IPAC2014 - List of Authors (Michel, P.)

Paper	Title	Page
MOPME044	Upgrade of the Machine Interlock System for the ELBE Accelerator Facility	469
	M. Justus, M. Freitag, B. Lange, P. Michel, W. Sorge, R. Steinbrück, H. Tietze HZDR, Dresden, Germany
	The ELBE facility with its 40 MeV C.W. LINAC has recently received an upgrade in terms of new secondary radiation sources and beam lines, while advancing the accelerator infrastructure towards 1.6 mA C.W. operation (1.0 mA before). Therefore, the machine interlock system (MIS) was redesigned in parts to meet the new timing requirements resulting from the increased overall beam power. It comprises fast beam loss detection and a PLC based beam line equipment protection system (EPS), both tripping the key components of the electron sources. The former tripping system using PLC interrupts was replaced by an in-house developed staggered CPLD based system with optical transmission and a PROFINET IO interface for control system integration. The EPS is distributed on several PLCs and has been improved in terms of M2M communication. Further, the vacuum inrush protection was completely renewed using brought-in equipment. This contribution depicts the technical features and performance of the MIS subsystems, as well as the actual status within the upgrade project.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPME044
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MOPME067	Kicker Development at the ELBE Facility	520
	G.S. Staats FZD, Dresden, Germany A. Arnold, H. Büttig, T. Kirschke, M. Kuntzsch, P. Michel, J. Teichert, H. Vennekate, A. Wagner, R. Xiang HZDR, Dresden, Germany R. Krause-Rehberg, A. Müller Martin-Luther-Universität, Naturwissenschaftliche Fakultät II, Halle (Saale), Germany
	Kicker-devices, also known as choppers, are of great interest for a multi-purpose electron accelerator like the ELBE at HZDR. They serve the following three main tasks: Firstly, they can be used to improve the time resolution for the positron beam line by removing certain parts of the bunch. As a second advantage they enable the machine to run two independent experiments at the same, as a chopper may split the beam into two separate parts. Lastly, a well-positioned kicker can reduce the dark current emitted by the SRF injector of the accelerator. Different designs for structures, deflecting the bunch in the beam line, have been simulated using CST Particle Studio. Here, no big difference to well-known strip line structures do exist. The next step is to design the supply electronics driving the kickers. As the ELBE accelerator runs at a high bunch repetition rate, the kicker has to keep up to this frequencies of up to 13 MHz. Hence, the high power levels needed for the operation may cause additional problems for the driver electronics. The poster is going to present the state of our development for all three tasks and our approaches to solve the corresponding challenges.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPME067
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MOPRI024	NEA-GaAs (Cs, O) Photocathodes for the ELBE SRF Gun	639
	R. Xiang, A. Arnold, P.N. Lu, P. Michel, P. Murcek, J. Teichert, H. Vennekate HZDR, Dresden, Germany
	Funding: supported by the European Community under the FP7 programme (EuCARD-2, contract number 312453, and LA3NET, contract number 289191), and by the BMBF grant 05K12CR1. At HZDR a preparation chamber for NEA-GaAs (Cs, O) has been built and commissioned. GaAs is the next photocathode material for the ELBE SRF gun, which has been successfully operated with Cs2Te layer in last years. GaAs At HZDR a preparation chamber for NEA-GaAs (Cs, O) has been built and tested. GaAs is the next photocathode material for the ELBE SRF gun, which has been successfully operated with Cs2Te photocathode in last years. GaAs photocathodes are advantageous because of their high quantum efficiency (QE) with visible light and the extensive experiences of their use in DC guns. Furthermore, GaAs photocathodes provide the possibility to realize a polarized SRF gun in the future. In this presentation we will introduce the new preparation system and the first results of the GaAs tests. The new transfer system under construction will be also presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRI024
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MOPRI025	Recent Improvement of Cs2Te Photocathodes at HZDR	642
	R. Xiang, A. Arnold, P.N. Lu, P. Michel, P. Murcek, J. Teichert, H. Vennekate HZDR, Dresden, Germany
	Funding: Work supported by the European Community-Research Infrastructure Activity (EuCARD, contract number 227579), and the support of the German Federal Ministry of Education and Research grant 05 ES4BR1/8. The SRF gun has been successfully operated for the radiation source ELBE at HZDR. To achieve higher current and lower beam emittance, a new niobium cavity with superconducting solenoid and a new 13 MHz laser have been recently developed. For this reason, better photocathodes with high quantum efficiency are urgently in demand. In this work we improve the present Cs2Te preparation system for cleaner environment and more precise stoichiometric control than before. A new mask is designed to prevent cesium pollution of the cathode body. Instead of Kapton only alumina ceramics are used for isolation, and the cathode plugs are degassed at higher temperature. New evaporators are installed and tested to obtain an accurate deposition rate. Furthermore, the cathode transfer system is thoroughly cleaned for a better vacuum condition.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRI025
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TUZA02	THz Facility at ELBE: A Versatile Test Facility for Electron Bunch Diagnostics on Quasi-CW Electron Beams	933
	M. Gensch, B.W. Green, J. Hauser, S. Kovalev, M. Kuntzsch, U. Lehnert, P. Michel, R. Schurig HZDR, Dresden, Germany A. Al-Shemmary, V. B. Asgekar, T. Golz, H. Schlarb, N. Stojanovic, S. Vilcins DESY, Hamburg, Germany A.S. Fisher SLAC, Menlo Park, California, USA G. Geloni XFEL. EU, Hamburg, Germany A.-S. Müller, M. Schwarz KIT, Karlsruhe, Germany N.E. Neumann, D. Plettemeier TU Dresden, Dresden, Germany
	At the Helmholtz-Zentrum Dresden-Rossendorf near Dresden a quasi-cw low-energy electron linear accelerator based on superconducting radiofrequency technology is operated successfully for more than 10 years. The ELBE accelerator is driving several secondary radiation sources including 2 infrared free electron lasers. A new addition will be a THz facility that aims to make use of super-radiant THz radiation. In its final form the THz facility shall consist of one coherent diffraction radiator and one undulator source which provide high-field THz pulses at unprecedented repetition rates. While the medium term goal is to establish a unique user facility for nonlinear THz science, the THz sources are already used as a test facility for novel diagnostic techniques on quasi-cw electron beams. The progress of the developments is reported and an outlook into future challenges and opportunities is given.
	Slides TUZA02 [3.041 MB]
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TUPRO044	Bunch Compression of the Low-energy ELBE Electron Beam for Super-radiant THz Sources	1123
	U. Lehnert, P. Michel, R. Schurig HZDR, Dresden, Germany A.A. Aksoy Ankara University, Accelerator Technologies Institute, Golbasi / Ankara, Turkey P.E. Evtushenko JLab, Newport News, Virginia, USA J.M. Krämer Danfysik A/S, Taastrup, Denmark
	At the ELBE radiation source two super-radiant THz sources, a broad-band trasnsition/diffraction radiation source and a planar undulator narrow-band sourc are under commissioning. At present the facility is driven from the ELBE linac with a CW electron beam of 100kHz repetition rate and up to 100pC of bunch charge. With the upgraded SRF electron gun bunch charges up to 1nC will become available. For the beam energies in the 20-30 MeV range buch compression into the sub-200 fs range becomes a major challenge. We present beam dynamics calculation of the attempted bunch compression scheme as well as first measurements obtained during the commissioning.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRO044
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WEPRO113	Status of the Radiation Source ELBE Upgrade	2233
	P. Michel, T.E. Cowan, U. Lehnert, U. Schramm HZDR, Dresden, Germany
	ELBE is based on a 40 MeV superconducting Electron Linac able to operate in CW mode and provides manifold secondary user beams. The suite of secondary beams include: two free electron lasers operating in the IR/THz regime; a fast neutron beam; a Bremsstrahlung gamma-ray beam; a low-energy positron beam; and patented single-electron test beams. The primary electron beam is also used for radiobiology research, or in interaction with ultra-intense PW-class lasers. Through 2014 ELBE will be upgraded to a Centre for High Power Radiation Sources. The ELBE beam current was increased to 1.6 mA by using novel solid state RF amplifiers. The concept also contains additional broad and narrow band coherent THz sources and the development of a 500 TW TiSa Laser and even a 1.5 PW diode pumped laser system. Laser plasma electron acceleration and proton acceleration experiments for medical applications are planned. Additionally, coupled electron laser beam experiments like Thomson scattering or injection of ELBE electron into the laser plasma will be done.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPRO113
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WEPME003	Two Years Experience with the Upgraded ELBE RF System Driven by 20kW Solid State Amplifier Blocks (SSPA)	2257
	H. Büttig, A. Arnold, A. Büchner, M. Justus, M. Kuntzsch, U. Lehnert, P. Michel, R. Schurig, G.S. Staats, J. Teichert HZDR, Dresden, Germany
	Since January 2012 the Superconducting CW Linac ELBE is equipped and in permanent operation with four 20 kW Solid State Amplifier Blocks. The poster gives an overview on the design of the new RF system and the experience gained within the first two years of operation.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPME003
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THPRO012	Wakefield-based Dechirper Structures for ELBE	2882
	F. Reimann, U. van Rienen Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany U. Lehnert, P. Michel HZDR, Dresden, Germany
	Funding: Federal Ministry of Education and Research The efficient reduction of the pulse length and the energy width of electron beams plays a crucial role in the generation of short pulses in the range of sub-picoseconds at future light sources. At the radiation source ELBE in Dresden Rossendorf short pulses are required for coherent THz generation and laser-electron beam interaction experiments such as X-ray Thomson scattering. Energy dechirping can be carried out passively by wakefields generated when the electron beam passes through suitable structures, namely corrugated and dielectrically lined cylindrical pipes or dielectrically lined rectangular waveguides (,,*). All structures offer the possibility to tune the resulting wakefield and therefore the resulting energy chirp through a variation of purely geometrical or material parameters. In this paper we present a semi-analytical approach to determine the wakefield in dielectrically lined rectangular waveguide, starting with the expression of the electric field in terms of the structure's eigenmodes. Bane, Stupakov, SLAC-PUB-14925 (2012) Mosnier, Novokhatski, in: Proceedings of PAC97, Vancouver, Canada, 1997 * Antipov et al., in: Proceedings of IPAC2012, New Orleans, USA, 2012
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRO012
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THPRO055	Electron Beam Final Focus System for Thomson Scattering at ELBE	2995
	J.M. Krämer, F. Bødker, A. Baurichter, M. Budde Danfysik A/S, Taastrup, Denmark A. Irman, U. Schramm Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Institute of Radiation Physics, Dresden, Germany U. Lehnert, P. Michel HZDR, Dresden, Germany
	Funding: This work is part of LA3NET and funded by European Commission under Grant Agreement Number 289191. The design of an electron beam Final Focus System (FFS) aiming for high-flux laser-Thomson backscattering x-ray sources at ELBE* is presented. A telescope system consisting of four permanent magnet based quadrupoles was found to have significantly less chromatic aberrations than a quadrupole triplet. This allows sub-ps electron beam focusing to match the laser spot size at the interaction point. Focusing properties like the position of the focal plane and the spot size are retained for electron beam energies between 20 and 30 MeV by adjusting the position of the quadrupoles individually on a motorized stage. Since the electron beam is chirped for bunch compression upstream, the rms energy spread is increased to one or two percent and second order chromatic effects must be taken into account. For an emittance of 13 pi mm mrad, we predict rms spot sizes of about 40 um and divergences of about 15 mrad. We also present the design of the permanent magnet quadrupoles to be used for the FFS. Ferromagnetic poles ensure a high field quality and adjustable shunts allow for fine adjustment of the field strength and compensation of deviations in the permanent magnet material. *A. Jochmann et al., Phys. Rev. Lett. 111 (2013) 114803
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRO055
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THPME109	EOS at CW Beam Operation at ELBE	3492
	Ch. Schneider, M. Gensch, M. Kuntzsch, P. Michel, W. Seidel HZDR, Dresden, Germany P.E. Evtushenko JLab, Newport News, Virginia, USA Ç. Kaya Ankara University, Accelerator Technologies Institute, Golbasi / Ankara, Turkey A. Shemmary, N. Stojanovic DESY, Hamburg, Germany
	The ELBE accelerator is a super conduction electron cw machine located at the Helmholtz Center Dresden Rossendorf Germany with 1 mA current, now tested for up to 2 mA. Besides other important diagnostics for setting up the machine for user beam time and further improvement of the machine – a THz source is momentary under commissioning – a EOS measuring station for bunch length measurements is locate right behind the second super conducting Linac. Measuring with a crystal in the vicinity of an up to 2 mA cw beam implies higher beam loss and also higher radiation exposure of the crystal and hence also a safety risk for the UHV conditions of the super conducting cavities in the case of crystal damage. Therefore the EOS measuring principle is adapted to larger measuring distances and also for beam requirements with lower bunch charge at ELBE. A description of the setup, considerations of special boundary conditions and as well results for 13 MHz cw beam operation are presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPME109
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Paper

Title

Page

Upgrade of the Machine Interlock System for the ELBE Accelerator Facility

469

M. Justus, M. Freitag, B. Lange, P. Michel, W. Sorge, R. Steinbrück, H. Tietze
HZDR, Dresden, Germany

The ELBE facility with its 40 MeV C.W. LINAC has recently received an upgrade in terms of new secondary radiation sources and beam lines, while advancing the accelerator infrastructure towards 1.6 mA C.W. operation (1.0 mA before). Therefore, the machine interlock system (MIS) was redesigned in parts to meet the new timing requirements resulting from the increased overall beam power. It comprises fast beam loss detection and a PLC based beam line equipment protection system (EPS), both tripping the key components of the electron sources. The former tripping system using PLC interrupts was replaced by an in-house developed staggered CPLD based system with optical transmission and a PROFINET IO interface for control system integration. The EPS is distributed on several PLCs and has been improved in terms of M2M communication. Further, the vacuum inrush protection was completely renewed using brought-in equipment. This contribution depicts the technical features and performance of the MIS subsystems, as well as the actual status within the upgrade project.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPME044

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MOPME067

Kicker Development at the ELBE Facility

520

G.S. Staats
FZD, Dresden, Germany
A. Arnold, H. Büttig, T. Kirschke, M. Kuntzsch, P. Michel, J. Teichert, H. Vennekate, A. Wagner, R. Xiang
HZDR, Dresden, Germany
R. Krause-Rehberg, A. Müller
Martin-Luther-Universität, Naturwissenschaftliche Fakultät II, Halle (Saale), Germany

Kicker-devices, also known as choppers, are of great interest for a multi-purpose electron accelerator like the ELBE at HZDR. They serve the following three main tasks: Firstly, they can be used to improve the time resolution for the positron beam line by removing certain parts of the bunch. As a second advantage they enable the machine to run two independent experiments at the same, as a chopper may split the beam into two separate parts. Lastly, a well-positioned kicker can reduce the dark current emitted by the SRF injector of the accelerator. Different designs for structures, deflecting the bunch in the beam line, have been simulated using CST Particle Studio. Here, no big difference to well-known strip line structures do exist. The next step is to design the supply electronics driving the kickers. As the ELBE accelerator runs at a high bunch repetition rate, the kicker has to keep up to this frequencies of up to 13 MHz. Hence, the high power levels needed for the operation may cause additional problems for the driver electronics. The poster is going to present the state of our development for all three tasks and our approaches to solve the corresponding challenges.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPME067

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MOPRI024

NEA-GaAs (Cs, O) Photocathodes for the ELBE SRF Gun

639

R. Xiang, A. Arnold, P.N. Lu, P. Michel, P. Murcek, J. Teichert, H. Vennekate
HZDR, Dresden, Germany

Funding: supported by the European Community under the FP7 programme (EuCARD-2, contract number 312453, and LA3NET, contract number 289191), and by the BMBF grant 05K12CR1.
At HZDR a preparation chamber for NEA-GaAs (Cs, O) has been built and commissioned. GaAs is the next photocathode material for the ELBE SRF gun, which has been successfully operated with Cs2Te layer in last years. GaAs At HZDR a preparation chamber for NEA-GaAs (Cs, O) has been built and tested. GaAs is the next photocathode material for the ELBE SRF gun, which has been successfully operated with Cs2Te photocathode in last years. GaAs photocathodes are advantageous because of their high quantum efficiency (QE) with visible light and the extensive experiences of their use in DC guns. Furthermore, GaAs photocathodes provide the possibility to realize a polarized SRF gun in the future. In this presentation we will introduce the new preparation system and the first results of the GaAs tests. The new transfer system under construction will be also presented.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRI024

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MOPRI025

Recent Improvement of Cs2Te Photocathodes at HZDR

642

R. Xiang, A. Arnold, P.N. Lu, P. Michel, P. Murcek, J. Teichert, H. Vennekate
HZDR, Dresden, Germany

Funding: Work supported by the European Community-Research Infrastructure Activity (EuCARD, contract number 227579), and the support of the German Federal Ministry of Education and Research grant 05 ES4BR1/8.
The SRF gun has been successfully operated for the radiation source ELBE at HZDR. To achieve higher current and lower beam emittance, a new niobium cavity with superconducting solenoid and a new 13 MHz laser have been recently developed. For this reason, better photocathodes with high quantum efficiency are urgently in demand. In this work we improve the present Cs2Te preparation system for cleaner environment and more precise stoichiometric control than before. A new mask is designed to prevent cesium pollution of the cathode body. Instead of Kapton only alumina ceramics are used for isolation, and the cathode plugs are degassed at higher temperature. New evaporators are installed and tested to obtain an accurate deposition rate. Furthermore, the cathode transfer system is thoroughly cleaned for a better vacuum condition.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-MOPRI025

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TUZA02

THz Facility at ELBE: A Versatile Test Facility for Electron Bunch Diagnostics on Quasi-CW Electron Beams

933

M. Gensch, B.W. Green, J. Hauser, S. Kovalev, M. Kuntzsch, U. Lehnert, P. Michel, R. Schurig
HZDR, Dresden, Germany
A. Al-Shemmary, V. B. Asgekar, T. Golz, H. Schlarb, N. Stojanovic, S. Vilcins
DESY, Hamburg, Germany
A.S. Fisher
SLAC, Menlo Park, California, USA
G. Geloni
XFEL. EU, Hamburg, Germany
A.-S. Müller, M. Schwarz
KIT, Karlsruhe, Germany
N.E. Neumann, D. Plettemeier
TU Dresden, Dresden, Germany

At the Helmholtz-Zentrum Dresden-Rossendorf near Dresden a quasi-cw low-energy electron linear accelerator based on superconducting radiofrequency technology is operated successfully for more than 10 years. The ELBE accelerator is driving several secondary radiation sources including 2 infrared free electron lasers. A new addition will be a THz facility that aims to make use of super-radiant THz radiation. In its final form the THz facility shall consist of one coherent diffraction radiator and one undulator source which provide high-field THz pulses at unprecedented repetition rates. While the medium term goal is to establish a unique user facility for nonlinear THz science, the THz sources are already used as a test facility for novel diagnostic techniques on quasi-cw electron beams. The progress of the developments is reported and an outlook into future challenges and opportunities is given.

Slides TUZA02 [3.041 MB]

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUZA02

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TUPRO044

Bunch Compression of the Low-energy ELBE Electron Beam for Super-radiant THz Sources

1123

U. Lehnert, P. Michel, R. Schurig
HZDR, Dresden, Germany
A.A. Aksoy
Ankara University, Accelerator Technologies Institute, Golbasi / Ankara, Turkey
P.E. Evtushenko
JLab, Newport News, Virginia, USA
J.M. Krämer
Danfysik A/S, Taastrup, Denmark

At the ELBE radiation source two super-radiant THz sources, a broad-band trasnsition/diffraction radiation source and a planar undulator narrow-band sourc are under commissioning. At present the facility is driven from the ELBE linac with a CW electron beam of 100kHz repetition rate and up to 100pC of bunch charge. With the upgraded SRF electron gun bunch charges up to 1nC will become available. For the beam energies in the 20-30 MeV range buch compression into the sub-200 fs range becomes a major challenge. We present beam dynamics calculation of the attempted bunch compression scheme as well as first measurements obtained during the commissioning.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-TUPRO044

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WEPRO113

Status of the Radiation Source ELBE Upgrade

2233

P. Michel, T.E. Cowan, U. Lehnert, U. Schramm
HZDR, Dresden, Germany

ELBE is based on a 40 MeV superconducting Electron Linac able to operate in CW mode and provides manifold secondary user beams. The suite of secondary beams include: two free electron lasers operating in the IR/THz regime; a fast neutron beam; a Bremsstrahlung gamma-ray beam; a low-energy positron beam; and patented single-electron test beams. The primary electron beam is also used for radiobiology research, or in interaction with ultra-intense PW-class lasers. Through 2014 ELBE will be upgraded to a Centre for High Power Radiation Sources. The ELBE beam current was increased to 1.6 mA by using novel solid state RF amplifiers. The concept also contains additional broad and narrow band coherent THz sources and the development of a 500 TW TiSa Laser and even a 1.5 PW diode pumped laser system. Laser plasma electron acceleration and proton acceleration experiments for medical applications are planned. Additionally, coupled electron laser beam experiments like Thomson scattering or injection of ELBE electron into the laser plasma will be done.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPRO113

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WEPME003

Two Years Experience with the Upgraded ELBE RF System Driven by 20kW Solid State Amplifier Blocks (SSPA)

2257

H. Büttig, A. Arnold, A. Büchner, M. Justus, M. Kuntzsch, U. Lehnert, P. Michel, R. Schurig, G.S. Staats, J. Teichert
HZDR, Dresden, Germany

Since January 2012 the Superconducting CW Linac ELBE is equipped and in permanent operation with four 20 kW Solid State Amplifier Blocks. The poster gives an overview on the design of the new RF system and the experience gained within the first two years of operation.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-WEPME003

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THPRO012

Wakefield-based Dechirper Structures for ELBE

2882

F. Reimann, U. van Rienen
Rostock University, Faculty of Computer Science and Electrical Engineering, Rostock, Germany
U. Lehnert, P. Michel
HZDR, Dresden, Germany

Funding: Federal Ministry of Education and Research
The efficient reduction of the pulse length and the energy width of electron beams plays a crucial role in the generation of short pulses in the range of sub-picoseconds at future light sources. At the radiation source ELBE in Dresden Rossendorf short pulses are required for coherent THz generation and laser-electron beam interaction experiments such as X-ray Thomson scattering. Energy dechirping can be carried out passively by wakefields generated when the electron beam passes through suitable structures, namely corrugated and dielectrically lined cylindrical pipes or dielectrically lined rectangular waveguides (*,**,***). All structures offer the possibility to tune the resulting wakefield and therefore the resulting energy chirp through a variation of purely geometrical or material parameters. In this paper we present a semi-analytical approach to determine the wakefield in dielectrically lined rectangular waveguide, starting with the expression of the electric field in terms of the structure's eigenmodes.
* Bane, Stupakov, SLAC-PUB-14925 (2012)
** Mosnier, Novokhatski, in: Proceedings of PAC97, Vancouver, Canada, 1997
*** Antipov et al., in: Proceedings of IPAC2012, New Orleans, USA, 2012

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPRO012

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THPRO055

Electron Beam Final Focus System for Thomson Scattering at ELBE

2995

J.M. Krämer, F. Bødker, A. Baurichter, M. Budde
Danfysik A/S, Taastrup, Denmark
A. Irman, U. Schramm
Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Institute of Radiation Physics, Dresden, Germany
U. Lehnert, P. Michel
HZDR, Dresden, Germany

Funding: This work is part of LA3NET and funded by European Commission under Grant Agreement Number 289191.
The design of an electron beam Final Focus System (FFS) aiming for high-flux laser-Thomson backscattering x-ray sources at ELBE* is presented. A telescope system consisting of four permanent magnet based quadrupoles was found to have significantly less chromatic aberrations than a quadrupole triplet. This allows sub-ps electron beam focusing to match the laser spot size at the interaction point. Focusing properties like the position of the focal plane and the spot size are retained for electron beam energies between 20 and 30 MeV by adjusting the position of the quadrupoles individually on a motorized stage. Since the electron beam is chirped for bunch compression upstream, the rms energy spread is increased to one or two percent and second order chromatic effects must be taken into account. For an emittance of 13 pi mm mrad, we predict rms spot sizes of about 40 um and divergences of about 15 mrad. We also present the design of the permanent magnet quadrupoles to be used for the FFS. Ferromagnetic poles ensure a high field quality and adjustable shunts allow for fine adjustment of the field strength and compensation of deviations in the permanent magnet material.
*A. Jochmann et al., Phys. Rev. Lett. 111 (2013) 114803

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THPME109

EOS at CW Beam Operation at ELBE

3492

Ch. Schneider, M. Gensch, M. Kuntzsch, P. Michel, W. Seidel
HZDR, Dresden, Germany
P.E. Evtushenko
JLab, Newport News, Virginia, USA
Ç. Kaya
Ankara University, Accelerator Technologies Institute, Golbasi / Ankara, Turkey
A. Shemmary, N. Stojanovic
DESY, Hamburg, Germany

The ELBE accelerator is a super conduction electron cw machine located at the Helmholtz Center Dresden Rossendorf Germany with 1 mA current, now tested for up to 2 mA. Besides other important diagnostics for setting up the machine for user beam time and further improvement of the machine – a THz source is momentary under commissioning – a EOS measuring station for bunch length measurements is locate right behind the second super conducting Linac. Measuring with a crystal in the vicinity of an up to 2 mA cw beam implies higher beam loss and also higher radiation exposure of the crystal and hence also a safety risk for the UHV conditions of the super conducting cavities in the case of crystal damage. Therefore the EOS measuring principle is adapted to larger measuring distances and also for beam requirements with lower bunch charge at ELBE. A description of the setup, considerations of special boundary conditions and as well results for 13 MHz cw beam operation are presented.

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reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2014-THPME109

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