3,773 research outputs found
Anode-Coupled Readout for Light Collection in Liquid Argon TPCs
This paper will discuss a new method of signal read-out from photon detectors
in ultra-large, underground liquid argon time projection chambers. In this
design, the signal from the light collection system is coupled via capacitive
plates to the TPC wire-planes. This signal is then read out using the same
cabling and electronics as the charge information. This greatly benefits light
collection: it eliminates the need for an independent readout, substantially
reducing cost; It reduces the number of cables in the vapor region of the TPC
that can produce impurities; And it cuts down on the number of feed-throughs in
the cryostat wall that can cause heat-leaks and potential points of failure. We
present experimental results that demonstrate the sensitivity of a LArTPC wire
plane to photon detector signals. We also simulate the effect of a 1 s
shaping time and a 2 MHz sampling rate on these signals in the presence of
noise, and find that a single photoelectron timing resolution of 30 ns
can be achieved.Comment: 16 pages, 15 figure
Improved TPB-coated Light Guides for Liquid Argon TPC Light Detection Systems
Scintillation light produced in liquid argon (LAr) must be shifted from 128
nm to visible wavelengths in light detection systems used for liquid argon
time-projection chambers (LArTPCs). To date, LArTPC light collection systems
have employed tetraphenyl butadiene (TPB) coatings on photomultiplier tubes
(PMTs) or plates placed in front of the PMTs. Recently, a new approach using
TPB-coated light guides was proposed. In this paper, we report on light guides
with improved attenuation lengths above 100 cm when measured in air. This is an
important step in the development of meter-scale light guides for future
LArTPCs. Improvements come from using a new acrylic-based coating,
diamond-polished cast UV transmitting acrylic bars, and a hand-dipping
technique to coat the bars. We discuss a model for connecting bar response in
air to response in liquid argon and compare this to data taken in liquid argon.
The good agreement between the prediction of the model and the measured
response in liquid argon demonstrates that characterization in air is
sufficient for quality control of bar production. This model can be used in
simulations of light guides for future experiments.Comment: 25 pages, 20 figure
Image-potential states on clean and hydrogen-covered Pd surfaces: Analysis of a one-dimensional model
Theoretical calculations in a one-dimensional model give the energies of surface states on clean and hydrogen-covered Pd surfaces in very good agreement with those measured by high-resolution electron energy-loss spectroscopy and inverse photoemission experiments. Some general properties and the applicability of this class of one-dimensional models are discussed
Highly-ordered graphene for two dimensional electronics
With expanding interest in graphene-based electronics, it is crucial that
high quality graphene films be grown. Sublimation of Si from the 4H-SiC(0001)
Si-terminated) surface in ultrahigh vacuum is a demonstrated method to produce
epitaxial graphene sheets on a semiconductor. In this paper we show that
graphene grown from the SiC (C-terminated) surface are of higher
quality than those previously grown on SiC(0001). Graphene grown on the C-face
can have structural domain sizes more than three times larger than those grown
on the Si-face while at the same time reducing SiC substrate disorder from
sublimation by an order of magnitude.Comment: Submitted to Appl. Phys. Let
Adsorbate-substrate vibrational modes of benzene on Ag(110) resolved with scanning tunneling spectroscopy.
Ellipsometry investigation of nucleation and growth of electron cyclotron resonance plasma deposited silicon films
The nucleation and initial growth of Si films is fundamental to the understanding and control of rapid thermal chemical vapor deposition (RTCVD), and plasma enhanced CVD(PECVD) processes. Herein is reported the nucleation and growth of Si deposited on oxidized silicon wafers by electron cyclotron resonance (ECR) PECVD in the 600–700 °C temperature range, under low pressures, and using both in situspectroscopicellipsometry and single wavelength real‐time ellipsometry. An island growth and coalescence model is used to interpret the real‐time ellipsometry data. Initial nuclei distance and growth parameters are derived. Atomic force microscopy was used to observe the early stage of nucleation. In situspectroscopicellipsometry is used to measure the final Si film thicknesses and optical properties. The deposited Si films were characterized by cross‐sectional transmission electron microscopy
The photomultiplier tube calibration system of the MicroBooNE experiment
We report on the design and construction of a LED-based fiber calibration system for large liquid argon time projection detectors. This system was developed to calibrate the optical systems of the MicroBooNE experiment. As well as detailing the materials and installation procedure, we provide technical drawings and specifications so that the system may be easily replicated in future LArTPC detectors.National Science Foundation (U.S.) (Grant PHY-1205175
Unoccupied surface states on Pd(111) observed in very-low-energy electron diffraction and inverse photoemission: Theoretical interpretation
A three-dimensional calculation of projected electronic bulk and surface bands, spanning the energies studied by inverse photoemission and very-low-energy electron diffraction, reveals that the surface-electronic states observed by the two techniques are indeed two distinct states. We discuss their true character and the question of effective masses, and briefly comment on the validity of one-dimensional models
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