Abstracts Brochure - CERN

MOPLS128
MOPLS129
MOPLS130
26-Jun-06 16:00 - 18:00 MOPLS — Poster Session
Status of the Fatigue Studies of the CLIC Accelerating Structures
S.T. Heikkinen, S.T. Heikkinen (HUT) S. Calatroni, H. Neupert, W.
Wuensch (CERN)
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The need for high accelerating gradients for
the future Compact Linear Collider imposes
considerable constraints on the materials of
the accelerating structures. The surfaces ex-
posed to high pulsed RF currents are subjected to cyclic thermal stresses possibly resulting in surface break up by
fatigue. Since no fatigue data exists in the literature up to very large numbers of cycles, a comprehensive study has
been initiated. Low cycle fatigue data (up to 10 8 cycles) has been collected by means of a pulsed laser surface heating
apparatus. The surface damage has been characterized by SEM observations and roughness measurements. High
cycle fatigue data (up to 10 11 cycles) at various stress ratios have been collected in high frequency bulk fatigue tests
using an ultrasonic apparatus. It is found that the appearance of surface fatigue damage in the laser experiments,
and of fatigue cracks in the bulk specimen, happen at similar stress levels for similar numbers of cycles. This allows
the two experimental techniques to be connected and to predict the surface damage at a high number of cycles. Upto-date
fatigue data for selected high conductivity, high strength Cu alloys are presented.
Integration of the PHIN RF Gun into the CLIC Test Facility
CERN is a collaborator within the European
S. Doebert (CERN)
PHIN project, a joint research activity for
Photo injectors within the CARE program.
The scope of this project is to build an RF Gun equipped with high quantum efficiency Cs2Te cathodes and a laser
to produce the nominal beam for the CLIC Test Facility (CTF3). The nominal beam for CTF3 has an average current
of 3.5 A, 1.5 GHz bunch repetition frequency and a pulse length of 1.5 us (2310 bunches) with quite tight stability
requirements. In addition a phase shift of 90 deg is needed after each train of 140 ns for the special CLIC combination
scheme. This RF Gun will be tested at CERN in fall 2006 and should be integrated as a new injector into the CTF3
linac, replacing the existing injector consisting of a thermionic gun and a subharmonic bunching system. The paper
studies the optimal integration into the machine trying to optimize transverse and longitudinal phase space of the
beam while respecting the numerous constraints of the existing accelerator. The presented scheme uses emittance
compensation and velocity bunching to fulfill the requirements.
Implications of a Curved Tunnel for the Main Linac of CLIC
Preliminary studies of a linac that follows the
A. Latina, D. Schulte (CERN) P. Eliasson (Uppsala University) earth’s curvature are presented for the CLIC
main linac. The curvature of the tunnel is
modeled in a realistic way by use of geometry changing elements. The emittance preservation is studied for a perfect
machine as well as taking into account imperfections. Results for a curved linac are compared with those for a laserstraight
machine.