358 research outputs found
The Injector Layout of BERLinPro
BERLinPro is an Energy Recovery Linac Project running since 2011 at the HZB in Berlin. A conceptual design report has been published in 2012 [1]. One of the key components of the project is the 100 mA superconducting RF photocathode gun under development at the HZB since 2010. Starting in 2016 the injector will go into operation, providing 6.6 MeV electrons with an emittance well below 1mm mrad and bunches shorter than 5 ps. In 2017 the 50 MeV linac will be set up and full recirculation is planned for 2018. The injector design has been finalized and is described in detail in this paper. Emphasis is further laid on beam dynamics aspects and performance simulations of two different gun cavitie
Effect of projectile nose shape on ballistic resistance of interstitial-free steel sheets
In this paper an experimental and numerical work is reported concerning the process of perforation of thin steel plates using different projectile nose shapes. The main goal is to analyze how the projectile shape may change the ballistic properties of materials. A wide range of impact velocities from 35 to 180 m/s has been covered during the tests. All the projectiles were 13 mm in diameter and the targets were 1 mm thick, as such the projectile can be regarded as rigid and the target sheets were of interstitial-free (IF) steel. The mass ratio (projectile mass/steel sheet mass) and the ratio between the span of the steel sheet and the diameter of the projectile were kept constant, equal to 0.38 and 3.85 respectively. To define the thermoviscoplastic behavior of the target material, the Rusinek-Klepaczko (RK) constitutive model [1] was used. The complete identification of the material constants was done based on a rigorous material characterization. Numerical simulations of some experimental tests were carried out using a non-linear finite element code ABAQUS/Explicit. It was found that the numerical models are able to describe the physical mechanisms in the perforation process with a good accuracy.The National Centre of Research and Development under the grant WND-DEM-1-203/00
Field Emission Studies of Heat Treated Mo Substrates
Molybdenum can be used as a substrate for the bi alkali antimonide photocathodes utilized for the generation of high brightness electron beams in a superconducting radio frequency SRF photoinjector cavities. Operation at high field strength is required to obtain a low emittance beam, thus increasing the probability of field emission FE from the cathode surface. Usually, substrates are heated in situ before alkali de position to remove oxide layers from the surface. FE on Mo substrates was measured by means of a field emission scanning microscope FESM . It turned out that in situ heat treatment HT of the Mo surface significantly changes the FE behaviour by activation of new emitters. For a better understanding of the mechanism for enhanced emission after in situ heating a witness Mo sample was investigated using x ray photoelectron spectroscop
High-Intensity and High-Brightness Source of Moderated Positrons Using a Brilliant gamma Beam
Presently large efforts are conducted towards the development of highly
brilliant gamma beams via Compton back scattering of photons from a
high-brilliance electron beam, either on the basis of a normal-conducting
electron linac or a (superconducting) Energy Recovery Linac (ERL). Particularly
ERL's provide an extremely brilliant electron beam, thus enabling to generate
highest-quality gamma beams. A 2.5 MeV gamma beam with an envisaged intensity
of 10^15 s^-1, as ultimately envisaged for an ERL-based gamma-beam facility,
narrow band width (10^-3), and extremely low emittance (10^-4 mm^2 mrad^2)
offers the possibility to produce a high-intensity bright polarized positron
beam. Pair production in a face-on irradiated W converter foil (200 micron
thick, 10 mm long) would lead to the emission of 2 x 10^13 (fast) positrons per
second, which is four orders of magnitude higher compared to strong radioactive
^22Na sources conventionally used in the laboratory.Using a stack of converter
foils and subsequent positron moderation, a high-intensity low-energy beam of
moderated positrons can be produced. Two different source setups are presented:
a high-brightness positron beam with a diameter as low as 0.2 mm, and a
high-intensity beam of 3 x 10^11 moderated positrons per second. Hence,
profiting from an improved moderation efficiency, the envisaged positron
intensity would exceed that of present high-intensity positron sources by a
factor of 100.Comment: 9 pages, 3 figure
BERLinPro A Compact Demonstrator ERL for High Current and Low Emittance Beams
The HZB previously BESSY was the first institution in Germany to build and operate a dedicated synchrotron light source BESSY I . About 10 years ago BESSY II, a third generation synchrotron light source, was commissioned and is very successfully running since that time. Due to its expertise in development and operation of accelerator facilities HZB is ideally suited to realize new accelerator concepts. Therefore HZB is proposing to build a demonstrator ERL facility BERLinPro that will realize high current and low emittance operation at 100 MeV. BERLinPro is intented to bring ERL technology to maturity. This paper presents an overview of the project and the key components of the facilit
Angular Scaling in Jets
We introduce a jet shape observable defined for an ensemble of jets in terms
of two-particle angular correlations and a resolution parameter R. This
quantity is infrared and collinear safe and can be interpreted as a scaling
exponent for the angular distribution of mass inside the jet. For small R it is
close to the value 2 as a consequence of the approximately scale invariant QCD
dynamics. For large R it is sensitive to non-perturbative effects. We describe
the use of this correlation function for tests of QCD, for studying underlying
event and pile-up effects, and for tuning Monte Carlo event generators.Comment: Updated to JHEP versio
Jet Dipolarity: Top Tagging with Color Flow
A new jet observable, dipolarity, is introduced that can distinguish whether
a pair of subjets arises from a color singlet source. This observable is
incorporated into the HEPTopTagger and is shown to improve discrimination
between top jets and QCD jets for moderate to high pT.Comment: 8 pages, 6 figures (updated to JHEP version
Jet Substructure at the Tevatron and LHC: New results, new tools, new benchmarks
In this report we review recent theoretical progress and the latest
experimental results in jet substructure from the Tevatron and the LHC. We
review the status of and outlook for calculation and simulation tools for
studying jet substructure. Following up on the report of the Boost 2010
workshop, we present a new set of benchmark comparisons of substructure
techniques, focusing on the set of variables and grooming methods that are
collectively known as "top taggers". To facilitate further exploration, we have
attempted to collect, harmonise, and publish software implementations of these
techniques.Comment: 53 pages, 17 figures. L. Asquith, S. Rappoccio, C. K. Vermilion,
editors; v2: minor edits from journal revision
Structure of Fat Jets at the Tevatron and Beyond
Boosted resonances is a highly probable and enthusiastic scenario in any
process probing the electroweak scale. Such objects when decaying into jets can
easily blend with the cornucopia of jets from hard relative light QCD states.
We review jet observables and algorithms that can contribute to the
identification of highly boosted heavy jets and the possible searches that can
make use of such substructure information. We also review previous studies by
CDF on boosted jets and its measurements on specific jet shapes.Comment: invited review for a special "Top and flavour physics in the LHC era"
issue of The European Physical Journal C, we invite comments regarding
contents of the review; v2 added references and institutional preprint
number
Torsion-balance tests of the weak equivalence principle
We briefly summarize motivations for testing the weak equivalence principle
and then review recent torsion-balance results that compare the differential
accelerations of beryllium-aluminum and beryllium-titanium test body pairs with
precisions at the part in level. We discuss some implications of
these results for the gravitational properties of antimatter and dark matter,
and speculate about the prospects for further improvements in experimental
sensitivity.Comment: 17 pages, 9 figures (in press Classical Quantum Gravity 2012
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