Bunched-beam Schottky monitoring in the LHC

Betz, M.; Jones, O R; Lefèvre, T.; Wendt, M.

doi:10.1016/j.nima.2017.08.045

Cited by 5 publications

(6 citation statements)

References 18 publications

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“…It is high enough resolution to observe the inner structure of Bessel satellites, which is crucial for our further considerations. Extensive details on the acquisition architecture can be found in [2]. For all longitudinal studies' results presented in this paper, we limited ourselves to 2854 rows (jω − nω 0 j ∈ ½20; 1000 Hz).…”

Section: Bunch Shape Calculationsmentioning

confidence: 99%

“…It is determined by two parameters, standard deviation σ N 2D and the modulus of mean ν N 2D of the mentioned 2D-normal distribution. 2 While a correlation between the Rice distribution and the distribution of synchrotron amplitudes is plausible at the moment of injection (the synchrotron amplitude is proportional to the distance from the origin in the longitudinal phase space), the question arises why it would remain valid after rf manipulations such as the ones performed during the energy ramp. Not knowing the answer to this question, we base our assumption on observations of bunch shapes measured by the WCM at different beam phases, and their corresponding synchrotron amplitude densities [calculated from Eq.…”

Section: Bunch Shape Calculationsmentioning

confidence: 99%

“…The Large Hadron Collider (LHC) transverse Schottky system, whose main objective is to provide the beam operators with noninvasive bunch-by-bunch tune and chromaticity measurements, was commissioned in 2011 [1]. In the meantime, the system has undergone major upgrades in order to improve signal quality [2]. Although qualitatively its chromaticity estimates agree with other measurement techniques (as verified in dedicated experiments), the small residual quantitative discrepancies observed need to be understood [3].…”

Section: Introductionmentioning

confidence: 99%

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Estimation of longitudinal bunch characteristics in the LHC using Schottky-based diagnostics

Lasocha

Alves

2020

Phys. Rev. Accel. Beams

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The Large Hadron Collider (LHC) Schottky monitors have been designed to measure various parameters of relevance to beam quality, namely tune, momentum spread, and chromaticity. In this work, we present how this instrument can be used to estimate longitudinal bunch characteristics, such as longitudinal bunch profile or synchrotron frequency distribution. Under the assumption of bunched beams with no intrabunch coherent motion, we start by deriving the relation between the distribution of synchrotron amplitudes within the bunch population and the longitudinal bunch profile from probabilistic principles. Subsequently, we fit the cumulative power density of acquired Schottky spectra with the underlying distribution of synchrotron amplitudes. Finally, the result of this fit is used to reconstruct the bunch profile using the derived model. The results obtained with this method are verified by comparison with longitudinal profile measurements from the LHC wall current monitors.

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Section: Bunch Shape Calculationsmentioning

confidence: 99%

Section: Bunch Shape Calculationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Estimation of longitudinal bunch characteristics in the LHC using Schottky-based diagnostics

Lasocha

Alves

2020

Phys. Rev. Accel. Beams

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“…The first method is based on the Monte Carlo approach presented in ref. [11]. It consists of drawing randomly, for each particle, a synchrotron oscillation time-amplitude 𝜏 𝑖 and an initial synchrotron phase 𝜑 𝑠 𝑖 from respectively a Rice and a uniform distribution.…”

Section: Theoretical Benchmarkingmentioning

confidence: 99%

“…As the Fourier transform is a linear operation, the bunch spectrum can be derived by summing the complex values of single-particle spectra using a sliding window, as done in ref. [11]. Taking the squared modulus of this sum gives the Power Spectral Density (PSD) of the whole bunch (i.e.…”

Section: Theoretical Benchmarkingmentioning

confidence: 99%

Impact of beam-coupling impedance on the Schottky spectrum of bunched beam

Lannoy,

Lasocha,

Pieloni

et al. 2024

J. Inst.

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The Schottky monitors of the Large Hadron Collider (LHC) can be used for non-invasive beam diagnostics to estimate various bunch characteristics, such as tune, chromaticity, bunch profile or synchrotron frequency distribution. However, collective effects, in particular beam-coupling impedance, can significantly affect Schottky spectra when large bunch charges are involved. In such conditions, the available interpretation methods are difficult to apply directly to the measured spectra, thus preventing the extraction of beam and machine parameters, which is possible for lower bunch charges. To study the impact of impedance on such spectra, we introduce a method for building Schottky spectra from macro-particle simulations performed with the PyHEADTAIL code, applied to LHC beam conditions. In this case, the use of a standard Fast Fourier Transform (FFT) algorithm to recover the spectral content of the beam becomes computationally intractable memory-wise, because of the relatively short bunch length compared to the large revolution period. To circumvent this difficulty, a semi-analytical method was developed to efficiently compute the Fourier transform. The simulated Schottky spectrum is then compared against theoretical formulas and measurements of Schottky signals previously obtained with lead ion beams in the LHC where impedance effects are expected to be limited. Furthermore, this study provides preliminary interpretations of the impact of beam-coupling impedance on proton Schottky spectra by incorporating longitudinal and transverse resonator-like impedance models into the simulations. A theoretical framework is also introduced for the case of the longitudinal impedance, allowing the extension of the existing theoretical formalism.

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Non-destructive position measurement of coasting beam using Schottky signals

Singh

Forck

Kowina

et al. 2018

Review of Scientific Instruments

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The beam position appears in the transverse Schottky signal spectra of coasting beams at revolution frequency and its harmonics. In this contribution, we utilize this signal for beam position monitoring using regular shoe-box monitors at heavy ion synchrotron GSI SIS-18. Position resolution below 1 mm at 1 kHz rate for 10 mA current was obtained. These results demonstrate the feasibility of non-destructive position monitoring of unbunched beams in synchrotrons and storage rings using capacitive pick-up data with appropriate signal processing.

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Bunched-beam Schottky monitoring in the LHC

Cited by 5 publications

References 18 publications

Estimation of longitudinal bunch characteristics in the LHC using Schottky-based diagnostics

Estimation of longitudinal bunch characteristics in the LHC using Schottky-based diagnostics

Impact of beam-coupling impedance on the Schottky spectrum of bunched beam

Non-destructive position measurement of coasting beam using Schottky signals

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