Abstracts Brochure - CERN

THPCH174
THPCH175
THPCH176
29-Jun-06 16:00 - 18:00 THPCH — Poster Session
amplified using 9th harmonic frequency, and the FFT spectrum analyzer could cover noise bandwidth from 0.01Hz
to 100 kHz. A distributed control system is built based on EPICS to monitor and control the system performance.
*C. X. Tang et al. Proc. of 2004 FEL conference, 622-624.
Theoretical and Experimental Study of Micro-pulse Electron Gun
The Micro-pulse Electron Gun (MPG) is a
J.Y. Zhai, C.-X. Tang, S. Zheng (TUB)
new type of cold cathode RF electron gun
that is based on the multipactor effect. MPG
can produce short duration, high current and self-bunching electron beams. This paper presents our work on the
analytical theory, numerical simulation and hot test experiments of MPG. The Cu-Al-Mg alloy, Pd-Ba alloy, EBE MgO
films and CVD diamond films were used respectively as the secondary electron emitters in the experiments. A micropulse
current with the density up to 20 amperes per square cm was observed. The emission currents at different RF
power levels were measured and explained with the steady-state and transient multipactor dynamics. The results
agree with the analytical calculation and computer simulation. The properties of the secondary electron emission
cathodes are also discussed.
Automatic Resonant Excitation Based System for Lorentz Force Compensation for VUV-
FEL
The cavity is the key element of each linear
P.M. Sekalski, A. Napieralski (TUL-DMCS) S. Simrock (DESY) accelerator used for high-energy physics purpose.
The resonant frequency of cavities depends
on its shape. Due to the pulse operation, they are deformed by dynamic Lorentz force (LF) caused by
accelerating electromechanical field. As a consequence, the cavities are not working on resonance but they are detuned
from master oscillator frequency by few hundreds of Hertz depending on accelerating field gradient. The
paper presents an automatic control system for LF compensation applied to fast tuning mechanism CTS. The active
element is multilayer low-voltage piezoelectric stack (EPCOS). The resonant excitation with adaptive feed forward
algorithm is used to drive the actuator. Test performed at VUV-FEL on cav5/ACC1 showed that detuning during
flat-top period (800us) might remain below 10Hz for accelerating field gradient of 20MV/m.
Deposition of Lead Thin Films Used as Photo-cathodes by Means of Cathodic Arc under
UHV Conditions
P.S. Strzyzewski, J. Langner, R. M. Mirowski, M. S. Sadowski, J.W.
Witkowski (The Andrzej Soltan Institute for Nuclear Studies, Centre
Swierk) T. Rao, J. Smedley (BNL) J.S. Sekutowicz (DESY)
438
The cathodic arc technology has been used
for various technical purposes for many
years. Recently, it has been demonstrated
that the cathodic arc can be operated under
ultra-high vacuum (UHV) conditions and it
might solve the problem of the oxygen contamination coming from water remnants. It opens a new road to many
applications where very pure metallic and/or superconducting films are needed. The paper reports on recent experimental
studies aimed on the deposition of superconducting films of pure lead (Pb) by means of the UHV cathodic arc.
Such layers can be used as photo-cathodes needed for modern accelerator injectors. The system configuration, used