IPAC2015 - List of Authors (Hillert, W.)

Paper	Title	Page
MOPWA023	Preserving Information of the Three Spatial Electron Beam Dimensions in One Streak Camera Measurement	144
	M.T. Switka, W. Hillert ELSA, Bonn, Germany
	Funding: Work funded by the DFG within SFB/TRR16 At the pulse stretcher ring ELSA, a streak camera is used for the analysis of visible synchrotron radiation. It functions as fast time resolving beam diagnostic apparatus capable of visualizing dynamics down to the picosecond time range. The optical beamline splits the photon beam and projects the electron beam's image onto the streak camera with transversely perpendicular orientation and slight displacement, thereby providing simultaneous imaging of both transverse planes. Thus, the information of bunch and beam dynamics in three dimensions is preserved and can be observed in slow sweep or synchroscan operation. Characteristics and exemplary measurements, demonstrating the capabilities and limits of this technique, are presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPWA023
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MOPWA024	Estimation of the Ion Density in Accelerators using the Beam Transfer Function Technique	147
	D. Sauerland, W. Hillert ELSA, Bonn, Germany A. Meseck HZB, Berlin, Germany
	Funding: Funded by the federal ministry of education and science of Germany The ELSA stretcher ring of Bonn University serves external hadron physics experiments with a quasi continuous electron beam of up to 3.2 GeV energy. Ions, being generated by collisions of the circulating electrons with the residual gas molecules, accumulate inside the beam potential, causing incoherent tune shifts and coherent beam instabilities. Detailed measurements were carried out in which ion dynamics is studied in dependence of beam energy and current, filling patterns and bias voltages of the ion clearing electrodes. By measuring the beam transfer function using a broadband transversal kicker, we were able to derive an estimate of the average ion density from the shift and broadening of the tune peak. In this contribution first results of these measurements are presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPWA024
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MOPHA012	A New FPGA Based Timing System at ELSA	802
	D. Proft, W. Hillert ELSA, Bonn, Germany
	At the electron stretcher facility ELSA a beam intensity upgrade from 20 mA to 200 mA is in progress. Investigations showed, that the maximum beam current is currently limited by excitation of beam instabilities. For separated characterization of single bunch instabilities from multi-bunch ones, a high beam current stored in a single revolving bunch is required. These high beam currents can only be achieved by accumulation of many shots from the injector. The existing timing system is not capable of single bunch injection and accumulation in the main stretcher ring. Therefore a new FPGA based timing system, synchronized to the RF system of the accelerator, has been developed which will completely supersede the existing one. Simultaneously the ‘‘slow'' timing system, providing trigger signals for the typically 6 s long accelerator cycle, is also modernized using a similar FPGA based solution to achieve a much better duty cycle during standard operation. In this contribution the FPGA designs laying the focus on the single bunch accumulation will be presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPHA012
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MOPHA014	Magnetic Field Parametrization for Efficient Spin Tracking with POLE	808
	J.F. Schmidt, W. Hillert ELSA, Bonn, Germany
	Funding: BMBF The new spin dynamics simulation suite pole is designed to perform systematic studies of beam depolarization in circular accelerators with short storage times or fast energy ramps. It is based on spin tracking using a Runge-Kutta algorithm with adaptive step width. pole can approximate the magnetic fields of the accelerator with a Fourier series to reduce computing time. Therefore, the magnetic field distribution is simplified with frequency filters by a C++ library before the spin tracking. The versatile library deals with import and export of lattices and particle trajectories from MAD-X and Elegant. The derived magnetic field distributions can be interpolated, Fourier transformed and accessed easily by applications. This contribution discusses advantages and disadvantages of the frquency filtering concept.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPHA014
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MOPHA015	Measurement of Momentum Compaction Factor via Depolarizing Resonances at ELSA	811
	J.F. Schmidt, W. Hillert, M. Schedler, J.-P. Thiry ELSA, Bonn, Germany
	Funding: DFG Measuring beam depolarization at energies in close proximity to a depolarizing integer resonance is an established method to determine the beam energy of a circular accelerator. This technique offers high accuracy due to the small resonance widths. Thus, also other accelerator parameters related to beam energy can be measured based on this method. This contribution presents a measurement of the momentum compaction factor with a high precision of 10^-4. It was performed at the 164 m stretcher ring of the Electron Stretcher Facility ELSA at Bonn University, which provides a polarized electron beam of up to 3.2 GeV.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPHA015
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WEPMA014	Development of New Microcontroller Based Power Supply Control Units at ELSA	2777
	D. Proft, W. Hillert, T. Perlitius ELSA, Bonn, Germany
	At the electron stretcher facility ELSA electrons are accelerated with a high ramping speed of 6 GeV/s. This leads to strong requirements on the main magnets power supplies. In particular, any synchronization errors directly result in beam tune shifts and, at worst, beam loss. The existing thirty years old control units are now being replaced by new in-house developed versatile microcontroller based ones. These allow the application of arbitrary ramp patterns and actual value acquisition in realtime. With an ethernet interface the ramp patterns can be uploaded directly to the power supplies. The flexible design also allows usage of the module to control other power supplies, e.g. those of the orbit correction magnets. This presentation will give details on the developed hardware design and the performance of the modules compared to the existing ones.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMA014
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WEPMA015	Water-cooled Thin Walled Beam Pipes of the Fast Ramping Storage Ring ELSA	2780
	P. Hänisch, W. Hillert, B. Neff ELSA, Bonn, Germany
	At the Electron Stretcher Facility ELSA of Bonn University thin walled beam pipes are in use to reduce eddy current loss to a minimum. The operation of the accelerator places high demands on the beam pipes like static stress because of the inner vacuum and additional one-sided thermal stress caused by synchrotron radiation. A first generation of thin walled beam pipes had been developed and manufactured during the construction of the stretcher ring in 1985. These pipes were successfully in operating stage the following ten years. The beam pipes had a wall thickness of 0.3mm, a length of 3m, and a bending radius of ca. 10.5m. Special pipes with a sideway branch for synchrotron radiation experiments have been manufactured in the same assembly dimension. In the course of an intensity upgrade, a second generation of beam pipes has been developed in 1995. To reduce the thermal stress caused by the synchrotron radiation an internal water cooling was mounted. In this contribution the design and manufacturing principles of the thin walled beam pipes with water cooling are presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMA015
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WEPMA016	A New RF station for the ELSA Stretcher Ring	2783
	M. Schedler, A. Dieckmann, P. Hänisch, W. Hillert ELSA, Bonn, Germany
	At the Electron Stretcher Facility ELSA of Bonn University, an increase of the maximum stored beam current from 20 mA to 200 mA is planned. The storage ring operates applying a fast energy ramp of 6 GeV/s from 1.2 GeV to 3.2 GeV and afterwards a slow extraction over a few seconds to the hadron physics experiments. The beam current is mainly limited due to missing RF power at highest energies in order to compensate for synchrotron radiation losses. The current stretcher ring's RF station is based on a single 200 kW klystron driving two 5-cell PETRA type cavities. To achieve the desired beam current at maximum energy two additional 7-cell PETRA type cavities, drivin by a second klystron, will be installed. With this upgrade, sufficient beam lifetime for slow beam extraction will be provided and thus ensure an adequate duty cycle of the external beam current. The general setup of the new RF station as well as the changes in operation when switching from one to two stations will be presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMA016
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Paper

Title

Page

Preserving Information of the Three Spatial Electron Beam Dimensions in One Streak Camera Measurement

144

M.T. Switka, W. Hillert
ELSA, Bonn, Germany

Funding: Work funded by the DFG within SFB/TRR16
At the pulse stretcher ring ELSA, a streak camera is used for the analysis of visible synchrotron radiation. It functions as fast time resolving beam diagnostic apparatus capable of visualizing dynamics down to the picosecond time range. The optical beamline splits the photon beam and projects the electron beam's image onto the streak camera with transversely perpendicular orientation and slight displacement, thereby providing simultaneous imaging of both transverse planes. Thus, the information of bunch and beam dynamics in three dimensions is preserved and can be observed in slow sweep or synchroscan operation. Characteristics and exemplary measurements, demonstrating the capabilities and limits of this technique, are presented.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPWA023

Export •

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

MOPWA024

Estimation of the Ion Density in Accelerators using the Beam Transfer Function Technique

147

D. Sauerland, W. Hillert
ELSA, Bonn, Germany
A. Meseck
HZB, Berlin, Germany

Funding: Funded by the federal ministry of education and science of Germany
The ELSA stretcher ring of Bonn University serves external hadron physics experiments with a quasi continuous electron beam of up to 3.2 GeV energy. Ions, being generated by collisions of the circulating electrons with the residual gas molecules, accumulate inside the beam potential, causing incoherent tune shifts and coherent beam instabilities. Detailed measurements were carried out in which ion dynamics is studied in dependence of beam energy and current, filling patterns and bias voltages of the ion clearing electrodes. By measuring the beam transfer function using a broadband transversal kicker, we were able to derive an estimate of the average ion density from the shift and broadening of the tune peak. In this contribution first results of these measurements are presented.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPWA024

Export •

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

MOPHA012

A New FPGA Based Timing System at ELSA

802

D. Proft, W. Hillert
ELSA, Bonn, Germany

At the electron stretcher facility ELSA a beam intensity upgrade from 20 mA to 200 mA is in progress. Investigations showed, that the maximum beam current is currently limited by excitation of beam instabilities. For separated characterization of single bunch instabilities from multi-bunch ones, a high beam current stored in a single revolving bunch is required. These high beam currents can only be achieved by accumulation of many shots from the injector. The existing timing system is not capable of single bunch injection and accumulation in the main stretcher ring. Therefore a new FPGA based timing system, synchronized to the RF system of the accelerator, has been developed which will completely supersede the existing one. Simultaneously the ‘‘slow'' timing system, providing trigger signals for the typically 6 s long accelerator cycle, is also modernized using a similar FPGA based solution to achieve a much better duty cycle during standard operation. In this contribution the FPGA designs laying the focus on the single bunch accumulation will be presented.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPHA012

Export •

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

MOPHA014

Magnetic Field Parametrization for Efficient Spin Tracking with POLE

808

J.F. Schmidt, W. Hillert
ELSA, Bonn, Germany

Funding: BMBF
The new spin dynamics simulation suite pole is designed to perform systematic studies of beam depolarization in circular accelerators with short storage times or fast energy ramps. It is based on spin tracking using a Runge-Kutta algorithm with adaptive step width. pole can approximate the magnetic fields of the accelerator with a Fourier series to reduce computing time. Therefore, the magnetic field distribution is simplified with frequency filters by a C++ library before the spin tracking. The versatile library deals with import and export of lattices and particle trajectories from MAD-X and Elegant. The derived magnetic field distributions can be interpolated, Fourier transformed and accessed easily by applications. This contribution discusses advantages and disadvantages of the frquency filtering concept.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPHA014

Export •

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

MOPHA015

Measurement of Momentum Compaction Factor via Depolarizing Resonances at ELSA

811

J.F. Schmidt, W. Hillert, M. Schedler, J.-P. Thiry
ELSA, Bonn, Germany

Funding: DFG
Measuring beam depolarization at energies in close proximity to a depolarizing integer resonance is an established method to determine the beam energy of a circular accelerator. This technique offers high accuracy due to the small resonance widths. Thus, also other accelerator parameters related to beam energy can be measured based on this method. This contribution presents a measurement of the momentum compaction factor with a high precision of 10^-4. It was performed at the 164 m stretcher ring of the Electron Stretcher Facility ELSA at Bonn University, which provides a polarized electron beam of up to 3.2 GeV.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPHA015

Export •

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

WEPMA014

Development of New Microcontroller Based Power Supply Control Units at ELSA

2777

D. Proft, W. Hillert, T. Perlitius
ELSA, Bonn, Germany

At the electron stretcher facility ELSA electrons are accelerated with a high ramping speed of 6 GeV/s. This leads to strong requirements on the main magnets power supplies. In particular, any synchronization errors directly result in beam tune shifts and, at worst, beam loss. The existing thirty years old control units are now being replaced by new in-house developed versatile microcontroller based ones. These allow the application of arbitrary ramp patterns and actual value acquisition in realtime. With an ethernet interface the ramp patterns can be uploaded directly to the power supplies. The flexible design also allows usage of the module to control other power supplies, e.g. those of the orbit correction magnets. This presentation will give details on the developed hardware design and the performance of the modules compared to the existing ones.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMA014

Export •

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

WEPMA015

Water-cooled Thin Walled Beam Pipes of the Fast Ramping Storage Ring ELSA

2780

P. Hänisch, W. Hillert, B. Neff
ELSA, Bonn, Germany

At the Electron Stretcher Facility ELSA of Bonn University thin walled beam pipes are in use to reduce eddy current loss to a minimum. The operation of the accelerator places high demands on the beam pipes like static stress because of the inner vacuum and additional one-sided thermal stress caused by synchrotron radiation. A first generation of thin walled beam pipes had been developed and manufactured during the construction of the stretcher ring in 1985. These pipes were successfully in operating stage the following ten years. The beam pipes had a wall thickness of 0.3mm, a length of 3m, and a bending radius of ca. 10.5m. Special pipes with a sideway branch for synchrotron radiation experiments have been manufactured in the same assembly dimension. In the course of an intensity upgrade, a second generation of beam pipes has been developed in 1995. To reduce the thermal stress caused by the synchrotron radiation an internal water cooling was mounted. In this contribution the design and manufacturing principles of the thin walled beam pipes with water cooling are presented.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMA015

Export •

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

WEPMA016

A New RF station for the ELSA Stretcher Ring

2783

M. Schedler, A. Dieckmann, P. Hänisch, W. Hillert
ELSA, Bonn, Germany

At the Electron Stretcher Facility ELSA of Bonn University, an increase of the maximum stored beam current from 20 mA to 200 mA is planned. The storage ring operates applying a fast energy ramp of 6 GeV/s from 1.2 GeV to 3.2 GeV and afterwards a slow extraction over a few seconds to the hadron physics experiments. The beam current is mainly limited due to missing RF power at highest energies in order to compensate for synchrotron radiation losses. The current stretcher ring's RF station is based on a single 200 kW klystron driving two 5-cell PETRA type cavities. To achieve the desired beam current at maximum energy two additional 7-cell PETRA type cavities, drivin by a second klystron, will be installed. With this upgrade, sufficient beam lifetime for slow beam extraction will be provided and thus ensure an adequate duty cycle of the external beam current. The general setup of the new RF station as well as the changes in operation when switching from one to two stations will be presented.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-WEPMA016

Export •

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