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At least 829 records · Page 46
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Commissioning and First Results of the Electron Beam Profiler in the Main Injector at Fermilab

The planned neutrino program at Fermilab requires large proton beam intensities in excess of 2 MW. Measuring the transverse profiles of these high intensity beams is challenging and often depends on non-invasive techniques. One such technique involves measuring the deflection of a probe beam of electrons with a trajectory perpendicular to the proton beam. A device such as this is already in use at the Spallation Neutron Source at ORNL and a similar device has been installed in the Main Injector at Fermilab. Commissioning of the device is in progress with the goal of having it operational by the end of the year. The status of the commissioning and initial results will be presented

Thurman-Keup, R.↗
DOE OSTI2017

Laser System Design and Operation for SNS H- Beam Laser Stripping

Recently, a high-efficiency laser assisted hydrogen ion (H-) beam stripping was successfully carried out in the Spallation Neutron Source (SNS) accelerator. The experiment was not only an important step toward foil-less H- stripping for charge exchange injection, it also served as a first example of using megawatt ultraviolet (UV) laser in an operational high power proton accelerator facility. This talk reports the design, implementation, and commissioning results of the macropulse laser system, laser transport line, and laser operation for the laser stripping experiment. The macropulse laser consists of a mode-locked picosecond pulsed seed laser and a burst-mode Nd:YAG laser amplifier. The general design concept can be adapted to any temporal beam structures in most accelerators. We have achieved UV pulses with the pulse widths varying between 34 to 54 ps and a maximum peak power over 3.5 MW. A laser transport line is installed to deliver the UV beam to the laser stripping chamber at a transmission efficiency of 70%. Laser operation including remote control and monitor of laser parameters will be described.

Liu, Yun↗
DOE OSTI2015

Commissioning and operation of the horizontal test apparatus at SNS

The Spallation Neutron Source (SNS) at Oak Ridge National Lab (ORNL) has built, commissioned and operated a Horizontal Test Apparatus (HTA) vessel in the Radiofrequency Test Facility (RFTF) test cave. It can be operated at 4.5 K using the independent Cryogenic Test Facility (CTF). The HTA is designed to be a single cavity version of an SNS cryomodule with the ability to demount and replace the cavity. It provides the functionality for testing a single dressed SNS medium or high beta Superconducting Radiofrequency (SRF) cavity. The HTA is currently being used in support of R&D for in-situ plasma processing of the cavity's inner niobium surface. The design and commissioning of the HTA at 4.5 K will be presented as well as results from operating the HTA including cool-down, warm-up and steady state operations. Results from plasma processing a warm SCRF cavity in-between cold HTA tests will also be reported.

Kim, Sang-Ho↗
DOE OSTI2017

Calculations vs. Measurements for Remnant Dose Rates from SNS Spent Structures

The Spallation Neutron Source (SNS) in Oak Ridge, Tennessee, is an accelerator driven neutron scattering facility for materials research. Presently SNS is capable to operate at 1.4 MW proton beam power incident on a mercury target with a proton beam energy of 1 GeV and 60 Hz repetition rate. SNS target system components are periodically replaced because they reach their end-of-life due to radiation induced material damage. Target vessel, which houses mercury target, is exchanged about two-three times per year and the proton beam window (PBW) is exchanged every two – three years.Each spent structure that leaves the SNS site requires supporting documentation with radionuclide inventory and dose rate prediction for the time of the transportation. Neutronics analyses are performed, assuming realistic irradiation history and decay case to ensure that the container/package, housing the structure, is compliant with the waste management regulations. Analyses are complex due to geometry, multi-code usage and following data treatment.To validate analyses, measurements of dose rates from the spent target vessel # 13 and PBW module #5 were performed. Neutronics analyses were performed to calculate residual dose rates from both structures for the time of measurements.

Popova, Irina I.↗
DOE OSTI2018

Analyses to support waste disposition of SNS Inner Reflector Plug

The Spallation Neutron Source Inner Reflector Plug (IRP) is scheduled for replacement. It reached end of life-time because of moderator neutron poison and decoupler burn-out, which is used for shaping neutron pulses. The replacement of IRP is a complex task due to its location in the area receiving high irradiation, being under significant amount of shielding, and size, which requires removal in segments. In order to support the disposal of spent IRP, waste characterization analyses are performed. These analyses include an accurate estimate of the radionuclide inventory and the residual dose rate. Using this data, the package class is determined for the and appropriate containers for temporary storage and subsequent transport are assigned. Analyses are performed in four steps: a radiation transport analysis of the radiation environment for producing the flux and isotope production information using MCNPX, a multi-cell transmutation analysis based n CINDER90, the generation of decay gamma source terms, and the gamma transport analyses of the decay gammas arriving at residual dose rates again using MCNPX. . Due to the complexity of the geometry of the lower segment, transport analyses for the residual dose rate require elaborate work for the source terms definition.

Popova, Irina I.↗
DOE OSTI2017

Investigating the Electromechanical Response Mechanism of Ionic Block Copolymers

One of the rapidly developing frontiers in research and engineering applications is focused on the rational design of materials that have targeted functionalities and tunable responses to external stimuli. Such materials stand to revolutionize how structural components are designed for applications including flexible electronics, biomimetic devices, nanofluidics, as well as separation chemistry. A chief obstacle to achieving this capability is the lack of a fundamental understanding of how chemical structure and morphology give rise to macromolecular properties. With this in mind, our research explores how polymer structure, counterion species, and film morphology affects the electromechanical response of materials when exposed to external electric fields. While the actuating behavior of materials such as Nafion have been commonly investigated, the literature lacks a thorough understanding of how the aforementioned factors drive the electrostatic and mechanical stresses that result in material deformation. Our research has investigated how thin film morphology and counterion species affect the electromechanical response of diblock copolymers containing charged imidazolium groups using neutron reflectometry. The sensitivity of neutron reflectometry to scattering length density as well as sub-nanometer changes in thickness make it an ideal tool for investigating polymer and counterion mobility under applied fields. To this end, we have designed a vacuum chamber capable of applying electric fields to thin films during reflectometry measurements. This chamber was used at the liquids reflectometer (BL-4B) at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL) to explore the electromechanical response of ionic block copolymers.

Dugger, Jason W.↗
DOE OSTI2018

MONTE CARLO NEUTRONICS ANALYSIS OF THE SNS STS MONOLITH

Neutronics analysis for the Oak Ridge National Laboratory Spallation Neutron Source second target station monolith conceptual design was performed entirely with the Monte Carlo method. It has been demonstrated that even though the monolith provides ~peta-scale attenuation of the dose rates, Monte Carlo simulations are within reach of computing capabilities of relatively inexpensive Linux clusters. Several monolith configurations achieved or exceeded design requirements and provide basis for the final design.

Remec, Igor↗
DOE OSTI2017

6D Phase Space Measurement of Low Energy, High Intensity Hadron Beam

The goal of this project is to demonstrate a method for measuring the full 6D phase space of an low energy, high intensity hadron beam. This is done by combining 4D emittance measurement techniques along with dispersion measurement and a beam shape monitor to provide the energy and phase space components. The measurement will be performed on new Beam Testing Facility (BTF) at the Spallation Neutron Source (SNS), a 2.5 MeV functional duplicate of the SNS accelerator front end.

Cathey, Brandon↗
DOE OSTI2017

6D Phase Space Measurement of Low Energy, High Intensity Hadron Beam

The goal of this experiment is to measure the full 6D phase space of a low energy, high intensity hadron beam. We use 4D emittance measurement techniques for the transverse plane combined with dispersion measurement and a beam shape monitor to provide the longitudinal phase space. The Beam Testing Facility (BTF) at the Spallation Neutron Source (SNS), a 2.5 MeV functional duplicate front end of the SNS accelerator is being used to facilitate the measurement. Early 6D measurements will be presented.

Cathey, Brandon↗
DOE OSTI2018

Technical Workings of the 6D Phase Measurement at SNS

The Beam Test Facility (BTF) is a functional duplicate of the Spallation Neutron Source (SNS) frontend with a 2.5 MeV beam on which the first six-dimensional phase space measurement has been completed. This presentation will show the technical underpinnings involved in performing the 6D scan with the BTF. The first part will examine the diagnostic setup involving apertures, a screen, and a bunch shape monitor and how the integrated system functions. The next part will cover the scan logic used in the software. The last part will briefly discuss ongoing efforts to analyze 6D measurements and identify correlations.

Cathey, Brandon↗
DOE OSTI2018

DOSE RATE VERIFICATION FOR SNS SPENT STRUCTURES

Residual dose rate measurements were conducted on two Spallation Neutron Source spent structures, target vessel #13 and proton beam window #5, after extraction from their service locations. These measurements were used to verify calculation methods for radionuclide inventory assessment that are typically performed for nuclear waste characterization and transportation. Neutronics analyses for predicting residual dose rates were carried out using complex and rigorous geometric models of the structures and their surroundings. Calculational results were analyzed and compared to the measured dose rates

Popova, Irina I.↗
DOE OSTI2019

Optimizing Room Temperature RF Structures for Accelerator Driven System Operations

Minimizing beam trip rates is one of the key operational goals at the Spallation Neutron Source (SNS). Trip rates are closely monitored, and real-time statistics are kept during beam operations for immediate analysis. Beam trips are automatically binned by the length of the trip along with the cause for each trip. The shortest beam trips occur with the highest frequency and those trip rates are dominated by the room temperature RF structures. There can be many causes for the RF structure malfunctions, but one area that has had a major impact on trip rates is improvement in how RF processing is done on structures after extended maintenance periods. Details about the improvement in RF conditioning will be discussed.

Brown, David↗
DOE OSTI2013

A SUITE OF SNS NEUTRON INSTRUMENT MODELS

MCSTAS models of the Spallation Neutron Source (SNS) neutron scattering instruments are being developed in a unified approach. Models aid performance assessment of the instruments, diagnosis of the component setup, and provide a tool for experiment planning and evaluation for the user community. The MCSTAS code has become a standard tool for neutron optics simulations in the neutron scattering community. Neutrons are tracked through the instrument model starting from moderator emission profiles through beam shaping components to the scattering at the sample and neutron detection. Models for the POWGEN, TOPAZ, VULCAN, and NOMAD instruments were completed utilizing as-built information as much as possible. Simulation results with the models are validated with measured data. While measurements and simulations of the neutron spectra incident to the sample location can agree within 10%, as for VULCAN, discrepancies have been identified for POWGEN and TOPAZ that indicate misalignment of components as neutron guide segments. Ideally, these misalignments are traced down and corrected as found.

Geoghegan, Ceris↗
DOE OSTI2019

Characterization and Modeling of High-Intensity Evolution in the SNS Beam Test Facility

Modern high-power accelerators are charged with delivering reliable beam with low losses. Resolving the complex dynamics arising from space charge and nonlinear forces requires detailed models of the accelerator and particle-in-cell simulation. There has historically been discrepancy between simulated and measured beam distributions, particularly at the low-density halo level. The Beam Test Facility (BTF) at the Spallation Neutron Source is outfitted to study beam evolution in a high-power linear accelerator MEBT. This includes capability for high-dimensional measurements of the post-RFQ beam distribution, including interplane correlations that may be the key to accurate simulation. Beam is transported through a 4.6 m FODO channel (9.5 cells) to a second distribution measurement stage. Plans for validating simulations against BTF measurements of beam evolution in the FODO channel are discussed.

Ruisard, Kiersten↗
DOE OSTI2020

Control System Plans for SNS Upgrade Projects

The Spallation Neutron Source at Oak Ridge National Laboratory is planning two major upgrades to the facility. The Proton Power Upgrade project, currently underway, will double the machine power from 1.4 to 2.8 MW by adding seven additional cryomodules and associated equipment. The Second Target Station project, currently in conceptual design, will construct a new target station effectively doubling the potential scientific output of the facility. This paper discusses the control system upgrades required to integrate these projects into the existing EPICS based control systems used for the machine and neutron instrument beamlines. While much of the control system can be replicated from existing solutions, some systems require new hardware and software. Operating two target stations simultaneously will require a new run permit system to safely manage beam delivery.

Hartman, Steven↗
DOE OSTI2017

Pulse Generator for Beam Deflector at the SNS Beam Test Facility

A new Beam Test Facility (BTF) has been built at the Spallation Neutron Source (SNS). It contains an ion source, Low Energy Beam Transport (LEBT) system, and a new Radio Frequency Quadrupole (RFQ) cavity. To determine the transmission losses of the ion beam through the RFQ, beam currents at RFQ input and output have to be measured. Input current measurements can be performed with an electrostatic deflector within the LEBT to displace the beam to a current pick up sensor located radially outward from the beam axis. A new pulse generator has been designed and built at the SNS to produce up to 6 kV pulses, with a pulse width of 1 to 10 usec at a repetition frequency of 10 Hz into the capacitive load to create the appropriate deflecting electrical field. This paper will review the beam deflector system; describe the new pulse generator and its performance, and present preliminary results of the beam transmission measurements.

Peplov, Vladimir↗
DOE OSTI2019

Target Control and Protection Systems Lessons from SNS Operations

The Spallation Neutron Source (SNS) at Oak Ridge National Laboratory has been in operations since 2006 and proposes a project to build a Second Target Station (STS) to effectively double potential scientific output. The SNS target controls operate in a harsh environment which includes high radiation, exposure to gaseous radionuclides, and activated liquid mercury and mercury vapor. These conditions necessitate protective interlocks and credited controls for protection functions to ensure proper response to off-normal conditions. In order to inform the design of target controls for the STS, we have examined lessons learned during SNS operations regarding the design and implementation of the control and protection systems for the first target station (FTS). This paper will examine various aspects of the performance of the target control and protection systems including reliability, maintainability and sustainability given the challenging environment created by 1.4 MW operations. Specific topics include distributed control of various target subsystems, response to loss of power, selection of nuclear grade instrumentation, and applying these lessons to the design for the STS project.

Humphreys, Dana↗
DOE OSTI2019

SNS Credited Pulse Energy Limit System Conceptual Design

The Controls Group at the Spallation Neutron Source (SNS) is designing a programmable signal processor based credited safety control that calculates pulsed beam energy based on beam kinetic energy and charge. The SNS Pulsed Energy Limit System (SPELS) must reli-ably shut off the beam if the average power exceeds 2.145 MW averaged over 60 seconds. This paper will cover the architecture and design choices needed to develop the system under the auspices of a programma-ble radiation-safety credit control. The authors will also introduce the concept of a graded failure approach that allows the credited system to continue operation in the presence of some faults.

Deibele, Craig↗