8,612 research outputs found
Software digitizer for high granular gaseous detector
A sampling calorimeter equipped with gaseous sensor layers with digital
readout is near perfect for "Particle Flow Algorithm" approach, since it is
homogeneous over large surfaces, robust, cost efficient, easily segmentable to
any readout pad dimension and size and almost insensitive to neutrons. The
response of a finely segmented digital calorimeter is characterized by track
efficiency and multiplicity. Monte Carlo (MC) programs such as GEANT4 simulate
with high precision the energy deposited by particles. The sensor and
electronic response associated to a pad are calculated in a separate
"digitization" process. We developed a general method for simulating the pad
response, a digitization, reproducing efficiency and multiplicity, using the
spatial information from a simulation done at higher granularity. The
digitization method proposed here has been applied to gaseous detectors
including Glass Resistive Plate Chambers (GRPC) and MicroMegas. Validating the
method on test beam data, experimental observables such as efficiency,
multiplicity and mean number of hits at different thresholds have been
reproduced with high precision.Comment: Proceeding for MPGD 201
SGXIO: Generic Trusted I/O Path for Intel SGX
Application security traditionally strongly relies upon security of the
underlying operating system. However, operating systems often fall victim to
software attacks, compromising security of applications as well. To overcome
this dependency, Intel introduced SGX, which allows to protect application code
against a subverted or malicious OS by running it in a hardware-protected
enclave. However, SGX lacks support for generic trusted I/O paths to protect
user input and output between enclaves and I/O devices.
This work presents SGXIO, a generic trusted path architecture for SGX,
allowing user applications to run securely on top of an untrusted OS, while at
the same time supporting trusted paths to generic I/O devices. To achieve this,
SGXIO combines the benefits of SGX's easy programming model with traditional
hypervisor-based trusted path architectures. Moreover, SGXIO can tweak insecure
debug enclaves to behave like secure production enclaves. SGXIO surpasses
traditional use cases in cloud computing and makes SGX technology usable for
protecting user-centric, local applications against kernel-level keyloggers and
likewise. It is compatible to unmodified operating systems and works on a
modern commodity notebook out of the box. Hence, SGXIO is particularly
promising for the broad x86 community to which SGX is readily available.Comment: To appear in CODASPY'1
Observation of Coherently-Enhanced Tunable Narrow-Band Terahertz Transition Radiation from a Relativistic Sub-Picosecond Electron Bunch Train
We experimentally demonstrate the production of narrow-band (% at THz) THz transition radiation with tunable
frequency over [0.37, 0.86] THz. The radiation is produced as a train of
sub-picosecond relativistic electron bunches transits at the vacuum-aluminum
interface of an aluminum converter screen. We also show a possible application
of modulated beams to extend the dynamical range of a popular bunch length
diagnostic technique based on the spectral analysis of coherent radiation.Comment: 3 pages, 6 figure
Composite-fermion crystallites in quantum dots
The correlations in the ground state of interacting electrons in a
two-dimensional quantum dot in a high magnetic field are known to undergo a
qualitative change from liquid-like to crystal-like as the total angular
momentum becomes large. We show that the composite-fermion theory provides an
excellent account of the states in both regimes. The quantum mechanical
formation of composite fermions with a large number of attached vortices
automatically generates omposite fermion crystallites in finite quantum dots.Comment: 5 pages, 3 figure
Wave-optics modeling of the optical-transport line for passive optical stochastic cooling
This work was supported by the US Department of Energy (DOE) under contract DE-SC0013761 to Northern Illinois University. Fermilab is managed by the Fermi Research Alliance, LLC (DE-SC0013761 DEAC02-07CH11359) for the U.S. Department of Energy Office of Science Contract number DE-AC02-07CH11359.Optical stochastic cooling (OSC) is expected to enable fast cooling of dense particle beams. Transition from microwave to optical frequencies enables an achievement of stochastic cooling rates which are orders of magnitude higher than ones achievable with the classical microwave based stochastic cooling systems. A subsytem critical to the OSC scheme is the focusing optics used to image radiation from the upstream âpickupâ undulator to the downstream âkickerâ undulator. In this paper, we present simulation results using wave-optics calculation carried out with the Synchrotron Radiation Workshop (SRW). Our simulations are performed in support to a proof-of-principle experiment planned at the Integrable Optics Test Accelerator (IOTA) at Fermilab. The calculations provide an estimate of the energy kick received by a 100-MeV electron as it propagates in the kicker undulator and interacts with the electromagnetic pulse it radiated at an earlier time while traveling through the pickup undulato
Initial beam-profiling tests with the NML prototype station at the Fermilab A0 Photoinjector
The beam-profile diagnostics station prototype for the superconducting rf
electron linac being constructed at Fermilab at the New Muon Lab has been
tested. The station uses intercepting radiation converter screens for the
low-power beam mode: either a 100-\mu m thick YAG:Ce single crystal
scintillator or a 1-\mu m thin Al optical transition radiation (OTR) foil. The
screens are oriented with the surface perpendicular to the beam direction. A
downstream mirror with its surface at 45 degrees to the beam direction is used
to direct the radiation into the optical transport. The optical system has
better than 20 (10) \mu m rms spatial resolution when covering a vertical field
of view of 18 (5) mm. The initial tests were performed at the A0 Photoinjector
at a beam energy of ~15 MeV and with micropulse charges from 25 to 500 pC for
beam sizes of 45 to 250 microns. Example results will be presented.Comment: 3 pp. Particle Accelerator, 24th Conference (PAC'11) 2011. 28 Mar - 1
Apr 2011. New York, US
A Metrological Based Realization of Time-of-Flight Diffraction Technique
AbstractTime-of-Flight Diffraction (ToFD) is a technique of non-destructive testing by ultrasound used for detecting faults and discontinuities in different components. The development and implementation of this technique was based on ISO 16828:2012 (Non-Destructive testing â Ultrasonic Testing â Time-of-Flight Diffraction Technique as a method for Detection and Sizing of Discontinuities). Controlling the different characteristics of the system, from the specification of the ultrasonic characteristics, to the imaging technique, was possible to identify the sources of uncertainty and estimate the ToFD measurement uncertainty. For a 25mm deep stainless steel test object, expanded uncertainties less than 0.5%(0.093Â mm) was achieved with ToFD. For larger ultrasonic paths, the technique is able to depict even lower uncertainties, regarding some care are taken in the ultrasonic measurement setup
Farmersâ attitudes towards participation in short food supply chains: Evidence from a Chinese field research
As the industrialized agro-food supply systems have been commonly criticized for their adverse environmental and social impact, Short food supply chains have emerged as a promising sustainable alternative. Given that the history of SFSCs is relatively short, the majority of empirical evidences is from developed countries, and existing studies on SFSCs in developing country context are rather limited. Therefore, this study aims to investigate the farmersâ attitudes towards participating in SFSCs by conducting a field research in China. Semi-structured interviews were implemented with eight participants selected from a local farmer market as a pilot study. The social and economic reasons are found to be the main motivations of Chinese farmers participating in SFSCs. However, none of these interviewed participants are aware of the environmental effects of SFSCs. Moreover, the findings were cross-compared with existing studies conducted in developed countries. It was found that Chinese farmers participating in SFSCs are mainly passive choice, as they lack of relevant knowledge and governmental support
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