1,030 research outputs found
Neutron-induced background in the CONUS experiment
CONUS is a novel experiment aiming at detecting elastic neutrino nucleus
scattering in the fully coherent regime using high-purity Germanium (Ge)
detectors and a reactor as antineutrino () source. The detector setup
is installed at the commercial nuclear power plant in Brokdorf, Germany, at a
very small distance to the reactor core in order to guarantee a high flux of
more than 10/(scm). For the experiment, a good
understanding of neutron-induced background events is required, as the neutron
recoil signals can mimic the predicted neutrino interactions. Especially
neutron-induced events correlated with the thermal power generation are
troublesome for CONUS. On-site measurements revealed the presence of a thermal
power correlated, highly thermalized neutron field with a fluence rate of
(74530)cmd. These neutrons that are produced by nuclear
fission inside the reactor core, are reduced by a factor of 10 on
their way to the CONUS shield. With a high-purity Ge detector without shield
the -ray background was examined including highly thermal power
correlated N decay products as well as -lines from neutron
capture. Using the measured neutron spectrum as input, it was shown, with the
help of Monte Carlo simulations, that the thermal power correlated field is
successfully mitigated by the installed CONUS shield. The reactor-induced
background contribution in the region of interest is exceeded by the expected
signal by at least one order of magnitude assuming a realistic ionization
quenching factor of 0.2.Comment: 28 pages, 28 figure
A massive cluster of Red Supergiants at the base of the Scutum-Crux arm
We report on the unprecedented Red Supergiant (RSG) population of a massive
young cluster, located at the base of the Scutum-Crux Galactic arm. We identify
candidate cluster RSGs based on {\it 2MASS} photometry and medium resolution
spectroscopy. With follow-up high-resolution spectroscopy, we use CO-bandhead
equivalent width and high-precision radial velocity measurements to identify a
core grouping of 26 physically-associated RSGs -- the largest such cluster
known to-date. Using the stars' velocity dispersion, and their inferred
luminosities in conjuction with evolutionary models, we argue that the cluster
has an initial mass of 40,000\msun, and is therefore among the most
massive in the galaxy. Further, the cluster is only a few hundred parsecs away
from the cluster of 14 RSGs recently reported by Figer et al (2006). These two
RSG clusters represent 20% of all known RSGs in the Galaxy, and now offer the
unique opportunity to study the pre-supernova evolution of massive stars, and
the Blue- to Red-Supergiant ratio at uniform metallicity. We use GLIMPSE,
MIPSGAL and MAGPIS survey data to identify several objects in the field of the
larger cluster which seem to be indicative of recent region-wide starburst
activity at the point where the Scutum-Crux arm intercepts the Galactic bulge.
Future abundance studies of these clusters will therefore permit the study of
the chemical evolution and metallicity gradient of the Galaxy in the region
where the disk meets the bulge.Comment: 49 pages, 22 figures. Accepted for publication in ApJ. Version with
hi-res figures can be found at http://www.cis.rit.edu/~bxdpci/RSGC2.pd
Wood/bark adhesion and methods of reducing adhesion in hardwood species. Project 2929, report one : a progress report to Members of Group Project 2929.
"December 21, 1970.""The Institute of Paper Chemistry ... Dean W. Einspahr, John D. Hankey, W. A. Wink, Miles K. Benson, and John W. Swanson.
Constraints on elastic neutrino nucleus scattering in the fully coherent regime from the CONUS experiment
We report the best limit on coherent elastic scattering of electron antineutrinos emitted from a nuclear reactor off germanium nuclei. The measurement was performed with the CONUS detectors positioned at 17.1m from the 3.9GWth reactor core of the nuclear power plant in Brokdorf, Germany. The antineutrino energies of less than 10 MeV assure interactions in the fully coherent regime. The analyzed dataset includes 248.7 kgd with the reactor turned on and background data of 58.8 kgd with the reactor off. With a quenching parameter of k = 0.18 for germanium, we determined an upper limit on the number of neutrino events of 85 in the region of interest at 90% confidence level. This new CONUS dataset disfavors quenching parameters above k = 0.27, under the assumption of standard-model-like coherent scattering of the reactor antineutrinos
Full background decomposition of the CONUS experiment
The CONUS experiment is searching for coherent elastic neutrino nucleus scattering of reactor anti-neutrinos with four low energy threshold point-contact high-purity germanium spectrometers. An excellent background suppression within the region of interest below 1keV (ionization energy) is absolutely necessary to enable a signal detection. The collected data also make it possible to set limits on various models regarding beyond the standard model physics. These analyses benefit as well from the low background level of ~10dkgbelow 1keV and at higher energies. The low background level is achieved by employing a compact shell-like shield, that was adapted to the most relevant background sources at the shallow depth location of the experiment: environmental gamma-radiation and muon-induced secondaries. Overall, the compact CONUS shield including the active anti-coincidence muon-veto reduces the background by more than four orders of magnitude. The remaining background is described with validated Monte Carlo simulations which include the detector response. It is the first time that a full background decomposition in germanium operated at reactor-site has been achieved. Next to remaining muon-induced background, Pb within the shield and cryostat end caps, cosmogenic activation and air-borne radon are the most relevant background sources. The reactor-correlated background is negligible within the shield. The validated background model together with the parameterization of the noise are used as input to the likelihood analyses of the various physics cases
Expansion of W 3(OH)
A direct measurement of the expansion of W 3(OH) is made by comparing Very
Large Array images taken about 10 yr apart. The expansion is anisotropic with a
typical speed of 3 to 5 km/s, indicating a dynamical age of only 2300 yr. These
observations are inconsistent with either the freely expanding shell model or a
simple bow shock model. The most favored model is a slowly expanding shell-like
HII region, with either a fast rarefied flow or another less massive diffuse
ionized region moving towards the observer. There is also a rapidly evolving
source near the projected center of emission, perhaps related to the central
star.Comment: LaTeX file, 28 pages, includes 8 figures. To appear in ApJ in
December 10 (1998) issue. Also available at
http://www.submm.caltech.edu/~kawamura/w3oh_pp.p
Hard X-ray emission in the star-forming region ON2: discovery with XMM-Newton
We obtained X-ray XMM-Newton observations of the open cluster Berkeley 87 and
the massive star-forming region (SFR) ON 2. In addition, archival infrared
Spitzer Space Telescope observations were used. It is likely that the SFR ON 2
and Berkeley 87 are at the same distance, 1.23 kpc, and hence are associated.
The XMM-Newton observations detected X-rays from massive stars in Berkeley 87
as well as diffuse emission from the SFR ON 2. The two patches of diffuse X-ray
emission are encompassed in the shell-like H II region GAL 75.84+0.40 in the
northern part of ON 2 and in the ON 2S region in the southern part of ON 2. The
diffuse emission from GAL 75.84+0.40 suffers an absorption column equivalent to
A_V approx. 28 mag. Its spectrum can be fitted either with a thermal plasma
model at T < 30 MK or by an absorbed power-law model with gamma; approx. -2.6.
The X-ray luminosity of GAL 75.84+0.40 is L_X approx. 6 10^31 erg/s. The
diffuse emission from ON 2S is adjacent to the ultra-compact H II (UCHII)
region Cygnus 2N, but does not coincide with it or with any other known UCHII
region. It has a luminosity of L_X approx. 4 10^31 erg/s. The spectrum can be
fitted with an absorbed power-law model with gamma; approx.-1.4. We adopt the
view of Turner and Forbes (1982) that the SFR ON 2 is physically associated
with the massive star cluster Berkeley 87 hosting the WO type star WR 142. We
discuss different explanations for the apparently diffuse X-ray emission in
these SFRs. These include synchrotron radiation, invoked by the co-existence of
strongly shocked stellar winds and turbulent magnetic fields in the
star-forming complex, cluster wind emission, or an unresolved population of
discrete sources.Comment: ApJ 2010, 712, 763. Reduced fig. resolution. Full resolution version
is at
http://www.astro.physik.uni-potsdam.de/research/abstracts/oskinova-ber87.htm
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