Abstracts Brochure - CERN

MOPCH — Poster Session 26-Jun-06 16:00 - 18:00
Development of a Prototype Superconducting CW Cavity and Cryomodule for Energy Recovery
Energy Recovery LINAC (ERL) and LINACdriven
FEL proposals and developments are
now widespread around the world. Superconducting
RF (SRF) cavity advances made
over the last 10 years for TESLA/TTF at 1.3
GHz, in reliably achieving accelerating gra-
P.A. McIntosh, C.D. Beard, D.M. Dykes, B. Todd (CCLRC/DL/
ASTeC) J.M. Byrd, J.N. Corlett, D. Li (LBNL) M. Liepe, V. Medjidzade,
H. Padamsee, J. Sears, V.D. Shemelin (Cornell University)
P. Michel, J. Teichert (FZR)
dients >20 MV/m, suggest their suitability for these ERL and FEL accelerators. Typically however, photon fluxes
are maximised from the associated insertion devices when the electron bunch repetition rate is as high as possible,
making CW-mode operation at high average current a fundamental requirement for these light sources. Challenges
arise in controlling the substantial HOM power and in minimizing the power dissipated at cryogenic temperatures
during acceleration and energy recovery, requiring novel techniques to be employed. This paper details a collaborative
development for an advanced high-Qo cavity and cryomodule system, based on a modified TESLA cavity, housed
in a Stanford/Rossendorf cryomodule. The cavity incorporates a Cornell developed resistive-wall HOM damping
scheme, capable of providing the improved level of HOM damping and reduced thermal load required.
RF Requirements for the 4GLS LINAC Systems
The 4GLS facility at Daresbury will combine
energy recovery linac (ERL) and free
electron laser (FEL) technologies to deliver a
suite of naturally synchronised state-of-the-
P.A. McIntosh, C.D. Beard, D.M. Dykes, A.J. Moss (CCLRC/DL/
ASTeC)
art sources of synchrotron radiation and FEL radiation covering the terahertz (THz) to soft X-ray regimes. CWmode
operation at high acceleration gradients are needed for the various 4GLS accelerator systems and here is where
Superconducting Radio Frequency (SRF) cavities excel. Since resistive losses in the cavity walls increase as the square
of the accelerating voltage, conventional copper cavities become uneconomical when the demand for high CW voltage
grows with particle energy requirements. After accounting for the refrigeration power needed to provide the liquid
helium operating temperature, a net power gain of several hundred remains for SRF over conventional copper cavities.
This paper details the RF requirements for each of the SRF accelerating stages of the 4GLS facility, outlining techniques
necessary to cope with CW-mode operation and HOM power generation.
Analysis of Wakefields in the ILC Crab Cavity
The large crossing angle schemes of the ILC
need a correction of bunch orientation at the
IP in order to recover a luminosity loss of up
to 80%. The orientation of bunches can be
G. Burt (Microwave Research Group, Lancaster University) C.D.
Beard, P. Goudket (CCLRC/DL/ASTeC) L. Bellantoni (Fermilab)
changed using a transverse deflecting cavity. The location of the crab cavity would be close to the final focus, and
small deflections caused by wakefields in the cavities could cause misalignments of the bunches at the IP. Wakefields in
the FNAL CKM cavities have been analysed and their effects studied in view of use as the ILC crab cavity. Numerical
simulations have been performed to analyse the transverse wakepotentials of up to quadrupole order modes in this
cavity and the effect upon bunches passing through this cavity. Trapped modes within the CKM cavity have been
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