Abstracts Brochure - CERN

MOPLS — Poster Session 26-Jun-06 16:00 - 18:00
Magnetic Modelling of a Short Period Superconducting Helical Undulator for the ILC
Positron Source
A positron source utilising undulators is now
defined as the baseline option for the International
Linear Collider (ILC). The ILC requires
a short period undulator, as close to 10mm
as possible, that is capable of producing 10
MeV photons. The HeliCal collaboration in
the UK has undertaken a programme to design,
develop and produce a prototype un-
J. Rochford, E. Baynham, T.W. Bradshaw, F.S. Carr, Y. Ivanyushenkov
(CCLRC/RAL/ASTeC) I.R. Bailey, L.I. Malysheva (Cockcroft Institute)
D.P. Barber (DESY) A.J. Brummitt (CCLRC/RAL) J.A. Clarke,
O.B. Malyshev, D.J. Scott (CCLRC/DL/ASTeC) P. Cooke, J.B. Dainton
(Liverpool University, Science Faculty) G.A. Moortgat-Pick
(Durham University)
dulator. As part of the programme, the group has used the OPERA software package to perform the magnetic design
of the undulator. The design has addressed several issues, including the effect of magnetic material for the undulator
former, optimal winding geometry, the magnetic flux inside the superconductor and its variation with undulator
period and the winding bore. This paper summarizes the results of both the 2d and the 3d magnetic simulations.
Higher Band Dipole Wake Field Simulations for the Main Linacs of the ILC
The main superconducting L-band linacs of
the ILC (International Linear Collider) will R.M. Jones, R.M. Jones (UMAN)
consist of two sets of approximately 10,000
nine-cell accelerating cavities, which will accelerate electrons and positrons up to a center of mass energy of initially
500 GeV and 1 TeV in a future projected upgrade. During acceleration, it is important to preserve the emittance of the
beam as any dilution thereof will degrade the luminosity of the beams at the collision point. Transverse wake fields
excited by multiple bunches with the beam train can cause the emittance to be diluted and in the worst case can give
rise to a beam break up instability. Here we report on detailed wake field simulations for TESLA-like cavities and
on recently designed LL (Low Loss) and re-entrant cavities; the latter cavities are reshaped with a view to achieving
higher gradients. The impact on beam dynamics is taken into account by tracking the particles down the complete
linac and recording the emittance.
Mitigation of Emittance Dilution due to Transverse Mode Coupling in the L-band Linacs
of the ILC
The main L-band linacs of the ILC accelerate
2820 bunches from a center of mass of 10 R.M. Jones, R.M. Jones (UMAN) R.H. Miller (SLAC)
GeV to 500 GeV (and in the proposed later
upgrade, to 1 TeV). The emittance of the vertical plane is approximately 400 times less than that of the horizontal
plane. Provided the vertical and horizontal mode dipole frequencies are degenerate, then the motion in each plane
is not coupled. However, in reality the degeneracy will more than likely be removed with the eigen modes lying
in planes rotated from the x and y planes due to inevitable manufacturing errors introduced in fabricating 20,000
cavities. This gives rise to a transverse coupling in the horizontal-vertical motion and can readily lead to a dilution
in the emittance in the vertical plane. We investigate means to ameliorate this emittance dilution by splitting the
horizontal-vertical tune of the lattice.
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