfacher. Dazu wird ein Detektorprototyp entworfen, konstruiert und getestet. Zum Test des Detektors wird eine Vakuumkammer mit einem Elektronenstrahlsystem aufgebaut. Es wird die Homogenität und Linearität des gefertigten Leuchtschirms geprüft, sowie die Abwesenheit von Störfeldern innerhalb des Detektorprototyps. Zur Auslese der Silizium-Photomultiplier werden elektronische Komponenten des Cherenkov-Teleskops FACT verwendet. Dazu wird spezielle Steuerungs- und Auslesesoftware entwickelt. Am Elektronenspeicherring DELTA wird mit dem Detektorprototyp das Signal der Photoelektronen nachgewiesen und damit gezeigt, dass es prinzipiell möglich ist auch ohne Elektronenvervielfachung ein Spektrum mit Silizium-Photomultipliern zu messen. Aus der Qualität der nachgewiesenen Spektren werden Schlussfolgerungen für ein neues, verbessertes Detektordesign gezogen

New operational dose quantity ambient dose H* in the context of galactic cosmic radiation in aviation

The International Commission on Radiation Units and Measurements recently proposed new operational quantities for external radiation exposure. Among those, the ambient dose is intended to replace the ambient dose equivalent as estimator for the effective dose. Following its definition, the measurement of the ambient dose requires a much more detailed knowledge about the radiation field than the ambient dose equivalent. The implications for radiation protection in aviation concerning galactic cosmic radiation that would follow the adoption of the ambient dose as operational quantity at flight altitudes were investigated in this work using model calculations. It was found that the ambient dose is about 10% higher than the ambient dose equivalent for conditions relevant in commercial aviation and overestimates the effective dose by about 30

Are Cosmic Neutrons a Threat to Pacemakers? - Testing SRAMs with an Am-Be Neutron Source

Introduction: Effects of cosmic radiation can impair pacemakers and other active implanted medical devices (AIMDs). There are several publications about devices showing irregular function during or after air-travel most likely caused by subatomic particles from space (Clair, Williams, Hygaard, & Saavedra, 2013; Ferrick, Bernstein, Aizer, & Chinitz, 2008; Paz, Teodorovich, Kogan, & Swissa, 2017). Furthermore, numerous radiation related malfunctions of unknown origin have been reported in the Manufacturers and User Facility Device Experience (MAUDE) database in recent years, some of which caused symptoms or led to the exchange of the device. These described malfunctions are most likely caused by SEE in the memory of the AIMD. Severe errors in the executed stimulation program are usually detected and corrected by the device itself through a power-on-reset. However, this procedure switches it to safety mode where stimulation parameters can be changed. Ultimately, this can lead to the pacemaker syndrome or unnecessary shocks of defibrillators. The problem of the susceptibility to particle radiation of medical devices is already well-known from radiation therapy. Therefore, various protective measures have been established for patients in recent years to avoid complications in this radiation environment (Gauter-Fleckenstein et al., 2015). Nevertheless, for developing and applying radiation protection measures to patients with AIMDs in further radiation environments, such as at aviation altitudes or during severe space weather events, the assessment of the risk of malfunction for AIMDs is necessary. [...

REFLECT – Research flight of EURADOS and CRREAT: Intercomparison of various radiation dosimeters onboard aircraft

Aircraft crew are one of the groups of radiation workers which receive the highest annual exposure to ionizing radiation. Validation of computer codes used routinely for calculation of the exposure due to cosmic radiation and the observation of nonpredictable changes in the level of the exposure due to solar energetic particles, requires continuous measurements onboard aircraft. Appropriate calibration of suitable instruments is crucial, however, for the very complex atmospheric radiation field there is no single reference field covering all particles and energies involved. Further intercomparisons of measurements of different instruments under real flight conditions are therefore indispensable. In November 2017, the REFLECT (REsearch FLight of EURADOS and CRREAT) was carried out. With a payload comprising more than 20 different instruments, REFLECT represents the largest campaign of this type ever performed. The instruments flown included those already proven for routine dosimetry onboard aircraft such as the Liulin Si-diode spectrometer and tissue equivalent proportional counters, as well as newly developed detectors and instruments with the potential to be used for onboard aircraft measurements in the future. This flight enabled acquisition of dosimetric data under well-defined conditions onboard aircraft and comparison of new instruments with those routinely used. As expected, dosimeters routinely used for onboard aircraft dosimetry and for verification of calculated doses such as a tissue equivalent proportional counter or a silicon detector device like Liulin agreed reasonable with each other as well as with model calculations. Conventional neutron rem counters underestimated neutron ambient dose equivalent, while extended-range neutron rem counters provided results comparable to routinely used instruments. Although the responses of some instruments, not primarily intended for the use in a very complex mixed radiation field such as onboard aircraft, were as somehow expected to be different, the verification of their suitability was one of the objectives of the REFLECT. This campaign comprised a single short flight. For further testing of instruments, additional flights as well as comparison at appropriate reference fields are envisaged. The REFLECT provided valuable experience and feedback for validation of calculated aviation doses

Validation of a radiative transfer model with measurements of UV Radiation inside a commercial aircraft

A radiative transfer model for the determination of UV radiation on arbitrarily oriented surfaces is validated by spectral measurements taken directly on the inner surface of a cockpit window of an Airbus A321-231 during a flight from Frankfurt, Germany to Málaga, Spain on 23 August, 2018. The simulations consider the UV spectral range from 290 nm to 400 nm and take into account both the measured spectral transmittance of a cockpit window as well as its construction-related orientation. Comparisons are performed for selected route segments with largely cloud-free conditions. The cruising level of the Airbus on these segments was nearly constant between 11.27 km and 11.29 km. UV irradiance measurements at the cockpit window give values within a range of 19 W/m2 and 26 W/m2. The comparison of modelled and measured irradiances show a very good agreement, i.e. the relative differences between simulated and measured values range from -2.1 % to +4.3 %. In addition, horizontally and vertically oriented sensors are simulated for the same flight. The validation results generally underpin the application potential of the model. As an example of this, UV irradiances incident on differently oriented surfaces, as could occur inside and outside of a future flying taxi on a short-haul flight between Munich and Augsburg at low cruising level, are shown

Operational Instruments for Measuring SWx Radiation Impacts at Aviation Altitudes

The interaction of cosmic radiation with constituents of the atmosphere creates a secondary particle field which contributes to the radiation exposure of aircrew and passengers. The assessment of this exposure can be achieved by model calculations and measurements. Reliable measurements of dose quantities in the complex radiation field at aviation altitudes require qualified radiation measuring instruments operated under well-defined flight and SWx conditions. A set of several types of such radiation detectors has been used on commercial airline flights as well as in research aircraft by the German Aerospace Center (DLR) for many years. The goal of these measuring flights has been the acquisition of high quality dose data for scientific investigations and operational radiation protection purposes. The detector types used, i.e. Hawk, a tissue equivalent proportional counter (TEPC), Liulin, a silicon semiconductor detector, LB 6411-Pb, a neutron probe, and bubble detectors are introduced

Measurement of UV radiation in commercial aircraft

Ultraviolet radiation (UVR) is significantly higher at aviation altitudes with respect to sea level. Cockpit windshields protect pilots from UV-B radiation but studies have shown that this is not necessarily the case for UV-A radiation. This work investigates the spectral properties of several windshields under flight conditions. Only one of the investigated windshields showed good UV-A attenuation. Furthermore, the altitude dependence of UV-A irradiance behind a windshield was measured with high spatial resolution. Measurements of the maximal UV irradiance behind the windshield surfaces and at the pilot’s position are compared to the recommendations by the International Commission on Non-Ionising Radiation Protection. Some recommended limits were exceeded at the surface of the windshields with direct sunlight and a large field of view. At the pilot’s position, with a more realistic field of view, the unweighted recommended level could have been exceeded within tens of minutes by looking in the direction of the Sun without visor or other protective measures. The weighted recommended maximal UVR exposure was not exceeded, neither with the use of the visor at the pilot’s position nor without it. The use of the visor for filtering direct sunlight was very effective in terms of UV-A reduction

Testing an active control device for bit flips in neutron and heavy ion radiation environments

Effects of particle radiation can impair active implanted medical devices (AIMDs) such as pacemakers, or ICDs. Single event effects can affect the device memory and can ultimately lead to the pacemaker syndrome or unnecessary shocks of defibrillators. The assessment of the risk of malfunctions in those devices for defined radiation environments is a prerequisite for developing corresponding radiation protection measures. For this purpose, the devices are to be exposed to neutron and proton radiation fields to determine the cross sections for radiation related malfunctions. However, the AIMDs can only be read out after irradiation. Therefore, an active control device has been developed to assure a reasonable amount of bit flips in the particle energies to be examined. The set up contains 13 commercial-of-the-shelf SRAMs of different types and sizes which are connected to a microcontroller. A pattern of alternating bits is written on the chips and read out constantly during or cumulative after irradiation. Any variations from the original pattern are logged. Firstly, the device was exposed to an Am-Be source to investigate the response to neutrons and the effect of constant irradiation over several hours. Secondly, the set up was irradiated with 48 MeV/u carbon ions for testing an expected high rate of bit flips in a short amount of time. In both cases a reasonable amount of bit flips was logged for all SRAMs. However, a higher sensitivity to carbon ions than to neutrons has been observed. A balanced ratio between 1-0 and 0-1 bit flips has been found as well as an even distribution over all blocks of addresses. All in all, no permanent damage has been observed with the fluences used so far. The detection of bit flips was Poisson distributed and stable over time. Furthermore, the device has been demonstrated to process high numbers of bit flips in a short amount of time. In conclusion, the developed device can be used as an active control monitor for bit flips in neutron and heavy ion radiation environment

Between Sea Level and the ISS: Radiation Measurements in the SAA Region at Flight Altitudes

The South Atlantic Anomaly (SAA) is a geographical region over the South Atlantic Ocean where the inner Van Allen radiation belt extends down particularly close to Earth. This leadsto highly increased levels of ionizing radiation and related impacts on spacecraft in Low Earth Orbits, e.g., correspondingly increased radiation exposure of astronauts and electronic components on the International Space Station. According to an urban legend, the SAA is also supposed to affect the radiation field in the atmosphere even down to the altitudes of civil aviation. In order to identify and quantify any additional contributions to the omnipresent radiation exposure due to the Galactic Cosmic Radiation at flight altitudes, comprehensive measurements were performed crossing the geographical region of the SAA at an altitude of 13 km in a unique flight mission—Atlantic Kiss. No indication of increased radiation exposure was found

Impact of the South Atlantic Anomaly on radiation exposure at flight altitudes during solar minimum

Abstract The South Atlantic Anomaly (SAA) is a geographical region over the South Atlantic Ocean where the inner Van Allen radiation belt extends down particularly close to Earth. This leads to highly increased levels of ionizing radiation and related impacts on spacecraft in Low Earth Orbits, e.g., correspondingly increased radiation exposure of astronauts and electronic components on the International Space Station. According to an urban legend, the SAA is also supposed to affect the radiation field in the atmosphere even down to the altitudes of civil aviation. In order to identify and quantify any additional contributions to the omnipresent radiation exposure due to the Galactic Cosmic Radiation at flight altitudes, comprehensive measurements were performed crossing the geographical region of the SAA at an altitude of 13 km in a unique flight mission—Atlantic Kiss. No indication of increased radiation exposure was found