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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Multiple bunch HOM evaluation for ERL cavities

In this paper we investigate the effect of the bunch pattern in a linac on the Higher Order Mode (HOM) power generation. The future ERL-based electron–ion collider eRHIC at BNL is used as an illustrative example. This ERL has multiple high current Superconducting Radiofrequency (SRF) 5-cell cavities. The HOM power generated when a single bunch traverses the cavity is estimated by the corresponding loss factor. Multiple re-circulations through the Energy Recovery Linac (ERL) create a specific bunch pattern. In this case the loss factor can be different than the single bunch loss factor. HOM power can vary dramatically when the ERL bunch pattern changes. The HOM power generation can be surveyed in the time and frequency domains. We estimate the average HOM power in a 5-cell cavity with different ERL bunch patterns.

43 PARTICLE ACCELERATORS↗
DOE OSTI2017

Conceptual design of a high real-estate gradient cavity for a SRF ERL

The term “real-estate gradient” is used to describe the energy gain provided by an accelerating structure per actual length it takes in the accelerator. given that the length of the tunnel available for the accelerator is constrained, the real-estate gradient is an important measure of the efficiency of a given accelerator structure. When designing an accelerating cavity to be efficient in this sense, the unwanted Higher Order Mode (HOM) fields should be reduced by suitable HOM dampers. This is a particularly important consideration for high current operation. The additional RF components might take longitude space and reduce the total accelerating efficiency. We describe a new high efficiency 5-cell cavity with the dampers included. The total length of the cavity is reduced by 13% as compared to a more conventional design without compromising the cavity fundamental-mode performance. In addition, the HOM impedance is reduced for a higher Beam-Break-Up (BBU) threshold of operating current. In this article, we consider an example, a possible application at the eRHIC Energy Recovery Linac (ERL).

43 PARTICLE ACCELERATORS↗
DOE OSTI2019

EXPERIMENTAL VERIFICATION OF TRANSPARENT SPIN MODE IN RHIC

High electron and ion polarizations are some of the key design requirements of a future Electron Ion Collider (EIC). The transparent spin mode, a concept inspired by the figure 8 ring design of JLEIC, is a novel technique for preservation and control of electron and ion spin polarizations in a collider or storage ring. It makes the ring lattice "invisible" to the spin and allows for polarization control by small quasi-static magnetic fields with practically no effect on the beam’s orbital characteristics. It offers unique opportunities for polarization maintenance and control in Jefferson Lab’s JLEIC and in BNL’s eRHIC. The transparent spin mode has been demonstrated in simulations and we now plan to test it experimentally. We present a design of an experiment using a polarized proton beam stored in one of the RHIC rings. In the experiment, one of the RHIC rings is configured in the transparent spin mode by aligning the axes of its two Siberian snakes. The experiment goals, procedures, hardware requirements and expected results are presented.

Morozov, V.S.↗
DOE OSTI2020

The US Electron Ion Collider Accelerator Designs

With the completion of the National Academies of Sciences Assessment of a US Electron-Ion Collider, the prospects for construction of such a facility have taken a step forward. This paper provides an overview of the two site-specific EIC designs: JLEIC (Jefferson Lab) and eRHIC (BNL) as well as brief overview of ongoing EIC R&D.

43 PARTICLE ACCELERATORS↗
DOE OSTI2016

A Magnetized Injector for Electron Cooling Applications

A number of electron-ion collider facilities for nuclear physics research are under consid- eration in the United States. At Brookhaven National Lab (BNL), the eRHIC (electron Relativistic Heavy Ion Collider) facility uses the existing ion/proton facility and augments it with an electron accelerator. Jefferson Lab plans to use the existing CEBAF machine and add an ion/proton accelerator, as part of the Jefferson Lab Electron-Ion Collider (JLEIC). All such facilities require that the ion beams be cooled in order to reach the lu- minosity goals. Different methods of cooling the ions using an electron beam are envisaged. BNL is pursuing coherent electron cooling and non-magnetized, bunch beam cooling, while Jefferson Lab is considering magnetized cooling. In addition to electron cooling, magnetized beams are of interest for other applica- tions such as flat beam klystrons, and novel means for producing bright beams for micro- undulators and compact X-ray sources. For example, flat beams generated from a mag- netized injector, in conjunction with low emittance, enable RF sources with frequencies above 100 GHz. While the market for high performance injectors for electron cooling is limited, the potential market for high frequency RF sources and compact X-ray systems is considerable. Thus, the design methodologies developed in this project have a wide range of applicability. In this Phase I project, Xelera Research LLC performed simulations and calculations to develop a prototype design for a magnetized electron injector that can be used as a source for cooling an ion beam. We developed general design methodologies and techniques that can then be applied to specific machine designs or other applications requiring magnetized injectors. In Phase II, the design will be further optimized, and then built in collaboration with a national lab partner. Xelera Research has many years of experience with electron sources and all of the skills and tools necessary to successfully carry out this project.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

A model of polarized-beam AGS in the ray-tracing code Zgoubi

A model of the Alternating Gradient Synchrotron, based on the AGS snapramps, has been developed in the stepwise ray-tracing code Zgoubi. It has been used over the past 5 years in a number of accelerator studies aimed at enhancing RHIC proton beam polarization. It is also used to study and optimize proton and Helion beam polarization in view of future RHIC and eRHIC programs. The AGS model in Zgoubi is operational on-line via three different applications, ’ZgoubiFromSnaprampCmd’, ’AgsZgoubiModel’ and ’AgsModelViewer’, with the latter two essentially interfaces to the former which is the actual model ’engine’. All three commands are available from the controls system application launcher in the AGS ’StartUp’ menu, or from eponymous commands on shell terminals. Main aspects of the model and of its operation are presented in this technical note, brief excerpts from various studies performed so far are given for illustration, means and methods entering in ZgoubiFromSnaprampCmd are developed further in appendix.

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 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 OSTI2017

Luminosity geometric reduction factor from colliding bunches with different lengths

In the interaction point of the future electron-Ion collider eRHIC, the electron beam bunches are at least one order of magnitude shorter than the proton beam bunches. With the introduction of a crossing angle, the actual number of collisions resulting from the bunch collision gets reduced. Here we derive the expression for the luminosity geometric reduction factor when the bunches of the two incoming beams are not equal.

43 PARTICLE ACCELERATORS↗
DOE OSTI2017

Polarized e-bunch acceleration at Cornell RCS: Tentative tracking simulations

An option as an injector into eRHIC electron storage ring is a rapid-cyclic synchrotron (RCS). Rapid acceleration of polarized electron bunches has never been done, Cornell synchrotron might lend itself to dedicated tests, which is to be first explored based on numerical investigations. This paper is a very preliminary introduction to the topic.

43 PARTICLE ACCELERATORS↗
DOE OSTI2017

Intrinsic resonances and AC-dipole simulations of 3He in the AGS Booster

Polarized 3 He collisions are part of future RHIC physics programs and of the eRHIC project. The anomalous magnetic moment of 3 He (G=-4.184) is roughly three times greater than that of protons (G=1.793), a polarized species that is already used at the Collider-Accelerator complex at BNL. Because of the higher anomolous magnetic moment and possibly injecting into the AGS at rigidities beyond 7 T • m, 3 He may have to cross depolarizing intrinsic resonances while accelerating in the Booster. To overcome these strong intrinsic resonances we look to an AC-dipole, which will need to be installed in the Booster. An AC-dipole is a magnet that induces large betatron oscillations which forces the entire bunch to experience a stronger resonance and induce a spin flip of all particles. An artificial intrinsic resonance is created, with close proximity to the original intrinsic resonance, which requires simulations to gauge what magnet strength is required. Simulations have been performed using zgoubi regarding the resonances 0 + v y , 12 - v y , and 6 + v y and show that the AC-dipole is effective at overcoming these resonances. Benefits of avoiding the 0 + v y and crossing the 12 - v y and 6 + v y in the Booster presents the advantage of allowing injection above the 0 + v y in the AGS and minimizes the orbit distortions from the snakes.

43 PARTICLE ACCELERATORS↗
DOE OSTI2018

Overcoming proton and 3 He intrinsic resonances in the AGS Booster with an ac dipole

Polarized 3 He collisions are part of future physics programs for RHIC and eRHIC. Due to optics perturbations from the AGS partial helical dipoles, it is desired to extract 3 He from the Booster at Gγ = –10.5, which involves crossing the 12 – ν y and the 6 + ν y intrinsic resonances. To overcome these resonances, an ac dipole is being designed to be installed in the Booster. The effect of an ac dipole is to generate artificial spin-resonance by inducing vertical betatron oscillations that guide the bunch through the horizontal fields of the quadrupoles. An experimental study with Au beam was performed to confirm that the available aperture is sufficient to accommodate these large vertical betatron oscillations. Simulations for 3 He crossing the aforementioned resonances have been performed and display the effectiveness of the ac dipole at spin-flipping in the Booster. Due to the rapid acceleration of the Booster, the ac dipole tune will change as much as 0.0028 over the course of an ac dipole cycle, which changes the amplitude of these betatron oscillations over the course of the cycle. Through simulation, it is shown that the varying betatron amplitude does not dilute the effectiveness of the ac dipole. Sextupoles are used to provide further control over the tune spread, where RF-dual harmonics are used to control the bunch length, and to reduce the momentum spread.

43 PARTICLE ACCELERATORS↗
DOE OSTI2018

Combined function magnets in the RHIC electron storage ring

The maximum electron beam intensity, and therefore the luminosity, of the electron-ion collider eRHIC is limited by the available RF power, which has been chosen as 10 MW. To maximize the beam intensity in the presence of this limitation the bending radius needs to be chosen as large as possible. While this is generally accomplished by a FODO lattice in the arcs due to its high dipole packing factor, the quadrupoles in a separated-function lattice do not contribute to bending. The use of combined-function magnets instead of regular quadrupoles would allow the quadrupoles to contribute to the bending as well, which increases the actual bending radius of the machine. However, this measure also affects the damping distribution in the machine, and may even result in anti-damping, making the lattice not suitable as a storage ring. In the following we demonstrate how to convert a separated-function lattice to a combined-function lattice while simultaneously preserving the damping distribution.

43 PARTICLE ACCELERATORS↗
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↗
DOE OSTI2019

A Magnetized Electron Source For Ion Beam Cooling

A number of electron-ion collider facilities for nuclear physics research are under consid- eration in the United States. At Brookhaven National Lab (BNL), the eRHIC (electron Relativistic Heavy Ion Collider) facility would augment the existing ion/proton facility with an electron accelerator. Thomas Jefferson National Accelerator Facility (JLab) plans to use the existing CEBAF machine and add an ion/proton accelerator, as part of the Jefferson Lab Electron-Ion Collider (JLEIC). All such facilities require cooling of the ion beams in order to reach the luminosity goals. Different methods of cooling the ions using an electron beam are envisaged. BNL is pursuing coherent electron cooling and non-magnetized, bunched-beam cooling, while JLab is considering magnetized cooling. In addition to electron cooling, magnetized beams are of interest for other applica- tions, such as flat beam klystrons and novel means for producing bright beams for micro- undulators and compact X-ray sources. For example, flat beams generated from a mag- netized injector, in conjunction with low emittance, enable RF sources with frequencies above 100 GHz. While the market for high-performance injectors for electron cooling is limited, the market for high-frequency RF sources and compact X-ray systems is con- siderable. Thus, the design methodologies developed in this project have a wide range of applicability. In Phase I of this SBIR project, Xelera Research LLC performed simulations and calcu- lations to develop a prototype design for a magnetized electron injector that can be used as a source for cooling an ion beam. We developed general design methodologies and tech- niques that are applicable not only to specific machine designs but to other applications requiring magnetized injectors as well. In this Phase II SBIR project, Xelera Research LLC, in collaboration with a team at JLab, designed, built, and tested a thermionic elec- tron source for driving a magnetized electron cooler in a future electron-ion collider project. This device was delivered to JLab in July 2019 and achieved first beam in December 2019.

43 PARTICLE ACCELERATORS↗
DOE OSTI2020

High Energy ERLs for Electron Cooling

Future electron-ion colliders such as the recently approved eRHIC collide high-intensity ion beams with high current electron beams. The electron beams take advantage of synchrotron radiation to damp emittances but the ion beams must be cooled via some beam-cooling mechanism, including electron cooling. The ion energies are typically a few hundreds of GeV per nucleon. At this energy, a DC cooler powered by an electrostatic accelerator, the preferred cooling approach on existing machines, is not feasible. An ERL, in principle, can provide the high current and brightness to cool these high-brightness ion beams. The beam quality requirements are much different from previous ERLs designs used for FELs. The cooling bunch must be very long to match the ion beam and the relative energy spread must be very small. Incoherent cooling can be enhanced with magnetized beams, but the magnetization must be maintained throughout the ERL. An alternate cooling mechanism, the so-called Coherent Electron Cooling, is, in principle, stronger and can be done with non-magnetized beams. We will present two applications of an ERL to high energy electron cooling and describe some of the technical challenges that must be overcome to operate such an ERL

Benson, Stephen↗
DOE OSTI2019

Laser-driven Polarized Deuterium Source

Polarized light ion beams are essential to the physics program for a future electron-ion collider (EIC), and polarized deuterons have been identified as essential tools to probe the sea quark and gluon distributions in studies of hadronization. Polarized deuterons form an especially unique system for study by providing a combination of quark and nuclear physics, and thus can yield new insights in the understanding of hadron structure that cannot be achieved with other polarized nuclei. Both the Jefferson Lab Electron-Ion Collider (JLEIC) and the electron-ion collider at Brookhaven National Lab (eRHIC) machine design concepts have integrated polarized deuteron transport into their designs, but there are currently no operational polarized deuteron beam sources in the United States. A new method for production of neutral polarized atomic deuterium beams is discussed. The method utilizes infrared stimulated Raman adiabatic passage (IR STIRAP) in the production of polarized deuterium halide molecules, from which polarized deuterium atoms can be accessed through photodissociation. The method has the potential to generate neutral polarized atomic deuterium beams with densities that are orders of magnitude greater than that in existing devices.

Sy, A.↗
DOE OSTI2020

MCBI in an Electron-Ion Collider

The luminosity performance for an electron-ion collider demands high-current operation for both the electron and ion beams, for a wide range of collision energies. This poses many challenges on the beam stability with regard to collective effects. In this paper, we present preliminary estimations of coherent instabilities for both of the EIC designs, i.e., JLEIC and eRHIC. Mitigation mechanisms or schemes envisioned for suppression of the instabilities are also discussed.

Li, Rui↗