DIPAC2011 - List of Authors (Noelle, D.)

Paper

Title

Page

Electron Beam Diagnostics for FLASH II

53

N. Baboi, D. Nölle
DESY, Hamburg, Germany

Up to now, the FLASH linac serves one SASE (Self-Amplified Spontaneous Emission) undulator. The radiation produced can be guided to one of 5 beamlines in the experimental hall. In order to increase the availability of the machine, an extension, FLASH II, will be built in the next few years. A second undulator section will be built to generate SASE light. A HHG (High Harmonic Generation) laser will alternatively be used to produce seeded radiation in the undulators. The electron beam diagnostics in FLASH II has to enable the precise control of the beam position, size, timing, as well as the overlap of the electron beam with the HHG laser. The losses have to be kept under control, and the beam has to terminate safely in the beam dump. In comparison to FLASH, which was designed to run with rather high charge, the dynamic range of the diagnostics has to be between 0.1 to 1 nC, similar to the European XFEL. This paper gives an overview of the diagnostics for FLASH II.

MOPD19

Button BPM Development for the European XFEL

83

D. Lipka, B. Lorbeer, D. Nölle, M. Siemens, S. Vilcins
DESY, Hamburg, Germany

Button beam position monitors will be the main BPM type used to measure the electron beam position at the European XFEL. Two different kinds of buttons are necessary: one type will be installed in the acceleration modules of the cold linac and the other in the warm environment. The electro-magnetic design of the feedthrough for both types of buttons will be discussed. A comparison of the designed and measured RF properties will be presented. In addition to the usual RF properties, also the properties at cryogenic level will play a role. HOM power must not heat up the BPM feedthroughs, in order to keep the cryo load of an overall accelerator module low, and also to prevent damage due to large temperature gradients over the ceramics of the feedthrough. First measurements with beam at FLASH show good agreement of the measured signals with the expectation.

TUPD43

XFEL Beam Loss Monitor System

401

A. Kaukher, I. Krouptchenkov, B. Michalek, D. Nölle, H. Tiessen
DESY, Hamburg, Germany

European XFEL will have a sophisticated Machine Protection System, part of which - Beam Loss Monitors(BLM). The monitors will detect losses of electron beam, in order to protect the components of the XFEL from damage and excessive activation. For protection of undulators, BLMs with a scintillator bar will be used. BLMs at places with high radiation load will be equipped with fused silica rods. Beam dumps of the XFEL will be instrumented with glass-fiber BLMs. The BLMs were tested with an electron test-beam at DESY, as well as at FLASH. Due to large amount of light produced by scintillator and high gain of the used photomultiplier, no optical grease is needed in front of the photomultiplier' window, while typical cathode voltage is only 500-600 volt. The prototype with quartz glass was typically operated at higher cathode voltage. Good operation of all three types of BLMs prototypes was obtained. It is planned to use same monitors also for the FLASH2 project. Current status of the XFEL BLM system development will be presented.

WEOC03

Dark Current Monitor for the European XFEL

572

D. Lipka, W. Kleen, J. Lund-Nielsen, D. Nölle, S. Vilcins, V. Vogel
DESY, Hamburg, Germany

Dark current is produced due from field emission in the accelerator. This generates a radiation background in the tunnel which damages the electronics and activates components. To decrease the dark current different methods like kickers and collimators are used. To control the dark current level and measure and optimize the efficiency of dark current reduction dark current monitors are required. To measure the dark current a cavity was designed and built with the operation frequency of the accelerator. Here the small charge of the dark current present in every RF bucket induces and superimposes a field up to a measurable level. The cavity is proven at the PITZ facility. In addition to dark current levels down to 50 nA, the monitor allows for charge measurements resolution below pC, better than the Faraday cup. In addition the ratio of amplitudes from higher order monopole modes is a function of the bunch length. Measurements show the same trend of bunch length compared with a destructive streak camera method with comparable resolution. Therefore this monitor is able to measure bunch charge, dark current and bunch length in a non-destructive manner.

Slides WEOC03 [0.935 MB]

Paper	Title	Page
MOPD09	Electron Beam Diagnostics for FLASH II	53
	N. Baboi, D. Nölle DESY, Hamburg, Germany
	Up to now, the FLASH linac serves one SASE (Self-Amplified Spontaneous Emission) undulator. The radiation produced can be guided to one of 5 beamlines in the experimental hall. In order to increase the availability of the machine, an extension, FLASH II, will be built in the next few years. A second undulator section will be built to generate SASE light. A HHG (High Harmonic Generation) laser will alternatively be used to produce seeded radiation in the undulators. The electron beam diagnostics in FLASH II has to enable the precise control of the beam position, size, timing, as well as the overlap of the electron beam with the HHG laser. The losses have to be kept under control, and the beam has to terminate safely in the beam dump. In comparison to FLASH, which was designed to run with rather high charge, the dynamic range of the diagnostics has to be between 0.1 to 1 nC, similar to the European XFEL. This paper gives an overview of the diagnostics for FLASH II.

MOPD19	Button BPM Development for the European XFEL	83
	D. Lipka, B. Lorbeer, D. Nölle, M. Siemens, S. Vilcins DESY, Hamburg, Germany
	Button beam position monitors will be the main BPM type used to measure the electron beam position at the European XFEL. Two different kinds of buttons are necessary: one type will be installed in the acceleration modules of the cold linac and the other in the warm environment. The electro-magnetic design of the feedthrough for both types of buttons will be discussed. A comparison of the designed and measured RF properties will be presented. In addition to the usual RF properties, also the properties at cryogenic level will play a role. HOM power must not heat up the BPM feedthroughs, in order to keep the cryo load of an overall accelerator module low, and also to prevent damage due to large temperature gradients over the ceramics of the feedthrough. First measurements with beam at FLASH show good agreement of the measured signals with the expectation.

TUPD43	XFEL Beam Loss Monitor System	401
	A. Kaukher, I. Krouptchenkov, B. Michalek, D. Nölle, H. Tiessen DESY, Hamburg, Germany
	European XFEL will have a sophisticated Machine Protection System, part of which - Beam Loss Monitors(BLM). The monitors will detect losses of electron beam, in order to protect the components of the XFEL from damage and excessive activation. For protection of undulators, BLMs with a scintillator bar will be used. BLMs at places with high radiation load will be equipped with fused silica rods. Beam dumps of the XFEL will be instrumented with glass-fiber BLMs. The BLMs were tested with an electron test-beam at DESY, as well as at FLASH. Due to large amount of light produced by scintillator and high gain of the used photomultiplier, no optical grease is needed in front of the photomultiplier' window, while typical cathode voltage is only 500-600 volt. The prototype with quartz glass was typically operated at higher cathode voltage. Good operation of all three types of BLMs prototypes was obtained. It is planned to use same monitors also for the FLASH2 project. Current status of the XFEL BLM system development will be presented.

WEOC03	Dark Current Monitor for the European XFEL	572
	D. Lipka, W. Kleen, J. Lund-Nielsen, D. Nölle, S. Vilcins, V. Vogel DESY, Hamburg, Germany
	Dark current is produced due from field emission in the accelerator. This generates a radiation background in the tunnel which damages the electronics and activates components. To decrease the dark current different methods like kickers and collimators are used. To control the dark current level and measure and optimize the efficiency of dark current reduction dark current monitors are required. To measure the dark current a cavity was designed and built with the operation frequency of the accelerator. Here the small charge of the dark current present in every RF bucket induces and superimposes a field up to a measurable level. The cavity is proven at the PITZ facility. In addition to dark current levels down to 50 nA, the monitor allows for charge measurements resolution below pC, better than the Faraday cup. In addition the ratio of amplitudes from higher order monopole modes is a function of the bunch length. Measurements show the same trend of bunch length compared with a destructive streak camera method with comparable resolution. Therefore this monitor is able to measure bunch charge, dark current and bunch length in a non-destructive manner.
	Slides WEOC03 [0.935 MB]