DIPAC2011 - List of Keywords (polarization)

Paper	Title	Other Keywords	Page
MOOB01	An Aperture Backscatter X-ray Beam Position Monitor at Diamond	photon, vacuum, scattering, undulator	6
	C. Bloomer, G. Rehm, C.A. Thomas Diamond, Oxfordshire, United Kingdom
	This paper presents the design and first results of a new XBPM developed at Diamond that images the backscatter from an aperture in the Front End to measure the beam centre of mass. This is of particular interest for monitoring the emission from elliptically polarizing undulators where the profile of the beam varies strongly with change of beam polarization. Traditional four-blade Front End XBPMs struggle to resolve a beam centre of mass for EPUs because of this. We have developed an XBPM that observes the backscattered photons from a copper aperture through a pinhole. This solution is capable of operating with the full white beam, and has been designed to fit into the same physical space as the standard front end XBPMs in use at Diamond. This offers the potential to easily replace traditional XBPMs where beneficial and required.
	Slides MOOB01 [7.211 MB]

MOPD17	Beam-based HOM Study in Third Harmonic SC Cavities for Beam Alignment at FLASH	HOM, cavity, dipole, electron	77
	P. Zhang, R.M. Jones, I.R.R. Shinton UMAN, Manchester, United Kingdom N. Baboi, B. Lorbeer, P. Zhang DESY, Hamburg, Germany H. Ecklebe, T. Flisgen, H.-W. Glock Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
	Funding: Work supported by European Commission under the FP7 Research Infrastructures grant agreement No.227579. An electron beam entering an accelerator cavity excites higher order modes (HOM). These are radiated to HOM couplers, subsequently damped, and can also be used to facilitate beam monitoring. The modes which deflect the beam transversely are the focus of this study and are used to monitor the beam position. Results are presented on the first analysis of beam alignment based on HOM signals from the third harmonic cavities at FLASH. The electrical center of each mode is ascertained by moving the beam to minimize the HOM signal detected. A single electron bunch per RF pulse is used.

MOPD25	Diode Down-mixing of HOM Coupler Signals for Beam Position Determination in 1.3-GHz- and 3.9-GHz-Cavities at FLASH	HOM, cavity, dipole, coupling	101
	H.-W. Glock, H. Ecklebe, T. Flisgen Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany N. Baboi, P. Zhang DESY, Hamburg, Germany
	Funding: work supported by BMBF under contract 05K10HRC and by European Commission under the FP7 Research Infrastructures grant agreement No.227579 Beam excited signals available at the HOM coupler ports of superconducting accelerating cavities cover a wide frequency range and carry information about (amongst others) transverse beam position. Down-mixing these signals using detector diodes is a mean to measure with standard and non-specific oscilloscope technology the time dependency of the power leaving the HOM coupler. Experiments undertaken at the accelerator modules ACC1 and ACC39 at FLASH demonstrated the possibility to extract beam position data out of low-frequency signals sampled with such a setup. These experiments as part of an ongoing study are described together with mathematical details of the evaluation scheme.

TUPD14	Commissioning of the Cavity BPM for the FERMI@Elettra FEL Project	cavity, electron, FEL, undulator	329
	P. Craievich, T. Borden, A.O. Borga, R. De Monte, M. Ferianis, M. Predonzani ELETTRA, Basovizza, Italy M. Dal Forno, R. Vescovo DIEIT, Trieste, Italy
	The cavity Beam Position Monitor (BPM) is a fundamental beam diagnostic device that allows the measurements of the electron beam trajectory in a non-destructively way and with sub-micron resolution. Ten cavity BPM systems have been installed along the undulators chain in the FERMI@Elettra FEL1 project. In this paper we discuss the installation, commissioning and performance of these cavity BPM systems. We have carried out preliminary operations during a pre-beam period, such as the alignment and fine tuning of the RF cavities under vacuum. During the commissioning each BPM has been calibrated by mechanically moving the support on which the BPM is mounted. We have estimated the single shot resolution in presence of beam jitter by reading the beam position synchronously over many electron bunches from three or more BPMs. The algorithms have been subsequently improved, and the results are described.
	Poster TUPD14 [0.460 MB]

TUPD68	Feasibility Study for a Single-Shot 3D Electron Bunch Charge Distribution Monitor with a Polarized Probe Laser at SPring-8 Photoinjector	laser, electron, gun, monitoring	464
	Y. Okayasu, H. Dewa, H. Hanaki, S. Matsubara, A. Mizuno, S. Suzuki, T. Taniuchi, H. Tomizawa, K. Yanagida JASRI/SPring-8, Hyogo-ken, Japan T. Ishikawa RIKEN Spring-8 Harima, Hyogo, Japan A. Maekawa, M. Uesaka The University of Tokyo, Nuclear Professional School, Ibaraki-ken, Japan
	It is essential for precise characterizations of light sources to monitor ever-changing charge distribution of electron bunch by single-shot measurement with high resolutions. Therefore, a single-shot and non-destructive 3D bunch charge distribution (BCD) monitor was developed to characterize longitudinal and transverse BCDs simultaneously. It is based on Electro-Optical (EO) multiple sampling with a manner of spectral decoding. For the transverse detection, eight EO-crystals surround the beam axis azimuthally, and a linear-chirped probe laser pulse with a hollow shape and spirally temporal shift, passes through the EO-crystals. A principle verification experiment has been successfully carried out with two EO-crystals in our facility. In addition, we are promoting a numerical calculation of the ultra-short and radial polarized laser transportation for our own system assuming eight EO-crystals usage in order to confirm observation feasibility. We report the principle and the first experimental results of the novel 3D-BCD monitor and introduce the feasibility demonstration with a calculation about a propagation of transverse polarization distributions along probe laser optics.
	Poster TUPD68 [4.684 MB]

TUPD73	Fast Orbit Stabilization System for Tandem APPLE-II Undulators at the KEK-PF	kicker, undulator, controls, power-supply	479
	T. Obina, K. Harada, R. Takai KEK, Ibaraki, Japan
	A rapid-polarization switching source has been developed in the KEK-PF 2.5-GeV electron storage ring. The source consists of two tandem APPLE-II type elliptically polarizing undulators (EPU) and five fast kicker magnets. The kicker magnets produce a local bump orbit at the frequency up to 100 Hz. Amplitude and phase of these magnets must be tuned precisely in order to minimize the leakage of residual orbit outside of the kicker bump. A fast orbit stabilization system which consists of ADC/FPGA/DAC are also developed to reduce the remaining orbit fluctuations in vertical and horizontal planes. In this paper, design and the preliminary result of the fast orbit compensation system is presented.

TUPD89	Polarimetry of 0.1 – 130 MeV Electron Beams at the S-DALINAC*	electron, laser, linac, photon	515
	C. Eckardt, P. Bangert, R. Barday, U. Bonnes, R. Eichhorn, J. Enders, C. Ingenhaag, Y. Poltoratska, M. Wagner TU Darmstadt, Darmstadt, Germany
	Funding: * Work supported by DFG through SFB 634 and by the state of Hesse through the Helmholtz International Center for FAIR in the framework of the LOEWE program. A source of polarized electrons[1] has been installed at the superconducting 130 MeV Darmstadt electron linear accelerator S-DALINAC[2], augmenting the experimental program for nuclear structure studies and fundamental experiments. Polarized electrons from a strained-superlattice GaAs cathode are electrostatically accelerated to 100 keV. In the low-energy beam line the beam parameters are measured using diagnostic elements like wire scanners and RF-monitors, a Wien filter for spin manipulation and a 100 keV Mott polarimeter for polarization measurement. Following a superconducting accelerator section, electron beams with 5-10 MeV energy are used for bremsstrahlung experiments. Here, the absolute degree of polarization will be measured using a Mott polarimeter, while monitoring the beam polarization during the experiment with a Compton transmission polarimeter. Alternatively, the electron beam can be further accelerated in the recirculating superconducting main linac. For beam energies of 50-130 MeV a Moeller polarimeter as well as two Compton transmission polarimeter are foreseen. We report on the performance of the polarized source and the polarimeter design and installation. [1] C. Eckardt et al., IPAC 10, Kyoto, _{_}THPEC019_{_}, p 4083. [2] A. Richter, Proc. EPAC 96, Sitges, _{_}WEX02A_{_}, p.110.

Paper

Title

Other Keywords

Page

MOOB01

An Aperture Backscatter X-ray Beam Position Monitor at Diamond

photon, vacuum, scattering, undulator

6

C. Bloomer, G. Rehm, C.A. Thomas
Diamond, Oxfordshire, United Kingdom

This paper presents the design and first results of a new XBPM developed at Diamond that images the backscatter from an aperture in the Front End to measure the beam centre of mass. This is of particular interest for monitoring the emission from elliptically polarizing undulators where the profile of the beam varies strongly with change of beam polarization. Traditional four-blade Front End XBPMs struggle to resolve a beam centre of mass for EPUs because of this. We have developed an XBPM that observes the backscattered photons from a copper aperture through a pinhole. This solution is capable of operating with the full white beam, and has been designed to fit into the same physical space as the standard front end XBPMs in use at Diamond. This offers the potential to easily replace traditional XBPMs where beneficial and required.

Slides MOOB01 [7.211 MB]

MOPD17

Beam-based HOM Study in Third Harmonic SC Cavities for Beam Alignment at FLASH

HOM, cavity, dipole, electron

77

P. Zhang, R.M. Jones, I.R.R. Shinton
UMAN, Manchester, United Kingdom
N. Baboi, B. Lorbeer, P. Zhang
DESY, Hamburg, Germany
H. Ecklebe, T. Flisgen, H.-W. Glock
Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany

Funding: Work supported by European Commission under the FP7 Research Infrastructures grant agreement No.227579.
An electron beam entering an accelerator cavity excites higher order modes (HOM). These are radiated to HOM couplers, subsequently damped, and can also be used to facilitate beam monitoring. The modes which deflect the beam transversely are the focus of this study and are used to monitor the beam position. Results are presented on the first analysis of beam alignment based on HOM signals from the third harmonic cavities at FLASH. The electrical center of each mode is ascertained by moving the beam to minimize the HOM signal detected. A single electron bunch per RF pulse is used.

MOPD25

Diode Down-mixing of HOM Coupler Signals for Beam Position Determination in 1.3-GHz- and 3.9-GHz-Cavities at FLASH

HOM, cavity, dipole, coupling

101

H.-W. Glock, H. Ecklebe, T. Flisgen
Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
N. Baboi, P. Zhang
DESY, Hamburg, Germany

Funding: work supported by BMBF under contract 05K10HRC and by European Commission under the FP7 Research Infrastructures grant agreement No.227579
Beam excited signals available at the HOM coupler ports of superconducting accelerating cavities cover a wide frequency range and carry information about (amongst others) transverse beam position. Down-mixing these signals using detector diodes is a mean to measure with standard and non-specific oscilloscope technology the time dependency of the power leaving the HOM coupler. Experiments undertaken at the accelerator modules ACC1 and ACC39 at FLASH demonstrated the possibility to extract beam position data out of low-frequency signals sampled with such a setup. These experiments as part of an ongoing study are described together with mathematical details of the evaluation scheme.

TUPD14

Commissioning of the Cavity BPM for the FERMI@Elettra FEL Project

cavity, electron, FEL, undulator

329

P. Craievich, T. Borden, A.O. Borga, R. De Monte, M. Ferianis, M. Predonzani
ELETTRA, Basovizza, Italy
M. Dal Forno, R. Vescovo
DIEIT, Trieste, Italy

The cavity Beam Position Monitor (BPM) is a fundamental beam diagnostic device that allows the measurements of the electron beam trajectory in a non-destructively way and with sub-micron resolution. Ten cavity BPM systems have been installed along the undulators chain in the FERMI@Elettra FEL1 project. In this paper we discuss the installation, commissioning and performance of these cavity BPM systems. We have carried out preliminary operations during a pre-beam period, such as the alignment and fine tuning of the RF cavities under vacuum. During the commissioning each BPM has been calibrated by mechanically moving the support on which the BPM is mounted. We have estimated the single shot resolution in presence of beam jitter by reading the beam position synchronously over many electron bunches from three or more BPMs. The algorithms have been subsequently improved, and the results are described.

Poster TUPD14 [0.460 MB]

TUPD68

Feasibility Study for a Single-Shot 3D Electron Bunch Charge Distribution Monitor with a Polarized Probe Laser at SPring-8 Photoinjector

laser, electron, gun, monitoring

464

Y. Okayasu, H. Dewa, H. Hanaki, S. Matsubara, A. Mizuno, S. Suzuki, T. Taniuchi, H. Tomizawa, K. Yanagida
JASRI/SPring-8, Hyogo-ken, Japan
T. Ishikawa
RIKEN Spring-8 Harima, Hyogo, Japan
A. Maekawa, M. Uesaka
The University of Tokyo, Nuclear Professional School, Ibaraki-ken, Japan

It is essential for precise characterizations of light sources to monitor ever-changing charge distribution of electron bunch by single-shot measurement with high resolutions. Therefore, a single-shot and non-destructive 3D bunch charge distribution (BCD) monitor was developed to characterize longitudinal and transverse BCDs simultaneously. It is based on Electro-Optical (EO) multiple sampling with a manner of spectral decoding. For the transverse detection, eight EO-crystals surround the beam axis azimuthally, and a linear-chirped probe laser pulse with a hollow shape and spirally temporal shift, passes through the EO-crystals. A principle verification experiment has been successfully carried out with two EO-crystals in our facility. In addition, we are promoting a numerical calculation of the ultra-short and radial polarized laser transportation for our own system assuming eight EO-crystals usage in order to confirm observation feasibility. We report the principle and the first experimental results of the novel 3D-BCD monitor and introduce the feasibility demonstration with a calculation about a propagation of transverse polarization distributions along probe laser optics.

Poster TUPD68 [4.684 MB]

TUPD73

Fast Orbit Stabilization System for Tandem APPLE-II Undulators at the KEK-PF

kicker, undulator, controls, power-supply

479

T. Obina, K. Harada, R. Takai
KEK, Ibaraki, Japan

A rapid-polarization switching source has been developed in the KEK-PF 2.5-GeV electron storage ring. The source consists of two tandem APPLE-II type elliptically polarizing undulators (EPU) and five fast kicker magnets. The kicker magnets produce a local bump orbit at the frequency up to 100 Hz. Amplitude and phase of these magnets must be tuned precisely in order to minimize the leakage of residual orbit outside of the kicker bump. A fast orbit stabilization system which consists of ADC/FPGA/DAC are also developed to reduce the remaining orbit fluctuations in vertical and horizontal planes. In this paper, design and the preliminary result of the fast orbit compensation system is presented.

TUPD89

Polarimetry of 0.1 – 130 MeV Electron Beams at the S-DALINAC*

electron, laser, linac, photon

515

C. Eckardt, P. Bangert, R. Barday, U. Bonnes, R. Eichhorn, J. Enders, C. Ingenhaag, Y. Poltoratska, M. Wagner
TU Darmstadt, Darmstadt, Germany

Funding: * Work supported by DFG through SFB 634 and by the state of Hesse through the Helmholtz International Center for FAIR in the framework of the LOEWE program.
A source of polarized electrons[1] has been installed at the superconducting 130 MeV Darmstadt electron linear accelerator S-DALINAC[2], augmenting the experimental program for nuclear structure studies and fundamental experiments. Polarized electrons from a strained-superlattice GaAs cathode are electrostatically accelerated to 100 keV. In the low-energy beam line the beam parameters are measured using diagnostic elements like wire scanners and RF-monitors, a Wien filter for spin manipulation and a 100 keV Mott polarimeter for polarization measurement. Following a superconducting accelerator section, electron beams with 5-10 MeV energy are used for bremsstrahlung experiments. Here, the absolute degree of polarization will be measured using a Mott polarimeter, while monitoring the beam polarization during the experiment with a Compton transmission polarimeter. Alternatively, the electron beam can be further accelerated in the recirculating superconducting main linac. For beam energies of 50-130 MeV a Moeller polarimeter as well as two Compton transmission polarimeter are foreseen. We report on the performance of the polarized source and the polarimeter design and installation.
[1] C. Eckardt et al., IPAC 10, Kyoto, _{_}THPEC019_{_}, p 4083.
[2] A. Richter, Proc. EPAC 96, Sitges, _{_}WEX02A_{_}, p.110.