962 research outputs found
Using Pilot Systems to Execute Many Task Workloads on Supercomputers
High performance computing systems have historically been designed to support
applications comprised of mostly monolithic, single-job workloads. Pilot
systems decouple workload specification, resource selection, and task execution
via job placeholders and late-binding. Pilot systems help to satisfy the
resource requirements of workloads comprised of multiple tasks. RADICAL-Pilot
(RP) is a modular and extensible Python-based pilot system. In this paper we
describe RP's design, architecture and implementation, and characterize its
performance. RP is capable of spawning more than 100 tasks/second and supports
the steady-state execution of up to 16K concurrent tasks. RP can be used
stand-alone, as well as integrated with other application-level tools as a
runtime system
The Effects of Dissolved Methane upon Liquid Argon Scintillation Light
In this paper we report on measurements of the effects of dissolved methane
upon argon scintillation light. We monitor the light yield from an alpha source
held 20 cm from a cryogenic photomultiplier tube (PMT) assembly as methane is
injected into a high-purity liquid argon volume. We observe significant
suppression of the scintillation light yield by dissolved methane at the 10
part per billion (ppb) level. By examining the late scintillation light time
constant, we determine that this loss is caused by an absorption process and
also see some evidence of methane-induced scintillation quenching at higher
concentrations (50-100 ppb). Using a second PMT assembly we look for visible
re-emission features from the dissolved methane which have been reported in
gas-phase argon methane mixtures, and we find no evidence of visible
re-emission from liquid-phase argon methane mixtures at concentrations between
10 ppb and 0.1%.Comment: 18 pages, 11 figures Updated to match published versio
Beam instrumentation for the Tevatron Collider
The Tevatron in Collider Run II (2001-present) is operating with six times
more bunches and many times higher beam intensities and luminosities than in
Run I (1992-1995). Beam diagnostics were crucial for the machine start-up and
the never-ending luminosity upgrade campaign. We present the overall picture of
the Tevatron diagnostics development for Run II, outline machine needs for new
instrumentation, present several notable examples that led to Tevatron
performance improvements, and discuss the lessons for future colliders
New Science on the Open Science Grid
The Open Science Grid (OSG) includes work to enable new science, new
scientists, and new modalities in support of computationally based research.
There are frequently significant sociological and organizational changes
required in transformation from the existing to the new. OSG leverages its
deliverables to the large scale physics experiment member communities to
benefit new communities at all scales through activities in education,
engagement and the distributed facility. As a partner to the poster and
tutorial at SciDAC 2008, this paper gives both a brief general description and
some specific examples of new science enabled on the OSG. More information is
available at the OSG web site: (http://www.opensciencegrid.org)
Adapting SAM for CDF
The CDF and D0 experiments probe the high-energy frontier and as they do so
have accumulated hundreds of Terabytes of data on the way to petabytes of data
over the next two years. The experiments have made a commitment to use the
developing Grid based on the SAM system to handle these data. The D0 SAM has
been extended for use in CDF as common patterns of design emerged to meet the
similar requirements of these experiments. The process by which the merger was
achieved is explained with particular emphasis on lessons learned concerning
the database design patterns plus realization of the use cases.Comment: Talk from the 2003 Computing in High Energy and Nuclear Physics
(CHEP03), La Jolla, Ca, USA, March 2003, 4 pages, pdf format, TUAT00
Recommended from our members
Experience with MODSIM II
We present results of computer simulations for Data Acquisition systems for large fixed target experiments in an object oriented simulation language, MODSIM. This paper summarizes our experiences and presents preliminary results from the simulation already completed. We also indicate the resources required for this project
Observation of the Dependence of Scintillation from Nuclear Recoils in Liquid Argon on Drift Field
We have exposed a dual-phase Liquid Argon Time Projection Chamber (LAr-TPC)
to a low energy pulsed narrowband neutron beam, produced at the Notre Dame
Institute for Structure and Nuclear Astrophysics to study the scintillation
light yield of recoiling nuclei in a LAr-TPC. A liquid scintillation counter
was arranged to detect and identify neutrons scattered in the LAr-TPC target
and to select the energy of the recoiling nuclei.
We report the observation of a significant dependence on drift field of
liquid argon scintillation from nuclear recoils of 11 keV. This observation is
important because, to date, estimates of the sensitivity of noble liquid TPC
dark matter searches are based on the assumption that electric field has only a
small effect on the light yield from nuclear recoils.Comment: v3 updated to reflect published version, including a set of plots for
49.9 keV dat
Measurement of Scintillation and Ionization Yield and Scintillation Pulse Shape from Nuclear Recoils in Liquid Argon
We have measured the scintillation and ionization yield of recoiling nuclei
in liquid argon as a function of applied electric field by exposing a
dual-phase liquid argon time projection chamber (LAr-TPC) to a low energy
pulsed narrow band neutron beam produced at the Notre Dame Institute for
Structure and Nuclear Astrophysics. Liquid scintillation counters were arranged
to detect and identify neutrons scattered in the TPC and to select the energy
of the recoiling nuclei. We report measurements of the scintillation yields for
nuclear recoils with energies from 10.3 to 57.3 keV and for median applied
electric fields from 0 to 970 V/cm. For the ionization yields, we report
measurements from 16.9 to 57.3 keV and for electric fields from 96.4 to 486
V/cm. We also report the observation of an anticorrelation between
scintillation and ionization from nuclear recoils, which is similar to the
anticorrelation between scintillation and ionization from electron recoils.
Assuming that the energy loss partitions into excitons and ion pairs from
Kr internal conversion electrons is comparable to that from Bi
conversion electrons, we obtained the numbers of excitons () and ion
pairs () and their ratio () produced by nuclear recoils from
16.9 to 57.3 keV. Motivated by arguments suggesting direction sensitivity in
LAr-TPC signals due to columnar recombination, a comparison of the light and
charge yield of recoils parallel and perpendicular to the applied electric
field is presented for the first time.Comment: v2 to reflect published versio
A Regenerable Filter for Liquid Argon Purification
A filter system for removing electronegative impurities from liquid argon is
described. The active components of the filter are adsorbing molecular sieve
and activated-copper-coated alumina granules. The system is capable of
purifying liquid argon to an oxygen-equivalent impurity concentration of better
than 30 parts per trillion, corresponding to an electron drift lifetime of at
least 10 ms. Reduction reactions that occur at about 250 degrees Celsius allow
the filter material to be regenerated in-situ through a simple procedure. In
the following work we describe the filter design, performance, and regeneration
process.Comment: 12 pages with 9 figure
- …