FEL2014 - List of Authors (Saldin, E.)

Paper	Title	Page
MOP056	SASE Characteristics from Baseline European XFEL Undulators in the Tapering Regime	159
	I.V. Agapov, G. Geloni XFEL. EU, Hamburg, Germany G. Feng, V. Kocharyan, E. Saldin, S. Serkez, I. Zagorodnov DESY, Hamburg, Germany
	The output SASE characteristics of the baseline European XFEL, recently used in the TDRs of scientific instruments and X-ray optics, have been previously optimized assuming uniform undulators without considering the potential of undulator tapering in the SASE regime. Here we demonstrate that the performance of European XFEL sources can be significantly improved without additional hardware. The procedure consists in the optimization of the undulator gap configuration for each X-ray beamline. Here we provide a comprehensive description of the X-ray photon beam properties as a function of wavelength and bunch charge. Based on nominal parameters for the electron beam, we demonstrate that undulator tapering allows one to achieve up to a tenfold increase in peak power and photon spectral density in the conventional SASE regime.

MOP057	Proposal to Generate 10 TW Level Femtosecond X-ray Pulses from a Baseline Undulator in Conventional SASE Regime at the European XFEL	164
	E. Saldin, V. Kocharyan, S. Serkez, I. Zagorodnov DESY, Hamburg, Germany G. Geloni XFEL. EU, Hamburg, Germany
	Output characteristics of the European XFEL have been previously studied assuming an operation point at 5 kA peak current. Here we explore the possibility to go well beyond such nominal peak current level. We consider a bunch with 0.25 nC charge, compressed up to a peak current of 45 kA. An advantage of operating at such high peak current is the increase of the x-ray output peak power without any modification to the baseline design. Based on start-to-end simulations, we demonstrate that such high peak current, combined with undulator tapering, allows one to achieve up to a 100-fold increase in a peak power in the conventional SASE regime, compared to the nominal mode of operation. In particular, we find that 10 TW-power level, femtosecond x-ray pulses can be generated in the photon energy range between 3 keV and 5 keV, which is optimal for single biomolecule imaging. Our simulations are based on the exploitation of all the 21 cells foreseen for the SASE3 undulator beamline, and indicate that one can achieve diffraction to the desired resolution with 15 mJ (corresponding to about 3·10¹³ photons) in pulses of about 3 fs, in the case of a 100 nm focus at the photon energy of 3.5 keV.

MOP058	Purified SASE Undulator Configuration to Enhance the Performance of the Soft X-ray Beamline at the European XFEL	169
	V. Kocharyan, E. Saldin, S. Serkez, I. Zagorodnov DESY, Hamburg, Germany I.V. Agapov, G. Geloni XFEL. EU, Hamburg, Germany
	The purified SASE (pSASE) undulator configuration recently proposed at SLAC promises an increase in the output spectral density of XFELs. In this article we study a straightforward implementation of this configuration for the soft x-ray beamline at the European XFEL. A few undulator cells, resonant at a subharmonic of the FEL radiation, are used in the middle of the exponential regime to amplify the radiation, while simultaneously reducing the FEL bandwidth. Based on start-to-end simulations, we show that with the proposed configuration the spectral density in the photon energy range between 1.3 keV and 3 keV can be enhanced of an order of magnitude compared to the baseline mode of operation. This option can be implemented into the tunable-gap SASE3 baseline undulator without additional hardware, and it is complementary to the self-seeding option with grating monochromator proposed for the same undulator line, which can cover the photon energy range between about 0.26 keV and 1 keV.

MOP082	Perspectives for Imaging Single Protein Molecules with the Present Design of the European XFEL	238
	G. Geloni XFEL. EU, Hamburg, Germany V. Kocharyan, E. Saldin, S. Serkez, I. Zagorodnov DESY, Hamburg, Germany O. Yefanov CFEL, Hamburg, Germany
	European XFEL aims to support imaging and structure determination of biological specimens between less than 0.1 microns and 1 micron size with working photon energies between 3 keV and 16 keV. This wide operation range is a cause for challenges to the focusing optics. A long propagation distance of about 900 m between x-ray source and sample leads to a large lateral photon beam size at the optics. Due to the large divergence of nominal X-ray pulses with durations shorter than 10 fs, one suffers diffraction from mirror apertures, leading to a 100-fold decrease in fluence at photon energies around 4 keV, which seem ideal for imaging of single biomolecules. Moreover, the nominal SASE1 is very far from the level required for single particle imaging. Here we show how it may be possible to optimize the SPB instrument for single biomolecule imaging with minimal additional costs and time, achieving diffraction without destruction at near-atomic resolution with 10¹³ photons in a 4 fs pulse at 4 keV photon energy and in a 100 nm focus, corresponding to a fluence of 10²³ ph/cm². This result is exemplified using the RNA Pol II molecule as a case study.

Paper

Title

Page

SASE Characteristics from Baseline European XFEL Undulators in the Tapering Regime

159

I.V. Agapov, G. Geloni
XFEL. EU, Hamburg, Germany
G. Feng, V. Kocharyan, E. Saldin, S. Serkez, I. Zagorodnov
DESY, Hamburg, Germany

The output SASE characteristics of the baseline European XFEL, recently used in the TDRs of scientific instruments and X-ray optics, have been previously optimized assuming uniform undulators without considering the potential of undulator tapering in the SASE regime. Here we demonstrate that the performance of European XFEL sources can be significantly improved without additional hardware. The procedure consists in the optimization of the undulator gap configuration for each X-ray beamline. Here we provide a comprehensive description of the X-ray photon beam properties as a function of wavelength and bunch charge. Based on nominal parameters for the electron beam, we demonstrate that undulator tapering allows one to achieve up to a tenfold increase in peak power and photon spectral density in the conventional SASE regime.

MOP057

Proposal to Generate 10 TW Level Femtosecond X-ray Pulses from a Baseline Undulator in Conventional SASE Regime at the European XFEL

164

E. Saldin, V. Kocharyan, S. Serkez, I. Zagorodnov
DESY, Hamburg, Germany
G. Geloni
XFEL. EU, Hamburg, Germany

Output characteristics of the European XFEL have been previously studied assuming an operation point at 5 kA peak current. Here we explore the possibility to go well beyond such nominal peak current level. We consider a bunch with 0.25 nC charge, compressed up to a peak current of 45 kA. An advantage of operating at such high peak current is the increase of the x-ray output peak power without any modification to the baseline design. Based on start-to-end simulations, we demonstrate that such high peak current, combined with undulator tapering, allows one to achieve up to a 100-fold increase in a peak power in the conventional SASE regime, compared to the nominal mode of operation. In particular, we find that 10 TW-power level, femtosecond x-ray pulses can be generated in the photon energy range between 3 keV and 5 keV, which is optimal for single biomolecule imaging. Our simulations are based on the exploitation of all the 21 cells foreseen for the SASE3 undulator beamline, and indicate that one can achieve diffraction to the desired resolution with 15 mJ (corresponding to about 3·10¹³ photons) in pulses of about 3 fs, in the case of a 100 nm focus at the photon energy of 3.5 keV.

MOP058

Purified SASE Undulator Configuration to Enhance the Performance of the Soft X-ray Beamline at the European XFEL

169

V. Kocharyan, E. Saldin, S. Serkez, I. Zagorodnov
DESY, Hamburg, Germany
I.V. Agapov, G. Geloni
XFEL. EU, Hamburg, Germany

The purified SASE (pSASE) undulator configuration recently proposed at SLAC promises an increase in the output spectral density of XFELs. In this article we study a straightforward implementation of this configuration for the soft x-ray beamline at the European XFEL. A few undulator cells, resonant at a subharmonic of the FEL radiation, are used in the middle of the exponential regime to amplify the radiation, while simultaneously reducing the FEL bandwidth. Based on start-to-end simulations, we show that with the proposed configuration the spectral density in the photon energy range between 1.3 keV and 3 keV can be enhanced of an order of magnitude compared to the baseline mode of operation. This option can be implemented into the tunable-gap SASE3 baseline undulator without additional hardware, and it is complementary to the self-seeding option with grating monochromator proposed for the same undulator line, which can cover the photon energy range between about 0.26 keV and 1 keV.

MOP082

Perspectives for Imaging Single Protein Molecules with the Present Design of the European XFEL

238

G. Geloni
XFEL. EU, Hamburg, Germany
V. Kocharyan, E. Saldin, S. Serkez, I. Zagorodnov
DESY, Hamburg, Germany
O. Yefanov
CFEL, Hamburg, Germany

European XFEL aims to support imaging and structure determination of biological specimens between less than 0.1 microns and 1 micron size with working photon energies between 3 keV and 16 keV. This wide operation range is a cause for challenges to the focusing optics. A long propagation distance of about 900 m between x-ray source and sample leads to a large lateral photon beam size at the optics. Due to the large divergence of nominal X-ray pulses with durations shorter than 10 fs, one suffers diffraction from mirror apertures, leading to a 100-fold decrease in fluence at photon energies around 4 keV, which seem ideal for imaging of single biomolecules. Moreover, the nominal SASE1 is very far from the level required for single particle imaging. Here we show how it may be possible to optimize the SPB instrument for single biomolecule imaging with minimal additional costs and time, achieving diffraction without destruction at near-atomic resolution with 10¹³ photons in a 4 fs pulse at 4 keV photon energy and in a 100 nm focus, corresponding to a fluence of 10²³ ph/cm². This result is exemplified using the RNA Pol II molecule as a case study.