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First Measurements of the Longitudinal Bunch Profile at SLAC Using Coherent Smith-Purcell Radiation at 28GeV
Coherent Smith-Purcell radiation has been demonstrated as a technique for measuring the longitudinal profile of charged particles bunches in the low to intermediate energy range. However, with the advent of the International Linear Collider, the need has arisen for a non-invasive method of measuring the bunch profile at extremely high energies. Smith-Purcell radiation has been used for the first time in the multi-GeV regime to measure the longitudinal profile of the 28GeV SLAC beam. The experiment has both successfully determined the bunch length, and has also demonstrated its sensitivity to bunch profile changes. The challenges associated with this technique, and its prospects as a diagnostic tool are reported here.
Reconstructions from randomly generated longitudinal electron bunch profiles with Gaussian envelopes using the Gerchberg–Saxton algorithm
Knowledge of longitudinal electron bunch profiles is vital to optimize the performance of plasma wakefield accelerators and x-ray free electron laser linacs. Because of their importance to these novel applications, noninvasive frequency domain techniques are often employed to reconstruct longitudinal bunch profiles from coherent synchrotron, transition, or undulator radiation measurements. In this paper, we detail several common reconstruction techniques involving the Kramers–Kronig phase relationship and Gerchberg–Saxton algorithm. Additionally, through statistical analysis, we draw general conclusions about the accuracy of these reconstruction techniques and the most suitable candidate for reconstructing well-isolated longitudinal bunch profiles from spectroscopic data.
Modelling and measurements of bunch profiles at the LHC
The bunch profiles in the LHC are often observed to be non-Gaussian, both at Flat Bottom (FB) and Flat Top (FT) energies. Especially at FT, an evolution of the tail population in time is observed. In this respect, the Monte-Carlo Software for IBS and Radiation effects (SIRE) is used to track different types of beam distributions. The impact of the distribution shape on the evolution of bunch characteristics is studied. The results are compared with observations from the LHC Run 2 data.
Bunch Profiling Using a Rotating Mask
The current method for measuring profiles of proton bunches in accelerators is severely lacking. One must dedicate a great deal of time and expensive equipment to achieve meaningful results. A new method to complete this task uses a rotating mask with slots of three different orientations to collect this data. By scanning over the beam in three different directions, a complete profile for each bunch is built in just seconds, compared to the hours necessary for the previous method. This design was successfully tested using synchrotron radiation emitted by SPEAR3. The profile of the beam was measured in each of the three desired directions. Due to scheduled beam maintenance, only one set of data was completed and more are necessary to solve any remaining issues. The data collected was processed and all of the RMS sizes along the major and minor axes, as well as the tilt of the beam ellipse were measured.
Electron Bunch Profile Diagnostics in the Few FS Regime Using Coherent Smith-Purcell Radiation
The rapid developments in the field of laser-driven particle acceleration hold the prospect of intense, highly relativistic electron bunches that are only a few fs long. The determination of the temporal profile of such bunches presents new challenges. The use of a radiative process such as Smith-Purcell radiation (SPR), is particularly promising in this respect. In this technique the beam is made to radiate a small amount of e/m radiation and the temporal profile is reconstructed from the measured spectral distribution of the radiation. We summarise the advantages of SPR and present the design parameters and preliminary results of the experiments at the FACET facility at SLAC. We also discuss a new approach to the problem of the recovery of the 'missing phase', which is essential for the accurate reconstruction of the temporal bunch profile.
Electron Bunch Profile Reconstruction in the Few fs Regime using Coherent Smith-Purcell Radiation
Advanced accelerators for fourth generation light sources based on high brightness linacs or laser-driven wakefield accelerators will operate with intense, highly relativistic electron bunches that are only a few fs long. Diagnostic techniques for the determination of temporal profile of such bunches are required to be non invasive, single shot, economic and with the required resolution in the fs regime. The use of a radiative process such as coherent Smith-Purcell radiation (SPR), is particularly promising with this respect. In this technique the beam is made to radiate a small amount of electromagnetic radiation and the temporal profile is reconstructed from the measured spectral distribution of the radiation. We summarise the advantages of SPR and present the design parameters and preliminary results of the experiments at the FACET facility at SLAC. We also discuss a new approach to the problem of the recovery of the 'missing phase', which is essential for the accurate reconstruction of the temporal bunch profile.
Analysis of a Single Shot Longitudinal Bunch Profiling System Based on An Ultra Short Pulse Ti:Sapphire Laser
No abstract prepared.
Spectral Fluctuations of Incoherent Radiation And Measurement of Longitudinal Bunch Profile
A method for measurement of ultrashort beam current profile I{sub b}(t) is proposed that is based on detecting fluctuations of the spectral intensity P ({omega}) of single bunch incoherent radiation. We show that the variance of the Fourier transform of the spectrum is proportional to the convolution function of the beam current. After the convolution function is found, using phase retrieval technique one can restore the shape of the pulse in many practical cases.
Electron bunch profile reconstruction based on phase-constrained iterative algorithm
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Evolution of ion bunch profile in the presence of longitudinal coherent electron cooling
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Longitudinal bunch profile diagnostic for magnetized electron beams
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Longitudinal bunch profile measurement of operational H − beam using laser wire and virtual slit
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MEASUREMENT OF LONGITUDINAL BUNCH PROFILE AND TWISS PARAMETERS IN SNS LINAC
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E-Cloud Dependence on the Longitudinal Bunch Profile in the PS and the HL-LHC
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Dependence of E-Cloud on the Longitudinal Bunch Profile: Studies in the PS & Extension to the HL-LHC
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Theories derived from Haissinski equation and their applications to electron storage rings
As a stationary solution of the Vlasov–Fokker–Planck equation, the Haissinski equation predicts the equilibrium line density of a bunch that circulates in a storage ring for a given wake function. The research in this paper shows that some equations regarding the centroid shift of the bunch, the peak position of the bunch profile, bunch length, and the impedance from the bunch profile can be derived from the Haissinski equation in a self-consistent manner. Specifically, a generalized quadratic equation for potential-well bunch lengthening is derived to accommodate any arbitrary impedance model (that is, the impedance spectrum under consideration can take any form). This expands upon Zotter's cubic equation, which is primarily applicable to inductive impedance. The equations derived in this paper are tested using computed impedance models for some electron storage rings, showing machine-dependent properties of impedance effects. We conclude that these equations can be employed in electron storage rings to effectively bridge the gap between impedance computations and beam-based measurements.
A Quest for Measuring Ion Bunch Longitudinal Profiles with One Picosecond Accuracy in the SNS Linac.
The SNS linac utilizes several accelerating structures operating at different frequencies and with different transverse focusing structures. Low-loss beam transport requires a careful matching at the transition points in both the transverse and longitudinal axes. Longitudinal beam parameters are measured using four Bunch Shape Monitors (used at many ion accelerator facilities, aka Feschenko devices). These devices, as initially delivered to the SNS, provided an estimated accuracy of about 5 picoseconds, which was sufficient for the initial beam commissioning. New challenges of improving beam transport for higher power operation will require measuring bunch profiles with 1-2 picoseconds accuracy. We have successfully implemented a number of improvements to maximize the performance characteristics of the delivered devices. We will discuss the current status of this instrument, its ultimate theoretical limit of accuracy, and how we measure its accuracy and resolution with real beam conditions.