Compaction kinetics, structurization, and mechanical characteristics of ceramics based on zirconium boride during the combined addition of sintering activating carbon additives, tungsten boride, and ...zirconium and tungsten silicides into the system are investigated. It is shown that the efficient additives for ZrB
2
ceramics are tungsten silicide and boride, which allow not only reducing the sintering temperature and activating the ceramic compaction, but also provide the maximum strength of the samples. The shrinkage of activator-free ZrB
2
occurs in the restructuring of boride that sinters with the formation of an azimuth texture. It is established that these processes do not occur in the ceramics sintered with activators. When such processes are developing, the sintering occurs under the conditions of intensive grain-boundary phase interactions. The mechanical characteristics are studied mainly by the indentation method with the determination of a certain number of ceramic strength characteristics. The differences in the characteristics of ceramics produced by hot pressing in vacuum and by hot pressing in the CO–CO
2
atmosphere are studied. It is established that the grain-boundary strength of forming materials and their defective state show the greatest differences. The data obtained allow optimizing the production, composition, and structure of ceramics to ensure the necessary mechanical characteristics (compressive strength, tensile strength, bending strength, hardness, and fracture toughness).
The kinetics of sintering and phase interactions in the diffusion contact zones of Cr
3
C
2
and ZrB
2
are investigated. It is found that using Cr
3
C
2
as a sintering activator for ZrB
2
sintering ...reduces the hot pressing temperature from 2200°C to 1500–1750°C, depending on the Cr
3
C
2
content. The phase formation accompanied with the formation of new high-temperature refractory compounds, such as zirconium carboborides, chromium borides and carboborides, and zirconium-chromium carboborides, rapidly develops at the Cr
3
C
2
and ZrB
2
interface within the diffusion zone. An intense diffusion of chromium and carbon into zirconium diboride accompanied with the formation of nonporous states in zirconium diboride (to a depth of 50–100 μm at 1360°C) near diffusion contact zone is observed. It is established that the contact interaction during sintering in the diffusion zone results in the formation of the vanishing eutectic liquid phase, which is consumed to forming new high-refractory compounds (phases based on zirconium carbide and chromium borides).
We present the first direct search for lepton flavour violating muon decay mediated by a new light particle X,
μ
+
→
e
+
X
,
X
→
γ
γ
. This search uses a dataset resulting from
7.5
×
10
14
stopped ...muons collected by the MEG experiment at the Paul Scherrer Institut in the period 2009–2013. No significant excess is found in the mass region 20–45 MeV/c
2
for lifetimes below 40 ps, and we set the most stringent branching ratio upper limits in the mass region of 20–40 MeV/c
2
, down to
O
(
10
-
11
)
at 90% confidence level.
High-intensity secondary beams play a vital role in today’s particle physics and materials science research and require suitable detection techniques to adjust beam characteristics to optimally match ...experimental conditions. To this end we have developed a quasi-non-invasive, ultra-thin, CsI(Tl) luminophore foil detector system, based on CCD-imaging. We have used this to quantify the beam characteristics of an intensity-frontier surface muon beam used for next-generation charged lepton-flavour violation (cLFV) search experiments at the Paul Scherrer Institut (PSI) and to assess the possible use for a future High-intensity Muon Beam (HiMB-project), currently under study at PSI. An overview of the production and intrinsic characteristics of such foils is given and their application in a high-intensity beam environment.
COMET Phase-I technical design report Abramishvili, R; Adamov, G; Allin, A ...
Progress of theoretical and experimental physics,
03/2020, Letnik:
2020, Številka:
3
Journal Article
Recenzirano
Odprti dostop
Abstract
The Technical Design for the COMET Phase-I experiment is presented in this paper. COMET is an experiment at J-PARC, Japan, which will search for neutrinoless conversion of muons into ...electrons in the field of an aluminum nucleus ($\mu$–$e$ conversion, $\mu^{-}N \rightarrow e^{-}N$); a lepton flavor-violating process. The experimental sensitivity goal for this process in the Phase-I experiment is $3.1\times10^{-15}$, or 90% upper limit of a branching ratio of $7\times 10^{-15}$, which is a factor of 100 improvement over the existing limit. The expected number of background events is 0.032. To achieve the target sensitivity and background level, the 3.2 kW 8 GeV proton beam from J-PARC will be used. Two types of detectors, CyDet and StrECAL, will be used for detecting the $\mu$–$e$ conversion events, and for measuring the beam-related background events in view of the Phase-II experiment, respectively. Results from simulation on signal and background estimations are also described.
PDF
