Transcript StepIV: Status of the magnetic field efforts

K. Long,
7 August, 2016
Mitigation of stray magnetic field
The Magnetic Shielding Group:
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Victoria Bayliss
John Cobb
Luke Fry
Melissa George
Pierrick Hanlet
Ken Long
Craig Macwaters
Courthold Mike
Ian Mullacrane
Roy Preece
Paul Smith
Jason Tarrant
John Webb
Holger Witter
Apologies if
I have omitted
you!
Contents:
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History
Magnetic modeling
Compressor re-location
Rack and control-room layout
Partial return yoke
Preparation for validation of FEA
Schedule considerations
Conclusions
Mitigation of stray magnetic field
History
V. Bayliss; CM33
Step IV: Compressors
5
4
Step VI: Compressors
600
500
|B| f i el d
(Gau ss)
400
-10000
Step IV: Magnet Control
Racks
Simplified solution shows it is
possible to shield in 5mm
US1010 iron and 5mm mumetal if Aluminium racks are
used.
In reality, we will need to provide
protected access (labyrinth or
air-lock style) to allow access
during magnet operation.
This implies serious modifications to the positions of magnet control
racks, their services and the entrance to the trench.
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300
200
100
0
-5000
0
5000
10000
Z -l ocat i on al on g b eam l i n e
(m m )
15000
Step IV: Electrical Racks
on North Mezzanine
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4 racks located on the north
mezzanine
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5mm US1010 iron and 5mm
mu-metal if Aluminium racks
are used.
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Estimated weight 3-5 tonnes –
requires major modifications
to the north mezzanine
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Mitigation of stray magnetic field
Magnetic modeling
P. Smith
Magnetic modeling:
• Hall Model
– The current MICE Hall Model is ~complete:
• Model now being used to gain information about the fields in
the racks and compressors under various assumptions
– Issue mainly mass distribution within the racks
• The racks/compressors contain some fairly fine detail:
– So, given the size of the Hall (and the model) there is a compromise
wrt the achieved meshing resolution
– It is clear that the results that the model is producing
needs checking with reality.
• R9 model:
– Vicky Bayliss has built model of the setup in R9
– Will be tested with real field measurements
– Results of the R9 “bench-test” will inform development
of the MICE Hall model
P. Smith
Magnetic modeling:
• Details of all the MICE Hall models and the scripts that built them
are kept on a website:
– http://www.hep.shef.ac.uk/research/mice/opera_models/test_model
s.html
• Model being extended to include all the ‘South Side Buildings’:
– MLCR; Plant room; Rack room 2; Hydrogen room; and ISIS control
rooms.
P. Smith
Magnetic modeling:
• Sub-models:
– It has been demonstrated (Mike Courthold) that it
is possible to extract the field in a sub-volume from
the Hall model so that it can be used to define the
boundary conditions of a “sub-model”;
– Important as it allows for modelling of sensitive
regions in more detail
• Sub-models will allow the parallisation of the
modelling:
– New staff recruited into modelling effort from
Imperial (M. George) and DL (K. Marinov)
• First meeting to get this sub modelling started
has been arranged to be held at Daresbury on
the 31st January.
Model comparison:
P. Smith. H. Witte, C. MacWaters
40G in case front
80G in case sides
120G in case sides
• Investigation (HW) of field
in neighbourhood of racks
indicated lower field inside
metal cabinets than previously
feared;
• Comparison with OPERA model
(HW, PS, CMacW) seems to
confirm this observation
• Interesting!
1.5G internal
– Might indicate stray fields can be managed
• Essential:
– Verification of magnetic models, e.g. using focus-coil and set-up in R9
Mitigation of stray magnetic field
Compressor relocation
J. Tarrant
West Wall: requirements:
• Compressors located to meet <= 30m high-pressure hose lengths
• Build necessary structure to support compressors & services
• Additional requirements
• Personnel access
• Compressor access (for installation & swap)
• Equipment delivery & assembly space (especially MICE devices)
15 Cryomech
compressors
4 Sumitomo
compressors
Step IV
compressors
• Document in
preparation for
transmission to
Technical Board
• Strong pressure
now to move
from design to
execution
Step V & VI
compressors
J. Tarrant
Equipment delivery and assembly area:
J. Tarrant
Mitigation of stray magnetic field
Rack and control room layout
J. Tarrant
MLCR & Rack Room #2
Toilets will be
removed for new ISIS
switchgear (2014)
New access
doors
ISIS
switchgear
Existing
locker room
= Rack
Room #2
Cables routed
under stairs
with access via
Rack Room #2
(volume to be
fireproofed)
Cables routed
under false floor
then into Hall (not
an insignificant
task!)
ISIS Plant room
door move
(position TBD)
Extended
MLCR
Existing rack
room = Rack
Room #1
2D Layout from John Webb
Mitigation of stray magnetic field
Partial return yoke
Modular shielding
• Need for shielding:
– Large stray field in MICE hall
– MICE Hall: equipment which
is sensitive to field
• UK/US magnetic Shielding
Group
– Two approaches: individual
shielding of components and
magnetic shield
• BNL: Magnetic Shield
Courtesy of Steve Plate, BNL
7 August 2016
– Design and simulation effort
– Shield:
40 tons of iron, 8.5m long
– Mechanical design (Magnet
Division)
H. Witte
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Concept
• For perfect shielding:
encase MICE in softiron cylinder
1.5 m
• However: acceptable
shielding can be
obtained with “partial
return yoke”
• Geometry
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Tube of radius 1.2 m
wall thickness 10 cm
azimuthally -50..50°
weight: 30t
7 August 2016
2m
– Not practical
(Note: not to scale)
H. Witte
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Achievable Performance
• Flux leakage
contained closely to
MICE
– Very little field
leakage behind
shield
Field lower by
factor 40+
10G
5G
7 August 2016
2G
• Field smaller than 5
Gauss for large
fraction of MICE
hall
• Tracker electronics
in low field region
• First pass on
engineering design
H. Witte
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Progress
• General Concept and Performance
– All cases of MICE
• Shield Penetrations
– Required for tracker waveguides etc.
– Solution identified – no impact on
performance
• Engineering
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2920mm
[115 in]
7 August 2016
Section of
shield
made of
AISI 1010
steel
Integration with MICE hall feasible
Forces on shield evaluated
Floor loadings / support structure
Preliminary cost-efficient engineering
concept: shield made of 14 sections
– Issue of specifications and tolerances
beginning to be addressed
• Extension to Step VI
– Demonstrated: general proof-ofconcept simulation
– More detail work necessary (focus is
on Step IV)
H. Witte
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Mitigation of stray magnetic field
Preparation for validation of FEA
Aims of modelling in R9
• General validation of model
• What fields are the compressors operating in?
• What is the most accurate way to model
compressors?
• What effect does the partition wall have on
the field?
V. Bayliss, C. MacWaters
General Validation
2mm “mildaverage” steel
• Baseline compressors modelled
• Compare the field maps at an array of
points in R9 (49 points)
135kg
This model has been built.
V. Bayliss, C. MacWaters
What field are the compressors
operating in?
The modelling done so far predicts that the field
around the compressors is ~5 Gauss, and that
develops a field in the skin that is ~200 Gauss.
However, the Cryogenics group have experience
of have operating compressors in similar fields
in R9 previously.
We need to measure the real field to see if the
compressor skin is shielding the motor or if it is
just operating ok in that field.
V. Bayliss, C. MacWaters
What is the most accurate way to
model compressors and racks?
• Model compressor in variety of ways:
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Single lump mass
Skin with simple mass in centre
Evenly distributed mass
9 lump masses (8 corners and the centre)
Etc.
• Measure field in and around
compressors and control racks
• Compare which model most accurately
predicts fields
This is future work.
V. Bayliss, C. MacWaters
What effect does the partition wall
have on the field?
• The partition wall has been modelled in a
similar way to those in the MICE hall
• Measuring the field in and around the wall will
give us more confidence in our modelling
techniques.
Mitigation of stray magnetic field
Schedule considerations
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MICE to Step IV:
Schedule shows “Step IV installation complete” Jun13:
– Taking this as a constraint
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Installation of solenoids etc. starts Sep13 to meet the Jun14 deadline:
– Already under pressure to deliver stray-field mitigation solution in time
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Pressure will continue to grow (welcome!)
Stray field mitigation for Step IV:
– Baseline:
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Compressors at West Wall
Rack Room 2; appropriate local shielding
– Mitigation of risk that there is a “gottcha”
in the baseline:
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Partial return yoke
Field mitigation schedule:
– “Racks behind north magnetic shield wall”:
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Ready to go, now prefer Rack Room 2
solution
– Compressors at West Wall:
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Detailing underway
Paper to TB before CM35
Expedite move to implementation
as far as possible
– MLCR upgrade and Rack Room 2:
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Expedite completion of specification
and design
Move to implementation as soon as possible
Strengthening the team:
– Modeling: M. George (Imperial), K. Marinov (DL)
– Design: G. Barber (Imperial), L. Fry (RAL)
Mitigation of stray magnetic field
Conclusions
Conclusions:
• Huge amount accomplished since June 2012!
– An effective team effort
• Aspects that are becoming clear:
– Compressor management
– Rack management
• Issues to be dealt with:
– Verification of OPERA models with measurements
– Efficient development of sub-modeling so that the
items on the “Fry list” can be dealt with
• My gut feeling:
– The stray-field problem can be addressed
respecting the timetable for the implementation of
Step IV