443 research outputs found
Performance of ePix10K, a high dynamic range, gain auto-ranging pixel detector for FELs
ePix10K is a hybrid pixel detector developed at SLAC for demanding
free-electron laser (FEL) applications, providing an ultrahigh dynamic range
(245 eV to 88 MeV) through gain auto-ranging. It has three gain modes (high,
medium and low) and two auto-ranging modes (high-to-low and medium-to-low). The
first ePix10K cameras are built around modules consisting of a sensor flip-chip
bonded to 4 ASICs, resulting in 352x384 pixels of 100 m x 100 m each.
We present results from extensive testing of three ePix10K cameras with FEL
beams at LCLS, resulting in a measured noise floor of 245 eV rms, or 67 e
equivalent noise charge (ENC), and a range of 11000 photons at 8 keV. We
demonstrate the linearity of the response in various gain combinations: fixed
high, fixed medium, fixed low, auto-ranging high to low, and auto-ranging
medium-to-low, while maintaining a low noise (well within the counting
statistics), a very low cross-talk, perfect saturation response at fluxes up to
900 times the maximum range, and acquisition rates of up to 480 Hz. Finally, we
present examples of high dynamic range x-ray imaging spanning more than 4
orders of magnitude dynamic range (from a single photon to 11000
photons/pixel/pulse at 8 keV). Achieving this high performance with only one
auto-ranging switch leads to relatively simple calibration and reconstruction
procedures. The low noise levels allow usage with long integration times at
non-FEL sources. ePix10K cameras leverage the advantages of hybrid pixel
detectors with high production yield and good availability, minimize
development complexity through sharing the hardware, software and DAQ
development with all other versions of ePix cameras, while providing an upgrade
path to 5 kHz, 25 kHz and 100 kHz in three steps over the next few years,
matching the LCLS-II requirements.Comment: 9 pages, 5 figure
Functional assessment of glucocerebrosidase modulator efficacy in primary patient-derived macrophages is essential for drug development and patient stratification.
Report on 240Am(n,x) surrogate cross section test measurement
The main goal of the test measurement was to determine the feasibility of the {sup 243}Am(p,t) reaction as a surrogate for {sup 240}Am(n,f). No data cross section data exists for neutron induced reactions on {sup 240}Am; the half-life of this isotope is only 2.1 days making direct measurements difficult, if not impossible. The 48-hour experiment was conducted using the STARS/LIBERACE experimental facility located at the 88 Inch Cyclotron at Lawrence Berkeley National Laboratory in August 2011. A description of the experiment and results is given. The beam energy was initially chosen to be 39 MeV in order to measure an equivalent neutron energy range from 0 to 20 MeV. However, the proton beam was not stopped in the farady cup and the beam was deposited in the surrounding shielding material. The shielding material was not conductive, and a beam current, needed for proper tuning of the beam as well as experimental monitoring, could not be read. If the {sup 240}Am(n,f) surrogate experiment is to be run at LBNL, simple modifications to the beam collection site will need to be made. The beam energy was reduced to 29 MeV, which was within an energy regime of prior experiments and tuning conditions at STARS/LIBERACE. At this energy, the beam current was successfully tuned and measured. At 29 MeV, data was collected with both the {sup 243}Am and {sup 238}U targets. An example particle identification plot is shown in Fig. 1. The triton-fission coincidence rate for the {sup 243}Am target and {sup 238}U target were measured. Coincidence rates of 0.0233(1) cps and 0.150(6) cps were observed for the {sup 243}Am and {sup 238}U targets, respectively. The difference in count rate is largely attributed to the available target material - the {sup 238}U target contains approximately 7 times more atoms than the {sup 243}Am. A proton beam current of {approx}0.7 nA was used for measurements on both targets. Assuming a full experimental run under similar conditions, an estimate for the run time needed was made. Figure 2 shows the number of days needed as a function of acceptable uncertainty for a measurement of 1-20 MeV equivalent neutron energy, binned into 200 keV increments. A 5% measurement will take 3 days for U, but 20 days for Am. It may be difficult to be the sole user of the LBNL cyclotron, or another facility, for such an extended period. However, a 10% measurement will take 19 hours for U, and 5 days for Am. Such a run period is more reasonable and will allow for the first ever measurement of the {sup 240}Am(n,f) cross section. We also anticipate 40% more beam time being available at Texas A&M Cyclotron Institute compared to LBNL in FY2012. The increased amount of beam time will allow us to accumulate better statistics then what would have been available at LBNL
Accelerator Testing of the General Antiparticle Spectrometer, a Novel Approach to Indirect Dark Matter Detection
We report on recent accelerator testing of a prototype general antiparticle
spectrometer (GAPS). GAPS is a novel approach for indirect dark matter searches
that exploits the antideuterons produced in neutralino-neutralino
annihilations. GAPS captures these antideuterons into a target with the
subsequent formation of exotic atoms. These exotic atoms decay with the
emission of X-rays of precisely defined energy and a correlated pion signature
from nuclear annihilation. This signature uniquely characterizes the
antideuterons. Preliminary analysis of data from a prototype GAPS in an
antiproton beam at the KEK accelerator in Japan has confirmed the
multi-X-ray/pion star topology and indicated X-ray yields consistent with prior
expectations. Moreover our success in utilizing solid rather than gas targets
represents a significant simplification over our original approach and offers
potential gains in sensitivity through reduced dead mass in the target area.Comment: 18 pages, 9 figures, submitted to JCA
Sneutrino cold dark matter, a new analysis: relic abundance and detection rates
We perform a new and updated analysis of sneutrinos as dark matter
candidates, in different classes of supersymmetric models. We extend previous
analyses by studying sneutrino phenomenology for full variations of the
supersymmetric parameters which define the various models. We first revisit the
standard Minimal Supersymmetric Standard Model, concluding that sneutrinos are
marginally compatible with existing experimental bounds, including direct
detection, provided they compose a subdominant component of dark matter. We
then study supersymmetric models with the inclusion of right-handed fields and
lepton-number violating terms. Simple versions of the lepton-number-violating
models do not lead to phenomenology different from the standard case when the
neutrino mass bounds are properly included. On the contrary, models with
right-handed fields are perfectly viable: they predict sneutrinos which are
compatible with the current direct detection sensitivities, both as subdominant
and dominant dark matter components. We also study the indirect detection
signals for such successful models: predictions for antiproton, antideuteron
and gamma-ray fluxes are provided and compared with existing and future
experimental sensitivities. The neutrino flux from the center of the Earth is
also analyzed.Comment: 72 pages, 50 figures. The version on the archive has low-resolution
figures. The paper with high resolution figures may be found through
http://www.to.infn.it/~arina/papers or
http://www.to.infn.it/~fornengo/Research/paperlist.htm
Baseline features of the VICTORIA (Vericiguat Global Study in Subjects with Heart Failure with Reduced Ejection Fraction) trial
Aim Describe the distinguishing features of heart failure (HF) patients with reduced ejection fraction (HFrEF) in the VICTORIA (Vericiguat Global Study in Patients with Heart Failure with Reduced Ejection Fraction) trial. Methods and results Key background characteristics were evaluated in 5050 patients randomized in VICTORIA and categorized into three cohorts reflecting their index worsening HF event. Differences within the VICTORIA population were assessed and compared with PARADIGM-HF (Prospective comparison of ARNI with ACEI to Determine Impact on Global Mortality and Morbidity in Heart Failure) and COMMANDER HF (A Study to Assess the Effectiveness and Safety of Rivaroxaban in Reducing the Risk of Death, Myocardial Infarction, or Stroke in Participants with Heart Failure and Coronary Artery Disease Following an Episode of Decompensated Heart Failure). VICTORIA patients had increased risk of mortality and rehospitalization: New York Heart Association class (40% class III), atrial fibrillation (45%), diabetes (47%), hypertension (79%) and mean estimated glomerular filtration rate of 61.5 mL/min/1.73m2. Baseline standard of HF care was very good: 60% received triple therapy. Their N-terminal pro-B-type natriuretic peptide was 3377 pg/mL [interquartile range (IQR) 1992-6380]. Natriuretic peptides were 30% higher level in the 67% patients with HF hospitalization Conclusions VICTORIA comprises a broadly generalizable high-risk population of three unique clinical strata of worsening chronic HFrEF despite very good HF therapy. VICTORIA will establish the role of vericiguat, a soluble guanylate cyclase stimulator, in HFrEF
NuSTAR Hard X-ray Survey of the Galactic Center Region I: Hard X-ray Morphology and Spectroscopy of the Diffuse Emission
We present the first sub-arcminute images of the Galactic Center above 10
keV, obtained with NuSTAR. NuSTAR resolves the hard X-ray source IGR
J17456-2901 into non-thermal X-ray filaments, molecular clouds, point sources
and a previously unknown central component of hard X-ray emission (CHXE).
NuSTAR detects four non-thermal X-ray filaments, extending the detection of
their power-law spectra with - up to ~50 keV. A
morphological and spectral study of the filaments suggests that their origin
may be heterogeneous, where previous studies suggested a common origin in young
pulsar wind nebulae (PWNe). NuSTAR detects non-thermal X-ray continuum emission
spatially correlated with the 6.4 keV Fe K fluorescence line emission
associated with two Sgr A molecular clouds: MC1 and the Bridge. Broad-band
X-ray spectral analysis with a Monte-Carlo based X-ray reflection model
self-consistently determined their intrinsic column density (
cm), primary X-ray spectra (power-laws with ) and set a
lower limit of the X-ray luminosity of Sgr A* flare illuminating the Sgr A
clouds to erg s. Above ~20 keV, hard
X-ray emission in the central 10 pc region around Sgr A* consists of the
candidate PWN G359.95-0.04 and the CHXE, possibly resulting from an unresolved
population of massive CVs with white dwarf masses . Spectral energy distribution analysis suggests that G359.95-0.04 is
likely the hard X-ray counterpart of the ultra-high gamma-ray source HESS
J1745-290, strongly favoring a leptonic origin of the GC TeV emission.Comment: 27 pages. Accepted for publication in the Astrophysical Journa
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