658 research outputs found
Systematic Differences due to High Energy Hadronic Interaction Models in Air Shower Simulations in the 100 GeV-100 TeV Range
The predictions of hadronic interaction models for cosmic-ray induced air
showers contain inherent uncertainties due to limitations of available
accelerator data and theoretical understanding in the required energy and
rapidity regime. Differences between models are typically evaluated in the
range appropriate for cosmic-ray air shower arrays (- eV).
However, accurate modelling of charged cosmic-ray measurements with ground
based gamma-ray observatories is becoming more and more important. We assess
the model predictions on the gross behaviour of measurable air shower
parameters in the energy (0.1-100 TeV) and altitude ranges most appropriate for
detection by ground-based gamma-ray observatories. We go on to investigate the
particle distributions just after the first interaction point, to examine how
differences in the micro-physics of the models may compound into differences in
the gross air shower behaviour. Differences between the models above 1 TeV are
typically less than 10%. However, we find the largest variation in particle
densities at ground at the lowest energy tested (100 GeV), resulting from
striking differences in the early stages of shower development.Comment: 9 pages, 6 figures. Published by Phys Rev
Latest news from the HAWC outrigger array
The High Altitude Water Cherenkov (HAWC) observatory is a very high energy gamma-ray detector located in Mexico. In late 2018, the HAWC collaboration completed a major upgrade consisting of the addition of a sparse outrigger array of 345 small water Cherenkov detectors (WCDs) surrounding the 300 WCDs of the main array and extending the instrumented area by a factor of 4. It provides an improved reconstruction of the showers whose core and footprint are not well contained in the array and increases the effective area in the range of a few TeV to beyond 100 TeV. This improvement in sensitivity will help to have a better understanding of the Galactic sources that accelerate particles up to the knee of the cosmic ray spectrum. In this contribution, we will show the current status, the performance, and the first results from the HAWC outrigger array
TARGET: A Digitizing And Trigger ASIC For The Cherenkov Telescope Array
The future ground-based gamma-ray observatory Cherenkov Telescope Array (CTA)
will feature multiple types of imaging atmospheric Cherenkov telescopes, each
with thousands of pixels. To be affordable, camera concepts for these
telescopes have to feature low cost per channel and at the same time meet the
requirements for CTA in order to achieve the desired scientific goals. We
present the concept of the TeV Array Readout Electronics with GSa/s sampling
and Event Trigger (TARGET) Application Specific Circuit (ASIC), envisaged to be
used in the cameras of various CTA telescopes, e.g. the Gamma-ray Cherenkov
Telescope (GCT), a proposed 2-Mirror Small-Sized Telescope, and the
Schwarzschild-Couder Telescope (SCT), a proposed Medium-Sized Telescope. In the
latest version of this readout concept the sampling and trigger parts are split
into dedicated ASICs, TARGET C and T5TEA, both providing 16 parallel input
channels. TARGET C features a tunable sampling rate (usually 1 GSa/s), a 16k
sample deep buffer for each channel and on-demand digitization and transmission
of waveforms with typical spans of ~100 ns. The trigger ASIC, T5TEA, provides 4
low voltage differential signal (LVDS) trigger outputs and can generate a
pedestal voltage independently for each channel. Trigger signals are generated
by T5TEA based on the analog sum of the input in four independent groups of
four adjacent channels and compared to a threshold set by the user. Thus, T5TEA
generates four LVDS trigger outputs, as well as 16 pedestal voltages fed to
TARGET C independently for each channel. We show preliminary results of the
characterization and testing of TARGET C and T5TEA.Comment: 6 pages, 8 figures, Proceedings of the 6th International Symposium on
High-Energy Gamma-Ray Astronomy (Gamma2016
A Template-based gamma-ray Reconstruction Method for Air Shower Arrays
We introduce a new Monte Carlo template-based reconstruction method for air shower arrays, with a focus on shower core and energy reconstruction of -ray induced air showers. The algorithm fits an observed lateral amplitude distribution of an extensive air shower against an expected probability distribution using a likelihood approach. A full Monte Carlo air shower simulation in combination with the detector simulation is used to generate the expected probability distributions. The goodness of fit can be used to discriminate between -ray and hadron induced air showers. As an example, we apply this method to the High Altitude Water Cherenkov -ray Observatory and its recently installed high-energy upgrade. The performance of this method and the applicability to air shower arrays with mixed detector types makes it a promising reconstruction approach for current and future instruments
Employment status and work-related problems of gastrointestinal cancer patients at diagnosis: a cross-sectional study
Objective To assess the employment status of patients with gastrointestinal cancer at diagnosis and to examine work-related problems of employed patients. Design New, consecutive patients were included at the Gastrointestinal Oncology Center Amsterdam, a one-stop, rapid access diagnostic assessment centre. Patients were interviewed on their employment status by a nurse. If (self-) employed, patients were asked to self-report on work-related problems, perceived distress (0-10), cancer-related problems, fatigue (MFI-20, range 4-20) and work ability (three WAI questions, range 0-10). Results Of all 333 included new consecutive patients (age range 32-89 years), 95 patients (28%) were (self-) employed at time of diagnosis, 179 (54%) were pensioners, and 59 were not working (18%). For the assessment of work-related problems, 45 (47%) of these 95 employed patients with cancer participated. Their mean age was 56 years, and patients had oesophageal/stomach (49%), colorectal (18%) or hepatic/pancreatic/biliary cancer (33%). Half of the employed patients (49%) were still at work, while 51% were on sick leave. The main reasons for sick leave were stress (35%), (scheduled) operation (26%), fatigue (17%) and pain (13%). Most patients on sick leave (70%) had no contact with their own occupational physician, although the majority (67%) would like to continue to work. Work-related problems were experienced by 73% of working patients. The mean work ability was 5.4, the mean general fatigue score was 11.5, and the mean distress score was 4.7. Employed patients on sick leave reported a lower work ability, more fatigue and higher distress but no more cancer-related problems compared with those still working. Conclusion A quarter of all patients with gastrointestinal cancer seen at an oncological centre are employed at time of diagnosis, and of these employed patients, 73% experience work-related problems. During diagnosis and treatment, information and support on work-related issues should be offered to patients with cancer as an essential part of high-quality oncological car
The first GCT camera for the Cherenkov Telescope Array
The Gamma Cherenkov Telescope (GCT) is proposed to be part of the Small Size
Telescope (SST) array of the Cherenkov Telescope Array (CTA). The GCT
dual-mirror optical design allows the use of a compact camera of diameter
roughly 0.4 m. The curved focal plane is equipped with 2048 pixels of
~0.2{\deg} angular size, resulting in a field of view of ~9{\deg}. The GCT
camera is designed to record the flashes of Cherenkov light from
electromagnetic cascades, which last only a few tens of nanoseconds. Modules
based on custom ASICs provide the required fast electronics, facilitating
sampling and digitisation as well as first level of triggering. The first GCT
camera prototype is currently being commissioned in the UK. On-telescope tests
are planned later this year. Here we give a detailed description of the camera
prototype and present recent progress with testing and commissioning.Comment: In Proceedings of the 34th International Cosmic Ray Conference
(ICRC2015), The Hague, The Netherlands. All CTA contributions at
arXiv:1508.0589
Accelerator measurements of magnetically-induced radio emission from particle cascades with applications to cosmic-ray air showers
For fifty years, cosmic-ray air showers have been detected by their radio
emission. We present the first laboratory measurements that validate
electrodynamics simulations used in air shower modeling. An experiment at SLAC
provides a beam test of radio-frequency (RF) radiation from charged particle
cascades in the presence of a magnetic field, a model system of a cosmic-ray
air shower. This experiment provides a suite of controlled laboratory
measurements to compare to particle-level simulations of RF emission, which are
relied upon in ultra-high-energy cosmic-ray air shower detection. We compare
simulations to data for intensity, linearity with magnetic field, angular
distribution, polarization, and spectral content. In particular, we confirm
modern predictions that the magnetically induced emission in a dielectric forms
a cone that peaks at the Cherenkov angle and show that the simulations
reproduce the data within systematic uncertainties.Comment: 5 pages, 7 figure
A new method for detection of induced mutations in wheat
Contains fulltext :
141188.pdf (preprint version ) (Open Access
Antarctic Surface Reflectivity Measurements from the ANITA-3 and HiCal-1 Experiments
The primary science goal of the NASA-sponsored ANITA project is measurement
of ultra-high energy neutrinos and cosmic rays, observed via radio-frequency
signals resulting from a neutrino- or cosmic ray- interaction with terrestrial
matter (atmospheric or ice molecules, e.g.). Accurate inference of the energies
of these cosmic rays requires understanding the transmission/reflection of
radio wave signals across the ice-air boundary. Satellite-based measurements of
Antarctic surface reflectivity, using a co-located transmitter and receiver,
have been performed more-or-less continuously for the last few decades.
Satellite-based reflectivity surveys, at frequencies ranging from 2--45 GHz and
at near-normal incidence, yield generally consistent reflectivity maps across
Antarctica. Using the Sun as an RF source, and the ANITA-3 balloon borne
radio-frequency antenna array as the RF receiver, we have also measured the
surface reflectivity over the interval 200-1000 MHz, at elevation angles of
12-30 degrees, finding agreement with the Fresnel equations within systematic
errors. To probe low incidence angles, inaccessible to the Antarctic Solar
technique and not probed by previous satellite surveys, a novel experimental
approach ("HiCal-1") was devised. Unlike previous measurements, HiCal-ANITA
constitute a bi-static transmitter-receiver pair separated by hundreds of
kilometers. Data taken with HiCal, between 200--600 MHz shows a significant
departure from the Fresnel equations, constant with frequency over that band,
with the deficit increasing with obliquity of incidence, which we attribute to
the combined effects of possible surface roughness, surface grain effects,
radar clutter and/or shadowing of the reflection zone due to Earth curvature
effects.Comment: updated to match publication versio
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