LINAC2014 - List of Keywords (FEL)

Paper	Title	Other Keywords	Page
MOIOA01	Linear Collider Studies	emittance, linac, linear-collider, collider	1
	S. Stapnes CERN, Geneva, Switzerland
	Status and comparison of the two remaining linear collider designs following publication of their CDRs
	Slides MOIOA01 [11.279 MB]

MOPP023	X-band Technology for FEL Sources	linac, emittance, operation, experiment	101
	G. D'Auria, S. Di Mitri, C. Serpico Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy E. Adli University of Oslo, Oslo, Norway A.A. Aksoy, O. 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 W. Fang, Q. Gu SINAP, Shanghai, People's Republic of China E.N. Gazis National Technical University of Athens, Athens, Greece M. Jacewicz, R.J.M.Y. Ruber, V.G. Ziemann Uppsala University, Uppsala, Sweden X.J.A. Janssen VDL ETG, Eindhoven, The Netherlands
	As is widely recognized, fourth generation Light Sources are based on FELs driven by Linacs. Soft and hard X-ray FEL facilities are presently operational at several laboratories, SLAC (LCLS), Spring-8 (SACLA), Elettra-Sincrotrone Trieste (FERMI), DESY (FLASH), or are in the construction phase, PSI (SwissFEL), PAL (PAL-XFEL), DESY (European X-FEL), SLAC (LCLS II), or are newly proposed in many laboratories. Most of the above mentioned facilities use NC S-band (3 GHz) or C-band (6 GHz) linacs for generating a multi-GeV low emittance beam. The use of the C-band increases the linac operating gradients, with an overall reduction of the machine length and cost. These advantages, however, can be further enhanced by using X-band (12 GHz) linacs that operate with gradients twice that given by C-band technology. With the low bunch charge option, currently considered for future X-ray FELs, X-band technology offers a low cost and compact solution for generating multi-GeV, low emittance bunches. The paper reports the ongoing activities in the framework of a collaboration among several laboratories for the development and validation of X-band technology for FEL based photon sources.

MOPP024	Perspectives of the S-Band Linac of FERMI	operation, linac, klystron, electron	105
	A. Fabris, P. Delgiusto, M. Milloch, C. Serpico Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy A. Grudiev CERN, Geneva, Switzerland
	The S-band linac of FERMI, the seeded Free Electron Laser (FEL) located at the Elettra laboratory in Trieste, has reached the peak on-crest electron energy of 1.55 GeV required for FEL-2 with the present layout. Different ways are being considered to extend the operating energy of the S-band linac up to 1.8 GeV. At the same time upgrades on the existing systems are investigated to address the requirements of operability of a users facility. This paper provides an overview of the developments that are under consideration and discusses the requirements and constraints for their implementation.

MOPP083	Helical Waveguides for Short Wavelength Accelerators and RF Undulators	undulator, electron, focusing, radiation	248
	S.V. Kuzikov, A.V. Savilov, A.A. Vikharev IAP/RAS, Nizhny Novgorod, Russia A.V. Savilov NNGU, Nizhny Novgorod, Russia
	The short wavelength accelerating structure can combine properties of a linear accelerator and a damping ring simultaneously. It provides acceleration of straight on-axis beam as well as cooling of this beam due to the synchrotron radiation of particles. These properties are provided by specific slow eigen mode which consists of two partial waves, TM01 and TM11. The flying RF undulator introduces a high-power short pulse, propagating in a long helically corrugated waveguide where the -1st space harmonic with negative phase velocity is responsible for particle wiggling. High group velocity allows providing long interaction of particles with RF pulse. Calculations show that RF undulator with period 5 mm, undulator parameter 0.1 is possible in 1 GW 10 ns pulse at frequency 30 GHz. The eigen mode in a helical undulator might have 0th harmonic phase velocity equal to light velocity. Such wave can be excited by relativistic drive bunch in the waveguide where witness bunch follows after the drive bunch, wiggles in wakefields, and generates X-rays at whole waveguide length. Helical waveguides can also be used in order to channel low-energy bunches in RF undulator of THz FEL.
	Poster MOPP083 [2.139 MB]

MOPP119	Measurements and High Power Test of the First C-band Accelerating Structure for SwissFEL	operation, vacuum, klystron, linac	333
	R. Zennaro, J. Alex, A. Citterio, J.-Y. Raguin PSI, Villigen PSI, Switzerland
	The SwissFEL project is based on a 5.8 GeV C-band Linac which is composed of 10⁴ accelerating structures with a length of 2 m each. Due to the absence of dimple tuning no local frequency correction is possible and hence ultra-precise machining is required. The paper reports on both low level and high power RF test of the first nominal structure produced. The required mechanical precision has been reached and the structure has been successfully power tested to a gradient larger than 50 MV/m, well above the nominal level of 28 MV/m. The measured dark current and break down rates are well in the specifications.

MOPP139	Studies of Coherent Synchrotron Radiation in the Jefferson Lab FEL Driver with Implications for Bunch Compression	linac, emittance, acceleration, simulation	388
	C. Tennant, D. Douglas, R. Li JLab, Newport News, Virginia, USA C.-Y. Tsai Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA
	Funding: Work supported by the Office of Naval Research and the High Energy Laser Joint Technology. Jefferson Laboratory work is supported under U.S. DOE Contract No. DE-AC05-06OR23177. The Jefferson Laboratory IR FEL Driver provides an ideal test bed for studying a variety of beam dynamical effects. Recent studies focused on characterizing the impact of coherent synchrotron radiation (CSR) with the goal of benchmarking measurements with simulation. Following measurements to characterize the beam, we quantitatively characterized energy extraction via CSR by measuring beam position at a dispersed location as a function of bunch compression. In addition to operating with the beam on the rising part of the linac RF waveform, measurements were also made while accelerating on the falling part. For each, the full compression point was moved along the backleg of the machine and the response of the beam (distribution, extracted energy) measured. Initial results of start-to-end simulations using a 1D CSR algorithm show remarkably good agreement with measurements. A subsequent experiment established lasing with the beam accelerated on the falling side of the RF waveform in conjunction with positive momentum compaction (R56) to compress the bunch. The success of this experiment motivated the design of a modified CEBAF-style arc with control of CSR and microbunching effects.

TUPP020	Beam Dynamics Simulation for FLASH2 HGHG Option	simulation, undulator, radiation, electron	471
	G. Feng, S. Ackermann, J. Bödewadt, W. Decking, M. Dohlus, Y.A. Kot, T. Limberg, M. Scholz, I. Zagorodnov DESY, Hamburg, Germany K.E. Hacker DELTA, Dortmund, Germany T. Plath Uni HH, Hamburg, Germany
	The free electron laser (FEL) facility at DESY in Hamburg (FLASH) is the world's first FEL user facility which can produce extreme ultraviolet (XUV) and soft X-ray photons. In order to increase the beam time delivered to users, a major upgrade named FLASH II is in progress. The electron beamline of FLASH2 consists of diagnostic and matching sections and a SASE undulator section. A seeding undulator section will be installed in the future. FLASH2 will be used as a seeded FEL as well as a SASE FEL. In this paper, some results of beam dynamics simulation for the SASE option are given at first which includes the parameters selection for the bunch compressors, RF parameters calculation for the accelerating modules and the beam dynamics simulation taking into account the collective effects. Beam dynamics simulation for a single stage HGHG option is based on the work for the SASE option. Electron bunches with low uncorrelated energy spread and small energy chirp are obtained after parameters optimization. The FEL simulation results show that 33.6 nm wavelength FEL radiation with high monochromaticity can be seeded at FLASH2 with a 235 nm seeding laser.

TUPP078	High Gain FEL with a Micro-bunch Structured Beam by the Transverse-Longitudinal Phase Space Rotation	cavity, radiation, electron, cathode	607
	M. Kuriki, Y. Seimiya HU/AdSM, Higashi-Hiroshima, Japan H. Hayano, K. Ohmi KEK, Ibaraki, Japan S. Kashiwagi Tohoku University, Research Center for Electron Photon Science, Sendai, Japan R. Kato ISIR, Osaka, Japan
	FEL is one of the ideal radiation source over the wide range of wavelength region with a high brightness and a high coherence. Many methods to improve FEL gain has been proposed by introducing an active modulation on the bunch charge distribution. The transverse-longitudinal phase-space rotation is one of the promising method to realize the density modulation as the micro-bunch structure. Initially, a beam density modulation in the transverse direction made by a mechanical slit, is properly transformed into the density modulation in the longitudinal direction by the phase-space rotation. That results the longitudinal micro-bunch structure. The micro-bunch structure made with this method has a large tunability by changing the slit geometry, the beam line design, and the beam dynamics tuning. A compact FEL facility based on this method is proposed.
	Poster TUPP078 [0.594 MB]

TUPP122	Roughness Tolerances in the Undulator Vacuum Chamber of LCLS-II	impedance, undulator, vacuum, wakefield	708
	K.L.F. Bane, G.V. Stupakov SLAC, Menlo Park, California, USA
	Funding: Work supported by Department of Energy contract DE–AC02–76SF00515. In LCLS-II, after acceleration and compression and just before entering the undulator, the beam passes through roughly 2.5 km of 24.5 mm (radius) stainless steel pipe. The bunch that passes through the pipe is extremely short with an rms of 8 um for the nominal 100 pC case. Thus, even though the pipe has a large aperture, the wake that applies is the short-range resistive wall wakefield. It turns out that the wake supplies needed dechirping to the LCLS-II beam before it enters the undulator. The LCLS-II bunch distribution is approximately uniform, and therefore the wake induced voltage is characterized by a rather linear voltage chirp for short bunches. However for bunches longer than 25 um (300 pC at 1 kA) the wake starts to become nonlinear, effectively limiting the maximum charge with which the LCLS-II can operate. In this note we calculate the wake, discuss the confidence in the calculation, and investigate how to improve the induced chirp linearity and/or strength. Finally, we also study the strength and effects of the transverse (dipole) resistive wall wakefield.

TUPP127	R&D of X-band Accelerating Structure for Compact XFEL at SINAP	linac, simulation, wakefield, radiation	715
	W. Fang, Q. Gu, M. Zhang, Z.T. Zhao SINAP, Shanghai, People's Republic of China A.A. Aksoy, O. Yavaş Ankara University, Accelerator Technologies Institute, Golbasi / Ankara, Turkey D. Angal-Kalinin, J.A. Clarke Cockcroft Institute, Warrington, Cheshire, United Kingdom C.J. Bocchetta, A.I. Wawrzyniak Solaris, Kraków, Poland M.J. Boland SLSA, Clayton, Australia G. D'Auria, S. Di Mitri, C. Serpico Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy T.J.C. Ekelöf, R.J.M.Y. Ruber, V.G. Ziemann Uppsala University, Uppsala, Sweden E.N. Gazis National Technical University of Athens, Athens, Greece A. Grudiev, A. Latina, D. Schulte, S. Stapnes, W. Wuensch CERN, Geneva, Switzerland
	One compact hard X-ray FEL facility is being planned at SINAP, and X-band high gradient accelerating structure is the most competetive scheme for this plan. X-band accelerating structure is designed to switch between 60MV/m and 80MV/m, and carries out 6GeV and 8GeV by 130 meters linac respectively. In this paper, brief layout of compact XFEL will be introduced, and in particular the prototype design of dedicated X-band acceleration RF system is also presented.

TUPP128	ECHO-enabled Tunable Terahertz Radiation Generation with a Laser-modulated Relativistic Electron Beam	laser, radiation, electron, simulation	719
	D. Huang, Q. Gu, Z. Wang, Z.T. Zhao SINAP, Shanghai, People's Republic of China D. Xiang Shanghai Jiao Tong University, Shanghai, People's Republic of China
	A new scheme to generate narrow-band tunable Terahertz (THz) radiation using a variant of the echo-enabled harmonic generation is analyzed. We show that by using an energy chirped beam, THz density modulation in the beam phase space can be produced with two lasers having the same wavelength. This removes the need for an optical parametric amplifier system to provide a wavelength-tunable laser to vary the central frequency of the THz radiation. The practical feasibility and applications of this scheme is demonstrated numerically with a start-to-end simulation using the beam parameters at Shanghai Deep Ultraviolet Free-Electron Laser facility (SDUV). The central frequency of the density modulation can be continuously tuned by either varying the chirp of the beam or the momentum compactions of the chicanes. The influence of nonlinear RF chirp and longitudinal space charge effect have also been studied in our article. We also briefly discuss how one may retrieve the beam longitudinal phase space through measurement of the THz density modulation. \end{abstract}

THIOB03	Results From the LCLS X-Band Transverse Deflector With Femtosecond Temporal Resolution	electron, undulator, photon, diagnostics	819
	Y. Ding, F.-J. Decker, V.A. Dolgashev, J.C. Frisch, Z. Huang, P. Krejcik, H. Loos, A. Lutmann, A. Marinelli, T.J. Maxwell, D.F. Ratner, J.L. Turner, J.W. Wang, M.-H. Wang, J.J. Welch, J. Wu SLAC, Menlo Park, California, USA C. Behrens DESY, Hamburg, Germany
	An X-band RF transverse deflector composed of two 1-m-long X-band deflecting structures has been recently commissioned at the Linac Coherent Light Source (LCLS) at SLAC National Accelerator Laboratory. Located downstream of the FEL undulator, this device provides electron beam longitudinal phase space diagnostics in both time and energy which enables reconstruction of the X-ray FEL power profiles with an unprecedented resolution. This talk reports on the progress of this new LCLS X-band transverse deflector, first usage experience and measured results.
	Slides THIOB03 [3.508 MB]

THPP084	Cyclotron-Undulator Cooling of Electron Beams	undulator, electron, cyclotron, simulation	1041
	S.V. Kuzikov, I.V. Bandurkin, A.V. Savilov IAP/RAS, Nizhny Novgorod, Russia A.V. Savilov NNGU, Nizhny Novgorod, Russia
	XFELs require high-quality electron beams which can be produced in damping rings. For XFEL, based on Compton scattering of laser light, instead of the damping ring we consider a new compact device where electrons move in the undulator with axial DC magnetic field. In this undulator electrons move near resonant condition, rotating with cyclotron frequency and wiggling at similar bounce frequency. Such undulator allows compensation of the initial velocity spread by perturbations of the longitudinal velocities caused by transverse wiggling. Calculation show that ~1% velocity spread of 5 MeV electron beam (typical for photoinjectors) can be reduced to ~0.01% at distance as long as 20 undulator periods. In the advanced scheme, where the described undulators alternate with sections of the cyclotron radiation, energy spread as small as 0.001% is reachable. Calculations show that this principle works also for high energy beams (100 MeV and more), where RF undulator instead of DC-magnet undulator is preferable.
	Poster THPP084 [0.713 MB]

THPP121	Injector System for the IR-FEL at RRCAT	beam-loading, linac, electron, cavity	1137
	L. Faillace, R.B. Agustsson RadiaBeam, Santa Monica, California, USA A. Kumar, K.K. Pant RRCAT, Indore (M.P.), India
	An infrared (IR) free-electron laser (FEL) has been proposed to be built at the Raja Ramanna Centre for Advanced Technology (RRCAT). RadiaBeam is currently involved in the design of the RRCAT FEL's injector system. The injector will deliver an electron beam with a variable energy (from 15 up to 40 MeV) and 1.5 nC at 36.6 MHz repetition rate. We show here the beam dynamics of the beam transport through the injector as well as the RF design and mechanical model of the system. * S. Krishnagopal et al., PRELIMINARY DESIGN OF THE PROPOSED IR-FEL IN INDIA, RRCAT, Indore, M.P. 452013, India

FRIOB01	Positive Trends in Radiation Risk Assessment and Consequent Opportunities for Linac Applications	radiation, linac, controls, simulation	1202
	Y. Socol Falcon Analytics, Netanya, Israel
	Ionizing radiation, an unavoidable by-product of high-energy LINACs, makes them subject to strict regulation and severe public concerns. During the last two decades the attitude to ionizing radiation hazards has been becoming more balanced, as opposed to the historical "radiophobia". The linear no-threshold hypothesis (LNTH), based on the assumption that every radiation dose increment constitutes increased cancer risk for humans, is more and more debated. In particular, the recent memorandum of the International Commission on Radiological Protection admits that the LNTH predictions at low doses are "speculative, unproven, undetectable and "phantom'." Moreover, numerous experimental, ecological, and epidemiological studies show that low doses of ionizing radiation may be beneficial to human health. While these advances in scientific understanding have not yet given fruit regarding radiation regulation and policy, we are hopeful these may happen in near to middle term. The presentation reviews the present status of the low-dose radiation-hazard debate. It also outlines anticipated opportunities for LINAC applications, especially in the prospective field of low-dose radiation therapy.
	Slides FRIOB01 [1.890 MB]

Paper

Title

Other Keywords

Page

MOIOA01

Linear Collider Studies

emittance, linac, linear-collider, collider

1

S. Stapnes
CERN, Geneva, Switzerland

Status and comparison of the two remaining linear collider designs following publication of their CDRs

Slides MOIOA01 [11.279 MB]

MOPP023

X-band Technology for FEL Sources

linac, emittance, operation, experiment

101

G. D'Auria, S. Di Mitri, C. Serpico
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
E. Adli
University of Oslo, Oslo, Norway
A.A. Aksoy, O. 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
W. Fang, Q. Gu
SINAP, Shanghai, People's Republic of China
E.N. Gazis
National Technical University of Athens, Athens, Greece
M. Jacewicz, R.J.M.Y. Ruber, V.G. Ziemann
Uppsala University, Uppsala, Sweden
X.J.A. Janssen
VDL ETG, Eindhoven, The Netherlands

As is widely recognized, fourth generation Light Sources are based on FELs driven by Linacs. Soft and hard X-ray FEL facilities are presently operational at several laboratories, SLAC (LCLS), Spring-8 (SACLA), Elettra-Sincrotrone Trieste (FERMI), DESY (FLASH), or are in the construction phase, PSI (SwissFEL), PAL (PAL-XFEL), DESY (European X-FEL), SLAC (LCLS II), or are newly proposed in many laboratories. Most of the above mentioned facilities use NC S-band (3 GHz) or C-band (6 GHz) linacs for generating a multi-GeV low emittance beam. The use of the C-band increases the linac operating gradients, with an overall reduction of the machine length and cost. These advantages, however, can be further enhanced by using X-band (12 GHz) linacs that operate with gradients twice that given by C-band technology. With the low bunch charge option, currently considered for future X-ray FELs, X-band technology offers a low cost and compact solution for generating multi-GeV, low emittance bunches. The paper reports the ongoing activities in the framework of a collaboration among several laboratories for the development and validation of X-band technology for FEL based photon sources.

MOPP024

Perspectives of the S-Band Linac of FERMI

operation, linac, klystron, electron

105

A. Fabris, P. Delgiusto, M. Milloch, C. Serpico
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
A. Grudiev
CERN, Geneva, Switzerland

The S-band linac of FERMI, the seeded Free Electron Laser (FEL) located at the Elettra laboratory in Trieste, has reached the peak on-crest electron energy of 1.55 GeV required for FEL-2 with the present layout. Different ways are being considered to extend the operating energy of the S-band linac up to 1.8 GeV. At the same time upgrades on the existing systems are investigated to address the requirements of operability of a users facility. This paper provides an overview of the developments that are under consideration and discusses the requirements and constraints for their implementation.

MOPP083

Helical Waveguides for Short Wavelength Accelerators and RF Undulators

undulator, electron, focusing, radiation

248

S.V. Kuzikov, A.V. Savilov, A.A. Vikharev
IAP/RAS, Nizhny Novgorod, Russia
A.V. Savilov
NNGU, Nizhny Novgorod, Russia

The short wavelength accelerating structure can combine properties of a linear accelerator and a damping ring simultaneously. It provides acceleration of straight on-axis beam as well as cooling of this beam due to the synchrotron radiation of particles. These properties are provided by specific slow eigen mode which consists of two partial waves, TM01 and TM11. The flying RF undulator introduces a high-power short pulse, propagating in a long helically corrugated waveguide where the -1st space harmonic with negative phase velocity is responsible for particle wiggling. High group velocity allows providing long interaction of particles with RF pulse. Calculations show that RF undulator with period 5 mm, undulator parameter 0.1 is possible in 1 GW 10 ns pulse at frequency 30 GHz. The eigen mode in a helical undulator might have 0th harmonic phase velocity equal to light velocity. Such wave can be excited by relativistic drive bunch in the waveguide where witness bunch follows after the drive bunch, wiggles in wakefields, and generates X-rays at whole waveguide length. Helical waveguides can also be used in order to channel low-energy bunches in RF undulator of THz FEL.

Poster MOPP083 [2.139 MB]

MOPP119

Measurements and High Power Test of the First C-band Accelerating Structure for SwissFEL

operation, vacuum, klystron, linac

333

R. Zennaro, J. Alex, A. Citterio, J.-Y. Raguin
PSI, Villigen PSI, Switzerland

The SwissFEL project is based on a 5.8 GeV C-band Linac which is composed of 10⁴ accelerating structures with a length of 2 m each. Due to the absence of dimple tuning no local frequency correction is possible and hence ultra-precise machining is required. The paper reports on both low level and high power RF test of the first nominal structure produced. The required mechanical precision has been reached and the structure has been successfully power tested to a gradient larger than 50 MV/m, well above the nominal level of 28 MV/m. The measured dark current and break down rates are well in the specifications.

MOPP139

Studies of Coherent Synchrotron Radiation in the Jefferson Lab FEL Driver with Implications for Bunch Compression

linac, emittance, acceleration, simulation

388

C. Tennant, D. Douglas, R. Li
JLab, Newport News, Virginia, USA
C.-Y. Tsai
Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA

Funding: Work supported by the Office of Naval Research and the High Energy Laser Joint Technology. Jefferson Laboratory work is supported under U.S. DOE Contract No. DE-AC05-06OR23177.
The Jefferson Laboratory IR FEL Driver provides an ideal test bed for studying a variety of beam dynamical effects. Recent studies focused on characterizing the impact of coherent synchrotron radiation (CSR) with the goal of benchmarking measurements with simulation. Following measurements to characterize the beam, we quantitatively characterized energy extraction via CSR by measuring beam position at a dispersed location as a function of bunch compression. In addition to operating with the beam on the rising part of the linac RF waveform, measurements were also made while accelerating on the falling part. For each, the full compression point was moved along the backleg of the machine and the response of the beam (distribution, extracted energy) measured. Initial results of start-to-end simulations using a 1D CSR algorithm show remarkably good agreement with measurements. A subsequent experiment established lasing with the beam accelerated on the falling side of the RF waveform in conjunction with positive momentum compaction (R56) to compress the bunch. The success of this experiment motivated the design of a modified CEBAF-style arc with control of CSR and microbunching effects.

TUPP020

Beam Dynamics Simulation for FLASH2 HGHG Option

simulation, undulator, radiation, electron

471

G. Feng, S. Ackermann, J. Bödewadt, W. Decking, M. Dohlus, Y.A. Kot, T. Limberg, M. Scholz, I. Zagorodnov
DESY, Hamburg, Germany
K.E. Hacker
DELTA, Dortmund, Germany
T. Plath
Uni HH, Hamburg, Germany

The free electron laser (FEL) facility at DESY in Hamburg (FLASH) is the world's first FEL user facility which can produce extreme ultraviolet (XUV) and soft X-ray photons. In order to increase the beam time delivered to users, a major upgrade named FLASH II is in progress. The electron beamline of FLASH2 consists of diagnostic and matching sections and a SASE undulator section. A seeding undulator section will be installed in the future. FLASH2 will be used as a seeded FEL as well as a SASE FEL. In this paper, some results of beam dynamics simulation for the SASE option are given at first which includes the parameters selection for the bunch compressors, RF parameters calculation for the accelerating modules and the beam dynamics simulation taking into account the collective effects. Beam dynamics simulation for a single stage HGHG option is based on the work for the SASE option. Electron bunches with low uncorrelated energy spread and small energy chirp are obtained after parameters optimization. The FEL simulation results show that 33.6 nm wavelength FEL radiation with high monochromaticity can be seeded at FLASH2 with a 235 nm seeding laser.

TUPP078

High Gain FEL with a Micro-bunch Structured Beam by the Transverse-Longitudinal Phase Space Rotation

cavity, radiation, electron, cathode

607

M. Kuriki, Y. Seimiya
HU/AdSM, Higashi-Hiroshima, Japan
H. Hayano, K. Ohmi
KEK, Ibaraki, Japan
S. Kashiwagi
Tohoku University, Research Center for Electron Photon Science, Sendai, Japan
R. Kato
ISIR, Osaka, Japan

FEL is one of the ideal radiation source over the wide range of wavelength region with a high brightness and a high coherence. Many methods to improve FEL gain has been proposed by introducing an active modulation on the bunch charge distribution. The transverse-longitudinal phase-space rotation is one of the promising method to realize the density modulation as the micro-bunch structure. Initially, a beam density modulation in the transverse direction made by a mechanical slit, is properly transformed into the density modulation in the longitudinal direction by the phase-space rotation. That results the longitudinal micro-bunch structure. The micro-bunch structure made with this method has a large tunability by changing the slit geometry, the beam line design, and the beam dynamics tuning. A compact FEL facility based on this method is proposed.

Poster TUPP078 [0.594 MB]

TUPP122

Roughness Tolerances in the Undulator Vacuum Chamber of LCLS-II

impedance, undulator, vacuum, wakefield

708

K.L.F. Bane, G.V. Stupakov
SLAC, Menlo Park, California, USA

Funding: Work supported by Department of Energy contract DE–AC02–76SF00515.
In LCLS-II, after acceleration and compression and just before entering the undulator, the beam passes through roughly 2.5 km of 24.5 mm (radius) stainless steel pipe. The bunch that passes through the pipe is extremely short with an rms of 8 um for the nominal 100 pC case. Thus, even though the pipe has a large aperture, the wake that applies is the short-range resistive wall wakefield. It turns out that the wake supplies needed dechirping to the LCLS-II beam before it enters the undulator. The LCLS-II bunch distribution is approximately uniform, and therefore the wake induced voltage is characterized by a rather linear voltage chirp for short bunches. However for bunches longer than 25 um (300 pC at 1 kA) the wake starts to become nonlinear, effectively limiting the maximum charge with which the LCLS-II can operate. In this note we calculate the wake, discuss the confidence in the calculation, and investigate how to improve the induced chirp linearity and/or strength. Finally, we also study the strength and effects of the transverse (dipole) resistive wall wakefield.

TUPP127

R&D of X-band Accelerating Structure for Compact XFEL at SINAP

linac, simulation, wakefield, radiation

715

W. Fang, Q. Gu, M. Zhang, Z.T. Zhao
SINAP, Shanghai, People's Republic of China
A.A. Aksoy, O. Yavaş
Ankara University, Accelerator Technologies Institute, Golbasi / Ankara, Turkey
D. Angal-Kalinin, J.A. Clarke
Cockcroft Institute, Warrington, Cheshire, United Kingdom
C.J. Bocchetta, A.I. Wawrzyniak
Solaris, Kraków, Poland
M.J. Boland
SLSA, Clayton, Australia
G. D'Auria, S. Di Mitri, C. Serpico
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
T.J.C. Ekelöf, R.J.M.Y. Ruber, V.G. Ziemann
Uppsala University, Uppsala, Sweden
E.N. Gazis
National Technical University of Athens, Athens, Greece
A. Grudiev, A. Latina, D. Schulte, S. Stapnes, W. Wuensch
CERN, Geneva, Switzerland

One compact hard X-ray FEL facility is being planned at SINAP, and X-band high gradient accelerating structure is the most competetive scheme for this plan. X-band accelerating structure is designed to switch between 60MV/m and 80MV/m, and carries out 6GeV and 8GeV by 130 meters linac respectively. In this paper, brief layout of compact XFEL will be introduced, and in particular the prototype design of dedicated X-band acceleration RF system is also presented.

TUPP128

ECHO-enabled Tunable Terahertz Radiation Generation with a Laser-modulated Relativistic Electron Beam

laser, radiation, electron, simulation

719

D. Huang, Q. Gu, Z. Wang, Z.T. Zhao
SINAP, Shanghai, People's Republic of China
D. Xiang
Shanghai Jiao Tong University, Shanghai, People's Republic of China

A new scheme to generate narrow-band tunable Terahertz (THz) radiation using a variant of the echo-enabled harmonic generation is analyzed. We show that by using an energy chirped beam, THz density modulation in the beam phase space can be produced with two lasers having the same wavelength. This removes the need for an optical parametric amplifier system to provide a wavelength-tunable laser to vary the central frequency of the THz radiation. The practical feasibility and applications of this scheme is demonstrated numerically with a start-to-end simulation using the beam parameters at Shanghai Deep Ultraviolet Free-Electron Laser facility (SDUV). The central frequency of the density modulation can be continuously tuned by either varying the chirp of the beam or the momentum compactions of the chicanes. The influence of nonlinear RF chirp and longitudinal space charge effect have also been studied in our article. We also briefly discuss how one may retrieve the beam longitudinal phase space through measurement of the THz density modulation. \end{abstract}

THIOB03

Results From the LCLS X-Band Transverse Deflector With Femtosecond Temporal Resolution

electron, undulator, photon, diagnostics

819

Y. Ding, F.-J. Decker, V.A. Dolgashev, J.C. Frisch, Z. Huang, P. Krejcik, H. Loos, A. Lutmann, A. Marinelli, T.J. Maxwell, D.F. Ratner, J.L. Turner, J.W. Wang, M.-H. Wang, J.J. Welch, J. Wu
SLAC, Menlo Park, California, USA
C. Behrens
DESY, Hamburg, Germany

An X-band RF transverse deflector composed of two 1-m-long X-band deflecting structures has been recently commissioned at the Linac Coherent Light Source (LCLS) at SLAC National Accelerator Laboratory. Located downstream of the FEL undulator, this device provides electron beam longitudinal phase space diagnostics in both time and energy which enables reconstruction of the X-ray FEL power profiles with an unprecedented resolution. This talk reports on the progress of this new LCLS X-band transverse deflector, first usage experience and measured results.

Slides THIOB03 [3.508 MB]

THPP084

Cyclotron-Undulator Cooling of Electron Beams

undulator, electron, cyclotron, simulation

1041

S.V. Kuzikov, I.V. Bandurkin, A.V. Savilov
IAP/RAS, Nizhny Novgorod, Russia
A.V. Savilov
NNGU, Nizhny Novgorod, Russia

XFELs require high-quality electron beams which can be produced in damping rings. For XFEL, based on Compton scattering of laser light, instead of the damping ring we consider a new compact device where electrons move in the undulator with axial DC magnetic field. In this undulator electrons move near resonant condition, rotating with cyclotron frequency and wiggling at similar bounce frequency. Such undulator allows compensation of the initial velocity spread by perturbations of the longitudinal velocities caused by transverse wiggling. Calculation show that ~1% velocity spread of 5 MeV electron beam (typical for photoinjectors) can be reduced to ~0.01% at distance as long as 20 undulator periods. In the advanced scheme, where the described undulators alternate with sections of the cyclotron radiation, energy spread as small as 0.001% is reachable. Calculations show that this principle works also for high energy beams (100 MeV and more), where RF undulator instead of DC-magnet undulator is preferable.

Poster THPP084 [0.713 MB]

THPP121

Injector System for the IR-FEL at RRCAT

beam-loading, linac, electron, cavity

1137

L. Faillace, R.B. Agustsson
RadiaBeam, Santa Monica, California, USA
A. Kumar, K.K. Pant
RRCAT, Indore (M.P.), India

An infrared (IR) free-electron laser (FEL) has been proposed to be built at the Raja Ramanna Centre for Advanced Technology (RRCAT). RadiaBeam is currently involved in the design of the RRCAT FEL's injector system. The injector will deliver an electron beam with a variable energy (from 15 up to 40 MeV) and 1.5 nC at 36.6 MHz repetition rate. We show here the beam dynamics of the beam transport through the injector as well as the RF design and mechanical model of the system.
* S. Krishnagopal et al., PRELIMINARY DESIGN OF THE PROPOSED IR-FEL IN INDIA, RRCAT, Indore, M.P. 452013, India

FRIOB01

Positive Trends in Radiation Risk Assessment and Consequent Opportunities for Linac Applications

radiation, linac, controls, simulation

1202

Y. Socol
Falcon Analytics, Netanya, Israel

Ionizing radiation, an unavoidable by-product of high-energy LINACs, makes them subject to strict regulation and severe public concerns. During the last two decades the attitude to ionizing radiation hazards has been becoming more balanced, as opposed to the historical "radiophobia". The linear no-threshold hypothesis (LNTH), based on the assumption that every radiation dose increment constitutes increased cancer risk for humans, is more and more debated. In particular, the recent memorandum of the International Commission on Radiological Protection admits that the LNTH predictions at low doses are "speculative, unproven, undetectable and "phantom'." Moreover, numerous experimental, ecological, and epidemiological studies show that low doses of ionizing radiation may be beneficial to human health. While these advances in scientific understanding have not yet given fruit regarding radiation regulation and policy, we are hopeful these may happen in near to middle term. The presentation reviews the present status of the low-dose radiation-hazard debate. It also outlines anticipated opportunities for LINAC applications, especially in the prospective field of low-dose radiation therapy.

Slides FRIOB01 [1.890 MB]