IPAC2022 - List of Authors (Hillert, W.)

Paper	Title	Page
TUPOPT023	Undulator Tapering Studies of an Echo-Enabled Harmonic Generation Based Free-Electron Laser	1047
SUSPMF010	use link to see paper's listing under its alternate paper code
	F. Pannek, W. Hillert University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany S. Ackermann, E. Ferrari, L. Schaper DESY, Hamburg, Germany
	The free-electron laser (FEL) user facility FLASH at DESY is currently undergoing an upgrade which involves the transformation of one of its beamlines to allow for external seeding via so-called Echo-Enabled Harmonic Generation (EEHG). With this seeding technique it will be possible to provide stable, longitudinal coherent and intense radiation in the XUV and soft X-ray regime at high repetition rate. To ensure an efficient FEL amplification process, sustainable energy exchange between the electrons and the electromagnetic field in the undulator is mandatory. Adequate adjustment of the undulator strength along the beamline allows to compensate for electron energy loss and to preserve the resonance condition. The impact of this undulator tapering on the temporal and spectral characteristics on the EEHG FEL radiation at 4 nm is investigated by means of numerical simulations performed with the FEL code GENESIS 1.3, version 4. Different tapering methods are examined and it is shown that specific tapering of the undulator strength allows to exceed the FEL saturation power while maintaining a clear temporal and spectral shape of the FEL pulse.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOPT023
About •	Received ※ 08 June 2022 — Revised ※ 15 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 27 June 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPOTK010	Nitric Acid Soaking after Imperfect Furnace Treatments	1211
SUSPMF105	use link to see paper's listing under its alternate paper code
	R. Ghanbari, A. Dangwal Pandey DESY, Hamburg, Germany C. Bate University of Hamburg, Hamburg, Germany W. Hillert, M. Wenskat University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
	Annealings of niobium cavities in UHV or nitrogen atmospheres are crucial for the performance in the later cryogenic tests and operation. Recovery methods for imperfect annealing conditions have been discussed, and a more recent proposal, the so-called "nitric acid soak" has been studied here in detail. It shows surprising recovery potential, albeit the unclear origin of this improvement. We present our investigation on the several potential origins. For this, we used SEM, SIMS and XPS measurements of niobium samples to study the surface morphology and contaminations. We can reject the favored hypothesis on the origin of the improvement, and propose an alternative origin.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOTK010
About •	Received ※ 10 June 2022 — Revised ※ 12 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 18 June 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPOTK011	Commissioning of a New Magnetometric Mapping System for SRF Cavity Performance Tests	1215
SUSPMF106	use link to see paper's listing under its alternate paper code
	J.C. Wolff, J. Eschke, A. Gössel, D. Reschke, L. Steder, L. Trelle DESY, Hamburg, Germany W. Hillert University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
	Funding: This work was supported by the Helmholtz Association within the topic Accelerator Research and Development (ARD) of the Matter and Technologies (MT) Program. Magnetic flux trapped in the niobium bulk material of superconducting radio frequency (SRF) cavities degrades their quality factor and the accelerating gradient. The sensitivity for flux trapping is mainly determined by the treatment and the geometry of the cavity as well as the niobium grain size and orientation. To potentially improve the flux expulsion characteristics of SRF cavities and hence the efficiency of future accelerator facilities, further studies of the trapping behavior are essential. For this purpose a magnetometric mapping system to monitor the magnetic flux along the outer cavity surface of 1.3 GHz TESLA-Type single-cell SRF cavities has been developed and is currently in the commissioning phase at DESY. Contrary to similar approaches, this system digitizes the sensor signals already inside of the cryostat to extensively reduce the number of required cable feedthroughs. Furthermore, the signal-to-noise ratio (SNR) and consequently the measuring sensitivity can be enhanced by shorter analog signal lines, less thermal noise and the Mu-metal shielding of the cryostat. In this contribution test results gained by a prototype of the mapping system are presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOTK011
About •	Received ※ 10 June 2022 — Revised ※ 16 June 2022 — Accepted ※ 17 June 2022 — Issue date ※ 29 June 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPOTK012	Nitrogen Infusion Sample R&D at DESY	1219
	C. Bate University of Hamburg, Hamburg, Germany A. Ermakov, D. Reschke, J. Schaffran DESY, Hamburg, Germany W. Hillert, M. Wenskat University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
	Funding: This work was supported by the Helmholtz Association within the topic Accelerator Research and Development (ARD) of the Matter and Technologies (MT) Program. Many accelerator projects such as the ILC would benefit from cavities with reduced surface resistance (high Q-values) while maintaining a high accelerating gradient. A possible way to meet the requirements is the so-called nitrogen-infusion procedure on Niobium cavities. However, a fundamental understanding and a theoretical model of this method are still missing. One important parameter is the residual resistance ratio (RRR) which is related to the impurity content of the material. We report the investigated RRR on samples in a wide temperature range in a vacuum and under a nitrogen atmosphere. This comparison made it possible to make statements about the differences in the concentration of nitrogen by varying the temperature. The samples are pure cavity-grade niobium and treated in the same manner as cavities. For this purpose, a small furnace dedicated to sample treatment was set up to change and explore the parameter space of the infusion recipe. Care was taken to achieve the highest level of purity possible in the furnace and in a pressure range of 1.0·10^-8 mbar in order to meet the high requirements of nitrogen infusion.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOTK012
About •	Received ※ 08 June 2022 — Revised ※ 14 June 2022 — Accepted ※ 15 June 2022 — Issue date ※ 01 July 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPOTK013	PEALD SIS Studies for SRF Cavities	1222
SUSPMF107	use link to see paper's listing under its alternate paper code
	I. González Díaz-Palacio, R.H. Blick, A. Stierle, R. Zierold University of Hamburg, Hamburg, Germany W. Hillert, M. Wenskat University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany A. Jeromin DESY Nanolab, FS-NL, Hamburg, Germany T.F. Keller, N. Krupka, M. Wenskat DESY, Hamburg, Germany
	Recent technological advances and material treatments have pushed Nb SRF cavities to their maximum RF performance. A novel approach for overcoming this limitation, which takes advantage of RF field only penetrates into the superconductor at a certain distance called London penetration depth, is nano-structuring multilayers with PEALD (plasma-enhanced atomic layer deposition). SIS (superconductor-insulator-superconductor) multilayers provide magnetic screening of the bulk Nb cavity, increasing the field at which the vortex penetration starts, and higher quality factor. ALD is closely related to chemical vapor deposition and bases on sequential self-limit gas-solid surface reactions facilitating conformal coatings with sub-nm precision even on complex substrates such as the interior of a cavity. As a preliminary study for SIS SRF cavities, we investigated the AlN-NbTiN/NbN multilayers grown by PEALD. Different compositions, thicknesses, and post-deposition thermal treatments have been investigated. The characterization results of superconducting properties, elemental composition, crystallinity, and cross-section are shown in this contribution.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOTK013
About •	Received ※ 09 June 2022 — Revised ※ 14 June 2022 — Accepted ※ 15 June 2022 — Issue date ※ 27 June 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPOMS024	Sensitivity of EEHG Simulations to Dynamic Beam Parameters	1463
	D. Samoilenko, W. Hillert, F. Pannek University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany S. Ackermann, E. Ferrari, N.S. Mirian, P. Niknejadi, G. Paraskaki, L. Schaper DESY, Hamburg, Germany F. Curbis, M.A. Pop, S. Werin MAX IV Laboratory, Lund University, Lund, Sweden
	Currently, the Free electron laser user facility FLASH at DESY is undergoing a significant upgrade involving the complete transformation of one of its beamlines to allow external seeding. With the Echo-Enabled Harmonic Generation (EEHG) seeding method, we aim for the generation of fully coherent XUV and soft X-ray pulses at wavelengths down to 4 nm. The generated FEL radiation is sensitive to various electron beam properties, e.g., its energy profile imprinted either deliberately or by collective effects such as Coherent Synchrotron Radiation (CSR). In dedicated particle tracking simulations, one usually makes certain assumptions concerning the beam properties and the collective effects to simplify implementation and analysis. Here, we estimate the influence of some of the common assumptions made in EEHG simulations on the properties of the output FEL radiation, using the example of FLASH and its proposed seeding beamline. We conclude that the inherent properties of the FLASH1 beam, namely the negatively chirped energy profile, has dominant effect on the spectral intensity profile of the radiators output compare to that of the CSR induced chirp.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOMS024
About •	Received ※ 20 May 2022 — Revised ※ 12 June 2022 — Accepted ※ 24 June 2022 — Issue date ※ 29 June 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUPOMS044	Dielectric Loaded THz Waveguide Experimentally Optimized by Dispersion Measurements	1526
SUSPMF027	use link to see paper's listing under its alternate paper code
	M.J. Kellermeier, R.W. Aßmann, K. Flöttmann, F. Lemery DESY, Hamburg, Germany R.W. Aßmann LNF-INFN, Frascati, Italy W. Hillert University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
	Emerging high power THz sources pave the road for THz- driven acceleration of ultra-short bunches, and enable their manipulation for diagnostic purposes. Due to the small feature sizes of THz-guiding devices new methods are necessary for their electromagnetic characterization. A new technique has recently been developed which characterizes THz waveguides with respect to their dispersion relations and attenuation. Here, the method is applied to circular waveguides, partially filled with polymer capillaries of different thicknesses, to find a suitable size for THz driven streaking at 287 GHz. Further, rough 3d-printed metallic waveguides are measured to study the effect of roughness on attenuation and phase constant. In general, additive manufacturing techniques show promise for advanced integrated designs of THz driven structures.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOMS044
About •	Received ※ 05 June 2022 — Revised ※ 12 June 2022 — Accepted ※ 15 June 2022 — Issue date ※ 28 June 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THOXSP3	Path to High Repetition Rate Seeding: Combining High Gain Harmonic Generation with an Optical Klystron	2411
	G. Paraskaki, E. Ferrari, L. Schaper, E. Schneidmiller DESY, Hamburg, Germany E. Allaria Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy W. Hillert University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
	External seeding in combination with harmonic generation has become a hot topic in the field of high gain free-electron lasers (FELs) since it allows delivery of superior FEL radiation characterized by, for example, full coherence and unprecedented shot-to-shot stability. At low repetition rate machines operating at few 10 Hz, novel experiments have been realized already, however, at superconducting machines, current laser technology does not support exploiting the full repetition rate available. One way to overcome this problem is to reduce the requirements in seed laser power: here, an optical klystron based high gain harmonic generation (HGHG) setup is proposed to reduce the laser peak power requirements by orders of magnitude, enabling operation at drastically increased repetition rates. We report simulation results based on the seeded beamline concept of the FLASH2020+ project. Among other topics, the effect of a linear electron beam energy chirp on this setup will be discussed.
	Slides THOXSP3 [1.502 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THOXSP3
About •	Received ※ 08 June 2022 — Revised ※ 14 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 27 June 2022
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THOYGD2	Experimental Slice Emittance Reduction at PITZ Using Laser Pulse Shaping
	R. Niemczyk, Z. Aboulbanine, G.D. Adhikari, N. Aftab, P. Boonpornprasert, G.Z. Georgiev, J. Good, M. Groß, C. Koschitzki, X.-K. Li, O. Lishilin, D. Melkumyan, S.K. Mohanty, A. Oppelt, H.J. Qian, H. Shaker, G. Shu, F. Stephan, T. Weilbach DESY Zeuthen, Zeuthen, Germany M.E. Castro Carballo, M. Krasilnikov, G. Vashchenko DESY, Hamburg, Germany W. Hillert University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
	Free-electron lasers in the X-ray regime require a high-brightness electron beam, i.e. an electron beam with high current and low transverse emittance. At the Photo Injector Test facility at DESY in Zeuthen (PITZ) high-brightness electron sources are optimized for the use at FLASH and European XFEL. A low transverse emittance of the electron beam’s central part, which is assumed to be the lasing slices, is of particular interest for the efficient FEL operation. Over the past years a slice emittance measurement scheme has been developed at PITZ which employs an rf deflector and additional quadrupole magnets along the beamline to the standard measurement procedure for the projected emittance (single-slit scan). It allows measuring the slice emittance in a high-brightness photo injector. Transversely flat-top shaped laser pulses of different temporal distributions (Gaussian and flat-top) have been used to emit electrons, as well as transversely-truncated Gaussian laser pulses with temporal Gaussian shape. The paper shows that the lowest slice emittance in the injector is reached with a temporal flattop shape, or when using a transversely-truncated Gaussian shape.
	Slides THOYGD2 [2.045 MB]
Cite •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

TUPOPT023

Undulator Tapering Studies of an Echo-Enabled Harmonic Generation Based Free-Electron Laser

1047

SUSPMF010

use link to see paper's listing under its alternate paper code

F. Pannek, W. Hillert
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
S. Ackermann, E. Ferrari, L. Schaper
DESY, Hamburg, Germany

The free-electron laser (FEL) user facility FLASH at DESY is currently undergoing an upgrade which involves the transformation of one of its beamlines to allow for external seeding via so-called Echo-Enabled Harmonic Generation (EEHG). With this seeding technique it will be possible to provide stable, longitudinal coherent and intense radiation in the XUV and soft X-ray regime at high repetition rate. To ensure an efficient FEL amplification process, sustainable energy exchange between the electrons and the electromagnetic field in the undulator is mandatory. Adequate adjustment of the undulator strength along the beamline allows to compensate for electron energy loss and to preserve the resonance condition. The impact of this undulator tapering on the temporal and spectral characteristics on the EEHG FEL radiation at 4 nm is investigated by means of numerical simulations performed with the FEL code GENESIS 1.3, version 4. Different tapering methods are examined and it is shown that specific tapering of the undulator strength allows to exceed the FEL saturation power while maintaining a clear temporal and spectral shape of the FEL pulse.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOPT023

About •

Received ※ 08 June 2022 — Revised ※ 15 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 27 June 2022

Cite •

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

TUPOTK010

Nitric Acid Soaking after Imperfect Furnace Treatments

1211

SUSPMF105

use link to see paper's listing under its alternate paper code

R. Ghanbari, A. Dangwal Pandey
DESY, Hamburg, Germany
C. Bate
University of Hamburg, Hamburg, Germany
W. Hillert, M. Wenskat
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany

Annealings of niobium cavities in UHV or nitrogen atmospheres are crucial for the performance in the later cryogenic tests and operation. Recovery methods for imperfect annealing conditions have been discussed, and a more recent proposal, the so-called "nitric acid soak" has been studied here in detail. It shows surprising recovery potential, albeit the unclear origin of this improvement. We present our investigation on the several potential origins. For this, we used SEM, SIMS and XPS measurements of niobium samples to study the surface morphology and contaminations. We can reject the favored hypothesis on the origin of the improvement, and propose an alternative origin.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOTK010

About •

Received ※ 10 June 2022 — Revised ※ 12 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 18 June 2022

Cite •

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

TUPOTK011

Commissioning of a New Magnetometric Mapping System for SRF Cavity Performance Tests

1215

SUSPMF106

use link to see paper's listing under its alternate paper code

J.C. Wolff, J. Eschke, A. Gössel, D. Reschke, L. Steder, L. Trelle
DESY, Hamburg, Germany
W. Hillert
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany

Funding: This work was supported by the Helmholtz Association within the topic Accelerator Research and Development (ARD) of the Matter and Technologies (MT) Program.
Magnetic flux trapped in the niobium bulk material of superconducting radio frequency (SRF) cavities degrades their quality factor and the accelerating gradient. The sensitivity for flux trapping is mainly determined by the treatment and the geometry of the cavity as well as the niobium grain size and orientation. To potentially improve the flux expulsion characteristics of SRF cavities and hence the efficiency of future accelerator facilities, further studies of the trapping behavior are essential. For this purpose a magnetometric mapping system to monitor the magnetic flux along the outer cavity surface of 1.3 GHz TESLA-Type single-cell SRF cavities has been developed and is currently in the commissioning phase at DESY. Contrary to similar approaches, this system digitizes the sensor signals already inside of the cryostat to extensively reduce the number of required cable feedthroughs. Furthermore, the signal-to-noise ratio (SNR) and consequently the measuring sensitivity can be enhanced by shorter analog signal lines, less thermal noise and the Mu-metal shielding of the cryostat. In this contribution test results gained by a prototype of the mapping system are presented.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOTK011

About •

Received ※ 10 June 2022 — Revised ※ 16 June 2022 — Accepted ※ 17 June 2022 — Issue date ※ 29 June 2022

Cite •

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

TUPOTK012

Nitrogen Infusion Sample R&D at DESY

1219

C. Bate
University of Hamburg, Hamburg, Germany
A. Ermakov, D. Reschke, J. Schaffran
DESY, Hamburg, Germany
W. Hillert, M. Wenskat
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany

Funding: This work was supported by the Helmholtz Association within the topic Accelerator Research and Development (ARD) of the Matter and Technologies (MT) Program.
Many accelerator projects such as the ILC would benefit from cavities with reduced surface resistance (high Q-values) while maintaining a high accelerating gradient. A possible way to meet the requirements is the so-called nitrogen-infusion procedure on Niobium cavities. However, a fundamental understanding and a theoretical model of this method are still missing. One important parameter is the residual resistance ratio (RRR) which is related to the impurity content of the material. We report the investigated RRR on samples in a wide temperature range in a vacuum and under a nitrogen atmosphere. This comparison made it possible to make statements about the differences in the concentration of nitrogen by varying the temperature. The samples are pure cavity-grade niobium and treated in the same manner as cavities. For this purpose, a small furnace dedicated to sample treatment was set up to change and explore the parameter space of the infusion recipe. Care was taken to achieve the highest level of purity possible in the furnace and in a pressure range of 1.0·10^-8 mbar in order to meet the high requirements of nitrogen infusion.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOTK012

About •

Received ※ 08 June 2022 — Revised ※ 14 June 2022 — Accepted ※ 15 June 2022 — Issue date ※ 01 July 2022

Cite •

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

TUPOTK013

PEALD SIS Studies for SRF Cavities

1222

SUSPMF107

use link to see paper's listing under its alternate paper code

I. González Díaz-Palacio, R.H. Blick, A. Stierle, R. Zierold
University of Hamburg, Hamburg, Germany
W. Hillert, M. Wenskat
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
A. Jeromin
DESY Nanolab, FS-NL, Hamburg, Germany
T.F. Keller, N. Krupka, M. Wenskat
DESY, Hamburg, Germany

Recent technological advances and material treatments have pushed Nb SRF cavities to their maximum RF performance. A novel approach for overcoming this limitation, which takes advantage of RF field only penetrates into the superconductor at a certain distance called London penetration depth, is nano-structuring multilayers with PEALD (plasma-enhanced atomic layer deposition). SIS (superconductor-insulator-superconductor) multilayers provide magnetic screening of the bulk Nb cavity, increasing the field at which the vortex penetration starts, and higher quality factor. ALD is closely related to chemical vapor deposition and bases on sequential self-limit gas-solid surface reactions facilitating conformal coatings with sub-nm precision even on complex substrates such as the interior of a cavity. As a preliminary study for SIS SRF cavities, we investigated the AlN-NbTiN/NbN multilayers grown by PEALD. Different compositions, thicknesses, and post-deposition thermal treatments have been investigated. The characterization results of superconducting properties, elemental composition, crystallinity, and cross-section are shown in this contribution.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOTK013

About •

Received ※ 09 June 2022 — Revised ※ 14 June 2022 — Accepted ※ 15 June 2022 — Issue date ※ 27 June 2022

Cite •

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

TUPOMS024

Sensitivity of EEHG Simulations to Dynamic Beam Parameters

1463

D. Samoilenko, W. Hillert, F. Pannek
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany
S. Ackermann, E. Ferrari, N.S. Mirian, P. Niknejadi, G. Paraskaki, L. Schaper
DESY, Hamburg, Germany
F. Curbis, M.A. Pop, S. Werin
MAX IV Laboratory, Lund University, Lund, Sweden

Currently, the Free electron laser user facility FLASH at DESY is undergoing a significant upgrade involving the complete transformation of one of its beamlines to allow external seeding. With the Echo-Enabled Harmonic Generation (EEHG) seeding method, we aim for the generation of fully coherent XUV and soft X-ray pulses at wavelengths down to 4 nm. The generated FEL radiation is sensitive to various electron beam properties, e.g., its energy profile imprinted either deliberately or by collective effects such as Coherent Synchrotron Radiation (CSR). In dedicated particle tracking simulations, one usually makes certain assumptions concerning the beam properties and the collective effects to simplify implementation and analysis. Here, we estimate the influence of some of the common assumptions made in EEHG simulations on the properties of the output FEL radiation, using the example of FLASH and its proposed seeding beamline. We conclude that the inherent properties of the FLASH1 beam, namely the negatively chirped energy profile, has dominant effect on the spectral intensity profile of the radiators output compare to that of the CSR induced chirp.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOMS024

About •

Received ※ 20 May 2022 — Revised ※ 12 June 2022 — Accepted ※ 24 June 2022 — Issue date ※ 29 June 2022

Cite •

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

TUPOMS044

Dielectric Loaded THz Waveguide Experimentally Optimized by Dispersion Measurements

1526

SUSPMF027

use link to see paper's listing under its alternate paper code

M.J. Kellermeier, R.W. Aßmann, K. Flöttmann, F. Lemery
DESY, Hamburg, Germany
R.W. Aßmann
LNF-INFN, Frascati, Italy
W. Hillert
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany

Emerging high power THz sources pave the road for THz- driven acceleration of ultra-short bunches, and enable their manipulation for diagnostic purposes. Due to the small feature sizes of THz-guiding devices new methods are necessary for their electromagnetic characterization. A new technique has recently been developed which characterizes THz waveguides with respect to their dispersion relations and attenuation. Here, the method is applied to circular waveguides, partially filled with polymer capillaries of different thicknesses, to find a suitable size for THz driven streaking at 287 GHz. Further, rough 3d-printed metallic waveguides are measured to study the effect of roughness on attenuation and phase constant. In general, additive manufacturing techniques show promise for advanced integrated designs of THz driven structures.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-TUPOMS044

About •

Received ※ 05 June 2022 — Revised ※ 12 June 2022 — Accepted ※ 15 June 2022 — Issue date ※ 28 June 2022

Cite •

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

THOXSP3

Path to High Repetition Rate Seeding: Combining High Gain Harmonic Generation with an Optical Klystron

2411

G. Paraskaki, E. Ferrari, L. Schaper, E. Schneidmiller
DESY, Hamburg, Germany
E. Allaria
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
W. Hillert
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany

External seeding in combination with harmonic generation has become a hot topic in the field of high gain free-electron lasers (FELs) since it allows delivery of superior FEL radiation characterized by, for example, full coherence and unprecedented shot-to-shot stability. At low repetition rate machines operating at few 10 Hz, novel experiments have been realized already, however, at superconducting machines, current laser technology does not support exploiting the full repetition rate available. One way to overcome this problem is to reduce the requirements in seed laser power: here, an optical klystron based high gain harmonic generation (HGHG) setup is proposed to reduce the laser peak power requirements by orders of magnitude, enabling operation at drastically increased repetition rates. We report simulation results based on the seeded beamline concept of the FLASH2020+ project. Among other topics, the effect of a linear electron beam energy chirp on this setup will be discussed.

Slides THOXSP3 [1.502 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THOXSP3

About •

Received ※ 08 June 2022 — Revised ※ 14 June 2022 — Accepted ※ 16 June 2022 — Issue date ※ 27 June 2022

Cite •

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

THOYGD2

Experimental Slice Emittance Reduction at PITZ Using Laser Pulse Shaping

R. Niemczyk, Z. Aboulbanine, G.D. Adhikari, N. Aftab, P. Boonpornprasert, G.Z. Georgiev, J. Good, M. Groß, C. Koschitzki, X.-K. Li, O. Lishilin, D. Melkumyan, S.K. Mohanty, A. Oppelt, H.J. Qian, H. Shaker, G. Shu, F. Stephan, T. Weilbach
DESY Zeuthen, Zeuthen, Germany
M.E. Castro Carballo, M. Krasilnikov, G. Vashchenko
DESY, Hamburg, Germany
W. Hillert
University of Hamburg, Institut für Experimentalphysik, Hamburg, Germany

Free-electron lasers in the X-ray regime require a high-brightness electron beam, i.e. an electron beam with high current and low transverse emittance. At the Photo Injector Test facility at DESY in Zeuthen (PITZ) high-brightness electron sources are optimized for the use at FLASH and European XFEL. A low transverse emittance of the electron beam’s central part, which is assumed to be the lasing slices, is of particular interest for the efficient FEL operation. Over the past years a slice emittance measurement scheme has been developed at PITZ which employs an rf deflector and additional quadrupole magnets along the beamline to the standard measurement procedure for the projected emittance (single-slit scan). It allows measuring the slice emittance in a high-brightness photo injector. Transversely flat-top shaped laser pulses of different temporal distributions (Gaussian and flat-top) have been used to emit electrons, as well as transversely-truncated Gaussian laser pulses with temporal Gaussian shape. The paper shows that the lowest slice emittance in the injector is reached with a temporal flattop shape, or when using a transversely-truncated Gaussian shape.

Slides THOYGD2 [2.045 MB]

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