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Migration of plasma erosion products in plasma facilities is studied experimentally and numerically within the framework of modeling transport of plasma-facing materials in the diagnostic ducts of fusion devices. Material transport simulation is discussed for two cases of low and high background neutral gas pressures. Monte Carlo software KITe was used to simulate transport at a neutral gas background pressure 0.1â€"0.5 Paâ€"typical during steady-state tokamak operation and during pressure pulses caused by edge localized modes (ELMs). The simulation approach was implemented to describe experiments at the MAGNUM-PSI facility. Fluid dynamic code FLUENT is used to simulate transport during pressure surges as high as 1000 Pa, which can occur in the case of severe disruptions in tokamak plasma discharges, such as vertical displacement events (VDE) or accidental events. The hydrodynamic approach was verified in simulation of target sputtering in the QSPA plasma gun facility. [ABSTRACT FROM AUTHOR]

Purpose: A clinical implementation of ion‐beam radiography (iRad) is envisaged to provide a method for on‐couch verification of ion‐beam treatment plans. The aim of this work is to introduce and evaluate a method for quantitative water‐equivalent thickness (WET) measurements for a specific helium‐ion imaging system for WETs that are relevant for imaging thicker body parts in the future. Methods: Helium‐beam radiographs (αRads) are measured at the Heidelberg Ion‐beam Therapy Center with an initial beam energy of 239.5 MeV/u. An imaging system based on three pairs of thin silicon pixel detectors is used for ion path reconstruction and measuring the energy deposition (dE) of each particle behind the object to be imaged. The dE behind homogeneous plastic blocks is related to their well‐known WETs between 280.6 and 312.6 mm with a calibration curve that is created by a fit to measured data points. The quality of the quantitative WET measurements is determined by the uncertainty of the measured WET of a single ion (single‐ion WET precision) and the deviation of a measured WET value to the well‐known WET (WET accuracy). Subsequently, the fitted calibration curve is applied to an energy deposition radiograph of a phantom with a complex geometry. The spatial resolution (modulation transfer function at 10 % —MTF10%) and WET accuracy (mean absolute percentage difference—MAPD) of the WET map are determined. Results: In the optimal imaging WET‐range from ∼280 to 300 mm, the fitted calibration curve reached a mean single‐ion WET precision of 1.55 ±$\,{\pm}\,$ 0.00%. Applying the calibration to an ion radiograph (iRad) of a more complex WET distribution, the spatial resolution was determined to be MTF10% = 0.49 ±$\,{\pm}\,$ 0.03 lp/mm and the WET accuracy was assessed as MAPD to 0.21 %. Conclusions: Using a beam energy of 239.5 MeV/u and the proposed calibration procedure, quantitative αRads of WETs between ∼280 and 300 mm can be measured and show high potential for clinical use. The proposed approach with the resulting image qualities encourages further investigation toward the clinical application of helium‐beam radiography. [ABSTRACT FROM AUTHOR]

Poster Highlights: Poster highlights 15: Particles and microbeams PH-0477: Effectiveness of fractionated carbon ion treatments in three rat prostate tumors C. Glowa, P. Peschke, S. Brons, J. Debus, C.P. Karger. [Extracted from the article]

Purpose/objective(s): Despite being a principal research interest, feasibility of raster-scanned ultra-high dose-rate particle beams remains largely unknown. Moreover, with the increasing evidence of potential normal tissue sparing with uHDR delivery, there is an urgent need for comprehensive assessments of facility-specific delivery capacity and characteristics to ultimately drive forward radiobiological investigations of the FLASH effect and subsequent modeling. This work aims to establish and assess the range and limits of uHDR delivery for raster-scanned particle therapy at a synchrotron-based facility for "light" (p, He) and "heavy" (C, O) ion beams.Materials/methods: For p, He, C and O ions, different settings of the synchrotron are tested to assess the linearity window for clinically ideal spill characteristics at FLASH dose levels and dose-rates. For instance, different parameters require modification and/or monitoring for each delivery scenario, e.g., monitor chamber current, delivery time, field size, the number of scanned spot positions, the number of particles and thus the achievable dose level. The dose can be assessed in two particular positions, either the entrance channel of a pristine peak or within a spread-out Bragg peak using a range modulator. Limitations in dose level and dose-rate were investigated within the entrance channel where, conceptually, normal tissues reside within the irradiation field. In addition, the influences of the field size and number of scanned-spots on spatially dependent dose-time structure and delivery time are investigated.Results: For the entrance channel, parameters which primarily impact dose delivery characteristics were both the number of particles to be delivered within a single spill by the synchrotron and the requested beam intensities. Parameter settings influence delivery characteristics differently for "light" and "heavy" particles: for "light ions" maximizing a number of particles per spill to FLASH dose levels can be limited while for "heavy" ions, extraction intensity is the main obstacle in achieving FLASH dose-rates. Characterized for the four ions, the dose-time evolution is spatially dependent and varies with the number of spots and scanning patterns.Conclusion: In parallel with mean delivery time and mean dose-rate measured live via monitoring systems, temporal delivery aspects of in-field dose distributions can be assessed and verified (experimentally or in-silico) for active beam delivery that could complement further bio-modelling. The results of this work make evident the importance of a proper assessment of dosimetry and delivery characteristics prior to biological experimentation, as demonstrated at our synchrotron-based facility where delivery parameters may fluctuate between treatment sessions. [ABSTRACT FROM AUTHOR]

In the direct vicinity of plasma-facing surfaces, the incident plasma particles interact with surface-recombined neutrals. Remarkably high near-surface plasma pressure losses were observed in the high-flux linear plasma generator Magnum-PSI. Combining the incoherent and coherent Thomson scattering diagnostics, we directly measured particle, momentum and energy fluxes down to 3 mm from the plasma target surface. At the surface, the particle and total heat flux were also measured, using respectively an in-target Langmuir probe and thermographic methods. The near-surface momentum and energy losses scale with density, and amount to at least 50% and 20%, respectively, at ne = 8 × 1020 m−3. These losses are attributed to the efficient exchange of charge, momentum and energy between incident plasma and surface-recombined neutrals. In low-temperature plasmas with sufficient density, incident particles go through several cycles of interaction and surface deposition before leaving the plasma, thereby providing an effective alternative dissipation channel to the incident plasma. Parallel plasma parameter profiles exhibit a transition with increasing plasma density. In low-density conditions, the plasma temperature is constant and near-surface ion acceleration is observed, attributed to the ambipolar electric field. Conversely, deceleration and plasma cooling are observed in dense conditions. These results are explained by the combined effect of ion–neutral friction and electron–ion thermal equilibration in the so-called thermalized collisional pre-sheath. The energy available for ambipolar acceleration is thus reduced, as well as the upstream flow velocity. In the ITER divertor, enhanced near-surface p–n interaction is expected as well, given the overlap in plasma conditions. Including these effects in finite-element scrape-off layer models requires a near-surface resolution smaller than the neutral mean free path. This amounts to 1 mm in Magnum-PSI, and possibly an order of magnitude smaller in ITER. [ABSTRACT FROM AUTHOR]

Quality assurance in magnetic resonance (MR)-guided radiotherapy lacks anthropomorphic phantoms that represent tissue-equivalent imaging contrast in both computed tomography (CT) and MR imaging. In this study, we developed phantom materials with individually adjustable CT value as well as - and -relaxation times in MR imaging at three different magnetic field strengths. Additionally, their experimental stopping power ratio (SPR) for carbon ions was compared with predictions based on single- and dual-energy CT. Ni-DTPA doped agarose gels were used for individual adjustment of and at and 3.0 T. The CT value was varied by adding potassium chloride (KCl). By multiple linear regression, equations for the determination of agarose, Ni-DTPA and KCl concentrations for given and CT values were derived and employed to produce nine specific soft tissue samples. Experimental and CT values of these soft tissue samples were compared with predictions and additionally, carbon ion SPR obtained by range measurements were compared with predictions based on single- and dual-energy CT. The measured CT value, and of the produced soft tissue samples agreed very well with predictions based on the derived equations with mean deviations of less than While single-energy CT overestimates the measured SPR of the soft tissue samples, the dual-energy CT-based predictions showed a mean SPR deviation of only To conclude, anthropomorphic phantom materials with independently adjustable CT values as well as and relaxation times at three different magnetic field strengths were developed. The derived equations describe the material specific relaxation times and the CT value in dependence on agarose, Ni-DTPA and KCl concentrations as well as the chemical composition of the materials based on given and CT value. Dual-energy CT allows accurate prediction of the carbon ion range in these materials. [ABSTRACT FROM AUTHOR]

The use of nanoparticles (NP) as dose enhancers in radiotherapy (RT) is a growing research field. Recently, the use of NP has been extended to charged particle therapy in order to improve the performance in radioresistant tumors. However, the biological mechanisms underlying the synergistic effects involved in NP-RT approaches are not clearly understood. Here, we used the capabilities of synchrotron-based Fourier Transform Infrared Microspectroscopy (SR-FTIRM) as a bio-analytical tool to elucidate the NP-induced cellular damage at the molecular level and at a single-cell scale. F98 glioma cells doped with AuNP and GdNP were irradiated using several types of medical ion beams (proton, helium, carbon and oxygen). Differences in cell composition were analyzed in the nucleic acids, protein and lipid spectral regions using multivariate methods (Principal Component Analysis, PCA). Several NP-induced cellular modifications were detected, such as conformational changes in secondary protein structures, intensity variations in the lipid CHx stretching bands, as well as complex DNA rearrangements following charged particle therapy irradiations. These spectral features seem to be correlated with the already shown enhancement both in the DNA damage response and in the reactive oxygen species (ROS) production by the NP, which causes cell damage in the form of protein, lipid, and/or DNA oxidations. Vibrational features were NP-dependent due to the NP heterogeneous radiosensitization capability. Our results provided new insights into the molecular changes in response to NP-based RT treatments using ion beams, and highlighted the relevance of SR-FTIRM as a useful and precise technique for assessing cell response to innovative radiotherapy approaches. [ABSTRACT FROM AUTHOR]

A new practical method to determine the ion recombination correction factor (ks) for plane-parallel and Farmer-type cylindrical chambers in particle beams is investigated. Experimental data were acquired in passively scattered and scanned particle beams and compared with theoretical models developed by Boag and/or Jaffé. The new method, named the three-voltage linear method (3VL-method), is simple and consists of determining the saturation current using the current measured at three voltages in a linear region and dividing it by the current at the operating voltage (V) (even if it is not in the linear region) to obtain ks. For plane-parallel chambers, comparing ks-values obtained by model fits to values obtained using the 3VL-method, an excellent agreement is found. For cylindrical chambers, recombination is due to volume recombination only. At low voltages, volume recombination is too large and Boag's models are not applicable. However, for Farmer-type chambers (NE2571), using a smaller voltage range, limited down to 100 V, we observe a linear variation of ks with 1/V2 or 1/V for continuous or pulsed beams, respectively. This linearity trend allows applying the 3VL-method to determine ks at any polarizing voltage. For the particle beams used, the 3VL-method gives an accurate determination of ks at any polarizing voltage. The choice of the three voltages must to be done with care to ensure to be in a linear region. For Roos-type or Markus-type chambers (i.e. chambers with an electrode spacing of 2 mm) and NE2571 chambers, the use of the 3VL-method with 300 V, 200 V and 150 V is adequate. A difference with the 2V-method and some 3V-methods in the literature is that in the 3VL-method the operational voltage does not have to be one of the three voltages. An advantage over a 2V-method is that the 3VL-method can inherently verify if the linearity condition is fulfilled. [ABSTRACT FROM AUTHOR]

• The Magnum-PSI facility is available for plasma-material interaction studies. • Magnum-PSI is capable to reach relevant plasma parameters for the ITER divertor. • Particle fluxes over 1025 m−2s−1 and heat fluxes of up to 50 MW m−2 are obtained. • Particle fluences of up to 1030 particles m−2 have been achieved. • Linear regression and artificial neural network analysis have been applied. The Magnum-PSI facility is unique in its ability to produce and even exceed the heat and particle fluxes expected in the divertor of a fusion reactor, combined with good access to the plasma-material interaction region for diagnostics and relatively easy sample manipulation. In addition, it is possible to study the effects of transient heat loads on a plasma-facing surface, similar to those expected during so called Edge Localized Modes. By virtue of a newly installed superconducting magnet, Magnum-PSI can now maintain these conditions for hours on end for truly long term tests of candidate plasma facing materials. The electron density and temperature in the plasma beam center as a function of different magnetic fields up to 1.6 T, gas flow and source current are determined: particle fluxes greater than 1025 m−2s−1 and heat fluxes of up to 50 MW m−2 are obtained. Linear regression and artificial neural network analysis have been used to gain insight in the general behavior of plasma conditions as a function of these machine settings. The plasma conditions during transient plasma heat loading have also been determined. These capabilities are now being exploited to reach fluence of up to 1030 particles m−2 at ITER-relevant conditions, equivalent to a significant fraction of the divertor service lifetime for the first time. [ABSTRACT FROM AUTHOR]

Background: The implementation of magnetic resonance imaging (MRI) guided radiotherapy (RT) continues to increase. Very limited in-vitro data on the interaction of ionizing radiation and magnetic fields (MF) have been published. In these experiments we focused on the radiation response in a MF of the TK6 human lymphoblastoid cells which are known to be highly radiosensitive due to efficient radiation-induced apoptosis.Methods: Clonogenicity was determined 12-14 days after irradiation with 1-4 Gy 6 MV photons with or without a 1.0 Tesla MF. Furthermore, alterations in cell cycle distribution and rates of radiation induced apoptosis (FACS analysis of cells with sub-G1 DNA content) were analyzed.Results: Clonogenic survival showed an exponential dose-dependence, and the radiation sensitivity parameter (α = 1.57/Gy) was in accordance with earlier reports. Upon comparing the clonogenic survival between the two groups, identical results within error bars were obtained. The survival fractions at 2 Gy were 9% (without MF) and 8.5% (with MF), respectively.Conclusion: A 1.0 Tesla MF does not affect the clonogenicity of TK6 cells irradiated with 1-4 Gy 6MV photons. This supports the use of MRI guided RT, however ongoing research on the interaction of MF and radiotherapy is warranted. [ABSTRACT FROM AUTHOR]

Highlights • The 2.5 T superconducting high flux plasma generator Magnum-PSI is presented. • The operational status of Magnum-PSI is presented. • ITER divertor relevant steady state heat flux (>10 MW m−2) has been achieved. • First high fluence (>2 × 1028 m−2) plasma exposure experiments have been performed. • Magnum-PSI has been commissioned for magnetic fields up to 1.6 T. Abstract The interaction of intense plasma impacting on the wall of a fusion reactor is an area of high and increasing importance in the development of electricity production from nuclear fusion. In the Magnum-PSI linear device, an axial magnetic field confines a high density, low temperature plasma produced by a wall stabilized DC cascaded arc into an intense magnetized plasma beam directed onto a target. The experiment has shown its capability to reach conditions that enable fundamental studies of plasma-surface interactions in the regime relevant for fusion reactors such as ITER: 1023–1025 m−2s−1 hydrogen plasma flux densities at 1–5 eV for tens of seconds by using conventional electromagnets. Recently the machine was upgraded with a superconducting magnet, enabling steady-state magnetic fields up to 2.5 T, expanding the operational space to high fluence capabilities for the first time. Also the diagnostic suite has been expanded by a new 4-channel resistive bolometer array and ion beam analysis techniques for surface analysis after plasma exposure of the target. A novel collective Thomson scattering system has been developed and will be implemented on Magnum-PSI. In this contribution, the current status, capabilities and performance of Magnum-PSI are presented. [ABSTRACT FROM AUTHOR]

The Heidelberg Ion-Beam Therapy Centre's synchrotron makes use of the well established slow extraction RF KO method near the third-order resonance. The spill quality is essential for therapy, since the reproducibility and fidelity in the parameters of the extracted beam translate in a reduction of irradiation time. The horizontal beam response was studied experimentally and with simulations at extraction conditions in order to deduce regions of interest for an optimal excitation signal spectrum. Two narrow frequency regions were found near the betatron resonance. With these results a new signal was engineered for the emittance blow-up scheme. The new excitation signal improves significantly the spill quality for the extraction configurations; for instance the lower interquartile value of the spill duty factor distribution for the most rigid carbon-ion beam E kin = 430 MeV/u improves from 82.2% to 94.8%. For the proton beam the improvement is more significant, where the spill duty factor is kept over the 90% level. [ABSTRACT FROM AUTHOR]

Purpose/objective(s): To establish and investigate the impact of LET and O2 concentration on biological response to ultra-high dose-rate (uHDR, FLASH) helium ion beams compared to standard dose-rate (SDR) irradiation.Materials/methods: Beam delivery settings for raster-scanned helium ions at both uHDR and SDR were tuned to achieve > 100 Gy/s and 0.15 Gy/s, respectively. For both SDR and uHDR, 8 Gy and 12 Gy plan optimization and calibration for 10 × 10mm2 fields was performed to assess in vitro response at lower LET (4.5 keV/μm) and higher LET (16 keV/μm) conditions. Clonogenic assay and DNA damage response (γH2AX) of human lung epithelial cancer cells A549 cells were used as biological indicators for the cellular response to uHDR and SDR irradiation for specified oxygen concentrations levels (1%, 21%).Results: Average dose-rates for both lower and higher LET were 193 Gy/s and 0.15 Gy/s for uHDR and SDR, respectively. Cell survival was higher and γH2AX, a surrogate for DNA damage response, was lower for cells irradiated with uHDR as compared to SDR at 1% O2 for both dose and LET levels. This difference in cellular response was not seen at 21% O2 where cell survival and DNA damage response were unchanged at studied dose-rates.Conclusion: The first uHDR delivery of raster-scanned particle beams was achieved using helium ions, reaching FLASH-level dose-rates of > 100 Gy/s. Baseline oxygen levels play a pivotal role, irrespective of investigated LET, for observation of a sparing effect for helium ions. [ABSTRACT FROM AUTHOR]

In Magnum-PSI (MAgnetized plasma Generator and NUMerical modeling for Plasma Surface Interactions), the high density, low temperature plasma of a wall stabilized dc cascaded arc is confined to a magnetized plasma beam by a quasi-steady state axial magnetic field up to 1.3 T. It aims at conditions that enable fundamental studies of plasma–surface interactions in the regime relevant for fusion reactors such as ITER: 10 23 –10 25 m −2 s −1 hydrogen plasma flux densities at 1–5 eV. To study the effects of transient heat loads on a plasma-facing surface, a high power pulsed magnetized arc discharge has been developed. Additionally, the target surface can be transiently heated with a pulsed laser system during plasma exposure. In this contribution, the current status, capabilities and performance of Magnum-PSI are presented. [ABSTRACT FROM AUTHOR]

Abstract: New linear plasma devices are currently being constructed or planned in the Trilateral Euregio Cluster (TEC) to meet the challenges with respect to plasma surface interactions in DEMO and ITER: i) MAGNUM-PSI (FOM), a high particle and power flux device with super-conducting magnetic field coils which will reach ITER-like divertor conditions at high magnetic field, ii) the newly proposed linear plasma device JULE-PSI (FZJ), which will allow to expose toxic and neutron activated target samples to ITER-like fluences and ion energies including in vacuo analysis of neutron activated samples, and iii) the plasmatron VISION I, a compact plasma device which will be operated inside the tritium lab at SCK-CEN Mol, capable to investigate tritium plasmas and moderately activated wall materials. This contribution shows the capabilities of the new devices and their forerunner experiments (Pilot-PSI at FOM and PSI-2 Jülich at FZJ) in view of the main objectives of the new TEC program on plasma surface interactions. [Copyright &y& Elsevier]

Abstract: Magnum-PSI is a linear plasma generator, built at the FOM-Institute for Plasma Physics Rijnhuizen. Subject of study will be the interaction of plasma with a diversity of surface materials. The machine is designed to provide an environment with a steady state high-flux plasma (up to 1024 H+ ions/m2 s) in a 3T magnetic field with an exposed surface of 80cm2 up to 10MW/m2. Magnum-PSI will provide new insights in the complex physics and chemistry that will occur in the divertor region of the future experimental fusion reactor ITER and reactors beyond ITER. The conditions at the surface of the sample can be varied over a wide range, such as plasma temperature, beam diameter, particle flux, inclination angle of the target, background pressure and magnetic field. An important subject of attention in the design of the machine was thermal effects originating in the excess heat and gas flow from the plasma source and radiation from the target. [Copyright &y& Elsevier]

Abstract: At FOM Rijnhuizen, linear plasma generators are used to investigate plasma-material interactions under high-density (⩽1021 m−3), low-temperature (⩽5eV) plasma bombardment. Research into carbon-based materials has been focused on chemical erosion by hydrogen plasmas. Results from plasma exposure to high-flux (>1023 H+/m2 s) and low-temperature hydrogen plasma indicate silicon carbide has a lower relative rate of gross erosion than other carbon-based materials (e.g. graphite, diamond, carbon-fiber composites) by a factor of 7–10. Hydrogenic retention is the focus of research on tungsten and molybdenum. For target temperatures of 700–1600K, the temperature dependence of hydrogenic retention is the dominant factor. Damage to the surface by heavy ion irradiation has shown to enhance retention by a factor of 2.5–4.1. Thermal stressing of W via. e-beam thermal cycling also enhances hydrogenic retention by a factor of 2.1±0.2, likely due to the introduction of thermal defects, which act as trapping sites for implanted hydrogenic isotopes. [Copyright &y& Elsevier]

Abstract: The FOM-Institute for Plasma Physics Rijnhuizen is constructing Magnum-PSI; a magnetized (3T), steady-state, large area (80cm2) high-flux (up to H+ ions m−2 s−1) plasma generator. Magnum-PSI will be a highly accessible laboratory experiment in which the interaction of magnetized plasma with different surfaces can be studied. This experiment will provide new insights in the complex physics and chemistry that will occur in the divertor region of the future experimental fusion reactor ITER. Here, extremely high power and particle flux densities are predicted at relatively low plasma temperatures. Magnum-PSI will be able to simulate these detached ITER divertor conditions in detail. In addition, conditions can be varied over a wide range, such as different target materials, plasma temperatures, beam diameters, particle fluxes, inclination angles of target, background pressures, magnetic fields, etc., making Magnum-PSI an excellent test bed for high heat flux components of future fusion reactors. The design phase of the Magnum-PSI device has been completed. The construction and assembly phase of the device is in progress. In this contribution, we will present the design and construction of the Magnum-PSI experiment. The status of the vacuum system, the 3T superconducting magnet, the plasma source, the target plate and manipulator, and additional plasma heating will be presented. The plasma and surface diagnostics that will be used in the Magnum-PSI experiment will be introduced. [ABSTRACT FROM AUTHOR]

Abstract: The FOM-Institute for Plasma Physics Rijnhuizen is preparing the construction of Magnum-PSI, a magnetized (3T), steady state, large area (80cm2) high-flux (up to 1024 H+ ionsm−2 s−1) plasma generator. The aim of the linear plasma device Magnum-PSI is to provide a controlled, highly accessible laboratory experiment in which the interaction of a magnetized plasma with different surfaces can be studied in detail. Plasma parameters can be varied over a wide range, in particular covering the high-density, low-temperature conditions expected for the detached divertor plasma of ITER. The target set-up will be extremely flexible allowing the investigation of different materials under a large variety of conditions (temperatures, inclination, biasing, coatings, etc.). A range of target materials will be used, including carbon, tungsten and other metals, and mixed materials. Because of the large plasma beam of 10cm diameter and spacious vacuum tank, even the test of whole plasma-facing component mock-ups will be possible. In this article, we will present the pre-design of the Magnum-PSI experiment. We will focus on the requirements of the vacuum system and the 3T superconducting magnet. We briefly introduce some of the other sub-systems on Magnum-PSI such as the target and target manipulator. [Copyright &y& Elsevier]

Abstract: The superconducting magnet system of the Wendelstein 7-X stellarator produces magnetic field up to 3T at the plasma axis. The system consists of five identical modules, each including ten non-planar and four planar coils as well as a 72° sector of the central supporting ring. The superconducting busbar lines feeding the coils (bus current is up to 18kA) are routed in a similar way for each module except for the current lead lines and separation planes between adjacent modules. The coils’ modular system allows the design, study and manufacture of the busbar lines independently for each module. The electromagnetic forces experienced by the busbars are taken by the supporting system. The paper presents the current design of the system for the fifth module, main results of the stress analysis and tests. [Copyright &y& Elsevier]

Abstract: In the framework of cooperation between the Max-Planck-Institute for Plasma Physics (IPP) essential work packages of the superconducting stellarator Wendelstein 7-X (which is presently under construction at Greifswald, Germany) have been taken over by the Forschungszentrum Jülich (FZJ). One of these packages is the design, construction and manufacturing of the superconducting three-dimensional coil interconnections (the so called bus system) and its appropriate supports. Key task was the development and qualification of an appropriate insulation fulfilling not only the electrical requirements but also withstanding all mechanical stresses during operation. An overall concept of the project was elaborated with the goal to optimize working steps and to simplify the system assembly. In order to compensate the magnetic stray fields generated by the bus currents an appropriate bus topology was developed. No collisions with other parts, reduced space for integration and easy transportation were provided (Fig. 1). [Copyright &y& Elsevier]

We report on the observation of a KSp resonance signal at a mass of 1765 ± 5 MeV/ c 2, with intrinsic width Γ = 108 ± 22 MeV/ c 2, produced inclusively in Σ--nucleus interactions at 340 GeV/ c in the hyperon beam experiment WA89 at CERN. The signal was observed in the kinematic region xF>0.7, in this region its production cross section rises approximately linearly with (1-xF), reaching BR(X→KSp)dσ/dxF=(5.2±2.3)μb per nucleon at xF=0.8. The hard xF spectrum suggests the presence of a strong leading particle effect in the production and hence the identification as a Σ*+ state. No corresponding peaks were observed in the K-p and Λπ± mass spectra. [ABSTRACT FROM AUTHOR]

Proffered Papers: Proffered papers 34: Particle therapy in CNS tumours OC-0687: RBE-dependence on LET and fractionation in the rat cervical spinal cord after oxygen ion irradiation L. Hintz, M. Saager, P. Peschke, S. Brons, J. Debus, C. Glowa, C.P. Karger. [Extracted from the article]

A new flexible antenna system has been designed for TEXTOR which can be operated in the “conjugated T” mode. This mode of operation foreseen for the new JET-EP antenna is characterised by its insensitivity to the variations of the antenna plasma loading resistance. By optimising the “conjugated T” mode, a VSWR at the generator lower than 1.1 can be maintained for an antenna distributed loading resistance varying between 2.5 and 9.5 Ohm/m (or <1.5 between 0.8 and 16 Ohm/m). [Copyright &y& Elsevier]

Particle computed tomography (pCT) is an emerging imaging modality that promises to reduce range uncertainty in particle therapy. The Bergen pCT collaboration aims to develop a novel pCT prototype based on the ALPIDE monolithic CMOS sensor. The planned prototype consist of two tracking planes forming a rear tracker and Digital Tracking Calorimeter (DTC). The DTC will be made of a 41 layer ALPIDE-aluminum sandwich structure. To enable data acquisition at clinical particle rates, a large multiplicity of particles will be measured using the highly-granular ALPIDE sensor. In this work, a first characterization of the ALPIDE sensor performance in ion beams is conducted. Particle hits in the ALPIDE sensor result in charge clusters whose size is related to the chip response and the particle energy deposit. Firstly, measurements in a 10 MeV 4 He micro beam have been conducted at the SIRIUS microprobe facility of ANSTO to investigate the dependence of the cluster size on the beam position over the ALPIDE pixel. Here, a variation in cluster size depending on the impinging point of the beam was observed. Additional beam tests were conducted at the Heidelberg Ion-Beam Therapy Center (HIT) investigating the cluster size as a function of the deposited energy by protons and 4 He ions in the sensitive volume of the ALPIDE. Results show the expected increase in cluster sizes with deposited energy and a clear difference in cluster sizes for protons and 4 He ions. As a conclusion, the variation in cluster size with the impinging point of the beam has to be accounted for to enable accurate energy loss reconstruction with the ALPIDE. This does, however, not affect the tracking of particles through the final prototype, as for that only the center-of-mass of the cluster is relevant. [ABSTRACT FROM AUTHOR]

Background: The role of radiolytic oxygen consumption for the in-vitro "Ultra-High Dose Rate" (UHDR) sparing and in-vivo FLASH effect is subject to active debate, but data on key dependencies such as the radiation quality are lacking., Purpose: The influence of "dose-averaged Linear Energy Transfer" (LETd) and dose rate on radiolytic oxygen consumption was investigated by monitoring the oxygen concentration during irradiation with electrons, protons, helium, carbon, and oxygen ions at UHDR and "Standard Dose Rates" (SDR)., Methods: Sealed "Bovine Serum Albumin" (BSA) 5% samples were exposed to 15 Gy of electrons and protons, and for the first time helium, carbon, and oxygen ions with LETd values of 1, 5.4, 14.4, 65, and 100.3 keV/µm, respectively, delivered at mean dose rates of either 0.3-0.4 Gy/s for SDR or approximately 100 Gy/s for UHDR. The Oxylite (Oxford Optronics) system allowed measurements of the oxygen concentration before and after irradiation to calculate the oxygen consumption rate., Results: The oxygen consumption rate was found to decrease with increasing LETd from 0.351 mmHg/Gy for low LET electrons to 0.1796 mmHg/Gy for high LET oxygen ions at SDR and for UHDR from 0.317 to 0.1556 mmHg/Gy, respectively. A higher consumption rate for SDR irradiation compared to the corresponding UHDR irradiation persisted for all particle types., Conclusion: The measured consumption rates demonstrate a distinct LETd dependence. The obtained dataset, encompassing a wide range of LETd values, could serve as a benchmark for Monte Carlo simulations, which may aid in enhancing our comprehension of oxygen-related mechanisms after irradiations. Ultimately, they could help assess the viability of different hypotheses regarding UHDR sparing mechanisms and the FLASH effect. The found LETd dependence underscores the potential of heavy ion therapy, wherein elevated consumption rates in adjacent normal tissue offer protective benefits, while leaving tumor regions with generally higher "Linear Energy Transfer" (LET) vulnerable., (© 2024 The Author(s). Medical Physics published by Wiley Periodicals LLC on behalf of American Association of Physicists in Medicine.)

Purpose: Hypoxia in tumors is associated with increased malignancy and resistance to conventional photon radiation therapy. This study investigated the potential of particle therapy to counteract radioresistance in syngeneic rat prostate carcinoma., Methods and Materials: Subcutaneously transplanted R3327-HI tumors were irradiated with photons or carbon ions under acute hypoxic conditions, induced by clamping the tumor-supplying artery 10 min before and during irradiation. Dose-response curves were determined for the endpoint "local tumor control within 300 days" and compared with previously published data acquired under oxic conditions. Doses at 50% tumor control probability (TCD 50 ) were used to quantify hypoxia-induced radioresistance relative to that under oxic conditions and also to quantify the increased effectiveness of carbon ions under oxic and hypoxic conditions relative to photons., Results: Compared with those under oxic conditions, TCD 50 values under hypoxic conditions increased by a factor of 1.53 ± 0.08 for photons and by a factor of 1.28 ± 0.06 for carbon ions (oxygen enhancement ratio). Compared with those for photons, TCD 50 values for carbon ions decreased by a factor of 2.08 ± 0.13 under oxic conditions and by a factor of 2.49 ± 0.08 under hypoxic conditions (relative biological effectiveness). While the slope of the photon dose-response curves increased when changing from oxic to hypoxic conditions, the slopes were steeper and remained unchanged for carbon ions., Conclusions: The reduced oxygen enhancement ratio of carbon ions indicated that the required dose increase in hypoxic tumors was 17% lower for carbon ions than for photons. Additionally, carbon ions reduced the effect of intertumor heterogeneity on the radiation response. Therefore, carbon ions may confer a significant advantage for the treatment of hypoxic tumors that are highly resistant to conventional photon radiation therapy., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)