**[HGQ01 Construction Summary]{.underline}**

R. Bossert, J. Brandt, F. Nobrega 2-9-98

Tech Note #TD-98-018

HGQ01 is the first of several 2 meter long model IR quadrupole magnets
to be built at FNAL in support of the LHC project at CERN. Winding of
the coils for HGQ01 was begun in June 1997. The magnet was completed in
January of 1998. A summary of the most important features is listed
below:

> • 70 mm bore with 14 turns and one wedge in the inner coil and 16
> turns with one wedge in the outer coil.
>
> • Cable uses SSC strand, reconfigured for the HGQ cable. Inner cable
> is 38 strand right lay and outer cable 46 strand left lay.
>
> • Cable insulation: Inner cable has 25 micron thick by 9.5mm wide bare
> kapton with 50% overlap surrounded by 4.8mm x 50 micron thick kapton
> coated with 2290 epoxy adhesive with 2mm gaps. Outer cable has 25
> micron thick by 9.5mm wide bare kapton with 50% overlap surrounded by
> 25 micron thick by 9.5mm wide kapton coated with 2290 epoxy adhesive
> with 50% overlap.
>
> • Nominal coil curing temperature was 135 degrees Centigrade.
>
> • Machined G-10 coil end parts made to a geometry determined by the
> FNAL produced computer program \"BEND\".
>
> • Ground insulation consisting of a combination of 75 micron and 125
> micron kapton.
>
> • A 5mm wide \"cooling path\" cut into the ground wrap at the pole to
> provide helium flow between the bore and the body of the collared
> area.
>
> • Strip heaters between the inner and outer layers, but not between
> the outer layer and the collars.
>
> • Bearing strips to protect the coils from the serrated collar edges
> and to provide a mechanism to adjust preload.
>
> • Stainless steel collars which provide all the coil support, i.e.,
> \"stand-alone collars\".
>
> • Beam gauges on the inner and outer coils and capacitor gauges on the
> inner coils to monitor coil preload.
>
> • External splice with the splice geometry determined by the FNAL
> produced computer program \"LEAD\".
>
> • End collet with G-10 quadrant parts to support the lead end. \"Full
> round\" laminations provide support for the return end.
>
> • Fully instrumented with voltage taps.
>
> • 40 cm diameter iron yoke.
>
> • Field adjustment shims within the yoke.
>
> • 8 mm thick stainless steel skin welded longitudinally at the second
> and fourth quadrants.
>
> • 50mm thick stainless steel end plate welded to skin.
>
> • Instrumented end preload screws on both ends.
>
> • Quadrant splices external to end plate.

**[HGQ01 Assembly History]{.underline}**

**[I Test Winding]{.underline}**

**A. Winding Tension**

Test winding was done with both inner and outer cable, to determine
windability, cable lay and winding tension. It was decided to fabricate
both inner and outer cable to wind in the favorable direction (right lay
for inner and left lay for outer). Winding tests revealed that the
\"window\" of acceptability for winding tension was between 60 and 100
lbs.

Tensions lower than 60 lbs were not sufficient to form the cable into
the tight bends specified by the IR Quadrupole cross-section, although
strand displacement was easier to control. Tensions higher than 100 lbs
formed the cable to the end parts better, but not significantly. Popped
strands were no less frequent at higher tensions and were much more
difficult to control or repair. Also, at very high tensions, the cable
would sometimes spontaneously \"rope\", or come out of lay due to the
winding tension alone.

For these reasons, a nominal winding tension of 80 lbs was chosen for
all turns on both inner and outer coils. When popped strands were
encountered, winding tension was typically lowered to around 50 lbs, the
cable repaired, and the turn completed at the lower tension. After
completion of the turn, the tension was increased back to 80 lbs.
Straight section clamps insured that the lower tension was not
propagated back into previously wound turns.

The same nominal tension of 80 lbs will be used for both inner and outer
coils of HGQ02.

**B. Outer Cable Stability Problems**

During the initial test winding, there were problems with the mechanical
stability of the outer cable scheduled to be used for HGQ01. Gianluca
Sabbi discussed the problem with the cable manufacturer ( LBL). It
became apparent that a mistake in a setting the \"planetary ratio\" of
the cabling machine (a setting which gives the strand a twist to
compensate for the de-twisting of the strand when the wire is cabled)
had caused the cable to have an excessive natural twist in it\'s free
state and a subsequent mechanical instability when tensioned.

Several samples of HGQ outer cable, with different planetary ratios and
consequently different degrees of residual twist, were produced and test
wound in Industrial #3. Based on the test winding, a decision was been
made to produce the HGQ01 and HGQ02 outer cable with a planetary ratio
of -.57, producing a residual twist of around 15 degrees.

Winding tests showed this cable to be very stable for winding. It was
used for HGQ01 and will be used for HGQ02.

**[II. Coil Fabrication]{.underline}**

**A. Cable and insulation**

**1. Inner Cable Transposition Pitch**

The reel of cable which was be used for the inner coils of HGQ01 has a
transposition pitch different from the standard design (131mm instead of
114mm). Both the pole and quadrant splices are 4 1/2 inches (114mm)
long. The splices on magnet HGQ01 are therefore shorter than the
transposition pitch of the inner cable, instead of approximately the
same length, as was designed. This may have some effect on the splice
performance. Magnet HGQ02 will have cable with the design transposition
pitch of 114mm.

**2. Cable and wedge insulation system.**

Cable and wedge insulation system for HGQ01, as stated above, is:

> Inner cable has 25 micron thick by 9.5mm wide bare kapton with 50%
> overlap surrounded by 4.8mm x 50 micron thick kapton coated with 2290
> epoxy adhesive with 2mm gaps. Outer cable has 25 micron thick by 9.5mm
> wide bare kapton with 50% overlap surrounded by 25 micron thick by
> 9.5mm wide kapton coated with 2290 epoxy adhesive with 50% overlap.

For magnet HGQ02, the insulation system is:

> Inner cable has 25 micron thick by 9.5mm wide bare kapton with 50%
> overlap surrounded by 9.5mm x 50 micron thick kapton coated with
> \"QI\" modified polyimide adhesive with 2mm gaps. Outer cable has 25
> micron thick by 9.5mm wide bare kapton with 50% overlap surrounded by
> 50 micron thick by 9.5mm wide kapton coated with \"QI\" modified
> polyimide adhesive butt lapped (no gaps).

The insulation system used for HGQ01 uses the traditional 2290 epoxy.
The epoxy adhesive is unacceptable for the long magnets because its
radiation resistance is not adequate. It was used for the first magnet
only, because the curing press was not capable of temperatures higher
than about 140C. Modifications made it possible to cure coils at the
higher temperature starting with magnet HGQ02.

The outer layer of insulation used on HGQ02 is the design specification.
The insulation on the outer cable and wedges was changed for HGQ01
because 50 micron thick 9.5 mm wide kapton was unavailable with epoxy
adhesive. The goal in both cases was to fill the gaps, preventing the
helium from cooling the outer cable as well as it does the inner.

**3. End part material**

End part material for HGQ01 was G-10. Due to the unacceptable radiation
resistance of G-10, end parts for all HGQ02 and all subsequent magnet
will be Ultem 2300 (Ultem with 30% glass fill), machined from tubes.

There are some mechanical differences between the Ultem and G-10 that
affect coil fabrication. Ultem is slightly weaker than the G-10, and
compresses more easily during the curing process. Also, the bond
strength between the Ultem and polyimide adhesive is not as good as
between the G-10 and epoxy. These issues will be addressed in sections
(II,C,10) and (II,C,11) of this report.

**B. Preforming the pole splices:**

The first step in winding both inner and outer coils is to preform the
cable for the pole splice. This is done by inserting a section of the
cable into a two stage preform fixture, clamping it and forming into the
required shape, heating the fixture to 290C (550F), and applying solder
to the cable to hold its shape.

Several problems were encountered with the preform fixtures. The first
was in the cold block, a water cooled clamp that has several functions.
The cable is first clamped in the cold block before any cable forming is
done. The cold block is meant to retain the trapezoidal shape of the
cable, prevent relative strand displacement form propagating into the
spool, prevent solder buildup, and prevent solder and heat propagation
into the spool.

The cold block was too close to the fixture, and prevented the first
preform stage from heating properly. This problem was solved by removing
the water flow from the original cold block, and adding a second cold
block on the spool side of the fixture. The original cold block was
still used to retain the cable shape and prevent solder buildup and
strand displacement.

Heating times were too long on the original preform fixtures because of
too much fixture mass and too little heater power. The fixtures were
modified at Fermilab by changing the four 1/2 inch diameter second stage
heaters to 1000 Watt, and operating them at 208V. The fixture base
plates were modified by adding two 5/8 inch diameter 1000 watt heaters,
operating at 208 Volts.

A computer operated control system powered the three heater groups:
first stage, second stage, and fixture base plate. Each group was
monitored by a separate thermocouple, and heating

times were very much reduced. The slowest group to reach temperature
were the base plate heaters.

Holes were provided in the fixtures for flux and solder introduction.
The first preforms showed that solder did not completely cover all areas
of the cable, particularly in the first stage where the cable moves from
its position at the pole in the coil cross section to the coil midplane
in preparation of ramping up and out. This problem was solved by adding
a ribbon of solder along the cable when it is installed into the first
stage.

The forces required to bend the cable in the fixture turned out to be
very large, particularly in the second stage where the cable undergoes
two hard-way bends to ramp up and out of the coil package. These bends
were made by the action of two sliding plates, each pushing one of the
narrow edges of the cable while providing a fixed distance between them
to prevent strands from coming out of place.

The fixed distance was held by the stiffness of the top sliding plate.
The cable forces were so high that in one instance, the top plate bowed
upward as much as .38mm (0.015 in). This problem allowed strands to be
partially displaced, and was solved by adding a clamp to keep the top
plate from bowing.

The screws used to slide the top plate buckled on the fist preform, and
were replaced with larger diameter screws. Even with the larger screws,
the cable forces were so high that the second stage could not be
completely closed. Measurements showed that the inner coil fixture
failed to close by around 0.38mm (.015 in).

After only a few preforms, it was evident that the narrow edge contact
surfaces of the sliding plates on the inner coil fixture were being
damaged by the strand movement of the cable when closing. This damage,
along with the inability to close, was severe enough to cause the
finished preforms to be larger than specified by as much as 0.70mm
(0.028 in). This was allowed because this section of the preform was to
be enclosed in an oversized groove in the collets.

Investigation into this problem showed that the original sliding plates
were made from 6061-T6 aluminum, and not from the tougher 7075-T651
aluminum that had been specified. New plates were ordered for the inner
fixture, and the material was verified to be 7075-T651. The new plates,
although wearing much more slowly, were not coated with the Ni-tuff hard
anodizing of the original plates, and there is some evidence of gauling.

In spite of these problems, the preform fixtures performed quite well.
The preforms made were quite uniform and more accurate than those made
for any other magnet program, including the LBQ and SSC programs. The
basic method and tooling will continue to be used for the balance of the
external splice IR quadrupole magnets.

**C. Winding and Curing Problems**

**1. Scraping on outer surface of inner coils.**

Scraping occurred on the outer surface of the first two inner coils.
There are areas where the cable insulation was scraped away, revealing
bare copper, at the outer perimeter

of the first three turns of the first current block, and the first turn
of the second current block, in the area where the turns go around the
end. The effect was worse on the return end than on the lead end. The
effect was evident after winding, and became worse during curing.

The problem concerned the \"hold down finger\", or tooling which holds
down the cable at the ends while winding. The finger was radiused at the
contact surfaces to conform to the shape of the outer perimeter of the
cable package. In the first coils, it was repositioned (pushed forward
in z) after each turn was made. During repositioning, it scraped over
the turns, causing insulation to be removed. There are two \"lines\" of
scraped insulation, moving longitudinally across the end turns.

To solve the problem the hold down finger was relieved along the surface
which contacted the coil as shown below. Also, a piece of .010 in. thick
mylar was placed between the hold down finger and the cable during
winding to protect the turns from direct scraping motion of the finger.
The winding procedure was also modified to include clamps to hold down
the finger while a turn is being wound. The clamps were removed during
finger repositioning. The slight finger deflection when the clamps were
removed , in conjunction with the protective sheet of mylar, allowed the
fingers to be repositioned without damage to the turns.

This winding procedure was used on all subsequent coils for HGQ01. It
is, however, a temporary solution and will be used only for magnets
HGQ01 and HGQ02. New tooling has been designed for HGQ03 (the first
internal splice coil) which will solve these problems by holding the
turns down without any line contact or sliding against the turns.

**2. Scraping on inner surface of inner coils**

Cable insulation has been removed at the inside surface of the first
inner coils, on both lead and return end, in the area where the turns
wrap around the poles. It is occurring on the first three turns of the
first current block, with the most significant scraping on the first
turn. The effect is worse on the return ends.

This has apparently happened during the curing process, although it is
difficult to tell if any damage occurred during winding, because these
areas are not visible until the coil is completely cured. It is caused
by either scraping or excessive downward force of the mandrel against
the coil while pressure is applied in the curing press.

There are two possible reasons this excessive force may be occurring. It
could be that, due to the angle at which these particular turns are
stacked in this area (see Figure A), the total corner-to-corner height
taken up by these turns is higher than the radial thickness allowed for
the layer. This situation has, however, occurred in past magnets without
this sort of insulation damage (although this cable is stiffer than any
previous coil produced at FNAL). It also could be due to the \"hump\"
that routinely occurs in the cable during winding. The cable \"humps\",
or rises from the mandrel after exiting a turn due to stresses or
relative strand movements incurred during winding. This hump must be
pushed down against the mandrel when pressure is applied in the curing
mold. When the cable is forced downward, stresses may be transferred to
the end area, causing the excessive load on the cable in that area. This
theory is seems more likely to be the cause of the damage because the
insulation damage is regularly skewed toward the side of the turn
containing the hump.

Two coils with this problem (HGQi002 and HGQi003) were used in HGQ01
after passing electrical tests. Insulating varnish was applied to
affected areas.

We believe that, if this problem does not cause turn-to-turn shorts, it
will not affect magnet performance. On all subsequent coils, strips of
.005 kapton are placed between the 1st and 2nd, and 2nd and 3rd turn
during inner coil winding. This will assure that enough space is
maintained between turns to allow insulating varnish to provide adequate
protection against turn-to-turn shorts.

This appears to be an adequate short term solution. None of the later
shorts that occurred were in the areas affected by this problem. If any
problems related to this scraping become evident, other solutions, such
as relieving the mandrel in this area, may be considered. For unknown
reasons, the problem became less severe in later coils, perhaps because
the forces from the hold-down fingers were reduced, or because of curing
tooling conditioning.

**3. Interference between pole insert and mold spacer during coil
insertion**

On the return end of the curing mold, a spacer bar is inserted into the
pole groove on the mold. This spacer is meant to prevent the retainer
from being extruded into the pole groove by curing forces.

When inserting the packaged coil assembly HGQi004 into the mold, the
pole insert \"razorback\" on the return end contacted the spacer bar,
keeping the return end of the coil from seating into the mold. A small
amount of press pressure was applied before this problem became evident.

This happened because the insert piece was about 1/8 inch longer than
the distance between the end of the pole insert and the end of the mold.
The technician who placed the insert piece into position (Imre) did not
know this, and placed the end of the bar flush with the end of the mold.

After this occurred the insert piece was moved to a position at which it
did not interfere with the pole insert. The coil was then cured
according to the standard procedure. A traveler modification will ensure
that the insert piece is positioned correctly in the future.

**4. Popped strand at parting plane near end.**

On coil HGQi004, there was a popped strand (a strand which had come out
of lay) on the parting plane turn, on the return end (turn enter side).
It began about 2 cm inside the area covered by the saddle, and extended
to about 2 cm beyond the area covered by the saddle.

This may have occurred as a result of coil deflections when the
interference occurred between the pole insert and the curing mold insert
piece (from item #3 above) although there is no way to be sure. The coil
was rejected and used on the mechanical model. However, one other
subsequent coil curing (coil HGQi007) showed the same problem (again
only after curing), only not as severe. On coil HGQi007, the strand was
able to be moved back into the proper position by technicians and was
used on HGQ01.

A possible cause for this is related to the end hold-down design. The
current finger is able to hold down turns where they cross over the top
of the mandrel, but does not hold down turns well in other areas. As a
result, wound coils have turns which lift off the mandrel by as much as
5mm (0.2in). These turns are then made to conform to the mandrel by the
curing mold.

The condition is undesirable for several reasons. Applying downward
force to an unsupported turn can easily cause popped strands while
winding. In the curing mold, the last wound turn, at least, is
unsupported when this downward force is applied. The turns are hidden
from view by the tooling, and strand problems cannot be monitored.

Also, if the turns are wound in a position off the mandrel, the length
of cable in the turn is not sufficient for the turn when it is finally
forced to the mandrel. This may cause higher coil springback as the
turns are stretched by the curing forces. Finally, the BEND program
designs each turn to lie on the mandrel. Relative strand movement within
the cable will not be the same in turns that are wound off the mandrel,
and may result in strand displacement or differential tension while
curing.

The new hold-down tooling design will incorporate a means to apply
downward force at any point along the turn. While some lift off the
mandrel may still be expected in such stiff cable, experience at CERN
indicates that the new tooling design will minimize the problem, and
will allow any strand displacements to be discovered and addressed while
winding.

The new tooling will not be available for use until magnet HGQ03 is
wound. the HGQ02 coils will continue to be wound using the HGQ01 tooling
with the modified procedure as stated in (II, C, 1) above.

**5. Poorly seated end saddles.**

The saddle did not properly seat on several of the early inner coils.
The worst case was on coil HGQi005, where there was about a 6mm gap
between the end of the last turn and the saddle on the return end. On
most other coils, this gap was between .1 and .5 mm. This problem was
solved, we believe, by modifying the curing procedure.

The curing procedure originally called for the lower platen pressure to
be increased to 1000 pump psi (about 1500 coil psi) before applying end
loading. It is likely that the platen pressure is too high to allow the
end cylinders to seat the saddles. A new procedure, designed to ensure
end closure, which includes higher end loading, less mandrel pressure
when end loading is applied, and a pressure cycling at high temperature
has been written.

Incidentally, during the SSC short model program, we had to modify the
curing procedure several times and try several different loading
sequences before we arrived at an adequate balance between platen,
mandrel and end pressures.

All coils with improper saddle seating had the saddles removed,
reseated, and were recured using the modified curing procedure. The
traveler must be changed to reflect the new procedure (shown below). The
temperatures shown below reflect coils cured at 135C. The high
temperature procedure will also reflect these changes.

The turn hold-down problems outline in the above section are also a
possible contributor to the end saddle seating problem. The last-wound
group in any coil is the one in which turn lift off the mandrel is the
worst. It is against this improperly positioned group that the saddle
fits. The saddle is designed to fit against turns conforming to the
mandrel, at installation, the saddle-to-group fit is not good.

Later, when the turns are forced down by the curing mold, the movement
of the turns may well result in a axial displacement of the saddles. An
additional effect of this turn conformance by the mold is that the
feather edges of the saddles are sometimes drawn in and folded under the
group. While this effect has not appeared to cause any serious coil
problems, the potential for insulation damage is very real.

**[New curing cycle 7-25-97]{.underline}**

R. Bossert & J. Brandt

Start with inner coil #HGQi007.

> A. Before installing end retainers, mark position of end saddle
> pushers at ends of mandrel with a permanent marker.
>
> B. Complete packaging according to traveler and put mold into press.
>
> C. Make sure end saddle pushers are inserted up to mark on pushers.
>
> D. Close the last two mandrel cylinder valves on each end.
>
> E. Apply 2500 pump psi. mandrel pressure.
>
> F. Apply 1000 pump psi. platen pressure.
>
> G. Lower platen pressure to 500 pump psi.
>
> H. Lower mandrel pressure to 500 pump psi.
>
> I. Apply 1500 pump psi end cylinder pressure.
>
> J. Increase mandrel pressure to 2500 pump psi.
>
> K. Increase platen pressure to 1000 pump psi.
>
> L. Check gaps between mold stops and upper platen.
>
> M. Start heat cycle.
>
> N. When temperature reaches 93C, lower platen pressure to 500 pump
> psi.
>
> O. Lower mandrel pressure to 500 pump psi.
>
> P. Verify that end pressure is still 1500 pump psi. Increase to 1500
> pump psi if necessary.
>
> Q. Open last two mandrel cylinder valves on each end.
>
> R. Increase mandrel pressure to 2500 pump psi.
>
> S. Increase platen pressure to 8500 psi.
>
> T. Check gaps between mold stops and upper platen.
>
> U. When temperature reaches 135C, check gaps between mold stops and
> upper platen.
>
> V. After one hour at 135C, turn off heaters. Maintain all pressures
> until coil is below 49C (120F).
>
> W. After coil is below 49C, release end pressure.
>
> X. Release platen pressure.
>
> Y. Release mandrel pressure.
>
> Z. Remove mold from press.

**6. Outer Wedge section mistakenly placed in Inner Coil**

After inner coil #HGQi006 was recured (a second time) and removed from
mandrel it was noticed that a section of outer wedge had been placed in
the inner coil.

Currently, in the HGQ program, the inner and outer wedges are insulated
differently. At an earlier time in the program, outer wedges were
insulated with the same system now used only for the inner wedges. When
the insulation system was changed, one of the outer wedges was not
re-insulated. When coil HGQi006 was being wound and the wedge was being
placed in the coil, technicians relied on the different insulation
system of the wedges to identify this piece as an inner wedge.

When the final coil inspection was made before curing, only the outside
surface of the coil is visible. The inner and outer wedges, from the
outside, look nearly identical to the naked eye. The wedges were
inspected and this step was signed, but the difference between the
wedges was not detected.

The wedge was removed and replaced and the coil was recured. It was
ultimately scrapped.

To prevent reoccurrence, a change to the traveler is necessary.
Inspection of wedges is covered in two steps in the traveler, #6.8 and
#7.3. Step 6.8 requires the technicians to identify that the wedges have
the correct insulation system and have the \"witness notch\" in the
correct orientation to assure that it is not in backwards. This step was
followed, as stated above, but the inner surface was not checked. A
check of the inside surface of the wedge should be added to this step to
insure that the correct wedge is being used. The wedges are similar and
there is no part number marked on them, but the difference between the
inner surfaces is clear.

Also, in step #7.3, the production engineer is required to check whether
the witness marks are in the correct orientation. This was done, but the
slight difference between position of the inner and outer wedge witness
marks was not noticed. There is no other way to tell the difference
between an inner and outer wedge at this point. I believe we can inspect
closely at this step (with a magnifying glass if necessary) to
discriminate between the inner and outer wedge witness marks. We could
also try to create a better way of identifying the wedges from the
outside.

**7. Curing Shim Overlap**

Inner coil HGQi005 was cured on 8-14-97 according to the new curing
procedure to properly seat the end saddles. After removing from mold, it
was discovered that two curing shims had overlapped, causing a
depression in a straight section of the coil.

The curing shims, which are placed between the coil and the arc pushers
during curing, are currently made in several short pieces. Before the
packaged coil assembly is placed into the curing mold, the position of
the shims on each end of the mandrel is checked to see if the shims are
in position. This checking was done, but on the lead end \"A\" side, it
is difficult to see whether the shim is at its proper longitudinal
position. Either it was not seen correctly or the shim moved out of
place during the positioning into the curing mold.

On a standard curing, the coil is still \"fluffy\" or larger than the
azimuthal space it is made to fit into. Since it is packed tightly into
this space, it is difficult for the curing shims to move out of place
while the packaged assembly is being placed into the curing mold. On a
recuring, the coil is already compressed. There is therefore some free
space within which the shim can move, allowing it to more easily come
out of place during handling.

New curing shims have now been manufactured in one piece, making it
impossible to have the sections overlap. It is desirable to use full
length curing shims for both short and long magnets. It is not yet known
whether we can obtain curing shims for long magnets which meet our
tolerance specifications.

**8. Discoloration of cable on all coils.**

Discoloration of cable, after curing, has been observed on cable used in
the HGQ program. This appears to be true regardless of curing cycle
length and regardless of adhesive used (epoxy or polyimide).

This discoloration seems to be the result of something deposited onto
the cable during cable manufacturing. We do not clean the HGQ cable at
FNAL as we did previously with the freon ultrasonic process used on SSC,
Tevatron and Low Beta cable.

We need to determine:

a.) The cause of the discoloration.

b.) Whether this problem is sufficient to affect magnet performance.

c.) If so, what cleaning method we can use to eliminate it.

We have tried several methods of \"cleaning\" the cable. Ten stacks have
been produced with cable uncleaned, cleaned thoroughly by hand with
alcohol, cleaned thoroughly by hand with \"Axarel 6100\" (the cleaning
fluid used by the SSC) and cleaned with the in-line SSC cable cleaning
module using Axarel 6100. Cable color has been noted after curing.
Results have been mixed. The alcohol seems to clean the cable best,
while the Axarel removes some of the discoloration, but deposits Axarel
onto the cable, which does not completely evaporate, creating another
unknown condition.

We are, temporarily, cleaning the cable for HGQ02 with Axarel 6100 in
the SSC cleaning module before insulation. The cable in magnet HGQ01 was
not cleaned.

There is also a venting problem in Industrial #3 to resolve if the SSC
module and Axarel 6100 is to be the permanent solution.

**9. Coil size problems and measurement discrepancies.**

All coils, both inner and outer, are cured in a mold cavities which are
designed to have the precise cross section of the finished package after
the coils are assembled with the final design preload applied. The coils
are cured under radial and azimuthal pressures which are similar (we
believe) to those pressures to which the coils will eventually be
subjected after they are collared and keyed.

After curing, azimuthal measurements of the coils are taken at a range
of pressures encompassing those which the magnet will experience during
operation. Specifically, the coils are measured at pressures of 8000
psi, 10000 psi, 12000 psi and 14000 psi (55 MPa, 70MPa, 83 MPa, 97 MPa).
The design pressures for inner and outer coils when cold and unpowered
for HGQ01 were 12000 psi (83MPa) for the inner coils and 10000 psi (70
MPa) for the outer coils. When we refer to a coil\'s \"azimuthal size\"
we are referring to its size at these particular pressures. We will
probably change the design pressure for outer coils to 12000 psi (83MPa)
for HGQ02, so numbers listed below are all at 12000 psi.

Mean size (with respect to nominal) and modulus of coils produced so far
in the HGQ program are:

Inner Coils Size \@12000 psi Modulus (8000-12000 psi) Cavity Size(in)

HGQi001-e/2 -.0025in,-60uM 820ksi,5.8GPa .000

HGQi002-e/1 -.0005in, -12uM 710ksi, 4.9GPa .000

HGQi003-e/1 -.0002in,-5uM 710ksi, 4.9GPa .000

HGQi004-e/1 +.0005in, +14uM 610ksi, 4.2GPa .000

HGQi005-e/1 +.0005in, +13uM 610ksi, 4.2GPa .000

HGQi006-e/3 -.0045in, -117uM 850ksi, 6.0GPa .000

HGQi007-e/1 -.003in, -75uM 590ksi, 4.1GPa .000

HGQi008-e/1 -.0035 in, -90uM 620ksi, 4.2GPa .000

HGQi009-p/1 -.005in,-130uM 600ksi,4.1GPa .000

HGQi010-e/1 -.002 in, 46uM 610ksi, 4.2GPa .000

HGQi011-e/1 -.0015in,-41uM 600ksi, 4.1GPa .000

HGQi012-p/1 +.0046,+117uM 660ksi,4.5GPa .000

HGQi013-p/1 -.004in,-100uM 590ksi,4.0GPa .000

Outer Coils Size \@12000 psi Modulus (8000-12000 psi) Cavity Size(in)

HGQo001-e/1 +.009in, +235uM 1020ksi,7.0GPa .000 HGQo002-e/1 +.019 in,
+475uM 1020ksi,7.0GPa .000

HGQo003-e/1 +.019 in, +485uM 1090ksi, 7.6GPa .000

HGQo004-e/1 +.012in,+300uM 1600ksi,10.5GPa -.015

HGQo005-e/1 +.020in, +505uM 1060ksi, 7.3GPa .000

HGQo006-e/1 +.020in, +505uM 1060ksi, 7.3GPa .000

HGQo007-p/1 +.016in, +400uM 870ksi,6.0GPa .000

2nd cure-p/2 +.015in,+370uM 1120ksi,7.7GPa -.005

3rd cure-p/3 +.013in,+325uM 1260ksi,8.7GPa -.010

4th cure-p/4 +.010in,+260uM 1480ksi,10.2GPa -.015

5th cure-p/5 +.0075in,195uM 1840ksi,12.7GPa -.020

HGQo008-p/1 +.006in,+155uM 1360ksi,9.4GPa -.020

HGQo009-p/1 +.0085in,+215uM 1404ksi,9.6Gpa -.020

e = epoxy adhesive p = polyimide adhesive

number after slash indicates measurement number, i.e., 1st time
measured, 2nd time measured, etc.

The early inner coils, when cured with the nominal cavity size, were
about the correct size as measured, As more coils were cured, azimuthal
size tended to decrease (this is a typical phenomena when new tooling is
introduced, as exhibited by SSC 50mm dipole coils). We now are making
coils which are, according to the measuring fixture, about .005 inches
undersize. Since the strain gauges tell us that the coils need to be
shimmed, to obtain the proper preload, to .014 in oversize, the inner
coils are about .019 smaller azimuthally than desired. We cannot correct
this by increasing curing mold cavity size, because curing mold
pressures will become lower than desired. HGQ02 will be shimmed, as was
HGQ01, during assembly to obtain the proper preload.

The early outer coils, when cured with the nominal cavity size, were
about .019 inches larger than the nominal size desired. As more coils
were cured, azimuthal size decreased slightly. In addition, by changing
the shim size, we reduced the mold cavity by .020. This cavity reduction
gave us approximately an additional .008 in azimuthal coil size
reduction. It also increased the curing pressure used to mold the coils.
This increase has other effects, which are discussed below in (II,C,10).
We now are making coils which are, according to the measuring fixture,
about .008 inches oversize. Since the strain gauges tell us that the
coils need to be shimmed, to obtain the proper preload, to .010 in
oversize, the outer coils are now being made to about the azimuthal size
desired.

We still do not understand why, when coils are measured in the azimuthal
measuring fixture, they do not agree with the predictions for preload
(as read by strain gauges) indicated by the finite element model. We
also do not understand why the inner and outer coils do not measure the
same size compared to their respective cavity sizes. A proposed plan to
understand these problems is shown below.

Plan to solve outer cable size problems:

> a\) Understand bare cable size as manufactured with respect to
> nominal. Look at cable size data from LBL. Measure a series of \"bare
> cable \" ten stacks.
>
> b\) Understand differences between bare and insulated cable sizes.
> Measure cable insulation thickness. Do an \"insulated\" ten stack with
> the nominal cable insulation system.
>
> c\) Understand actual tooling sizes with respect to nominal. Get
> tooling parts drawings and inspection reports. Check the drawings and
> compare the tolerance buildup from the inspection reports.
>
> d\) Measure a coil in the curing press, using feeler gauges and pump
> psi to determine coil size. Look at \"press closing pressure\" from
> the traveler data of all HGQ outer coils and tabulate.
>
> e\) Measure the same coil (from d) in the coil measuring, or
> \"sizing\" fixture. Compare results.
>
> f\) Determine coil size from the mechanical model and HGQ01 based on
> strain gauge and collar deflection measurements. Compare results with
> the sizing fixture measurements of the same coils (and curing press
> closing pressures, if available). Determine if any measurement errors
> exist in the three methods of measurement and decide which, if any,
> measurement is correct.
>
> g\) Cure and analyze ten stacks with various insulation systems to
> understand the effect of insulation variations (particularly gaps
> between wraps) on cable size.
>
> h\) Analyze ten stacks cured with various pressures, but the same
> insulation system.
>
> i\) Draw conclusion. Write a technical note explaining the results.

**10. Damage to Outer Coil End Parts**

Curing pressures on coil HGQo004 caused significant damage to end parts.
Keys and saddles on both ends showed fracture cracks. Inside surfaces of
keys showed deformation or \"waviness\", indicative of overcompression.

This problem is due to excessive curing pressure. Platen pressure of
8500 pump psi was needed to close the press when curing this coil. This
is an equivalent of 13200 azimuthal coil psi (91 MPa).

High pressures were used on this coil because earlier coils in this
series (HGQo002 and HGQo003) were oversize by .019 inches azimuthally
and had low modulus. .015 inches of shim was removed from the curing
mold to reduce the azimuthal coil size.

The excessive curing pressures on coil HGQo004 also caused severe damage
to the cable on the inside surface of the coil. The area where the turn
curves through the lead end key has had the inside surface of the
insulation scraped off. The copper had been removed from the inside edge
of the cable, and superconducting material was visible.

This coil was not used in a magnet. Ends were cut off and potted and
sectioned to observe end part placement. Straight sections were used in
the HGQ mechanical model.

The .015 shim was be returned to the curing mold for future coils. The
coils therefore continued to be oversize. A later coil, HGQo007, (with
Ultem parts) was cured repeatedly with various curing shims. Some end
part damage on this coil was caused by poor bonding of end parts to
cable and stretching of the coil to get it back on the mandrel for
recuring.

Damage with smaller cavity size and high curing pressures seemed to be
more extensive with the G-10 than with the Ultem, possibly because the
Ultem compressed, or flowed, more readily.

**11. End Part Adhesion on Polyimide Coils**

Magnet HGQ02 will use Ultem end parts and polyimide adhesive on the
cable insulation, instead of the G-10 end parts and epoxy cable
insulation used for magnet HGQ01. The recommended curing temperature for
he epoxy was 135C, while the recommended curing temperature for the
polyimide adhesive was 170C.

Early coils wound with Ultem end parts and polyimide cable insulation
showed end part adhesion to be very poor. Saddles typically came off
easily and the other parts did not adhere well. In some cases,
(particularly HGQo007) the lack of adhesion also caused significant end
part damage.

Deepak Chichili did tests with samples of G-10 and Ultem using their
respective adhesives at 135C for the G-10 and epoxy and 170, 180C and
190C for the Ultem and polyimide (reference \"Investigation of Bond
Strength of Polyimide Adhesive\" TD-98-004). Coils were also wound and
cured using polyimide and Ultem at 170C, 180C and 190C. It was
determined that the adhesive strength of the Ultem/polyimide bond
increases significantly with temperature, although never reaching the
level of the G-10/epoxy bond. It appears that we can achieve an adequate
bonding strength at 190C for the Ultem/polyimide coils. We will
therefore cure both the inner and outer HGQ02 coils at 190C.

It also appears that the smooth surface finish of the machined Ultem
parts makes bonding more difficult. We will experiment with altering the
surface finish of the Ultem parts to further improve the bonding
strength.

The bonding problem with polyimide end parts results in several
additional problems. The actual unbending of the turns allowed by the
poor adhesion is a potential danger to insulation. The kapton may stick
to the end parts and be peeled away from the cable. This might not be a
serious problem since the risk of shorts is minimal, but it is certainly
undesirable.

The lead end key is particularly vulnerable to cracking or displacement
when poorly bonded in the package. This actually happened on one outer
coil (HGQo007) when it was

repackaged onto the mandrel. The lack of bonding caused the two key
parts to act independently, cracking part A, and shifting it relative to
the preform and to part B.

The preform area needs to remain well bonded in between the two piece
key, especially if spot heaters will be attached in this area for future
magnets. The outer coil lead end key is the most vulnerable since the
preform is only bonded to one side, and against a removable shim on the
other side. The shim reserves space for the inner coil preform to be
routed through the outer coil later in magnet assembly.

The lack of bonding makes the inner coil filler easily displaced. The
polyimide adhesive is very dry and smooth when winding the coils, and
not tacky like the epoxy adhesive used on G-10 parts. The filler
normally wants to be dragged out of place by the winding of the turn
around it, and the polyimide adhesive provides no resistance to this.

With a gap left between the back of the filler and the wedge, the filler
will be much more likely to move into this gap with a smooth dry
adhesive. This actually happened on one inner coil, leaving several
turns unsupported for the length of the filler. Two possible solutions
exist for this filler displacement problem.

If the polyimide adhesive can be applied immediately before winding, it
may be tacky enough to retain the filler position, and prevent it from
moving back into the wedge gap. If this is not possible, or if the
adhesive fails to prevent movement anyway, the wedge may have to be
butted against the back of the filler. This will prevent filler
displacement, but will eliminate a desired gap for minimizing coil
distortion upon coil springback.

We will, on magnet HGQ02, eliminate the wedge gap on the lead end
against the filler to prevent movement of the filler.

**12. Curing Press Heating Cycle Problems**

The heating cycle for the initial practice coils (HGQi001 and HGQo001)
took significantly longer than expected. It took approximately 7 1/2
hours from the time the heaters were started at room temperature until
the coils reached 135C. Also, the temperature of the mold on the return
end (as read by thermocouples) lagged behind the temperature at the lead
end by approximately 8 degrees C.

The curing press resistance heating system was then reconfigured to
provide more power than was used on the practice coils (15000 vs. 5800
total watts). The HGQ coils could then be heated in the curing press to
135C in under 1 1/2 hours. The temperature gradient across the mold,
however, remained 8 degrees C. This was true of both the inner and outer
mold, and independent of the press into which the mold was placed or the
direction in which the mold was placed into the press. When temperatures
were increased to 170C, then to 180C and 190C, the temperature gradient
across the mold increased proportionally, to about 12C at 190C.

This problem was studied by Deepak Chichili, Igor Novitski and Dean
Conolly. (reference \"On the Temperature Gradient in the HGQ Cable
Curing Fixture, TD-98-005). It was discovered that the active element of
the resistance heaters, which were placed longitudinally through the
molds, was skewed to one side of the heaters. The amount of skew varied
from heater to heater. The heaters were therefore removed from both the
inner and outer molds, the position of the active element was measured,
and the heaters reinserted, with the active element of each heater
separately centered within the mold. This eliminated the temperature
gradient across the curing molds.

**13. Parting plane lead deterioration**

The parting plane lead, after it exits the coil area, extends at least a
meter. This heave piece of cable presents a handling problem, because
the condition of the cable can easily deteriorate during the magnet
assembly process, making it difficult to for the quadrant splices and
possibly contributing to cable instability in this area during
operation. This became a problem during the assembly of HGQ01. Since
HGQ02 coils use polyimide insulation and

Ultem end parts, which have a weaker bonding strength than the
G-10/epoxy, this problem can only become more severe.

To reduce this deterioration, we will tin the parting plane lead before
curing, and solder the copper stabilizer to the lead immediately after
curing (as described in IX,B). Clamps which hold the lead to the coil
and can remain with the coil during handling will also be designed and
fabricated, although they may not e ready for HGQ02.

**D. Voltage Tap Installation**

**1. Grooving end Parts**

There are several voltage taps in the outer coil of the HGQ magnet for
which the wires must travel between the inner and outer layers until
they are fed out through the external pole splice cooling channel. In
order to provide room for these wires, grooves must be cut into some of
the end parts . This was done by hand by technicians after the coils
were cured on magnet HGQ01. It will again be done by hand by technicians
for HGQ02, but before the coils are wound. There is no provision in the
traveler for this operation, but since it is done before the magnet
production actually starts, documentation on the drawing is believed
sufficient.

**2. Changes in Procedure to decrease short potential**

The voltage tap installation procedure used in magnet HGQ01 is a
duplication of the SSC dipole procedure. To apply a voltage tap, the
kapton insulation on the bottom of a cable is scraped away with sharp
knife until the bare cable is exposed. The tap is then soldered onto the
cable with a soldering gun.

During the assembly of magnet HGQ01, at least two turn-to-turn shorts
occurred. There is a good chance that both of these shorts were due to
solder from voltage taps. A new procedure has been created to decrease
the potential for shorts related to taps.

The new procedure specifies that the kapton insulation be cut
longitudinally at the center of the narrow edge of the cable, instead of
scraped away. This will make accidental scraping of insulation off the
adjacent turn much less likely. It also allows the remaining kapton to
be folded back, providing an insulating barrier so that solder is less
likely to flow onto the next turn. This procedure will be used on magnet
HGQ02. It has not yet been formally documented.

**III. Coil Insulation and Ground Wrap**

**A. Manufacturing problems with ground wrap**

Three of the ground wrap pieces needed for magnet HGQ01 were rejected
due to dimensional inaccuracies. The manufacturer ultimately failed to
make complete parts within tolerance. Instead, the parts were made
creased, but not folded. Technicians in Industrial #3 were able to fold
the parts by hand within the accuracy required.

Ultimately, another manufacturer will make complete parts within our
specifications. For magnet HGQ02, we will still use the partially
completed parts from the original manufacturer, folded by technicians at
FNAL.

**B. Manufacturing Problems with strip Heaters**

The original design for HGQ01 called for a double strip stainless steel
heating element, sandwiched between two pieces of kapton, folded across
the parting plane on the return end within the saddle area not covered
by the coil. An alternate, single element design was manufactured in
case the double element one was not acceptable. The heaters were placed
radially between the inner and outer layers.

The manufacturer failed to successfully make the double element strips,
and will not make any further attempts, so the single element heaters
were used. These need to be terminated by rolling up the end of the
strips within the saddles on both ends, so slots needed to be cut into
the return end saddles as well as the lead end. This was done by hand on
the production floor for magnet HGQ01.

For Magnet HGQ02, the single element heaters will also be used, but will
be placed both between the outer layer and the collars and between the
inner and outer layers. End saddles, both inner and outer, need to be
modified before coils can be wound. These modifications will be done on
the production floor for magnet HGQ02 and are documented in drawings. As
with the grooves in the end parts for voltage taps, the modifications
will be done before coil fabrication begins.

**C. Preload Adjustment Shims**

Bearing strips (or collaring shims) needed to be shimmed appropriately
to obtain the proper preload on all coils for magnet HGQ01. The shim
sizes used were based on experiments done with a mechanical model.

The mechanical model was collared and keyed three times, each time using
the same set of coils of known azimuthal size. Bearing strips were
shimmed to obtain a certain preload based on finite element
calculations. The coil preload was then read by strain gauges.
Relationships between shim sizes, measured coil sizes, and preload
measured by strain gauges allows us to understand how much the coils
need to be shimmed to obtain the proper preload. Magnet HGQ01 was then
shimmed to the same preload, taking into account the difference in
measured size between the mechanical model coils and the HGQ01 coils. A
complete report on the mechanical model study is available in TD-97-042
\"HGQ Mechanical Model Results - Synopsis\", T. Heger/J. Ozelis.

Coil and shim sizes used for HGQ01 are described below:

**[Collaring Shims for HGQ01]{.underline}**

R. Bossert 9-15-97

Inner coils needed to be shimmed up (larger) from nominal by 350 microns
(14 mils) on each side of each coil. Two of the inner coils (HGQi002 and
HGQi003) measured the nominal azimuthal size at the design pressure of
85 MPa (12000 psi). These coils had .014 inches of kapton added to the
parting plane on each side (the kapton extends the entire length of the
coil, from end of saddle to end of saddle). The other two inner coils
(HGQi007 and HGQi008) measured approximately .003 inches smaller than
the nominal azimuthal size at the design pressure. They each had .017
inches of kapton added to the parting plane on each side, also extending
from end of saddle to end of saddle. The standard (nominal size) inner
bearing strips were at the poles on all inner coils.

Outer coils needed to be shimmed up (larger) from nominal by 160 microns
(about 6 mils). All four outer coils (HGQo002, HGQo003, HGQo005 and
HGQo006) were approximately .019 inches larger than the nominal
azimuthal size at the design pressure of 70 MPa (10000 psi).

All four outer coils therefore needed to have .013 inches removed
azimuthally on each side. We could only remove .003 inches of ground
wrap at the parting plane and still have a

sufficient amount left for electrical insulation, so, in the magnet
body, we removed all the material from the poles.

\"Special\" bearing strips were fabricated for the outer coils which
were .019 inches smaller than the original design size. We used these,
and added .006 inches of kapton at the poles to give us the total of
.013 inches removed from the poles. At the ends (from back of key to
back of saddle), we did not have bearing strips, so could not remove
material from the poles. There, we removed .003 inches from the parting
plane (as much as we could), then reduced the amount of radial kapton
around the outside surface of the outer coil to achieve the rest of the
preload reduction. The radial amount we removed was determined by
analysis of the FEA done by Tricia Heger and/or Igor Novitski. We needed
to know this number before we collared, because the collaring process
included full rounds on the return end.

So in summary:

Inner coils: Shimmed up by 350 microns (+.014 inches)

HGQi002 and HGQi003: Coil is (.000) with (+.014) kapton added to each
side at parting plane.

HGQi007 and HGQi008: Coil is (-.003) with (+.017) kapton added to each
side at parting plane.

Outer coils: shimmed up by 160 microns (+.006 inches)

HGQo002, HGQo003, HGQo005 and HGQo006 in body: Coil is (+.019) with
(-.019) removed from bearing strips and (+.006 kapton added to poles).

HGQo002, HGQo003, HGQo005 and HGQo006 on ends: Coil is (+.019) with
(-.003) kapton removed at parting plane and an amount (as yet
undetermined) of kapton removed radially to equal the remaining (-.010
inches) of azimuthal distance to be removed.

After collaring one strain gauge pack in magnet HGQ01, we concluded that
the outer coil preload was too low. The magnet was de-collared and .004
inches was added to the outer coil bearing strips, making the outer coil
package \"shimmed up\" by a total of 250 microns (.010 in.) instead of
the 160 microns originally planned.

**D. Bearing Strip Damage during keying.**

The bearing strips exhibited some damage, with varying degrees of
severity, during the keying of the mechanical model, causing us to
change the material of the strips.

Mechanical model results:

At the time HGQ01 was collared, the mechanical model had been pressed
twice. The bearing strips, by design, were brass on the inner coil and
\"full hard\" copper on the outer coil. They were each .050 inches (1.2
mm) thick.

First mechanical model pressing: Inner bearing strips were the design
thickness of .050 inch thick brass. Outer bearing strips were full hard
copper, machined from the design thickness of

.050 to a thickness of .037 inches (.94mm). Prestress during pressing is
shown below. This was a much lower prestress than we expected to, and
ultimately did, achieve in HGQ01.

Coil Before Springback Final after springback

Inner 6000-10000 psi (42-70MPa) 3000 psi (21MPa)

Outer 6000-9000 psi (42-62MPa) 2000 psi (14MPa)

On the first pressing, both the inner and outer bearing strips held up
well. Both were slightly scored on the azimuthal surface. The outer
strips had a slight amount of serration on the thin radial surface. The
serrations, at their worst, measured about 3-4 mils (75-100 microns)
deep. This might be unsatisfactory for the long term production
solution, but it would not cause us serious problems on the first model.

Second mechanical model pressing: Inner bearing strips were the design
thickness of .050 inch thick brass. Outer bearing strips were full hard
copper, at the design thickness of .050 inches (1.27mm). Prestress
during pressing is shown below. This was a much higher prestress than
was needed for HGQ01.

Coil Before Springback Final after springback

Inner 18400 psi (127 MPa) 14000 psi (97MPa)

Outer 17000-27000psi (117-186MPa) 15000-22000 psi (104-152 MPa)

On the second mechanical model pressing, the inner bearing strips still
held up pretty well, slightly more, but still not significant scoring.
The outer strips, however, were more severely damaged. Scoring on the
azimuthal surface and serrations on the radial edge, on the \"good\" end
(where the laminations did not \"chevron\", were no worse, and sometimes
less severe than, the worst areas of the first pressing. On the end
where chevroning took place, the scoring was severe and the edge
serrations are as deep as 10 mils (250 microns), with a raised area of
displaced material of another 10 mils (250 microns), making total
peak-to-peak variations as high as 20 mils (500 microns).

Our plans, on HGQ01, were to shim the bearing strips to achieve a
preload between these two extremes. The goal for HGQ01:

Coil Before Springback Final after springback

Inner 16000 psi (110 MPa) 12000 psi (83 MPa)

Outer 15000 psi (104 MPa) 10000 psi (70 MPa)

Jay Hoffman did tensile and hardness tests on samples of the two bearing
strips used in the mechanical model. The results were:

> Brass inner strips: Yield strength 49000 psi, Ultimate strength 79000
> psi (in tension). Young\'s modulus 15.9 x 10\^6 psi.
>
> Copper outer strips: Yield strength 36000 psi, Ultimate strength 47000
> psi (in tension). Young\'s modulus 16.1 x 10\^6 psi.

The copper measured lower than the specification for the material (it
should be minimum 45000 psi yield.)

Hardness on Rockwell \"B\" scale: Brass: 85.9

Copper: 52.8

Even though the preload in HGQ01 was not expected to be as high as on
mechanical model #2, the damage we saw was extensive enough to make us
decide to change the material for the outer strips from copper to
phosphor bronze. For HGQ01, then, the bearing strips were:

Inner bearing strips were the design thickness of .050 inch thick brass
(same as mechanical model). Outer bearing strips were phosphor bronze,
with a yield strength in excess of 110000 psi at a thickness of .032
inches (.81mm). They were made thin to compensate for the extremely
large outer coils in HGQ01.

Our reasoning was:

On HGQ01, the inner strips as designed were not a problem. The brass
held up during the pressing of mechanical model #2, so will be OK under
the lower pressures of HGQ01. On the outer strips, the phosphor bronze
we are using on HGQ01 is significantly stronger than the copper, but
thinner.

There were three potential problems:

1.) Scoring on the azimuthal surface.

2.) Bending stresses where the bearing strip bridges the laminations.

3.) Serrations on the radial surface.

1.) Scoring on the azimuthal surface was not considered a problem. The
collars on HGQ01 will not chevron and the phosphor bronze has a higher
yield strength and will be subjected to lesser pressures than Mechanical
Model #2. The scoring on the HGQ01 would therefore be less severe than
the non-chevroned area on MM2, which was not serious.

2.) Bending stresses on the phosphor bronze, since it is thinner, will
be greater per unit stress than with the copper. A quick calculation
indicates that the maximum stress in the phosphor bronze should be about
25000 psi. (Assuming fixed supports, 15000 coil psi and a gap of .06
inches.)

If the gap is assumed to be .08 inches because the die break on the
stamped lamination surface causes it not to be flat over it\'s whole .06
inch width, the stresses increase to 45000 psi, still significantly
below the yield strength of the material.) Deflection in this direction
is a small fraction of a mil.

3.) The serrations are harder to assess. If we compare the bronze strips
to the thick (.050 inch) copper strips used on MM2, the bronze is
thinner, but has a much higher yield strength.

Since they are in direct compression, they would be expected to yield at
a higher stress than the .050 copper. Since we were expecting stresses
roughly 25% lower than MM2, we considered the design acceptable.

There are two ways that the serrations could potentially be a threat to
magnet performance.

> 1.) If they are so deep that they cause the bearing strip to leave a
> significant part of the inside edge of the coil uncovered. Based on
> the measurements of the serration depth in the mechanical model, this
> didn\'t appear to be a problem.
>
> 2.) If the sharp serrated edge punctures the ground insulation,
> causing a short to ground. This didn\'t look like a problem either.
> Inspection of the bearing strips from the mechanical models indicated
> that the sharp edges always go toward the collars, with the surface
> contacting the ground wrap remaining smooth.

After \"massaging\" the collared coil, the magnet was de-collared (to
add shim to the outer bearing strips, as noted above in (III,C). The
inner and outer bearing strips were inspected at that time. Slight
scoring, but no significant damage was evident.

Magnet HGQ02 will use the same material (brass for inner, phosphor
bronze for the outer) as HGQ01. The outer strips will be thicker
(probably the design of .050) because the combination of coils size
reduction and necessary overshimming makes the thicker bearing strips
more desirable.

**E. End ground wrap.**

Many small pieces of coil insulation and ground wrap need to be placed
around the ends area to terminate the ends of the body ground insulation
pieces. Special care must be taken to ensure that no ground short paths
exist between the many places that these parts must be split to allow
assembly. The end ground configuration is shown in drawing
5520-MC-344376.

This operation went smoothly. In several places, pieces need to be
trimmed by hand to fit on an individual basis. There were some minor
discrepancies in the traveler, where the wrong part numbers were called
out. These will be corrected for magnet HGQ02.

**IV. Collaring**

**A. Collar Stacking**

After the magnet is assembled and shimmed, it is tipped vertically and
collars, including those for strain and capacitor gauges, are stacked by
hand along the packaged coil assembly. The collaring of a quadrupole is
performed vertically with a pair of laminations stacked opposing each
other. The next layer pair of laminations are stacked 90∞ out of phase
with the layer below it. This alternating of layers is repeated until
collaring is complete. A large nut at the end of the collaring mandrel
is used to hold the assembly together.

**1. Collar lamination Flatness**

Collars were stamped by Plainfield Tool who were the low bidders. They
have stamped laminations successfully for us many times in the past. The
drawing called for a 0.005" flatness that was later changed to 0.010"
and then to 0.015". (For reference, SSC collars used 0.005" flatness and
LBQ used 0.001") Inspection of the laminations showed out of flatness
conditions of as much as 0.042". The vendor stated that the parts are
coming out of the die flat and within specification however they believe
the deburring operation causes the out of flatness condition. The
initial shipment of collars did not meet the flatness requirement but
were accepted as they were deemed usable for the first model magnet. A
meeting with Plainfield on December 11, 1997 was held and they were
charged with identifying the process that caused the flatness problem,
look at possibly straightening laminations on hand, and responding to
FNAL with a concise plan to supply future laminations in accordance with
FNAL's specifications. REF: Memo from Nelson Sample 12/12/97.

Magnet HGQ02 will use collar laminations of the same quality as were
used on magnet HGQ01. They are in stock.

**2. Grooves for strain gauge wires**

Lateral grooves need to be placed into the collar laminations to route
strain gauge wires from their positions within the magnet to the slots
that are used to route them to their respective connectors. These
grooves consisted of one modified lamination on magnet HGQ01. They were
not large enough. Collar laminations had to be removed and modified to
accept the wires. On magnet HGQ02, two laminations will be modified
prior to the collaring process, thereby avoiding the delay incurred on
HGQ01.

**3. Modifications to Full Round Laminations**

The return end of magnet HGQ01 used \"full round\" collars, or collar
laminations with the pole area removed, to enclose the coil assemblies.
Problems were encountered when these collars were places onto the coil
assembly. Technicians were not able to close them sufficiently by hand
to allow the coil to be pressed. \"C\" clamps were necessary to seat the
laminations onto the coil assembly.

In addition, when the laminations were pressed onto the coils, the sharp
inside corners of the steel cause severe damage to the kapton ground
insulation layers on the end. The laminations needed to be removed, and
the sharp corners rounded by about 4mm radius. These laminations will be
modified before the collaring process for magnet HGQ02.

**V. Keying**

**A. Special Keying Procedure**

The procedure for collaring HGQ01 was similar to that used on Low Beta
Quadrupoles. The press was modified, within the constraints of the
hydraulic pressure available, to obtain the preload needed. As a result,
the \"stamp\", or longitudinal area which could be pressed for keying at
one time was reduced to 4 inches. The key length was therefore limited
to 3 inches.

This did not create any significant problems in keying the body, but the
return end (where we are using full round laminations and therefore must
press and key as in the straight section) becomes more difficult. The
area in which the turns are enclosed within the curved surfaces of the
end parts is more than 3 inches long. We consequently are forced to
press the end in segments, causing large temporary differences in
diameter which occur within the area encompassed by the end windings.
This can potentially cause movement between turns and create shorts.

A special procedure was therefore used to press the end. The procedure
is shown below. It was used on HGQ01 and will be used on HGQ02. It is
being incorporated into the keying traveler.

**[Keying Procedure for HGQ01]{.underline}**

R. Bossert 10-8-97

[Keying Magnet Body]{.underline}

Note: During entire massaging and keying process, monitor total magnet
resistance. Check at each step to verify that no turn-to-turn shorts
have occurred.

1.) Record total magnet resistance in traveler.

2.) \"Massage\" entire coil twice, once at 1500 pump psi and then at
3000 pump psi, beginning at return end (bottom). Take all beam and
capacitor gauge measurements at 3000 pump psi during massaging. Gauge
readings only need to be taken when pressing the area in which that
particular gauge is placed.

3.) Go to area where inner beam gauges are placed. Press till keys can
be inserted. Start with 3000 main pump psi and increase in 1000 pump psi
increments. Take inner beam gauge measurements at each pressure. Verify
that inner coil preload when keys can be inserted is within the
acceptable window of 14000 - 18000 psi (before springback). Release
pressure, but do not insert keys.

4.) Go to area where outer beam gauges are placed. Press till keys can
be inserted. Start with 3000 main pump psi and increase in 1000 pump psi
increments. Take outer beam gauge measurements at each pressure. Verify
that outer coil preload when keys can be inserted is within the
acceptable window of 12000 - 16000 psi (before springback). Insert keys.

5.) Continue keying from position of outer beam gauges toward lead end
of magnet (top).

6.) When two key lengths away from end of straight section on lead end,
cut special length key to end 3 inches away from end of straight
section. Insert the short key second to last. Use a full length (3 inch)
key at the end to be aligned flush with the end of the last collar. If
it protrudes slightly, it can be trimmed after removal from press.

7.) Move back to section just below outer beam gauges. Continue keying
toward return end of magnet (bottom).

8.) When one key length away from end of straight section (that is, the
back of the key extension) on return end, cut special length key to end
1 1/4 inches away from end of straight section. Insert the short key
last. Do not key the last 1 1/4 inches of straight section.

9.) Record total magnet resistance in traveler.

[Keying Return End]{.underline}

1.) Check to ensure full round collars are aligned azimuthally with body
collars.

2.) Record total resistance of magnet in traveler.

3.) Massage return end twice, once at 1500 pump psi and again at 3000
pump psi..

> Do each massage the end in two steps: Start by pressing the 3 1/2 inch
> section beginning with the end of the saddle as shown in Figure 1.
> (the main press pushers, being 4 inches long, will have to extend 1/2
> inch beyond the end of the saddle). Then press the remaining 4 inches
> of unkeyed section.

![](media/image1.pct){width="3.9722222222222223in"
height="3.5833333333333335in"}

[Figure 1. Main Pusher positions for massaging.]{.underline}

4.) Move the main pushers 1/2 inch from the second massaging position
toward the lead end of the magnet (to surround the 1st keying position
shown in Figure 2). With the main pump pressure at 3000 psi., partially
insert keys into the first key position (the section encompassing the
first 3 inches from the magnet body). Up to 3000 pump psi may be used on
the cylinders which drive in the keys.

5.) Move the main pushers 3 inches toward the end of the magnet, and
partially insert the keys into the second key position at 3000 main pump
psi. Up to 3000 pump psi may be used on the cylinders which drive in the
keys.

![](media/image2.pct){width="4.5in" height="4.055555555555555in"}

[Figure 2. Key Positions]{.underline}

6.) Move the main pushers from the 2nd keying position back to the first
keying position and press until the keys can be inserted, or 5500 main
pump psi, whichever is lower. If the keys can be inserted at 5500 main
pump psi, insert them and skip to step 10. If not, remove the keys from
the entire end area, starting with keying position #1, and remove from
press.

7.) Remove the full round collars.

8.) Remove one layer of .005 inch thick ground wrap from around the end
area.

9\. Start again at step #1 of the return end keying procedure.

10.) Move the main pushers 3 inches toward the end of the magnet, and
press until keys can be inserted. Do not increase main platen pressure
above 5500 pump psi. Insert keys into the

2nd key position shown on Figure 2. Up to 3000 pump psi may be used on
the cylinders which drive in the keys.

11.) Move the main pushers 3 inches toward the end of the magnet, and
press until keys can be inserted. Do not increase main platen pressure
above 5500 pump psi. Insert keys into the 3rd key position shown on
Figure 2. Up to 3000 pump psi may be used on the cylinders which drive
in the keys. The extra key may protrude beyond the end of the magnet. It
can be cut off after the magnet is removed from the press.

**B. \"Toggling\" and collar measurements in the press.**

The keying procedure was refined by Igor Novitski to include one or more
\"toggling\" steps during every key insertion. This method allowed
\"springback\" to be minimized.

Traditionally, the collared coil is pressed by the main hydraulic press
to a pressure which allows the keys to be fully inserted. After the keys
are inserted, and the main press pressured is released, internal
deflections in the collared coil assembly occur, and the coil preload
decreases. It is desirable to avoid overcompression as much as possible,
because higher pressures increase risks, particularly of turn-to-turn
shorts, to the coils.

When using the \"toggling\" method, measurements are taken of the collar
outside dimensions during pressing. When the size indicates that the
tapered keys can just begin to be inserted, keys are partially inserted,
using a moderate amount of pressure. The main pusher pressure is then
removed, while keeping the pressure on the tapered keys. Then the main
pressure is reapplied and key pressure is removed. After increasing the
main pressure to the next level, the key pressure is reapplied, keys are
inserted further and the main pressure removed again. The process
continues until the keys are fully inserted.

This process worked well on HGQ01. It will be used on HGQ02.

**C. Spring Clip Problems**

Minor problems were encountered with the spring clips used to hold the
keys in position during insertion. The spring clips are part of the key
insertion mechanism and are meant to retract when the mechanism contacts
the collar laminations as the keys are being inserted. The clops
actually released the keys before they were sufficiently engaged in the
slots. The result was that the keys became mis-positioned or even
dropped out of place altogether.

The first attempt to solve this problem was to attach a stiff mylar
sheet under the insertion mechanism which would keep the keys from
falling. This did not work well because the mylar sometimes interfered
with key placement, and also because the mylar prevented the technicians
from seeing the previously installed key strings. This created a danger
of key overlaps or excessive gaps between keys in any of the eight key
strings.

Finally the mylar was removed and keys were inserted into the collars by
hand. They were pushed in firmly enough so that friction kept them in
place, and the insertion mechanisms were than used to push the keys all
the way in. With this method, the technicians were able to insure key
position, and maintain continuous contact between keys in all key
strings.

An automated solution to this problem will be difficult to develop. The
tolerance in key lengths and gaps could result in key strings of
different length, requiring independent axial adjustment of each
insertion mechanism to control key gaps or overlaps. The mechanism
itself interferes with the ability to observe and align to the
previously inserted keys.

The tooling developed for the long model collaring is intended to
address this issue. If the insertion mechanisms are retained as they
are, an automated method will be developed. Horizontal collaring and
other methods are being considered for the new long model tooling. If
incorporated, this key string problem may be eliminated.

In any case, the methods used in HGQ01 will be repeated for HGQ02.

**D. End Spacer Problems**

Specially machined cylinders are necessary to take up the space during
keying that will eventually be taken by the collet end clamp on the lead
end and the full round laminations on the return end. These parts, as
fabricated, had to be modified to fit the magnet. The length on the
return end had to be changed and the inside diameter had to be bored
out. These modifications have been completed. The parts should accept
magnet HGQ02 without further modification.

**E. Hydraulic Cylinder Synchronization**

During mechanical model tests, a problem was observed concerning
hydraulic cylinder extension speeds. All cylinders are manifolded
together to ensure pressure equalization, but each unloaded cylinder
extends at a different rate. The faster cylinders contact the
laminations first, and tend to force the assembly away from the press
center. The slower cylinders then contact the laminations in the wrong
place.

The lamination tabs have angled sides and usually contact the cylinder
pushers in a position close enough to allow tab engagement. The angled
sides then force the collars to recenter the assembly in the press.
However, once during the collaring of the first magnet, the tabs failed
to engage the slots, and two cylinder pushers received minor damage from
edge contact.

The displaced pusher material from the edge indentations was easily
removed, and the technicians were able to prevent this from recurring by
closely observing tab engagements. However, this method is difficult
since the collared coil assembly sometimes has to be twisted to ensure
tab engagement. Misaligned tabs must bear against the angled pusher
surface and slide down it into proper position. This may result in
unusual collar loading, scuffing of laminations, and unwanted pusher
wear and side loading.

A simple solution for this problem was suggested by Bill Robatzek. A
needle valve on the inlet of each cylinder will allow the flow to the
faster cylinder to be reduced. Any other hydraulic synchronization
method is quite costly, and are usually not designed to control piston
extension on unloaded cylinders. We may incorporate needle valves on the
existing tooling, and will address this issue on production magnet
collaring.

**F. Final Keyed Pressures**

These are all the final pressures after keying the body of magnet HGQ01.
The strain gauges nearer the lead end are designated \"lead end\" and
the strain gauges nearer the return end are designated \"return end\",
even though the gauges are within the magnet body, and not actually at
the lead or return end.

The inner beam and capacitor gauges are place at opposing poles. In
theory, (and disregarding friction), opposing gauges should read close
to the same preload.

Opposing gauge pairs are:

Inner beam 016 opposes inner capacitor 024.

Inner beam 020 opposes inner capacitor 022.

Inner beam 009 opposes inner capacitor 023.

Inner beam 010 opposes inner capacitor 021.

There are no outer coil capacitor gauges.

The \"lead end\" inner gauges are not at the same place longitudinally
as the \"lead end\" outer gauges, nor are the \"return end\" ones. There
is no position in the magnet at which we have both inner and outer
gauges being read simultaneously.

Maximum stress

before \"springback\" Final stress after

(Main pump pressure \"springback\". All

6500 psi, key press pressure has

pusher pressure been removed. Keys

3000 pump psi.) alone support coils.

Gauge position MPa psi MPa psi

and number

Inner Beam LE 016 132 19202 95 13750

Inner Beam LE 020 138 19979 101 14666

Inner Cap LE 024 90 13042 65 9377

Inner Cap LE 022 108 15661 78 11287

Inner Beam RE 009 93 13425 59 8574

Inner Beam RE 010 102 14810 70 10109

Inner Cap RE 023 94 13588 66 9544

Inner Cap RE 021 97 14022 65 9478

Outer Beam LE 018 107 15591 68 9799

Outer Beam LE 019 116 16894 73 10597

Outer Beam RE 014 102 14780 63 9148

Outer Beam RE 015 140 20367 9 14395

By the way, during our pre-pressing to verify the preload, we noticed
the widely discrepant readings on outer return end beam gauges 014 and
015. They are at the same place longitudinally, at positions 180 degrees
from each other. We removed them and reversed their position, them
re-pressed. The high gauge then read low, while the low gauge then read
high although the discrepancy was not as large as before. This indicates
that there really is a difference between preloads at that position,
although possibly not as large as the strain gauges indicate. From a
visual inspection, we could not see anything abnormal in that area.

We then put the gauges back in their original positions before keying
the magnet.

**G. Turn-to-turn Shorts**

The completion of magnet HGQ01 was significantly delayed due to the
discovery and repair of two turn-to-turn shorts. A chronological account
of the discovery and repair of the shorts follows:

The magnet body was keyed on 10-21. The return end was keyed on 10-24.
The collaring mandrel was removed from the bore the following day.

After the mandrel was removed, electrical measurements were done
(Resistance. inductance and \"Q\", and hipotting). All measurements were
normal.

Four days later (10-29), the pole splices were soldered. Electrical
measurements after this operation indicated that there was a short in
quadrant 1 inner coil two turns from the pole near the return end.
Voltage tap measurements isolated the short to an area about 10 cm long
which encompassed a voltage tap. The short was very resistive (it
lowered the coil resistance by about 1/6 of a turn). The short occurred,
apparently, not during an assembly operation, but while the magnet was
sitting on the assembly table. It is unlikely to have occurred during
the splicing operation.

Without repairing the short, we then installed the lead end collet. The
collet was installed dry, (without green putty) on 11-3. During the
collet installation, another short occurred, in the quadrant 3 inner
coil at the lead end. This one reduced the coil resistance by an entire
turn. Voltage tap measurements isolated the short to an area about 10cm
long on the lead end between the first and second turns from the parting
plane. This area also encompassed a voltage tap. We decided to attempt
to repair the shorts, but simultaneously wound two replacement coils in
case we failed.

Five attempts were made to repair this short, first removing the voltage
tap and solder, then inserting various combinations of kapton and G-10
between the turns in the vicinity of the voltage tap. Some of these
attempts showed damage to the inserted material (pin-holes) at the
position of the tap, leading us to conclude that the short was at the
voltage tap. Also, each insertion of progressively more material caused
the short to occur at a later stage of the collet installation, further
confirming that the short was at this position. Finally, after the 5th
attempt at repair, (and having placed .020 inches of G-10 between the
turns in this area), the short in quadrant 3 still existed.

The magnet was then rung. During ringing, the resistive short in
quadrant 1 disappeared (presumably \"burned out\").

We then did further electrical measurements on quadrant 3, at a higher
current, while reading the voltage and current separately. These
measurements were more accurate, but more risky, being done by
\"poking\" the turns with a sharp pointer to break through the
insulation. These measurements showed the short to be, still at the lead
end between the same two turns, but near the end of the saddle. The
original measurements had isolated the short to be over an area which
encompassed both the voltage tap and the area the short now appeared to
be. We then inserted .008 inches of G-10 between the turns at this point
and reinstalled the collet. The quadrant 3 short was now gone. It is
unclear whether we had one short in quadrant 3 at the voltage tap, them
created another one while fixing the original, or originally had two
shorts in the quadrant 3 coil, both of which were eventually repaired.

Two steps are being taken to decrease the possibility of turn-to-turn
shorts in future magnets (including HGQ02). The voltage tap procedure is
being modified, as explained above in (II,D,2). In addition, fixtures
have been designed to press the end of each coil before assembly to the
pressures incurred during the keying operation. Any shorts in the ends
will presumably be found before assembly. This is already being done in
the straight section, but not on the ends.

It should be possible to adapt the end compression fixtures to allow us
to measure coil size on the ends, to determine if we need to shim the
ends differently than the body to obtain the proper preload.

**VI. End Can Installation**

**A. Shimming for preload in end.**

In the ends, shimming at the poles to adjust preload is not an option.
Since there are no poles available where there are end parts, the
preload can only be adjusted by either shimming at the parting plane, or
adding or subtracting extra kapton around the perimeter of the outer
layer. A first pass was done based on FEA analysis by Igor Novitski.
Adjustments were made based on can exterior measurements done after the
dry run.

**B. Fixture Capacity**

The force required to close the collet over the lead end was about 55000
lbs. To obtain this force, 9500 pump psi was required on the three
hydraulic cylinders installed in the press. This is 95% of the capacity
of the cylinders. It would be desirable to add three more cylinders to
the end can assembly fixture, doubling the capacity for magnet HGQ02.

**C. Multiple can installation**

Ordinarily, there are two can installation in the assembly procedure.
First a \"dry run\", during which the preload is verified by checking
can deflections and adjusted if necessary, then a final installation, in
which green putty is placed around the pole lead stabilizers and allowed
to dry. Due to the turn-to-turn shorts described above in (V,G), and the
several attempts at repair of these shorts ,there were 8 separate can
installations instead of the usual two. No problems resulted from the
multiple installation. We do not expect this to reoccur in magnet HGQ02.

**D. Turns moving into bore area**

During one of the collet installation on magnet HGQ01, the parting plane
leads moved into the bore area. The can had to be removed to adjust the
lead position and reinstalled. Tooling needs to be designed to keep this
from occurring in the future.

**E. Fixture Travel for can removal**

The end can assembly fixture is designed to be able to either install or
remove an end can. The inserts used to remove the can (an operation
necessary even in the ideal case), were too short to contact the collets
and had to be shimmed. They need to be modified for HGQ02.

**F. Collet Material**

Collet quadrants were made of two material, G-10 and Ultem 2300. We
chose to use G-10 for magnet HGQ01 because it has less thermal
contraction in the azimuthal direction than the Ultem (although the same
in the radial direction). Ultimately, if the external splice design is
used for the production magnets, G-10 will be unacceptable because of
its low radiation resistance. We have not decided whether to use G-10 or
Ultem for HGQ02. Complete parts in both materials are available.

**VII. Yoke and Skinning**

**A. Yoke Pack Assembly**

Yoke packs were assembled and welded together in IB2. Five fusion welds
were used on the outside diameter and two on the inside diameter using a
stacking pressure of 150 psi. After welding the yoke packs were weighed
and measured yielding a 98% packing factor.

**B. Practice Welding**

A practice skin and yoke assembly were welded to shake down the skin
welding press. A number of problems were discovered with the biggest one
being the buckling of laminations. The following changes were made as a
result of the practice welding:

\- Monolithic yoke end packs added to both ends of HGQ01

\- Lead end yoke lam stamped with cooling hole removed (HGQ01-02 only)

\- Two 15\" stainless steel rods added the lead end yoke assembly
cooling holes at the mid-plane (HGQ01-02 only)

\- Filler packs added to the magnet assembly during welding.

**C. Alignment keys**

The collar/yoke alignment keys were reduced in height by 1mm to
eliminate any possibility of interference during the installation of the
collared coil assembly into the yoke packs.

**D. Monolithic Packs**

The epoxied stainless steel yoke end packs were not square. At the
mid-plane a gap of 0.1875" was measured on one side with no gap on the
other side. The ends of the magnet skins were supported with 2" glued
filler packs.

**E. Welding Problems**

The cold mass was compressed by the tooling using 600 psi hydraulic
pressure. A minimum of 500 psi is needed to overcome the die springs and
seat the contact tooling to the press bed. Shell welding began Friday,
December 12 and was completed the following day. During the fusion or
root pass, high porosity was observed. It is believed the cause is from
trapped air between the key and skin. Air is heated and escapes through
the weld puddle leaving behind the observed porosity. The porosity is
filled by the subsequent weld passes. Also, during the root pass, the
welder had difficulty arcing to the bottom of the "V" groove weld prep.
It is believed this is due to the torch head being closer to the walls
than to the bottom of the groove.

**F. Buckling**

The skin was cut to length and some minor buckling was observed on the
return end of the magnet. There was up to a .007 in gap between the
collar and yoke except for one point near a collar key, where contact
was made. Several laminations were peeled off the lead and return end
epoxied yoke packs because of the unevenness of the ends and the need
for instrumentation wire clearance.

**G. Out of Roundness**

Out of roundness of the magnet ends was small with the return end being
slightly worse than the lead end. The end plates were machined 0.030"
smaller on the diameter that corresponded to a large fraction of the out
of roundness measured from the practice skin and yoke assembly. As a
result, the end plates were slightly smaller than necessary.

**H. End Plate Welding**

Welding of the end plates was strait forward and uneventful. The last
layer of weld was omitted as this model is not a pressure vessel and
because the weld stress was well below yield (from calculation).

**VIII. Bullet Installation**

**A. Wiring Needed**

The wiring for the bullets needs to be fed through holes in the magnet
iron and along the surface of the end plate. This operation was not
included in the traveler and needs to be added. In addition some
grooving of the return end plate is required which need to be done in
advance for HGQ02.

**B. Preloading**

Special lower than normal preload was used on the bullets for HGQ01.
Because of the previous turn-to-turn shorts, it was considered advisable
to not torque the bullets more than absolutely necessary. The final
bullet preload in the warm condition was 350 lbs. This force allowed the
bullets to move approximately .010 inches.

**IX. Quadrant Splices**

**A. Mockup results**

A full size mockup of the quadrant splice configuration was completed.
Some parts needed to be modified to allow the leads to fit properly and
to reduce the bending radius of the cable. Modifications were made by
Lee Simmons. Drawings have been modified for magnet HGQ02. Some parts
will be reworked.

**B. Stabilizer Problems**

Copper \"lead stabilizers\" were designed to be soldered to the parting
plane leads of all coils within the area of the end plate. This is an
area about 5cm long which extends from the back of the saddle
longitudinally to the beginning of the quadrant splice blocks. These
copper pieces were to be soldered to the leads after the magnet was
yoked, but before the end plates were installed.

I turned out to be very difficult and risky to solder these pieces onto
the cable at this stage of assembly. There was not enough room to attach
a soldering fixture and not enough space to attach the proper cooling
blocks to ensure that the magnet components and end parts would not be
heated excessively. On magnet HGQ01, we merely tinned the cable in this
area. Then, after the end plates were welded, G-10 blocks and green
putty were packed around them to prevent movement.

On magnet HGQ02, These parts will be soldered onto the coils before
magnet assembly. The parting plane lead will be tinned before curing,
then the stabilizer will be soldered onto the cable immediately after
removal from the curing press. This will also prevent the parting plane
leads from deteriorating during the handling process, a problem evident
on HGQ01.

**C. Turns moving into bore**

When the quadrant splice leads were tinned, as discussed above, two of
them moved into the bore area by as much as 4mm. This was more than can
be allowed if the MTF probe is to be inserted. The two leads were
unsecured and clamped in place, then resecured and puttied. This is not
expected to be a problem on HGQ02, because the leads will be tinned
immediately before

the coil is cured. The copper stabilizer will be attached immediately
after curing. Nevertheless, a fixture will be manufactured to keep the
leads from encroaching into the bore during the final assembly process.

**D. Assembly of Quadrant Splice Parts on magnet.**

Quadrant lead parts were assembled and quadrant leads compressed into
the available spaces on HGQ01 without incident. Modifications made to
parts based on the mockup (discussed in IX, A) allowed the stresses in
the cable to be adequately small.

**E. Oversize Preforms**

Preforms were oversize and would not fit into the splice fixture. The
width of the splice fixture needed to be made .040 larger to allow the
cable to be inserted.

**F. Cold Block**

A \"cold block\" was designed to be placed between the splice fixture
and the quadrant splice parts to keep heat from dissipating into the
magnet. It did not fit into the space provided. Instead, the cold block
which is used for the pole splice was used. In addition, the spliced
area had to be moved 6mm farther away from the quadrant splice parts to
make room for the cold block. New, longer splice support blocks had to
be manufactured to confine the spliced area, including the area covered
by the cold block.

**G. Quantity of Solder**

First attempt at a splice did not have enough solder (there were
unacceptably large voids) A .010 inch thick solder strip was initially
put only in the middle, between the two preformed areas to be spliced.
When solder strips were placed on all three sides, (.010 on each side),
solder fill was adequate. The traveler needs to be changed to account
for the added solder.

**H. Flux transferred into cable toward magnet**

After fitting quadrant leads into the configuration to be spliced on the
mockup (noted above in (IX, A), splices were made in three places. It
was evident from disassembling the mockup that flux had flowed toward
the magnet from the splice. To prevent this on the magnet, splices were
made with the spliced area pointing downward, and much less flux was
used. Disassembly of HGQ01 will show whether this has occurred on the
magnet.

**J. Splice Support Blocks**

\"Splice support blocks\" were used to confine the spliced leads at the
parting plane from movement (discussed in IX,F), They were glued to end
plate. Holes need to be added to firmly screw them to the end plate on
future magnets.

**X. Final Electrical connections**

Final electrical connections were done by a combination of MTF and IB3
technicians (Marty Whitson, Bill Mumpers and Jeff Arthur). Schematic for
connectors were supplied by Jeff

Arthur. The schematic used for HGQ01 was in the form of a sketch. It
needs to be properly documented for HGQ02. Otherwise electrical
connections for magnet HGQ02 will be identical to those for magnet
HGQ01.

**A. Voltage Taps Added**

Each quadrant and ramp splices needed a third voltage tap. Only two had
been installed at each location. One extra tap was added at each place.
This step needs to be added to the traveler in the proper location.

**B. Space between End Plate and Yoke Laminations.**

The space allotted between the inside of the steel end plate and the
yoke laminations was inadequate to route the wires safely. The space
needs to be increased to 9mm on magnet HGQ02. A Hipotting failure during
the final electrical inspection was the result of a voltage tap wire
contacting the end plate. It was a result of the inadequate space and a
sharp edge on a hole in the end plate (noted in (X,C).

**C. Sharp edges on end plate Holes.**

Wires need to be routed behind the end plate and out through holes in
the end plate. These holes had sharp (non-chamfered) edges. A voltage
tap wire was damaged as it crossed this sharp edge, causing a hipot
failure at the final electrical inspection. These holes need to have
rounded or chamfered edges on future magnets.

**E. Kapton sheets for insulation.**

Kapton sheets (.005 inches) need to be added to the inside surface of
the end plate and the outside surface of the yoke laminations to prevent
ground shorts between components and instrumentation wires channeled
through that area.

**D. Strain gauge wire length**

Strain gauge wires needed to be lengthened at the ends of the magnet.
These changes need to be incorporated into the traveler. All return end
wires should be 20 feet long and lead end wires should be 15 feet.

**F. G-10 tube through Bus Slot.**

Return end instrumentation wires are routed back to the lead end through
a G-10 tube in the bus hole in the yoke. The original plan did not call
for using a G-10 tube for protection. The part needs to be added to the
magnet assembly drawing and traveler.

In addition, the voltage tap wires need to be twisted into pairs inside
the tube. This was not done on HGQ01, but should be incorporated into
HGQ02.

**G. Running Capacitor gauge wires through G-10 tube.**

The wire bundle for capacitor gauges had a large connector attached to
it at an earlier phase of assembly. It consequently could not be routed
through the G-10 tube noted in (X,F). It was instead routed through the
bus slot in the yoke, but outside the G-10 tube. This will be corrected
in HGQ02. The connector will not be attached until after the wire bundle
is routed.

**XI. Misc.**

**A. Hi Potting**

Magnet HGQ01 was hipotted coil to ground, heater to ground and heater to
coil at 1500 volts instead of the standard 5000 volts for coil to ground
and 3000 volts for heater to ground and heater to coil. It was not
deemed necessary for the cold tests to Hipot to a higher voltage. The
magnet will be hipotted to 5000 V after testing. The same procedure will
be used for HGQ02.

**B. Quality Control and Measurement Techniques Used**

Many measurement techniques are used to establish magnet quality and
reliability and to allow us to understand the relationship between these
parameters and magnet performance. They include:

• Coil press pressure measurements

• Coil press temperature measurements

• Coil azimuthal size and modulus measurements

• Coil radial size measurements

• Coil resistance measurements under load

• Coil longitudinal and springback measurements

• Electrical resistance, inductance, and \"Q\" measurements

• Voltage taps placed in coils.

• Collared coil diameter mechanical measurements

• End can perimeter measurements

• Strain gage preload measurements, both beam and capacitor gauges

• Bore Gauge measurements

• Ringing

• End preload measurements

• Hipotting

• Yoke twist measurement

• Yoke packing factor

• Warm and cold magnetic measurements

Not all of these measurements have been complete for magnet HGQ01, but
eventually all of them will be used in the model program.