FEL2014 - List of Keywords (feedback)

Paper	Title	Other Keywords	Page
MOP008	Temperature Effects of the FLASH2 Undulators	undulator, controls, operation, insertion-device	34
	M. Tischer, A. Schöps, P. Vagin DESY, Hamburg, Germany
	FELs are very sensitive to small changes in the resonance condition of the emitted radiation. As a consequence, permanent magnet undulators in FELs usually require extensive temperature control in order to assure stable operation conditions. In principle, the temperature dependence of permanent magnet material is well known but more things need to be considered like different thermal expansion of various mechanical parts or thermally induced deformation which do not only affect the K parameter but also the field quality. We have performed temperature dependent magnetic measurements in a range from 19 to 28 degrees Celsius and have analyzed the magnetic performance of the undulator. The results of this case study can be transferred to all FLASH2 undulators and shall allow for a simple temperature dependent gap correction in order to make the spectral properties insensitive to temperature changes of the insertion devices.

THB04	Electron Beam Diagnostics and Feedback for the LCLS-II	cavity, diagnostics, controls, undulator	666
	J.C. Frisch, P. Emma, A.S. Fisher, P. Krejcik, H. Loos, T.J. Maxwell, T.O. Raubenheimer, S.R. Smith SLAC, Menlo Park, California, USA
	Funding: work supported by DOE contract DE-AC02-76-SF00515 The LCLS_II is a CW superconducting accelerator driven, hard and soft X-ray Free Electron Laser which is planned to be constructed at SLAC. It will operate with a variety of beam modes from single shot to approximately 1 MHz CW at bunch charges from 10pc to 300pC with average beam powers up to 1.2 MW. A variety of types of beam instrumentation will be used, including stripline and cavity BPMS, fluorescent and OTR based beam profile monitors, fast wire scanners and transverse deflection cavities. The beam diagnostics system is designed to allow tuning and continuous measurement of beam parameters, and to provide signals for fast beam feedbacks.
	Slides THB04 [1.501 MB]

THP043	Model-based Klystron Linearization in the SwissFEL Test Facility	klystron, high-voltage, power-supply, controls	820
	A. Řežaeizadeh, R. Kalt, T. Schilcher PSI, Villigen PSI, Switzerland A. Řežaeizadeh, R. Smith Automatic Control Laboratory, ETH Zurich, Zurich, Switzerland
	Funding: Paul Scherrer Institut An automatic procedure is developed to provide the optimal operating point of a klystron. Since klystrons are nonlinear with respect to the input amplitude, a model-based amplitude controller is introduced which uses the klystron characteristic curves to obtain the appropriate high voltage power supply and amplitude, such that the operating point is close to the saturation. An advantage of the proposed design is that the overall open-loop system (from the input to the RF station to the klystron output amplitude) is linearized. The method has been successfully tested on a full scale RF system running at nominal power. Ch.Rapp, Effects of HPA-Nonlinearity on a 4-DPSK/OFDM-Signal …,Euro. Conf. on Satellite Communi.,1991. <CR> *A.Cann, Nonlinearity Model With Variable Knee…,IEEE Trans. Aerosp. Electron. Syst.,1980

THP044	RF Pulse Flattening in the SwissFEL Test Facility based on Model-free Iterative Learning Control	controls, klystron, electron, flattop	824
	A. Řežaeizadeh, R. Smith Automatic Control Laboratory, ETH Zurich, Zurich, Switzerland A. Řežaeizadeh, T. Schilcher PSI, Villigen PSI, Switzerland
	Funding: Paul Scherrer Institut This paper introduces an iterative approach to producing flat-topped radio frequency (RF) pulses for driving the pulsed linear accelerators in the Swiss free electron laser (SwissFEL). The method is based on model-free iterative learning control which iteratively updates the input pulse shape in order to generate the desired amplitude and phase pulses at the output of the RF system. The method has been successfully applied to the klystron output to improve the flatness of the amplitude and phase pulse profiles. * P. Janssens,et.al, "Model-free iterative learning control for LTI systems …", 18th IFAC. <CR> ** N. Amann, et.al , "ILC for discrete-time systems …", IEE Control Theory Apps.

THP083	Coherent Radiation Diagnostics for Longitudinal Bunch Characterization at European XFEL	radiation, electron, detector, diagnostics	925
	P. Peier, H. Dinter, C. Gerth DESY, Hamburg, Germany
	European XFEL comprises a 17.5 GeV linear accelerator for the generation of hard X-rays. Electron bunches from 20 pC to 1 nC will be produced with a length of a few ps in the RF gun and compressed by three orders of magnitude in three bunch compressor (BC) stages. European XFEL is designed to operate at 10 Hz delivering bunch trains with up to 2700 bunches separated by 222 ns. The high intra-bunch train repetition rate offers the unique possibility of stabilizing the machine with an intra-bunch train feedback, which puts in turn very high demand on fast longitudinal diagnostics. Two different systems will be installed in several positions of the machine. Five bunch compression monitors (BCM) will monitor the compression factor of each BC stage and used for intra-bunch train feedbacks. A THz spectrometer will be used to measure parasitically the longitudinal bunch profile after the energy collimator at 17.5 GeV beam energy. We will present concepts for fast longitudinal diagnostic for European XFEL based on coherent radiation, newest developments for high repetition rate measurements and simulations for the feedback capability of the system.

THP098	CameraLink High-Speed Camera for Bunch Profiling	FPGA, controls, monitoring, hardware	968
	D. Llorente Sancho, H. Brands, R. Ischebeck, P. Pollet, V. Schlott PSI, Villigen PSI, Switzerland
	In the context of upcoming SwissFEL linear accelerator, we are working on a high-speed high-resolution instrument capable of delivering good sensitivity even in dark conditions. The camera selected is a PCO. Edge with SCMOS technology and an ultra-low noise sensor with 2560x2160 pixel resolution working at 100Hz. This allows for single bunch monitoring in SwissFEL, allowing eventually for on-the-fly inter-bunch image processing. The communication between the PCO. Edge camera and a last-generation Kintex7 FPGA has been demonstrated using a prototyping evaluation board and an 850-nm optical link connected to a 10Gbit SFP+ transceiver. Rudimentary packet processing has been implemented to confirm the satisfactory operation of the new link-layer protocol X-CameraLinkHS, specifically development for high-speed image transmission. We aim for online image processing and investigating the feasibility of achieving inter-bunch feedback (< 10 ms).

Paper

Title

Other Keywords

Page

MOP008

Temperature Effects of the FLASH2 Undulators

undulator, controls, operation, insertion-device

34

M. Tischer, A. Schöps, P. Vagin
DESY, Hamburg, Germany

FELs are very sensitive to small changes in the resonance condition of the emitted radiation. As a consequence, permanent magnet undulators in FELs usually require extensive temperature control in order to assure stable operation conditions. In principle, the temperature dependence of permanent magnet material is well known but more things need to be considered like different thermal expansion of various mechanical parts or thermally induced deformation which do not only affect the K parameter but also the field quality. We have performed temperature dependent magnetic measurements in a range from 19 to 28 degrees Celsius and have analyzed the magnetic performance of the undulator. The results of this case study can be transferred to all FLASH2 undulators and shall allow for a simple temperature dependent gap correction in order to make the spectral properties insensitive to temperature changes of the insertion devices.

THB04

Electron Beam Diagnostics and Feedback for the LCLS-II

cavity, diagnostics, controls, undulator

666

J.C. Frisch, P. Emma, A.S. Fisher, P. Krejcik, H. Loos, T.J. Maxwell, T.O. Raubenheimer, S.R. Smith
SLAC, Menlo Park, California, USA

Funding: work supported by DOE contract DE-AC02-76-SF00515
The LCLS_II is a CW superconducting accelerator driven, hard and soft X-ray Free Electron Laser which is planned to be constructed at SLAC. It will operate with a variety of beam modes from single shot to approximately 1 MHz CW at bunch charges from 10pc to 300pC with average beam powers up to 1.2 MW. A variety of types of beam instrumentation will be used, including stripline and cavity BPMS, fluorescent and OTR based beam profile monitors, fast wire scanners and transverse deflection cavities. The beam diagnostics system is designed to allow tuning and continuous measurement of beam parameters, and to provide signals for fast beam feedbacks.

Slides THB04 [1.501 MB]

THP043

Model-based Klystron Linearization in the SwissFEL Test Facility

klystron, high-voltage, power-supply, controls

820

A. Řežaeizadeh, R. Kalt, T. Schilcher
PSI, Villigen PSI, Switzerland
A. Řežaeizadeh, R. Smith
Automatic Control Laboratory, ETH Zurich, Zurich, Switzerland

Funding: Paul Scherrer Institut
An automatic procedure is developed to provide the optimal operating point of a klystron. Since klystrons are nonlinear with respect to the input amplitude, a model-based amplitude controller is introduced which uses the klystron characteristic curves to obtain the appropriate high voltage power supply and amplitude, such that the operating point is close to the saturation. An advantage of the proposed design is that the overall open-loop system (from the input to the RF station to the klystron output amplitude) is linearized. The method has been successfully tested on a full scale RF system running at nominal power.
*Ch.Rapp, Effects of HPA-Nonlinearity on a 4-DPSK/OFDM-Signal …,Euro.
Conf. on Satellite Communi.,1991. <CR>
**A.Cann, Nonlinearity Model With Variable Knee…,IEEE Trans. Aerosp. Electron. Syst.,1980

THP044

RF Pulse Flattening in the SwissFEL Test Facility based on Model-free Iterative Learning Control

controls, klystron, electron, flattop

824

A. Řežaeizadeh, R. Smith
Automatic Control Laboratory, ETH Zurich, Zurich, Switzerland
A. Řežaeizadeh, T. Schilcher
PSI, Villigen PSI, Switzerland

Funding: Paul Scherrer Institut
This paper introduces an iterative approach to producing flat-topped radio frequency (RF) pulses for driving the pulsed linear accelerators in the Swiss free electron laser (SwissFEL). The method is based on model-free iterative learning control which iteratively updates the input pulse shape in order to generate the desired amplitude and phase pulses at the output of the RF system. The method has been successfully applied to the klystron output to improve the flatness of the amplitude and phase pulse profiles.
* P. Janssens,et.al, "Model-free iterative learning control for LTI systems …", 18th IFAC. <CR>
** N. Amann, et.al , "ILC for discrete-time systems …", IEE Control Theory Apps.

THP083

Coherent Radiation Diagnostics for Longitudinal Bunch Characterization at European XFEL

radiation, electron, detector, diagnostics

925

P. Peier, H. Dinter, C. Gerth
DESY, Hamburg, Germany

European XFEL comprises a 17.5 GeV linear accelerator for the generation of hard X-rays. Electron bunches from 20 pC to 1 nC will be produced with a length of a few ps in the RF gun and compressed by three orders of magnitude in three bunch compressor (BC) stages. European XFEL is designed to operate at 10 Hz delivering bunch trains with up to 2700 bunches separated by 222 ns. The high intra-bunch train repetition rate offers the unique possibility of stabilizing the machine with an intra-bunch train feedback, which puts in turn very high demand on fast longitudinal diagnostics. Two different systems will be installed in several positions of the machine. Five bunch compression monitors (BCM) will monitor the compression factor of each BC stage and used for intra-bunch train feedbacks. A THz spectrometer will be used to measure parasitically the longitudinal bunch profile after the energy collimator at 17.5 GeV beam energy. We will present concepts for fast longitudinal diagnostic for European XFEL based on coherent radiation, newest developments for high repetition rate measurements and simulations for the feedback capability of the system.

THP098

CameraLink High-Speed Camera for Bunch Profiling

FPGA, controls, monitoring, hardware

968

D. Llorente Sancho, H. Brands, R. Ischebeck, P. Pollet, V. Schlott
PSI, Villigen PSI, Switzerland

In the context of upcoming SwissFEL linear accelerator, we are working on a high-speed high-resolution instrument capable of delivering good sensitivity even in dark conditions. The camera selected is a PCO. Edge with SCMOS technology and an ultra-low noise sensor with 2560x2160 pixel resolution working at 100Hz. This allows for single bunch monitoring in SwissFEL, allowing eventually for on-the-fly inter-bunch image processing. The communication between the PCO. Edge camera and a last-generation Kintex7 FPGA has been demonstrated using a prototyping evaluation board and an 850-nm optical link connected to a 10Gbit SFP+ transceiver. Rudimentary packet processing has been implemented to confirm the satisfactory operation of the new link-layer protocol X-CameraLinkHS, specifically development for high-speed image transmission. We aim for online image processing and investigating the feasibility of achieving inter-bunch feedback (< 10 ms).