FEL2015 - List of Authors (Di Mitri, S.)

Paper	Title	Page
MOC03	Estimate of Free-Electron Laser Gain Length in the Presence of Electron Beam Collective Effects	24
	S. Di Mitri Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy S. Spampinati Cockcroft Institute, Warrington, Cheshire, United Kingdom
	A novel definition for the three-dimensional free electron laser gain length is proposed, which takes into account the increase of electron beam projected emittance as due, for example, to geometric transverse wakefield and coherent synchrotron radiation developing in linear accelerators. The analysis shows that the gain length is affected by an increase of the electron beam projected emittance, even though the slice (local) emittance is preserved, and found to be in agreement with Genesis code simulation results. It is then shown that the minimum gain length and the maximum of output power may notably differ from the ones derived when collective effects are neglected. The proposed model turns out to be handy for a parametric study of electron beam six-dimensional brightness and FEL performance as function, e.g., of bunch length compression factor, accelerator alignment tolerances and optics design. S. Di Mitri, S. Spampinati, Phys. Rev. Special Topics Accel. Beams, 17, 110702 (2014)
	Slides MOC03 [2.528 MB]
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MOP013	The Fermi Seeded FEL Facility: Operational Experience and Future Perspectives	57
	L. Giannessi, E. Allaria, L. Badano, F. Bencivenga, C. Callegari, F. Capotondi, D. Castronovo, P. Cinquegrana, M. Coreno, R. Cucini, I. Cudin, G. D'Auria, M.B. Danailov, R. De Monte, G. De Ninno, P. Delgiusto, A.A. Demidovich, S. Di Mitri, B. Diviacco, A. Fabris, R. Fabris, W.M. Fawley, M. Ferianis, E. Ferrari, P. Finetti, P. Furlan Radivo, G. Gaio, D. Gauthier, F. Gelmetti, F. Iazzourene, M. Kiskinova, S. Krecic, M. Lonza, N. Mahne, M. Manfredda, C. Masciovecchio, M. Milloch, F. Parmigiani, E. Pedersoli, G. Penco, L. Pivetta, O. Plekan, M. Predonzani, K.C. Prince, E. Principi, L. Raimondi, P. Rebernik Ribič, F. Rossi, E. Roussel, L. Rumiz, C. Scafuri, C. Serpico, P. Sigalotti, M. Svandrlik, C. Svetina, M. Trovò, A. Vascotto, M. Veronese, R. Visintini, D. Zangrando, M. Zangrando Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
	FERMI is the seeded FEL user facility in Trieste, Italy, producing photons from the VUV to the soft X-rays with a high degree of coherence and spectral stability. Both FEL lines, FEL-1 and FEL-2, are available for users, down to the shortest wavelength of 4 nm. We report on the completion of the commissioning of the high energy FEL line, FEL-2, on the most recent progress obtained on FEL-1 and on the operational experience for users, in particular those requiring specific FEL configurations, such as two-colour experiments. We will also give a perspective on the improvements and upgrades which have been triggered based on our experience, aiming to maintain as well as to constantly improve the performance of the facility for our user community.
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MOP034	Beam Optics Measurements at FERMI by using Wire-Scanner	101
	G. Penco, A. Abrami, I. Cudin, S. Di Mitri, M. Ferianis, E. Ferrari, G. Gaio, L. Giannessi, S. Grulja, R. Sauro, L. Sturari Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy E. Ferrari Università degli Studi di Trieste, Trieste, Italy L. Giannessi ENEA C.R. Frascati, Frascati (Roma), Italy G.L. Orlandi, C. Ozkan Loch PSI, Villigen PSI, Switzerland
	Measuring and controlling the electron beam optics is an important ingredient to guarantee high performance of a free-electron laser. In the FERMI linac, the Twiss parameters and the transverse emittances are routinely measured by detecting the beam spot size as a function of a scanning quadrupole placed upstream (i.e. quadrupole scan method). The beam spot size is usually measured with an OTR screen that unfortunately suffers from coherent optical transition radiation (C-OTR) that introduces spurious light and corrupts the image. Moreover, the beam size at the end of the FERMI linac is focused to a few tens of microns and this makes it difficult to precisely measure it with the OTR system, which has an estimated resolution of 20um. For this reason, a wire-scanner system has been installed at the end of the linac just in the waist of the optics channel. The wire-scanner is a SwissFEL prototype installed in FERMI in order to study the hardware and beam loss monitor performances at the GeV energy scale. The beam optics measurements performed with the wire-scanner is here presented, and the obtained results are more in agreement with the theoretical expectations. A more reliable beam optics estimation at the end of the linac has allowed to better match it to the nominal lattice and transport it up to the undulator chain, providing important benefits to the FEL performance.
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MOP053	Intra-Beam Scattering in High Brightness Electron Linacs	153
	S. Di Mitri Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
	Intra-beam scattering (IBS) of a high brightness electron beam in a linac has been studied* analytically, and the expectations found to be in reasonable agreement with particle tracking results from the Elegant code. It comes out that, under standard conditions for a linac driving a free electron laser, IBS plays no significant role in the development of microbunching instability. A partial damping of the instability is envisaged, however, when IBS is enhanced either with dedicated magnetic insertions, or in the presence of an electron beam charge density at least 4 times larger than that produced by present photo-injectors. * S. Di Mitri, Phys. Rev. Special Topics Accel. Beams, 17, 074401 (2014).
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MOP067	Transverse Emittance-Preserving Transfer Line and Arc Compressor for High Brightness Electron Sources	191
	S. Di Mitri, M. Cornacchia, S. Spampinati Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy S. Spampinati Cockcroft Institute, Warrington, Cheshire, United Kingdom
	Minimizing transverse emittance is essential in single- or few-passes accelerators designed to deliver high brightness electron beams. Emission of coherent synchrotron radiation (CSR) is an important factor of emittance degradation. We have demonstrated, with analytical and experimental results, that this perturbation may be cancelled by imposing certain conditions on the electron optics when the bunch length is constant along the line. This scheme of CSR suppression is then enlarged, analytically and numerically, to cover the case of varying bunch length in a periodic arc compressor. The proposed solution hold the promise of cost-saving of compact transfer lines with large bending angles, and new schemes for beam longitudinal gymnastics both in recirculating and in single-pass accelerators driving free electron lasers. S. Di Mitri, M. Cornacchia, S. Spampinati, Phys. Rev. Letters, 110, 014801 (2013) ** S. Di Mitri, M. Cornacchia, Europhys. Letters, 109, 62002 (2015)
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MOP079	On the Importance of Electron Beam Brightness in High Gain Free Electron Lasers	227
	S. Di Mitri Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
	Linear accelerators delivering high brightness electron beams are essential for driving short wavelength, high gain free-electron lasers (FELs). The FEL radiation output efficiency is often parametrized through the power gain length that relates FEL performance to the electron beam quality at the undulator. Experimental data and simulation results of existing and planned FEL facilities are used to explicit the relationship between the FEL output wavelength and the electron beam six-dimensional brightness. Practical formulas are provided that show the dependence of the exponential gain length on the beam brightness. S. Di Mitri, M. Cornacchia, Phys. Reports, 539 (2014) 1~48. ** S. Di Mitri, Photonics, 2 (2015) 317~341
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TUB04	Influence of a Non-Uniform Longitudinal Heating on High Brightness Electron Beams for FEL
	E. Ferrari Università degli Studi di Trieste, Trieste, Italy E. Allaria, M.B. Danailov, G. De Ninno, S. Di Mitri, D. Gauthier, L. Giannessi, G. Penco, E. Roussel, M. Veronese Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy G. De Ninno, D. Gauthier University of Nova Gorica, Nova Gorica, Slovenia L. Giannessi ENEA C.R. Frascati, Frascati (Roma), Italy
	Laser-heater systems are essential tools to control and optimize high-gain free electron lasers (FELs), working in the x-ray wavelength range. Indeed, these systems induce a controllable heating of the energy spread of the electron bunch. The heating allows in turn to suppress longitudinal microbunching instabilities limiting the FEL performance. In this communication, we show that a long-wavelength energy modulation of the electron beam induced by the laser heater can be preserved until the beam entrance in the undulators, affecting the FEL emission process. This non-uniform longitudinal heating can be exploited to investigate the electron- beam microbunching in the linac, as well as to control the FEL spectral properties. Here, we present experimental, analytical and numerical studies carried out at FERMI.
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TUP013	The X-Band FEL Collaboration	368
	J. Pfingstner, E. Adli University of Oslo, Oslo, Norway A.A. Aksoy, Ö. Yavaş Ankara University, Accelerator Technologies Institute, Golbasi / Ankara, Turkey D. Angal-Kalinin, J.A. Clarke STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom C.J. Bocchetta, A.I. Wawrzyniak Solaris, Kraków, Poland M.J. Boland, T.K. Charles, R.T. Dowd, G. LeBlanc, Y.E. Tan, K.P. Wootton, D. Zhu SLSA, Clayton, Australia G. Burt Lancaster University, Lancaster, United Kingdom N. Catalán Lasheras, A. Grudiev, A. Latina, D. Schulte, S. Stapnes, I. Syratchev, W. Wuensch CERN, Geneva, Switzerland A. Charitonidis NTUA, Athens, Greece G. D'Auria, S. Di Mitri, C. Serpico Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy T.J.C. Ekelöf, M. Jacewicz, R.J.M.Y. Ruber, V.G. Ziemann Uppsala University, Uppsala, Sweden W. Fang, Q. Gu SINAP, Shanghai, People's Republic of China E.N. Gazis National Technical University of Athens, Athens, Greece X.J.A. Janssen VDL ETG, Eindhoven, The Netherlands Z. Nergiz Nigde University, Nigde, Turkey
	The X-band FEL collaboration is currently designing an X-ray free-electron laser based on X-band acceleration technology. Due to the higher accelerating gradients achievable with X-band technology, a X-band normal conducting linac can be shorter and therefore potentially cost efficient than what is achievable with lower frequency structures. This cost reduction of future FEL facilities addresses the growing demand of the user community for coherent X-rays. The X-band FEL collaboration consists of 12 institutes and universities that jointly work on the preparation of design reports for the specific FEL projects. In this paper, we report on the on-going activities, the basic parameter choice, and the integrated simulation results. We also outline the interest of the X-band FEL collaboration to use the electron linac CALIFES at CERN to test FEL concepts and technologies relevant for the X-band FEL collaboration.
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Paper

Title

Page

Estimate of Free-Electron Laser Gain Length in the Presence of Electron Beam Collective Effects

24

S. Di Mitri
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
S. Spampinati
Cockcroft Institute, Warrington, Cheshire, United Kingdom

A novel definition for the three-dimensional free electron laser gain length is proposed*, which takes into account the increase of electron beam projected emittance as due, for example, to geometric transverse wakefield and coherent synchrotron radiation developing in linear accelerators. The analysis shows that the gain length is affected by an increase of the electron beam projected emittance, even though the slice (local) emittance is preserved, and found to be in agreement with Genesis code simulation results. It is then shown that the minimum gain length and the maximum of output power may notably differ from the ones derived when collective effects are neglected. The proposed model turns out to be handy for a parametric study of electron beam six-dimensional brightness and FEL performance as function, e.g., of bunch length compression factor, accelerator alignment tolerances and optics design.
* S. Di Mitri, S. Spampinati, Phys. Rev. Special Topics Accel. Beams, 17, 110702 (2014)

Slides MOC03 [2.528 MB]

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MOP013

The Fermi Seeded FEL Facility: Operational Experience and Future Perspectives

57

L. Giannessi, E. Allaria, L. Badano, F. Bencivenga, C. Callegari, F. Capotondi, D. Castronovo, P. Cinquegrana, M. Coreno, R. Cucini, I. Cudin, G. D'Auria, M.B. Danailov, R. De Monte, G. De Ninno, P. Delgiusto, A.A. Demidovich, S. Di Mitri, B. Diviacco, A. Fabris, R. Fabris, W.M. Fawley, M. Ferianis, E. Ferrari, P. Finetti, P. Furlan Radivo, G. Gaio, D. Gauthier, F. Gelmetti, F. Iazzourene, M. Kiskinova, S. Krecic, M. Lonza, N. Mahne, M. Manfredda, C. Masciovecchio, M. Milloch, F. Parmigiani, E. Pedersoli, G. Penco, L. Pivetta, O. Plekan, M. Predonzani, K.C. Prince, E. Principi, L. Raimondi, P. Rebernik Ribič, F. Rossi, E. Roussel, L. Rumiz, C. Scafuri, C. Serpico, P. Sigalotti, M. Svandrlik, C. Svetina, M. Trovò, A. Vascotto, M. Veronese, R. Visintini, D. Zangrando, M. Zangrando
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy

FERMI is the seeded FEL user facility in Trieste, Italy, producing photons from the VUV to the soft X-rays with a high degree of coherence and spectral stability. Both FEL lines, FEL-1 and FEL-2, are available for users, down to the shortest wavelength of 4 nm. We report on the completion of the commissioning of the high energy FEL line, FEL-2, on the most recent progress obtained on FEL-1 and on the operational experience for users, in particular those requiring specific FEL configurations, such as two-colour experiments. We will also give a perspective on the improvements and upgrades which have been triggered based on our experience, aiming to maintain as well as to constantly improve the performance of the facility for our user community.

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MOP034

Beam Optics Measurements at FERMI by using Wire-Scanner

101

G. Penco, A. Abrami, I. Cudin, S. Di Mitri, M. Ferianis, E. Ferrari, G. Gaio, L. Giannessi, S. Grulja, R. Sauro, L. Sturari
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
E. Ferrari
Università degli Studi di Trieste, Trieste, Italy
L. Giannessi
ENEA C.R. Frascati, Frascati (Roma), Italy
G.L. Orlandi, C. Ozkan Loch
PSI, Villigen PSI, Switzerland

Measuring and controlling the electron beam optics is an important ingredient to guarantee high performance of a free-electron laser. In the FERMI linac, the Twiss parameters and the transverse emittances are routinely measured by detecting the beam spot size as a function of a scanning quadrupole placed upstream (i.e. quadrupole scan method). The beam spot size is usually measured with an OTR screen that unfortunately suffers from coherent optical transition radiation (C-OTR) that introduces spurious light and corrupts the image. Moreover, the beam size at the end of the FERMI linac is focused to a few tens of microns and this makes it difficult to precisely measure it with the OTR system, which has an estimated resolution of 20um. For this reason, a wire-scanner system has been installed at the end of the linac just in the waist of the optics channel. The wire-scanner is a SwissFEL prototype installed in FERMI in order to study the hardware and beam loss monitor performances at the GeV energy scale. The beam optics measurements performed with the wire-scanner is here presented, and the obtained results are more in agreement with the theoretical expectations. A more reliable beam optics estimation at the end of the linac has allowed to better match it to the nominal lattice and transport it up to the undulator chain, providing important benefits to the FEL performance.

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MOP053

Intra-Beam Scattering in High Brightness Electron Linacs

153

S. Di Mitri
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy

Intra-beam scattering (IBS) of a high brightness electron beam in a linac has been studied* analytically, and the expectations found to be in reasonable agreement with particle tracking results from the Elegant code. It comes out that, under standard conditions for a linac driving a free electron laser, IBS plays no significant role in the development of microbunching instability. A partial damping of the instability is envisaged, however, when IBS is enhanced either with dedicated magnetic insertions, or in the presence of an electron beam charge density at least 4 times larger than that produced by present photo-injectors.
* S. Di Mitri, Phys. Rev. Special Topics Accel. Beams, 17, 074401 (2014).

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MOP067

Transverse Emittance-Preserving Transfer Line and Arc Compressor for High Brightness Electron Sources

191

S. Di Mitri, M. Cornacchia, S. Spampinati
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
S. Spampinati
Cockcroft Institute, Warrington, Cheshire, United Kingdom

Minimizing transverse emittance is essential in single- or few-passes accelerators designed to deliver high brightness electron beams. Emission of coherent synchrotron radiation (CSR) is an important factor of emittance degradation. We have demonstrated, with analytical and experimental results, that this perturbation may be cancelled by imposing certain conditions on the electron optics when the bunch length is constant along the line*. This scheme of CSR suppression is then enlarged, analytically and numerically, to cover the case of varying bunch length in a periodic arc compressor**. The proposed solution hold the promise of cost-saving of compact transfer lines with large bending angles, and new schemes for beam longitudinal gymnastics both in recirculating and in single-pass accelerators driving free electron lasers.
* S. Di Mitri, M. Cornacchia, S. Spampinati, Phys. Rev. Letters, 110, 014801 (2013)
** S. Di Mitri, M. Cornacchia, Europhys. Letters, 109, 62002 (2015)

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MOP079

On the Importance of Electron Beam Brightness in High Gain Free Electron Lasers

227

S. Di Mitri
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy

Linear accelerators delivering high brightness electron beams are essential for driving short wavelength, high gain free-electron lasers (FELs). The FEL radiation output efficiency is often parametrized through the power gain length that relates FEL performance to the electron beam quality at the undulator. Experimental data and simulation results of existing and planned FEL facilities are used to explicit the relationship between the FEL output wavelength and the electron beam six-dimensional brightness*. Practical formulas are provided that show the dependence of the exponential gain length on the beam brightness**.
* S. Di Mitri, M. Cornacchia, Phys. Reports, 539 (2014) 1~48.
** S. Di Mitri, Photonics, 2 (2015) 317~341

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TUB04

Influence of a Non-Uniform Longitudinal Heating on High Brightness Electron Beams for FEL

E. Ferrari
Università degli Studi di Trieste, Trieste, Italy
E. Allaria, M.B. Danailov, G. De Ninno, S. Di Mitri, D. Gauthier, L. Giannessi, G. Penco, E. Roussel, M. Veronese
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
G. De Ninno, D. Gauthier
University of Nova Gorica, Nova Gorica, Slovenia
L. Giannessi
ENEA C.R. Frascati, Frascati (Roma), Italy

Laser-heater systems are essential tools to control and optimize high-gain free electron lasers (FELs), working in the x-ray wavelength range. Indeed, these systems induce a controllable heating of the energy spread of the electron bunch. The heating allows in turn to suppress longitudinal microbunching instabilities limiting the FEL performance. In this communication, we show that a long-wavelength energy modulation of the electron beam induced by the laser heater can be preserved until the beam entrance in the undulators, affecting the FEL emission process. This non-uniform longitudinal heating can be exploited to investigate the electron- beam microbunching in the linac, as well as to control the FEL spectral properties. Here, we present experimental, analytical and numerical studies carried out at FERMI.

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TUP013

The X-Band FEL Collaboration

368

J. Pfingstner, E. Adli
University of Oslo, Oslo, Norway
A.A. Aksoy, Ö. Yavaş
Ankara University, Accelerator Technologies Institute, Golbasi / Ankara, Turkey
D. Angal-Kalinin, J.A. Clarke
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire, United Kingdom
C.J. Bocchetta, A.I. Wawrzyniak
Solaris, Kraków, Poland
M.J. Boland, T.K. Charles, R.T. Dowd, G. LeBlanc, Y.E. Tan, K.P. Wootton, D. Zhu
SLSA, Clayton, Australia
G. Burt
Lancaster University, Lancaster, United Kingdom
N. Catalán Lasheras, A. Grudiev, A. Latina, D. Schulte, S. Stapnes, I. Syratchev, W. Wuensch
CERN, Geneva, Switzerland
A. Charitonidis
NTUA, Athens, Greece
G. D'Auria, S. Di Mitri, C. Serpico
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
T.J.C. Ekelöf, M. Jacewicz, R.J.M.Y. Ruber, V.G. Ziemann
Uppsala University, Uppsala, Sweden
W. Fang, Q. Gu
SINAP, Shanghai, People's Republic of China
E.N. Gazis
National Technical University of Athens, Athens, Greece
X.J.A. Janssen
VDL ETG, Eindhoven, The Netherlands
Z. Nergiz
Nigde University, Nigde, Turkey

The X-band FEL collaboration is currently designing an X-ray free-electron laser based on X-band acceleration technology. Due to the higher accelerating gradients achievable with X-band technology, a X-band normal conducting linac can be shorter and therefore potentially cost efficient than what is achievable with lower frequency structures. This cost reduction of future FEL facilities addresses the growing demand of the user community for coherent X-rays. The X-band FEL collaboration consists of 12 institutes and universities that jointly work on the preparation of design reports for the specific FEL projects. In this paper, we report on the on-going activities, the basic parameter choice, and the integrated simulation results. We also outline the interest of the X-band FEL collaboration to use the electron linac CALIFES at CERN to test FEL concepts and technologies relevant for the X-band FEL collaboration.

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