IBIC2016 - List of Authors (Rehm, G.)

Paper	Title	Page
TUCL03	Measurements of Longitudinal Coupled Bunch Instabilities and Status of New Feedback System	298
	G. Rehm, M.G. Abbott, A.F.D. Morgan DLS, Oxfordshire, United Kingdom
	We have modified the vertical bunch-by-bunch feedback to also provide a longitudinal kick on a separate input. Using our existing drive/damp system and a modulator/amplifier to the required 1.5 GHz we are thus able to characterise the damping rates of all coupled bunch instabilities, while not able to provide feedback. At the same time, we have started the development of a completely new longitudinal feedback system based on commercially available components, providing 500MS/s, 14 bit conversion in and out, powerful Virtex 7 field programmable gate array for digital signal processing and 32GB of on board buffer for recording data. We report on the status of the development and our plans to bring the new system into use.
	Slides TUCL03 [2.897 MB]
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IBIC2016-TUCL03
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TUPG12	Design for the Diamond Longitudinal Bunch-by-Bunch Feedback Cavity	340
	A.F.D. Morgan, G. Rehm DLS, Oxfordshire, United Kingdom
	In 2017 it is planned to install some additional normal conducting cavities into the Diamond storage ring. In order to deal with the potential higher order modes in these we are designing a longitudinal bunch-by-bunch feedback system. This paper will focus on the design of the overloaded cavity kicker, adapted to the Diamond beam pipe cross section. The design has evolved in order to reduce the strong 3rd harmonic resonance seen on the introduction of the racetrack beam pipe. Through a combination of geometry optimisation and the addition of integrated taper transitions this harmonic has been greatly reduced while also minimising sharp resonances below 15GHz. The major features will be described, as well as the expected performance parameters.
	Poster TUPG12 [1.423 MB]
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IBIC2016-TUPG12
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WEPG43	A Procedure for the Characterization of Corrector Magnets	728
	S. Gayadeen, M.J. Furseman, G. Rehm DLS, Oxfordshire, United Kingdom
	At Diamond Light source, the main assumption for the Fast Orbit Feedback (FOFB) controller design is that the corrector magnets all have the same dynamic response. In this paper, a procedure to measure the frequency responses of the corrector magnets on the Diamond Storage Ring is presented and the magnet responses are measured and compared in order to assess whether this assumption is valid. The measurements are made by exciting a single corrector magnet with a sinusoidal input and measuring the resulting sinusoidal movement on the electron beam using electron Beam Position Monitors (eBPMs). The input excitation is varied from 10 Hz to 5 kHz using a 10 mA sine wave. The amplitude ratio and the phase difference between the input excitation and the beam position excitation are determined for each input frequency and the procedure is repeated for several magnets. Variations in both gain and phase across magnets are discussed in this paper and the effect of such variations on the performance of the FOFB controller performance is determined.
	Poster WEPG43 [1.137 MB]
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IBIC2016-WEPG43
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WEPG63	Performance Evaluation of Molybdenum Blades in an X-ray Pinhole Camera	795
	L.M. Bobb, A.F.D. Morgan, G. Rehm DLS, Oxfordshire, United Kingdom
	At Diamond Light Source transverse profile measurements of the 3 GeV electron beam are provided by x-ray pinhole cameras. From these beam size measurements and given knowledge of the lattice parameters the emittance, coupling and energy spread are calculated. Traditionally, tungsten blades are used to form the pinhole aperture due to the opacity of tungsten to x-rays in the keV spectral range. The physical properties of tungsten also make it difficult to work. To achieve the 25 micron x 25 micron aperture size required for high resolution measurements it is necessary to mount these tungsten blades in an assembly whereby the pinhole aperture size is defined by precisely machined shims. Here we propose to replace the tungsten blade and shim arrangement with machined molybdenum blades and evaluate the performance of the resulting imaging system.
	Poster WEPG63 [0.825 MB]
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IBIC2016-WEPG63
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

Measurements of Longitudinal Coupled Bunch Instabilities and Status of New Feedback System

298

G. Rehm, M.G. Abbott, A.F.D. Morgan
DLS, Oxfordshire, United Kingdom

We have modified the vertical bunch-by-bunch feedback to also provide a longitudinal kick on a separate input. Using our existing drive/damp system and a modulator/amplifier to the required 1.5 GHz we are thus able to characterise the damping rates of all coupled bunch instabilities, while not able to provide feedback. At the same time, we have started the development of a completely new longitudinal feedback system based on commercially available components, providing 500MS/s, 14 bit conversion in and out, powerful Virtex 7 field programmable gate array for digital signal processing and 32GB of on board buffer for recording data. We report on the status of the development and our plans to bring the new system into use.

Slides TUCL03 [2.897 MB]

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IBIC2016-TUCL03

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPG12

Design for the Diamond Longitudinal Bunch-by-Bunch Feedback Cavity

340

A.F.D. Morgan, G. Rehm
DLS, Oxfordshire, United Kingdom

In 2017 it is planned to install some additional normal conducting cavities into the Diamond storage ring. In order to deal with the potential higher order modes in these we are designing a longitudinal bunch-by-bunch feedback system. This paper will focus on the design of the overloaded cavity kicker, adapted to the Diamond beam pipe cross section. The design has evolved in order to reduce the strong 3rd harmonic resonance seen on the introduction of the racetrack beam pipe. Through a combination of geometry optimisation and the addition of integrated taper transitions this harmonic has been greatly reduced while also minimising sharp resonances below 15GHz. The major features will be described, as well as the expected performance parameters.

Poster TUPG12 [1.423 MB]

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IBIC2016-TUPG12

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPG43

A Procedure for the Characterization of Corrector Magnets

728

S. Gayadeen, M.J. Furseman, G. Rehm
DLS, Oxfordshire, United Kingdom

At Diamond Light source, the main assumption for the Fast Orbit Feedback (FOFB) controller design is that the corrector magnets all have the same dynamic response. In this paper, a procedure to measure the frequency responses of the corrector magnets on the Diamond Storage Ring is presented and the magnet responses are measured and compared in order to assess whether this assumption is valid. The measurements are made by exciting a single corrector magnet with a sinusoidal input and measuring the resulting sinusoidal movement on the electron beam using electron Beam Position Monitors (eBPMs). The input excitation is varied from 10 Hz to 5 kHz using a 10 mA sine wave. The amplitude ratio and the phase difference between the input excitation and the beam position excitation are determined for each input frequency and the procedure is repeated for several magnets. Variations in both gain and phase across magnets are discussed in this paper and the effect of such variations on the performance of the FOFB controller performance is determined.

Poster WEPG43 [1.137 MB]

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IBIC2016-WEPG43

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPG63

Performance Evaluation of Molybdenum Blades in an X-ray Pinhole Camera

795

L.M. Bobb, A.F.D. Morgan, G. Rehm
DLS, Oxfordshire, United Kingdom

At Diamond Light Source transverse profile measurements of the 3 GeV electron beam are provided by x-ray pinhole cameras. From these beam size measurements and given knowledge of the lattice parameters the emittance, coupling and energy spread are calculated. Traditionally, tungsten blades are used to form the pinhole aperture due to the opacity of tungsten to x-rays in the keV spectral range. The physical properties of tungsten also make it difficult to work. To achieve the 25 micron x 25 micron aperture size required for high resolution measurements it is necessary to mount these tungsten blades in an assembly whereby the pinhole aperture size is defined by precisely machined shims. Here we propose to replace the tungsten blade and shim arrangement with machined molybdenum blades and evaluate the performance of the resulting imaging system.

Poster WEPG63 [0.825 MB]

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IBIC2016-WEPG63

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)