Fixed Point SU(3) Gauge Actions: Scaling Properties and Glueballs

We present a new parametrization of a SU(3) fixed point (FP) gauge action using smeared ("fat") gauge links. We report on the scaling behaviour of the FP action on coarse lattices by means of the static quark-antiquark potential, the hadronic scale $r_0$, the string tension $\sigma$ and the critical temperature $T_c$ of the deconfining phase transition. In addition, we investigate the low lying glueball masses where we observe no scaling violations within the statistical errors.Comment: Lattice 2000 (Improvement and Renormalisation), 4 pages, 3 eps-figures, LaTe

Classically Perfect Gauge Actions on Anisotropic Lattices

We present a method for constructing classically perfect anisotropic actions for SU(3) gauge theory based on an isotropic Fixed Point Action. The action is parametrised using smeared (``fat'') links. The construction is done explicitly for anisotropy $\xi=a_s/a_t=2$ and 4. The corresponding renormalised anisotropies are determined using the torelon dispersion relation. The renormalisation of the anisotropy is small and the parametrisation describes the true action well. Quantities such as the static quark-antiquark potential, the critical temperature of the deconfining phase transition and the low-lying glueball spectrum are measured on lattices with anisotropy $\xi=2$. The mass of the scalar $0^{++}$ glueball is determined to be 1580(60) MeV, while the tensor $2^{++}$ glueball is at 2430(60) MeV.Comment: 64 pages, 19 figures, LaTe

Fixed Point Gauge Actions with Fat Links: Scaling and Glueballs

A new parametrization is introduced for the fixed point (FP) action in SU(3) gauge theory using fat links. We investigate its scaling properties by means of the static quark-antiquark potential and the dimensionless quantities $r_0 T_c, T_c/\sqrt{\sigma}$ and $r_0 \sqrt{\sigma}$, where $T_c$ is the critical temperature of the deconfining phase transition, $r_0$ is the hadronic scale and $\sigma$ is the effective string tension. These quantities scale even on lattices as coarse as $a \approx 0.3$ fm. We also measure the glueball spectrum and obtain $m_{0^{++}}=1627(83)$ MeV and $m_{2^{++}}=2354(95)$ MeV for the masses of the scalar and tensor glueballs, respectively.Comment: 45 pages, 12 figures, Late

Development of a Fast Betatron Tune and Chromaticity Measurement System Using Bunch-by-Bunch Position Monitoring

The betatron tune and its dependence on the momentum (chromaticity) are essentialquantities of circular particle accelerators. The tune must be monitored in order toavoid optical resonances which cause instabilities and limit the lifetime of the storedparticle beam. Control of the tune and chromaticity are also required to achieve longcoherence times in spin polarization experiments as carried out by the JEDI collaboration.In the scope of the present thesis, a fast betatron tune and chromaticity measurementsystem is developed for the Cooler Synchrotron COSY. The betatron oscillations ofthe beam are excited through stripline electrodes with a white noise RF signal in anappropriate frequency band. Resonant transverse oscillations are then observed usingcapacitive beam position monitors. Characteristic for the newly developed system isthe determination of the betatron tune from bunch-by-bunch beam position measurements.This allows for time-discrete tune measurements within a few milliseconds aswell as continuous tune monitoring – for example during the acceleration ramp.The high precision tune measurement also enables determination of the beam chromaticity.Therefore, the beam momentum is varied by means of RF frequency sweepsand the subsequent tune change is measured. For routine use during beam operationand experiments, the developed method is integrated into the control system.Finally, measurements showing the operational capabilities and limits of the methodare presented. The influence of different parameters on the signal strength is analysed.For commissioning, control of the betatron tune and compensation of the chromaticityare demonstrated

Integration of the COSY 2MeV Electron Cooler into EPICS

We report on the control system upgrade of the 2MeV electron cooler at the Cooler Synchrotron (COSY).An EPICS IOC was implemented to integrate the cooler to the COSY control system, providing 1059 readout parameters of the cooler as EPICS PVs.Thereby archiving of the electron coolers parameter was achieved, which is crucial for data analysis and correlation. Also, the proton orbit influencing magnets of the electron cooler were made available to the COSY control system as well as the proton beam positions measured by the electron coolers BPM.Also new GUIs were developed to display the coolers current status and control the magnet power supplies

Charakterisierung der Kühldynamik des 2MeV Elektronenkühlers am Beschleuniger COSY

Das Cooler Synchrotron COSY des Forschungszentrum Jülich verfügt über zwei Verfahren der Strahlkühlung, stochastische- und Elektronenkühlung.Damit kann die Impulsunschärfe sowie die Emittanz des Teilchenstrahls verringert und klein gehalten werden, um so die Anforderungen kernphysikalischer Experimente zu erfüllen.Ziel dieser Arbeit ist die systematische Untersuchung der Dynamik der Hochenergie Elektronenkühlung, um die erreichbare Strahlqualität sowie die Kühlrate zu verbessern.Um die dazu erforderlichen Messungen zu ermöglichen, wird die Datenerfassung des Kühlers und der strahldiagnostischen Systeme automatisiert und die Datenspeicherung zentral zusammengeführt.Auf Basis des Kontrollsystems EPICS wird außerdem eine Online-Datenauswertung implementiert.Im Ergebnis werden Analyse- und Korrelation von beliebigen Datensätzen wesentlich vereinfacht und nachträgliche Analysen ermöglicht.Die damit durchgeführten Messungen zeigen durchweg eine schnelle longitudinale und wesentlich langsamere transversale Elektronenkühlung.Eine Studie der Elektronenbewegung während des Kühlprozesses legt nahe, dass nicht nur die Elektronenschwingungen, sondern auch die Größe des Protonenstrahls von entscheidender Bedeutung ist.Im Bezug auf Kühlstärke und -geschwindigkeit können die besten Ergebnisse – insbesondere im Target-Betrieb – durch Kombination der Vorteile beider Kühlverfahren erzielt werden.Mithilfe eines durch stochastische Vor-Kühlung verkleinerten Strahlquerschnitts kann die Kühlgeschwindigkeit verdoppelt, und gleichzeitig eine große Impulsschärfe erreicht werden, weshalb dieses Vorgehen zu empfehlen ist.Bei gleichzeitigem Betrieb der Systeme tritt ein bislang nicht vollständig verstandenes Artefakt im Schottky Signal auf, dass weiterer Untersuchung bedarf

Excitation signal optimization for minimizing fluctuations in knock out slow extraction

The synchrotron is a circular particle accelerator used for high energy physics experiments, material and life science, as well as hadron cancer therapy. After acceleration to the desired energies, particle beams are commonly extracted from the synchrotron using the method of resonant slow extraction. The goal is to deliver a steady particle flux—referred to as spill—to experiments and treatment facilities over the course of seconds while slowly emptying the storage ring. Any uncontrolled intensity fluctuations in the spill are detrimental to the efficiency of beam usage, as they lead to detector pileups or detector interlocks, hindering experiments and cancer treatment. Among the most widely used extraction scheme in medical facilities is the Radio Frequency Knock Out (RF-KO) driven resonant slow extraction, where the stored beam is transversely excited with a radio frequency (RF) field and the spill intensity is controlled by the excitation signal strength. This article presents particle dynamics simulations of the RF-KO system with the focus on finding effective mechanism for minimizing the intensity fluctuations while maintaining a good extraction efficiency and other advantages of KO extraction. An improved beam excitation signal which optimizes these main objectives is found, and is rigorously compared experimentally with other commonly applied techniques

Transverse Excitation and Applications for Beam Control

Transverse excitation of stored particle beams is required for a number of applications in accelerators. Using a time-varying, transverse electric field with a dedicated frequency spectrum, the amplitude and coherence of betatron oscillations can be increased in a controlled manner. This allows for determination of the betatron tune from turn-by-turn position measurements, control of transverse beam shapes, as well as extraction of stored beams. For studies of beam excitation, a custom signal generator is being developed. It is based on software-defined radio (SDR) which allows for configurable signal characteristics and tuneable spectra. This approach enables usage for multiple applications in beam diagnostics and control. To determine appropriate excitation spectra, studies of particle dynamics in presence of excitation are being carried out. Nonlinear fields are also incorporated to account for beam extraction conditions, which affects frequency spectra of beam motion due to detuning effects

Tune and chromaticity measurement at COSY

An overview on the established tune sweep system and the newly developed fast tune and chromaticity measurement system is given. The methods and their capabilities are described and the two systems are compared