Cone Field Research Articles

Differentially Positive Systems

The paper introduces and studies differentially positive systems, that is, systems whose linearization along an arbitrary trajectory is positive. A generalization of Perron–Frobenius theory is developed in this differential framework to show that the property induces a conal order that strongly constrains the asymptotic behavior of solutions. The results illustrate that behaviors constrained by local order properties extend beyond the well-studied class of linear positive systems and monotone systems, which both require a constant cone field and a linear state space.

Uniform hyperbolicity of locally maximal chaotic invariant sets in a system with only one stable equilibrium

By the methods of Poincaré map and the cone field theory, we present a rigorous computer-assisted method to verify the existence of a locally maximal uniformly hyperbolic chaotic invariant set for an autonomous chaotic system which has only one stable equilibrium. At the same time, our arguments show that the second return Poincaré map restricted to the hyperbolic set is indeed topologically conjugate to the 2-shift map.

Landform assemblage in Isidis Planitia, Mars: Evidence for a 3 Ga old polythermal ice sheet

The floor of Isidis Planitia, a giant impact basin located close to the martian equator, exhibits a landform assemblage, nicknamed Thumbprint Terrain, made of Arcuate Ridges, Aligned Cones, Isolated Cones, Cone Fields, associated with a peripheral network of Sinuous Ridges, Linear Depressions, and Mounds. From a new comprehensive mapping initiative of these landforms and from comparisons with terrestrial analogues (ribbed moraines, dirt cones, kettle holes, eskers, tunnel valleys and moraine plateaux), we demonstrate that this distinctive assemblage is a glacial landsystem inherited from the presence of a massive polythermal ice sheet over the basin during the Hesperian. The flow of the ice sheet was controlled by its basal thermal regime. Wet-based conditions led to the formation of Arcuate Ridges and Aligned Cones in most parts of the basin, while a negative geothermal anomaly due to impact-related crustal thinning was responsible for cold-based conditions in its central part, where only Isolated Cones and Cones Fields are present. Sinuous Ridges, Linear Depressions and Mounds at the basin margins are interpreted as relicts of a radial network of subglacial channels, which drained the glacial meltwater produced within the interior of the ice sheet across its cold-based periphery.

Intraplate seismicity across the Cape Verde swell: A contribution from a temporary seismic network

We present an analysis and characterization of the regional seismicity recorded by a temporary broadband seismic network deployed in the Cape Verde archipelago between November 2007 and September 2008.The detection of earthquakes was based on spectrograms, allowing the discrimination from low-frequency volcanic signals, resulting in 358 events of which 265 were located, the magnitudes usually being smaller than 3. For the location, a new 1-D P-velocity model was derived for the region showing a crust consistent with an oceanic crustal structure. The seismicity is located mostly offshore the westernmost and geologically youngest areas of the archipelago, near the islands of Santo Antão and São Vicente in the NW and Brava and Fogo in the SW. The SW cluster has a lower occurrence rate and corresponds to seismicity concentrated mainly along an alignment between Brava and the Cadamosto seamount presenting normal faulting mechanisms. The existence of the NW cluster, located offshore SW of Santo Antão, was so far unknown and concentrates around a recently recognized submarine cone field; this cluster presents focal depths extending from the crust to the upper mantle and suggests volcanic unrest. No evident temporal behaviour could be perceived, although the events tend to occur in bursts of activity lasting a few days. In this recording period, no significant activity was detected at Fogo volcano, the most active volcanic edifice in Cape Verde.The seismicity characteristics point mainly to a volcanic origin. The correlation of the recorded seismicity with active volcanic structures agrees with the tendency for a westward migration of volcanic activity in the archipelago as indicated by the geologic record.

Modelling Alzheimer-like cognitive deficits in rats using biperiden as putative cognition impairer

To enable the development of effective treatments for dementias such as Alzheimer's disease (AD), it is important to establish valid animal models of cognitive impairments. Scopolamine is widely used to induce cognitive deficits in animal models of AD, but also causes non-cognitive side effects. We assessed whether biperiden, a selective antagonist of M1 muscarinic receptors, which are predominantly expressed in brain areas involved in cognitive processes, causes cognitive deficits without inducing peripheral side-effects. Two different doses of biperiden (3 or 10mgkg−1) on the acquisition of a spatial cone field task were assessed in male Lister Hooded rats. This task measures, among others, spatial working (WM) – and reference memory (RM) simultaneously. Biperiden did not impair learning of the task. The animals reached asymptotic levels for all variables except reference memory and the number of rewards collected. However, the 10mgkg−1 dose decreased the tendency of rats to use searching strategies to solve the task and made them slower to start searching and completing the task. In conclusion, though no effects on WM and RM performance were seen, the present study cannot conclude that biperiden acts as a more selective cognition impairer than scopolamine in other rats strains and/or other doses than those tested.

Development of topographic asymmetry: Insights from dated cinder cones in the western United States

AbstractTopographic asymmetry, that is, differences in the morphology of landscapes as a function of slope aspect, can be used to infer ecohydrogeomorphic feedback relationships. In this study, we document the dependence of topographic gradients and drainage densities on slope aspect and time/age in four Quaternary cinder cone fields in Arizona, Oregon, and California. Cinder cones are particularly useful as natural experiments in geomorphic evolution because they begin their evolution at a known time in the past (many have been radiometrically dated) and because they often have simple, well‐constrained initial morphologies. North‐facing portions of cinder cones have steeper topographic gradients and higher mean vegetation cover (i.e., Normalized Difference Vegetation Index, or NDVI, values) under current climatic conditions compared with corresponding south‐facing portions of cones within each volcanic field. Drainage density is also higher on north‐facing portions of cones in three of the four volcanic fields. These differences in topography were not present initially but developed progressively over time, indicating that the asymmetry is a result of post‐eruption geomorphic processes. To test alternative hypotheses for the slope‐aspect control of topography, we developed a numerical model for cinder cone evolution and a methodology for estimating local paleovegetation cover as a function of elevation, slope aspect, and time within the Quaternary. The numerical model results demonstrate that rates of colluvial transport were higher on south‐facing hillslopes in at least three of the four cinder cones fields. Our paleovegetation analysis suggests that in the two Arizona volcanic fields we studied, higher rates of colluvial transport on south‐facing hillslopes were the result of greater time‐averaged vegetation cover and hence higher rates of sediment transport by floral bioturbation. Our results illustrate the profound impact that relatively small variations in solar insolation can have on landscapes via feedbacks among hydrology, vegetation cover, and sediment transport.

SU‐E‐J‐109: Testing the KV Imaging Center Congruence with Radiation Isocenter of Small MLC and SRS Cone Field On Two Machines

Purpose:Orthogonal kV image pairs are used for target localization when fiducial markers are implanted. CBCT is used to verify cone SRS setup. Therefore it is necessary to evaluate the isocenter congruence between radiation fields and kV imaging center. This study used a simple method to evaluate the isocenter congruence, and compared the results for MLC and cone fields on two different Linacs.Methods:Varian OBI block was attached on the couch. It has a central 1mm BB with markers on three surfaces to align with laser. KV and MV images were taken at four cardinal angles. A 3×3cm2 MLC field and a 20mm cone field were irradiated respectively. On each kV image, the distance from BB center to the kV graticule center were measured. On the MV image of MLC field, the center of radiation field was determined manually, while for cone field, the Varian AM maintenance software was used to analyze the distance between BB and radiation field. The subtraction of the two distances gives the discrepancy between kV and radiation centers. Each procedure was repeated on five days at Trilogy and TrueBeam respectively.Results:The maximum discrepancy was found in the longitudinal direction at 180° gantry angel. It was 1.5±0.1mm for Trilogy and 0.6±0.1mm for TrueBeam. For Trilogy, although radiation center wobbled only 0.7mm and image center wobbled 0.8mm, they wobbled to the opposite direction. KV Pair using gantry 180° should be avoided in this case. Cone vs. kV isocenter has less discrepancy than MLC for Trilogy.Conclusion:Radiation isocenter of MLC and cone field is different, so is between Trilogy and TrueBeam. The method is simple and reproducible to check kV and radiation isocenter congruence.

SU-E-T-122: Dosimetric Comparison Between Cone, HDMLC and MicroMLC for the Treatment of Trigeminal Neuralgia

Purpose: The purpose of this work was to evaluate the dosimetric characteristics of three collimation systems, 5mm circular cone (Brainlab) and square fields of 5mm with HDMLC (Varian) and microMLC Moduleaf, Siemens) for trigeminal neuralgia treatment. Methods: A TPS Iplan v4.5 BrainLAB was used to do treatment plans for each collimations system in a square solid water phantom with isocenter at 5cm depth. Single field and treatment plan including 11 arcs with fix field and 100° gantry range was made for each collimation systems. EBT3 films were positioned at isocenter in a coronal plane to measured dose distribution for all geometries. Films were digitized with a Vidar DosimetryPro Red scanner with a resolution of 89dpi and RIT113v6.1 software was used for analysis. Penumbra region (80%–20%), FWHM and dose percentage at 5mm and 10mm from CAX were determined. All profiles were normalized at CAX. Results: For single beam the penumbra (FWHM) was 1.5mm (5.3mm) for the cone, 1.9mm (5.5mm) for HDMLC and 1.8mm (5.4mm) for the microMLC. Dose percentage at 5mm was 6.9% for cone, 12.5% for HDMLC and 8.7% for the microMLC. For treatment plan the penumbra (FWHM) was 2.58mm (5.47mm) for the cone, 2.8mm (5.84mm) for HDMLC and 2.58mm (6.09mm) for the microMLC. Dose perecentage at 5mm was 13.1% for cone, 16.1% for HDMLC, 15.2% for the microMLC. Conclusion: The cone has a dose falloff larger than the microMLC and HDMLC, by its reduced penumbra, this translates into better protection of surrounding healthy tissue, however, the microMLC and HDMLC have similar accuracy to cone.

Volcanic Geotopes and Their Geosites Preserved in an Arid Climate Related to Landscape and Climate Changes Since the Neogene in Northern Saudi Arabia: Harrat Hutaymah (Hai’il Region)

Maars and tuff rings are some of the most common volcanic landforms on Earth. They are inferred to be the product of the explosive interaction between rising magma (mostly basaltic) and various groundwater sources or surface water bodies. Maar and tuff ring volcanoes are commonly associated with extensive scoria cone fields that are fed by dispersed volcanic vents, providing access to the surface for magma over a long period of time (thousands to millions of years’ timescale). The presence of maar and tuff ring volcanoes, therefore, is an important signifier of the availability of water from sub-surface and/or surface water sources. As environmental conditions change over time, the groundwater table, as well as surface water availability, can change dramatically and this is likely be reflected in the type of volcanoes formed on the surface. Such changes are the most graphic and visible in volcanic fields that are today located in arid environments, where the presence of young volcanoes formed through interactions with water demonstrates how the environment can change over geological timescales. Therefore, these areas have high geoeducational values and can contribute to our understanding of how external (water sources controlled by climatic factors) and internal (magmatic) forces can shape the style of volcanism of a volcanic field. Harrat Hutaymah is one of the excellent locations where there is great abundance of maars and tuff rings. They are located in an area dominated today by various types of deserts. Harrat Hutaymah, therefore, demonstrates the global geological changes that can affect the style of volcanism and hence the resulting volcanic landscape. The richness of the region in archaeological sites and early settlements indicates the importance of this region for the early evolution of civilizations in the Middle East, which is likely to have been enhanced and/or modified by similar environmental changes over a much smaller timescale. Harrat Hutaymah provides a firm basis to demonstrate global changes through its volcanic heritage that are easily accessible and well exposed.

Failure Investigation at a Collapsed Deep Excavation in Very Sensitive Organic Soft Clay

Collapse of a 15.7-m-deep excavation in very sensitive organic soft clay in Hangzhou, China, is presented in this paper. The collapse of the excavation caused the break and/or inclination of the retaining walls, the wracking of the supporting system, significant sinking of a major road adjacent to the excavation site, and also the break in a water main beneath the road. After the collapse, the ground disturbance due to the collapse was investigated by cone penetration tests (CPTs) and field vane shear tests (VSTs). A simplified method, based on the CPT and VST test results, was used to evaluate the strength reduction ratio (SRR) of the in situ soils. According to the SRR values of the soils at different depths, the lower boundaries of the severely disturbed soils were determined and a possible slip failure surface passing through the bottom of the severely disturbed soils was justified. The factors of safety (FOSs) against basal heave of the excavation calculated from various methods were 1.05, 0.74 and 0.89, respectively. These computed values were much smaller than the corresponding recommended values. The stability number N of the excavation was calculated to be 7.4. The overall FOS was studied using the shear strength reduction technique based on a finite-element method (FEM) program. The FEM analysis results indicated that the FOS of the excavation was 0.97, and the computed slip failure surface fit well with that from the soil disturbance investigation. The failure mechanism of the excavation was then justified to be a basal heave. The main reasons leading to the collapse and lessons learned from the collapse are discussed. The investigation of the failure provides experiences and lessons for deep excavation design in very sensitive organic soft clay.

Cone Fields and Topological Sampling in Manifolds with Bounded Curvature

A standard reconstruction problem is how to discover a compact set from a noisy point cloud that approximates it. A finite point cloud is a compact set. This paper proves a reconstruction theorem which gives a sufficient condition, as a bound on the Hausdorff distance between two compact sets, for when certain offsets of these two sets are homotopic in terms of the absence of μ-critical points in an annular region. We reduce the problem of reconstructing a subset from a point cloud to the existence of a deformation retraction from the offset of the subset to the subset itself. The ambient space can be any Riemannian manifold but we focus on ambient manifolds which have nowhere negative curvature (this includes Euclidean space). We get an improvement on previous bounds for the case where the ambient space is Euclidean whenever μ≤0.945 (μź(0,1) by definition). In the process, we prove stability theorems for μ-critical points when the ambient space is a manifold.

Hydrovolcanic tuff rings and cones as indicators for phreatomagmatic explosive eruptions on Mars

AbstractHydrovolcanism is a common natural phenomenon on Earth and should be common on Mars, too, since its surface shows widespread evidence for volcanism and near‐surface water. We investigate fields of pitted cones in the Nephentes/Amenthes region at the southern margin of the ancient impact basin, Utopia, which were previously interpreted as mud volcanoes. The cone fields contain pitted and breached cones with associated outgoing flow‐like landforms. Based on stratigraphic relations, we determined a Hesperian or younger model age. We test the hypothesis of a (hydro)volcanic origin. Based on a detailed morphological and morphometrical analysis and an analysis of the regional context, an igneous volcanic origin of these cones as hydrovolcanic edifices produced by phreatomagmatic eruptions is plausible. Several lines of evidence suggest the existence of subsurface water ice. The pitted cones display well‐developed wide central craters with floor elevations below the preeruptive surface. Their morphometry and the overall appearance are analogous to terrestrial tuff cones and tuff rings. Mounds that are also observed in the same region resemble terrestrial lava domes. The hydrovolcanic interaction between ascending magma and subsurface water and/or water ice may explain the formation of the pitted cones, although other scenarios such as mud volcanism cannot be ruled out. Together with the mounds, the cones might represent effusive and explosive edifices of a monogenetic volcanic field composed of lava domes, tuff rings, tuff cones, and possibly maars.

NETVOLC: An algorithm for automatic delimitation of volcano edifice boundaries using DEMs

Accurately delimiting boundaries is required for characterizing landforms through measurement of their geomorphometric parameters. Volcanism produces a wide range of landforms, from symmetric cones to very irregular massifs, that can gradually merge with the surroundings and contain other elements, thus complicating landform delimitation. Most morphometric studies of volcanoes delimit landforms manually, with the inconvenience of being time-consuming and subjective. Here we propose an algorithm, NETVOLC, for automatic volcano landform delimitation based on the premise that edifices are bounded by concave breaks in slope. NETVOLC applies minimum cost flow (MCF) networks for computing the best possible edifice outline using a DEM and its first- and second-order derivatives. The main cost function considers only profile convexity and aspect; three alternative functions (useful in complex cases) also consider slope, elevation and/or radial distance. NETVOLC performance is tested by processing the Mauna Kea pyroclastic cone field. Results using the main cost function compare favorably to manually delineated outlines in 2/3rds of cases, whereas for the remaining 1/3rd of cases an alternative cost function is needed, introducing some degree of subjectivity. Our algorithm provides a flexible, objective and time-saving tool for automatically delineating volcanic edifices. Furthermore, it could be used for delineating other landforms with concave breaks in slope boundaries. Finally, straightforward modifications can be implemented to extend the algorithm capabilities for delimiting landforms bounded by convex breaks in slope, such as summit craters and calderas.

CPT-based Seismic Liquefaction Potential Evaluation Using Multi-gene Genetic Programming Approach

This study examines the potential of multi-gene genetic programming (MGGP) based classification approach to evaluate liquefaction potential of soil in terms liquefaction index (LI) using a large database from post liquefaction cone penetration test (CPT) measurements and field manifestations. The database consists of CPT measurements; cone tip resistance (qc), friction ratio (Rf), vertical total stress (σv) and vertical effective stress of soil (σv′), seismic parameters; peak horizontal ground surface acceleration (amax) and earthquake moment magnitude (Mw), and the depth under consideration (z). The MGGP models (Model-I and Model-II) are developed for predicting occurrence and non-occurrence of liquefaction on basis of combination of above input parameters. The performance of the Model-I (95 %) is found to be more efficient compared to available artificial neural network model (91 %) and that of the Model-II (97 %) is found to be at par with the available support vector machine model (97 %) in terms of rate of successful prediction of liquefied and non-liquefied cases for testing data. Using an independent database of 96 cases, the overall classification accuracies are found to be 87 and 86 % for Model-I and Model-II respectively. Sensitivity analyses are made to identify the important parameters contributing to the prediction of LI.

ОСОБЕННОСТИ ИНЖЕНЕРНО-ГЕОЛОГИЧЕСКИХ ИЗЫСКАНИЙ ПРИ ЗАСТРОЙКЕ ГОРОДСКИХ КВАРТАЛОВ И КРУПНЫХ ЗАГОРОДНЫХ ТЕРРИТОРИЙ

The authors discuss peculiarities of engineering geological surveys of contaminated urban and rural soils. The authors provide examples of the influence produced by the scope and composition of geological engineering surveys on the reliability of foundation soils. The authors also provide their assessments in terms of deformation-related properties of filled soils and their employment as immediate foundation soils for a residential house in Marfino. The article is polemical, and it may raise animated discussions of the problem. The authors believe that geological engineering tests held in urban areas and preceding the implementation of any construction projects should not be limited to cone penetration and field tests of soils limited to the grid, and at the stage of the project design, any tests shall be held within the perimeter of a designed building according to the effective legislation. In the course of field tests, geologists must pay special attention to the identification of contaminated soils of different origin, especially if the foundation is made of plates. The depth of the contamination may reach 10 meters in Moscow and in the Moscow Region. Identification of backfill soils may be particularly difficult.

Error Compensation for Area Digital Sun Sensor

Compared to the error factors of the Linear Array Digital Sun Sensor (DSS), those of the Area Array DSS are complicated and methods used for error compensation are not valid or simple enough. This paper presents the main error factors of the Area Array DSS and proposes an effective method to compensate them. The procedure of error compensation of Area Array DSS includes three steps. First, the geometric error of calibration is compensated; second, the coordinate map method is used to compensate the error caused by optical refraction; third, the high order polynomial-fitting method is applied to calculate the tangent of the sun angles; finally, the arc tangent method is used to calculate the sun angles. Experimental results of the product of the High Accuracy Sun Sensor indicate that the precision is better than 0.02° during the cone field of view (CFOV) of 10°, and the precision is better than 0.14° during the CFOV 10° to 64°. The proposed compensation method effectively compensates the major error factors and significantly improves the measure precision of the Area APS DSS.

Application of shear wave velocity for evaluation of equivalent radius of penetrometers

As a penetrometer is pushed into saturated soft soils, excess pore water pressure affected by the disturbed zone is generated. This excess pore water pressure, which dissipates radially, is related to the probe size and shape. The probe size and shape may be represented by an equivalent radius. The aim of this paper is to evaluate the equivalent radius of a penetrometer using the horizontal coefficient of consolidation. Three penetrometers including the cone penetrometer, dilatometer, and Field Velocity Probe (FVP), are used within a large laboratory calibration chamber and in the field. For the calibration chamber tests, a clay–sand mixture is prepared and consolidated under a vertical stress of 160 kPa. These dissipation tests are conducted at a depth that is equal to half the height of the chamber. For the field tests, three penetrometers are penetrated into soft soils through a gravel layer and a sand mat layer. These dissipation tests are implemented at a depth of 24 m. The cone penetrometer, dilatometer, and FVP measure the change of the pore water pressure, the closing pressure value, and the shear wave velocity, respectively. From these six dissipation tests, the equivalent radii of the dilatometer and the FVP are obtained. In addition, an empirical equation for the calculation of the equivalent radius of the penetrometer is suggested.

Comparison of cone beam CT device and field of view for the detection of simulated periapical bone lesions

We aimed to assess the diagnostic accuracy of different cone beam CTs (CBCTs) and the influence of field of view (FOV) in diagnosing simulated periapical lesions. 6 formalin-fixed lateral mandibular specimens from pigs were used for creating 20 standardized periapical bone defects. 18 roots were selected for the control group. Three CBCT devices [Accuitomo 3D® (Morita, Kyoto, Japan), NewTom 3G (Quantitative Radiology, Verona, Italy) and Scanora® (Soredex, Tuusula, Finland)] and three FOVs (NewTom 3G® FOV 6, 9 and 12 inches) were used to scan the mandible. Five observers assessed the images, using a five-point probability scale for the presence of lesions. Specificity, sensitivity and areas under the receiver operating characteristic (ROC) curves were calculated. Sensitivity ranged from 72% to 80%. Specificity ranged from 60% to 77%. A difference in scoring between Scanora and the other two devices existed only in the control group. ROC analysis for different FOVs showed a decreased sensitivity with an increasing FOV, but this difference was not significant. the control group, there was a difference between the CBCT devices regarding their specificity. FOV size did not show any difference in diagnostic performance. In cases in which conventional radiographic methods in combination with clinical evaluation are not sufficient, CBCT may be the method of choice to assess periapical pathology. CBCT examinations should be complementary to a clinical examination and FOV adaptation can be utilized to keep the dose to the patient as low as possible.

New seismo-stratigraphic and marine magnetic data of the Gulf of Pozzuoli (Naples Bay, Tyrrhenian Sea, Italy): inferences for the tectonic and magmatic events of the Phlegrean Fields volcanic complex (Campania)

A detailed reconstruction of the stratigraphic and tectonic setting of the Gulf of Pozzuoli (Naples Bay) is provided on the basis of newly acquired single channel seismic profiles coupled with already recorded marine magnetics gathering the volcanic nature of some seismic units. Inferences for the tectonic and magmatic setting of the Phlegrean Fields volcanic complex, a volcanic district surrounding the western part of the Gulf of Naples, where volcanism has been active since at least 50 ka, are also discussed. The Gulf of Pozzuoli represents the submerged border of the Phlegrean caldera, resulting from the volcano-tectonic collapse induced from the pyroclastic flow deposits of the Campanian Ignimbrite (35 ka). Several morpho-depositional units have been identified, i.e., the inner continental shelf, the central basin, the submerged volcanic banks and the outer continental shelf. The stratigraphic relationships between the Quaternary volcanic units related to the offshore caldera border and the overlying deposits of the Late Quaternary depositional sequence in the Gulf of Pozzuoli have been highlighted. Fourteen main seismic units, both volcanic and sedimentary, tectonically controlled due to contemporaneous folding and normal faulting have been revealed by geological interpretation. Volcanic dykes, characterized by acoustically transparent sub-vertical bodies, locally bounded by normal faults, testify to the magma uprising in correspondence with extensional structures. A large field of tuff cones interlayered with marine deposits off the island of Nisida, on the western rim of the gulf, is related to the emplacement of the Neapolitan Yellow Tuff deposits. A thick volcanic unit, exposed over a large area off the Capo Miseno volcanic edifice is connected with the Bacoli-Isola Pennata-Capo Miseno yellow tuffs, cropping out in the northern Phlegrean Fields.

On the creation of high energy bremsstrahlung and intensity by a multitarget and repeated focusing of the scattered electrons by small-angle backscatter at the wall of a cone and magnetic fields—A possible way to improve linear accelerators in radiotherapy and to verify Heisenberg–Euler scatter

The yield of bremsstrahlung from collisions of fast electrons (energy at least 6MeV) with a Tungsten target can be significantly improved by exploitation of Tungsten wall scatter in a multi-layered target. The Tungsten wall can serve to refocuse small angle scattered electrons. It is necessary that the thickness of one Tungsten layer does not exceed 0.02mm. Further repeated focusing of electrons results from suitable magnetic fields with field strength between 0.5T and 6T (if the cone with multi-layered targets is rather narrow). Linear accelerators in radiation therapy only need repeated focusing by wall scatter without further magnetic fields (standard case: ca. 100–000 plates with 0.01mm thickness and 1mm distance between the plates). The construction of a very narrow bremsstrahlung beam with extremely high photon intensity requires an additional strong magnetic field (order 1–6T), which provides the possibility to check Heisenberg–Euler scatter of high energy photons.