Abstracts Brochure - 2nd International Particle Accelerator Conference

Poster Panel 96
ID: 4061 - MOPC046
CaCo: A Cavity Combiner for IOTs Amplifiers,
Beatriz Bravo, Filip Mares, Francis Perez, Paco
Sanchez (CELLS-ALBA Synchrotron, Cerdanyola
del Vallès), Michel Langlois (ESRF, Grenoble) -
The ALBA storage ring uses six room temperature
cavities; each one fed by two 80 kW IOTs amplifiers
at 499.654 MHz. The power of the pair of
transmitters is combined by a cavity combiner,
CaCo. One of the design requirements of CaCo was
that it continued working safely and with a good
efficiency in the case of an IOT failure
(asymmetrical mode). During the first asymmetric
full power tests, in May 2010, with an active IOT
and the other passive, the result was dramatic, the
passive IOT broke in two parts after few hours of
operation. This paper presents the experimental
results and the electromagnetic field simulations of
the asymmetrical operation mode of CaCo, i.e. one
active IOT and the other passive, and analyze why
the ceramic of the output tube of the passive IOT
broke during the first performance of this mode.
Also, it reports a possible solution to solve this
problem.
Sub Classification: T06 Room Temperature RF
Poster Panel 97
ID: 3351 - MOPC002
Cooling and Vibration Studies for the CLIC Xband
Accelerating Structures, Tessa Charles, Kris
Ryan (Monash University, Melbourne), Mark James
Boland (ASCo, Clayton, Victoria), Germana
Riddone (CERN, Geneva), Alexander Samoshkin
(JINR, Dubna, Moscow Region) - Turbulent cooling
water in the Compact Linear Collider (CLIC)
accelerating structures will inevitably induce some
vibrations. The maximum acceptable amplitude of
vibrations is small, as vibrations in the accelerating
structure could lead to beam jitter and alignment
difficulties. A FEM model is needed to identify the
conditions under which vortex shedding from the
cooling system induces significant vibrations. Due
to the orders of magnitude difference between the
fluid motion and the structure motion, vibrations of
the structure will make a negligible contribute to the
turbulence of the cooling fluid. Therefore the
resonant conditions of the cooling channels,
presented in this paper, determine directly the
natural frequencies of the accelerating structures,
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Main Classification 7: Accelerator Technology
29
thereby identifying frequencies to be avoided under
normal operating conditions. These results will be
applied to the final structural design of the
accelerating structures. This paper also identifies the
positioning of sensors for the CLIC Two-Beam Test
Module.
Sub Classification: T06 Room Temperature RF
Poster Panel 98
ID: 2026 - MOPC030
The C-band Traveling-wave Accelerating
Structure for Compact XFEL at SINAP,
Wencheng Fang, Qiang Gu, Zhentang Zhao
(SINAP, Shanghai), Dechun Tong (TUB, Beijing) -
The R&D of C-band accelerating structure has been
launched two years ago at Shanghai Institute of
Applied Physics, it will be used for the future
compact hard X-ray FEL. The 1st C-band travelingwave
accelerating structure is ready for the high
power test now. This structure is the preliminary
model for the research of the technology of
microwave test and tuning, arts and crafts and high
power test. This paper presents the process of
fabrication, cold test and tuning results.
Sub Classification: T06 Room Temperature RF
Poster Panel 99
ID: 4447 - MOPC065
Ion Motion in the Vicinity of Microprotrusions in
Accelerating Structures, Dmytro Kashyn, Tom
Antonsen, Irving Haber, Gregory Nusinovich
(UMD, College Park, Maryland) - It is known that
newly fabricated accelerating structures have almost
ideally smooth surface. However, ‘post mortem’
examination of these structures reveals that their
surface can be significantly modified after highgradient
operation. This surface modification can be
caused by the appearance of microscopic
protrusions*. One of the factors leading to heating,
melting and evaporation of these protrusions (factors
resulting in the RF breakdown) is ion
bombardment**. In our study we analyze ion motion
in the vicinity of microprotrusions both analytically
and numerically. First, we study the ion motion in
the RF electric field magnified by the protrusion in
the absence of electron field emitted current and
show that most of the ions do not reach the structure
surface. Then we add into consideration the
interaction of ions with Fowler-Nordheim current
emitted from the tip of protrusion (dark current).