Abstracts Brochure - CERN

TUPCH — Poster Session 27-Jun-06 16:00 - 18:00
Precision RF Gun Phase Monitor System for the VUV-FEL
For RF photo-injectors, the properties of the
high brightness beam critically depend on H. Schlarb, N. Heidbrook, H. Kapitza, F. Ludwig, N. Nagad (DESY)
the synchronisation between the RF gun acceleration
phase and the photo-cathode laser. At the VUV-FEL, the phase stability is determined by operating the RF
gun close to zero-crossing RF phase. This allows the conversion of phase variations into charge variations which then
is readout by a precision charge measurement system based on toroids. In this paper, we discuss the limitation of this
method. Resolution reduction of the charge measurement system due to electro-magnetic-interference is discussed
in detail.
Single Shot Longitudinal Bunch Profile Measurements at the DESY VUV-FEL Using Electro-optic
Techniques
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-
B. Steffen, E.-A. Knabbe, B. Schmidt (DESY) G. Berden, A.F.G. van
der Meer (FOM Rijnhuizen) W.A. Gillespie, P.J. Phillips (University
of Dundee) S.P. Jamison, A. MacLeod (UAD) P. Schmüser (Uni HH)
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.
Time Resolved Single-shot Measurements of Transition Radiation at the THz Beamline of
the DESY VUV-FEL Using Electro-optic Spectral Decoding
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,
B. Steffen, E.-A. Knabbe, B. Schmidt (DESY) G. Berden, A.F.G. van
der Meer (FOM Rijnhuizen) W.A. Gillespie, P.J. Phillips (University
of Dundee) S.P. Jamison, A. MacLeod (UAD) P. Schmüser (Uni HH)
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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