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Feedback on magnetic length using laminations
June 2002,
Manufacturer 2. Azimuthal coil size of both inner and outer layer of 2012 and
2014 are larger than nominal, requiring for the use of 0.1 mm less thick inner
and outer layer pole shims. This has an impact of about 10 negative units on
the main field, which is observed in the collared coils measurements. Even
though the effect is not very large, it is decided to profit of this case to
try for the first time the use of additional laminations to recover a longer
magnetic length, thus compensating the integrated main field.
In the specification Annex B.? it is stated that up to 100 mm of additional
iron laminations, replacing the nested ones, can be added (50 on each side).
Since the difference in the main field between iron laminations and nested
laminations is around 10%, 100 mm more should give a 10 mm increase in the
magnetic length, i.e. 7 units.
April 2003,
Manufacturer 2. Data of cold masses 2012 and 2014 are available. Analysis
shows (see file)
that in average cold masses with nominal laminations have a magnetic length
that is 55 mm less than the collared coil, with a sigma of 4 mm. In the
case of 2012 and 2014, with 100 mm more of iron laminations, the difference
of magnetic length between cold mass and collared coil is -45 mm, with a sigma
of 2 mm.
April 2003, CERN. On the
basis of the measurements, it is asked to add 100 mm more of lamination also in
2013, 2016, 2017 and 2018 that has lower main field due to non-nominal shims.
Moreover, it is asked to add 100 mm more laminations in 2022 and 2026 that,
even though with nominal shims, featured a lower main field.
(... to be continued ...)
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