Abstracts Brochure - CERN

MOPCH — Poster Session 26-Jun-06 16:00 - 18:00
with this cavity. An initial experiment with copper benchmarked our apparatus. It afforded an opportunity to refine
our technique of determining Q0 from the reflected frequency response and revealed the behavior of copper down to
4.2 K. This was followed by a test of a niobium sample. A test is also planned for MgB2. In addition to characterizing
the onset of superconductivity with temperature, our cavity can be resonated with a high power klystron to determine
the surface magnetic field level sustainable by the material in the superconducting state.
*C. Nantista et al. “Test Bed for Superconducting Materials,” presented at the 2005 Particle Accelerator Conference,
Knoxville, Tennessee, May 16-20, 2005; SLAC-PUB-11246.
1.3 GHz Electrically Controlled Fast Ferroelectric Tuner
A fast, electrically-controlled tuner is described
with parameters suitable for operation
with the 9-cell SC accelerator structure
of ILC. The tuner is based on a magic tee and
V.P. Yakovlev (Omega-P, Inc.) J.L. Hirshfield (Yale University,
Physics Department) S. Kazakov (KEK)
two phase shifters that contain ferroelectric rings. The dielectric constant of the ferroelectric ring is altered by applying
a 4.2 kV DC pulse that provides an RF phase shift from 0 deg to 180 deg. This, in turn allows a change of the input
signal amplitude from zero to its maximum value, or a change in phase from 0 deg to 360 deg during the RF pulse. It
is shown that the possibility of changing the cavity coupling to the input line during the RF pulse allows significant
RF power savings, up to 12.5 MW for the 800 GeV ILC option. In addition, fast electrically-tuned amplitude and
phase control with a feed-back system should be useful to compensate for possible phase deviations of the input RF
fields in each cavity of ILC to match the cavity with the feeding transmission line as the beam load varies.
The JLAB Ampere-class Cryomodule Conceptual Design
For the next generation of compact highpower
FELs a new cryomodule is required
that is capable of accelerating up to Ampere
levels of beam current. Challenges include
R.A. Rimmer, E. Daly, J. Henry, W.R. Hicks, J.P. Preble, M. Stirbet,
H. Wang, K. Wilson, G. Wu (Jefferson Lab)
strong HOM damping, high HOM power and high fundamental-mode power (in operating scenarios without full
energy recovery). For efficient use of space a high real-estate gradient is desirable and for economic operation good
fundamental-mode efficiency is important. The technology must also be robust and should be based on well-proven
and reliable technologies. For Ampere-class levels of beam current both halo interception and beam break-up (BBU)
are important considerations. These factors tend to drive the designs to lower frequencies where the apertures are
larger and the transverse impedances are lower. To achieve these goals we propose to use a compact waveguidedamped
multi-cell cavity packaged in an SNS-style cryomodule.
Compact Waveguide Fundamental Power Coupler Design for 1-Ampere Cryomodule
Development of a new CW cryomodule capable
of transporting Ampere-level beam currents
in a compact FEL is currently underway
at JLAB. The 748.5 MHz cavities will operate
M. Stirbet, E. Daly, J. Henry, W.R. Hicks, R.A. Rimmer, K. Wilson
(Jefferson Lab)
with at least 16 MV/m acceleration gradients at forward RF power up to 200 kW. In this paper we propose a compact
waveguide fundamental power coupler, based on the robust, pre-stressed planar window concept developed and
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