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abstract: We experimentally demonstrate efficient broadband self powered photo detection and power generation in thin films of polycrystalline bismuth telluride (Bi2Te3) semiconductors under inhomogeneous strain. The developed simple, junction free, lightweight, and flexible photo detectors are composed of a thin active layer and Ohmic contacts on a flexible plastic substrate, and can operate at room temperature and without application of an external bias voltage. We attribute the observed phenomena to the generation of an electric field due to a spontaneous polarization produced by strain gradient, which can separate both photo generated and thermally generated charge carriers in bulk of the semiconductor material, without a semiconductor junction. We show that the developed photo detectors can generate electric power during both the daytime and the nighttime, by either harnessing solar and thermal radiation or by emitting thermal radiation into the cold sky. To the best of our knowledge, this is the first demonstration of the power generation in a simple junction free device under negative illumination, which exhibits higher voltage than the previously used expensive commercial HgCdTe photo diode. Significant improvements in the photo detector performance are expected if the low charge mobility polycrystalline active layer is replaced with high quality single crystal material. The technology is not limited to Bi2Te3 as the active material, and offers many potential applications in night vision, wearable sensors, long range LIDAR, and daytime/nighttime energy generation technologies.
author_names: Bruno Lorenzi

Yoichiro Tsurimaki

Akihiro Kobayashi

Masayuki Takashiri

Svetlana V Boriskina
title: Self powered broadband photo detection and persistent energy generation with junction free strained Bi2Te3 thin films.
venue: Optics express
year: 2020

abstract: The interactions between electromagnetic field and the biological system can lead to the change of biological morphology, structure, function and other aspects at the different levels of biological targets. The domestic sewage is secondarily disinfected using continuous electromagnetic waves, the microscopic molecules have a certain dipole moment and the biological molecular aggregates with dielectric properties of the cell may generate dielectric loss under the effect of the applied electromagnetic field. The thermal effect will be produced by putting the microwave energy into the heat of irregular movement which increases biological system's temperature. Under the influence of an applied electromagnetic field, the membrane potentially undergoes conformational changes that would affect K ion, Na ion channels open and make the voltage dependant Ca ion open, the high concentration of Ca ion of the membrane into the cell along the potential gradient, which leads to cell death, resulting in the biological non thermal effects, the greater the changes of cellular transmembrane voltage, the higher the rate of cell death. The experiment results show that the microwave secondary sterilization has a good sterilizing effect, the method has the advantages of high efficiency, low cost, simple operation, easy automation, without adding any substance and does not produce any secondary pollution, etc.
title: THE EFFECT AND MECHANISM OF URBAN DOMESTIC SEWAGE SECONDARY STERILIZATION BY MICROWAVE
year: 2019

abstract: Non thermal plasma assisted partial oxidation of hydrocarbon fuels (including military logistic fuels) is considered with the intent to rapidly produce hydrogen rich syngas with the least amount of electrical power. The syngas produced can be used to fuel quiet solid oxide fuel cell (SOFC) auxiliary generators, be added to engines or combustors to extend lean operation (decrease NOx and increase efficiency) or be further reformed to increase hydrogen yield (via water gas shift and gas cleanup) for low temperature fuel cells. Unlike catalytic fuel reformers that suffer from adverse issues involving catalyst deactivation (coking and tolerance to sulfur) and require a warmup period dependent on the thermal mass of the catalyst, plasma reforming offers a noncatalytic approach for rapid "on demand" hydrogen rich syngas production (quick startup) Plasma fuel reforming is also fuel flexible and can be applied to applications needing dynamic control of a varying amount of syngas such as those having a time dependent load (e.g. engine acceleration/ deceleration) It can also be used to rapidly produced hydrogen for fuel cell powered robots used in place of batteries. In this study, experimental results using a non thermal 'warm' plasma reformer are presented with a focus on the hydrogen and carbon monoxide yields, their selectivities, the efficiency of the reformer and the specific energy density (SED) a measure of the amount of electricity needed to produce a kilogram of hydrogen or syngas. In terms of fuel feedstocks, much of our work to date has focused on plasma reforming of natural gas with recent efforts to extend the work to JP fuels. INTRODUCTION Fuel cells and other applications require hydrogen. In commercial systems, hydrogen is traditionally produced in large scale steam reforming plants and transported to the point of use, which is not practical for most military operations. Instead, fuel reformers are needed to convert jet fuel (a complex blend of heavy hydrocarbons with sulfur impurities) to hydrogen or hydrogen rich syngas at the point of use. A practical approach is to partially oxidize the available fuel to hydrogen rich syngas, which is a mixture of hydrogen and carbon monoxide. For SOFC's, the entire reformate containing mostly hydrogen, carbon dioxide, and small hydrocarbons can potentially be used provided the sulfur levels and aromatic content are sufficiently low. For low temperature protonexchange membrane (PEM) fuel cells, the water Proceedings of the 2018 Ground Vehicle Systems Engineering and Technology Symposium (GVSETS) Rapid Production of Hydrogen Rich Syngas, Pearlman et al. Page 2 of 9 gas shift reaction can be used to convert the carbon monoxide in the reformate to additional hydrogen with the use of steam followed by gas cleanup; the steam can also potentially be recovered from the output of the fuel cell. For partial oxidation, catalytic, thermal, and plasma based approaches exist. Catalytic reforming has been shown to work at least for a limited time [1] yet is sensitive to the high aromatic content and sulfur in the fuel. Also, the catalyst must be initially heated which can slow the startup time depending on its thermal mass. Thermal partial oxidation (TPOX) is also an option, conveniently avoids the need for catalysts, yet does require high reaction temperatures ~1200oC or higher) to achieve high hydrogen concentrations; the high temperatures limit the choice of materials to high temperature metals, metal alloys or ceramics; TPOX reformers also require a startup period dependent on the thermal mass of the reformer. In this work, our focus is on non thermal plasmaassisted partial oxidation. No catalysts are needed and the reformer can rapidly produce hydrogen from a cold start. It is also fuel flexible and sulfur tolerant. It does, however, require electricity to generate a high voltage, low current electric discharge (arc) with which the reactants interact, producing radicals and charged species that promote reforming reactions. Stainless steel electrodes are used in our reformer and can handle typical operating temperatures of 800 1000oC. Also, in our system, the arc discharge continuously translates between two opposed electrodes; this avoids the formation of local hot spots on the electrodes that are undesirable. In effect, by continuously translating the arc discharge, a 'volumetric' discharge is generated that then is used to reform a continuous reactant flow. A key focus of our current work (now funded through the Department of Energy) is also on developing effective ways to lower the electricity needed for plasma assisted fuel reforming; this is important since the cost of electricity is the primary operating cost [4] To do so, our approach has been to efficiently preheat the reactants using heat from the hot reformate exiting the reformer; this raises the temperature of the reactants, which increases the reaction rates resulting in higher syngas yields for the same electrical power. Prior work showing the benefit of preheating is available in references 6 and 7. THERMAL VS. NON THERMAL PLASMA FUEL REFORMING There are two fundamental types of plasmas, thermal and non thermal, both of which have application for fuel reforming. Both plasmas consist of electrons, ionized species and neutral species that promote fuel reforming. For conditions where the all constituents are very energetic (high electron, ion and gas temperatures) the plasma is referred to as a thermal plasma. High electrical power is, however, needed to generate thermal plasmas and is used for bulk heating of the entire gas mixture. With that said, however, thermal plasma fuel reformers are very efficient at producing hydrogen rich syngas from a variety of different hydrocarbon fuels (natural gas, gasoline, diesel, oil, biomass, and jet fuel) have a fast response time, and can be compact (owed to their high power density) [9] In comparison, non thermal plasmas require less electrical power as they do not provide for bulk heating of the gas. Rather, the gas temperatures are comparatively low (neutral and ionized species temperatures are ~300 1,500K) while the electron temperatures are very high (10,000 100,000K) With lower gas temperatures, the need for expensive, high temperature materials is avoided and electrode stability/lifetime is extended. In essence, in non thermal plasmas, high grade electricity is used to create a strong nonequilibrium between the electron temperature and Proceedings of the 2018 Ground Vehicle Systems Engineering and Technology Symposium (GVSETS) Rapid Production of Hydrogen Rich Syngas, Pearlman et al. Page 3 of 9 the temperature of the gas molecules and ions; the electrons subsequently participate in dissociation and ionization reactions that promote syngas production without substantial heating of the gas mixture. In our system, heating of the gas mixture is largely provided from the exothermicity of the partial oxidation process together with heat recuperation from the hot reformate with a limited amount of heating provided from the electrical discharge. Non thermal plasmas can further be divided into two classes: "cold" and "warm." Both classes generate a pool of active species that serve a similar role as a catalyst. Cold plasmas, including dielectric barrier discharges (DBD) coronas, and pulsed coronas, do not provide heating of the gas, and are usually used in applications requiring low process temperature and low power density, such as surface treatment, ozone production, and disinfection [12] "Warm" discharges are intermediate between cold and thermal plasmas and include low current arcs, glow discharges [13] microwave discharges [10,11] and gliding arc discharges [5] Gliding arc discharges are especially well suited for fuel reforming since their temperatures are in the 800 1000oC range, which is similar to that needed for traditional reforming. In terms of prior studies on plasma reforming, notable contributions include work by the Drexel Plasma Institute who used a gliding arc plasma reactor for steam or dry reforming of JP8 with H2O and CO2; here, the H2O and CO2 represent the products of an SOFC exhaust stream [2] Also, Ceramatec has developed a plasma reformer for reforming diesel
author_names: Howard G Pearlman

Brian F Schwartz

Max Demydovych

Chien-Hua Chen

Alexander Rabinovich

Shridhar Shenoy

Alexander A Fridman
title: Rapid Production of Hydrogen Rich Syngas Using a Non Thermal Plasma Fuel Reformer
year: 2018

abstract: Thermo catalytic thermal cracking processes refer to processes of the chemical industry whose input raw material are solid, liquid or gas state hydrocarbons. The purpose of technology is to produce a liquid and gas state hydrocarbon fraction with higher value. As a starting point in our research, we examined thermal cracking of solid and/or rubber waste by means of a fixed and fluid bed (semi batch) complex reactor system using a catalyst at 450 degC. Common features of these operations of the chemical industry are the inertised atmosphere, temperatures between 400 and 450 degC and a pressure range close to the atmosphere. However, the selected reactor design may imply a considerable difference as it largely determines the distribution and quality parameters of the valuable products formed. Our publication discusses the optimisation possibilities of reactor constructions of diverse types based on the values measured with the equipment constructed by us and experiences. 1. PRESENTATION OF THERMAL CRACKING PROCESSES Recycling various plastic and rubber waste sorts thermo catalytically has been drawing more and more attention in the last years as valuable raw materials for the chemical industry and energy carriers can be generated this way. Moreover, it is worth noting that considerable environmental and waste treatment issues can become resolvable, too. One of the most important operational units of the process is the reactor, in which the degradation, more precisely the chemical conversion of the solid raw material occurs with the impact of a catalyst and inert fluid mixer. However, it is a relevant fact that solid raw material processing thermal cracking technologies face a number of important challenges. The design and operation of catalytic cracking reactors is difficult due to the poor thermal conductivity factor and extremely high viscosity of molten polymer. Types used in a broad range applications are the following: batch/semi batch reactors; fixed bed reactors; fluid bed reactors; MultiScience XXXI. microCAD International Multidisciplinary Scientific Conference University of Miskolc, Hungary, 20 21 April 2017 ISBN 978 963 358 132 2 DOI: 10.26649/musci.2017.066 streamed bed reactors; screw press (extruder) reactors. Our work leveraged a combined design laboratory scale (capacity: 40 g/h) semibatch operated fluid and fixed bed reactor system by means of which experimental measurements were performed under thermal and thermo catalytic circumstances at 450 degC. 2. ANALYSIS OF REACTOR TYPES OF THE THERMAL AND THERMOCATALYTIC THERMAL CRACKING PROCESSES The selection of reactor type(s) appropriate for the solid raw material to be processed is key in the process as it affects directly both the quality and quantity of the product formed. 2.1. Batch/semi batch reactors Many studies on thermo catalytic plastics cracking in mixed (not in each case) batch or semi batch reactor are available in the professional literature [1] The main reason for this is principally the easy designability and operability. In the case of semi batch reactors, a stream of continuous inert gas (nitrogen in general) is generated, which removes the volatile components from the vapour space at the temperature of reaction. The removal of volatile products minimises the possibility of the secondary cracking (e.g. via oligomerisation, cyclisation and aromatization) of primary cracking products. This process 'takes a back seat' in a batch reactor as there the secondary cracking is 'brought to the fore' [2] Lee et al. examined the catalytic degradation of plastic waste (HDPE high density polyethylene) LDPE (low density polyethylene) PP (polypropylene) and PS (polystyrene) on FCC (fluid catalytic cracking) catalyst in a semi batch mixed reactor [3] The yield of liquid products depending on the plastics of various types at 400 degC was as follows: PS PP PE (HDPE, LDPE) The quantity of liquid products was over 60 in each case. In the catalytic case, the solid remains were below 1 m/m% except for PS, where it was about 5 m/m% To avoid the mentioned secondary cracking, we decided to operate the verticallypositioned fluid bed tube reactor in our work in a semi batch manner with the continuous stream in of nitrogen. 2.2. Fixed bed reactors Fixed bed reactors are probably listed among the most classic reactors. However, there use with plastics is not easy as these materials have an elevated viscosity and low thermal conductivity factor, due to which extremely serious issues can arise even at the feed in. In specific cases, the molten polymer fraction is introduced to the reactor [4] via a capillary tube from the tank under overpressure. The most frequent technical solution is to perform a so called preventive thermal cracking. Next, the liquid or gas components originating from the thermal cracking can be simply transferred onto the fixed bed [5, 6] in a simple fashion. In our experiments, the role of the fixed bed outlined above was played by the horizontal tube reactor operated at 300 degC as the product vapours formed coming from the vertically positioned operational unit were transferred directly in here, which can actually be regarded as a preventive thermo catalytic cracking as well. 2.3. Fluid bed reactors Fluid bed reactors are characterised by homogeneity in terms of temperature and product composition. This is a remarkable advantage in the cracking of polymers as a thermal gradient develops due to the generally low thermal conductivity factor and high viscosity, leading to developing other reaction systems as heat does not transfer uniformly everywhere. One of the most known processes for the pyrolysis of plastic waste is the Hamburg process developed by Kaminsky et al. [7] The reactor was heated with a heating filament with a power of 5 kW. The raw material was in fed by two screw conveyor belts. The products produced in this way underwent a thorough separation, composed of a cyclone, coolers and electrostatic separators, too. Initially this system was used for thermal cracking of waste polymers exclusively, thereby using nitrogen or pre heated vapour as fluidising agent [7] At a conversion of 90 m/m% oil and waxy products formed, whereas oil had 40% BTX (benzene, toluene, xylene) at higher temperatures (690 to 735 degC) [7] In our work, we noticed that the conversion was almost 90% already at 450 degC with the reactor combination selected by us as we mixed 10 w% catalyst into the raw material and the NiO coated metal mesh, which was also responsible for the establishment of the homogeneous temperature field. The oil produced in our case contained 40% BTX fraction, too (Table 1) because the product vapours could be in direct contact with the catalyst attachment in the horizontal tube reactor. 2.4. Streamed bed reactors One of the first proposals to recycle plastic waste was to crack them directly together with standard FCC raw materials in a combined material flow in FCC refining units. In this line of thinking, a new reaction system is established in a streamed bed. The in feeding contains normally mixed plastic (PE, PP, PS) at 5 10 m/m% light oil (LCO) vacuum gas oil (VGO) or benzene [8] The key element of the process is the internal recirculation reactor, which can ensure little contact time (1 to 10 s) and can operate at a ratio of C/O 6 (catalyst/oil ratio) The catalyst is placed in a basket and gases circulate through the basket via a streaming enforced by a turbine. At time 0, in feeding takes place by injection, when the reaction is finished, the valve opens and the products flow into a vacuum chamber [8] Cracking PE/LCO and PP/LCO mixtures on a HZSM 5 catalyst resulted in the formation of mainly C5 C12 hydrocarbon and aromatic type product as well as small quantity of C1 C2 gas and chark at 450 degC in the ascending simulator [8] 2.5. Screw press (extruder) reactors Screw press (extruder) reactors provide assistance for thermo catalytic cracking of plastic and plastic oil mixture by opening up a novel reaction system [9 11] What is interesting about the process is that the design of the reactor reminds of extruders, which are also used for a broad range of polymer processing applications. The equipment is shown in Figure 1 in a schematic form. Figure 1 Schematic of a screw press reactor [10] The reactor has one hopper where the plastics and plastic oil mixtures can be infed. The externally heated furnace operates at 250 to 300 degC in a nitrogen atmosphere (at a pressure somewhat higher than the atmospheric one) [9 11] The molten reaction mixture is then forwarded into the reactor body, which means essentially a stainless steel tube meaning the current reaction zone at the same time. The tube is heated externally by two tube furnaces, whose temperatures can be regulated irrespective of each other, thus, the reactor can be split up into two heating sections (marking T1/T2) The temperature can be continually regulated with a series of integrated thermoelements to avoid the probability of formation of cold/colder points that would lead to the hardening of plastic. The revolution of the screw press can be varied between 0.5 and 25 rpm, as a result of which the residence time of melt can be defined, too. Due to the small screw diameter, the radial temperature profile is technically negligible. The catalyst is mixed with the plastic in the hopper as this ensures the homogeneous reaction mixture and consequently the identical stream image in the entire system. The catalyst can be recovered at the output point with a simple filtering [9 11] Unlike in other reaction systems, no viscosity issue arises in this reactor as the extrudes squeezes out the material, therefore, the plastic phase can be fed in the hopper continually without any flow issue. This is a significant benefit in contrast to conventional fixed bed reactors where plastic moves simply gravitationally or the feed in is provided from a previous thermal cr
author_names: Andor Zsemberi

Zoltan Simenfalvi

Arpad Bence Palotas
title: Presentation of Reactor Types for Thermo Catalytic Thermal Cracking
year: 2017

abstract: Introduction Waveforms are an important issue in magnetic stimulation. They provide the key to an important characteristic of neurons: their distinctive nonlinear dynamics. Different waveforms seem to have different activation sites and may allow selective stimulation. This is reflected for example by their different corticospinal D and I wave patterns Di Lazzaro, 2004 However, available pulse types are very restricted. In essence, the only established waveforms are monophasic and biphasic pulses. In addition to selective stimulation and neuromodulation, higher efficiency Goetz, 2012 could enable highly focal small coils to overcome thermal issues and provide high repetition rates. Objectives Current devices can only provide very distinct pulses for technological reasons. Even in alternative, more flexible approaches, the underlying circuitry is limited to a certain class of stimuli. Among these stimuli, only a subclass does not change the device state of charge and can therefore be generated repetitively. Our objective was to conceive and design a technology that is able to generate almost any waveform. Accordingly, the selection of waveforms would no longer depend on device capabilities and technology, but merely follow the user's needs. Methods For this aim, we had to abandon all traditional concepts and designs for pulse generation in magnetic stimulation as well as other fields of science and engineering. We developed novel topologies that can handle the special requirements of magnetic stimulation pulses, namely high voltage, high current and high speed. The winning approach uses a dynamical reconfiguration of small energy storages: Metaphorically speaking, it uses a high number of small voltage batteries that can be combined in any parallel and series connection dynamically changeable for every time step so as to exactly control the coil voltage accurately to the curve outlined by the desired waveform. The key components of the technology are no longer expensive high voltage semiconductors, but inexpensive mass produced devices used in consumer electronics. We designed a control strategy for the distributed concept and implemented a prototype for characterization of the concept. Results The system can generate almost any waveform, both existing and potential future pulse shapes. All waveforms can be generated with a recovery of the pulse energy from the coil, which has been known from biphasic stimulators. We achieved this even for classical monophasic waveforms, which can except for rare research devices Schmid et al. 1993 provide high pulse repetition rates, although being preferred. The high losses prevent that. Furthermore, the generation of waveforms is not done by any mechanical reconfiguration, but controlled dynamically. Therefore, the system can even fundamentally change the waveform from pulse to pulse in a theta burst or double pulse protocol. Conclusion The generation of arbitrary waveforms is possible and has several advantages also for classical waveforms. Among others, this includes the ability to use high repetition rates for almost every waveform and profit from cost effective mass produced components.
author_names: Stefan Gotz

Florian Helling

Thomas Weyh
title: P 232. Leaving the beaten track of TMS waveform restrictions: Concepts and prototype for a 'convertible' stimulator that can generate almost every type of existing and future waveform
venue: Clinical Neurophysiology
year: 2013

abstract: As the demand for energy continues to grow with population in emerging countries, use of alternative renewable sources of energy is imperative for the near future. The impending climate change and current economic development have forced a shift to more sustainable sources of energy like geothermal, solar, and wind. The widening of supply demand gap over years has led to global energy crisis and resulted in exhaustive use of non renewable natural resources to meet the energy demands. This extensive use of fossil fuels has been made possible by the current development of human civilization. However, burning of fossil fuels, which are becoming increasingly scarce, has led to an increase in emissions of carbon dioxide, which is a greenhouse gas, into the atmosphere. This, in turn, has also led to a detrimental impact on the environment and an imbalance in the natural ecosystem. Geothermal energy is a green, environmentfriendly, low carbon, renewable and sustainable source of energy since there are relatively less investments and is pollutant free. The major advantage of geothermal energy over other sources of renewable energy is that the underground heat/energy mining does not depend on the weather conditions and geothermal power runs at a much higher load factor than wind or solar. Nearly 40% of the total investment cost that goes into setting up a geothermal plant is the drilling cost. However, this problem can be potentially tackled by utilizing the currently decommissioned and abandoned oil and gas wells for geothermal purposes. Retrofitting an abandoned well to produce geothermal energy also saves the cost of exploring sites for geothermal fields. The estimated potential for the geothermal energy that can be harnessed in India is about 10 million kW. In this study, abandoned oil and gas wells have been simulated as a source of geothermal power to generate electricity. Simulations have been performed by coupling thermal reservoir with bore well heat transfer and laminar flow model. Water, which is chosen as working fluid is circulated down through the annulus and extracted back through the shorter insulated inner pipe. A parametric study to assess the production temperature using finite element method with various operating parameters such as injection mass flow rate, re injection temperature, well depth and geothermal gradient is performed. The results of this study indicate that heat extraction rate increases with increasing mass flow rate as well as the well depth while all other injection parameters remain constant. At higher injection temperature, the net heat extraction rate from the reservoir decreases with time due to lower temperature difference between injected fluid and reservoir formation temperature.
author_names: A Shah

S N Pandey

Vikram Vishal

Sandip Kumar Saha
title: Modeling of heat transfer in abandoned oil and gas wells
year: 2019

abstract: This thesis describes the work undertaken over three years into the investigation of the effect of proton irradiation on the fatigue crack behaviour of an austenitic stainless steel. Many in core nuclear reactor components that are subjected to radiation damage and repeated thermal stresses are made from austenitic stainless steels. A thorough understanding of the effect of the material changes caused by the radiation damage on the fatigue cracking behaviour is essential for safely extending the lifetime of nuclear plant components. Proton irradiation from an ion accelerator has been used in this study as a surrogate for the neutron irradiation experienced by real components. Despite the different interactions of protons and neutrons with matter, under certain conditions, proton damage can result in a similar damaged end state to neutrons. In contrast to reactor neutrons, accelerated protons can be produced at a higher rate, allowing component end of life damage levels to be reached in a much shorter time. A review of the literature identified thermoelastic stress analysis (TSA) as the technique most capable of measuring the required variables during a fatigue crack growth test, i.e. stress intensity factor and plastic zone size. Two key gaps in the literature were identified. Firstly, few studies of fatigue crack growth in irradiation damaged specimens exist and those that do typically report a small number of specimens. Due to the inherent variability of fatigue crack growth, a large number of specimens should be tested at each damage level to obtain statistically meaningful data. Secondly, fatigue crack growth studies rely on analytical relations based on crack length for both stress intensity factor and plastic zone size measurements in many cases. Using TSA allows direct measurement of these quantities and hence a deeper understanding of the actual specimen behaviour. A novel method was developed to measure the extent of the cyclic plastic zone based on the in phase second harmonic temperature signal. This allowed measurement of the plastic zone area, without prior knowledge of the yield strength. Further, the total energy dissipated from the plastic zone could be calculated, without assuming the plastic zone size and shape. Investigations of the second harmonic temperature data revealed signals originating in the crack flanks that were demonstrated to be related to crack closure. This allowed a simple binary check for closure without further data analysis. A number of austenitic compact tension specimens were prepared and irradiated using accelerated protons at a set of increasing proton fluence levels. Following irradiation, the specimens were loaded in fatigue and imaged regularly with a TSA system as the crack grew. This gave simultaneous measurements of plastic zone size and effective stress intensity factor, and represented the first time the TSA technique has been used to investigate radiation damaged material. The experimentally obtained stress intensity factors and crack growth rates were fitted using the Paris' Law model and analysis of covariance suggested that there is not a statistically significant difference in the gradient of the fit with increasing irradiation damage. However, a significant effect (p 0.05) was found in the offset value. This suggests that greater radiation damage causes a greater reduction in crack growth rate, in agreement with literature. Measurements of the TSA output suggest that, contrary to theory, the apparent plastic zone increased in size with more radiation damage. However, the dissipated energy from the plastic zone did tend to increase with radiation damage. Hence, it is hypothesised that the physical plastic zone decreases in size due to the greater hardness induced by the irradiation, but emits a larger amount of energy as the vacancies and interstitials generated by the radiation damage make dislocation movement more energetically difficult, resulting in an apparent increase in plastic zone size when measured using the TSA system.
author_names: Rory P Spencer
title: Fatigue crack growth behaviour in proton irradiated austenitic stainless steel
year: 2019

abstract: Feldspar in ordinary chondrites (OCs) is often associated with thermal metamorphism, as a secondary mineral that forms from the crystallization of matrix and chondrule mesostasis. However, studies of feldspar in equilibrated OCs show that there is a range of plagioclase compositions within chondrules, some of which may be primary products of chondrule crystallization. It is important to recognize primary feldspar within chondrules because it can be used to help understand the secondary effects of thermal metamorphism and aqueous alteration. The presence of primary feldspar also provides important petrologic constraints on chondrule formation timescales. We undertook a careful study of Semarkona (LL3.00) and observed feldspar in 18% of chondrules. The feldspar is plagioclase covering a wide range of compositions (An2 An99) with little K feldspar component <Or3) We show that plagioclase is a primary igneous phase, based on grain morphology and compositions consistent with growth from a melt having the bulk compositions of the host chondrules. Based on experimental studies, the presence of plagioclase suggests chondrules cooled slowly at temperatures close to the solidus. We also observed several secondary features consistent with the aqueous alteration. These features include zoning of Na and Ca in plagioclase, heterogeneity in plagioclase compositions in altered chondrules, development of porosity from the dissolution of chondrule glass, and alteration of glass to phyllosilicates. Alteration of major Al bearing phases, like plagioclase and glass, has important implications for interpretations of ages derived from Al Mg dating of chondrules, if they have been affected by secondary processes. Introduction Feldspar in ordinary chondrites (OCs) is commonly considered to be a secondary phase that forms during thermal metamorphism. As chondrule mesostasis glass, often feldspathic in composition, and chondrite matrix recrystallize, plagioclase and other phases develop in what has historically been treated as a solid state, temperature dependent process (Huss et al. 2006) The classification scheme of Van Schmus and Wood (1967) used to differentiate degrees of thermal metamorphism, describes the crystallization of chondrule mesostasis into albite as an important feature of the effect of thermal metamorphism. According to this classification scheme, fine grained albite crystallizes by petrologic type 4 and then undergoes textural equilibration through types 5 and 6, ultimately resulting in grains of albite >50 mm in size (Huss et al. 2006; Van Schmus and Wood 1967) However, recent studies of feldspar in equilibrated OCs (Kovach and Jones 2010; Lewis and Jones 2016) show that the general model of Van Schmus and Wood (1967) does not fully define the feldspar equilibration process or the range in compositions and textures found in OC feldspar. Plagioclase is not solely albitic in composition and a wide range of plagioclase compositions (An2 An88) is present in relict chondrules in type 4 L and LL chondrites (Kovach and Jones 2010; Lewis and Jones 2016) Only in type 6 chondrites is feldspar equilibrated chemically, as well as texturally, to an albitic composition of ~An11. The wide range of feldspar compositions within chondrules in type 4 L and LL chondrites is plausibly derived from variable initial mesostasis compositions. However, chondrules may also contain primary igneous plagioclase, with a range of compositions that could reflect the compositions of plagioclase observed in type 4 OCs. Primary, igneous anorthitic feldspar has been described in Type I chondrules in OCs (Huss et al. 2001; Russell et al. 2000) but it is not well characterized, unlike similar occurrences in carbonaceous chondrites (CCs) (Brearley and Jones 1998; Wick and Jones 2012) Al rich chondrules in OCs also contain primary anorthite that is useful for age dating using Al Mg systematics (e.g. Huss et al. 2001) Although Type II chondrules in OCs are relatively rich in Na and K, albitic plagioclase or alkali feldspar is not generally observed (Jones 1990) Grossman and Brearley (2005) noted that crystalline albite is present within some Semarkona chondrules, but did not indicate whether it is primary or secondary in origin. To understand how secondary plagioclase develops during metamorphism, it is essential to know the abundance and composition of primary plagioclase. The mineralogical and chemical changes that affect chondrule mesostasis during thermal metamorphism depend on the composition and initial crystallinity of the mesostasis, in addition to temperature and available fluids. The presence of primary feldspar can influence the subsequent crystallization of the mesostasis glass by providing surfaces on which secondary plagioclase can nucleate. Plagioclase is also affected by alkali metasomatism, so secondary effects recorded in primary plagioclase can provide an indicator of the presence of fluids in type 3 chondrites. Plagioclase alteration can affect Al Mg systematics resulting in low precision isochrons or ages that are difficult to interpret. In addition to its importance in terms of interpreting metamorphism, understanding the origin and development of primary feldspar can help constrain chondrule cooling rates, an important parameter in chondrule formation models (Connolly and Jones 2016) We have investigated the presence and characteristics of primary igneous plagioclase within chondrules of the LL3.00 chondrite Semarkona. Semarkona is the least thermally metamorphosed OC fall with a maximum metamorphic temperature estimated to be less than 260degC (Alexander et al. 1989) It is the ideal sample in which to investigate primary chondrule minerals because chondrule mesostasis glass has not undergone crystallization (Huss et al. 2006) The mineralogy and petrology of Semarkona chondrules were studied extensively by Jones and Scott (1989) and Jones (1990, 1994, 1996) but primary igneous plagioclase was not recognized in those studies. Marked improvements in SEM technology has enabled higher resolution investigations into chondrule mineralogy and allowed for studies on phases too small to be fully characterized in earlier studies. We show that primary igneous plagioclase is abundant in Semarkona chondrules and that careful observations of plagioclase are important for interpreting the effects of metamorphism, alteration, and the results of Al Mg isotope systematics. Samples Analytical Methods For this study, we examined a single thin section of Semarkona from the Institute of Meteoritics Collection at the University of New Mexico, UNM 549. Feldspar was identified using backscattered electron (BSE) imaging and energy dispersive spectroscopic (EDS) analysis on an FEI Quanta 3D Field Emission Gun Scanning Electron Microscope (FEG SEM) at the University of New Mexico. High contrast BSE images were captured at 10 kV and 16 nA. Cathodoluminescence (CL) images were acquired at the Williamson Research Centre, University of Manchester using a CITL Cold Cathode CL 8200 MK3 with optical stage operated at 15 20 kV and 300 400 mA. Quantitative wavelength dispersive spectroscopic (WDS) analysis was performed on a JEOL 8200 Electron Probe Microanalyzer (EPMA) at the University of New Mexico operated at 10 15 kV and 10 nA with a focused beam. The low accelerating voltage was used to minimize the interaction volume when analyzing small feldspar grains. We used the following standards: Taylor olivine (Mg, Fe) Taylor albite (Na, K) Taylor orthoclase (K, Al, Si) and a doped diopside (Ca, Cr, Mn) We used time dependent intensity corrections on Na using the Probe for EPMA software to compensate for the effects of Na migration in Na bearing plagioclase during focused beam analysis. We determined bulk silicate compositions for four chondrules, based on quantitative WDS maps obtained using the EPMA. 300x300 pixel maps were acquired in two passes using an 80 ms/px dwell time and a 1 3 mm spot size. This provided coverage of between 300x300 mm and 900x900 mm, depending on the size of the chondrule. The resulting intensity maps were processed using mean atomic number (MAN) background corrections to produce quantitative oxide maps. MAN curves were generated using the following Taylor standards: olivine, albite, orthoclase, chromite, spessartine, MgO, hematite, and nickel and additional standards: doped diopside, labradorite, and sodalite. Chondrules were masked in Adobe Photoshop and the bulk silicate compositions of the chondrules were calculated. We used a custom MATLAB script to identify the chondrule pixels in which analytical sums lie between 90% and 110% In addition, pixels with SiO2 content less than 20% were omitted to eliminate Fe Ni metal and sulfides. Densities were determined for each pixel based on the assigned mineral phase and the bulk silicate composition of each chondrule was calculated as the mean density weighted composition of accepted
author_names: Jonathan A Lewis

Rhian H Jones
title: Primary feldspar in the Semarkona LL3.00 chondrite: Constraints on chondrule formation and secondary alteration
year: 2019

abstract: Very thin, thermally evaporated MoOx (x 3) layer has been used as transparent hole selective contact on an ntype Germanium substrate to effectively demonstrate PV conversion capability. The fabricated MoOx/Ge heterojunction PV cell shows a photocurrent density of 44.8 mA/cm under AM1.5G illumination, which is comparable to that of conventional Ge PV cells. However, a low open circuit voltage of 138mV is obtained, which might be explained by the presence of tunnelling mechanisms through the MoOx/Ge interface. To our knowledge, this is the first demonstration of a hole selective contact made of transition metal oxide on an n type semiconductor different from c Si. Thus, this work may have important implications toward the development of new device architectures, such as novel low cost Ge PV cells with possible applications in multijunction solar cells and thermophotovoltaics. Historically, the driving force for the use of Ge in photovoltaic (PV) applications has been as a substrate for GaAs space solar cells (Miller and Harris, 1980) the main reason being the higher thermal conductivity and the possibility of manufacturing thinner and lighter wafers with Ge than with GaAs. Later on, Ge/GaAs tandem solar cells were pursued to enhance the conversion efficiency (Chand et al. 1986) by using the Ge bottom cell to convert the infrared part of the solar spectrum. This progress eventually derived in the development of the current standard technology for space solar cells that consists of triple junction Ge/GaAs/GaInP structures, with AM0 conversion efficiencies in the range of 28 30% These cells have been also used in terrestrial applications within concentrated PV (CPV) systems, where they reached AM1.5D conversion efficiencies of 41.6% King et al. 2009) just below the current world record for solar to electricity conversion efficiency of 46.0% (Dimroth et al. 2016) Apart from solar applications, Ge PV cells have been considered as a low cost replacement for low band gap III V semiconductors in thermophotovoltaic (TPV) converters, in which thermal radiation is directly converted into electricity by infrared sensitive PV devices (Bauer, 2011; Chubb, 2007) In this context, Ge TPV cells could be used in a broad range of applications such as waste heat recovery (Bauer et al. 2003) solar thermal power (Ungaro et al. 2015; Lenert et al. 2014; Datas and Algora, 2013) space power (Datas and Marti, 2017) and energy storage (Datas et al. 2016) among many others. Current state of the art of Ge PV cells consist of p n junctions created by diffusion of dopants at high temperatures (Bitnar, 2003) For instance, p n junctions in p Ge have been created by diffusion of Vgroup atoms (typically P and As) during the first growing step of GaInP or GaAs nucleation layers within a Metal Organic CVD (MOCVD) reactor at temperatures of ~650 degC (Fernandez et al. 2008; Fernandez, 2010; Barrigon Montanes, 2014) Other groups have used the diffusion of Zn in n Ge substrates within a LPE reactor (Khvostikov et al. 2002) In an effort to reduce manufacturing costs of standalone Ge PV cells, IMEC reported devices with p n junctions created by spin on diffusion of P on p Ge by rapid thermal annealing at different temperatures (450 700 degC) (Posthuma et al. 2007; van der Heide, 2009; van der Heide et al. 2009) leading to the best reported 1 sun AM1.5G conversion efficiency for stand alone Ge PV cells of 7.9% (van der Heide et al. 2009) Surface passivation has been accomplished by forming different kinds of heterojunctions on Ge surface, such as Ge/GaAs (Khvostikov et al. 2002) or Ge/GaInP (Fernandez et al. 2008; Fernandez, 2010; Barrigon Montanes, 2014) by MOCVD or LPE (Khvostikov et al. 2002) or Ge/a Si (Posthuma et al. 2007; van der Heide, 2009; van der Heide et al. 2009; Posthuma et al. 2005) Ge/ SiNx (Nagashima et al. 2007) and Ge/a SixC1 x (Fernandez et al. 2008; Fernandez, 2010; Weiss et al. 2018) by PECVD. In order to further reduce the fabrication cost of Ge PV cells, it is desirable to eliminate the high temperature diffusion, and complex MOCVD or PECVD processes. In this regard, a particularly appealing option consists of substituting the doping step by carrier selective coatings with surface passivation properties that could be deposited at low temperatures. For this purpose, high electron affinity transition https:/doi.org/10.1016/j.solener.2019.02.009 Received 29 August 2018; Received in revised form 21 January 2019; Accepted 6 February 2019 Corresponding authors. Solar Energy 181 (2019) 357 360 0038 092X/ (c) 2019 International Solar Energy Society. Published by Elsevier Ltd. All rights reserved. T metal oxides (TMOs) such as MoO3, WO3, and V2O5, are very interesting candidates that have already been found effective to produce hole selective contacts on both n type and p type c Si (Gerling et al. 2015; Battaglia et al. 2014; Bullock et al. 2014; Vijayan et al. 2018) In this letter we report a Ge PV cell formed by a thin sub stoichiometric MoOx (x 3) layer on top of an n type crystalline Ge (c Ge) substrate, which behaves as a hole selective contact. To our knowledge, this is the first demonstration of a hole selective contact made with a TMO on an n type semiconductor different than c Si. Thus, it might open the door to new device architectures, not only for PV applications, but also in photonics and CMOS electronics, where the integration of TMOs is being investigated (Sanchez et al. 2016) along with the use of different semiconductors having higher carrier mobilities and extended spectral response than c Si, such as Ge (Reboud et al. 2017; Toriumi and Nishimura, 2017) The PV cell structure was fabricated on (1 0 0) oriented, Czochralski, n type Ge substrates (r=0.37O*cm, 350 mm thick) The substrate was cleaned by HCl: H2O (33% immediately prior to rear side passivation by PECVD of (i/n) a SiCx:H (4/15 nm, x~ 0.2) and a SiC (80 nm) stack deposited at ~300 degC. Next, the rear contact was created by laser firing of the a SiC stack to produce an array of ~60 mm diameter local diffusion points, separated by 600 mm pitch. This distance was chosen to introduce reasonable series resistance of ~0.1Ocm (Fischer, 2003) Laser firing was accomplished by means of a ~1200mW, l=1064 nm Nd/YAG laser system at a frequency of 4 kHz with 6 pulses per spot, following a similar approach developed for c Si devices (Lopez et al. 2018) The rear contact was finalized by means of an e beam evaporated Ti/Pd/Ag metal stack that provides lateral interconnection between fired points. The hole selective contact was formed at the front side of the device by means of very thin (nominally 20 nm) MoOx layer thermally evaporated from powdered MoO3 sources at ~8*10 mbar and a deposition rate of ~0.2 A/s (Gerling et al. 2015) A 75 nm thick ITO layer was subsequently deposited by RFSputtering on top of the MoOx layer to increase lateral electrical conductivity and minimize optical reflectivity. A sketch of the full PV cell structure and the TEM image of the MoOx/ITO interface are shown in Fig. 1, where a pronounced inter diffusivity between the layers is clearly observed. The 1x1 cm active area of the PV cells was defined by conventional lithographic techniques followed by mesa etching of the MoOx/ITO layers. Finally, the front Ag grid electrode (2 mm thick) was evaporated through a shadow mask for a 4% contacted area. One sun I V characterization of the PV cell was performed at 25 degC using a ORIEL 94021A (Newport) solar simulator, where the distance between the cell and the lamp was varied until the photo generated current density coincides with the one calculated through the integration of the cell' experimental external quantum efficiency (EQE) and the AM1.5G spectrum with 100mW/cm. The corresponding current density voltage (J V) curve under 1 sun illumination is shown in Fig. 2. The short circuit current density (JSC= 44.8mA/cm) outperforms that of the best performing state of the art Ge PV cells (43.2mA/cm) (van der Heide et al. 2009) On the other hand, a much lower open circuit voltage (138mV) is measured, compared to those reported in (Fernandez, 2010; van der Heide et al. 2009) (up to 265mV) which ultimately results in a lower FF (40.9% partially due to a non optimized metal grid that introduces a series resistance of 0.65 Ocm. As a result, an AM1.5G conversion efficiency of 2.53% is obtained. External quantum efficiency (EQE) of the PV cell is shown in Fig. 3 at short circuit conditions along with the EQE of Ge PV cells reported in (van der Heide, 2009) for a direct comparison. The improved EQE for wavelengths shorter than 600 nm might be explained by the reduction of the recombination close to the front surface compared to the one existing in the highly doped emitters (10 10 cm) used in (van der Heide, 2009) Such a low recombination does not necessary indicate a good chemical surface passivation, i.e. strong reduction of interface state density, but it could be related to a strong electric field that unbalances carrier densities, i.e. field effect passivation. The electric field located at the surface creates an electrostatic potential which, under thermal equilibrium, is the potential barrier built at the junction (Vbi) Then, the higher Vbi, the stronger the electric field and, thus, the better the surface passivation. In order to measure Vbi, capacitance voltage measurements of the cell in reverse bias were performed at 10 kHz using HP4294A impedance analyser with a signal amplitude of 30mV following the same approach than in (Almora et al. 2017) where similar structures on c Si substrates are characterized. This data can be Fig. 1. Sketch of the fabricated solar cell. Focus: TEM image of the MoOx interlayer of the final device. Fig. 2. Current density voltage curve of the Ge PV cell manufactured in this work under AM1.5 G illumination conditions. A. Alcaniz, et al. Solar Energy 181 (2019) 357 360
author_names: A Alcaniza

G Lopeza

I Martina

A Jimenezb

A Datasa

Emanuela Callea

Erlyta Septa Rosa

L G Gerlinga

C Voza

C del Canizob

Ramon Alcubillaa
title: Germanium photovoltaic cells with MoOx hole selective contacts
year: 2019

abstract: The ISIS Neutron and Muon Source, based at the Rutherford Appleton Laboratory, begins with an injector line that accelerates an H ion beam to 70 MeV. The beam then travels through a High Energy Drift Space (HEDS) before passing through an electron stripping foil upon injection into the proton synchrotron, which provides acceleration up to 800 MeV. During machine setup, beam profile measurements in the HEDS are taken using scanning wire monitors, which drive a single pair of measuring wires, one per plane, through the beam aperture using an analogue servo motor. Many of these monitors have been in operation since ISIS was commissioned in 1984 and as such are coming to the end of their operational lifetimes, meaning a new suite of monitors is required. A prototype monitor has been developed along with new electronics and a control system to test the operation of a new drive mechanism based around a stepper motor and resolver, providing increased precision and reliability. This paper discusses the development of a new multi wire monitor design, and the associated upgrade to the electronics and control system. INTRODUCTION The ISIS linac accelerates H ions to 70 MeV, producing a 50 Hz pulsed beam with a pulse length of 200 ms. This beam travels through a HEDS before injection into an 800 MeV proton synchrotron. After acceleration, protons are transferred into one of two Extracted Proton Beamlines (EPBs) and delivered to a tungsten target, driving the neutron spallation process. Measurement of the beam's profile throughout the accelerator is vital during machine setup, whilst also providing valuable information during accelerator studies, and for understanding beam loss mechanisms. Three types of profile monitor are in use around ISIS: wire scanners and wire grid 'harp' monitors, which are both destructive to the beam [1] and Ionisation Profile Monitors (IPMs) which provide non destructive measurements. IPMs are used for profile measurements around the synchrotron ring, as any induced beam loss would quickly build to unsustainable levels over multiple orbits. Non destructive profile monitoring at ISIS is described in further detail in [2] [3] Destructive profile monitors are installed around the HEDS and EPBs and are crucial during machine setup, providing trusted and reliable measurements of the beam. Profiles are taken by moving conducting wires into the path of the beam and measuring the current generated by secondary electron emission, induced as beam particles pass through the wires. ISIS is operated at a slower rate of 1.6 Hz while these monitors are in use, reducing both the levels of induced beam loss and the risk of damage to the measuring wires. Harp monitors are installed along both EPBs, consisting of retractable grids of wires which are inserted into the beam aperture using a pneumatic system. The grids contain 24 wires per plane with spacing set to either 6 mm or 10 mm, depending on the beam distribution in each location. Along the HEDS the beam is significantly smaller, with beam widths typically between 10 30 mm. As a result wire scanners are used here instead to allow higher resolution profiles to be measured, in addition to being cheaper to manufacture and causing less beam loss. A single pair of measuring wires is scanned across the beam aperture by a motor driven linear stage, mounted at 45 to the beam (Fig. 1) As a result, wire displacement in both the horizontal and vertical planes is equal when the wire head is moved, with the distance travelled along each plane inversely proportional to the linear stage motion by a factor of 2. The wires are moved through the beam in horizontal and vertical steps, typically of 4 mm, and a reading is taken at each position to build up a 2D profile measurement over multiple beam pulses. Figure 1: Orientation of a wire scanner head, with a signal wire and pair of bias wires mounted in each plane. There are currently 15 wire scanners installed along the ISIS HEDS, many of which have been operational for over 30 years and have surpassed their design lifetimes. As a result a replacement programme is now underway, and a new monitor design has been developed alongside an upgraded control system and electronics. MONITOR DESIGN A prototype monitor of the new design has been built, tested and recently installed in the ISIS HEDS. The monitor offers improved measurement resolution and precision compared with existing monitors, in addition to enhanced reliability. As the motion undergone during measurement ___________________________________________ daniel.harryman@stfc.ac.uk christopher.wilcox@stfc.ac.uk 6th International Beam Instrumentation Conference IBIC2017, Grand Rapids, MI, USA JACoW Publishing ISBN: 978 3 95450 192 2 doi:10.18429/JACoW IBIC2017 WEPCC18 WEPCC18 396 Co nt en tf ro m th is w or k m ay be us ed un de rt he te rm so ft he CC BY 3. 0 lic en ce (c) 20 18 A ny di str ib ut io n of th is w or k m us tm ai nt ai n at tri bu tio n to th e au th or (s tit le of th e w or k, pu bl ish er ,a nd D O I. 6 Beam Profile Monitors causes wear in several components, predicted lifetime usage was a key factor during the design phase. All components were selected to ensure a design lifetime of 20 years heavy use, corresponding to 8,000 scanning cycles. Measuring and Bias Wires Silicon Carbide (SiC) coated carbon wires with diameters of 142 mm are used for the measuring wires. This material is an ideal choice due to its rigidity and high emissivity, meaning it does not suffer from excess heating whilst intercepting the beam [4] The wires are left unconstrained at their outermost extent to allow for thermal expansion to occur without causing damage. Instead the wires threaded through small guide holes cut into Macor(r) mounting blocks to ensure they remain aligned during operation. Each measuring wire is flanked by a pair of bias wires (Fig. 1) these can be set to a positive bias voltage of up to 200 V to attract electrons emitted from the measuring wire, preventing recombination from affecting the beaminduced signal during measurement. Motion System A radiation hardened stepper motor, resolver and brake, manufactured by Empire Magnetics, is used to drive the linear stage and wire head through the beam (Fig. 2) [5] Stepper motors rotate in small, discrete steps, ensuring highly accurate levels of rotation. Additionally a strong holding torque is generated while these motors are energised and at rest. An electromagnetic brake, released when supplied with current, is connected to prevent shaft movement when the system is not in use, and provides a safeguard in the event of power failure. Figure 2: Simplified layout of the profile monitor. A 5:1 gearbox is connected between the motor and the linear stage, providing extra protection from the compression force generated by the bellows when the wires are withdrawn from the beam aperture. The resolver provides a measurement of the wire positions, producing signals induced by the motor's rotations which are then passed through a resolver to encoder converter for processing in the motor drive unit. The overall system can theoretically measure the position of the wires to a resolution less than 0.1 mm, comfortably exceeding the precision required. The scanning speed required is set by the reduced rate of 1.6 Hz at which ISIS is operated during measurement. Movement of the wires between each scan position is completed during the time between adjacent beam pulses, ensuring the profile is measured as quickly as possible. Honeywell 9HM1 microswitches, suitable for use in radiation environments, are used as limit switches and positioned to set the linear stage stroke to 156 mm, 6 mm larger than the beam aperture [6] When the monitor performs a profile scan, the wires are centred in the beam aperture relative to these switches, meaning precise switch activation positions are vital. During testing the switches demonstrated excellent precision, with the measured shaft positions at each limit undergoing variations of just 40 mm over 2,000 cycles of operation. Direct Position Measurement A linear potentiometer is attached to the monitor shaft, providing a secondary reading of the wire positions. This is useful for detecting slipping of the monitor's shaft position, which can occur over a number of years. It also provides a method of position measurement in the event of a power failure causing the motor control unit's encoder to reset. The potentiometer measures at a lower resolution of approximately 1 mm but is more robust and provides an independent safeguard to show if the wire head is positioned inside the beam aperture inadvertently. The voltages measured by the potentiometer range between 14 V, chosen so that should anything happen to the 15 V supply fed to the potentiometer it would be instantly visible to the electronics. Radiation Protection The monitor's limit switches and motor systems were selected for their suitability for use in radiation environments, as previously mentioned. However these components are significantly more expensive as a result, and potentially unnecessary as in some monitor locations the expected dose is relatively low. To test these dose levels a TID (Total Ionisation Dosimeter) monitoring system, recently developed at ISIS, will be used to measure radiation levels along the HEDS, to test whether more cost effective components can be used on some of the new monitors [7] ELECTRONICS Setup Two units are used to control the profile monitor: a custom motor control unit, used to control the monitors drive system and provide a live position of the monitor; and a National Instruments cRIO embedded controller, which interfaces with the ISIS accelerator control system and acquires data from the monitor [8] 6th International Beam Instrumentation Conference IBIC2017, Grand Rapids, MI, USA JACoW Publishing ISBN: 978 3 95450 192 2 doi:10.18429/JACoW IBIC2017 WEPCC18 6 Beam Profile Monitors WEPCC18 397
author_names: Daniel Harryman

Christopher C Wilcox
title: An Upgraded Scanning Wire Beam Profile Monitoring System for the ISIS High Energy Drift Space
year: 2018