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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,081 records · Page 60
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Electron Cloud Measurements in Fermilab Booster

Fermilab Booster synchrotron requires an intensity upgrade from 4.5x1012 to 6.5x1012 protons per pulse as a part of Fermilabs Proton Improvement Plan-II (PIP-II). One of the factors which may limit the high-intensity performance is the fast transverse instabilities caused by electron cloud effects. According to the experience in the Recycler, the electron cloud gradually builds up over multiple turns in the combined function magnets and can reach final intensities orders of magnitude greater than in a pure dipole. Since the Booster synchrotron also incorporates combined function magnets, it is essential to discover any existence of an electron cloud. And if it does, its effects on the PIP-II era Booster and its mitigating techniques. As the first step, the presence or absence of the electron cloud was investigated using the clearing bunch technique. This paper presents experimental details and observations of the bunch-by-bunch tune shifts of beams with various bunch train structures at low and high intensities and simulation results conducted using PyECLOUD.

43 PARTICLE ACCELERATORS↗
DOE OSTI2010

Muon Capture for the IDS Neutrino Factory

We have developed a new method for capture, bunching and phase-energy rotation of secondary beams from a proton source, using high-frequency rf systems. The method is the baseline for muon capture in the International scoping study for a neutrino factory. In this method, a proton bunch on a target creates secondaries that drift into a capture transport channel. A sequence of rf cavities forms the resulting muon beams into strings of bunches of differing energies, aligns the bunches to (nearly) equal central energies, and initiates ionization cooling. For the International Design Study the method must be optimized for performance and cost, and variations will be explored. In this paper we present results of optimization and variation studies toward obtaining the maximum number of muons for a neutrino factory, as well as for a future muon collider.

43 PARTICLE ACCELERATORS↗
DOE OSTI2010

Study of Optical Frequency Chirping and Pulse Compression in a High-Gain Energy-Recovery-Linac-Based Free-Electron Laser

In this paper we report a direct experimental investigation of optical frequency chirping effects induced by ultrashort electron bunches in a high-gain energy-recovery-linac (ERL) free-electron laser (FEL) cavity. Our measurement and analysis shows clear evolution of the optical pulse chirp verses the electron bunch energy chirp. Further study also provides important evidence that under certain conditions much shorter FEL pulses can be obtained through properly chirping electron bunches and optical pulse compression. Although studies about the chirp measurement on Self-amplified-spontaneous-emission (SASE) FEL were reported recently, we believe this paper for the first time provides a comprehensive and close observation into the very unique temporal and spectral characteristics of ultrashort optical pulses from a high-gain ERL FEL. This is made possible by the stable operation and unique capability of the Jefferson Lab machine to change the electron bunch energy chirp with no curvature. Preliminary simulations will also be presented.

Zhang, Shukui↗
DOE OSTI2015

Studies of a proton phase beam monitor for range verification in proton therapy

A primary subject of the present research in particle therapy is to ensure the precise irradiation of the target volume. The prompt gamma timing (PGT) method provides one possibility for in vivo range verification during the irradiation of patients. Prompt gamma rays with high energies are emitted promptly due to nuclear reactions of protons with tissue. The arrival time of these gammas to the detector reflects the stopping process of the primary protons in tissue and are directly correlated to the range. Due to the time resolution of the detector and the proton bunch time spread, as well as drifts of the bunch phase with respect to the accelerator frequency, timing spectra are smeared out and compromise the accuracy of range information intended for future clinical applications. Nevertheless, counteracting this limitation and recovering range information from the PGT measured spectra, corrections using a phase beam monitor can be performed. A first prototype of phase beam monitor was tested at GSI Darmstadt, where measurements of the energy profile of the ion bunches were performed. At the ELBE accelerator Helmholtz-Zentrum Dresden-Rossendorf (HZDR), set up to provide bremsstrahlung photons in very short pulses, a constant fraction algorithm for the incoming digital signals was evaluated, which is used for optimizing the time resolution. Studies of scattering experiments with different thin targets and detector positions are accomplished at Oncoray Dresden, where a clinical proton beam is available. These experiments allow a basic characterization of the proton bunch structure and the detection yield. (authors)

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2023

Modeling the CEBAF Injector at 200 kV: Investigating K-Long Beam Conditions with and without Wien Filter

The upcoming K-Long experiment [1] ain Hall D at Jefferson Lab presents unique beam requirements, featuring a significantly low bunch repetition rate and an unusually high bunch charge. This experiment, which utilizes the CEBAF accelerator in conjunction with the GlueX experimental setup, aims to study strange hadron spectroscopy by measuring the differential cross section and polarizations of produced hyperons such as Λ, Σ, Ξ, and Ω. By directing an intense K-Long beam towards the LD2/LH2 target, new and valuable data can be obtained. To optimize the CEBAF injector specifically for this experiment, we employed Multi-Objective Genetic Optimization (MGO) using General Particle Tracer (GPT) simulations. Through this approach, we determined the optimal magnetic elements and radiofrequency (RF) settings required to achieve a K-Long bunch charge of 0.64 pC at an energy of 200 kV. We conducted simulations with both the Wien Filter turned on and off to examine its impact on the beam. Furthermore, we investigated the transmission efficiency and beam characteristics of electron beams with varying charge per bunch through the injector, considering the simultaneous operation of all four CEBAF Halls. The results of our study offer valuable insights and guidance for optimizing the CEBAF injector not only for the Jefferson Lab K-Long experiment but also for other experiments that entail similar beam conditions.

Pokharel, Sunil↗
DOE OSTI2025

IOTA Experiment for Proton Pulse Compression at Extreme Space-Charge

The longitudinal compression of high-intensity, space-charge-dominated proton bunches is a critical requirement for future proton-driven muon colliders. We propose a proton bunch compression experiment at the Integrable Optics Test Accelerator (IOTA) storage ring at Fermilab to investigate optimal radio-frequency (RF) cavity parameters and lattice configurations. IOTA is a compact, fixed-energy storage ring dedicated to beam physics Research and Development and capable of circulating a 2.5 MeV proton beam under extreme space-charge conditions. Using the ImpactX code with its 3D space-charge solver, simulations indicate that the bunch length can be rapidly reduced by at least a factor of two without appreciable degradation of transverse beam quality--even in the strong space-charge regime. However, longitudinal defocusing due to the space-charge remains a significant challenge in short-pulsed intense proton bunches, and the optimization of compression under these conditions is discussed.

Simons, B. D. [Northern Illinois U.]↗
DOE OSTI2010

Femtosecond Operation of the LCLS for User Experiments

In addition to its normal operation at 250pC, the LCLS has operated with 20pC bunches delivering X-ray beams to users with energies between 800eV and 2 keV and with bunch lengths below 10 fs FWHM. A bunch arrival time monitor and timing transmission system provide users with sub 50 fs synchronization between a laser and the X-rays for pump/probe experiments. We describe the performance and operational experience of the LCLS for short bunch experiments.

Accelerators,ACCPHY, ACCSYS, INST, XFEL↗
DOE OSTI2010

IMPEDANCE CONSIDERATIONS FOR THE DESIGN OF THE VACUUM SYSTEM OF THE CERN PS2

In order for the LHC to reach an ultimate luminosity goal of 10{sup 35}/cm{sup 2}/s, CERN is considering upgrade options for the LHC injector chain, including a new 50 GeV synchrotron of about 1.3 km length for protons and heavy ions, to be called the PS2 [1]. The proton energy will be ramped from 4 GeV to 50 GeV in 1.2 s, and the design proton current for LHC operation is 2.7 A. In the LARP framework, we are studying the instability thresholds and the impedance requirements of the vacuum system for the PS2. Goal of this study is to develop an impedance budget for the machine. We consider the standard single and multi-bunch collective effects that may be an issue in the PS2. For single bunch, we study the microwave instability and the transverse mode coupling instability (TMCI); for multi-bunch, the transverse coupled bunch instability. While the impedance budget will include many components in the machine, at present, we only have sufficient information to include the resistance of the beam pipe, the vacuum flanges that connect the various pieces of the vacuum chamber, and space charge impedance in our estimate. Note that earlier estimates of the impedance and its effects in the PS2 can be found in Ref. [2]. Table 1 presents selected PS2 parameters that will be used in the calculations. The equations used, unless indicated otherwise, can be found in Ref. [3].

43 PARTICLE ACCELERATORS↗
DOE OSTI2012

A New Green's Function for the Wake Potential Calculation of the SLAC S-band Constant Gradient Accelerating Section

The behavior of the longitudinal wake fields excited by a very short bunch in the SLAC S-band constant gradient accelerating structures has been studied. Wake potential calculations were performed for a bunch length of 10 microns using the author's code to obtain a numerical solution of Maxwell's equations in the time domain. We have calculated six accelerating sections in the series (60-ft) to find the stationary solution. While analyzing the computational results we have found a new formula for the Green's function. Wake potentials, which are calculated using this Green's function are in amazingly good agreement with numerical results over a wide range of bunch lengths. The Green's function simplifies the wake potential calculations and can be easily incorporated into the tracking codes. This is very useful for beam dynamics studies of the linear accelerators of LCLS and FACET.

43 PARTICLE ACCELERATORS↗
DOE OSTI2010

Hybrid Laser-Plasma Wakefield Acceleration

The concept of driving a driver/witness-type plasma wakefield accelerator (PWFA) with quasimonoenergetic double electron bunches from a laser wakefield accelerator (LWFA) is studied. In the quasimonoenergetic LWFA/SMLWFA (self-modulated LWFA) regime, it is possible to generate multiple quasimonoenergetic electron bunches with durations of only a few fs and distances of only a few tens of fs with a comparably simple experimental setup. In a subsequent high-density plasma afterburner stage the witness bunch energy can be boosted in the plasma wakefield generated by the driver. Such a hybrid system can increase the maximum energy output of a laser wakefield accelerator and is well suited to study driver/witness plasma accelerator phenomena and can be used as a cost-effective test-bed for future high-energy plasma-based accelerators.

43 PARTICLE ACCELERATORS↗
DOE OSTI2011

Photoelectron-photofragment coincidence spectroscopy in a cryogenically cooled linear electrostatic ion beam trap

A cryogenically cooled linear electrostatic ion beam trap for use in photoelectron-photofragment coincidence (PPC) spectroscopy is described. Using this instrument, anions created in cold, low-duty-cycle sources can be stored for many seconds in a {approx}20 K environment to cool radiatively, removing energetic uncertainties due to vibrationally excited precursor anions. This apparatus maintains a well-collimated beam necessary for high-resolution fragment imaging and the high experimental duty cycle needed for coincidence experiments. Ion oscillation is bunched and phase-locked to a modelocked laser, ensuring temporal overlap between ion bunches and laser pulses and that ions are intersected by the laser only when travelling in one direction. An electron detector is housed in the field-free center of the trap, allowing PPC experiments to be carried out on ions while they are stored and permitting efficient detection of 3-dimensional electron and neutral recoil trajectories. The effects of trapping parameters on the center-of-mass trajectories in the laser-ion interaction region are explored to optimize neutral particle resolution, and the impact of bunching on ion oscillation is established. Finally, an initial demonstration of radiative cooling is presented.

43 PARTICLE ACCELERATORS↗
DOE OSTI2012

High transformer ratio drive beams for wakefield accelerator studies

For wakefield based acceleration schemes, use of an asymmetric (or linearly ramped) drive bunch current profile has been predicted to enhance the transformer ratio and generate large accelerating wakes. We discuss plans and initial results for producing such bunches using the 20 to 23 GeV electron beam at the FACET facility at SLAC National Accelerator Laboratory and sending them through plasmas and dielectric tubes to generate transformer ratios greater than 2 (the limit for symmetric bunches). The scheme proposed utilizes the final FACET chicane compressor and transverse collimation to shape the longitudinal phase space of the beam.

43 PARTICLE ACCELERATORS↗
DOE OSTI2012

Three regimes of relativistic beam - plasma interaction

Three regimes of relativistic beam - plasma interaction can in principle be reached at the ATF depending on the relative transverse and longitudinal size of the electron bunch when compared to the cold plasma collisionless skin depth c?{omega}{sub pe}: the plasma wakefield accelerator (PWFA), the self-modulation instability (SMI), and the current filamentation instability (CFI) regime. In addition, by choosing the bunch density, the linear, quasi-nonlinear and non linear regime of the PWFA can be reached. In the case of the two instabilities, the bunch density determines the growth rate and therefore the occurrence or not of the instability. We briefly describe these three regimes and outline results demonstrating that all these regime have or will be reached experimentally. We also outline planned and possible follow-on experiments.

43 PARTICLE ACCELERATORS↗
DOE OSTI2012

Charge recombination in the muon collider cooling channel

The final stage of the ionization cooling channel for the muon collider must transversely recombine the positively and negatively charged bunches into a single beam before the muons can be accelerated. It is particularly important to minimize any emittance growth in this system since no further cooling takes place before the bunches are collided. We have found that emittance growth could be minimized by using symmetric pairs of bent solenoids and careful matching. We show that a practical design can be found that has transmission {approx}99%, emittance growth less than 0.1%, and minimal dispersion in the recombined bunches.

43 PARTICLE ACCELERATORS↗
DOE OSTI2013

FLUTE: A versatile linac-based THz source

A new compact versatile linear accelerator named FLUTE is currently being designed at the Karlsruhe Institute of Technology. This paper presents the status of this 42 MeV machine. It will be used to generate strong (several 100 MV/m) ultra-short ({approx}1 ps) THz pulses (up to {approx}4-25 THz) for photon science experiments, as well as to conduct a variety of accelerator studies. The latter range from comparing different coherent THz radiation generation schemes to compressing electron bunches and studying the electron beam stability. The bunch charge will cover a wide range ({approx}100 pC-3 nC). Later we plan to also produce ultra-short x-ray pulses from the electron bunches, which, for example, could then be combined for THz pump-x-ray probe experiments.

43 PARTICLE ACCELERATORS↗
DOE OSTI2013

Development of diagnostic and manipulation systems for space-charge dominated electron beams and confined electron plasmas in ELTRAP

Modifications have been implemented in the Penning-Malmberg device ELTRAP aimed at performing studies on the dynamics of space-charge dominated nanosecond electron bunches traveling along the magnetic field. In particular, a Thomson backscattering apparatus has been developed where an infrared (IR) laser pulse collides with the bunched electron beam. The frequency-shifted backscattered radiation, acquired by means of a photomultiplier (PMT), can be exploited to evaluate information on energy, energy spread and density of the bunch. The achievable sensitivity of the diagnostics has been estimated, and valuable information on the main parameters affecting the signal-to-noise (S/N) ratio has been obtained [B. Paroli, F. Cavaliere, M. Cavenago, F. De Luca, M. Ikram, G. Maero, C. Marini, R. Pozzoli, and M. Rome, JINST 7, P01008 (2012)]. A series of upgrades are under way, aimed at increasing the S/N ratio through the use of a new laser for the electron source, the insertion of a stray light shield, and the optimization of the detection electronics. Moreover, electromagnetic simulations relevant to the design and implementation of a microwave heating system are presented. The generation of an electron plasma in ELTRAP by means of a low-power radio frequency (RF) drive in the MHz range applied on one of the trap electrodes and under ultra-high vacuum (UHV) conditions has previously been demonstrated [B. Paroli, F. De Luca, G. Maero, F. Pozzoli, and M. Rome, Plasma Sources Sci. Technol. 19, 045013 (2010)]. The new heating system will allow the extension of the RF studies to the GHz range and in particular the production of a more energetic electron plasma via cyclotron resonant excitation.

43 PARTICLE ACCELERATORS↗
DOE OSTI2012

A Compact Ring Design with Tunable Momentum Compaction

A storage ring with tunable momentum compaction has the advantage in achieving different RMS bunch length with similar RF capacity, which is potentially useful for many applications, such as linear collider damping ring and predamping ring where injected beam has a large energy spread and a large transverse emittance. A tunable bunch length also makes the commissioning and fine tuning easier in manipulating the single bunch instabilities. In this paper, a compact ring design based on a supercell is presented, which achieves a tunable momentum compaction while maintaining a large dynamic aperture.

43 PARTICLE ACCELERATORS↗