22 research outputs found
Characterization of relativistic electron bunch duration and travelling wave structure phase velocity based on momentum spectra measurements on the ARES linac at DESY
The ARES linac at DESY aims to generate and characterize ultrashort electron
bunches (fs to sub-fs duration) with high momentum and arrival time stability
for the purpose of applications related to accelerator R&D, e.g. development of
advanced and compact diagnostics and accelerating structures, test of new
accelerator components, medical applications studies, machine learning, etc.
During its commissioning phase, the bunch duration characterization of the
electron bunches generated at ARES has been performed with an RF-phasing
technique relying on momentum spectra measurements, using only common
accelerator elements (RF accelerating structures and magnetic spectrometers).
The sensitivity of the method allowed highlighting different response times for
Mo and Cs2Te cathodes. The measured electron bunch duration in a wide range of
machine parameters shows excellent agreement overall with the simulation
predictions, thus demonstrating a very good understanding of the ARES operation
on the bunch duration aspect. The importance of a precise in-situ experimental
determination of the phase velocity of the first travelling wave accelerating
structure after the electron source, for which we propose a simple new
beam-based method precise down to sub-permille variation respective to the
speed of light in vacuum, is emphasized for this purpose. A minimum bunch
duration of 20 fs rms, resolution-limited by the space charge forces, is
reported. This is, to the best of our knowledge, around 4 times shorter than
what has been previously experimentally demonstrated based on RF-phasing
techniques with a single RF structure. The present study constitutes a strong
basis for future time characterization down to the sub-fs level at ARES, using
dedicated X-band transverse deflecting structures.Comment: 17 pages, 11 figures. To be submitted to Physical Review Accelerators
and Beam
Status and Objectives of the Dedicated Accelerator R&D Facility "SINBAD" at DESY
We present a status update on the dedicated R\&D facility SINBAD which is
currently under construction at DESY. The facility will host multiple
independent experiments on the acceleration of ultra-short electron bunches and
novel, high gradient acceleration methods. The first experiment is the
ARES-experiment with a normal conducting 100\,MeV S-band linac at its core. We
present the objectives of this experiment ranging from the study of compression
techniques to sub-fs level to its application as injector for various advanced
acceleration schemes e.g. the plans to use ARES as a test-site for DLA
experiments in the context of the ACHIP collaboration. The time-line including
the planned extension with laser driven plasma-wakefield acceleration is
presented. The second initial experiment is AXSIS which aims to accelerate
fs-electron bunches to 15\,MeV in a THz driven dielectric structure and
subsequently create X-rays by inverse Compton scattering.Comment: EAAC'17 conference proceeding
Elite Influence? Religion, Economics, and the Rise of the Nazis
Adolf Hitler's seizure of power was one of the most consequential events of the twentieth century. Yet, our understanding of which factors fueled the astonishing rise of the Nazis remains highly incomplete. This paper shows that religion played an important role in the Nazi party's electoral success -- dwarfing all available socioeconomic variables. To obtain the first causal estimates we exploit plausibly exogenous variation in the geographic distribution of Catholics and Protestants due to a peace treaty in the sixteenth century. Even after allowing for sizeable violations of the exclusion restriction, the evidence indicates that Catholics were significantly less likely to vote for the Nazi Party than Protestants. Consistent with the historical record, our results are most naturally rationalized by a model in which the Catholic Church leaned on believers to vote for the democratic Zentrum Party, whereas the Protestant Church remained politically neutral
Simulation of Deflecting Structures for Dielectric Laser Driven Accelerators
In laser illuminated dielectric accelerators (DLA) high acceleration gradients can be achieved, due to high damage thresholds of the materials at optical frequencies. This is a necessity in developing more compact particle accelerator technologies. The Accelerator on a CHip International Program funded by the Gordon and Betty Moore Foundation is researching such devices. Means to manipulate the beam, i.e. focusing and deflection, are needed for the proper operation of such devices. These means should rely on the same technologies for manufacturing and powering like the accelerating structures. In this study different concepts for dielectric laser driven deflecting structures are investigated via particle-in-cell (PIC) simulations and compared afterwards. The comparison is conducted with respect to the suitability for beam manipulation. Another interesting applicationwill be investigated as a diagnostic device for ultra short electron bunches from conventional accelerators functioning like a radio frequency transverse deflecting cavity (TDS)
Parameter Studies on Dielectric Gratings as Electron Accelerators
Dielectric laser driven particle acceleration (DLA) is one of the candidates for novel high-gradient technologies to reduce the footprint of large scale particle acceleration facilities. On the other hand these devices can be used to interact with the particle beams of state-of-the-art photon science machines, especially with FELs, to manipulate the longitudinal phase space in a compact and cost effective way. The near-field surface modes of dielectric gratings can be used to interact with particle beams close to the surface. To achieve transversely homogeneous accelerating fields two gratings are opposed. The laser can be coupled from the side into the structure. In this work we present a study on the influence of the geometry parameters of the grating on the acceleration gradient and its transverse uniformity. Based on this study a design for production was chosen, which will be used for experiments at the ARES linac within the SINBAD facility at DESY. This work was carried out within the ACHIP project funded by the Gordon and Betty Moore Foundation (GBMF 4744)
Predicting the transverse emittance of space charge dominated beams using the phase advance scan technique and a fully connected neural network
The transverse emittance of a charged particle beam is an important figure of
merit for many accelerator applications, such as ultra-fast electron
diffraction, free electron lasers and the operation of new compact accelerator
concepts in general. One of the easiest to implement methods to determine the
transverse emittance is the phase advance scan method using a focusing element
and a screen. This method has been shown to work well in the thermal regime. In
the space charge dominated laminar flow regime, however, the scheme becomes
difficult to apply, because of the lack of a closed description of the beam
envelope including space charge effects. Furthermore, certain mathematical, as
well as beamline design criteria must be met in order to ensure accurate
results. In this work we show that it is possible to analyze phase advance scan
data using a fully connected neural network (FCNN), even in setups, which do
not meet these criteria. In a simulation study, we evaluate the perfomance of
the FCNN by comparing it to a traditional fit routine, based on the beam
envelope equation. Subsequently, we use a pre-trained FCNN to evaluate measured
phase advance scan data, which ultimately yields much better agreement with
numerical simulations. To tackle the confirmation bias problem, we employ
additional mask-based emittance measurement techniques
Myocarditis in newborn wild-type BALB/c mice infected with the murine gamma herpesvirus MHV-68
Characterization of relativistic electron bunch duration and travelling wave structure phase velocity based on momentum spectra measurements on the ARES linac at DESY
International audienceThe ARES linac at DESY aims to generate and characterize ultrashort electron bunches (fs to sub-fs duration) with high momentum and arrival time stability for the purpose of applications related to accelerator R&D, e.g. development of advanced and compact diagnostics and accelerating structures, test of new accelerator components, medical applications studies, machine learning, etc. During its commissioning phase, the bunch duration characterization of the electron bunches generated at ARES has been performed with an RF-phasing technique relying on momentum spectra measurements, using only common accelerator elements (RF accelerating structures and magnetic spectrometers). The sensitivity of the method allowed highlighting different response times for Mo and Cs2Te cathodes. The measured electron bunch duration in a wide range of machine parameters shows excellent agreement overall with the simulation predictions, thus demonstrating a very good understanding of the ARES operation on the bunch duration aspect. The importance of a precise in-situ experimental determination of the phase velocity of the first travelling wave accelerating structure after the electron source, for which we propose a simple new beam-based method precise down to sub-permille variation respective to the speed of light in vacuum, is emphasized for this purpose. A minimum bunch duration of 20 fs rms, resolution-limited by the space charge forces, is reported. This is, to the best of our knowledge, around 4 times shorter than what has been previously experimentally demonstrated based on RF-phasing techniques with a single RF structure. The present study constitutes a strong basis for future time characterization down to the sub-fs level at ARES, using dedicated X-band transverse deflecting structures