FEL2012 - List of Authors (Klose, K.)

Paper	Title	Page
TUPD32	Simultaneous Operation of a Multi Beamline FEL Facility	301
	B. Faatz, S. Ackermann, V. Ayvazyan, W. Decking, C. Grün, K. Klose, F. Obier, S. Pfeiffer, M. Scholz, J. Wortmann DESY, Hamburg, Germany E. Hass Uni HH, Hamburg, Germany
	The FLASH II project will add an undulator beamline and a new experimental Hall to the existing FLASH Facility. In addition to improving the radiation properties of the FEL by using seeding, one of the main goals is to double the beamtime of the facility for users. At the moment, we deliver photon pulses in 10 Hz bursts with up to 800 bunches within each RF pulse. In order not to limit parameter ranges, we will have to give those same tuning possibilities within an RF pulse for each of the users independently. For this purpose, several tests have been performed to determine the limits of the difference in beam parameters which can be delivered. We will show to what extend we can switch fast between two beamlines, how we can change photon pulse length by allowing different charges, have different energy in the two beamlines simultaneously to allow for wavelength scans for the fixed-gap undulator presently built in FLASH, while not interfering with user operation of the new beamline.

WEPD08	Upgrades of the Photoinjector Laser System at FLASH	385
	S. Schreiber, C. Grün, O. Hensler, K. Klose, S. Schulz, T. Schulz, M. Staack DESY, Hamburg, Germany M. Groß, G. Klemz, G. Koss DESY Zeuthen, Zeuthen, Germany I.H. Templin, I. Will, H. Willert MBI, Berlin, Germany
	The photoinjector of FLASH uses an RF gun equipped with caesium telluride photocathodes illuminated by appropriate UV laser pulses as a source of ultra-bright electron beams. The superconducting accelerator of FLASH is able to accelerate a 0.8 ms long train of thousands of electron bunches in a burst mode. This puts special demands on the design of the electron source, especially the laser system. The construction of a second undulator beamline FLASH2 has started. The pulse train will be divided into two parts to serve both beamlines simultaneously. Since experiments with the FLASH soft X-ray beam need flexibility, we plan to use two laser systems each serving one beamline. This makes it possible to deliver two trains with different properties in charge, number of bunches, and bunch spacing in the same RF pulse. This also required an upgrades of the laser beamline design. We report on improvements of the laser beamline and first tests operating two lasers simultaneously at FLASH.

THPD33	Generation of Ultra-short Electron Bunches at FLASH	610
	J. Rönsch-Schulenburg, E. Hass, A. Kuhl, T. Plath, M. Rehders, J. Roßbach Uni HH, Hamburg, Germany A. Angelovski, R. Jakoby, A. Penirschke TU Darmstadt, Darmstadt, Germany N. Baboi, M. Bousonville, M.K. Czwalinna, C. Gerth, K. Klose, T. Limberg, U. Mavrič, H. Schlarb, B. Schmidt, S. Schreiber, B. Steffen, C. Sydlo, S. Vilcins, S. Wesch DESY, Hamburg, Germany S. Schnepp, T. Weiland TEMF, TU Darmstadt, Darmstadt, Germany
	Funding: The work is supported by German Federal Ministry of Education and Research (BMBF) within Joint Project - FSP 301 under the contract number 05K10GU2. In order to produce radiation pulses of a few femtoseconds at FELs like FLASH, different concepts have been proposed. Probably the most robust method is to create an electron bunch, which is in the most extreme case as short as one longitudinal optical mode. For FLASH this translates into a bunch length of a few micrometers only. In order to mitigate space charge effects, the bunch charge needs to be about 20 pC. The technical requirements to achieve this goal are discussed. This includes beam dynamics studies to optimize the injection and compression of small charge electron bunches. A reduced photo injector laser pulse duration helps to relax the RF tolerance which scales linear with the compression factor. A new photo injector laser with sub-picosecond pulse duration in combination with a stretcher is used to optimize the initial bunch length. The commissioning of the new laser system and first experiments are described. Limitations of the presently available electron beam diagnostics at FLASH for short, low charge bunches are analyzed. Improvements of the longitudinal phase space diagnostics and the commissioning of a more sensitive beam arrival time monitor are described.

Paper

Title

Page

Simultaneous Operation of a Multi Beamline FEL Facility

301

B. Faatz, S. Ackermann, V. Ayvazyan, W. Decking, C. Grün, K. Klose, F. Obier, S. Pfeiffer, M. Scholz, J. Wortmann
DESY, Hamburg, Germany
E. Hass
Uni HH, Hamburg, Germany

The FLASH II project will add an undulator beamline and a new experimental Hall to the existing FLASH Facility. In addition to improving the radiation properties of the FEL by using seeding, one of the main goals is to double the beamtime of the facility for users. At the moment, we deliver photon pulses in 10 Hz bursts with up to 800 bunches within each RF pulse. In order not to limit parameter ranges, we will have to give those same tuning possibilities within an RF pulse for each of the users independently. For this purpose, several tests have been performed to determine the limits of the difference in beam parameters which can be delivered. We will show to what extend we can switch fast between two beamlines, how we can change photon pulse length by allowing different charges, have different energy in the two beamlines simultaneously to allow for wavelength scans for the fixed-gap undulator presently built in FLASH, while not interfering with user operation of the new beamline.

WEPD08

Upgrades of the Photoinjector Laser System at FLASH

385

S. Schreiber, C. Grün, O. Hensler, K. Klose, S. Schulz, T. Schulz, M. Staack
DESY, Hamburg, Germany
M. Groß, G. Klemz, G. Koss
DESY Zeuthen, Zeuthen, Germany
I.H. Templin, I. Will, H. Willert
MBI, Berlin, Germany

The photoinjector of FLASH uses an RF gun equipped with caesium telluride photocathodes illuminated by appropriate UV laser pulses as a source of ultra-bright electron beams. The superconducting accelerator of FLASH is able to accelerate a 0.8 ms long train of thousands of electron bunches in a burst mode. This puts special demands on the design of the electron source, especially the laser system. The construction of a second undulator beamline FLASH2 has started. The pulse train will be divided into two parts to serve both beamlines simultaneously. Since experiments with the FLASH soft X-ray beam need flexibility, we plan to use two laser systems each serving one beamline. This makes it possible to deliver two trains with different properties in charge, number of bunches, and bunch spacing in the same RF pulse. This also required an upgrades of the laser beamline design. We report on improvements of the laser beamline and first tests operating two lasers simultaneously at FLASH.

THPD33

Generation of Ultra-short Electron Bunches at FLASH

610

J. Rönsch-Schulenburg, E. Hass, A. Kuhl, T. Plath, M. Rehders, J. Roßbach
Uni HH, Hamburg, Germany
A. Angelovski, R. Jakoby, A. Penirschke
TU Darmstadt, Darmstadt, Germany
N. Baboi, M. Bousonville, M.K. Czwalinna, C. Gerth, K. Klose, T. Limberg, U. Mavrič, H. Schlarb, B. Schmidt, S. Schreiber, B. Steffen, C. Sydlo, S. Vilcins, S. Wesch
DESY, Hamburg, Germany
S. Schnepp, T. Weiland
TEMF, TU Darmstadt, Darmstadt, Germany

Funding: The work is supported by German Federal Ministry of Education and Research (BMBF) within Joint Project - FSP 301 under the contract number 05K10GU2.
In order to produce radiation pulses of a few femtoseconds at FELs like FLASH, different concepts have been proposed. Probably the most robust method is to create an electron bunch, which is in the most extreme case as short as one longitudinal optical mode. For FLASH this translates into a bunch length of a few micrometers only. In order to mitigate space charge effects, the bunch charge needs to be about 20 pC. The technical requirements to achieve this goal are discussed. This includes beam dynamics studies to optimize the injection and compression of small charge electron bunches. A reduced photo injector laser pulse duration helps to relax the RF tolerance which scales linear with the compression factor. A new photo injector laser with sub-picosecond pulse duration in combination with a stretcher is used to optimize the initial bunch length. The commissioning of the new laser system and first experiments are described. Limitations of the presently available electron beam diagnostics at FLASH for short, low charge bunches are analyzed. Improvements of the longitudinal phase space diagnostics and the commissioning of a more sensitive beam arrival time monitor are described.