Physics - Accelerator Physics Publications (50)

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Physics - Accelerator Physics Publications

In this paper, a simple method is proposed to extend the photon energy range of a soft x-ray self-seeding free-electron laser (FEL). A normal monochromator is first applied to purify the FEL spectrum and provide a coherent seeding signal. This coherent signal then interacts with the electron beam in the following reverse tapered undulator section to generate strong coherent microbunchings while maintain the good quality of the electron beam. Read More


The Dragon-II linear induction accelerator is able to provide triple-pulse electron beams with an adjustable pulse spacing at the minimum of 300 ns. As a main determinant of the image quality, the X-ray spot size is usually quoted as an evaluation of the resolving power. The pinhole imaging method is applied to measure the two-dimensional spatial distribution of the triple-pulse X-ray source, by which the azimuthal asymmetry of the source can be analyzed. Read More


Using a particle-in-cell (PIC) code, we investigated the possibilities for emittance growth through the quadrupole magnets of the system used to transport the high-current electron beam from an induction accelerator to the bremsstrahlung converter target used for flash radiography. We found that even highly mismatched beams exhibited little emittance growth (< 6%), which we attribute to softening of their initial hard edge current distributions. We also used this PIC code to evaluate the accuracy of emittance measurements using a solenoid focal scan following the quadrupole magnets. Read More


The Dual-Axis Radiographic Hydrotest (DARHT) facility uses bremsstrahlung radiation source spots produced by the focused electron beams from two linear induction accelerators (LIAs) to radiograph large hydrodynamic experiments driven by high explosives. Radiographic resolution is determined by the size of the source spot, and beam emittance is the ultimate limitation to spot size. Some of the possible causes for the emittance growth in the DARHT LIA have been investigated using particle-in-cell (PIC) codes, and are discussed in this article. Read More


The dual-axis radiography for hydrodynamic testing (DARHT) facility at Los Alamos National Laboratory uses two electron linear-induction accelerators (LIA) to produce the source spots for perpendicular flash radiographs of a dynamic experiment.Manipulating the beam current is a means for adjusting the dose, and one way to do this is to change the size of the cathode. This article describes simulations undertaken to develop scaling laws for use as design tools in changing the Axis-1 beam current by changing the cathode size. Read More


Investigation of coherent Smith-Purcell Radiation (SPR) spectral characteristics was performed both experimentally and by numerical simulation. The measurement of SPR spectral line shapes of different diffraction orders was carried out at KEK LUCX facility. A pair of room-temperature Schottky barrier diode (SBD) detectors with sensitivity bands of $60-90$~GHz and $320-460$~GHz was used in the measurements. Read More


Beam tracking software for accelerators can be divided into two categories: fast envelope simula- tions limited to linear beam optics, and slower multiparticle simulations that can model nonlinear effects. To find a middle ground between these approaches, we introduce virtual parameters in position and momentum which exhibit a cross-dependency (i.e. Read More


A new bunch current measurement system has been implemented in Hefei Light Source II (HLS II) recently. This system is based on the photodetector and synchrotron radiation. This paper presents the system structure and a waveform reconstruction algorithm. Read More


The magnetron H- ion sources developed in the 1970s currently in operation at Fermilab provide beam to the rest of the accelerator complex. A series of modifications to these sources have been tested in a dedicated offline test stand with the aim of improving different operational issues. The solenoid type gas valve was tested as an alternative to the piezoelectric gas valve in order to avoid its temperature dependence. Read More


2017Jan
Affiliations: 1Fermilab, 2Fermilab, 3Fermilab, 4Fermilab, 5Fermilab, 6Fermilab, 7Fermilab, 8Fermilab, 9Fermilab, 10Fermilab, 11Fermilab, 12Fermilab, 13Fermilab, 14Fermilab, 15Fermilab, 16Fermilab, 17Colorado State U.

A CW-compatible, pulsed H- superconducting linac "PIP-II" is being planned to upgrade Fermilab's injection complex. To validate the front-end concept, a test accelerator (The PIP-II Injector Test, formerly known as "PXIE") is under construction. The warm part of this accelerator comprises a 10 mA DC, 30 keV H- ion source, a 2 m-long Low Energy Beam Transport (LEBT), a 2. Read More


A plasma beam dump uses the collective oscillations of plasma electrons to absorb the kinetic energy of a particle beam. In this paper, a modified passive plasma beam dump scheme is proposed using either a gradient or stepped plasma profile to maintain a higher decelerating gradient compared to a uniform plasma. The improvement is a result of the plasma wavelength change preventing the re-acceleration of low energy particles. Read More


The experimental device for generation of undulator radiation in terahertz wavelength region by use of undulator on ferromagnets is created. The device is based on a beam of a microtrone with the energy 7.5 MeV. Read More


The undulator is a critical component to produce synchrotron radiation and free electron laser. When a Bessel light beam carrying the orbit angular momentum co-propagates with an electron beam, a net transverse deflection force will be subjected to the electron beam. As a result of dephasing effect, the deflection force will oscillate acting as an undulator. Read More


2017Jan
Affiliations: 1Fermilab, 2Fermilab, 3Fermilab, 4Fermilab, 5Fermilab

As SCRF particle accelerator technology advances the need for "low particulate" and "particle free" vacuum systems becomes greater and greater. In the course of the operation of these systems, there comes a time when various instruments have to be temporarily attached for diagnostic purposes: RGAs, leak detectors, and additional pumps. In an effort to make the additions of these instruments easier and more time effective, we propose to use KF style flanges for these types of temporary diagnostic connections. Read More


2017Jan
Authors: A. Vivoli1
Affiliations: 1Fermilab

The U.S. Particle Physics Project Prioritization Panel (P5) report encouraged the realization of Fermilab's Proton Improvement Plan II (PIP-II) to support future neutrino programs in the United States. Read More


2017Jan
Affiliations: 1Fermilab, 2Fermilab, 3Fermilab, 4Fermilab, 5Fermilab, 6Fermilab

The readout electronics for the resonant beam position monitors (BPMs) in the Fermilab Switchyard (SY) have been upgraded, utilizing a low noise amplifier transition board and Fermilab designed digitizer boards. The stripline BPMs are estimated to have an average signal output of between -110 dBm and -80 dBm, with an estimated peak output of -70 dBm. The external resonant circuit is tuned to the SY machine frequency of 53. Read More


In this conceptual design report the possible options for an upgrade of the REX/HIE-ISOLDE charge breeder are discussed. The performance requirements imposed by standard HIE-ISOLDE physics as well as injection into a possible future TSR@ISOLDE are discussed, and thereafter translated into machine parameters. Experimental results from tests of a high-current and high-density electron gun performed at Brookhaven National Laboratory are presented, and alternative gun designs are discussed. Read More


Inverse Compton scattering (ICS) is a unique mechanism for producing fast pulses - picosecond and below - of bright X- to gamma-rays. These nominally narrow spectral bandwidth electromagnetic radiation pulses are efficiently produced in the interaction between intense, well-focused electron and laser beams. The spectral characteristics of such sources are affected by many experimental parameters, such as the bandwidth of the laser, and the angles of both the electrons and laser photons at collision. Read More


A facility based on a next-generation, high-flux D-D neutron generator has been commissioned and it is now operational at the University of California, Berkeley. The current generator design produces near monoenergetic 2.45 MeV neutrons at outputs of 10^8 n/s. Read More


The emitted energy of electrons is calculated in relativistic strophotron. It is shown, that it is superposition of amplification at harmonics of main resonance frequency of the system. Read More


Deviation of the Fast Faraday Cup signal from the longitudinal shape of the measured bunch is estimated, and a simple formula for the increase of the signal rms width is suggested. Read More


Thomson scattering of intense laser pulses from relativistic electrons allows us to generate high-brightness and tunable-polarization X/{\gamma}-ray pulses. This paper demonstrates the polarization control of the Thomson scattering source experimentally. The polarization of X/{\gamma}-ray is related to incident polarized laser beams, which is controlled by rotating a quarter-wave plate. Read More


We report on the status of the Fermilab accelerator complex, including recent performance, upgrades in progress, and plans for the future. Beam delivery to the neutrino experiments surpassed our goals for the past year. The Proton Improvement Plan is well underway with successful 15 Hz beam operation. Read More


We present an upgrade to the particle-in-cell ion beam simulation code OPAL that enables us to run highly realistic simulations of the spiral inflector system of a compact cyclotron. This upgrade includes a new geometry class and field solver that can handle the complicated boundary conditions posed by the electrode system in the central region of the cyclotron both in terms of particle termination, and calculation of self-fields. Results are benchmarked against the analytical solution of a coasting beam. Read More


2016Dec

A neutrino factory or muon collider requires the capture and cooling of a large number of muons. Scenarios for capture, bunching, phase-energy rotation and initial cooling of {\mu}'s produced from a proton source target have been developed, for neutrino factory and muon collider scenarios. They require a drift section from the target, a bunching section and a {\phi}-{\delta}E rotation section leading into the cooling channel. Read More


2016Dec
Affiliations: 1Fermilab, 2Brookhaven, 3Mississippi U., 4Mississippi U.

A high-energy muon collider scenario require a "final cooling" system that reduces transverse emittance by a factor of ~10 while allowing longitudinal emittance increase. The baseline approach has low-energy transverse cooling within high-field solenoids, with strong longitudinal heating. This approach and its recent simulation are discussed. Read More


The Mu2e experiment at Fermilab is being designed to study the coherent neutrino-less conversion of a negative muon into an electron in the field of a nucleus. This process has an extremely low probability in the Standard Model, and its observation would provide unambiguous evidence for beyond the standard model physics. The Mu2e design aims to reach a single-event-sensitivity of about $2. Read More


It is shown that the possibility to create the free electron laser without inversion (FELWI) has a threshold behavior on the field of intensity of amplified wave. In the collective approach, the description of threshold conditions is given. It is shown that the threshold of observation of amplification without inversion is sufficiently high, which hampers essentially the possibility of experimental realization of the FELWI. Read More


For low energy operation strategy we advocate utilization of many short wigglers in contrast with single long wiggler. This allows begin to operate very naturally with few strong field wigglers giving necessary damping time on expense of energy spread. By adding more and more wigglers in the ring, as these wigglers are manufactured and tuned, the field in the wigglers will be decreased, keeping necessary damping. Read More


The 2014 P5 report indicated the accelerator-based neutrino and rare decay physics research as a centrepiece of the US domestic HEP program. Operation, upgrade and development of the accelerators for the near-term and longer-term particle physics program at the Intensity Frontier face formidable challenges. Here we discuss key elements of the accelerator physics and technology R&D program toward future multi-MW proton accelerators. Read More


2016Dec
Affiliations: 1NICADD, DeKalb and Fermilab, 2NICADD, DeKalb, 3Fermilab, 4Fermilab, 5Fermilab, 6Shanghai, Inst. Optics, Fine Mech., 7UC, Irvine, 8UC, Irvine, 9UC, Irvine, 10Michigan U. and Palaiseau, Lab. Opt. Appl., 11Michigan U. and Palaiseau, Lab. Opt. Appl.

This paper describes simulation analyses on beam and laser (X-ray)-driven accelerations in effective nanotube models obtained from Vsim and EPOCH codes. Experimental setups to detect wakefields are also outlined with accelerator facilities at Fermilab and NIU. In the FAST facility, the electron beamline was successfully commissioned at 50 MeV and it is being upgraded toward higher energies for electron accelerator R&D. Read More


The main resonance frequency is shown to depend on the initial conditions of the electron, and in particular on its initial transversal coordinate xo. This dependence is shown to give rise to a very strong inhomogeneous broadening of the spectral lines. The broadening can become large enough for the spectral lines to overlap with each other. Read More


We present results on the effects of interstitial oxygen and carbon on a bulk-niobium superconducting radio-frequency cavity. Previous experiments have shown that high-temperature (~800 $^\circ\text{C}$) nitrogen-doping plays the dominant role in the reduction of the electron mean free path in the RF penetration layer of niobium that leads to a decrease in microwave surface resistance and a suppression the temperature-dependent component of the surface resistance with increasing accelerating gradient. In this work, we show that oxygen and carbon-doping has very similar effects on cavity performance, demonstrating that these effects are not unique to nitrogen. Read More


2016Dec
Affiliations: 1Fermilab, 2Fermilab and Northern Illinois U.

A portion of the remnant Tevatron program infrastructure at Fermilab is being reconfigured to be used for the generation and delivery of proton and muon beams for new high-precision particle physics experiments. With the 8 GeV Booster as its primary source, the Mu2e experiment will receive 8.9 GeV/c bunched beam on target, after being stored and slow spilled from the Delivery Ring (DR) -- a refurbished debuncher ring from Tevatron antiproton production. Read More


2016Dec
Affiliations: 1Fermilab, 2Fermilab, 3Brookhaven, 4Mississippi U., 5Mississippi U., 6LBL, Berkeley, 7MUONS Inc., Batavia

The Muon Accelerator Program (MAP) has completed a four-year study on the feasibility of muon colliders and on using stored muon beams for neutrinos. That study was broadly successful in its goals, establishing the feasibility of heavy lepton colliders (HLCs) from the 125 GeV Higgs Factory to more than 10 TeV, as well as exploring using a {\mu} storage ring (MSR) for neutrinos, and establishing that MSRs could provide factory-level intensities of $\nu_e (\bar{\nu}_e)$ and $\bar{\nu}_\mu$ $({\nu}_\mu)$ beams. The key components of the collider and neutrino factory systems were identified. Read More


Spectral intensity of spontaneous radiation is calculated in relativistic strophotron. It is shown, that it in the strophotron is given by a superposition of contributions from emission at different (odd) harmonics of the main resonance frequency . The main resonance frequency is shown to depend on the initial conditions of the electron, and in particular on its initial transversal coordinate . Read More


In this paper, we present a 3-D one step photoemission model that can be used to calculate the quantum efficiency and momentum distributions of electrons photoemitted from ordered single crystal surfaces close to the photoemission threshold. Using Ag(111) as an example, we show that the model can not only calculate the quantum efficiency from the surface state accurately without using any ad hoc parameters, but also provides a theoretical quantitative explanation of the vectorial photoelectric effect. This model in conjunction with other band structure and wave function calculation techniques can be effectively used to screen single crystal photoemitters for use as electron sources for particle accelerator and ultrafast electron diffraction applications. Read More


2016Dec
Affiliations: 1Fermilab, 2Mississippi U., 3Mississippi U., 4IIT, Chicago, 5IIT, Chicago

Emittance exchange mediated by wedge absorbers is required for longitudinal ionization cooling and for final transverse emittance minimization for a muon collider. A wedge absorber within the MICE beam line could serve as a demonstration of the type of emittance exchange needed for 6-D cooling, including the configurations needed for muon colliders. Parameters for this test are explored in simulation and possible experimental configurations with simulated results are presented. Read More


2016Dec
Affiliations: 1Northern Illinois U., 2Northern Illinois U., 3Fermilab, 4Fermilab, 5Fermilab, 6Fermilab, 7Fermilab, 8Fermilab, 9Brigham Young U., Rexburg, 10Kansas U., 11Sokendai, Tsukuba

X-rays have widespread applications in science and industry, but developing a simple, compact, and high-quality X-ray source remains a challenge. Our collaboration has explored the possible use of channeling radiation driven by a 50 MeV low-emittance electron beam to produce narrowband hard X-rays with photon energy of 40 to 140 keV. Here we present the simulated X-ray spectra including the background bremsstrahlung contribution, and a description of the required optimization of the relevant electron-beam parameters necessary to maximize brilliance of the resulting X-ray beam. Read More


2016Dec
Affiliations: 1MUONS Inc., Batavia, 2MUONS Inc., Batavia, 3MUONS Inc., Batavia, 4Fermilab, 5Fermilab, 6Fermilab

A novel concept of a high-power magnetron transmitter allowing dynamic phase and power control at the frequency of locking signal is proposed. The transmitter compensating parasitic phase and amplitude modulations inherent in Superconducting RF (SRF) cavities within closed feedback loops is intended for powering of the intensity-frontier superconducting accelerators. The concept uses magnetrons driven by a sufficient resonant (injection-locking) signal and fed by the voltage which can be below the threshold of self-excitation. Read More


2016Dec
Affiliations: 1Fermilab, 2Fermilab, 3Fermilab, 4Fermilab, 5Fermilab, 6Fermilab, 7Fermilab, 8Fermilab, 9Fermilab, 10Fermilab, 11Fermilab, 12Fermilab, 13Fermilab, 14Fermilab, 15Fermilab, 16Fermilab, 17Fermilab, 18Fermilab, 19Fermilab, 20Fermilab, 21Fermilab, 22Fermilab, 23Fermilab, 24Fermilab, 25Fermilab, 26Rutherford

The Long Baseline Neutrino Facility (LBNF) project will build a beamline located at Fermilab to create and aim an intense neutrino beam of appropriate energy range toward the DUNE detectors at the SURF facility in Lead, South Dakota. Neutrino production starts in the Target Station, which consists of a solid target, magnetic focusing horns, and the associated sub-systems and shielding infrastructure. Protons hit the target producing mesons which are then focused by the horns into a helium-filled decay pipe where they decay into muons and neutrinos. Read More


2016Dec
Affiliations: 1Colorado State U., 2Colorado State U. and Ljubljana U., 3Colorado State U., 4Fermilab, 5Fermilab, 6Fermilab, 7Fermilab

As part of the PIP-II Injector Experiment (PXIE) accelerator, a four-vane radio frequency quadrupole (RFQ) accelerates a 30-keV, 1-mA to 10-mA H- ion beam to 2.1 MeV. It is designed to operate at a frequency of 162. Read More


The description of FELWI in the collective approach, is given The dispersion equations are obtained and discussed for both Raman and Thompson regimes. Read More


NORMA is a design for a normal-conducting race track fixed-field alternating-gradient accelerator (FFAG) for protons from 30 to 350 MeV. In this article we show the development from the nominal lattice design to a model implemented with field maps from 2D and 3D FEM magnet designs. We show that while the fields from the 2D model are sufficient, adjustments must be made lattice to account for differences in the fringe-field and full 3D models. Read More


The Integrable Optics Test Accelerator (IOTA) is a storage ring for advanced beam physics research currently being built and commissioned at Fermilab. It will operate with protons and electrons using injectors with momenta of 70 and 150 MeV/c, respectively. The research program includes the study of nonlinear focusing integrable optical beam lattices based on special magnets and electron lenses, beam dynamics of space-charge effects and their compensation, optical stochastic cooling, and several other experiments. Read More


2016Dec
Affiliations: 1Colorado State U., 2Colorado State U. and Ljubljana U. and Element Aero, Chicago, 3Colorado State U. and Element Aero, Chicago, 4Fermilab

At present, a variety of image-based diagnostics are used in particle accelerator systems. Often times, these are viewed by a human operator who then makes appropriate adjustments to the machine. Given recent advances in using convolutional neural networks (CNNs) for image processing, it should be possible to use image diagnostics directly in control routines (NN-based or otherwise). Read More


2016Dec
Affiliations: 1Colorado State U., 2Colorado State U., 3Colorado State U., 4Fermilab, 5Fermilab, 6Fermilab, 7Fermilab, 8Fermilab

For the PIP-II Injector Test (PI-Test) at Fermilab, a four-vane radio frequency quadrupole (RFQ) is designed to accelerate a 30-keV, 1-mA to 10-mA, H- beam to 2.1 MeV under both pulsed and continuous wave (CW) RF operation. The available headroom of the RF amplifiers limits the maximum allowable detuning to 3 kHz, and the detuning is controlled entirely via thermal regulation. Read More


The scheme with quadrupole lenses is presented for realization relativistic strophotron type Free electron laser. Equations of motion are solved and trajectories are found. It is shown, that movement of electrons in presented scheme is stable in both transverse directions. Read More


The equations of particle motion in the FELWI are derived using Hamiltonian formalism. In small signal regime the uncoupled one dimensional phase equation is derived in the form of pendulum equation. For the practical estimations the same equation along with the equation of particle energy change are solved using perturbation theory and the expressions for gain in FEL regime and particle angle dependence of energy at the exit of first undulator are obtained. Read More