NLC Movers and Supports
Author: John Cornuelle
Date: March 7, 2003
All of the beam line components must have some kind of support. Many also require precision movers
because the final alignment needed is more precise than what surveying techniques can provide, and needs to be
done with the beam present (tunnel empty). The mover requirements are set by Accelerator Physics and are:
3000 µ range
.250 µ step size
3000 µ range
.050 µ step size
There are engineering requirements that come from the need to support a certain amount of equipment on
each mover. Both the girder and magnet movers need to be able to support 1,300 pounds apiece.
The complete beam line systems, comprising the equipment and movers and supports, need to meet certain
established requirements for temperature stability, vibration amplitude and frequency, and long-term mechanical
stability as a system. The requirements just for the supports cannot be broken out of this integrated requirement.
1. Overall Description
There are 2,030 girder movers, 2,500 magnet movers, and 12,400 supports. The movers are based on a
successful design prototyped in the FFTB, using harmonic gear reduction. Other technologies may also be usable.
2. Technical issues
There are no significant technical issues other than operational reliability/availability. The movers contain
motors, gear trains, and bearings, and if any of these stop working, then that axis of that component can no
longer participate in beam-based alignment. At some point, this degradation will require an entry to the tunnel
to repair the failed units. This time period by design will have to be long enough not to be a driver for the
availability of the overall machine.
3. Changes from Prior Configurations
The drift sections in the non-RF portion of the Main Linac are being replaced with a bypass line that is used
to carry the lower energy beam. This bypass line will have inexpensive supports, and these are not included in
the component count shown above. Component count differences due to lattice and other changes for the NLC
2001 and NLC 2003 including major revisions to Beam Delivery (shortened final focus lengths and extra IR),
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the additions of extra transport lines to the Injector Systems, and the topological changes to Injector Systems
are also not included.
Discussion of Configuration Choices
The mover function must be present for beam-based alignment to be performed. The selected technology
must move as specified above, retain that performance over some (long) time period, and fail on a basis that does
not interfere with the operational availability of the machine. So, it is possible that the technology selected will not
be the least expensive technology to acquire and install.
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