Search NASA⌕ Search

SEARCH · Search NASA

Results for “labs facilities”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Positron beams at Ce+BAF

Positron beams would provide a new and meaningful probe for the experimental program at the Thomas Jefferson National Accelerator Facility (JLab). The JLab Positron Working Group, formed in 2018 and now with over 250 members from 75 institutions, continues to develop an experimental program with high duty-cycle positron beams including but not limited to future hadronic physics and dark matter experiments. Critical requirements involve generating positron beams with a high degree of spin polarization, sufficient intensity and a continuous-wave (CW) bunch train compatible with acceleration to 12 GeV at the Continuous Electron Beam Accelerator Facility (CEBAF). In this presentation we describe a start-to-end layout for positron beams at 12 GeV CEBAF utilizing the Low Energy Research Facility (LERF) at Jefferson Lab to build two new injectors. A GaAs dc high voltage photo-gun first generates >1 mA of polarized electrons which are then accelerated to 80-150 MeV and directed to a high-power spinning W target for polarized bremsstrahlung and positron pair creation. A second injector then collects, bunches and accelerates the positrons to 123 MeV. The positron beams are transported by a new beam line and injected into the CEBAF acceptance for acceleration to the end stations with energies up to 12 GeV. The layout is optimized to provide Users with positron spin polarization >60% and intensity greater than >100 nA, and with higher intensities when polarization is not required.

Benesch, J.↗
DOE OSTI2023

Beam study on low dispersion CEBAF arcs

The Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab employs recirculating linac SRF technology to generate a high polarization 12 GeV electron beam for nuclear physics users. New opportunities to study multipass energy recovery have also emerged with the proposal of a 5-pass energy recovery demonstration, ER@CEBAF. New beam optics with minimized beta functions have been developed and tested to avoid collective beam instabilities for multi-pass beams and meet the beam requirements of the nuclear physics community. To enable energy recovery for a common arc beam transport of five passes, achromatic and isochronous arc optics conditions were satisfied by re-designing the transverse optics of CEBAF. This paper focuses on beam studies conducted to study the newly-designed, low-dispersion, lowest energy arcs for CEBAF operations and ER@CEBAF.

Neththikumara, I.↗
DOE OSTI2023

Evaluation of a High-Power Target Design for Positron Production at CEBAF

A source for polarized positron beams at the Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab is being designed. The Polarized Electrons for Polarized Positrons (PEPPo) concept is used to produce polarized e$^+$e$^-$-pairs from the bremsstrahlung radiation of a longitudinally polarized electron beam interacting within a high-Z conversion target. The scheme under consideration includes a 4 mm thick tungsten target that absorbs 17 kW deposited by a 1 mA continuous-wave electron beam with an energy of 120 MeV. The concept of a rotating tungsten rim mounted on a water-cooled copper disk was explored. The results of ANSYS thermal and mechanical analyses are discussed together with FLUKA evaluations of the radiation damages.

Ushakov, A.↗
DOE OSTI2024

TRANSFER LEARNING FOR FIELD EMISSION MITIGATION IN CEBAF SRF CAVITIES

The Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab operates hundreds of super-conducting radio frequency (SRF) cavities in its two linear accelerators (linacs). Field emission (FE) is an ongoing operational challenge in higher gradient SRF cavities. FE generates high levels of neutron and gamma radiation leading to damaged accelerator hardware and a radiation hazard environment. During machine development periods, we performed gradient scans to record data capturing the relationship between cavity gradients and radiation levels measured throughout the linacs. However, the field emission environment at CEBAF varies considerably over time as the configuration of the radio frequency (RF) gradients changes and due to the changing behaviour of field emitters. An artificial intelligence/machine learning (AI/ML) approach with transfer learning could be a valuable tool to mitigate FE and lower the radiation levels. In this work, we mainly focus on leveraging the RF trip data gathered during CEBAF operations. We develop a transfer learning-based surrogate model for radiation detector readings given RF cavity gradients to track the CEBAF?s changing configuration and environment. Then, we could use the developed model as an optimization process for redistributing the RF gradients within a linac to minimize radiation levels.

Ahammed, K.↗
DOE OSTI2024

Towards large phase space beams at the CEBAF injector

We report on the status of a degrader device to generate large phase space beams for machine acceptance studies in the Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab. The degrader device consists of thin, low-Z targets to degrade the electron beam phase space through multiple scattering, two apertures to define the maximum transverse emittance, and a solenoid to aid in matching to the rest of the injector beamline. The engineering design of the degrader device and projected degraded beam phase space parameters are presented.

Sy, A.↗
DOE OSTI2024

Simulations of Positron Capture at Ce+BAF

We present a capture concept for the continuous wave (CW) polarized positron injector for the Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab (Ce+BAF). This two-step concept is based on (1) the generation of bremsstrahlung radiation by a longitudinally polarized electron beam 1 mA, 120 MeV, 90% polarization), passing through a tungsten target, and (2) the production of e+e--pairs by these bremsstrahlung photons in the same target. To provide highly-polarized positron beams (>60% polarization) or high-current positron beams (>1 µA) with low polarization for nuclear physics experiments, the positron source requires a flexible capture system with an adjustable energy selection band. The results of beam dynamics simulations and calculations of the power deposited in the positron capture section are presented.

Ushakov, Andriy↗
DOE OSTI2024

Computational simulations and beamline optimizations for an electron beam degrader at CEBAF

An electron beam degrader is under development with the objective of measuring the transverse and longitudinal acceptance of the Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab. This project is in support of the CE+BAF positron capability. Computational simulations of beam-target interactions and particle tracking were performed integrating the GEANT4 and Elegant toolkits. A solenoid was added to the setup to control the beam's divergence. Parameter optimization of the solenoid field and magnetic quadrupoles gradient was also performed to further reduce particle loss through the rest of the injector beamline.

Lizárraga-Rubio, V.↗
DOE OSTI2022

A 500 KV INVERTED GEOEMTRY FEEDTHROUGH FOR A HIGH VOLT-AGE DC ELECTRON GUN

The Continuous Electron Beam Accelerator Facility injector at Jefferson Lab (JLab) utilizes an inverted-geometry ceramic insulator photogun operating at 130 kV direct current to generate spin-polarized electron beams for high-energy nuclear physics experiments. A second photogun delivers 180 keV beam for commissioning a SRF booster in a testbed accelerator, and a larger version delivers 300 keV magnetized beam in a test stand beam line. This contribution reports on the development of an unprecedented inverted-insulator with cable connector for reliably applying 500 kV DC to a future polarized beam photogun, to be designed for operating at 350 kV without field emission. Such a photogun design could then be used for generating a polarized electron beam to drive a spin-polarized positron source as a demonstrator for high energy nuclear physics at JLab. There are no commercial cable connectors that fit the large inverted insulators required for that voltage range. Our proposed concept is based on a modified epoxy receptacle with intervening SF6 layer and a test electrode in a vacuum vessel.

Hernandez-Garcia, C.↗
DOE OSTI2023

First Results from Nanoindentation of Vapor Diffused Nb3Sn Films on Nb

The mechanical vulnerability of the Nb3Sn-coated cavities is identified as one of the significant technical hurdles toward deploying them in practical accelerator applications in the not-so-distant future. It is crucial to characterize the material's mechanical properties in ways to address such vulnerability. Nanoindentation is a widely used technique for measuring the mechanical properties of thin films that involves indenting the film with a small diamond tip and measuring the force-displacement response to calculate the film's elastic modulus, hardness, and other mechanical properties. For the first time, the nanoindentation analysis was performed on multiple vapor-diffused Nb3Sn samples coated at Jefferson Lab and Fermilab coating facilities. This contribution will discuss the first results obtained from the nanoindentation of Nb3Sn-coated Nb samples prepared via the Sn vapor diffusion technique.

Pudasaini, Uttar↗
DOE OSTI2020

Soft Matter Thermal and Mechnical Devices

The participant company, Treau, makes homes and buildings more comfortable with quiet, energy efficient, and easy to install heating and cooling systems. They entered the Cyclotron Road program with an idea for a heat exchanger and compressor and a general idea that the building heating and cooling sector was the best first target market. While at Cyclotron Road, they used the Cyclotron Road program staff and Berkeley Lab expertise to better understand the needs of the heating and cooling equipment market. This was critical to understand who the end customer was, and what features were needed in this market. They were then able to conduct product development with this target market/customer in mind. The Cyclotron Road program was also critical in building a manufacturing and scale-up plan that allowed the participant to build a credible growth and fundraising strategy. By the end of the program, the participant had a working prototype testing at Berkeley Lab’s HVAC testing facilities.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2020

Machine Learning Based Cavity Fault Classification and Prediction

We report on the development of machine learning models for classifying C100 superconducting radio frequency (SRF) cavity faults in the Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab. CEBAF is a continuous-wave recirculating linac utilizing 418 SRF cavities to accelerate electrons up to 12 GeV through 5-passes. Of these, 96 cavities (12 cryomodules) are designed with a digital low-level RF system configured such that a cavity fault triggers waveform recordings of 17 RF signals for each of the eight cavities in the cryomodule. Subject matter experts (SME) can analyze the collected time-series data, identify which of the eight cavities faulted first, and classify the type of fault. This information is used to find trends and strategically deploy mitigations to problematic cryomodules. However, manually labeling the data is laborious and time-consuming. By leveraging machine learning, near real-time – rather than post-mortem – identification of the offending cavity and classification of the fault type has been implemented. We discuss the performance of the ML models during a recent physics run.

43 PARTICLE ACCELERATORS↗
DOE OSTI2021

Design of a 10 MeV beamline at the Upgraded Injector Test Facility for e-beam irradiation

Electron beam irradiation near 10 MeV is suitable for wastewater treatment. The Upgraded Injector Test Facility (UITF) at Jefferson Lab is a CW superconducting linear accelerator capable of providing an electron beam of energy up to 10 MeV and up to 100 µA current. This contribution presents the beam transport simulations for a beamline to be used for the irradiation of wastewater samples at the UITF. The simulations were done using the code General Particle Tracer with the goal of obtaining an 8 MeV electron beam of radius (3-σ) of ~2.4 cm. The achieved energy spread is ~74.5 keV. The space charge effects were investigated when the bunch charge is varied to be up to 1000 times and the results showed that they do not affect the beam quality significantly.

Li, X.↗
DOE OSTI2023

Evaluation of a High-Power Target Design for Positron Production at CEBAF

A source for polarized positron beams at the Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab is being designed. The Polarized Electrons for Polarized Positrons (PEPPo) concept is used to produce polarized e$^+$e$^-$-pairs from the bremsstrahlung radiation of a longitudinally polarized electron beam interacting within a high-Z conversion target. The scheme under consideration includes a 4 mm thick tungsten target that absorbs 17 kW deposited by a 1 mA continuous-wave electron beam with an energy of 120 MeV. The concept of a rotating tungsten rim mounted on a water-cooled copper disk was explored. The results of ANSYS thermal and mechanical analyses are discussed together with FLUKA evaluations of the radiation damages.

Ushakov, A.↗
DOE OSTI2024

Simulations of Positron Capture at Ce+BAF

We present a capture concept for the continuous wave (CW) polarized positron injector for the Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab (Ce+BAF). This two-step concept is based on (1) the generation of bremsstrahlung radiation by a longitudinally polarized electron beam 1 mA, 120 MeV, 90% polarization), passing through a tungsten target, and (2) the production of e+e--pairs by these bremsstrahlung photons in the same target. To provide highly-polarized positron beams (>60% polarization) or high-current positron beams (>1 µA) with low polarization for nuclear physics experiments, the positron source requires a flexible capture system with an adjustable energy selection band. The results of beam dynamics simulations and calculations of the power deposited in the positron capture section are presented.

Ushakov, Andriy↗
DOE OSTI2024

TRANSFER LEARNING FOR FIELD EMISSION MITIGATION IN CEBAF SRF CAVITIES

The Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab operates hundreds of super-conducting radio frequency (SRF) cavities in its two linear accelerators (linacs). Field emission (FE) is an ongoing operational challenge in higher gradient SRF cavities. FE generates high levels of neutron and gamma radiation leading to damaged accelerator hardware and a radiation hazard environment. During machine development periods, we performed gradient scans to record data capturing the relationship between cavity gradients and radiation levels measured throughout the linacs. However, the field emission environment at CEBAF varies considerably over time as the configuration of the radio frequency (RF) gradients changes and due to the changing behaviour of field emitters. An artificial intelligence/machine learning (AI/ML) approach with transfer learning could be a valuable tool to mitigate FE and lower the radiation levels. In this work, we mainly focus on leveraging the RF trip data gathered during CEBAF operations. We develop a transfer learning-based surrogate model for radiation detector readings given RF cavity gradients to track the CEBAF?s changing configuration and environment. Then, we could use the developed model as an optimization process for redistributing the RF gradients within a linac to minimize radiation levels.

Ahammed, K.↗
DOE OSTI2025

Polarized positrons at Ce\(^+\)BAF

A baseline concept for a continuous wave (CW) polarized positron injector was developed for the Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab [1]. This concept is based on positron beam generation by a high current polarized electron beam (1 mA, 120 MeV, >85% polarization) irradiating a 4 mm thick rotating water-cooled tungsten target or liquid metal target. The update on the development of the Ce+BAF injector concept including the polarized electron source, the development of high power targets, simulations of positron capture, the design of the transport line from the positron injector to the CEBAF North Linac and the planned experiment to measure the upper limits of transverse and longitudinal emittances accepted by the 12 GeV CEBAF optics are presented. [1] J. Grames et al., "Positron beams at Ce+BAF", in Proc. 14th Int. Particle Accelerator Conf. (IPAC’23), Venice, Italy, MOPL152, pp. 896–899 (2023). doi:10.18429/JACoW-IPAC2023-MOPL152

Ushakov, Andriy↗
DOE OSTI2022

ION PRODUCTION AND MITIGATION IN DC HIGH-VOLTAGE PHOTO-GUNS

One of the biggest obstacles to operating a GaAs polarized electron source with a long charge lifetime is the mitigation of ion back-bombardment. Several techniques exist to either clear ions from the accelerator or to mitigate ion damage of the photocathode. Predicting the effectiveness of these techniques requires sophisticated simulation models of electron impact ionization within the photo-gun. In this work, the effectiveness of applying a positive anode bias voltage to mitigate ion damage and increase the charge lifetime of the GaAs photocath?ode was studied over three run periods at the Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab (JLab). The charge lifetime with the biased anode configuration was 1.80±0.51 times longer than the lifetime of the usual grounded anode configuration. Sim?ulations of ionization within the CEBAF photo-gun and adjacent beamline were made using General Particle Tracer (GPT) and a new C++ custom element to predict and explain the substantial improvement in charge lifetime. The experimental results and the development of the ionization custom element, with its use in simulations of ion back-bombardment with the biased anode, are described in detail.

Yoskowitz, Joshua↗
DOE OSTI2022

Deep Learning Based Superconducting Radio-Frequency Cavity Fault Classification at Jefferson Laboratory

This work investigates the efficacy of deep learning (DL) for classifying C100 superconducting radio-frequency (SRF) cavity faults in the Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab. CEBAF is a large, high-power continuous wave recirculating linac that utilizes 418 SRF cavities to accelerate electrons up to 12 GeV. Recent upgrades to CEBAF include installation of 11 new cryomodules (88 cavities) equipped with a low-level RF system that records RF time-series data from each cavity at the onset of an RF failure. Typically, subject matter experts (SME) analyze this data to determine the fault type and identify the cavity of origin. This information is subsequently utilized to identify failure trends and to implement corrective measures on the offending cavity. Manual inspection of large-scale, time-series data, generated by frequent system failures is tedious and time consuming, and thereby motivates the use of machine learning (ML) to automate the task. This study extends work on a previously developed system based on traditional ML methods (Tennant and Carpenter and Powers and Shabalina Solopova and Vidyaratne and Iftekharuddin, Phys. Rev. Accel. Beams, 2020, 23, 114601), and investigates the effectiveness of deep learning approaches. The transition to a DL model is driven by the goal of developing a system with sufficiently fast inference that it could be used to predict a fault event and take actionable information before the onset (on the order of a few hundred milliseconds). Because features are learned, rather than explicitly computed, DL offers a potential advantage over traditional ML. Specifically, two seminal DL architecture types are explored: deep recurrent neural networks (RNN) and deep convolutional neural networks (CNN). We provide a detailed analysis on the performance of individual models using an RF waveform dataset built from past operational runs of CEBAF. In particular, the performance of RNN models incorporating long short-term memory (LSTM) are analyzed along with the CNN performance. Furthermore, comparing these DL models with a state-of-the-art fault ML model shows that DL architectures obtain similar performance for cavity identification, do not perform quite as well for fault classification, but provide an advantage in inference speed.

97 MATHEMATICS AND COMPUTING↗