40 research outputs found
Unraveling Fano noise and partial charge collection effect in X-ray spectra below 1 keV
Fano noise, readout noise, and the partial charge collection (PCC) effect
collectively contribute to the degradation of energy spectra in Charge Coupled
Devices (CCD) measurements, especially at low energies. In this work, the X-ray
produced by the fluorescence of fluorine (677 eV) and aluminum (1486 eV) were
recorded using a Skipper-CCD, which enabled the reading noise to be reduced to
0.2 e-. Based on an analytical description of photopeak shapes resulting from
the convolution of the PCC effect and Fano noise, we achieved a precise
characterization of the energy spectra. This description enabled us to
disentangle and quantify the contributions from both Fano noise and the PCC
effect. As a result, we determined the Fano factor and the electron-hole pair
creation energy. Additionally, we estimated the PCC-region of the sensor and,
for the first time, experimentally observed the expected skewness of photopeaks
at low energies.Comment: 8 pages, 5 figure
SENSEI: Characterization of Single-Electron Events Using a Skipper-CCD
We use a science-grade Skipper Charge Coupled Device (Skipper-CCD) operating
in a low-radiation background environment to develop a semi-empirical model
that characterizes the origin of single-electron events in CCDs. We identify,
separate, and quantify three independent contributions to the single-electron
events, which were previously bundled together and classified as ``dark
counts'': dark current, amplifier light, and spurious charge. We measure a dark
current, which depends on exposure, of (5.89+-0.77)x10^-4 e-/pix/day, and an
unprecedentedly low spurious charge contribution of (1.52+-0.07)x10^-4 e-/pix,
which is exposure-independent. In addition, we provide a technique to study
events produced by light emitted from the amplifier, which allows the
detector's operation to be optimized to minimize this effect to a level below
the dark-current contribution. Our accurate characterization of the
single-electron events allows one to greatly extend the sensitivity of
experiments searching for dark matter or coherent neutrino scattering.
Moreover, an accurate understanding of the origin of single-electron events is
critical to further progress in ongoing R&D efforts of Skipper and conventional
CCDs.Comment: 9 pages, 6 figures, 4 table
Preceptoria em Medicina de Família e Comunidade: desafios e realizações em uma Atenção Primária à Saúde em construção
Preceptoria Médica em Serviço de Emergência e Urgência Hospitalar na Perspectiva de Médicos
A construção de um ambiente virtual de aprendizagem para educação a distância: uma estratégia educativa em serviço
Skipper-CCD Sensors for the Oscura Experiment: Requirements and Preliminary Tests
Oscura is a proposed multi-kg skipper-CCD experiment designed for a dark
matter (DM) direct detection search that will reach unprecedented sensitivity
to sub-GeV DM-electron interactions with its 10 kg detector array. Oscura is
planning to operate at SNOLAB with 2070 m overburden, and aims to reach a
background goal of less than one event in each electron bin in the 2-10
electron ionization-signal region for the full 30 kg-year exposure, with a
radiation background rate of 0.01 dru. In order to achieve this goal, Oscura
must address each potential source of background events, including instrumental
backgrounds. In this work, we discuss the main instrumental background sources
and the strategy to control them, establishing a set of constraints on the
sensors' performance parameters. We present results from the tests of the first
fabricated Oscura prototype sensors, evaluate their performance in the context
of the established constraints and estimate the Oscura instrumental background
based on these results
Early Science with the Oscura Integration Test
Oscura is a planned light-dark matter search experiment using Skipper-CCDs
with a total active mass of 10 kg. As part of the detector development, the
collaboration plans to build the Oscura Integration Test (OIT), an engineering
test experiment with 10% of the Oscura's total mass. Here we discuss the early
science opportunities with the OIT to search for millicharged particles (mCPs)
using the NuMI beam at Fermilab. mCPs would be produced at low energies through
photon-mediated processes from decays of scalar, pseudoscalar, and vector
mesons, or direct Drell-Yan productions. Estimates show that the OIT would be a
world-leading probe for low-mass mCPs.Comment: 21 pages, 13 figure