1,166 research outputs found
Radiation Hardness tests with neutron flux on different Silicon photomultiplier devices
Radiation hardness is an important requirement for solid state readout
devices operating in high radiation environments common in particle physics
experiments. The MEGII experiment, at PSI, Switzerland, investigates the
forbidden decay . Exploiting the most intense
muon beam of the world. A significant flux of non-thermal neutrons (kinetic
energy ) is present in the experimental hall produced along
the beamline and in the hall itself. We present the effects of neutron fluxes
comparable to the MEGII expected doses on several Silicon PhotoMulitpliers
(SiPMs). The tested models are: AdvanSiD ASD-NUV3S-P50 (used in MEGII
experiment), AdvanSiD ASD-NUV3S-P40, AdvanSiD ASD-RGB3S-P40, Hamamatsu and
Excelitas C30742-33-050-X. The neutron source is the thermal Sub-critical
Multiplication complex (SM1) moderated with water, located at the University of
Pavia (Italy). We report the change of SiPMs most important electric
parameters: dark current, dark pulse frequency, gain, direct bias resistance,
as a function of the integrated neutron fluency.Comment: 9 pages, 6 figures. Proceedings from Instrumentation for colliding
Beam Physics (INSTR-17) 27-02-2017/03-03-2017 Novosibirsk (R
Coherent States Expectation Values as Semiclassical Trajectories
We study the time evolution of the expectation value of the anharmonic
oscillator coordinate in a coherent state as a toy model for understanding the
semiclassical solutions in quantum field theory. By using the deformation
quantization techniques, we show that the coherent state expectation value can
be expanded in powers of such that the zeroth-order term is a classical
solution while the first-order correction is given as a phase-space Laplacian
acting on the classical solution. This is then compared to the effective action
solution for the one-dimensional \f^4 perturbative quantum field theory. We
find an agreement up to the order \l\hbar, where \l is the coupling
constant, while at the order \l^2 \hbar there is a disagreement. Hence the
coherent state expectation values define an alternative semiclassical dynamics
to that of the effective action. The coherent state semiclassical trajectories
are exactly computable and they can coincide with the effective action
trajectories in the case of two-dimensional integrable field theories.Comment: 20 pages, no figure
Carrapato e vermes: inimigos do gado e do produtor.
bitstream/item/65290/1/CT-95-Carrapato-e-vermes.pd
Improving the Time Resolution of Large-Area LaBr3:Ce Detectors with SiPM Array Readout
LaBr3:Ce crystals have good scintillation properties for X-ray spectroscopy.
Initially, they were introduced for radiation imaging in medical physics with
either a photomultiplier or SiPM readout, and they found extensive applications
in homeland security and gamma-ray astronomy. We used 1 inch round LaBr3:Ce
crystals to realize compact detectors with the SiPM array readout. The aim was
a good energy resolution and a fast time response to detect low-energy X-rays
around 100 keV. A natural application was found inside the FAMU experiment, at
RIKEN RAL. Its aim is a precise measurement of the proton Zemach radius with
impinging muons, to contribute to the solution to the so-called proton radius
puzzle. Signals to be detected are characteristic X-rays around 130 KeV. A
limit for this type of detector, as compared to the ones with a photomultiplier
readout, is its poorer timing characteristics due to the large capacity of the
SiPM arrays used. In particular, long signal falltimes are a problem in
experiments such as FAMU, where a prompt background component must be separated
from a delayed one (after 600 ns) in the signal X-rays to be detected.
Dedicated studies were pursued to improve the timing characteristics of the
used detectors, starting from hybrid ganging of SiPM cells; then developing a
suitable zero pole circuit with a parallel ganging, where an increased
overvoltage for the SiPM array was used to compensate for the signal decrease;
and finally designing ad hoc electronics to split the 1 inch detector SiPM
array into four quadrants, thus reducing the involved capacitances. The aim was
to improve the detectors timing characteristics, especially falltime, while
keeping a good FWHM energy resolution for low-energy X-ray detection
Carrapato dos bovinos: controle estratégico nas diferentes regiões brasileiras.
bitstream/item/65401/1/COT-36-Carrapato-dos-bovinos.pd
Studies on the biodistribution of dextrin nanoparticles
The characterization of biodistribution is a central requirement in the development of biomedical applications based on the use of nanoparticles, in particular for controlled drug delivery. The blood circulation time, organ biodistribution and rate of excretion must be well characterized in the process of product development. In this work, the biodistribution of recently developed self-assembled dextrin nanoparticles is addressed. Functionalization of the dextrin nanoparticles with a DOTA-monoamide-type metal chelator, via click chemistry, is described. The metal chelator-functionalized nanoparticles were labeled with the ᵧ-emitting 153Sm3+ radioisotope and the blood clearance rate and organ biodistribution of the nanoparticles were obtained. The effect of PEG surface coating on the blood clearance rate and organ biodistribution of the nanoparticles was also studied.The authors wish to acknowledge funding through the FCT/POCTI programme (project PTDC/QUI/70063/2006)
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