Search

An analysis of publications related to high energy physics computing in refereed journals is presented. The distribution of papers associated to various fields of computing relevant to high energy physics is critically analyzed. The relative publication rate of software papers is evaluated in comparison to other closely related physics disciplines, such as nuclear physics, radiation protection and medical physics, and to hardware publications. The results hint to the fact that, in spite of the significant effort invested in high energy physics computing and its fundamental role in the experiments, this research area is underrepresented in scientific literature; nevertheless the analysis of citations highlights the significant impact of software publications in experimental research.

We describe the design optimization process and performance characterization of a next generation neutron telescope, with imaging and energy measurement capabilities, sensitive to neutrons in the 1-20 MeV energy range. The response of the fast neutron imaging telescope (FNIT), its efficiency in neutron detection, energy resolution and imaging capabilities were characterized through a combination of lab tests and Monte Carlo simulations. Monte Carlo simulations, together with experimental data, are also being used in the development and testing of the image reconstruction algorithm. FNIT was initially conceived to study solar neutrons as a candidate instrument for the inner heliosphere sentinel (IHS) spacecraft. However, the design of this detector was eventually adapted to locate special nuclear material (SNM) sources for homeland security purposes, by detecting fission neutrons. In either case, the detection principle is based on multiple elastic neutron-proton scatterings in organic scintillator. By reconstructing event locations and measuring the recoil proton energies, the direction and energy spectrum of the primary neutron flux can be determined and neutron sources identified. This paper presents the most recent results arising from our efforts and outlines the performance of the FNIT detector.

The US Department of Energy's transuranic (TRU) waste inventory includes about 4,500 m3 of remote-handled TRU (RH-TRU) wastes composed of a variety of containerized waste forms having a contact surface dose rate that exceeds 2 mSv/hr (200 mrem/hr) containing waste materials with a total TRU concentration greater than 3700 Bq/g (100 nCi/g). As part of a research project to investigate the use of active Compton-suppressed room-temperature gamma-ray detectors for direct non-destructive quantification of the TRU content of these RH-TRU wastes, we have designed and purchased a unique detector system using a LaBr3(Ce) primary detector and a Nal(Tl) suppression mantle. The LaBr3(Ce) primary detector is a cylindrical unit ~25 mm in diameter by 76 mm long viewed by a 38 mm diameter photomultiplier. The Nal(Tl) suppression mantle (secondary detector) is 175 mm by 175 mm with a center well that accommodates the primary detector. An important feature of this arrangement is the lack of any "can" between the primary and secondary detectors. These primary and secondary detectors are optically isolated by a thin layer (.003") of aluminized Kapton. This arrangement virtually eliminates the "dead" material between the primary and secondary detectors, a feature that preliminary modeling indicated would substantially improve the Compton suppression capability of this device. This paper presents both the expected performance of this unit determined from modeling with MCNPX, and the performance measured in our laboratory with radioactive sources.

The ATLAS experiment is getting ready to observe collisions between protons at a centre of mass energy of 14 TeV. These will be the highest energy collisions in a controlled environment to-date, to be provided by the Large Hadron Collider at CERN by mid 2008. The ATLAS Trigger and Data Acquisition (TDAQ) system selects events online in a three level trigger system in order to keep those events promising to unveil new physics at a budgeted rate of ~200 Hz for an event size of ~1.5 MB. This corresponds to a reduction of O(10^5) from the initial bunch-crossing rate of 40 MHz at nominal operating conditions. This paper focuses on the data-logging system on the TDAQ side, the so-called "Sub-Farm Output" (SFO) system. It takes data from the Event Filter farm, which is the third level trigger, and it streams and indexes the events into different files, according to each event's trigger path. The data files are moved to CASTOR, the central mass storage facility at CERN. The final TDAQ data-logging system has been installed using 6 Linux PCs, holding 24 disks of 500 GB each, managed by three RAID controllers on each PC. The data-writing is managed in a controlled round-robin way among three independent filesystems associated to a distinct set of disks, managed by a distinct RAID controller. This design allows fast I/O, which together with a high speed network permits to minimize the number of SFO nodes. We report here on the functionality and performance requirements on the system, our experience with commissioning it and on the performance achieved.

Very high resolution images can be achieved in small animal PET systems utilizing solid state silicon pad detectors. In such systems with sub-millimeter intrinsic resolutions, the range of the positron is becoming the dominant contribution to image blur. The size of the positron range effect depends on the initial positron energy and hence the radioactive tracer used. For higher energy positron emitters, such as 68Ga and 94mTc which are gaining importance in small animal studies, the width of the annihilation point distribution dominates the spatial resolution. This positron range effect can be reduced by embedding the field of view of the PET scanner in a strong magnetic field. In order to confirm this effect experimentally we have developed a high resolution PET instrument based on silicon pad detectors that can operate in a 7 T magnetic field. In this paper we present the preliminary results of a study of the effects of magnetic fields up to 7 T on PET image resolution for 22Na and 68Ga point sources.

The Italian silicon-detectors-with-low-interaction-with material collaboration (SLIM5) has designed, fabricated and tested several prototypes of CMOS monolithic active pixel sensors (MAPS). This paper shows the design of a new mixed-mode chip prototype composed of a bidimensional matrix of pixels, and of an off-pixel digital readout sparsification circuit. The readout logic is based on commercial standard cells and implements an optimized non token readout technique. Also, a MAPS emulator software toool is presented. The project is aimed at overcoming the readout speed limit of future large-matrix pixel detectors for particle tracking, by matching the requirements of future high-energy physics experiments. The readout architecture extends the flexibility of the MAPS devices to be also used in first level triggers on tracks in vertex detectors.

The frequency-distance principle (FDP) is a well-known relationship that relates the distance between the object and the detector to the slope in the two-dimensional Fourier transform of the projection sinogram. This relationship has been previously applied to compensation of the distance dependent collimator blurring in SPECT (single photon emission computed tomography) in the literature. This paper makes an attempt to use the FDP to correct for uniform attenuation in SPECT. Computer simulations reveal that this technique works well for objects consisting of point sources but does not work well for distributed objects.