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Volker Ziemann

Publications and source records attributed to Volker Ziemann.

At least 19 recordsLinked to original sources
arXiv2026

Controlling a digital twin of the CEBAF injector from EPICS

The Experimental and Instrumental Control System EPICS is used to control magnets and to read data from diagnostic devices in the CEBAF accelerator. We describe a prototype system where an EPICS installation, local on a laptop or Raspberry Pi, controls beam optics simulations. They can be running on the same computer or on a separate computer connected via the network. The prototype focuses on modeling and controlling the moderately complex injector beam line of CEBAF, which only comprises a few dozen magnets and beam monitors.

physics.acc-ph↗
arXiv2026

The transient behavior of superconducting multi-cell accelerating cavities

We employ an equivalent-circuit model of a multi-cell cavity to explore its time-dependent behavior in order to understand differences between the multi-cell model and the commonly-used model of a single-cell resonator. Furthermore, we address tolerances that arise from manufacturing imperfections.

physics.acc-ph↗
arXiv2024

German Beams -- The Story of Particle Accelerators in Germany

Even though many of the experiments leading to the standard model of particle physics were done at large accelerator laboratories in the US and at CERN, many exciting developments happened in smaller national facilities all over the world. In this report we highlight the history of accelerator facilities in Germany.

physics.acc-ph↗
arXiv2024

Swedish Beams -- The Story of Particle Accelerators in Sweden

Even though many of the experiments leading to the standard model of particle physics were done at large accelerator laboratories in the US and at CERN[1] many exciting developments happened in smaller national facilities all over the world. In this report we highlight the history of accelerator facilities in Sweden which was home to the highest-energy cyclotron in Europe for some time in the early 1950s. [1] For a brief history of this story see: V. Ziemann, Beams -- the Story of Particle Accelerators and the Science they Discover, Copernicus books, Springer 2024.

physics.acc-ph↗
arXiv2024

A new method to measure the unloaded quality factor of superconducting cavities

We describe an method that measures the unloaded quality factor $Q_0$, the external quality factor $Q_E$, and the cavity detuning $Δω$ with a recursive least-squares algorithm. It combines a large number of consecutive measurements to successively improve an estimate of fit parameters that asymptotically converges to the ``real'' values. Exploiting the large amount of data acquired by a digital low-level RF system permits us to reach this asymptotic regime in a moderate time frame of seconds to minutes. Simulations show that the method works both for critically coupled and over-coupled cavities. A new calibration method adresses very tight tolerances of the method on system parameters.

physics.acc-ph↗
arXiv2023

Simulations of real-time system identification for superconducting cavities with a recursive least-squares algorithm

We explore the performance of a recursive least-squares algorithm to determine the bandwidth $ω_{12}$ and the detuning $Δω$ of a superconducting cavity. We base the simulations on parameters of the ESS double-spoke cavities. Expressions for the signal-to-noise ratio of derived parameters are given to explore the applicability of the algorithm to other configurations.

physics.acc-ph↗
arXiv2022

Closed-form expressions for the magnetic field of permanent magnets in three dimensions

We derive a closed-form expression of the magnetic field of a finite-size current sheet and use it to calculate the field of permanent magnets, which are modeled through their surface current densities. We illustrate the method by determining the multipoles and the effective length due to fringe fields of a finite-length dipole constructed of magnetic cubes.

physics.app-ph↗
arXiv2022

RF gymnastics with transfer matrices

We introduce transfer matrices to describe the motion of particles in the vicinity of the stable and unstable fixed points of longitudinal phase space and use them to analyze the transfer of bunches between radio-frequency systems operating at different harmonics and voltages. We then apply this formalism to analyze the decoherence due to amplitude-dependent tune shift on the asymptotically achievable longitudinal emittance and assess tolerances for the injection.

physics.acc-ph↗
arXiv2022

Equilibrium parameters in coupled storage ring lattices and practical applications

We calculate equilibrium emittances and damping times due to the emission of synchrotron radiation for coupled storage ring lattices by evaluating the projections of the commonly used synchrotron radiation integrals onto the normal modes of the coupled motion. Orbit distortion is included by calculating off-axis contributions to the radiation integrals. We provide explicit formulae for fast forward calculation, which have been implemented into the interactive lattice design code OPA.

physics.acc-ph↗
arXiv2022

Beam parameters of a Möbius ring

We describe a racetrack-shaped ring in which the cross-plane coupling can be continuously varied between an uncoupled configuration to a Möbius configuration, where the transverse planes change role after one turn. Tunes, emittances, and other beam parameters that depend on the emission of synchrotron radiation are calculated as a function of the coupling.

physics.acc-ph↗
arXiv2021

Longitudinal phase-space matching between radio-frequency systems with different harmonic numbers and accelerating voltages

We describe a simple mechanism to transform bunches with matched longitudinal phase-space distributions from one RF system to a matched distribution of a second RF system operating on a different harmonic and with a different accelerating voltage. The process is reversible and the longitudinal emittance is preserved. Simple equations that characterize the procedure are given and applications are discussed. In particular this method can be used to rapidly shorten the bunch length in proton rings.

physics.acc-ph↗
arXiv2021

Noninvasively improving the orbit-response matrix while continuously correcting the orbit

Based on continuously recorded beam positions and corrector excitations from, for example, a closed-orbit feedback system we describe an algorithm that continuously updates an estimate of the orbit response matrix. The speed of convergence can be increased by adding very small perturbations, so-called dither, to the corrector excitations. Estimates for the rate of convergence and the asymptotically achievable accuracies are provided.

physics.acc-ph↗
arXiv2021

Strap-on magnets: a framework for rapid prototyping of magnets and beam lines

We describe a framework to assemble permanent-magnet cubes in 3D-printed frames to construct dipole, quadrupole, and solenoid magnets, whose field, in the absence of iron, can be calculated analytically in three spatial dimensions. Rotating closely spaced dipoles and quadrupoles in opposite directions allows us to adjust the integrated strength of a multipole. Contributions of unwanted harmonics are calculated and found to be moderate. We then combine multiple magnets to construct beam-line modules: chicane, triplet cell, and solenoid focusing system.

physics.acc-ph↗