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At least 1,099 records · Page 61
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Multiplexer System for the SPEAR3 Booster BPM Upgrade

BPM measurements in booster synchrotrons are often only critical during accelerator commissioning or when a problem occurs. As a result, many facilities do not make large investments in booster BPM signal processors; they either have very few BPMs and/or use older generation processors. The SPEAR3 booster BPM processor system, for instance, has operated since 1990 with commercial multiplexers to switch between BPM button signals into a single dated analog BPM processor that was developed at SLAC*. This system has reached its end-of-life so we are in the process of upgrading to modern multiplexers that feed a pair of turn-by-turn Libera SPARK-ERXR processors. This low-cost solution gives us the ability to arbitrarily multiplex between BPM signals during the energy ramp with modern BPM processors. The system can either measure 2 BPMs turn-by-turn in parallel during the entire energy ramp, or sequentially measure all BPMs (2 at a time) at different time slices within the ramp. Here we show measurements of the MiniCircuits switch we chose as well as our architecture for the upgrade.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2020

Direct Observations of Sub-micropulse Electron-beam Effects from Short-range Wakefields in TESLA-type Superconducting RF Cavities

The preservation of the low emittance of electron beams during transport in the accelerating structures of large facilities is an ongoing challenge. In the cases of the TESLA-type superconducting rf cavities currently used in the European X-ray Free-electron Laser (FEL) and the under construction Linac Coherent Light Source upgrade (LCLS-II), off-axis beam transport may result in emittance dilution due to transverse long-range and short-range wakefields (SRW)*. To investigate such effects, experiments were performed at the Fermilab Accelerator Science and Technology (FAST) facility with its unique two-cavity configuration after the photocathode rf gun. We used optical transition radiation (OTR) imaging with a UV-visible synchroscan streak camera to display sub-micropulse y-t effects in the 41-MeV beam. The head-tail transverse kicks within the 11-ps-long micropulses were observed at the 100-micron level for steering off-axis in one cavity and several 100 microns for two cavities. Since the SRW kick angles go inversely with energy, these results may inform the commissioning plans of the LCLS-II injector where beam will be injected at ~1 MeV into a cryomodule.

43 PARTICLE ACCELERATORS↗
DOE OSTI2021

BPM System for the PIP-II Injector Test Facility

A new BPM system was used for commissioning and operation of the PIP2 Injector Test Facility. The system of 13 warm and 12 cold BPMs was based upon custom 250 MS/s digitizers controlled and readout over gigabit ethernet by a single multi-core rackmount server running linux. The system provided positions, intensity, and phase for each bpm as a pulse average or pulse waveform from 10 us to 4 ms at a 20 Hz pulse repetition rate.

43 PARTICLE ACCELERATORS↗
DOE OSTI2021

Machine Learning Training for HOM reduction and Emittance Preservation in a TESLA-type Cryomodule at FAST

Low emittance electron beams are of high importance at facilities like the LCLS-II at SLAC. Emittance dilution effects due to off-axis beam transport for a TESLA-type cryomodule (CM) have been shown at the Fermilab Accelerator Science and Technology facility. The results showed the correlation between the electron beam-induced cavity high-order modes (HOMs) and submacropulse centroid slewing and oscillation downstream of the CM. Mitigation of emittance dilution can be achieved by reducing the HOM signals and the variances in the submacropulse beam positions downstream of the CM. Here we present a Machine Learning based optimization and model construction for HOM signal level reduction using Neural Networks and Gaussian Processes. To gather training data we performed experiments using single bunch and 50 bunch electron beams with charges up to 125 pC/b. We measured HOM signals of all cavities and beam position with a set of BPMs downstream of the CM. The beam trajectory was changed using V/H125 corrector set located upstream of the CM. The results presented here will inform the LCLS-II injector commissioning and will serve as a prototype for HOM reduction and emittance preservation.

43 PARTICLE ACCELERATORS↗
DOE OSTI2021

Evaluation of Anisotropic Magnetoresistive (AMR) Sensors for a Magnetic Field Scanning System for SRF Cavities

One of the significant causes of residual losses in superconducting radio-frequency (SRF) cavities is trapped magnetic flux. The flux trapping mechanism depends on many factors that include cool-down conditions, surface preparation techniques, and ambient magnetic field orientation. Suitable diagnostic tools are not yet available to quantitatively correlate such factors’ effect on the flux trapping mechanism. A magnetic field scanning system (MFSS) consisting of AMR sensors, fluxgate magnetometers, or Hall probes is recently commissioned to scan the local magnetic field of trapped vortices around 1.3 GHz single-cell SRF cavities. In this contribution, we will present results from sensitivity calibration and the first tests of AMR sensors in the MFSS.

Parajuli, I. P.↗
DOE OSTI2021

Numerical Modelling of the Optical Stochastic Cooling Experiment at IOTA

A proof-of-principle optical-stochastic cooling (OSC) experiment is currently in its commissioning phase at the Fermilab’s IOTA ring. In support of this experiment, we recently implemented an OSC element in the ELEGANT tracking program. The model, based on a semi-analytic description of OSC [*], supports the simulation of a large number of macroparticles (10⁴-10⁶) over many turns (10⁶). This paper showcases the simulation capabilities to investigate the beam dynamics in the presence of cooling (or self-interacting radiation field in general) and quantify the impact of various sources of error (e.g. transverse and phase jitter), guide data analysis.

43 PARTICLE ACCELERATORS↗
DOE OSTI2022

MAGNETIC FIELD MAPPING OF 1.3 GHz SUPERCONDUCTING RADIO FREQUENCY NIOBIUM CAVITIES

Niobium is the material of choice to build superconducting radio frequency (SRF) cavities, which are fundamental building blocks of modern particle accelerators. These cavities require a cryogenic cool-down to ~2 - 4 K for optimum performance minimizing RF losses on the inner cavity surface. However, temperature-independent residual losses in SRF cavities cannot be prevented entirely. One of the significant contributor to residual losses is trapped magnetic flux. The flux trapping mechanism depends on different factors, such as surface preparations and cool-down conditions. We have developed a diagnostic magnetic field scanning system (MFSS) using Hall probes and anisotropic magneto-resistance sensors to study the spatial distribution of trapped flux in 1.3 GHz single-cell cavities. The first result from this newly commissioned system revealed that the trapped flux on the cavity surface might redistribute with increasing RF power. The MFSS was also able to capture significant magnetic field enhancement at specific cavity locations after a quench.

Parajuli, I. P.↗
DOE OSTI2022

Electron Accelerator Lattice Design for LHeC with Permanent Magnets

We present a new ’green energy’ approach to the Energy Recovery Linac (ERL) the future Electron Ion Collider at LHeC using single beam line made of very strong focusing combined function permanent magnets and the Fixed Field Alternating Linear Gradient (FFA-LG) principle. We are basing our design on recent very successful commissioning results of the Cornell University and Brookhaven National Laboratory ERL Test Accelerator-CBETA.

Trbojevic, D.↗
DOE OSTI2023

Status of Error Correction Studies in Support of FFA@CEBAF

In pursuit of higher energy at the Continuous Electron Beam Accelerator Facility (CEBAF), the FFA@CEBAF energy upgrade study is considering the implementation of a novel technology to recirculate electron beam through the accelerating gradient of the machine more times. The technology in question is Fixed-Field Alternating-gradient (FFA) bending accelerator arcs: these arcs may replace the present highest energy electromagnetic (EM) arcs, and due to a much wider energy acceptance allow several more passes. The survey and beam error tolerance of the FFA arcs need to be well understood prior to commissioning, in addition to the limits of planned correction magnets and diagnostics. This work explores the current state of error tolerance and correction studies in FFA arcs at CEBAF.

Benesch, J.↗
DOE OSTI2023

A Compton transmission polarimeter for DC and SRF electron photo-injectors

The production of high-current and intense spin polarized electron beams is of great importance in electron-based facilities. Tests are planned to produce such beams in 2023 using GaAs-based photocathodes installed in the Brookhaven National Lab RHIC Coherent electron Cooling superconducting radiofrequency (SRF) photogun [1]. A fast and efficient electron polarimeter operating in the MeV energy range is required to measure the beam spin polarization. While Mott polarimeters provide larger measured asymmetries, a Compton Transmission polarimeter is well suited in the few MeV energy range. In this work, we report on a relatively compact and cost-effective Compton transmission polarimeter which has been built and calibrated at Jefferson Lab (JLab). First, we present the design of the polarimeter radiator, polarized target analyzing magnet, BGO detector assembly and data acquisition system. Next, results of a two-week commissioning study performed at the JLab Upgraded Injector Test Facility will be described. Here, a well-known polarized electron beam produced from a bulk GaAs photocathode in a dc high-voltage photogun was first measured in a 180 keV Mott scattering polarimeter, then used to characterize and calibrate the Compton transmission polarimeter as a function of the polarized target magnetization and beam properties. Finally, we report an effective analyzing power of the Compton polarimeter and compare experimental results with those produced via Geant4 simulations.

Blume, G.↗
DOE OSTI2023

Lattice design of 250 MeV version of PERLE

The PERLE (Powerful Energy Recovery LINAC for Experiment) collaboration is working on a high power energy recuperation linac facility with three acceleration (up to 500 MeV) and three deceleration passes through two cryomodules with an injection current of 20 mA. Here we present the lattice design of the first phase of this machine, which features a single cryo-module and demonstrates six-pass operation at a maximum energy of 250 MeV at a high current. This initial lattice design boasts a simpler structure with fewer elements, resulting in lower initial costs and faster construction and shorter commissioning time. Furthermore, all magnets and cryo-modules are designed to be compatible with both phases, keeping upgrade costs to a minimum.

Fomin, A.↗
DOE OSTI2023

Measurements at peak operational beam current in the SNS beam test facility

Work at the SNS beam test facility has focused on high dimensional and high dynamic range measurements of the medium energy (2.5 Mev) beam distribution. This is motivated by the need to understand and predict beam losses down to one-part-per-million. The initial demonstration of full-and-direct 6D phase space measurement was done at a current of 40 mA transported through the RFQ. Since that demonstration, more detailed studies have been performed at lower transported currents (in the range 30 mA and below). This is due to a hardware change - recent runs utilize the original SNS RFQ, which after a decade of service in the SNS achieves transmission significantly below design (50-60%, vs >80%). A short run in 2023 with a newly-commissioned RFQ enables maximum transmission. Preliminary results from beam distribution measurements during this run are discussed.

Ruisard, Kiersten↗
DOE OSTI2023

Modeling for the phased injector upgrade for 12 GeV CEBAF

As a follow on to the 12 GeV upgrade to the Continuous Electron Beam Accelerator Facility, the front end of the DC photo-gun-based injector has gone through a phased upgrade. The first phase focused on the beamline between the gun and the RF chopper system, and the second phase addresses the beamline after the RF chopper system including replacing the capture section and quarter cryomodule with a new booster module containing a 2-cell and 7-cell cavity string. Throughout the design process, we maintained and developed three models, one for the existing injector and one for each of the upgrade phases. With these models, we evaluated proposed hardware upgrades, evaluated and determined optimized beamline element positions, developed buncher voltage requirements, and settings for optimal injector running. In this paper, we will describe the models and results from these various studies and provide a brief summary of Phase 1 commissioning.

Kazimi, R.↗
DOE OSTI2024

ORBITAL ANGULAR MOMENTUM BEAMS RESEARCH USING A FREE-ELECTRON LASER OSCILLATOR

We present a Fixed-Field-Alternating (FFA) permanent magnet racetrack electron accelerator with energy range between 10-60 GeV for the future LHeC. Electron beam is brought back to the linac by the single beam line without requiring electric power REDUCING estimated wall power of 100 MW in the present LHeC design to a negligible power for arcs as the permanent magnets are used. The design is based on experience from the very successful commissioning of the Cornell University and Brookhaven National Laboratory Energy Recovery Test Accelerator ? ?CBETA?. The proposal supports sustainability efforts for LHeC by making a 'green' accelerator. It is an energy recovery linac with 99.9% energy efficiency and reduces the power consumption by using small permanent magnets. The FFA non-linear gradient design is a racetrack shape, where, as in the CBETA, the arcs are matched by adiabatic transition to the two (LHeC) or multiple straight sections. Two 10 GeV superconducting linacs are placed on both sides of the Interaction Region (IR) significantly reducing the power of synchrotron radiation loss.

Trbojevic, D.↗
DOE OSTI2024

Proton beam dynamics in bare IOTA with intense space-charge

We are commissioning a 2.5-MeV proton beam for the Integrable Optics Test Accelerator at Fermilab, allowing experiments in the strong space-charge regime with incoherent betatron tune shifts nearing 0.5. Accurate modelling of space-charge dynamics is vital for understanding planned experiments. We compare anticipated emittance growth and beam loss in the bare IOTA configuration using transverse space-charge models in Xsuite, PyORBIT, and MADX simulation codes. Our findings reveal agreement within a factor of 2 in core phase-space density predictions up to 100 synchrotron periods at moderate beam currents, while tail distributions and beam loss show significant differences.

43 PARTICLE ACCELERATORS↗
DOE OSTI2024

Progress towards the completion of the proton power upgrade project

The Proton Power Upgrade project at the Spallation Neutron Source at Oak Ridge National Laboratory will increase the proton beam power capability from 1.4 to 2.8 MW. Upon completion in early 2025, 2 MW of beam power will be available for neutron production at the existing first target station (FTS) with the remaining beam power available for the future second target station (STS). The project has installed seven superconducting radio-frequency (RF) cryomodules and supporting RF power systems to increase the beam energy by 30% to 1.3 GeV, and the beam current will be increased by 50%. The injection and extraction region of the accumulator ring are being upgraded, and a new 2 MW mercury target has been developed along with supporting equipment for high-flow gas injection to mitigate cavitation and fatigue stress. The first four cryomodules and supporting systems were commissioned in 2022-2023 and supported neutron production at 1.05 GeV, 1.7 MW with high reliability. The first-article 2 MW target was operated successfully for approximately 4400 MW-Hours over two run periods. The long outage began in August 2023 for installation of the remaining technical equipment and construction of the Ring-to-Target Beam Transport tunnel stub that will enable connection to the STS without interrupting operation of the FTS. The upgrade is proceeding on-schedule and on-budget, and resumption of neutron production for the user program is planned for July 2024.

43 PARTICLE ACCELERATORS↗
DOE OSTI2025

Optics tuning of the FCC-ee

The Future Circular Collider, FCC-ee, is a proposed next generation electron-positron collider aiming to provide large luminosities at beam energies from 45.6 up to 182.5 GeV. This collider faces a major challenge to deliver the design performance in the presence of realistic lattice errors. A commissioning strategy has been developed including dedicated optics designs, efficient beam-based alignment and optics corrections based on refined optics measurements. First specifications on main magnets, corrector circuits, and instrumentation have also been investigated. A summary of all these aspects is presented in this paper.

Tomas, Rogelio [CERN]↗
DOE OSTI2025

Beam results for the new super-conducting booster at Jefferson Lab

The performance results of a new super-conducting booster for the CEBAF injector at Jefferson Lab, could be of interest for other similar electron injectors. A recent addition of this new booster has provided us the ability to achieve a more adiabatic acceleration and therefore an improvement to the beam dynamics and beam brightness. It has also simplified the design and operation of the section of the injector responsible for accelerating the electron beam from a few hundred keV to several MeV (typically 6.7 MeV). The addition of the new booster was part of an upgrade to the CEBAF injector to improve the beam quality for future physics experiments with high sensitivity to beam quality. The booster consists of two cavities: a 2-cell cavity followed by a 7-cell cavity. This combination allows for a wide range of input electron beam energies, from 130 keV to more than 300 keV. In fact, during the last year, the booster was successfully operated with 140,180, and 200 keV input beam energies as the electron gun was being upgraded. This paper describes the new booster, presents beam optics data results from different beam studies, commissioning, and the physics quality beam operation.

Accelerator Physics↗