Papers by Markus Köhli
Footprint characteristics revised for field-scale soil moisture monitoring with cosmic-ray neutrons
Cosmic-ray neutron probes are widely used to monitor environmental water content near the surface... more Cosmic-ray neutron probes are widely used to monitor environmental water content near the surface. The method averages over tens of hectares and is unrivaled in serving representative data for agriculture and hydrological models at the hectometer scale. Recent experiments, however, indicate that the sensor response to environmental heterogeneity is not fully understood. Knowledge of the support volume is a prerequisite for the proper interpretation and validation of hydrogeophysical data. In a previous study, several physical simplifications have been introduced into a neutron transport model in order to derive the characteristics of the cosmic-ray probe's footprint. We utilize a refined source and energy spectrum for cosmic-ray neutrons and simulate their response to a variety of environmental conditions. Results indicate that the method is particularly sensitive to soil moisture in the first tens of meters around the probe, whereas the radial weights are changing dynamically with ambient water. The footprint radius ranges from 130 to 240m depending on air humidity, soil moisture and vegetation. The moisturedependent penetration depth of 15 to 83cm decreases exponentially with distance to the sensor. However, the footprint circle remains almost isotropic in complex terrain with nearby rivers, roads or hill slopes. Our findings suggest that a dynamically weighted average of point measurements is essential for accurate calibration and validation. The new insights will have important impact on signal interpretation, sensor installation, data interpolation from mobile surveys, and the choice of appropriate resolutions for data assimilation into hydrological models. More Coauthors: M. Zreda, U. Schmidt, P. Dietrich, S. Zacharias
The 10B based Jalousie neutron detector – An alternative for 3He filled position sensitive counter tubes
Over the last decades 3He filled proportional counter tubes were the working horse employed to se... more Over the last decades 3He filled proportional counter tubes were the working horse employed to serve as neutron counters especially in cases where large area coverage was required. Today the lack of 3He demands the development of an alternative technology. Here we present a prototype neutron detector that is based on a concept with solid 10B as neutron converter and aims for large area neutron detection applications. We report on first experimental results obtained with this prototype to demonstrate the feasibility and operational readiness of our concept.
Absolute effciency measurements with the 10B based Jalousie detector
The 10B based Jalousie detector is a replacement for 3He counter tubes, which are nowadays less a... more The 10B based Jalousie detector is a replacement for 3He counter tubes, which are nowadays less affordable for large area detectors due to the 3He crisis. In this paper we investigate and verify the performance of the new 10B based detector concept and its adoption for the POWTEX diffractometer, which is designed for the detection of thermal neutrons with predicted detection efficiencies of 75–50% for neutron energies of 10–100 meV, respectively. The predicted detection efficiency has been verified by absolute measurements using neutrons with a wavelength of 1.17 Å (59 meV)
An end cap module for the LC-TPC Large Prototype (LP) was designed and constructed
consisting of ... more An end cap module for the LC-TPC Large Prototype (LP) was designed and constructed
consisting of a stack of three Gas Electron Multipliers and eight Timepix
chips. This module was placed in the LP and the setup was tested with the 5 GeV
electron test beam at DESY, Hamburg
The EUDET-project was launched to create an infrastructure for developing and testing new and
adv... more The EUDET-project was launched to create an infrastructure for developing and testing new and
advanced detector technologies to be used at a future linear collider. The aim was to make possible
experimentation and analysis of data for institutes, which otherwise could not be realized due to lack
of resources. The infrastructure comprised an analysis and software network, and instrumentation
infrastructures for tracking detectors as well as for calorimetry.
Teaching Documents by Markus Köhli
Es werden die wichtigsten statistischen Methoden zusammengefasst und erklärt, welche zur Auswertu... more Es werden die wichtigsten statistischen Methoden zusammengefasst und erklärt, welche zur Auswertung von Versuchen des Fortgeschrittenen-Praktikums des Studiengangs Physik notwendig sind.
Thesis Chapters by Markus Köhli
Entwicklung einer Labortestkammer für mikrostrukturierte Gasdetektoren mit hochpixellierter Auslese und Charakterisierung postprozessierter TimePix-Chips unter Verwendung von GEM-Folien zur Gasverstärkung
Ziel dieser Arbeit lag in der Untersuchung der Eignungsfähigkeit des TimePix-Chips hinsichtlich ... more Ziel dieser Arbeit lag in der Untersuchung der Eignungsfähigkeit des TimePix-Chips hinsichtlich des Einsatzes als Auslese für mikrostrukturierte Gasdetektoren. In Ermangelung des zur Durchführung von Experimenten passenden Equipmentes galt es zu Beginn, eine Experimentierumgebung zu scha en.
Resultierend aus diesem Umstand schrieb die Agenda zuerst die Konstruktion einer geeigneten Testkammer
vor, um nachfolgend Experimente und deren Auswertung zu ermöglichen. So gliedert sich diese Arbeit in die einzelnen Aspekte von der Konzeption des Experimentes bis zur letztlichen Analyse. Die Ausführung dieser Arbeit beginnt damit, dass in den Grundlagen der physikalische Zusammenhang
zur grundsätzlichen Art der Funktion des Detektors hergestellt und der technologische Rahmen dargelegt wird. Der erste Teil führt die Konzeption des Aufbaus der Kammer aus, welcher sich mit dem Erstellen und Untersuchen eines Simulationsmodelles beschäaftigt. Folgend wird der finite Corpus besprochen, zu welchem gleichermaßen die zugehörige Sensorik, Elektrik und Datennahmegeräte zählen. Nach dem Durchführen des Experimentes setzt die Charakterisierungsarbeit ein Präparieren der erhaltenen Rohdaten voraus. Es existiert aus diesem Grund ein Zwischenabschnitt, welcher sich mit der zu diesem Zweck erstellten Software auseinandersetzt. Letztendliches Ziel war die Untersuchung von TimePix-Chips, welche durch Techniken der Postprozessierung modi ziert wurden. Der TimePix-Chip wurde als hochpixellierter ladungsemp findlicher Detektor
konzipiert und soll zusammen mit der aktuellen Generation mikrostrukturierter Gas-Elektronen-Verstärkern (GEMs) derart kombiniert werden, dass diese eine digitale, hochaufgelöste Auslese für Driftkammern bilden. Die Motivation jeglicher Postprozessierung liegt darin, dass sie eine bessere Adaption
des Grundkörpers des TimePix-Chips an die Granularität und physikalischen Anforderungen der GEM-Struktur scha ffen.
Talks by Markus Köhli
Accurate soil moisture (SM) monitoring is key in irrigation as it can greatly improve water use e... more Accurate soil moisture (SM) monitoring is key in irrigation as it can greatly improve water use efficiency. Recently, Cosmic-Ray Neutron Sensors (CRNS) have been recognized as a promising tool in SM monitoring due to their large footprint of several hectares and half a meter in depth. CRNS have great potential for irrigation applications as to the non-invasive nature of the method and the low-maintenance independently operating sensors. From the initial focus on hydrological research Cosmic-Ray Neutron Sensors are emerging into applied agricultural contexts, for example irrigation management and soil moisture mapping. Examples are the integration of CRNS into the SWAMP (LoRa) or the Nb-IoT network of the German Chamber of Agriculture. This project, called ADAPTER, involves the development and provision of innovative simulation-based information products for weather- and climate-resilient agriculture. These are daily (”soil”) weather and comprehensive long-term climate change information available to the agricultural community and all interested parties as easy-to-use analyses, data products, and information interfaces. Still, challenges for CRNS are posed for scenarios especially for irrigated fields with a size smaller than the CRNS footprint or heterogeneous conditions with respect to the biomass distribution.
High Resolution Neutron Detection, 2018
The world of detectors used in thermal neutron scattering instrumentation has changed. By alerts ... more The world of detectors used in thermal neutron scattering instrumentation has changed. By alerts on the future Helium-3 supply, critical to perspectives of the large-scale research infrastructures, the run on substitutional technologies started. Most of the solutions could be adapted from developments of particle physics and are comprised of one or more layers of Boron-10. The Time Projection Method achieves a very high resolution by projecting ionization tracks onto a readout with dense spatial and time information. The university of Bonn is developing a novel system employing the TimePix technology - CMOS based chips with 55 micrometer sized pixels operated at clock speeds up to 80 MHz. In a first prototype with 8 TimePix chips, which are arranged in parallel to a boron layer, the track topology with this unrivaled high resolution has been studied. By reconstructing the origin of the conversion ions a time resolution of <50 ns and a spatial resolution of 100 micrometer has been achieved.
Soil Moisture Measurement at the hectometer scale using CRNS for mobile applications, 2018
The method of cosmic ray neutron sensing - soil moisture measurement at the hectometer scale non-... more The method of cosmic ray neutron sensing - soil moisture measurement at the hectometer scale non-invasively has turned out to be feasible by detecting environmental albedo neutron density. The key feature of the method is the exceptionally different behavior of hydrogen in its reflction power of neutrons generated by cosmic rays. It slows down fast neutrons whereas any other heavier element independent of the chemical composition rather reflects them. In the recent years the understanding of neutron transport by Monte-Carlo simulations led to major advancements in precision, which have been successfully targeted meanwhile by a manifold of experiments. Whereas the homogeneous conditions are well understood, inhomogeneous topologies are now in the focus of research. In our case these are applications for partial snow cover and mobile surveys, where the influence of the road material, which biased results towards lower soil moisture values, could be calculated, measured and analytically understood. Here we present the actual status of the method especially with respect to inhomogeneous terrain.
Cosmic-Ray Neutron Sensing with novel neutron detectors, 2019
The method of cosmic ray neutron sensing - measuring soil moisture non-invasively at the hectomet... more The method of cosmic ray neutron sensing - measuring soil moisture non-invasively at the hectometer scale has turned out to be feasible by detecting the environmental albedo neutron density. The key feature of the method is that neutrons generated by cosmic rays show an exceptionally different behavior interacting with hydrogen. It slows down fast neutrons whereas any other heavier element, independent of the chemical composition, rather reflects them. In the recent years the understanding of neutron transport by Monte Carlo simulations led to major advancements in precision, which have been successfully targeted meanwhile by a manifold of experiments.
We are now developing boron-lined neutron detectors using spin-off technologies from the upcoming European Spallation Source and instrument design experience from past experiments. These detectors shall also offer an alternative platform to current Helium-3 based systems. In order to reduce costs we recently have developed readout electronics and data acquistion systems based on Arduino microcontrollers.
Arduino-based readout electronics for particle detectors, 2019
With the Arduino open source electronics platform microcontrollers have become a comparably easy-... more With the Arduino open source electronics platform microcontrollers have become a comparably easy-to-use tool for rapid prototyping and implementing creative solutions. Their stability especially qualifies them to be used for slow control units. Yet, running at 16 MHz, the capabilities can be extended to data taking and signal analysis at decent rates. Such devices in combination with dedicated frontend electronics can offer low cost alternatives for student projects and independently operating small scale instrumentation. We present two projects, which cover as well the readout of helium-3 and boron-10 proportional counters as of scintillators or wavelength shifting fibers with Silicon Photomultipliers.
The nCatcher combines commercially available analog electronics and the Arduino nano enabling pulse shape analysis for proportional counters. The frontend integrates and shapes pulses to microseconds in order to use the Arduino's signal analysis capabilities - time over threshold measurement and a 10-bit analog to digital converter. Combining these two parameters allows for effective discrimination between different radiation types by estimating the total deposited energy (E) of incoming radiation as well as the mean energy loss per distance (dE/dx). This makes the device suitable for low to medium rate environments, where a good signal noise is a crucial.
With the SiPMTrigger we have realized a small scale design for triggering or vetoing. It consists of a custom mixed signal frontend board featuring signal amplification, discrimination and a coincidence unit. An Arduino MEGA digitally adjusts the thresholds of both channels and measures the trigger rate up to 200 kHz.
High Resolution Neutron Detection by the yTPC method, 2018
The world of detectors used in thermal neutron scattering instrumentation has changed. By alerts ... more The world of detectors used in thermal neutron scattering instrumentation has changed. By alerts on the future Helium-3 supply, critical to perspectives of the large-scale research infrastructures, the run on substitutional technologies started. Most of the solutions could be adapted from developments of particle physics and are comprised of one or more layers of Boron-10. The Time Projection Method achieves a very high resolution by projecting ionization tracks onto a readout with dense spatial and time information. The University of Bonn is developing a novel system employing the Timepix technology - CMOS based chips with 55 micrometer sized pixels operated at clock speeds up to 80 MHz. Each matrix of 256 x 256 pixels is equipped with an InGrid - microstructured aluminum meshes 50 micrometer ontop of the pixels serving as a charge amplifier. In a first prototype with 8 Timepix chips, which are arranged in parallel to a boron layer, the track topology with this unrivaled high resolution has been studied. By reconstructing the origin of the conversion ions a time resolution of <50 ns and a spatial resolution of 100 micrometer has been achieved. As this setup now allows the full reconstruction of the conversion tracks down to the electron level the understanding of the track topology can help interpreting the signals in more coarsely resolved systems and address the question: what is realistically the resolution limit for boron-lined gas detectors?
Novel Neutron Detectors based on the Time Projection Method
The world of detectors used in thermal neutron scattering instrumentation has changed. By alerts ... more The world of detectors used in thermal neutron scattering instrumentation has changed. By alerts on the future Helium-3 supply, critical to perspectives of the large-scale research infrastructures the run on substitutional technologies started. Most of the solutions could be adapted from developments of particle physics and are comprised of one or more layers of Boron-10. The Time Projection Method achieves highest spatial and time information by high granular track reconstruction, here by the conversion products in a solid Boron-10 layer. Based on the experience of the CASCADE Detector installed at the Spin-Echo instruments RESEDA and MIRA at FRM II in Germany, the University of Bonn now develops two novel systems using the Time Projection Method. The BASTARD detector based on Gas Electron Multiplier foils aims for sub-millimeter resolution at highest count rates and the BODELAIRE detector based on TimePix chips aims for sub-100 micrometer resolution at medium count rates. Both systems increase the efficiency of a single layer of Boron-10 by stacking several consecutive units in beam direction. We present the actual status of the CASCADE project and the actual developments of the novel detector prototypes.
Soil Moisture Measurements with Cosmic-Ray Neutrons , 2019
An effect, which has been considered for more than 50 years as a detector background, turns out t... more An effect, which has been considered for more than 50 years as a detector background, turns out to be one of the promising spin-off technologies to access our most important resource: water. The method, called cosmic-ray neutron sensing (CRNS), is able to uniquely measure at typical correlation scales of soil water of several ten to hundred meters, which other techniques barely reach. This information is most valuable to support climate modeling and hydrology to direct applications in precision farming, draught monitoring and also snow height measurements.
Although it was known that neutrons created in cosmic-ray induced air showers form a gas above the ground, which can be related to the presence of hydrogen, the lack of computational resources prevented a precise description for the relation of neutron intensity to environmental water. Now, in a recent interdisciplinary cooperation of Particle Physics and Earth Sciences the quest to understand the particle propagation in the soil-atmosphere
interface has been solved. With the COSMOS collaboration having meanwhile deployed
more than one hundred sensors, the focus is now set to design and build large-scale neutron detectors in order to improve the measurement precision. This talk provides an overview of the detection technologies, Monte Carlo simulation methods and data challenges of CRNS
as well as it shall exemplarily show how Nuclear and Particle Physics can give birth to a new and unexpected field of applications.
The globally increased demand of Helium-3 along with the limited availability for this gas asks f... more The globally increased demand of Helium-3 along with the limited availability for this gas asks for the development of alternative technologies for the large ESS instrumentation pool.
We report on the CASCADE Project - a novel detection system, which has been developed for the purposes of neutron spin echo spectroscopy. It features 2D spatially resolved detection of thermal neutrons at high rates. The CASCADE detector is comprised of a stack of solid 10B coated Gas Electron Multiplier (GEM) foils, which serve both as a neutron converter and as an amplifier for the primary ionization deposited in the standard Argon-CO2 counting gas environment. This multi-layer setup efficiently increases the detection efficiency to serve as a Helium-3 alternative.
For the application in MIEZE spin echo techniques with interference patterns in the order of millimetres it has furthermore been managed to extract the signal of the charge traversing the stack to identify the very thin conversion layer of about 1µm. This allows to precisely determine the time-of-flight.
The detector concept and measurements results will be presented.
The globally increased demand of Helium-3 along with the limited availability for this gas asks f... more The globally increased demand of Helium-3 along with the limited availability for this gas asks for the development of alternative technologies as the nowadays standard technology is still based on the Helium counter tube.
We report on the CASCADE Project - a novel detection system, which has been developed for the purposes of neutron spin echo spectroscopy. It features 2D spatially resolved detection of thermal neutrons at high rates. The CASCADE detector is comprised of a stack of solid 10B coated Gas Electron Multiplier (GEM) foils, which serve both as a neutron converter and as an amplifier for the primary ionization deposited in the standard Argon-CO2 counting gas environment.
For the application in MIEZE spin echo techniques it has furthermore been managed to extract the signal of the charge traversing the stack to identify the very thin conversion layer of about 1μm. This allows to precisely determine the time-of-flight
The detector concept and measurement results will be presented.
Talk presented at the 12th RD51 Collaboration Meeting, 2014
Bisher werden zum effizienten Nachweis von thermischen Neutronen Detektoren auf Basis von Helium-... more Bisher werden zum effizienten Nachweis von thermischen Neutronen Detektoren auf Basis von Helium-3 eingesetzt, welches sowohl als Neutronenkonverter wie auch als Zählgas dient. Die weltweit gestiegene Nachfrage verlangt, einhergehend mit der limitierten Verfügbarkeit, nach der Entwicklung alternativer Technologien, insbesondere auch in Hinblick auf die ESS.
Der CASCADE-Detektor wurde zum Einsatz in der ortsaufgelösten Neutronen-Spinechospektroskopie entwickelt. Das neuartige Detektionssystem nutzt Bor-10 beschichtete Gas Electron Multiplier (GEM) Folien, mittels deren Neutronenkonversion und nachfolgend Gasverstärkung der entstehenden Primärionisation erfolgt. Die Nachweiseffizienz wird damit durch die Zahl an Folien im Stapel erhöht.
Für die Anwendung in Spinechomessungen (MIEZE) mit thermischen Neutronen wird durch Auslesen des Ladungssignals an einzelnen GEM-Lagen die Konversionsschicht identifiziert und somit präzise die Neutronflugzeit bestimmt. Die kompakte Bauweise erlaubt in Kombination mit der hohen Zeitauflösung das Abbilden der wenige Zentimeter ausgedehnten Spinechogruppe.
Talk Presented at the Deutsche Tagung für Forschung mit Synchrotronstrahlung, Neutronen und Ionenstrahlen an Großgeräten, 2014
The globally increased demand of Helium-3 along with the limited availability for this gas asks f... more The globally increased demand of Helium-3 along with the limited availability for this gas asks for the development of alternative technologies as the nowadays standard technology is still based on the Helium counter tube.
We report on the CASCADE Project - a novel detection system, which has been developed for the purposes of neutron spin echo spectroscopy. It features 2D spatially resolved detection of thermal neutrons at high rates. The CASCADE detector is comprised of a stack of solid 10B coated Gas Electron Multiplier (GEM) foils, which serve both as a neutron converter and as an amplifier for the primary ionization deposited in the standard Argon-CO2 counting gas environment.
For the application in MIEZE spin echo techniques it has furthermore been managed to extract the signal of the charge traversing the stack to identify the very thin conversion layer of about 1μm. This allows to precisely determine the time-of-flight [2].
The detector concept and measurement results will be presented.
[1] M. Klein, C.J. Schmidt, Nucl. Instr. and Meth. A 628 (2011) 9-18
[2] W. Häussler et al., J. Phys.: Conf. Ser. 251 012067 (2010)
Talk Presented at the International Workshop on Position Sensitive Neutron Detectors, 2014
Cold Fusion or N-Rays? Such are mistakes buried deep in the past one might guess - if not lately ... more Cold Fusion or N-Rays? Such are mistakes buried deep in the past one might guess - if not lately the announcement of the discovery of neutrinos travelling faster than light would have been a scientific sensation. Physics, that shall be taught here, is also a history of dead ends. But soon after a in retrospect obvious misconception had spread, it is very likely to be banned from the covers of scientific journals. We want to shed light on such hypotheses, which did not stand the test of time, and ask: What have been the reasons for the wrong interpretation? How had the theses been judged at the time they emerged? What about alternatives? How did the general consensus turn towards the 'new paradigm' and what can we learn nowadays for coming new approaches?
Talk presented at the 79th DPG Annual Conference.
Uploads
Papers by Markus Köhli
consisting of a stack of three Gas Electron Multipliers and eight Timepix
chips. This module was placed in the LP and the setup was tested with the 5 GeV
electron test beam at DESY, Hamburg
advanced detector technologies to be used at a future linear collider. The aim was to make possible
experimentation and analysis of data for institutes, which otherwise could not be realized due to lack
of resources. The infrastructure comprised an analysis and software network, and instrumentation
infrastructures for tracking detectors as well as for calorimetry.
Teaching Documents by Markus Köhli
Thesis Chapters by Markus Köhli
Resultierend aus diesem Umstand schrieb die Agenda zuerst die Konstruktion einer geeigneten Testkammer
vor, um nachfolgend Experimente und deren Auswertung zu ermöglichen. So gliedert sich diese Arbeit in die einzelnen Aspekte von der Konzeption des Experimentes bis zur letztlichen Analyse. Die Ausführung dieser Arbeit beginnt damit, dass in den Grundlagen der physikalische Zusammenhang
zur grundsätzlichen Art der Funktion des Detektors hergestellt und der technologische Rahmen dargelegt wird. Der erste Teil führt die Konzeption des Aufbaus der Kammer aus, welcher sich mit dem Erstellen und Untersuchen eines Simulationsmodelles beschäaftigt. Folgend wird der finite Corpus besprochen, zu welchem gleichermaßen die zugehörige Sensorik, Elektrik und Datennahmegeräte zählen. Nach dem Durchführen des Experimentes setzt die Charakterisierungsarbeit ein Präparieren der erhaltenen Rohdaten voraus. Es existiert aus diesem Grund ein Zwischenabschnitt, welcher sich mit der zu diesem Zweck erstellten Software auseinandersetzt. Letztendliches Ziel war die Untersuchung von TimePix-Chips, welche durch Techniken der Postprozessierung modi ziert wurden. Der TimePix-Chip wurde als hochpixellierter ladungsemp findlicher Detektor
konzipiert und soll zusammen mit der aktuellen Generation mikrostrukturierter Gas-Elektronen-Verstärkern (GEMs) derart kombiniert werden, dass diese eine digitale, hochaufgelöste Auslese für Driftkammern bilden. Die Motivation jeglicher Postprozessierung liegt darin, dass sie eine bessere Adaption
des Grundkörpers des TimePix-Chips an die Granularität und physikalischen Anforderungen der GEM-Struktur scha ffen.
Talks by Markus Köhli
We are now developing boron-lined neutron detectors using spin-off technologies from the upcoming European Spallation Source and instrument design experience from past experiments. These detectors shall also offer an alternative platform to current Helium-3 based systems. In order to reduce costs we recently have developed readout electronics and data acquistion systems based on Arduino microcontrollers.
The nCatcher combines commercially available analog electronics and the Arduino nano enabling pulse shape analysis for proportional counters. The frontend integrates and shapes pulses to microseconds in order to use the Arduino's signal analysis capabilities - time over threshold measurement and a 10-bit analog to digital converter. Combining these two parameters allows for effective discrimination between different radiation types by estimating the total deposited energy (E) of incoming radiation as well as the mean energy loss per distance (dE/dx). This makes the device suitable for low to medium rate environments, where a good signal noise is a crucial.
With the SiPMTrigger we have realized a small scale design for triggering or vetoing. It consists of a custom mixed signal frontend board featuring signal amplification, discrimination and a coincidence unit. An Arduino MEGA digitally adjusts the thresholds of both channels and measures the trigger rate up to 200 kHz.
Although it was known that neutrons created in cosmic-ray induced air showers form a gas above the ground, which can be related to the presence of hydrogen, the lack of computational resources prevented a precise description for the relation of neutron intensity to environmental water. Now, in a recent interdisciplinary cooperation of Particle Physics and Earth Sciences the quest to understand the particle propagation in the soil-atmosphere
interface has been solved. With the COSMOS collaboration having meanwhile deployed
more than one hundred sensors, the focus is now set to design and build large-scale neutron detectors in order to improve the measurement precision. This talk provides an overview of the detection technologies, Monte Carlo simulation methods and data challenges of CRNS
as well as it shall exemplarily show how Nuclear and Particle Physics can give birth to a new and unexpected field of applications.
We report on the CASCADE Project - a novel detection system, which has been developed for the purposes of neutron spin echo spectroscopy. It features 2D spatially resolved detection of thermal neutrons at high rates. The CASCADE detector is comprised of a stack of solid 10B coated Gas Electron Multiplier (GEM) foils, which serve both as a neutron converter and as an amplifier for the primary ionization deposited in the standard Argon-CO2 counting gas environment. This multi-layer setup efficiently increases the detection efficiency to serve as a Helium-3 alternative.
For the application in MIEZE spin echo techniques with interference patterns in the order of millimetres it has furthermore been managed to extract the signal of the charge traversing the stack to identify the very thin conversion layer of about 1µm. This allows to precisely determine the time-of-flight.
The detector concept and measurements results will be presented.
We report on the CASCADE Project - a novel detection system, which has been developed for the purposes of neutron spin echo spectroscopy. It features 2D spatially resolved detection of thermal neutrons at high rates. The CASCADE detector is comprised of a stack of solid 10B coated Gas Electron Multiplier (GEM) foils, which serve both as a neutron converter and as an amplifier for the primary ionization deposited in the standard Argon-CO2 counting gas environment.
For the application in MIEZE spin echo techniques it has furthermore been managed to extract the signal of the charge traversing the stack to identify the very thin conversion layer of about 1μm. This allows to precisely determine the time-of-flight
The detector concept and measurement results will be presented.
Talk presented at the 12th RD51 Collaboration Meeting, 2014
Der CASCADE-Detektor wurde zum Einsatz in der ortsaufgelösten Neutronen-Spinechospektroskopie entwickelt. Das neuartige Detektionssystem nutzt Bor-10 beschichtete Gas Electron Multiplier (GEM) Folien, mittels deren Neutronenkonversion und nachfolgend Gasverstärkung der entstehenden Primärionisation erfolgt. Die Nachweiseffizienz wird damit durch die Zahl an Folien im Stapel erhöht.
Für die Anwendung in Spinechomessungen (MIEZE) mit thermischen Neutronen wird durch Auslesen des Ladungssignals an einzelnen GEM-Lagen die Konversionsschicht identifiziert und somit präzise die Neutronflugzeit bestimmt. Die kompakte Bauweise erlaubt in Kombination mit der hohen Zeitauflösung das Abbilden der wenige Zentimeter ausgedehnten Spinechogruppe.
Talk Presented at the Deutsche Tagung für Forschung mit Synchrotronstrahlung, Neutronen und Ionenstrahlen an Großgeräten, 2014
We report on the CASCADE Project - a novel detection system, which has been developed for the purposes of neutron spin echo spectroscopy. It features 2D spatially resolved detection of thermal neutrons at high rates. The CASCADE detector is comprised of a stack of solid 10B coated Gas Electron Multiplier (GEM) foils, which serve both as a neutron converter and as an amplifier for the primary ionization deposited in the standard Argon-CO2 counting gas environment.
For the application in MIEZE spin echo techniques it has furthermore been managed to extract the signal of the charge traversing the stack to identify the very thin conversion layer of about 1μm. This allows to precisely determine the time-of-flight [2].
The detector concept and measurement results will be presented.
[1] M. Klein, C.J. Schmidt, Nucl. Instr. and Meth. A 628 (2011) 9-18
[2] W. Häussler et al., J. Phys.: Conf. Ser. 251 012067 (2010)
Talk Presented at the International Workshop on Position Sensitive Neutron Detectors, 2014
Talk presented at the 79th DPG Annual Conference.