This paper presents the experimental and calculated results of the investigation of soot formation in a standard premixed ethylene/air flame with the addition of 15–100% dimethyl ether. The soot ...volume fraction was measured using the laser light extinction method at a wavelength of 520 nm. The flame temperature versus height above the burner was measured using standard Pt-Rh thermocouples. It was experimentally shown that the addition of 15% dimethyl ether to ethylene/air flame resulted in a 20% increase of soot volume fraction. The further replacement of ethylene by 60% dimethyl ether decreased the soot volume fraction at 5 fold relatively to a pure ethylene/air flame. Kinetic modeling of soot volume fraction growth with height above the burner was carried out based on the kinetic mechanisms developed by CREСK group (http://creckmodeling.chem.polimi.it/). The calculations were carried out using open software package OpenSMOKE ++, which includes the modeling of gas-dynamic processes in the premixed laminar flame reactor. Good agreement between the experimental and calculated data was obtained. The analysis of kinetic mechanism used in this study allowed determining the peculiarity of kinetic pathways of benzene formation, which is proposed as an initial substance for soot precursor. It was found, that increase of soot concentration at 15% dimethyl ether addition to the ethylene/air flame is caused by intensification of channel of benzene formation via C3H3 recombination, which additionally produced from C3H4-p (propyne). In turn, the increase of C3H4-p concentration occurred due to reactions of acetylene with CH3 radical formed during DME decomposition. These results obtained in a standard ethylene/air flame could be used for development and validation of various kinetic mechanisms of soot formation.
Alpha backgrounds in the AMoRE-Pilot experiment Alenkov, V.; Bae, H. W.; Beyer, J. ...
The European physical journal. C, Particles and fields,
12/2022, Letnik:
82, Številka:
12
Journal Article
Recenzirano
Odprti dostop
The Advanced Mo-based Rare process Experiment (AMoRE)-Pilot experiment is an initial phase of the AMoRE search for neutrinoless double beta decay of
100
Mo, with the purpose of investigating the ...level and sources of backgrounds. Searches for neutrinoless double beta decay generally require ultimately low backgrounds. Surface
α
decays on the crystals themselves or nearby materials can deposit a continuum of energies that can be as high as the
Q
-value of the decay itself and may fall in the region of interest (ROI). To understand these background events, we studied backgrounds from radioactive contaminations internal to and on the surface of the crystals or nearby materials with Geant4-based Monte Carlo simulations. In this study, we report on the measured
α
energy spectra fitted with the corresponding simulated spectra for six crystal detectors, where sources of background contributions could be identified through high energy
α
peaks and continuum parts in the energy spectrum for both internal and surface contaminations. We determine the low-energy contributions from internal and surface
α
contaminations by extrapolating from the
α
background fitting model.
Abstract The GERmanium Detector Array ( Gerda ) experiment operated enriched high-purity germanium detectors in a liquid argon cryostat, which contains 0.33% of $$^{36}$$ 36 Ar, a candidate isotope ...for the two-neutrino double-electron capture (2 $$\nu $$ ν ECEC) and therefore for the neutrinoless double-electron capture (0 $$\nu $$ ν ECEC). If detected, this process would give evidence of lepton number violation and the Majorana nature of neutrinos. In the radiative 0 $$\nu $$ ν ECEC of $$^{36}$$ 36 Ar, a monochromatic photon is emitted with an energy of 429.88 keV, which may be detected by the Gerda germanium detectors. We searched for the $$^{36}$$ 36 Ar 0 $$\nu $$ ν ECEC with Gerda data, with a total live time of 4.34 year (3.08 year accumulated during Gerda Phase II and 1.26 year during Gerda Phase I). No signal was found and a 90% CL lower limit on the half-life of this process was established $$T_{1/2} >1.5\cdot 10^{22} $$ T 1 / 2 > 1.5 · 10 22 year.
The GERmanium Detector Array (Gerda) experiment at the Gran Sasso underground laboratory (LNGS) of INFN is searching for neutrinoless double beta (0νββ) decay of 76 Ge. The signature of the signal is ...a monoenergetic peak at 2039 keV, the Q ββ value of the decay. To avoid bias in the signal search, the present analysis does not consider all those events, that fall in a 40 keV wide region centered around Q ββ. The main parameters needed for the 0νββ analysis are described. A background model was developed to describe the observed energy spectrum. The model contains several contributions, that are expected on the basis of material screening or that are established by the observation of characteristic structures in the energy spectrum. The model predicts a flat energy spectrum for the blinding window around Qββ with a background index ranging from 17.6 to 23.8 × 10 -3 cts/(keV kg yr). A part of the data not considered before has been used to test if the predictions of the background model are consistent. The observed number of events in this energy region is consistent with the background model. The background at Q ββ is dominated by close sources, mainly due to 42 K, 214 Bi, 228 </sup Th, 60 Co and α emitting isotopes from the 226 Ra decay chain. The individual fractions depend on the assumed locations of the contaminants. It is shown, that after removal of the known γ peaks, the energy spectrum can be fitted in an energy range of 200 keV around Q ββ with a constant background. This gives a background index consistent with the full model and uncertainties of the same size.
Abstract
We search for tri-nucleon decays of
$$^{76}$$
76
Ge in the dataset from the GERmanium Detector Array (GERDA) experiment. Decays that populate excited levels of the daughter nucleus above the ...threshold for particle emission lead to disintegration and are not considered. The ppp-, ppn-, and pnn-decays lead to
$$^{73}$$
73
Cu,
$$^{73}$$
73
Zn, and
$$^{73}$$
73
Ga nuclei, respectively. These nuclei are unstable and eventually proceed by the beta decay of
$$^{73}$$
73
Ga to
$$^{73}$$
73
Ge (stable). We search for the
$$^{73}$$
73
Ga decay exploiting the fact that it dominantly populates the 66.7 keV
$$^{73m}$$
73
m
Ga state with half-life of 0.5 s. The nnn-decays of
$$^{76}$$
76
Ge that proceed via
$$^{73m}$$
73
m
Ge are also included in our analysis. We find no signal candidate and place a limit on the sum of the decay widths of the inclusive tri-nucleon decays that corresponds to a lower lifetime limit of 1.2
$$\times $$
×
10
$$^{26}$$
26
yr (90% credible interval). This result improves previous limits for tri-nucleon decays by one to three orders of magnitude.
Search for tri-nucleon decays of 76Ge in GERDA Agostini, M.; Alexander, A.; Bakalyarov, A. M. ...
The European physical journal. C, Particles and fields,
09/2023, Letnik:
83, Številka:
9
Journal Article
Recenzirano
Odprti dostop
We search for tri-nucleon decays of
76
Ge in the dataset from the GERmanium Detector Array (GERDA) experiment. Decays that populate excited levels of the daughter nucleus above the threshold for ...particle emission lead to disintegration and are not considered. The ppp-, ppn-, and pnn-decays lead to
73
Cu,
73
Zn, and
73
Ga nuclei, respectively. These nuclei are unstable and eventually proceed by the beta decay of
73
Ga to
73
Ge (stable). We search for the
73
Ga decay exploiting the fact that it dominantly populates the 66.7 keV
73
m
Ga state with half-life of 0.5 s. The nnn-decays of
76
Ge that proceed via
73
m
Ge are also included in our analysis. We find no signal candidate and place a limit on the sum of the decay widths of the inclusive tri-nucleon decays that corresponds to a lower lifetime limit of 1.2
×
10
26
yr (90% credible interval). This result improves previous limits for tri-nucleon decays by one to three orders of magnitude.
(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image).The GERmanium Detector Array (Gerda) at the Gran Sasso Underground Laboratory (LNGS) searches for the neutrinoless double ...beta decay (...) of ...Ge. Germanium detectors made of material with an enriched ...Ge fraction act simultaneously as sources and detectors for this decay. During Phase I of theexperiment mainly refurbished semi-coaxial Ge detectors from former experiments were used. For the upcoming Phase II, 30 new ...Ge enriched detectors of broad energy germanium (BEGe)-type were produced. A subgroup of these detectors has already been deployed in Gerda during Phase I. The present paper reviews the complete production chain of these BEGe detectors including isotopic enrichment, purification, crystal growth and diode production. The efforts in optimizing the mass yield and in minimizing the exposure of the ...Ge enriched germanium to cosmic radiation during processing are described. Furthermore, characterization measurements in vacuum cryostats of the first subgroup of seven BEGe detectors and their long-term behavior in liquid argon are discussed. The detector performance fulfills the requirements needed for the physics goals of Gerda Phase II.
We search for tri-nucleon decays of
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76
Ge in the dataset from the GERmanium Detector Array (GERDA) experiment. Decays that populate excited levels of the daughter nucleus above the threshold for particle emission lead to disintegration and are not considered. The ppp-, ppn-, and pnn-decays lead to
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73
Cu,
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73
Zn, and
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73
Ga nuclei, respectively. These nuclei are unstable and eventually proceed by the beta decay of
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73
Ga to
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73
Ge (stable). We search for the
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73
Ga decay exploiting the fact that it dominantly populates the 66.7 keV
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73
m
Ga state with half-life of 0.5 s. The nnn-decays of
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76
Ge that proceed via
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73
m
Ge are also included in our analysis. We find no signal candidate and place a limit on the sum of the decay widths of the inclusive tri-nucleon decays that corresponds to a lower lifetime limit of 1.2
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×
10
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26
yr (90% credible interval). This result improves previous limits for tri-nucleon decays by one to three orders of magnitude.
An optimized digital shaping filter has been developed for the
Gerda
experiment which searches for neutrinoless double beta decay in
76
Ge. The
Gerda
Phase I energy calibration data have been ...reprocessed and an average improvement of 0.3 keV in energy resolution (FWHM) corresponding to 10 % at the
Q
value for
0
ν
β
β
decay in
76
Ge is obtained. This is possible thanks to the enhanced low-frequency noise rejection of this Zero Area Cusp (ZAC) signal shaping filter.
Time-resolved laser-induced incandescence (TR-LII) was applied for the determination of particle sizes during carbon-particle formation from supersaturated atomic carbon vapor that was generated by ...laser photolysis of carbon suboxide (C3O2) at room temperature. Thus, the solid carbon particles were formed under hydrogen-free conditions. The TR-LII technique was used for in situ size measurement of growing carbon particles and samples of final particles were analyzed by transmission electron microscopy (TEM). It was found that the particles grow to a final size of 4--12 nm within 0.02--1 ms. The properties of the obtained particles depend on the initial conditions in the reaction volume, i.e. concentration of carbon suboxide, pressure and type of gas diluter, photolysis wavelength, and laser pulse energy. The comparison of TR-LII and TEM particle sizing results yields information about the effective thermal energy accommodation coefficients for He, Ar, CO, and C3O2 molecules on carbon particles.
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