50 research outputs found
Gigahertz repetition rate thermionic electron gun concept
We present a novel concept for the generation of gigahertz repetition rate
high brightness electron bunches. A custom design 100 kV thermionic gun
provides a continuous electron beam, with the current determined by the
filament size and temperature. A 1 GHz rectangular RF cavity deflects the beam
across a knife-edge, creating a pulsed beam. Adding a higher harmonic mode to
this cavity results in a flattened magnetic field profile which increases the
duty cycle to 30%. Finally, a compression cavity induces a negative
longitudinal velocity-time chirp in a bunch, initiating ballistic compression.
Adding a higher harmonic mode to this cavity increases the linearity of this
chirp and thus decreases the final bunch length. Charged particle simulations
show that with a 0.15 mm radius LaB6 filament held at 1760 K, this method can
create 279 fs, 3.0 pC electron bunches with a radial rms core emittance of
0.089 mm mrad at a repetition rate of 1 GHz.Comment: 12 pages, 12 figure
Theory and particle tracking simulations of a resonant radiofrequency deflection cavity in TM mode for ultrafast electron microscopy
We present a theoretical description of resonant radiofrequency (RF)
deflecting cavities in TM mode as dynamic optical elements for
ultrafast electron microscopy. We first derive the optical transfer matrix of
an ideal pillbox cavity and use a Courant-Snyder formalism to calculate the 6D
phase space propagation of a Gaussian electron distribution through the cavity.
We derive closed, analytic expressions for the increase in transverse emittance
and energy spread of the electron distribution. We demonstrate that for the
special case of a beam focused in the center of the cavity, the low emittance
and low energy spread of a high quality beam can be maintained, which allows
high-repetition rate, ultrafast electron microscopy with 100 fs temporal
resolution combined with the atomic resolution of a high-end TEM. This is
confirmed by charged particle tracking simulations using a realistic cavity
geometry, including fringe fields at the cavity entrance and exit apertures
mazF, a novel counter-selectable marker for unmarked chromosomal manipulation in Bacillus subtilis
Here, we present a novel method for the directed genetic manipulation of the Bacillus subtilis chromosome free of any selection marker. Our new approach employed the Escherichia coli toxin gene mazF as a counter-selectable marker. The mazF gene was placed under the control of an isopropyl-β-d-thiogalactopyranoside (IPTG)-inducible expression system and associated with a spectomycin-resistance gene to form the MazF cassette, which was flanked by two directly-repeated (DR) sequences. A double-crossover event between the linearized delivery vector and the chromosome integrated the MazF cassette into a target locus and yielded an IPTG-sensitive strain with spectomycin-resistance, in which the wild-type chromosome copy had been replaced by the modified copy at the targeted locus. Another single-crossover event between the two DR sequences led to the excision of the MazF cassette and generated a strain with IPTG resistance, thereby realizing the desired alteration to the chromosome without introducing any unwanted selection markers. We used this method repeatedly and successfully to inactivate a specific gene, to introduce a gene of interest and to realize the in-frame deletion of a target gene in the same strain. As there is no prerequisite strain for this method, it will be a powerful and universal tool
Status of the compactlight design study*
CompactLight (XLS) is an International Collaboration of 24 partners and 5 third parties, funded by the European Union through the Horizon 2020 Research and Innovation Programme. The main goal of the project, which started in January 2018 with a duration of 36 months, is the design of an hard X-ray FEL facility beyond today’s state of the art, using the latest concepts for bright electron photo-injectors, high-gradient accelerating structures, and innovative short-period undulators. The specifications of the facility and the parameters of the future FEL are driven by the demands of potential users and the associated science cases. In this paper we will give an overview on the ongoing activities and the major results achieved until now
The Compact Linear Collider (CLIC) - 2018 Summary Report
The Compact Linear Collider (CLIC) is a TeV-scale high-luminosity linear collider under development at CERN. Following the CLIC conceptual design published in 2012, this report provides an overview of the CLIC project, its current status, and future developments. It presents the CLIC physics potential and reports on design, technology, and implementation aspects of the accelerator and the detector. CLIC is foreseen to be built and operated in stages, at centre-of-mass energies of 380 GeV, 1.5 TeV and 3 TeV, respectively. CLIC uses a two-beam acceleration scheme, in which 12 GHz accelerating structures are powered via a high-current drive beam. For the first stage, an alternative with X-band klystron powering is also considered. CLIC accelerator optimisation, technical developments and system tests have resulted in an increased energy efficiency (power around 170 MW) for the 380 GeV stage, together with a reduced cost estimate at the level of 6 billion CHF. The detector concept has been refined using improved software tools. Significant progress has been made on detector technology developments for the tracking and calorimetry systems. A wide range of CLIC physics studies has been conducted, both through full detector simulations and parametric studies, together providing a broad overview of the CLIC physics potential. Each of the three energy stages adds cornerstones of the full CLIC physics programme, such as Higgs width and couplings, top-quark properties, Higgs self-coupling, direct searches, and many precision electroweak measurements. The interpretation of the combined results gives crucial and accurate insight into new physics, largely complementary to LHC and HL-LHC. The construction of the first CLIC energy stage could start by 2026. First beams would be available by 2035, marking the beginning of a broad CLIC physics programme spanning 25-30 years