FEL2012 - List of Authors (Loos, H.)

Paper

Title

Page

First Lasing of the IR FEL at the Fritz-Haber-Institut Berlin

1

W. Schöllkopf, W. Erlebach, S. Gewinner, G. Heyne, H. Junkes, A. Liedke, G. Meijer, V. Platschkowski, W.Q. Zhang, G. von Helden
FHI, Berlin, Germany
H. Bluem, D. Dowell, K. Jordan, R. Lange, J.H. Park, J. Rathke, A.M.M. Todd, L.M. Young
AES, Medford, NY, USA
M.A. Davidsaver
BNL, Upton, New York, USA
S.C. Gottschalk
STI, Washington, USA
U. Lehnert, P. Michel, W. Seidel, R. Wünsch
HZDR, Dresden, Germany
H. Loos
SLAC, Menlo Park, California, USA

An IR and THz FEL with a design wavelength range from 4 to 500 μm has been commissioned at the Fritz-Haber-Institut (FHI) in Berlin, Germany, for applications in, i.a., molecular and cluster spectroscopy as well as surface science.[1] The linac[2] comprises two S-band standing-wave copper structures. The first one operates at near fixed field to accelerate the electrons to 20 MeV, while the second one is designed to accelerate (or decelerate) to any final energy between 15 and 50 MeV. A key aspect of the system is low longitudinal emittance, <50 keV-psec, at more than 200 pC bunch charge with a max.μpulse rep. rate of 1 GHz. The up to 15 μs long macro pulses come at a rate of up to 20 Hz. The electrons are steered through either one of two FELs. A single-plane-focusing, 40 mm period wedged-pole hybrid undulator[3] combined with a 5.4 m long cavity has been commissioned for the mid-IR (<50 μm). In addition, a two-plane-focusing undulator in combination with a 7.2 m long cavity with a 1-d waveguide for the optical mode is planned for the far-IR. In February 2012 we observed 'first lasing' at 28 MeV and 18 μm wavelength. We will present first results characterizing the system.
[1] W. Schöllkopf et al., "Status of the Fritz Haber Institute THz FEL", Paper TUPB30, Proc. FEL 2011.
[2] Advanced Energy Systems, Inc., Medford, NY, USA
[3] STI Optronics, Inc., Bellevue, WA, USA

Slides MOOB01 [3.440 MB]

TUOAI02

Hard X-ray Self-Seeding at the LCLS

R.R. Lindberg, W. Berg, D. Shu, Yu. Shvyd'ko, S. Stoupin, E. Trakhtenberg, A. Zholents
ANL, Argonne, USA
J.W. Amann, F.-J. Decker, Y.T. Ding, Y. Feng, J.C. Frisch, D. Fritz, J.B. Hastings, Z. Huang, J. Krzywinski, H. Loos, A.A. Lutman, H.-D. Nuhn, D.F. Ratner, J.A. Rzepiela, D.R. Walz, J.J. Welch, J. Wu, D. Zhu
SLAC, Menlo Park, California, USA
V.D. Blank, S. Terentiev
TISNCM, Troitsk, Russia
P. Emma
LBNL, Berkeley, California, USA
S. Spampinati
Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy

Funding: U.S. Dept. of Energy Office of Sciences under Contract No. DE-AC02-06CH11357
The Linac Coherent Light Source (LCLS) has produced extremely bright hard x-ray pulses using self-amplified spontaneous emission (SASE) since 2009. In SASE, the electron beam shot noise initiates the FEL gain, resulting in output radiation characterized by poor temporal coherence and a fluctuating spectrum whose normalized width is given by the FEL bandwidth. Recently, colleagues at DESY suggested a self-seeding scheme for the LCLS to reduce the bandwidth*. Here, the SASE produced in the first half of the undulator line is put through a simple diamond-based monochromator; the resulting monochromatic light trailing the main SASE pulse is used to seed the FEL interaction in the downstream undulators. We report on the experimental results implementing such a scheme at the LCLS, in which we have measured a reduction in bandwidth by a factor of 40-50 from that of SASE at 8-9 keV. The self-seeded FEL operates close to saturation, with the maximum output energy approximately equal to that with no seeding for low charge. The observed level of power fluctuations in the seeded output is presently rather large, and future plans focus on discovering their origins and reducing their magnitude.
* Geloni, V. Kocharyan ,and E.L. Saldin, DESY 10-133, arXiv:10⁰⁸.3036 (2010)

Slides TUOAI02 [22.104 MB]

TUOBI01

System Design for Self-Seeding the LCLS at Soft X-ray Energies

205

Y. Feng, J.W. Amann, D. Cocco, R.C. Field, J.B. Hastings, P.A. Heimann, Z. Huang, H. Loos, J.J. Welch, J. Wu
SLAC, Menlo Park, California, USA
K. Chow, P. Emma, L. Rodes, R.W. Schoenlein
LBNL, Berkeley, California, USA

Funding: Portions of this research were carried out at the LCLS at the SLAC. LCLS is an Office of Science User Facility operated for the U.S. DOE Office of Science by Stanford University
The complete design for self-seeding the LCLS at soft X-ray energies from 400 to 1000 eV based on a grating monochromator is described. The X-ray optics system consists of a toroidal variable-line-space (VLS) grating with a resolving power greater than 5000 for creating a nearly transform-limited seed pulse from the upstream SASE undulator for pulse durations of the order of 25 fs, and focusing mirrors for imaging the seed pulse onto the downstream seeding undulator. Diagnostics for ensuring overlap with the reentrant electron beam are included in the design. The optical system is sufficiently compact to fit within a single 3.4 m LCLS undulator segment. The electron chicane system which serves to delay the electron beam to match the less than 1 ps delay from the optical system is similar to the chicane used in the hard X-ray self-seeding at LCLS. The seeded FEL pulse is expected to be nearly transform-limited with a bandwidth in the 10-4 range, potentially increasing the low-charge FEL X-ray peak brightness by 1-2 orders of magnitude.

Slides TUOBI01 [6.749 MB]

TUPD26

Fast Beam-Based BPM Calibration

289

K.J. Bertsche, H. Loos, H.-D. Nuhn, F. Peters
SLAC, Menlo Park, California, USA

Funding: Work supported by the U.S. Department of Energy under contract number DE-AC02-76SF00515.
The Alignment Diagnostic System (ADS) of the LCLS undulator system indicates that the 33 undulator quadrupoles have an extremely high position stability over many weeks. However, beam trajectory straightness and lasing efficiency degrade more quickly than this. A lengthy Beam Based Alignment (BBA) procedure must be executed every two to four weeks to re-optimize the X-ray beam parameters. The undulator system includes RF cavity Beam Position Monitors (RFBPMs), several of which are utilized by an automatic feedback system to align the incoming electron-beam trajectory to the undulator axis. The beam trajectory straightness degradation has been traced to electronic drifts of the gain and offset of the BPMs used in the beam feedback system. To quickly recover the trajectory straightness, we have developed a fast beam-based procedure to recalibrate the BPMs. This procedure takes advantage of the high-precision monitoring capability of the ADS, which allows highly repeatable positioning of undulator quadrupoles. This report describes the ADS, the position stability of the LCLS undulator quadrupoles, and some results of the new recovery procedure.

WEOC04

Accelerator Beamline Performance for the IR FEL at the Fritz-Haber-Institut, Berlin

365

H. Bluem, D. Dowell, J.H. Park, A.M.M. Todd, L.M. Young
AES, Medford, NY, USA
S. Gewinner, W. Schöllkopf
FHI, Berlin, Germany
H. Loos
SLAC, Menlo Park, California, USA

An electron accelerator and beamline for an IR and THz FEL with a design wavelength range from 4 to 500 μm has been commissioned by Advanced Energy Systems at the Fritz-Haber-Institut (FHI) in Berlin, Germany, for applications in, i.a., molecular and cluster spectroscopy as well as surface science. The linac comprises two S-band standing-wave copper structures and was designed to meet challenging specifications, including a final energy adjustable in the range of 15 to 50 MeV, low longitudinal emittance (<50 keV-psec) and transverse emittance (<20 μm), at more than 200 pC bunch charge with aμpulse repetition rate of 1 GHz. First lasing was achieved February 2012. Operational experience and measured electron beam performance will be presented.

Slides WEOC04 [12.785 MB]

THOC04

Femtosecond X-ray Pulse Duration and Separation Measurement using a Cross-Correlation Technique

Y.T. Ding, F.-J. Decker, Z. Huang, H. Loos, J.J. Welch, J. Wu, F. Zhou
SLAC, Menlo Park, California, USA
P. Emma
LBNL, Berkeley, California, USA
C. Feng
SINAP, Shanghai, People's Republic of China

At the Linac Coherent Light Source (LCLS), the emittance-spoiling foil is a very simple and effective method to control the output x-ray pulse duration [*]. In addition, double slotted foil can be used to generate two femotsecond x-ray pulses with variable time delays. In this paper, we report the first measurement of x-ray pulse duration and double x-ray pulse separation by using a cross-correlation technique between x-rays and electrons [**]. The measured pulse separation can be used to calibrate the foil setup, and pulse duration of less than 3 fs rms has been achieved. This technique can be used to provide critical temporal diagnostics for x-ray experiments that employ the emittance-spoiling foil.
[*] P. Emma et al., PRL 92, 074801 (2004).
[**] G. Geloni et al., DESY 10-008.

Slides THOC04 [0.684 MB]

THPD30

Fast, Absolute Bunch Length Measurements in a Linac using an Improved RF-phasing Method

602

P. Emma
LBNL, Berkeley, California, USA
C. Behrens
DESY, Hamburg, Germany
H. Loos
SLAC, Menlo Park, California, USA

Funding: We are grateful to the US Department of Energy under contract number DE-AC02-76SF00515.
There is great demand for a fast, accurate method to measure the absolute bunch length of an electron beam in a linac. Many ideas are available, with one of the most attractive based on the transverse RF deflector*. Since this specialized technology can be costly and unavailable, we introduce an alternate method using accelerating RF with the same robust characteristics (fast, accurate, and absolute). This method is based on the 'RF zero-phasing' scheme**, but includes several significant improvements based on experience with the RF deflector method.
* R. Akre et al., Proc. of PAC-01, p. 2353.
** D. X. Wang et al., Proc. of PAC-97, p. 2020.

Paper	Title	Page
MOOB01	First Lasing of the IR FEL at the Fritz-Haber-Institut Berlin	1
	W. Schöllkopf, W. Erlebach, S. Gewinner, G. Heyne, H. Junkes, A. Liedke, G. Meijer, V. Platschkowski, W.Q. Zhang, G. von Helden FHI, Berlin, Germany H. Bluem, D. Dowell, K. Jordan, R. Lange, J.H. Park, J. Rathke, A.M.M. Todd, L.M. Young AES, Medford, NY, USA M.A. Davidsaver BNL, Upton, New York, USA S.C. Gottschalk STI, Washington, USA U. Lehnert, P. Michel, W. Seidel, R. Wünsch HZDR, Dresden, Germany H. Loos SLAC, Menlo Park, California, USA
	An IR and THz FEL with a design wavelength range from 4 to 500 μm has been commissioned at the Fritz-Haber-Institut (FHI) in Berlin, Germany, for applications in, i.a., molecular and cluster spectroscopy as well as surface science.[1] The linac[2] comprises two S-band standing-wave copper structures. The first one operates at near fixed field to accelerate the electrons to 20 MeV, while the second one is designed to accelerate (or decelerate) to any final energy between 15 and 50 MeV. A key aspect of the system is low longitudinal emittance, <50 keV-psec, at more than 200 pC bunch charge with a max.μpulse rep. rate of 1 GHz. The up to 15 μs long macro pulses come at a rate of up to 20 Hz. The electrons are steered through either one of two FELs. A single-plane-focusing, 40 mm period wedged-pole hybrid undulator[3] combined with a 5.4 m long cavity has been commissioned for the mid-IR (<50 μm). In addition, a two-plane-focusing undulator in combination with a 7.2 m long cavity with a 1-d waveguide for the optical mode is planned for the far-IR. In February 2012 we observed 'first lasing' at 28 MeV and 18 μm wavelength. We will present first results characterizing the system. [1] W. Schöllkopf et al., "Status of the Fritz Haber Institute THz FEL", Paper TUPB30, Proc. FEL 2011. [2] Advanced Energy Systems, Inc., Medford, NY, USA [3] STI Optronics, Inc., Bellevue, WA, USA
	Slides MOOB01 [3.440 MB]

TUOAI02	Hard X-ray Self-Seeding at the LCLS
	R.R. Lindberg, W. Berg, D. Shu, Yu. Shvyd'ko, S. Stoupin, E. Trakhtenberg, A. Zholents ANL, Argonne, USA J.W. Amann, F.-J. Decker, Y.T. Ding, Y. Feng, J.C. Frisch, D. Fritz, J.B. Hastings, Z. Huang, J. Krzywinski, H. Loos, A.A. Lutman, H.-D. Nuhn, D.F. Ratner, J.A. Rzepiela, D.R. Walz, J.J. Welch, J. Wu, D. Zhu SLAC, Menlo Park, California, USA V.D. Blank, S. Terentiev TISNCM, Troitsk, Russia P. Emma LBNL, Berkeley, California, USA S. Spampinati Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
	Funding: U.S. Dept. of Energy Office of Sciences under Contract No. DE-AC02-06CH11357 The Linac Coherent Light Source (LCLS) has produced extremely bright hard x-ray pulses using self-amplified spontaneous emission (SASE) since 2009. In SASE, the electron beam shot noise initiates the FEL gain, resulting in output radiation characterized by poor temporal coherence and a fluctuating spectrum whose normalized width is given by the FEL bandwidth. Recently, colleagues at DESY suggested a self-seeding scheme for the LCLS to reduce the bandwidth. Here, the SASE produced in the first half of the undulator line is put through a simple diamond-based monochromator; the resulting monochromatic light trailing the main SASE pulse is used to seed the FEL interaction in the downstream undulators. We report on the experimental results implementing such a scheme at the LCLS, in which we have measured a reduction in bandwidth by a factor of 40-50 from that of SASE at 8-9 keV. The self-seeded FEL operates close to saturation, with the maximum output energy approximately equal to that with no seeding for low charge. The observed level of power fluctuations in the seeded output is presently rather large, and future plans focus on discovering their origins and reducing their magnitude. Geloni, V. Kocharyan ,and E.L. Saldin, DESY 10-133, arXiv:10⁰⁸.3036 (2010)
	Slides TUOAI02 [22.104 MB]

TUOBI01	System Design for Self-Seeding the LCLS at Soft X-ray Energies	205
	Y. Feng, J.W. Amann, D. Cocco, R.C. Field, J.B. Hastings, P.A. Heimann, Z. Huang, H. Loos, J.J. Welch, J. Wu SLAC, Menlo Park, California, USA K. Chow, P. Emma, L. Rodes, R.W. Schoenlein LBNL, Berkeley, California, USA
	Funding: Portions of this research were carried out at the LCLS at the SLAC. LCLS is an Office of Science User Facility operated for the U.S. DOE Office of Science by Stanford University The complete design for self-seeding the LCLS at soft X-ray energies from 400 to 1000 eV based on a grating monochromator is described. The X-ray optics system consists of a toroidal variable-line-space (VLS) grating with a resolving power greater than 5000 for creating a nearly transform-limited seed pulse from the upstream SASE undulator for pulse durations of the order of 25 fs, and focusing mirrors for imaging the seed pulse onto the downstream seeding undulator. Diagnostics for ensuring overlap with the reentrant electron beam are included in the design. The optical system is sufficiently compact to fit within a single 3.4 m LCLS undulator segment. The electron chicane system which serves to delay the electron beam to match the less than 1 ps delay from the optical system is similar to the chicane used in the hard X-ray self-seeding at LCLS. The seeded FEL pulse is expected to be nearly transform-limited with a bandwidth in the 10-4 range, potentially increasing the low-charge FEL X-ray peak brightness by 1-2 orders of magnitude.
	Slides TUOBI01 [6.749 MB]

TUPD26	Fast Beam-Based BPM Calibration	289
	K.J. Bertsche, H. Loos, H.-D. Nuhn, F. Peters SLAC, Menlo Park, California, USA
	Funding: Work supported by the U.S. Department of Energy under contract number DE-AC02-76SF00515. The Alignment Diagnostic System (ADS) of the LCLS undulator system indicates that the 33 undulator quadrupoles have an extremely high position stability over many weeks. However, beam trajectory straightness and lasing efficiency degrade more quickly than this. A lengthy Beam Based Alignment (BBA) procedure must be executed every two to four weeks to re-optimize the X-ray beam parameters. The undulator system includes RF cavity Beam Position Monitors (RFBPMs), several of which are utilized by an automatic feedback system to align the incoming electron-beam trajectory to the undulator axis. The beam trajectory straightness degradation has been traced to electronic drifts of the gain and offset of the BPMs used in the beam feedback system. To quickly recover the trajectory straightness, we have developed a fast beam-based procedure to recalibrate the BPMs. This procedure takes advantage of the high-precision monitoring capability of the ADS, which allows highly repeatable positioning of undulator quadrupoles. This report describes the ADS, the position stability of the LCLS undulator quadrupoles, and some results of the new recovery procedure.

WEOC04	Accelerator Beamline Performance for the IR FEL at the Fritz-Haber-Institut, Berlin	365
	H. Bluem, D. Dowell, J.H. Park, A.M.M. Todd, L.M. Young AES, Medford, NY, USA S. Gewinner, W. Schöllkopf FHI, Berlin, Germany H. Loos SLAC, Menlo Park, California, USA
	An electron accelerator and beamline for an IR and THz FEL with a design wavelength range from 4 to 500 μm has been commissioned by Advanced Energy Systems at the Fritz-Haber-Institut (FHI) in Berlin, Germany, for applications in, i.a., molecular and cluster spectroscopy as well as surface science. The linac comprises two S-band standing-wave copper structures and was designed to meet challenging specifications, including a final energy adjustable in the range of 15 to 50 MeV, low longitudinal emittance (<50 keV-psec) and transverse emittance (<20 μm), at more than 200 pC bunch charge with aμpulse repetition rate of 1 GHz. First lasing was achieved February 2012. Operational experience and measured electron beam performance will be presented.
	Slides WEOC04 [12.785 MB]

THOC04	Femtosecond X-ray Pulse Duration and Separation Measurement using a Cross-Correlation Technique
	Y.T. Ding, F.-J. Decker, Z. Huang, H. Loos, J.J. Welch, J. Wu, F. Zhou SLAC, Menlo Park, California, USA P. Emma LBNL, Berkeley, California, USA C. Feng SINAP, Shanghai, People's Republic of China
	At the Linac Coherent Light Source (LCLS), the emittance-spoiling foil is a very simple and effective method to control the output x-ray pulse duration []. In addition, double slotted foil can be used to generate two femotsecond x-ray pulses with variable time delays. In this paper, we report the first measurement of x-ray pulse duration and double x-ray pulse separation by using a cross-correlation technique between x-rays and electrons []. The measured pulse separation can be used to calibrate the foil setup, and pulse duration of less than 3 fs rms has been achieved. This technique can be used to provide critical temporal diagnostics for x-ray experiments that employ the emittance-spoiling foil. [] P. Emma et al., PRL 92, 074801 (2004). [**] G. Geloni et al., DESY 10-008.
	Slides THOC04 [0.684 MB]

THPD30	Fast, Absolute Bunch Length Measurements in a Linac using an Improved RF-phasing Method	602
	P. Emma LBNL, Berkeley, California, USA C. Behrens DESY, Hamburg, Germany H. Loos SLAC, Menlo Park, California, USA
	Funding: We are grateful to the US Department of Energy under contract number DE-AC02-76SF00515. There is great demand for a fast, accurate method to measure the absolute bunch length of an electron beam in a linac. Many ideas are available, with one of the most attractive based on the transverse RF deflector. Since this specialized technology can be costly and unavailable, we introduce an alternate method using accelerating RF with the same robust characteristics (fast, accurate, and absolute). This method is based on the 'RF zero-phasing' scheme, but includes several significant improvements based on experience with the RF deflector method. R. Akre et al., Proc. of PAC-01, p. 2353. ** D. X. Wang et al., Proc. of PAC-97, p. 2020.