IPAC2016 - List of Authors (Hug, F.)

Paper	Title	Page
MOPMB012	A High-Energy-Scrapersystem for the S-DALINAC Extraction - Design and Installation	101
	L.E. Jürgensen, T. Bahlo, C. Burandt, T. Kürzeder, N. Pietralla, S. Weih, J. Wissmann TU Darmstadt, Darmstadt, Germany F. Hug IKP, Mainz, Germany
	Funding: *Funded by Deutsche Forschungsgemeinschaft under grant No. SFB 634 The superconducting Darmstadt linear electron accelerator (S-DALINAC) of the Institute for Nuclear Physics at Technische Universität Darmstadt delivers electron beams in cw-mode with energies up to 130 MeV. The accelerator consists of a 10-MeV injector and a 30-MeV main linac where superconducting 3-GHz microwave cavities are operated at a temperature of 2 K for beam acceleration. With three recirculation beamlines the main linac can be used up to four times. To improve the energy spread and the energy stability of the beam a new scrapersystem has been developed and installed. It changes the extraction beam line into a dispersion-conserving chicane consisting of four dipole magnets and three scrapers. The system includes scraping of x- and y-halo in two positions as well as improving and stabilizing energy spread on a dispersive part. We will present the design of the system and report on its installation into the accelerator complex.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMB012
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPOR025	Beam Break-up Measurements at the Recirculating Electron Accelerator S-DALINAC	1714
	T. Kürzeder, M. Arnold, L.E. Jürgensen, J. Pforr, N. Pietralla TU Darmstadt, Darmstadt, Germany F. Hug IKP, Mainz, Germany
	Funding: Supported by the German Federal Ministry for Education and Research (BMBF) under Grant No. 05K13RDA Beam break-up (BBU) instability is an important limitation to the current which can be accelerated in a superconducting linac. In particular recirculating machines and Energy Recovery Linacs have to deal with that problem. Therefore, it is important to find strategies for increasing the threshold currents of these machines. The superconducting accelerator S-DALINAC at the Technische Universität Darmstadt provides electron beams in c.w. for nuclear physics experiments since 1991. It consists of a 10 MeV injector and a 40 MeV main linac where two and eight 20-cell elliptical 3-GHz cavities are operated in a liquid helium bath at 2 K. Using two recirculation beam lines the main accelerator can be used up to 3 times. Operational experiences have shown that the design-beam current of 20 μA could not be reached. One reason is the occurrence of BBU. We will report on measurements of the threshold current at various energy settings of the S-DALINAC. The results of a first test to increase the BBU limit by using skew quadrupole magnets in the first recirculation beam line will be presented.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOR025
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPOR026	Final Design and Status of the Third Recirculation for the S-DALINAC*	1717
	M. Arnold, T. Kürzeder, N. Pietralla TU Darmstadt, Darmstadt, Germany F. Hug IKP, Mainz, Germany
	Funding: *Work supported by DFG through CRC 634 and RTG 2128 Since 1991 the twice-recirculating superconducting accelerator S-DALINAC is providing electron beams for nuclear physics experiments. Due to a reduced quality factor of its cavities in comparison to their design values it was not possible to operate the accelerator with its maximum design energy of 130 MeV in cw mode. To provide electron beams of this energy in the future it was decided to add one recirculation beam line in order to use the main linac four times, operating the cavities on decreased accelerating gradients. The necessary modifications consist of several different aspects: A new beamline needs to be installed and other pre-existing beam line sections have to be modified for matching new boundary conditions. These new conditions are mainly a result of beam dynamics simulations and of the design of a new separation dipole magnet, which will bend the different beams energy-dependent in the various recirculation beam lines. We will present the implemented design and give a status report on the project.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOR026
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPMB009	Status of the Superconducting Cryomodules and Cryogenic System for the Mainz Energy-recovering Superconducting Accelerator MESA	2134
	T. Stengler, K. Aulenbacher, F. Hug, D. Simon, P. Weber IKP, Mainz, Germany F. Schlander ESS, Lund, Sweden N. Wiehl Johannes Gutenberg University Mainz, Institut of Nuclear Chemistry, Mainz, Germany
	Funding: Work supported by the German Research Foundation (DFG) under the Cluster of Excellence "PRISMA" SRF and the cryogenic system are mandatory for the operation of MESA at the Institut für Kernphysik at Johannes Gutenberg-Universität Mainz. The cryomodule production project is running for one year right now and the recent developments and measurements are presented. Further on the cryogenic concept required for the operation of MESA will be discussed.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMB009
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPMB004	Improving Energy Spread and Stability of a Recirculating Few-turn Linac	3222
	F. Hug IKP, Mainz, Germany M. Arnold, T. Kürzeder, N. Pietralla TU Darmstadt, Darmstadt, Germany R.G. Eichhorn Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: Supported by the DFG through CRC 634, RTG 2128 and PRISMA cluster of excellence A non-isochronous recirculation scheme which helps cancelling out errors coming from the RF-jitters in a recirculating linac will be presented. Non-isochronous recirculation is the common operation mode for synchrotrons or microtrons. In such a scheme the recirculation arcs provide a non-zero longitudinal dispersion, while the particle bunches are accelerated at a certain phase off-crest with respect to the maximum of the accelerating field. In few-turn linacs and microtrons such beam dynamics can be used to reduce the energy spread. To do so the longitudinal phase advance needs to be set to a half-integer number of oscillations in phase space. Then errors from linac RF-systems cancel out and the energy spread remains closely to the value at injection. In addition to the improved energy spread the beam stability of few-turn recirculators can be increased as well using such a system. We will present operational experience with the non-isochronous recirculation system of the twice recirculating superconducting accelerator S-DALINAC operated at TU Darmstadt including beam-dynamics calculations and measurements of the energy spread.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMB004
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPMY024	Upgrade of a UHV Furnace for 1700 C Heat Treatment and Processing of Niobium Samples	3709
	J. Conrad, L. Alff, R. Grewe, T. Kürzeder, M. Major, N. Pietralla TU Darmstadt, Darmstadt, Germany F. Hug IKP, Mainz, Germany S.T. Sievers MIT, Marburg, Germany
	Funding: Supported by the German Federal Ministry for Education and Research (BMBF) under Grant No. 05H15RDRBA In 2005 a high temperature vacuum furnace was put into operation at the Institute for Nuclear Physics at the Technische Universität Darmstadt. It has been designed for firing pure Niobium at temperatures of up to 1870 C. Until now several Nb cavities have been heat treated at 850 C with a proven record of success. The current focus of research in improving the superconductive characteristics of accelerator cavities is on new materials such as Nb3Sn or NbN or on the doping of Nb surfaces with nitrogen, so called N2-Doping. The surface preparations generally take place at temperatures of not more than 1000 C. To study phenomena that occur at higher temperatures, like the formation of delta-phase NbN at 1300 to 1700 C, it is planned to refurbish the UHV furnace and use it for corresponding studies. We will report on the design of a new annealing pot and a sample holder and give a review on our first experiences with the upgraded furnace.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMY024
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

A High-Energy-Scrapersystem for the S-DALINAC Extraction - Design and Installation

101

L.E. Jürgensen, T. Bahlo, C. Burandt, T. Kürzeder, N. Pietralla, S. Weih, J. Wissmann
TU Darmstadt, Darmstadt, Germany
F. Hug
IKP, Mainz, Germany

Funding: *Funded by Deutsche Forschungsgemeinschaft under grant No. SFB 634
The superconducting Darmstadt linear electron accelerator (S-DALINAC) of the Institute for Nuclear Physics at Technische Universität Darmstadt delivers electron beams in cw-mode with energies up to 130 MeV. The accelerator consists of a 10-MeV injector and a 30-MeV main linac where superconducting 3-GHz microwave cavities are operated at a temperature of 2 K for beam acceleration. With three recirculation beamlines the main linac can be used up to four times. To improve the energy spread and the energy stability of the beam a new scrapersystem has been developed and installed. It changes the extraction beam line into a dispersion-conserving chicane consisting of four dipole magnets and three scrapers. The system includes scraping of x- and y-halo in two positions as well as improving and stabilizing energy spread on a dispersive part. We will present the design of the system and report on its installation into the accelerator complex.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMB012

Export •

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

TUPOR025

Beam Break-up Measurements at the Recirculating Electron Accelerator S-DALINAC

1714

T. Kürzeder, M. Arnold, L.E. Jürgensen, J. Pforr, N. Pietralla
TU Darmstadt, Darmstadt, Germany
F. Hug
IKP, Mainz, Germany

Funding: Supported by the German Federal Ministry for Education and Research (BMBF) under Grant No. 05K13RDA
Beam break-up (BBU) instability is an important limitation to the current which can be accelerated in a superconducting linac. In particular recirculating machines and Energy Recovery Linacs have to deal with that problem. Therefore, it is important to find strategies for increasing the threshold currents of these machines. The superconducting accelerator S-DALINAC at the Technische Universität Darmstadt provides electron beams in c.w. for nuclear physics experiments since 1991. It consists of a 10 MeV injector and a 40 MeV main linac where two and eight 20-cell elliptical 3-GHz cavities are operated in a liquid helium bath at 2 K. Using two recirculation beam lines the main accelerator can be used up to 3 times. Operational experiences have shown that the design-beam current of 20 μA could not be reached. One reason is the occurrence of BBU. We will report on measurements of the threshold current at various energy settings of the S-DALINAC. The results of a first test to increase the BBU limit by using skew quadrupole magnets in the first recirculation beam line will be presented.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOR025

Export •

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

TUPOR026

Final Design and Status of the Third Recirculation for the S-DALINAC*

1717

M. Arnold, T. Kürzeder, N. Pietralla
TU Darmstadt, Darmstadt, Germany
F. Hug
IKP, Mainz, Germany

Funding: *Work supported by DFG through CRC 634 and RTG 2128
Since 1991 the twice-recirculating superconducting accelerator S-DALINAC is providing electron beams for nuclear physics experiments. Due to a reduced quality factor of its cavities in comparison to their design values it was not possible to operate the accelerator with its maximum design energy of 130 MeV in cw mode. To provide electron beams of this energy in the future it was decided to add one recirculation beam line in order to use the main linac four times, operating the cavities on decreased accelerating gradients. The necessary modifications consist of several different aspects: A new beamline needs to be installed and other pre-existing beam line sections have to be modified for matching new boundary conditions. These new conditions are mainly a result of beam dynamics simulations and of the design of a new separation dipole magnet, which will bend the different beams energy-dependent in the various recirculation beam lines. We will present the implemented design and give a status report on the project.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOR026

Export •

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

WEPMB009

Status of the Superconducting Cryomodules and Cryogenic System for the Mainz Energy-recovering Superconducting Accelerator MESA

2134

T. Stengler, K. Aulenbacher, F. Hug, D. Simon, P. Weber
IKP, Mainz, Germany
F. Schlander
ESS, Lund, Sweden
N. Wiehl
Johannes Gutenberg University Mainz, Institut of Nuclear Chemistry, Mainz, Germany

Funding: Work supported by the German Research Foundation (DFG) under the Cluster of Excellence "PRISMA"
SRF and the cryogenic system are mandatory for the operation of MESA at the Institut für Kernphysik at Johannes Gutenberg-Universität Mainz. The cryomodule production project is running for one year right now and the recent developments and measurements are presented. Further on the cryogenic concept required for the operation of MESA will be discussed.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMB009

Export •

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

THPMB004

Improving Energy Spread and Stability of a Recirculating Few-turn Linac

3222

F. Hug
IKP, Mainz, Germany
M. Arnold, T. Kürzeder, N. Pietralla
TU Darmstadt, Darmstadt, Germany
R.G. Eichhorn
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: Supported by the DFG through CRC 634, RTG 2128 and PRISMA cluster of excellence
A non-isochronous recirculation scheme which helps cancelling out errors coming from the RF-jitters in a recirculating linac will be presented. Non-isochronous recirculation is the common operation mode for synchrotrons or microtrons. In such a scheme the recirculation arcs provide a non-zero longitudinal dispersion, while the particle bunches are accelerated at a certain phase off-crest with respect to the maximum of the accelerating field. In few-turn linacs and microtrons such beam dynamics can be used to reduce the energy spread. To do so the longitudinal phase advance needs to be set to a half-integer number of oscillations in phase space. Then errors from linac RF-systems cancel out and the energy spread remains closely to the value at injection. In addition to the improved energy spread the beam stability of few-turn recirculators can be increased as well using such a system. We will present operational experience with the non-isochronous recirculation system of the twice recirculating superconducting accelerator S-DALINAC operated at TU Darmstadt including beam-dynamics calculations and measurements of the energy spread.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMB004

Export •

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

THPMY024

Upgrade of a UHV Furnace for 1700 C Heat Treatment and Processing of Niobium Samples

3709

J. Conrad, L. Alff, R. Grewe, T. Kürzeder, M. Major, N. Pietralla
TU Darmstadt, Darmstadt, Germany
F. Hug
IKP, Mainz, Germany
S.T. Sievers
MIT, Marburg, Germany

Funding: Supported by the German Federal Ministry for Education and Research (BMBF) under Grant No. 05H15RDRBA
In 2005 a high temperature vacuum furnace was put into operation at the Institute for Nuclear Physics at the Technische Universität Darmstadt. It has been designed for firing pure Niobium at temperatures of up to 1870 C. Until now several Nb cavities have been heat treated at 850 C with a proven record of success. The current focus of research in improving the superconductive characteristics of accelerator cavities is on new materials such as Nb3Sn or NbN or on the doping of Nb surfaces with nitrogen, so called N2-Doping. The surface preparations generally take place at temperatures of not more than 1000 C. To study phenomena that occur at higher temperatures, like the formation of delta-phase NbN at 1300 to 1700 C, it is planned to refurbish the UHV furnace and use it for corresponding studies. We will report on the design of a new annealing pot and a sample holder and give a review on our first experiences with the upgraded furnace.

DOI •

reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPMY024

Export •

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