indico.cern.ch · created date: 10/2/2019 9:07:14 am
TRANSCRIPT
Technical Review of D2 short model CERN 2 October 2019
Technical review on D2 short
modelCERN 2 October 2019
Last results on D2 short model collaringP.Fabbricatore on behalf INFN team
1. The collaring of the repaired V2 aperture
2. Delamination of the G11 end spacer in the pole
3. General considerations about collaring
4. Coil dimensions – polymerization shims
Technical Review of D2 short model CERN 2 October 20192
Among the actions taken for
mitigating the problem at the
origin of the conductor
damage, the collars in the LC
side of aperture A has been
changed for including the
noses in the collars.
Replacement of coil A in aperture V2 of D2 short
model
• Following the problem met with the coil
A of aperture V2 limiting the current at
about 10 kA, the aperture was
uncollared and a damage of the
conductor found on the electrical exit
placed on the pole.
• A new coil type A was built and a new
collaring of the aperture V2 took place
V2 A3-A4
V2 A2-A3
V1B
AV2
A
B
Technical Review of D2 short model CERN 2 October 20193
Technical Review of D2 short model CERN 2 October 2019
After collaring there was a clear evidence of a damage of the end spacers
placed in the pole at the connection sides as shown in figure for the
(new) coil A type (the damaged zone is circled). The coil B of the aperture
shows the same kind of damage in the same location (the end spacer
placed in the pole) but of quite reduced amount
After re-collaring V2
Technical Review of D2 short model CERN 2 October 2019
After inspecting the collared coils
(also the one of aperture V1) we
have realised that in all cases there
are signs of de-lamination in these
spacers mainly due to the presence
of a hole weakening the
components. In the present case of
the recollared aperture V1 the
damage is more pronounced
because with the new collars having
an integrated the stainless core
embedded into the pole spacer is
no more present (this core was part
of the separated nose as shown in
the following figure showing the
non-connection side of new Coil
type A ).
Evidencies of delaminations in the pole spacer
Technical Review of D2 short model CERN 2 October 2019
The repair was done on
August 8th in presence of
INFN personnel. As already
remarked, the most damaged
pole end spacers after
collaring was the one of coil
type A (the new wound coil).
The inner part of the pole was
partially delaminated so first
of all ASG decided to remove
the part of the pole which was
already almost detached see
figure on the right (the thicker
part could be around 2-3
mm).
Repair of G11 poles in aperture V2
Technical Review of D2 short model CERN 2 October 20197
Repair of G11 poles in aperture V2
All holes and empty spaces of
that region with charged
stycast. The results for both
coil type A (left) and B (right)
are shown in the figures.
After the repair the electrical
tests (ground insulation, surge
tes, coil resistance) passed.
The magnet has been re-
assembled and ready to be re-
tested at cold
Technical Review of D2 short model CERN 2 October 2019 8
In the collaring phase the
upper and lower coils are
pressed each other through
their collars up to the caves
of the upper and lower collars
are aligned, allowing to insert
the keys and freeze the
aperture geometry.
The dimensions of the coil
should be such that when
keys are inserted the applied
pressure should guarantee
the designed pre-stress (with
some margin).
If coils (including ground
insulation) are thicker the
required pressure for
inserting the keys is higher. If
the coils are too thick, the
pressure can break the coil
Some general considerations on collaring
Technical Review of D2 short model CERN 2 October 2019 9
The new coil A was between 0.3 mm and 0.4 mm larger than nominal
(measurement under a pressure of 70 MPa) in line with the last coils done but
about 0.2 mm larger than the damaged A type coil. Moreover this time the
correct midplane insulation of 0.2 mm per coil was put in place (previously ASG
put 0.05 mm insulation causing b3 and b5 rising to +10 units). We have
observed that the dimensions of coils + midplane insulation has caused problems
in the collaring which has been done at a pressure 8% larger than the previous
collaring operations and only after long massage cycles. We have observed a
delamination of the poles in connection side
The coils are larger than nominal value at 70 MPa
Technical Review of D2 short model CERN 2 October 2019
The polymerization shims decided after tests on
stacks and mokeups
To be noted: shims fixed after test showed coilis -0.2 mm wrt nominal
Technical Review of D2 short model CERN 2 October 201911
Dimensions of coil A1 (the faulty coil)
Technical Review of D2 short model CERN 2 October 201912
Dimensions of coil A3-R (replacing the faulty coil)
Using the same polimerization
shim, the coil dimensions in
the central region changed
from + 0.26 mm deviation to +
the 0.43mm
To be noted that the coil
copper wedges produced by
lamination are at the limit and
some time out of tolerances.
ASG think this was the reason
for the 0.2 mm dimensional
variation among coils,
However it is clear from these
results that the polimerization
shims shall be increased of
0.2 mm-0.3 mm
Technical Review of D2 short model CERN 2 October 2019
Tapered shims in the coil ends
• The coil ends are constrained by the
no-pole collars, which can in principle
press this region only if the azimuthal
dimension is increased.
• In order to have controlled
dimensions of the coil ends allowing
to have a determined azimuthal
stress, tapered shims are placed at
the midplane
• The maximum thickness of the shims
is at the coil ends, reducing
progressively to zero longitudinally
along the coil end (about 150 mm)
• We think that the tapered shims were
too tick (see Stefania’s presentation)
Technical Review of D2 short model CERN 2 October 2019 14
1- The coil azimuthal dimensions involved in the model
were too large ( from 0.26 mm to 0.43 mm larger than
nominal) The polimerization shim shall be increased
(see Stefania’s presentation for quantitative values).
Crucial test with the practice coil (preceded by tests on
short mokeups)
2- The pole and spacers shall be compact with no holes
weakening the structure
3- The mid-plane tapered shims put in the coil ends shall
be re-calibrated for avoiding pressure higher than 70 MPa
in coil ends.
Indication for the prototype
Technical Review of D2 short model CERN 2 October 201915
Thank you for your attention