AB-BT representatives were invited to discuss the
responsibilities and workpackages for head-tail dump as well as internal
H0/H- dump. WW explained briefly the function
of the head- and tail-dump, to which the beam in the raise and fall time of
the LINAC4 pulse are deflected, as well as the internal H0/H-
dump, to which the partly and unstripped particles are deflected. It
was mentioned that the head dump shall also be robust enough to withstand,
and protect downstream elements in case of full beam impact due of
malfunction of the BI.DIS magnets, which is also the case for the internal H0/H-
dump in case of stripping foil failure. Due to the fact that the dumps
form an integral part of the magnets, it was decided that the mandate of
building these dumps will stay within the AB-BT workpackage. Nevertheless, a
functional specification shall be drawn up, giving load scenarios, radiation
estimates and magnet protection data, in order to enable AB-ATB to perform
the conceptual design for these items.
CC asked if protection of the septum blade will be required, JB replied that
this is currently the case by small scrapers and that in the new design this
will be envisaged but due to the limited space (~5mm) full protection will
be difficult.
WW showed slides on the
aperture limitations for
H- beam at the BI.DIS and BI.SMV, which were presented during the LINAC4
PSB commissioning meeting of 22-05-2008. The new proposed scheme provides
additional 4-5 mm clearance at BI.SMV’s (min. +2.5 mm) beam clearance at the
BI.SMV entrance, therefore the BI.DIS angles have to be increased up to 4.75
mrad. JB reported that the BI.DIS have been successfully tested up to 30 kV,
sufficient for a 5 mrad deflection, ∫B•dl of 9.5 mT.m, with a required
voltage of 26.75 kV and a required current of 1100 A. Furthermore it was
noted that the offset at BIDIS entrance of 5.2 mm shall be increased to 6.5
mm and the DVT40 deflection needs to change from 7.27 mrad to 9.2 mrad,
requiring a performance increase of 2.4 in ∫B•dl (compared to 1.9 baseline).
JB mentioned that additional beam clearance at BI.SMV1 could be obtained if
a bent yoke would be used instead of segmented yoke.
CC mentioned the option of increasing the space between BI.SMV and BVT as
well as between the BI.DIS and BI.SMV magnets in order to relax the BI.SMV
performance, which could lead to a simplified magnet design.
JB presented
FLUX2D
simulations on the expected fringe fields of the BI.SMV seen by the
adjacent beam. Harmonic values, as presented in attached slides, have been
calculated for a beam radius of 16mm. It was decided that these values need
to be implemented in the optics model to check the influence.
BB indicated that for the feasibility study concerning BI.BS
magnet fall time decrease it needs to be investigated what the cut
off value is to go from eddy current screen to a direct drive magnet
configuration. This still needs to be simulated to see what the slowest
possible fall/rise time would be.
WW mentioned that for the BT LINAC4 workpackage a description needs to be written, containing the main parameters, a short technical description, scope of the Workpackage, list of deliverables, organisation of the Workpackage, planning and intermediate milestones, workpackage breakdown with a detailed description of what is included and what is needed from other Workpackages, budget estimate and spending profile, manpower estimate, etc. WW shall make a draft for discussion.