C. Boulware

Niowave (United States)

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Terry Grimm

Niowave (United States)

J. Skaritka

Brookhaven National Laboratory

I. Ben‐Zvi

Stony Brook University

S. Belomestnykh

Fermi National Accelerator Laboratory

Evgenya Simakov

Los Alamos National Laboratory

Tianmu Xin

Institute of High Energy Physics

R. Than

Brookhaven National Laboratory

I. Pinayev

Brookhaven National Laboratory

D. Kayran

Brookhaven National Laboratory

Paul Orfin

Brookhaven National Laboratory

Cooperative Institutions

Brookhaven National Laboratory

150

Deutsches Elektronen-Synchrotron DESY

RIKEN BNL Research Center

Stony Brook University

Thomas Jefferson National Accelerator Facility

Brookhaven College

Los Alamos National Laboratory

European Organization for Nuclear Research

German Institute for Adult Education

Argonne National Laboratory

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SRF and RF Systems for CeC PoP Experiment

S. Belomestnykh I. Ben‐Zvi C. Boulware J. C. Brutus Terry Grimm

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Superconducting 112 MHz QWR electron gun

S. Belomestnykh I. Ben‐Zvi C. Boulware X. Chang Terry Grimm

Brookhaven National Laboratory and Niowave, Inc. have designed and fabricated a superconducting 112 MHz quarter-wave resonator (QWR) electron gun. The first cold test of the QWR cryomodule has been completed at Niowave. The paper describes the cryomodule design, presents the cold test results, and outline plans to upgrade the cryomodule. Future experiments include studies of different photocathodes and use for the coherent electron cooling proof-of-principle experiment. Two cathode stalk options, one for multi-alkali photocathodes and the other one for a diamond-amplified photocathode, are discussed. A quarter-wave resonator concept of superconducting RF (SRF) electron gun was proposed at BNL for electron cooling hadron beams in RHIC. QWRs can be made sufficiently compact even at low RF frequencies (long wavelengths). The long wavelength allows to produce long electron bunches, thus minimizing space charge effects and enabling high bunch charge. Also, such guns should be suitable for experiments requiring high average current electron beams. A 112 MHz QWR gun was designed, fabricated, and cold-tested in collaboration between BNL and Niowave. This is the lowest frequency SRF gun ever tested successfully. In this paper we describe the gun design and fabrication, present the cold test results, and outline our plans. This gun will also serve as a prototype for a future SRF gun to be used for coherent electron cooling of hadrons in eRHIC.

Electron gun

Photocathode

Superconducting radio frequency

Bunches

Electron cooling

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Electron Beams from Needle Photocathodes and a New Theory of the Smith-Purcell Free-Electron Laser

C. Boulware

A promising source of radiation in the important terahertz (THz) region of the spectrum is the Smith-Purcell free-electron laser (SPFEL). This dissertation presents a new theory of the SPFEL, taking into account dispersion of evanescent surface waves on the grating. From the dispersion relation for these waves, it is found that the device can operate as an amplifier or as an oscillator. The gain length is calculated in the amplifier regime, as well as the growth rate and start current in the oscillator regime. The theory is supported by published computer simulations, but in conflict with previous experiment. These devices require a high-quality electron beam, and this dissertation also presents developments in needle photocathodes designed to drive an SPFEL. Data on emission current are presented as a function of voltage for various drive laser wavelengths. A simplified model is used to interpret the data as variation in the emitting area with voltage for photon energies below the cathode workfunction. Data and a new scaling law for the divergence of the beam at high current are also presented.

Free-electron laser

Free electron model

Dispersion relation

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Photo-Field Emission from Needle Cathodes

Elsevier eBooks (2003)

C. Boulware C. A. Brau

10.1016/b978-0-444-51417-2.50155-3

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Cryogenic testing of the 2.1 GHz five-cell superconducting RF cavity with a photonic band gap coupler cell

Applied Physics Letters (2016)

Sergey Arsenyev Richard J. Temkin W.B. Haynes Dmitry Shchegolkov Evgenya Simakov

We present results from cryogenic tests of the multi-cell superconducting radio frequency (SRF) cavity with a photonic band gap (PBG) coupler cell. Achieving high average beam currents is particularly desirable for future light sources and particle colliders based on SRF energy-recovery-linacs (ERLs). Beam current in ERLs is limited by the beam break-up instability, caused by parasitic higher order modes (HOMs) interacting with the beam in accelerating cavities. A PBG cell incorporated in an accelerating cavity can reduce the negative effect of HOMs by providing a frequency selective damping mechanism, thus allowing significantly higher beam currents. The multi-cell cavity was designed and fabricated of niobium. Two cryogenic (vertical) tests were conducted. The high unloaded Q-factor was demonstrated at a temperature of 4.2 K at accelerating gradients up to 3 MV/m. The measured value of the unloaded Q-factor was 1.55 × 108, in agreement with prediction.

Superconducting radio frequency

10.1063/1.4953204

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Employing photonic band gap cavities for filtering higher order modes in SRF accelerator structures

Evgenya Simakov Sergey Arsenyev W.B. Haynes Sergey Kurennoy Michael Madrid

with a PBG cell was designed and optimized for HOM damping. Monopole and dipole HOMs were simulated. The SRF cavity was fabricated and tuned. External quality factors for some HOMs were measured in a cold test. Moreover, the measurements agreed well with the simulations.

10.2172/1054674

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SRF Systems for the Coherent Electron Cooling Demonstration Experiment

S. Belomestnykh I. Ben‐Zvi J. C. Brutus J. Huang D. Kayran

A short 22-MeV linac under development at BNL will provide high charge, low repetition rate beam for the Coherent electron Cooling (CeC) demonstration experiment in RHIC. The linac will include a 112 MHz SRF gun and a 704 MHz five-cell accelerating SRF cavity. The paper describes the two SRF systems, discusses the project status, first test results and schedule.

Electron cooling

Repetition (rhetorical device)

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Electron Sources for Future Lightsources, Summary and Conclusions for the Activities during FLS 2012

arXiv (Cornell University) (2013)

T. Kamps Carlos Hernández-García C. Boulware J. Corlett K. Harkay

This paper summarizes the discussions, presentations, and activity of the Future Light Sources Workshop 2012 (FLS 2012) working group dedicated to Electron Sources. The focus of the working group was to discuss concepts and technologies that might enable much higher peak and average brightness from electron beam sources. Furthermore the working group was asked to consider methods to greatly improve the robustness of operation and lower the costs of providing electrons.

10.48550/arxiv.1307.1571

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Design and operation of a superconducting quarter-wave electron gun

Physical Review Special Topics - Accelerators and Beams (2011)

J. R. Harris Kate Ferguson John Lewellen Sean P. Niles B. Rusnak

Superconducting radio-frequency electron guns are viewed by many as the preferred technology for generating the high-quality, high-current beams needed for future high power free-electron lasers and energy recovery linacs. All previous guns of this type have employed elliptical cavities, but there are potential advantages associated with other geometries. Here we describe the design, commissioning, and initial results from a superconducting radio-frequency electron gun employing a quarter-wave resonator configuration, the first such device to be built and tested. In initial operation, the gun has generated beams with bunch charge in excess of 78 pC, energy of 469 keV, and normalized rms emittances of about $4.9\text{ }\text{ }\ensuremath{\mu}\mathrm{m}$. Currently, bunch charge is limited by the available drive laser energy, and beam energy is limited by x-ray production and the available rf power. No fundamental limits on beam charge or energy have been encountered, and no high-field quenching events have been observed.

Electron gun

10.1103/physrevstab.14.053501

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Citations (30)

DEVELOPMENT OF A SUPERCONDUCTING 500 MHZ MULTI-SPOKE CAVITY FOR ELECTRON LINACS *

D. Gorelov C. Boulware Terry Grimm Jean Delayen Christopher Hopper

Multi-spoke cavities are well-known options for acceleration of heavy and light ions. A recently developed multi-spoke cavity for β=1 presents an attractive opportunity to use this cavity type for electron accelerators. One of the main attractive features of this cavity type is its compactness for relatively low frequency. A simplified design at 500 MHz allowed building of a multi-spoke cavity and cryomodule in a 2year time frame with confidence and development of effective manufacturing techniques. It also constitutes an important step in proving the usefulness of this kind of cavity design for new applications in the electron machines. Niowave is now in a position to build on the success of this cavity to help advance the design of superconducting electron accelerators. Accelerating voltage of more then 6.7 MV in a single cavity at 4.2 K is expected with peak electric field of less then 22 MV/m, and peak magnetic field of less then 80 mT. The paper discusses the fabrication challenges of the complete cavity and the cryomodule, as well as room temperature and cryogenic test results.

Superconducting radio frequency

Position (finance)

Cavity wall

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