| Paper |
Title |
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| TUPCH024 |
Comparative Study of Bunch Length and Arrival Time Measurements at FLASH
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1049 |
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- 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
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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.
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| TUPCH026 |
Single Shot Longitudinal Bunch Profile Measurements at FLASH using Electro-optic Techniques
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1055 |
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- 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
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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.
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| TUPCH027 |
Time Resolved Single-shot Measurements of Transition Radiation at the THz Beamline of FLASH using Electro-optic Spectral Decoding
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1058 |
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- 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
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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.
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