Paper |
Title |
Page |
MOPCH016 |
Bunch Compression Monitor
|
86 |
|
- H. Delsim-Hashemi, J. Rossbach, P. Schmüser
Uni HH, Hamburg
- O. Grimm, H. Schlarb, B. Schmidt
DESY, Hamburg
- A.F.G. van der Meer
FOM Rijnhuizen, Nieuwegein
|
|
|
An accelerated bunch of electrons radiates coherently at wavelengths longer than or comparable to the bunch length. The first generation Bunch Compression Monitor (BCM) that is installed at the VUV-FEL applies this principle by measuring the total radiation intensity. For a better control on the degree of the compression, the radiated intensity in different bandwidth can be used. Dependent on the changes in the structure of the bunch, its radiation spectrum changes correspondingly. A new generation BCM uses wavelength dependent diffracting devices and multi-channel sensors to measure the signal in different wavelength channels simultaneously. This paper describes the construction of the first prototypes and experimental results in different short wavelength bands measured at the linac of the VUV-FEL at DESY, Hamburg.
|
|
TUPCH024 |
Comparative Study of Bunch Length and Arrival Time Measurements at FLASH
|
1049 |
|
- H. Schlarb, A. Azima, S. Düsterer, M. Huening, E.-A. Knabbe, M. Roehrs, R. Rybnikov, B. Schmidt, B. Steffen
DESY, Hamburg
- M.C. Ross
SLAC, Menlo Park, California
- P. Schmüser, A. Winter
Uni HH, Hamburg
|
|
|
Diagnostic devices to precisely measure the longitudinal electron beam profile and the bunch arrival time require elaborate new instrumentation techniques. At the VUV-FEL, two entirely different methods are used. The bunch profile can be determined with high precision by a transverse deflecting RF structure. The method is disruptive and does not allow to monitor multiple bunches in a macro-pulse train. Therefore, it is augmented by two non-disruptive electro-optical devices, called EO and TEO. The EO setup uses a dedicated diagnostic laser synchronized to the machine RF. The longitudinal electron beam profile is encoded in the intensity profile of a chirped laser pulse and analyzed by looking at the spectral composition of the pulse. The second setup, TEO, utilizes the TiSa-based laser system used for pump-probe experiments. Here, the temporal electron shape is encoded into a spatial dimension of laser pulse by an intersection angle between the laser and the electron beam at the EO-crystal. In this paper, we present a comparative study of bunch length and arrival time measurements performed simultaneously with all three experimental techniques.
|
|
TUPCH026 |
Single Shot Longitudinal Bunch Profile Measurements at FLASH using Electro-optic Techniques
|
1055 |
|
- B. Steffen, E.-A. Knabbe, B. Schmidt
DESY, Hamburg
- G. Berden, A.F.G. van der Meer
FOM Rijnhuizen, Nieuwegein
- W.A. Gillespie, P.J. Phillips
University of Dundee, Nethergate, Dundee, Scotland
- S.P. Jamison, A. MacLeod
UAD, Dundee
- P. Schmüser
Uni HH, Hamburg
|
|
|
For the high-gain operation of a SASE FEL, extremly short electron bunches are essential to generate sufficiently high peak currents. At the superconducting linac of the VUV-FEL at DESY, we have installed an electro-optic experiment with temporal decoding and spectral decoding to probe the time structure of the electric field of single sub 200fs e-bunches. In this technique, the field-induced birefringence in an electro-optic crystal is encoded on a chirped ps laser pulse. The longitudinal electric field profile of the electron bunch is then obtained from the encoded optical pulse by a single-shot cross correlation with a 30 fs laser pulse using a second-harmonic crystal (temporal decoding) or by a single-shot measurement of its spectrum (spectral decoding). In the temporal decoding measurements an electro-optic signal of 230fs FWHM was observed, and is limited by the material properties of the particular electro-optic crystal used. Bunch profile and time jitter measurements were obtained simultaneously with VUV SASE operation.
|
|
TUPCH027 |
Time Resolved Single-shot Measurements of Transition Radiation at the THz Beamline of FLASH using Electro-optic Spectral Decoding
|
1058 |
|
- B. Steffen, E.-A. Knabbe, B. Schmidt
DESY, Hamburg
- G. Berden, A.F.G. van der Meer
FOM Rijnhuizen, Nieuwegein
- W.A. Gillespie, P.J. Phillips
University of Dundee, Nethergate, Dundee, Scotland
- S.P. Jamison, A. MacLeod
UAD, Dundee
- P. Schmüser
Uni HH, Hamburg
|
|
|
Single-shot electro-optic detection was used to measure the temporal profile of coherent transition radiation (CTR) pulses at the VUV-FEL at DESY. The CTR was generated from single bunches kicked to an off-axis screen, with the radiation transported through a 20m long transfer line imaging the CTR from a radiation screen to an experimental station outside the accelerator tunnel. Bipolar pulses with a FWHM less than 1ps have been measured and are consistent with simulations of the propagation of radiation through the transfer line.
|
|
TUPCH028 |
Layout of the Optical Synchronization System for FLASH
|
1061 |
|
- A. Winter, P. Schmüser, A. Winter
Uni HH, Hamburg
- F. Loehl, F. Ludwig, H. Schlarb, B. Schmidt
DESY, Hamburg
|
|
|
The present RF synchronization system of the VUV-FEL can typically stabilize the arrival time of the electron bunches at the undulator to about 200 fs on a timescale of minutes and to several picoseconds on a timescale of hours. To improve the machine stability and to ensure optimal performance for the VUV-FEL user facility, a new ultra-precise timing system is mandatory. The optical synchronization system under construction will satisfy three goals: Firstly, it provides a local oscillator frequency with the same stability as the existing low-level RF regulation, secondly, it can synchronize the experimental lasers of the FEL users with a precision in the order of 30 fs, thirdly, it provides an ultra-stable reference for beam arrival time measurements and enables a feedback on the electron beam to compensate residual drifts and timing jitter. The optical synchronization system is based on an optical pulse train from a mode-locked laser with a highly stabilized repetition rate. This paper describes the proposed layout of the optical synchronization system, the integration into the machine layout and the diagnostic experiments to monitor the performance of the system.
|
|
TUPCH029 |
High-precision Laser Master Oscillators for Optical Timing Distribution Systems in Future Light Sources
|
1064 |
|
- A. Winter, P. Schmüser, A. Winter
Uni HH, Hamburg
- J. Chen, F.X. Kaertner
MIT, Cambridge, Massachusetts
- F.O. Ilday
Bilkent University, Bilkent, Ankara
- F. Ludwig, H. Schlarb
DESY, Hamburg
|
|
|
X-ray pulses with a pulse duration in the 10 fs regime or even less are needed for numerous experiments planned at next generation free electron lasers. A synchronization of probe laser pulses to the x-ray pulses with a stability on the order of the pulse width is highly desirable for these experiments. This requirement can be fulfilled by distributing an ultra-stable timing signal to various subsystems of the machine and to the experimental area to provide synchronization at the fs level over distances of several kilometers. Mode-locked fiber lasers serve as laser master oscillators (LMO), generating the frequencies required in the machine. The pulse train is distributed through length-stabilized fiber links. This paper focuses on the LMO, devoting special attention to the phase noise properties of the frequencies to be generated, its reliability to operate in an accelerator environment, and the residual timing jitter and drifts of the RF feedback for the fiber links. A prototype experimental system has been constructed and tested in an accelerator environment and its performance characteristics will be evaluated.
|
|
THPPA01 |
High-precision Laser Master Oscillators for Optical Timing Distribution Systems in Future Light Sources
|
2747 |
|
- A. Winter, P. Schmüser, A. Winter
Uni HH, Hamburg
- J. Chen, F.X. Kaertner
MIT, Cambridge, Massachusetts
- F.O. Ilday
Bilkent University, Bilkent, Ankara
- F. Ludwig, H. Schlarb
DESY, Hamburg
|
|
|
Abstract to be supplied
|
|
|
Transparencies
|