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At least 865 records · Page 48
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Manual for the Jet Event and Background Simulation Library

Jets are the collimated streams of particles resulting from hard scattering in the initial state of high-energy collisions. In heavy-ion collisions, jets interact with the quark-gluon plasma (QGP) before freezeout, providing a probe into the internal structure and properties of the QGP. In order to study jets, background must be subtracted from the measured event, potentially introducing a bias. We aim to understand and quantify this subtraction bias. PYTHIA, a library to simulate pure jet events, is used to simulate a model for a signature with one pure jet (a photon) and one quenched jet, where all quenched particle momenta are reduced by a user-de ned constant fraction. Background for the event is simulated using multiplicity values generated by the TRENTO initial state model of heavy-ion collisions fed into a thermal model consisting of a 3-dimensional Boltzmann distribution for particle types and momenta. Data from the simulated events is used to train a statistical model, which computes a posterior distribution of the quench factor for a data set. The model was tested rst on pure jet events and then on full events including the background. This model will allow for a quantitative determination of biases induced by various methods of background subtraction.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Effect of pulsed hollow electron-lens operation on the proton beam core in LHC

Collimation with hollow electron beams is currently one of the most promising concepts for active halo control in the HL-LHC. In order to further increase the diffusion rates for a fast halo removal as e.g. desired before the squeeze, the electron lens (e-lens) can be operated in pulsed mode. In case of profile imperfections in the electron beam the pulsing of the e-lens induces noise on the proton beam which can, depending on the frequency content and strength, lead to emittance growth. In order to study the sensitivity to the pulsing pattern and the amplitude, a beam study (machine development MD) at the LHC has been proposed for August 2016 and we present in this note the preparatory simulations and estimates.

43 PARTICLE ACCELERATORS↗
DOE OSTI2017

TREAT HODOSCOPE – A Predictive Simulation Model

The Transient Reactor Test Facility (TREAT) reactor is being restarted after over two decades of standby operation. TREAT is designed to test the time-dependent behavior of nuclear fuel during simulated reactor accidents. One of the principle data collection systems of TREAT is the fast neutron hodoscope which is used to observe the motion of the fuel test specimen as it is being damaged, deformed, or melted over the course of the power transient. The hodoscope is a grid of ex-core collimator channels paired with a bank of fast neutron sensitive radiation detectors. These detectors have historically been calibrated using empirical methods utilizing measurement data from smaller power pulses. Given modern computational capabilities this work sets out to establish a predictive computational capability of the fast neutron flux field exiting the hodoscope to support these calibrations.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2017

Radiological Protection Studies for NGLS XTOD

The X-ray transport, optics and diagnostic system (XTOD) starts from the end of bending magnets sending electrons to the main dump and ends at the end wall separating the accelerator tunnel from the user experimental hall (hereafter referred as EH wall), as shown in Figure 1. Figure 1.a shows the general schematic and Figure 1.b shows the initial layout with possible shielding components. This document summarizes the extensive studies on the shielding and collimator system design necessary to meet the radiation protection requirements.

61 RADIATION PROTECTION AND DOSIMETRY↗
DOE OSTI2017

A Laboratory Astrophysical Jet to Study Canonical Flux Tubes

Understanding the interaction between plasma flows and magnetic fields remains a fundamental problem in plasma physics, with important applications to astrophysics, fusion energy, and advanced space propulsion. For example, flows are of primary importance in astrophysical jets even if it is not fully understood how jets become so long without becoming unstable. Theories for the origin of magnetic fields in the cosmos rely on flowing charged fluids that should generate magnetic fields, yet this remains to be demonstrated experimentally. Fusion energy reactors can be made smaller with flows that improve stability and confinement. Advanced space propulsion could be more efficient with collimated and stable plasma flows through magnetic nozzles but must eventually detach from the nozzle. In all these cases, there appears to be a spontaneous emergence of flowing and/or magnetic structures, suggesting a form of self-organization in plasmas. Beyond satisfying simple intellectual curiosity, understanding plasma self-organization could enable the development of methods to control plasma structures for fusion energy, space propulsion, and other applications. The research project has therefore built a theory and an experiment to investigate the interaction between magnetic fields and plasma flows. The theory is called canonical field theory for short, and the experiment is called Mochi after a rice cake filled with surprising, yet delicious fillings.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2018

Phase I (Final Report)

The focus of this proposal was the development of a new instrument capable of in-situ, spatially resolved, measurement of the energy spectra of ions in the edge of a tokamak plasma. The energy spectra of the ions determines the rates of sputtering and erosion of the plasma facing surfaces. The ion spectra in the edge is not easily determined spectroscopically and must be measured in situ since the ions are confined by the strong magnetic fields of the tokamak. Conventional energy analyzers are too large and expensive to install in multiple locations around the tokamak torus. The probes to be developed in this project are compact, low cost, and small enough to be placed inside of specially prepared wall tiles – essentially creating a “smart” plasma facing surface in a tokamak. Phase 1 of this project successfully demonstrated that two key elements of the instrument, the collimator and the energy analyzer, could be fabricated on a single silicon wafer and the combination functioned as designed when tested with an electron beam.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2018

Cross-Calibration of the GPS Constellation CXD Proton Data with GOES EPS [Slides]

The CXD provides good quality proton flux measurements across a range of proton energies. The data within the 1 st and 3 rd quartile range of the ratio of integral flux values is within 20 – 40%. While proton response of the CXD extends down to 6 MeV due to collimator holes in instrument filters, the > 10 MeV integral proton flux is not well captured as shown by the comparisons with EPS. We recommend that users of the data restrict their analysis to proton energies > 20 MeV. Although the full dataset is available now [https://www.ngdc.noaa.gov/stp/spaceweather/satellite-data/satellite-systems/gps/] this updated flux calculation is not present and so a reprocessing will commence soon and the dataset updated. These calibrated datasets will allow a number of exciting multipoint analyses such as more accurate probing of geomagnetic cutoffs as well as providing additional input to radiation belt climatology models such as AE9/AP9/SPM [Ginet et al., 2013].

58 GEOSCIENCES↗
DOE OSTI2018

A parameterized ray-tracing model for evaluation of hemispherical lensing of a uniform, telecentric object aperture -- performance improvement estimates for segmented scintillators with miniature lens arrays

A parametric model describing the collimation of radiation from a uniform circular aperture by a hemispherical lens of the same radius has been developed for rapid estimation of the potential benefit of miniature dielectric lens arrays in lens-coupled gamma ray cameras (GRCs) with segmented scintillators. A simplified ray-tracing approach is adopted that makes use of small angle approximations relevant to GRCs used in nuclear science at Los Alamos National Laboratory and elsewhere. Application of this analysis technique in a first-pass design optimization process results in the optimistic estimate that miniature lenses fabricated from typical optical quality glass might boost optical coupling by as much as a factor of 4 (6 dB gain). However, this is not likely to be economically attractive compared to other techniques, such as reduction of the GRC lens f-number.

47 OTHER INSTRUMENTATION↗
DOE OSTI2018

Mu2e Calorimeter Clustering Studies [Slides]

aMu2e (muon-to-electron-conversion), an Intensity Frontier experiment at Fermilab set to begin data taking in 2022, will search for flavor violation in charged leptons with a muon decaying to only an electron without any neutrinos. Protons will be accelerated by the 8GeV proton beam before reaching Mu2e’s production target. From there, pions enter an S-shaped Transport Solenoid and travel through a series of absorbers and collimators to select low-energy negatively charged muons from pion decay that will hit the stopping target. Downstream from the stopping target are a curved straw tracker and two annular disk crystal calorimeters. The signal will be a mono-energetic e- with an energy close to the rest mass of a muon. The Mu2e expected single event sensitivity is 2.87e-17. The complimentary trigger strategy will take advantage of both online track searches from the tracker and calorimeter reconstruction. The trigger requires a rejection factor greater than 100 and m ust make its decision within a 3ms time budget. In order to provide high efficiency on signal events, our calorimeter clustering algorithms must be accurate and meet the timing performance. I will discuss the expected performance of two clustering algorithms: a fast algorithm to be used at the trigger level and a more accurate clustering algorithm to be used in the offline reconstruction. The fast algorithm defines clusters by only selecting crystals adjacent to a high energy crystal seed. The full-blown algorithm can find smaller clusters separated from the main cluster, within a distance and timing window, and combine them into one cluster. We have analyzed the topology of the reconstructed clusters by the two algorithms on events with only a conversion electron and combined signal and background events. The goal of these studies is to improve the performance of the fast algorithm to better reconstruct the cluster energy and work within the strict timing budget.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

MD 2167: Effect of a resonant excitation on the evolution of the beam emittance and halo population

Collimation with hollow electron beams or lenses (HEL) is currently one of the most promising concepts for active halo control in HL-LHC. In previous studies it has been shown that the halo can be efficiently removed with a hollow electron lens. Equally important as an efficient removal of the halo, is to demonstrate that the core stays unperturbed. In the case of an ideal hollow electron lens without bends, the field at the location of the beam core vanishes and the core thus remains unperturbed. In reality, the field at the beam core does not vanish entirely due to imperfections in the electron beam profile and the electron lens bends necessary to guide the electron in and out of the proton aperture. In particular, in the case of a pulsed operation of the electron lens the non-vanishing residual field induces noise on the proton beam. To identify the most sensitive pulsing patterns for the resonant mode and derive tolerances on the profile imperfections, a first MD (MD1415) was carried out on 24.08.2016 [1] and a second MD on 17.09.2017. In this note we present the results of the second MD (MD2167), which focused on confirming a part of the results of the first MD and testing in addition a resonant excitation for which no effect on the beam core is expected and the effect of random uniform noise in addition.

43 PARTICLE ACCELERATORS↗
DOE OSTI2018

Proceedings of RIKEN BNL Research Center Workshop: The Definition of Jets in a Large Background

Jets, the collimated spray of particles produced by a high momentum quark or gluon, have been a key observable in high-energy particle and heavy ion physics. While in general, observables should be clearly defined with the same definition used in both theory and experiment, this has always been challenging for measurements of jets. Since the fragmentation of partons into final state hadrons is not calculable perturbatively and final state particles cannot be assigned unambiguously to particular partons, jet definitions rely on algorithms to reconstruct jets and select which particles are clustered into which jet. Defining a jet is particularly challenging when the jets are surrounded by particles from a high multiplicity underlying event such as those in heavy ion collisions, high luminosity proton-proton or electron-ion collisions. The community currently faces similar issues regarding jet definitions to those faced in particle physics in the preceding decades.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2017

Uncollided Flux Implementation for Discrete Ordinates Radiation Transport Solutions in Rattlesnake

Simulation of neutron streaming over long distances in optically thin narrow pipes sur- rounded by optically thicker materials that can absorb and/or scatter neutrons presents a simulation challenge to most neutron transport methods. Without sophisticated variance reduction techniques, this problem can be intractable for Monte Carlo techniques. Deterministic methods are often limited due to large angular discretization errors, this phenomenon is commonly known as ray effects. The uncollided component of the angular flux solution is the most anisotropic part and it can be difficult for discrete ordinate methods to accurately represent. The number of discrete angles required to overcome these ray effects is prohibitively large for the hodoscope configuration. Hence, other approaches must be taken to better simulate neutron streaming within the hodoscope collimator slots. In this report, we present an algorithm for semi-analytical calculation of the uncollided flux.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2017

Fuel Motion Monitoring System at TREAT – FY2017 Instrumentation Summary

This document is a report summarizing FY2017 efforts related to the Transient Reactor Test Facility (TREAT) Fuel Motion Monitoring System, "hodoscope," refurbishment campaign. TREAT is an air-cooled, graphite-moderated, heterogeneous test facility designed to evaluate reactor fuels and structural materials under conditions that simulate various types of transient overpower and under-cooling situations in a nuclear reactor. Fuel meltdowns, metal-water reactions, thermal interaction between overheated fuel and coolant, and the transient behavior of ceramic fuel for high-temperature systems can be studied. A key instrument that monitors fuel motion as these events take place is the fast neutron hodoscope. The hodoscope is designed to allow for pre-, during-, and post- transient imaging of fuel within a test loop in the center of the reactor core. The preferred technique for imaging is detection of fast neutrons produced by fission in the test fuel, travelling unmoderated through an empty row of core fuel assemblies and then through a multi-slot collimator to a 360-detector array. Due to the age of the instrument, a refurbishment of the hodoscope’s fast neutron detection capability is necessary to support real-time, fuel-position experimental data collection. One particular challenge in this regard is related to the refurbishment of the fast-neutron-sensing detector elements in the detector array. This report summarizes major activities and accomplishments related to the FMMS refurbishment in FY2017. Of particular note was work related to identifying options for new proton recoil scintillator wafer and initial examination of the TREAT proton recoil proportional counter detectors.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2018

Gamma-ray raster imaging with robotic data collection. FY18 report

This project has developed an alternative imaging capability for measuring radioactive materials in situ. This approach uses a robotic-mounted gamma-ray detector which can move around an area of interest, sampling the space at a high frequency. By rastering across the area, an image can be created with no collimation and a high efficiency. A regression model was developed to map out material distribution as the robot moves through the environment. An informative path planning algorithm was also developed to maximize the information collected throughout the movement path. The use of a robotic mount allows data collection for long periods of time unattended, and it will also eliminate uncertainties in positioning typically introduced by personnel. This approach will be particularly relevant for gloveboxes, shielded cells, or process piping which may have complex, non-uniform distributions of material.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2018

Using sound to ‘see’ through solid objects

To foil supervillains, Superman relies on his X-ray vision to see through shielded objects to expose dangerous items, such as explosives laced with kryptonite. At Los Alamos National Laboratory, a team of scientists in the Materials Synthesis and Integrated Devices group have invented a technology that works somewhat like Superman’s X-ray vision. Instead of eye beams, this new technology, known as ACCObeam (Acoustic Collimated Beam), uses a new type of sound beam to pierce through physical barriers such as cement, rock and metal and produce high-resolution images of what lies beyond, be it an explosive hidden in a suitcase or an unstable oil well deep in the earth that could fracture and collapse at any given moment.

42 ENGINEERING↗
DOE OSTI2018

LLE-Annual report input

In FY18, an LLNL/GA/Michigan University team carried out the project “Exploring pair plasmas and their applications” with 2 LBS shot days on OMEGA EP. The campaign used an EP short pulse beam to produce jets of electron-positron antimatter pairs while the 2nd short pulse beam was used to producing protons to diagnose the laser-target interactions. The experiments focused on 1) inhensing the pair yield using nano-structure targets and 2) collimating/focusing positron jets through curved sheath potential from shaped target surface. The experiments successfully demonstrated both the yield enhensement and the positron focusing. The data provided basis futrue experiments on labortary astrophysics using the pair jet – plasma interaction to drive beam instabilities. A total of 14 shots were performed in the fiscal year. The EP short pulse beams (~1 kJ in 10 ps) irradiated targets of 1 mm thick Au targets, with and without the nano-structure on the laser interaction surface. It was found that for the same laser energy, positron yields and acceleration both were increased dramatically by using nano-structure. This finding is important to the future experiments and applications using laser pair jets. Previous experiments used gold targets almost exclusively. It was also found that a hemispherical shaped backsurface can focuing the positron jets through the sheath field – like that observed in proton focusing. This observation is important as it demonstrated that higher pair density can be achieved by reducing their volume, which may enable the development of instablities predicted by theory. The prior experiments showed that quasi-monoenergetic relativistic positron jets are formed during high-intensity irradiation of thick gold targets, and that these jets can be strongly collimated using the magnetized-inertial fusion electrical delivery system (MIFEDS). The external field produces a 40-fold increase in the peak positron and electron signal [4]. The positron yield was found to scale as the square of the laser energy. The FY15 results revealed another dimension of scaling on the target materials. The favorable scaling would enable the laboratory study of relativistic pair plasmas that are important to understanding some of the most exotic and energetic systems in the universe.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2017

Effects of a long low-gap in-vacuum undulator on the impedance and beam lifetime

Possible installation of a long low-gap in-vacuum undulator in the NSLS-II storage ring could result in several impedance-related and beam lifetime issues. High impedance of the low-gap undulator can result in beam instabilities and beam-induced overheating of the undulator itself. These issues have been preliminary studied using analytical formulae, computer simulations and experience of operations with existing in-vacuum undulators. Depending on the device location, the minimum gap and the overall ring-average residual gas pressure, an in-vacuum undulator (IVU) may appreciably shorten the elastic gas scattering component of the beam lifetime. When the latter becomes comparable to the Touschek lifetime, a significant reduction of the total beam lifetime will occur. Here this effect is studied by applying some well-known analytical formulas, as well as insights from NSLS-II operating experience. Finally, the issue of IVU radiation damage also needs to be looked at, and potentially addressed with a dedicated collimation system.

36 MATERIALS SCIENCE↗
DOE OSTI2018

The CBETA Fractional Arc Test

As part of this development effort, the Cornell-BNL Energy recovery linac Test Accelerator (CBETA) [3], a 4-pass, 150 MeV energy recovery linac (ERL), utilizing a Non-scaling Fixed Field Alternating-gradient (NS-FFA) permanent magnet return loop, is currently under design and construction at Cornell University through the joint collaboration of Brookhaven National Lab (BNL) and the Cornell Laboratory for Accelerator based Sciences and Education (CLASSE). Building on the significant advancements in high-brightness photoelectron sources and SRF technology at Cornell, as well as the FFA magnet and lattice design expertise from BNL, CBETA will establish the operation of a multi-turn SRF based ERL utilizing a compact FFA return loop with large energy acceptance (a factor of roughly 3.6 in energy), and thus demonstrate one possible cost-reduction technology under consideration for the eRHIC design. Moreover, successful completion of the CBETA project requires the study and measurement of many critical phenomena relevant to designing the EIC: the Beam-Breakup (BBU) instability, halo-development and collimation, growth in energy spread from Coherent Synchrotron Radiation (CSR), and CSR micro bunching, and thus should provide valuable insight to the EIC and ERL communities. In order to demonstrate the viability of the CBETA design, the Fractional Arc Test (FAT) was added to the CBETA commissioning sequence.

43 PARTICLE ACCELERATORS↗