TQC Progress R. Bossert

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TQC Progress R. Bossert
US LHC Accelerator Research Program
bnl - fnal- lbnl - slac
LARP Collaboration Meeting April 26-28, 2006
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Introduction
The TQC structure is an extrapolation of
successful work done on previous magnets. Many
cos theta magnets with the collar/yoke/skin
structure have been made at Fermilab and
elsewhere.
Tevatron dipole and quadrupole, SSC dipole,
Tevatron LBQ, MQXB (LHCIR Quadrupole) all have
been produced at Fermilab using a similar
structure.
TQC01 is the first of the TQC short model series
to be built. Coil manufacturing is complete.
Mechanical model work has been taking place over
the last 6 months and is being completed this
week. Assembly is beginning this week.
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TQC01 Objectives

• Design, fabricate and test a 1m long, 2 layer,
  90mm Nb3Sn quadrupole model using mechanical
  support structure based on 25mm thick SS collars.
  Compare magnet performance with the design
  parameters.
• Provide input for a consistent comparison
  between the properties of a collar-based
  structure and an aluminum shell-based structure
  (TQS model).
• Use the same coil design for both TQS and TQC
  models.

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TQ coils
TQC coils are identical to the coils used for TQS
models assembled at LBNL.

• Coil
• 2-layer shell-type
• Inner-layer wedges
• Inner-layer pole glued into the coil
• Cable
• Strand MJR, 0.7 mm
• Number of strands 27
• Keystone angle 1 deg
• Width 10.077 mm
• Thickness 1.26 mm
• Insulation 0.125 mm S2-glass sleeve

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TQC parameters
TQC01 Specifications
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TQC Structure - Design Approach
The TQC design is based on the MQXB mechanical
structure (collar, yoke, skin, end plate,etc.).
This basic structural system was used at Fermilab
on the Tevatron magnets. Variations have been
used successfully on the Tevatron LBQ, the SSC
dipole, and most recently the MQXB (LHC IR quad).

The collar/yoke/skin structure has proven to be
reliable and reproducible for short as well as
full-length magnets.
MQXB cross-section.
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TQC mechanical structure

• Based on structural analysis, specific features
  of the LHCIR quadrupole have been modified, and
  features have been added to allow this system to
  meet the requirements of the higher field Nb3Sn
  magnets.
• Shims are added between collar and yoke at each
  midplane to allow preload to be shared between
  skin and collars and control collar-yoke
  interference.
• Outer layer poles have been retained for coil
  alignment. Inner poles are impregnated into
  coil.

TQC cross-section.
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TQC Mechanical Structure

• A radial cut is made in each yoke quadrant to
  provide symmetrical loading to the collars.
• Control spacers are introduced for collared coil
  alignment and yoke motion control.
• 12 mm thick stainless steel skin, increased from
  8mm used for MQXB.
• Mechanical structure and coil pre-stress is
  studied and optimized using a series of
  mechanical models.

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TQC mechanical structure End Loading
3D FEA of structures has taken place at both LBNL
and FNAL. Analysis indicates that, depending on
input parameters and end loading, separation
between end parts and first turn of coils of
between 20um and 200 um can take place when the
magnet is powered.
Effect of this separation on training behavior is
not clear. There is evidence from racetracks at
LBNL that a correlation exists between gaps and
training. Many magnets built and tested at
Fermilab, both Nb3Sn and NbTi, with minimal and
no end loading, have not exhibited excessive
training quenches in the ends.
End load in TQC01 will test the minimal axial
end loading system. Load is applied by a
combination of radial force through the collars
by the skin, and end force applied by four
preload screws, or bullets through 50mm thick
stainless steel end plates. A total force of
14000N (3000 lbs.) is applied to each end.
This system is identical to that which has been
proven effective on Nb3Sn dipoles at Fermilab.
It is designed to ensure that the magnet ends are
in contact with the bullets during all phases of
cool-down and operation. HFDA06, a recent dipole
model, was tested with this system and remained
preloaded during all phases of operation. The TQ
structure is similar to that of Nb3Sn dipoles.
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TQC 2D Mechanical Analysis
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TQC Assembly Insulation and Collaring

• Impregnated coils are assembled and surrounded by
  layers of Kapton ground wrap.
• Assembly is hung vertically over collaring press,
  and collar packs are placed over coils.

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TQC Assembly Collaring
Collars are incrementally keyed, in 8 cm.
longitudinal sections, applying azimuthal preload
to the coils of 70MPa after keying is complete.
Initial pressure is applied by main cylinders,
then key cylinders are energized. Multiple
passes are applied, with key depth controlled and
incrementally increased with each pass.
Mechanical model studies indicate that
differential pressure between keyed sections can
be controlled to within 15 MPa.
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TQC Assembly Yoke and Skin

• Control spacers, preload shims, yoke packs and
  skin are assembled in the yoke press.
• Hydraulic pressure is applied and skin is welded
  in several passes, applying the fully assembled
  preload of 140MPa to the coil through the preload
  shims.
• Preload to coils from yoke/skin is limited by the
  control spacers at room temperature.
• During cooldown, parts shrink, allowing preload
  on coils, still limited by the control spacers,
  to increase to 150MPa.

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TQC Assembly Ends and Splices
End plates are welded, and torque is applied to
end preload bolts.
NbTi midplane leads are formed into appropriate
shapes, and leads are spliced.
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TQC01 Status - Coils
4 coils were wound and cured at Fermilab, reacted
and impregnated at LBNL. Now ready to assemble
at Fermilab.
Spot heater
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TQC01 Status Mechanical Models
Several mechanical models have been produced.
Purpose of the Mechanical models

• Understand coil size, midplane shims and collar
  yoke shims.
• Compare coil preloads with anaylsis.
• Understand how collaring process works with
  Nb3Sn coils.
• Understand and verify yoke welding process.

Mechanical Model 1 - A preliminary model using
an aluminum tube with collar structure was used
to confirm analysis of collared coil assembly.
Strain in the aluminum tube was measured while
the collaring keys were inserted, incrementally,
in small steps until they were fully inserted.
Azimuthal stress in the aluminum tube increased
by approximately 15 MPa per mm of key depth.
Since key depth can be controlled during the
keying operation to about 1mm, the incremental
stress between keyed sections can be controlled
to within 15 MPa.
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TQC01 Status Mechanical Models
Mechanical Model 2 Used practice coils 1 and 3
End areas were collared with full round
collars. Purpose was to understand collaring
process over ends using full round collars as
well as understand yoke welding process with TQ
coils. Some straight section was also collared
with full round collars.

• Results
• Collaring with 125 micron (5 mil) midplane
  shims yielded preloads within the acceptable
  range.
• Yoke welding alignment gap and weld pass
  numbers were established which provide necessary
  movement for yoke to close onto control spacers,
  therefore providing the 140 MPa to coils
  necessary for completed magnet .

Mechanical Model 2
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TQC01 Status Mechanical Models
Mechanical Model 3 Used practice coils 1 and 3
intended to understand collaring process over
straight section with tabbed collars and
differences between inner and outer preload.
Capacitor gauges placed at all inner and outer
midplanes. Collar deflections and gauge
readings after keying showed large differences in
size and preload between quadrants, indicating
side-to-side variations between coils.
Q1
L
S
S
L
Q4
Q2
L
S
S
L
Q3
TQC01 Mechanical Model Configuration
Normal TQ configuration
As a result, a full round configuration was
chosen for TQC01, until precision and placement
of components within the coil cross section is
completely understood.
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TQC01 Status Coil Measurements
Due to the results shown in mechanical model 3,
measurements of the coil cross section were taken
on an optical comparator. Two sections of
practice coil 4 have so far been measured.
Preliminary results indicate that coils have no
significant side-to-side variations. More
sections still need to be measured to understand
coil consistency.
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TQC01 Status Coil Measurements
Also, practice coils 2 and 4 were pressed in a
fixture at azimuthal preloads up to 60 MPa with
Fuji film placed at the midplanes. Results show
very uniform preload across both layers,
indicating there are no significant differences
between size of inner and outer layers.
Conclusion differences in size of inner and
outer layers on optical comparator measurements
are due to the coil being relaxed slightly when
sectioned in the free state.
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TQC01 Status Mechanical Models
Mechanical Model 4 Practice coils 1 and 3 were
re-collared using full round collars and
capacitor gauges on both inner and outer coils.
Results showed that large variations in collar
deflections were eliminated, as expected, but
capacitor gauges indicate large preload
variations between outer coil quadrants.
Conclusion Either practice coil 1 or 3 has an
anomalous size at some cross section or the coils
have been damaged from extensive handling and
use.
As a result, MM4 is not being used to determine
mid-plane shims, but can still be used to verify
weld processes and collar-yoke shim size. This
model is ready to be welded. Welding will be
completed on May 1st.
Mechanical Model 5 Practice coils 2 and 4 have
been collared with full round collars, using a
range of shims from 0 to 125 microns, and Fuji
film at the midplanes. Purpose is to determine
preload shims. This model has been completed.
Based on this data, preload shims of 50 um will
be placed at each midplane when coils are
assembled.
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TQC01 Instrumentation

• Voltage taps applied to coils through traces, as
  in TQS design. Outer coil positions identical
  to TQS. Inner coil positions identical to the
  TQS positions, with 2 taps added.
• 1 strain gauge on inner surface of each pole, on
  lead end key/island, measuring longitudinal
  stress, identical to gauge position on TQS01.
• Strip heaters embedded into outer coil traces
  (identical to TQS01).

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TQC01 Instrumentation

• 4 strain gauges bonded to inner surface of each
  inner coil to measure inner coil preload.

• Spot heaters on outer layer of two coils.

• Strain gauges on control spacers.

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TQC01 Instrumentation

• Strain gauges on skin.

• Strain gauges on end preload screws (bullets).

• 2 temperature sensors, one near each end in yoke.

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TQC01 Schedule
Construction of TQC01 is beginning this week.
FY05 Design of cable, coil, and tooling
FNALLBNL 01/15/2005 Complete Fabricate and
insulate practice cable LBNL 04/15/2005
Complete Procure coil fabrication tooling/parts
FNAL 05/01/2005 Complete Procure mech
model parts FNAL 07/15/2005
Complete Wind Cure 2 practice coils
FNALLBNL 08/01/2005 Complete React
impregnate 2 practice coils FNAL 09/15/2005
Complete FY06 Wind/cure coils
FNAL 12/20/2005 Complete React/impregnate
coils FNAL 04/15/2006 Complete Assemble and
test mechanical model FNAL
05/1/2006 Assemble magnet FNAL 06/16/2006 Te
st magnet FNAL 07/07/2006
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TQC02

• Objectives are
• To fabricate and test a 2nd 1-m long, 2-layer,
  90-mm Nb3Sn quadrupole model using the
  collar/yoke mechanical structure. Compare magnet
  performance with the design parameters and the
  performance of TQC01 and increase the statistical
  database for TQ short models.
• Provide input for a consistent comparison
  between the properties of a collar-based
  structure and an Aluminum shell-based structure
  (TQS models).
• Refine design features based on construction
  experience and/or testing of TQC01.
• Incorporate RRP strand in TQ coils and structure.

6 unit lengths of TQC02 cable has been
fabricated, but there are some questions
concerning stability. Coil fabrication will
begin as soon as new cable will be manufactured.
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Summary

• Coils for TQC01 are complete. They are at
  Fermilab ready to be assembled.

• Mechanical model work on collared coils for
  TQC01 is complete. Yoke and skin welding of the
  final mechanical model will be completed Monday
  May 1st.

• Construction of TQC01 has begun. Coils are
  being instrumented this week. Assembly will
  begin May 1st

• Coil winding of TQC02 has not started, but will
  begin as soon as new cable is available.