78 research outputs found
Demonstration of the synchrotron-type spectrum of laser-produced Betatron radiation
Betatron X-ray radiation in laser-plasma accelerators is produced when
electrons are accelerated and wiggled in the laser-wakefield cavity. This
femtosecond source, producing intense X-ray beams in the multi kiloelectronvolt
range has been observed at different interaction regime using high power laser
from 10 to 100 TW. However, none of the spectral measurement performed were at
sufficient resolution, bandwidth and signal to noise ratio to precisely
determine the shape of spectra with a single laser shot in order to avoid shot
to shot fluctuations. In this letter, the Betatron radiation produced using a
80 TW laser is characterized by using a single photon counting method. We
measure in single shot spectra from 8 to 21 keV with a resolution better than
350 eV. The results obtained are in excellent agreement with theoretical
predictions and demonstrate the synchrotron type nature of this radiation
mechanism. The critical energy is found to be Ec = 5.6 \pm 1 keV for our
experimental conditions. In addition, the features of the source at this energy
range open novel perspectives for applications in time-resolved X-ray science.Comment: 5 pages, 4 figure
Spatiotemporal dynamics of ultrarelativistic beam-plasma instabilities
An electron or electron-positron beam streaming through a plasma is
notoriously prone to micro-instabilities. For a dilute ultrarelativistic
infinite beam, the dominant instability is a mixed mode between longitudinal
two-stream and transverse filamentation modes, with a phase velocity oblique to
the beam velocity. A spatiotemporal theory describing the linear growth of this
oblique mixed instability is proposed, which predicts that spatiotemporal
effects generally prevail for finite-length beams, leading to a significantly
slower instability evolution than in the usually assumed purely temporal
regime. These results are accurately supported by particle-in-cell (PIC)
simulations. Furthermore, we show that the self-focusing dynamics caused by the
plasma wakefields driven by finite-width beams can compete with the oblique
instability. Analyzed through PIC simulations, the interplay of these two
processes in realistic systems bears important implications for upcoming
accelerator experiments on ultrarelativistic beam-plasma interactions
Synchrotron radiation-based experimental determination of the optimal energy for cell radiotoxicity enhancement following photoelectric effect on stable iodinated compounds
This study was designed to experimentally evaluate the optimal X-ray energy for increasing the radiation energy absorbed in tumours loaded with iodinated compounds, using the photoelectric effect. SQ20B human cells were irradiated with synchrotron monochromatic beam tuned at 32.8, 33.5, 50 and 70 keV. Two cell treatments were compared to the control: cells suspended in 10 mg ml1 of iodine radiological contrast agent or cells pre-exposed with 10 mM of iodo-desoxyuridine (IUdR) for 48 h. Our radiobiological end point was clonogenic cell survival. Cells irradiated with both iodine compounds exhibited a radiation sensitisation enhancement. Moreover, it was energy dependent, with a maximum at 50 keV. At this energy, the sensitisation calculated at 10% survival was equal to 2.03 for cells suspended in iodinated contrast agent and 2.60 for IUdR. Cells pretreated with IUdR had higher sensitisation factors over the energy range than for those suspended in iodine contrast agent. Also, their survival curves presented no shoulder, suggesting complex lethal damages from Auger electrons. Our results confirm the existence of the 50 keV energy optimum for a binary therapeutic irradiation based on the presence of stable iodine in tumours and an external irradiation. Monochromatic synchrotron radiotherapy concept is hence proposed for increasing the differential effect between healthy and cancerous tissue irradiation
Stable and high quality electron beams from staged laser and plasma wakefield accelerators
We present experimental results on a plasma wakefield accelerator (PWFA) driven by high-current electron beams from a laser wakefield accelerator (LWFA). In this staged setup stable and high quality (low divergence and low energy spread) electron beams are generated at an optically-generated hydrodynamic shock in the PWFA. The energy stability of the beams produced by that arrangement in the PWFA stage is comparable to both single-stage laser accelerators and plasma wakefield accelerators driven by conventional accelerators. Simulations support that the intrinsic insensitivity of PWFAs to driver energy fluctuations can be exploited to overcome stability limitations of state-of-the-art laser wakefield accelerators when adding a PWFA stage. Furthermore, we demonstrate the generation of electron bunches with energy spread and divergence superior to single-stage LW-FAs, resulting in bunches with dense phase space and an angular-spectral charge density beyond the initial drive beam parameters. These results unambiguously show that staged LWFA-PWFA can help to tailor the electron-beam quality for certain applications and to reduce the influence of fluctuating laser drivers on the electron-beam stability. This encourages further development of this new class of staged wakefield acceleration as a viable scheme towards compact, high-quality electron beam sources
The first case of Brucella canis in Sweden: background, case report and recommendations from a northern European perspective
Infection with Brucella canis has been diagnosed in Sweden for the first time. It was diagnosed in a three-year-old breeding bitch with reproductive disturbances. Fifteen in-contact dogs were tested repeatedly and all of them were negative for B. canis. The source of infection could not be defined. The present article describes the case and the measures undertaken and gives a short review over B. canis. Recommendations on how to avoid the infection in non-endemic countries are given
European Strategy for Particle Physics -- Accelerator R&D Roadmap
The 2020 update of the European Strategy for Particle Physics emphasised the
importance of an intensified and well-coordinated programme of accelerator R&D,
supporting the design and delivery of future particle accelerators in a timely,
affordable and sustainable way. This report sets out a roadmap for European
accelerator R&D for the next five to ten years, covering five topical areas
identified in the Strategy update. The R&D objectives include: improvement of
the performance and cost-performance of magnet and radio-frequency acceleration
systems; investigations of the potential of laser / plasma acceleration and
energy-recovery linac techniques; and development of new concepts for muon
beams and muon colliders. The goal of the roadmap is to document the collective
view of the field on the next steps for the R&D programme, and to provide the
evidence base to support subsequent decisions on prioritisation, resourcing and
implementation.Comment: 270 pages, 58 figures. Editor: N. Mounet. LDG chair: D. Newbold.
Panel chairs: P. V\'edrine (HFM), S. Bousson (RF), R. Assmann (plasma), D.
Schulte (muon), M. Klein (ERL). Panel editors: B. Baudouy (HFM), L. Bottura
(HFM), S. Bousson (RF), G. Burt (RF), R. Assmann (plasma), E. Gschwendtner
(plasma), R. Ischebeck (plasma), C. Rogers (muon), D. Schulte (muon), M.
Klein (ERL
Engine Control of a Downsized Spark Ignited Engine: from Simulation to Vehicle
Tightening European standards on fuel consumption and pollutant emissions reduction lead to a sophistication of engine concepts and associated control. Since few years, downsizing (reduction of the engine displacement) appears as a major way to achieve those requirements for spark ignition engines. Efficient
performance and drivability can be then achieved with a direct injection downsized engine with turbocharging and Variable Camshaft Timing (VCT). One of the major issues of the torque-oriented control is in-cylinder mass observation and control. To have an efficient torque response, the in-cylinder trapped mass, adjusted by the throttle and the waste gate, must be controlled with accuracy according to performance and drivability requirements. Depending on admission and exhaust pressures, the twin VCT will allow to control in-cylinder burned gases rate to reduce fuel consumption and pollutant emissions, and air scavenging to improve transient speed response. Another major issue is in-cylinder trapped mass and air scavenging prediction for AFR control. In this paper, we propose a model-based approach to achieve those engine control issues. The first challenge is to design accurate observers for non-measurable variables (in-cylinder burned gases and trapped air mass). The method is based on a complex high frequency 0D engine model, which has been validated on a large range of engine operating points and transient operations based on test bed results. Then, this model permits to design and learn open-loop nonlinear static observers of in-cylinder masses (based on neural network). The static and dynamic behavior of high frequency 0D engine model allows to achieve design of dynamic and closed-loop in-cylinder mass observation and prediction, multivariable and non-linear control of air path according to in-cylinder mass trajectory (trapped air mass & recirculated gases rate). Then, the complete engine control can be developed and validated on simulation and on a real time Software-In-the-Loop platform based on high frequency 0D engine model, before a complete validation and calibration on test bed. Finally, the complete torque-oriented engine control has been integrated on vehicle. From 0D engine model, a complete vehicle model has been set on real-time platform in order to validate engine control integration and design vehicle layout. The major issue is then supervision of engine control set points (torque, AFR, efficiency) according to engine states (start, idle, driver request, cut-off) and warm-up strategies
- …