Nonlinear electrostatic emittance compensation in kA, fs electron bunches

Nonlinear space-charge effects play an important role in emittance growth in the production of kA electron bunches with a bunch length much smaller than the bunch diameter. We propose a scheme employing the radial third-order component of an electrostatic acceleration field, to fully compensate the nonlinear space-charge effects. This results in minimal transverse root-mean-square emittance. The principle is demonstrated using our design simulations of a device for the production of high-quality, high-current, subpicosecond electron bunches using electrostatic acceleration in a 1 GV/m field. Simulations using the GPT code produce a bunch of 100 pC and 73 fs full width at half maximum pulse width, resulting in a peak current of about 1.2 kA at an energy of 2 MeV. The compensation scheme reduces the root-mean-square emittance by 34% to 0.4p mm mrad

Compression of sub-relativistic space-charge-dominated electron bunches for singleshot femtosecond electron diffraction

We demonstrate the compression of 95 keV, space-charge-dominated electron bunches to sub-100 fs durations. These bunches have sufficient charge (200 fC) and are of sufficient quality to capture a diffraction pattern with a single shot, which we demonstrate by a diffraction experiment on a polycrystalline gold foil. Compression is realized by means of velocity bunching by inverting the positive space-charge-induced velocity chirp. This inversion is induced by the oscillatory longitudinal electric field of a 3 GHz radio-frequency cavity. The arrival time jitter is measured to be 80 fs

Low-loss electron beam transport in a high-power, electrostatic free-electron maser

At the FOM Institute for Plasma Physics \u27\u27Rijnhuizen\u27\u27, The Netherlands, the commissioning of a high-power, electrostatic free-electron maser is in progress. The design target is the generation of 1 MW microwave power in the frequency range 130-260 GHz. The foreseen application of this kind of device is as a power source for electron cyclotron applications on magnetically confined plasmas. The device is driven by a high-power electron beam. For long-pulse operation a low loss current is essential. A 3-A electron beam has been accelerated to energies ranging from 1.35 to 1.7 MeV and transported through the undulator at current losses below 0.02%. Further, it was shown that the beam line accepts an electron energy variation of 5% with fixed beam optics. This is essential for rapid tuning of the microwave frequency, over 10%. Electron beam simulations have shown to be remarkably accurate both for the prediction of the lens settings and for the intercepted current. The operational settings of the beam line which give the highest current transmission are within a few percent of the simulated values

Small-angle approximation in the description of radiative collective effects within an ultrarelativistic electron bunch

The problem of the evaluation of radiative collective effects accompanying accelerated motion of a short ultrarelativistic electron bunch in vacuum is considered within the framework of the small-angle approximation; second order expansion in the transverse velocity of electrons is performed in order to obtain an analytical expression for energy spread within the bunch. Comparison with earlier results by other authors shows good agreement

Laser Wakefield Acceleration in the linear and non-linear regime

No abstract

A tabletop soft X-ray source based on 5-10 MeV LINACs

We are investigating the feasibility of a novel, tabletop, high-brightness soft X-ray source

High-brightness, narrowband, compact soft x-ray Cherenkov sources in the water window

Narrowband, soft x-ray Cherenkov radiation at energies of 453 and 512 eV has been generated by 10 MeV electrons in, respectively, titanium and vanadium foils. The measured spectral and angular distribution of the radiation, and the measured total yield (10–4 photon per electron) are in agreement with theoretical predictions based on refractive index data. We show that the brightness that can be achieved using a small electron accelerator is sufficient for practical x-ray microscopy in the water-window spectral region

Theory of coherent transition radiation generated by ellipsoidal electron bunches

We present the theory of coherent transition radiation (CTR) generated by ellipsoidal electron bunches. We calculate analytical expressions for the electric field spectrum, the power spectrum, and the temporal electric field of CTR, generated by cylindrically symmetric ellipsoidal electron bunches with hard and soft edges. This theory is relevant for diagnostics of ellipsoidal electron bunches. Realization of such bunches would solve the problem of space-charge induced emittance degradation

Extreme events in the European renewable power system:Validation of a modeling framework to estimate renewable electricity production and demand from meteorological data

With the need to reduce greenhouse gas emissions, the coming decades will see a transition of Europe's power system, currently mainly based on fossil fuels towards a higher share of renewable sources. Increasing effects of fluctuations in electricity production and demand as a result of meteorological variability might cause compound events with unforeseen impacts. We constructed and validated a modeling framework to examine such extreme impact events on the European power system. This framework includes six modules: i) a reservoir hydropower inflow and ii) dispatch module; iii) a run-of-river hydropower production module; iv) a wind energy production module; v) a photovoltaic solar energy production model; and vi) an electricity demand module. Based on ERA5 reanalysis input data and present-day capacity distributions, we computed electricity production and demand for a set of European countries in the period 2015–2021 and compared results to observed data. The model captures the variability and extremes of wind, photovoltaic and run-of-river production well, with correlations between modelled and observed data for most countries of more than 0.87, 0.68 and 0.65 respectively. The hydropower dispatch module also functions well, with correlations up to 0.82, but struggles to capture reservoir inflows and operating procedures of some countries. A case study into the meteorological drivers of extreme events in Sweden and Spain showed that the meteorological conditions during extreme events selected by the model and extracted from observational data are similar, giving confidence in the application of the modeling framework for (future changes in) extreme event analysis.</p

Face and construct validity of a novel mechanical ERCP simulator

__Background__ and study aims Simulation-based training has become an important pillar in competence-based medicine. However, limited data are available on use of simulators in training for endoscopic retrograde cholangiopancreatography (ERCP). We aimed to determine the face and construct validity of the Boškoski-Costamagna mechanical ERCP Trainer, and to assess its didactic value, as judged by experts. Methods Participants were divided into four groups based on ERCP lifetime experience: novices, intermediate, experienced, and experts. Participants performed several standardized assignments on the simulator. Outcome parameters included times to complete the procedure, ability to cannulate both ducts, number of attempts to cannulate the common bile duct and pancreatic duct, number of inadvertent pancreatic duct cannulations, successful stent placement, and successful stone extraction. All experts filled out a questionnaire on the simulator’s realism and didactic value. Results Novices (n = 11) completed the total procedure in 21:09 (min:sec), intermediates (n = 5) in 10:58, experienced (n = 8) in 06:42 and experts (n = 22) in 06:05. Experts were significantly faster than novices (Kruskal-Wallis test P < 0.000). Experts rated the realism of the simulator 7.12 on a 10-point Likert scale. The simulator’s potential as a tool for training novices was rated 3.91 on a four-point Likert scale, and there was a high agreement among experts to include the simulator in the training of novice endoscopists (3.86 on a four-point Likert scale). Conclusions The novel Boškoski-Costamagna ERCP simulator demonstrates good face and construct validity. ERCP experts highly agree on the didactic value and added value of this simulator in the training curriculum for novice endoscopists