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At least 487 records · Page 27
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DOE OSTI2026

Universal Injector at LERF – Baseline Design

A new electron injector complex has been proposed within the Low Energy Recirculating Facility (LERF) vault, which would serve both the 22 GeV CEBAF and the positron programs, while being compatible with the electron source required to produce positrons for Ce+BAF. The baseline design of a 3-pass recirculator features a main linac configured with three cryomodules, five isochronous arcs and three straight sections, allowing electron beam acceleration up to 650 MeV. The injector offers the flexibility to extract 1-pass and 2-pass energy electrons, as needed for positron production, with final reconfiguration to a 3-pass 650 MeV injector for 22 GeV CEBAF. This paper provides an overview of the baseline design of the Universal injector complex, including the 8 MeV injector and the recirculator. A comprehensive suite of beam dynamics studies to validate our design is being launched, starting with start-to-end tracking with Elegant followed by the orbit correction and error mitigation.

Bogacz, A. [Thomas Jefferson National Accelerator ↗
DOE OSTI2024

CW copper injector for SRF industrial cryomodules

Compact SRF industrial linacs can provide unique parameters of the beam (>1 MW and >1-10 MeV) hardly achievable by normal conducting linacs within limited space. SRF technology was prohibitively expensive until the development of conduction cooling which opened the way for compact stand alone SRF systems suitable for industrial and research applications. Limited cooling capacity puts strict requirements on the beam parameters with zero losses of the beam on the SRF cavity walls. This implies strict requirements on the beam energy to be accepted by the cryomodule and most importantly the beam bunching with zero particles in between. We designed a CW normal conducting RF injector which consists of a gridded RF gun integrated with a first cell of a copper booster cavity to satisfy these requirements. Here we present a complete design of a booster cavity including beam dynamics, RF, thermomechanical and engineering design.

43 PARTICLE ACCELERATORS↗
DOE OSTI2025

ESTIMATION OF THE WAKEFIELD RESONANT FREQUENCY USING DIFFERENT SIMULATION TOOLS

Reliable and fast wakefield calculations are important for beam dynamics and THz generation in accelerators. We compare approaches and limitations with different available simulation tools and compare results. As an example, we analyse a cylindrical corrugated waveguide with narrower and wider radii of 5 and 6 mm, and aperture width and periodicity of 1 and 2 mm using ABCI by KEK and ANSYS HFSS simulation software. First, ABCI was used to determine the resonant frequency of the cylindri-cal corrugated waveguide with different lengths. The corresponding results were taken as a reference to exam-ine the simulation method in the ANSYS HFSS environ-ment. The eigenmode solver of ANSYS HFSS was used to determine different resonant frequencies. This was fol-lowed by examining a cylindrical corrugated waveguide that was implemented having a length of 17 mm for dif-ferent conductor settings. The corresponding waveguide was fed by a plane wave having a resonant frequency that satisfies the intersection of the light line and dispersion curve of the corresponding mode. The analysis showed that the maximum loss factor was achieved at 39.20 and 40.07 GHz using ANSYS HFSS simulation data for differ-ent conductors, whereas ABCI resulted in 38.50 GHz. The talk will present the results gathered by different simula-tion setups implemented in ANSYS HFSS.

Unutmaz, Muhammed [SLAC National Accelerator Labor↗
DOE OSTI2022

PERLE - ERL Test Facility at Orsay

PERLE (Powerful ERL for Experiments)[1] is a novel Energy Recovery Linac (ERL) test facility, designed to validate choices for a 50 GeV ERL foreseen in the design of the Large Hadron Electron Collider (LHeC) and the Future Circular Collider (FCC-eh), and to host dedicated nuclear and particle physics experiments. Its main thrust is to probe high current, continuous wave (CW), multi-pass operation with superconducting cavities at 802 MHz. With very high transient beam power (10 MW), PERLE offers an opportunity for controllable study of every beam dynamic effect of interest in the next generation of ERL design and becomes a ‘stepping stone’ between present state-of-art 1 MW ERLs and future 100 MW scale applications.

Bogacz, S. Alex↗
DOE OSTI2015

An overview of Booster and AGS polarized proton operation during Run 15

This note is an overview of the Booster and AGS for the 2015 Polarized Proton RHIC run from an operations perspective. There are some notable differences between this and previous runs. In particular, the polarized source intensity was expected to be, and was, higher this year than in previous RHIC runs. The hope was to make use of this higher input intensity by allowing the beam to be scraped down more in the Booster to provide a brighter and smaller beam for the AGS and RHIC. The RHIC intensity requirements were also higher this run than in previous runs, which caused additional challenges because the AGS polarization and emittance are normally intensity dependent.

43 PARTICLE ACCELERATORS↗
DOE OSTI2016

A close look at beam aborts with rise times less than 40 ms from the years 2014-2016. Case studies.

In an effort to understand the risks of operating RHIC with an additional delay of 40 ms in the abort system, all beam aborts triggered by loss monitors at store from the years 2014, 2015 and 2016 were analyzed; and particularly fast cases, selected. The results were presented at the RHIC retreat on Jul 29, 2016. All beam aborts at injection, during the ramp and at flattop but before the “ev-lumi” event were ignored since the additional delay of 40 ms is proposed for operation at store only. Many (but not all) of the 15 studied cases are of no concern. Cases with high damage potential are rare - but not rare enough. In order to make an added 40 ms during physics store conditions as safe as reasonably possible, additional permit inputs such as 10 Hz BF power supplies, RF storage cavities, power supply error states or BPMs, in addition to significantly reduced loss monitors (LM) thresholds for selected LM should be commissioned.

43 PARTICLE ACCELERATORS↗
DOE OSTI2016

Overview and analysis of the 2016 Gold Run in the Booster and AGS

Run 16 differed from preceding Au runs in that during most of it a 12:6:2 merge was employed in the AGS instead of an 8:4:2 merge. This was done to provide higher bunch intensities for RHIC. Since the approach to providing higher bunch intensities is, and has been, to merge more Booster bunches of the same intensity into one final bunch, detailing the longitudinal aspects of this setup seems quite relevant. So, aside from providing an overview of the Au portion of Run 16, this note also contains a series of emittance measurements in the Booster and AGS. Comparisons of these to similar measurements in previous runs are also made in hopes of gaining a better understanding of what factors contribute to the emittance of a bunch at AGS extraction. The note also tries to provide some context in which to understand the various merge schemes and describes a potential 8 to 1 type merge.

43 PARTICLE ACCELERATORS↗
DOE OSTI2016

Theory and Modeling of Petawatt Laser Pulse Propagation in Low Density Plasmas

Report describing accomplishments in all-optical control of self-injection in laser-plasma accelerators and in developing advanced numerical models of laser-plasma interactions. All-optical approaches to controlling electron self-injection and beam formation in laser-plasma accelerators (LPAs) were explored. It was demonstrated that control over the laser pulse evolution is the key ingredient in the generation of low-background, low-phase-space-volume electron beams. To this end, preserving a smooth laser pulse envelope throughout the acceleration process can be achieved through tuning the phase and amplitude of the incident pulse. A negative frequency chirp compensates the frequency red-shift accumulated due to wake excitation, preventing evolution of the pulse into a relativistic optical shock. This reduces the ponderomotive force exerted on quiescent plasma electrons, suppressing expansion of the bubble and continuous injection of background electrons, thereby reducing the charge in the low-energy tail by an order of magnitude. Slowly raising the density in the pulse propagation direction locks electrons in the accelerating phase, boosting their energy, keeping continuous injection at a low level, tripling the brightness of the quasi-monoenergetic component. Additionally, propagating the negatively chirped pulse in a plasma channel suppresses diffraction of the pulse leading edge, further reducing continuous injection. As a side effect, oscillations of the pulse tail may be enhanced, leading to production of low-background, polychromatic electron beams. Such beams, consisting of quasi-monoenergetic components with controllable energy and energy separation, may be useful as drivers of polychromatic x-rays based on Thomson backscattering. These all-optical methods of electron beam quality control are critically important for the development of future compact, high-repetition-rate, GeV-scale LPA using 10 TW-class, ultra-high bandwidth pulses and mm-scale, dense plasmas. These results emphasize that investment into new pulse amplification techniques allowing for ultrahigh frequency bandwidth is as important for the design of future LPA as are the current efforts directed to increasing the pulse energy.

43 PARTICLE ACCELERATORS↗
DOE OSTI2015

Issues of incompatibility of dipole beam separation schemes with EIC physics

This report addresses the question, can the risk of an eRHIC machine be reduced by replacing the crab-cavities through a dipole field in the IR to separate the electron and hadron beams. In the following, several scenarios to integrate a separation dipole in the IR design will be described. For each of the scenarios the challenges and problems to realize this in practice will be detailed. In addition, the impact on the detector design and the EIC physics program will also be discussed. Several physics requirements need to be integrated into the interaction region design, in order to perform the physics program as described in the EIC White Paper and in the RHIC Design Study. These requirements are also described in detail on a dedicated page of the eRHIC-wiki. The main requirements are described here.

43 PARTICLE ACCELERATORS↗
DOE OSTI2016

Simulation of 6 to 3 to 1 merge and squeeze of Au77+ bunches in AGS

In order to increase the intensity per Au77+ bunch at AGS extraction, a 6 to 3 to 1 merge scheme was developed and implemented by K. Zeno during the 2016 RHIC run. For this scheme, 12 Booster loads, each consisting of a single bunch, are delivered to AGS per AGS magnetic cycle. The bunch from Booster is itself the result of a 4 to 2 to 1 merge which is carried out on a flat porch during the Booster magnetic cycle. Each Booster bunch is injected into a harmonic 24 bucket on the AGS injection porch. In order to fit into the buckets and allow for the AGS injection kicker rise time, the bunch width must be reduced by exciting quadrupole oscillations just before extraction from Booster. The bunches are injected into two groups of six adjacent harmonic 24 buckets. In each group the 6 bunches are merged into 3 by bringing on RF harmonic 12 while reducing harmonic 24. This is a straightforward 2 to 1 merge (in which two adjacent bunches are merged into one). One ends up with two groups of three adjacent bunches sitting in harmonic 12 buckets. These bunches are accelerated to an intermediate porch for further merging. Doing the merge on a porch that sits above injection energy helps reduce losses that are believed to be due to the space-charge force acting on the bunched particles. (The 6 to 3 merge is done on the injection porch because the harmonic 24 frequency on the intermediate porch would be too high for the AGS RF cavities.) On the intermediate porch each group of 3 bunches is merged into one by bringing on RF harmonics 8 and 4 and then reducing harmonics 12 and 8. One ends up with 2 bunches, each the result of a 6 to 3 to 1 merge and each sitting in a harmonic 4 bucket. This puts 6 Booster loads into each bunch. Each merged bunch needs to be squeezed into a harmonic 12 bucket for subsequent acceleration. This is done by again bringing on harmonic 8 and then harmonic 12. Results of simulations of the 6 to 3 to 1 merge and the subsequent squeeze into harmonic 12 buckets are presented in this note. In particular, they provide a benchmark for what can be achieved with the available RF voltages.

43 PARTICLE ACCELERATORS↗
DOE OSTI2016

Double and triple-harmonic RF buckets and their use for bunch squeezing in AGS

For the past several years we have merged bunches in AGS in order to achieve the desired intensity per bunch prior to injection into RHIC. The merging is done on a flat porch at or above AGS injection energy. Because the merges involve the reduction of the RF harmonic number by a factor of 2 (for a 2 to 1 merge) and then a factor of 3 (for a 3 to 1 merge), one requires RF frequencies 6hf s , 3hf s , 2hf s and hf s , where f s is the revolution frequency on the porch and h = 4 is the fundamental harmonic number. The standard AGS RF cavities cannot operate at the lowest frequencies 2hf s and hf s ; these are provided by two modified cavities. Upon completion of the merges, the bunches are sitting in harmonic h buckets. In order to be accelerated they need to be squeezed into harmonic 3h buckets. This is accomplished by producing a double-harmonic bucket in which harmonics h and 2h act in concert, and then a triple-harmonic bucket in which harmonics h, 2h, and 3h act in concert. Simulations have shown that the squeeze presents an acceptance bottleneck which limits the longitudinal emittance that can be put into the harmonic 3h bucket. In this note the areas of the double and triple-harmonic buckets are calculated explicitly, and it is shown that these go through a minimum as the RF voltages are raised to the desired values. Several RF voltage ranges are examined, and the acceptance bottleneck is determined for each of these. Finally, the acceptance bottleneck for Au77+ bunches in AGS is calculated for several RF voltage ranges. The main result is that the RF voltages for the low-frequency harmonic h and 2h cavities both must be at least 22 kV in order to achieve an acceptance of 0:6 eV s per nucleon. If the harmonic h and 2h voltages are 15 and 22 kV, respectively, then the acceptance is reduced to 0:548 eV s per nucleon.

43 PARTICLE ACCELERATORS↗
DOE OSTI2016

IBS simulation with different RF configurations in RHIC

It is a crucial task to understand the beam emittance growth during RHIC cycle and the underlying causes. One would benefit not just for the current operation of RHIC, also for the design of eRHIC. This report focuses on the Intra-Beam Scattering (IBS) contribution to the emittance growth of the proton beam with two different configurations of RF system. The answers to these questions will be given in the end of the report; can IBS explain the emittance growth all alone? What’s the difference of IBS growth rates for different RF configurations?

43 PARTICLE ACCELERATORS↗
DOE OSTI2016

Wakefields of a Beam near a Single Plate in a Flat Dechirper

At linac-based, X-ray free electron lasers (FELs), there is interest in streaking the beam by inducing the transverse wakes in a flat dechirper, by passing the beam near to one of its two jaws. For LCLS-II - as has already been done for LCLS-I - this way of using the dechirper will e.g. facilitate two-color and fresh slice schemes of running the FEL. With the beam a distance from the near wall of say b ~ 0.25 mm and from the far wall by ≳ 5 mm, the second wall will no longer affect the results. The physics will be quite different from the two plate case: with two plates the impedance has a resonance spike whose frequency depends on the plate separation 2a; in the single plate case this parameter no longer exists. Formulas for the longitudinal, dipole, and quadrupole wakes for a beam off-axis between two dechirper plates, valid for the range of bunch lengths of interest in an X-ray FEL, are given in reference 3. By taking the proper limit, we can obtain the corresponding wakes for a beam close to one dechirper plate and far from the other. This is the task we perform in this note.

43 PARTICLE ACCELERATORS↗
DOE OSTI2017

High Average Current Bunched Electron Source for RF Accelerators

High-average current high-quality electron beams are imperative for high-power RF accelerators used in various energy and environmental applications in industry, medicine, and national security as well as for advanced existing and future accelerator systems such as PIP II, particle colliders (eRHIC BNL) for cooling high-energy proton, ion, and hadron beams, storage rings, wakefield accelerators (AWA), and energy recovery linacs. The most common current approach to generate high-peak current high-brightness short electron bunches uses photoemission excited by intense laser radiation. However, to avoid overheating photocathodes are operated at a subharmonic of the linac frequency that in turn restricts the average beam current. There are also limitations in the electron-beam average current due to the average power available from drive lasers. On the other hand, the state of the art thermionic sources that produce high average current electron beams do not have yet good emission gating methods to realize sufficiently short and good quality electron bunches. We develop a robust thermionic electron source (e-source) of >1 A average current with advanced gating of the emission at the linac-frequency and its 3rd harmonic. Central to the approach is a novel scheme for energy efficient feeding of the 3rd-harmonic power in the RF gap. The cathode is attached to the gun cavity through this small emission-gating gap in which the RF modes are excited. The use of thermionic emission allows for the desired high-average current CW electron beams. Adding the 3rd emission gating harmonic shortens the electron bunches and by this means lessens impact of the RF curvature on the beam quality resulting in the smaller energy spread and bunch emittances. Such high current electron beam is suitable for injection into high-power normal- or superconducting linacs in CW mode at a high repetition rate of the linac frequency. In Phase I, we performed modeling and beam dynamics, parametric, and optimization studies. A >1A average current e-source with 200,000hrs lifetime expectancy has been demonstrated in the simulations. We have developed baseline design of the e-source and its components. It is anticipated that the e-source will be in demand for normal- and superconducting particle accelerators and will benefit many commercial and energy and environmental applications such as treating waste and potable water, sludge, stack gases, and medical waste as well as X-ray sources for medicine, sterilization, materials processing, geology, and non-intrusive imaging.

43 PARTICLE ACCELERATORS↗
DOE OSTI2018

NSLS-II upgrade proposal with splitting dipole scheme

In this note, a preliminary study of the NSLS-II upgrade lattice with splitting-dipole scheme is presented. The constraints from maintaining the layout of the ring and re-using the existing magnets have been illustrated. The linear and nonlinear beam dynamics are discussed as well.

36 MATERIALS SCIENCE↗
DOE OSTI2019

RACCAM: An example of spiral sector scaling FFA technology

The RACCAM project prototyped a spiral sector, scaling FFA dipole. It was the rst of its kind and a major component in a rapid-cycling compact ring design for a multiple beam proton- therapy installation. A brief description introduces the project and the merits of spiral, scaling FFA technology. The article then focuses on the magnet design, eld measurements and their use in beam dynamics simulations carried out to validate the design.

43 PARTICLE ACCELERATORS↗
DOE OSTI2020

Innovations in optimization and control of accelerators using methods of differential geometry and genetic algorithms (Final Report)

Online tuning of particle accelerators is necessary in order to achieve optimal machine performance. However, it is also a major challenge due to the large parameter space which must be searched and the fact that many of the desir- able objectives compete with one another, and so will not reach their optimal values simultaneously. In order to mitigate these issues, we have explored using dimension-reduction techniques to reduce the size of the parameter space which must be searched and multi-objective genetic algorithms to obtain the sets of tuning parameters which provide pareto-optimal values for the objectives. These methods have enabled us to obtain improved values of the vertical emittance at the Cornell Electron Storage Ring (CESR), and to do so with greater control of orbit errors. Algorithmic tuning is a multidisciplinary endeavour, requiring expertise in beam dynamics, diagnostics, control systems and computer science, and thus a key practical problem is to formulate a common language in which experts with different specialties can communicate. We developed a solution to this problem in the form of a generic accelerator software interface that allows for rapid prototyping of optimization and control algorithms. Our interface is built on the Experimental Physics and Industrial Control Systems (EPICS) and makes possible testing control code in simulation before deployment on real accelerators, as well as deployment of third-party optimization code.

43 PARTICLE ACCELERATORS↗