L Bottura, M Buzio , JG Perez, A Masi, N Smirnov, A Tikhov, et al., “A Polarity Checker for LHC Magnets” IMMW 2005, 14th International Magnetic Measurement Workshop, CERN, 26-29 September 2005 (1/18) A Polarity Checker for LHC Magnets A Polarity Checker for LHC Magnets L. Bottura, G. Brun, M. Buzio , G. Fievez, P. Galbraith, J. Garcia Perez, R. Lopez, A. Masi, S. Russenschuck, N. Smirnov, F. Thierry, A. Tikhov 1. 1. Introduction Introduction 2. 2. Measurement method Measurement method 3. 3. Hardware Hardware 4. 4. Software Software 5. 5. Characterization Characterization 6. 6. Test results Test results 7. 7. Conclusions and outlook Conclusions and outlook Contents Contents Ref: M Buzio et al, “Checking the Polarity of Superconducting Multipole LHC Magnets”, paper presented at
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L Bottura, M Buzio, JG Perez, A Masi, N Smirnov, A Tikhov, et al., “A Polarity Checker for LHC Magnets” IMMW 2005, 14th International Magnetic Measurement.
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L Bottura, M Buzio, JG Perez, A Masi, N Smirnov, A Tikhov, et al., “A Polarity Checker for LHC Magnets”IMMW 2005, 14th International Magnetic Measurement Workshop, CERN, 26-29 September 2005
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A Polarity Checker for LHC MagnetsA Polarity Checker for LHC Magnets
L. Bottura, G. Brun, M. Buzio, G. Fievez, P. Galbraith, J. Garcia Perez, R. Lopez, A. Masi, S. Russenschuck, N. Smirnov, F. Thierry, A. Tikhov
1.1. IntroductionIntroduction
2.2. Measurement methodMeasurement method
3.3. HardwareHardware
4.4. SoftwareSoftware
5.5. CharacterizationCharacterization
6.6. Test resultsTest results
7.7. Conclusions and outlookConclusions and outlook
ContentsContents
Ref: M Buzio et al, “Checking the Polarity of Superconducting Multipole LHC Magnets”, paper presented at MT-19
L Bottura, M Buzio, JG Perez, A Masi, N Smirnov, A Tikhov, et al., “A Polarity Checker for LHC Magnets”IMMW 2005, 14th International Magnetic Measurement Workshop, CERN, 26-29 September 2005
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the LHC will include about 1750 cryomagnet assemblies, up to almost 16 m long, housing a total of about 10000 superconducting magnets connected in 1612 electrical circuits
magnet connection errors are always detrimental and may be unacceptable in some cases, including esp. main dipoles and quadrupoles, insertion region magnets, skew and tuning quadrupole correctors
need to check systematically multipole order, type and polarity of all LHC magnetic elements automated, self-contained probe based on a rotating Hall sensor designed and built similar system used with success at BNL for RHIC and presented at IMMW XI, Brookhaven (A. Jain et
al.)
1.1 – Introduction: 1.1 – Introduction: Purpose of the systemPurpose of the system1.1 – Introduction: 1.1 – Introduction: Purpose of the systemPurpose of the system
1232 cryodipoles, including 3696 corrector spool pieces 360 arc Short Straight Sections, divided in 61 sub-types including 260 main quadrupolesand 1080 corrector magnets
~8000 total superconducting corrector magnets106 Short Straight Sections for the insertion regions
L Bottura, M Buzio, JG Perez, A Masi, N Smirnov, A Tikhov, et al., “A Polarity Checker for LHC Magnets”IMMW 2005, 14th International Magnetic Measurement Workshop, CERN, 26-29 September 2005
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Specifications: - general-purpose system for any multipole order and type (normal or skew) - automatic, self-contained, fast- room temperature measurements, fit inside beam pipe (Ø 50 mm) - minimum field 60 T (~earth field !)
L Bottura, M Buzio, JG Perez, A Masi, N Smirnov, A Tikhov, et al., “A Polarity Checker for LHC Magnets”IMMW 2005, 14th International Magnetic Measurement Workshop, CERN, 26-29 September 2005
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Radial component (normal to Hall sensor)
Vector of N values sampled at regular intervals
DFT of the radial field vector
Inverse DFT of the radial field vector
2.1 – Measurement method: 2.1 – Measurement method: Harmonic analysis of radial fieldHarmonic analysis of radial field2.1 – Measurement method: 2.1 – Measurement method: Harmonic analysis of radial fieldHarmonic analysis of radial field
1
)1(
1
refr)iA(BB),(
n
ni
n
nnxy er
iBrΒ
1
)1(
1
refr)iA(BB),(
n
ni
n
nnxy er
iBrΒ
irR euBB B
)(
1-N to0j ,2
),( jN
BB jjRR jj
1
0
21 N
j
ijkN
R eBN j
kβ
1
0
2N
k
ijkN
R eBj
kβ
*
1
n
n
ref
R
ri
nC
*
1
n
n
ref
R
ri
nC
Tangential Hall plate
Stepwise Rotation Magnet Apertures
X
Y
Connection end
Y
X
B
BR
R
1
1
12
sin2
cosN
nnn
n
refR jn
NBjn
NA
r
RB
j
Harmonic field coefficients as a function of the DFT of sampled values
Harmonic field coefficients as a function of the DFT of sampled values
* denotes complex conjugation
expand, equate term by term
L Bottura, M Buzio, JG Perez, A Masi, N Smirnov, A Tikhov, et al., “A Polarity Checker for LHC Magnets”IMMW 2005, 14th International Magnetic Measurement Workshop, CERN, 26-29 September 2005
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2.2 – Measurement method: 2.2 – Measurement method: Transfer functionTransfer function2.2 – Measurement method: 2.2 – Measurement method: Transfer functionTransfer function
Magnets without diode installed
Magnets with diode installed
For greater accuracy, polarity is determined on the basis of (approximate) transfer function rather than raw harmonic measurement
An arbitrary number of current points can be specified; minimum is two, of opposite sign if possible
Linear best fit to {Cn,I} pairs
0,nn
n CII
CC
Cn
I
I1
I2
Cn
II1 I2Transfer function [T/A @ 17 mm]
Remanent field [T @ 17 mm](+ Hall voltage offset)
L Bottura, M Buzio, JG Perez, A Masi, N Smirnov, A Tikhov, et al., “A Polarity Checker for LHC Magnets”IMMW 2005, 14th International Magnetic Measurement Workshop, CERN, 26-29 September 2005
Parameter ValueProbe length (mm) 768Probe external diameter (mm) 40Tube internal diameter (mm) 40 to 73Tilt sensor range 45°Tilt sensor resolution (mrad) 0.1Hall plate current (mA) 50 Hall plate sensitivity (mV/T) 233.8Hall plate radius (mm) 11Hall plate azimuthal offset (mrad) 10.5Hall plate max. field (mT) 30Hall plate min. field (mT) 0.01On-board Preamplifier gain 500Azimuthal resolution (mrad) 0.047
Functional block diagram
4+1 units in operation at CERN 24x256-stage stepping motor with
22:1 reduction gearbox electrolytic tilt sensor longitudinal transport motor not in
use (manual positioning)
L Bottura, M Buzio, JG Perez, A Masi, N Smirnov, A Tikhov, et al., “A Polarity Checker for LHC Magnets”IMMW 2005, 14th International Magnetic Measurement Workshop, CERN, 26-29 September 2005
Power supplies for rack, DC motor, tilt sensor, stepping motorVoltmeter (tilt sensor)
50 mA Hall supply
Windows PC(+ DAC for Hall output acquisition)
Keithley 2001 multiplexer
DAQ electronics rack
Bipolar Kepco magnet power supply
Custom data switching unit
L Bottura, M Buzio, JG Perez, A Masi, N Smirnov, A Tikhov, et al., “A Polarity Checker for LHC Magnets”IMMW 2005, 14th International Magnetic Measurement Workshop, CERN, 26-29 September 2005
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3.3 – Hardware: 3.3 – Hardware: Connections to main cryoassembliesConnections to main cryoassemblies3.3 – Hardware: 3.3 – Hardware: Connections to main cryoassembliesConnections to main cryoassemblies
Upstream (connection)
Downstream (lyre)
M1 M2 M1 M2
M3
Power supply
DSU
1 10 20 11 1 10 20 11
L R R L
J2 J3
J4
Upstream
(connection)
M1 M2
M3
Power supply
DSU
ES811 ES812 ES911 ES912
J5
J6
J7
ES8x1 ES8x2 ES831 ES832 ES9x1 ES9x2 ES931 ES932
Downstream (lyre)
L
R
L
R
Name J1 J2 J3 J4 J5 J6 J7 J8 Type Burndy Burndy Burndy Burndy Burndy Burndy Burndy Burndy Pins 4 4 28 28 8 12 5 12 Gender Male Female Female Male Female Female Female Female Output Channels
- 1 2-9 2-9 1-2 3-6 7-8
MB SSS Used for
Power Supply MB
MCS/MCDO Upstream
MCS/MCDO Downstream
MQ Other
correctors MCBX
MUX
standardized connections to cryodipoles and arc Short Straight Sections allow fully automatic sequential powering of the magnets
connections to magnets for the Insertion Regions are done manually (106 cryoassemblies, 16 types)
cry
od
ipole
sh
ort
str
aig
ht
secti
on
L Bottura, M Buzio, JG Perez, A Masi, N Smirnov, A Tikhov, et al., “A Polarity Checker for LHC Magnets”IMMW 2005, 14th International Magnetic Measurement Workshop, CERN, 26-29 September 2005
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User panel, wizard-style interface
4.1 – Software: 4.1 – Software: LabView user interfaceLabView user interface4.1 – Software: 4.1 – Software: LabView user interfaceLabView user interface
On-line assessment of results by cross-checkingwith expected values
Automatic generation of pdf
test report
Manual input of assembly/magnets to be tested
L Bottura, M Buzio, JG Perez, A Masi, N Smirnov, A Tikhov, et al., “A Polarity Checker for LHC Magnets”IMMW 2005, 14th International Magnetic Measurement Workshop, CERN, 26-29 September 2005
L Bottura, M Buzio, JG Perez, A Masi, N Smirnov, A Tikhov, et al., “A Polarity Checker for LHC Magnets”IMMW 2005, 14th International Magnetic Measurement Workshop, CERN, 26-29 September 2005
8HCLMBBL 2 4 MB MCS MB MCSHCLMBBR 2 4 MB MCS MB MCSHCLMBAL 2 8 MCD MCO MB MCS MCD MCO MB MCSHCLMBAR 2 8 MCD MCO MB MCS MCD MCO MB MCSHCLQASA 2 4 MQS MQ MS MCBV MQS MQ MS MCBHHCLQASB 2 4 MQS MQ MS MCBV MQS MQ MS MCBHHCLQASC 2 4 MQS MQ MS MCBH MQS MQ MS MCBVHCLQASD 2 4 MQS MQ MS MCBH MQS MQ MS MCBVHCLQASE 2 4 MQS MQ MS MCBH MQS MQ MS MCBVHCLQASF 2 4 MQS MQ MS MCBH MQS MQ MS MCBVHCLQATA 2 4 MQT MQ MS MCBV MQT MQ MS MCBH
Magnet configuration file
Magnet Label (Type/ Assembly/ Aperture)
Magnet type
Insertfrom
Position[mm]
ComponentPolarity
ExpectedPositive Terminal
MB_HCLMBA_1 MB Upstream 7500 N P AMB_HCLMBA_2 MB Upstream 7500 N N AMCS_HCLMBA_1 MCS Downstream 1500 N P AMCS_HCLMBA_2 MCS Downstream 1500 N P AMO_HCLQOAG_1 MO Upstream 259 N N AMO_HCLQOAG_2 MO Upstream 259 N N AMQ_HCLQOAG_1 MQ Upstream 2283 N N AMQ_HCLQOAG_2 MQ Upstream 2283 N N A
MCBV_HCLQOAG_1 MCBV Upstream 4803 S P AMCBH_HCLQOAG_2 MCBH Upstream 4803 N P A
MS_HCLQOAG_1 MS Upstream 4117 N P AMS_HCLQOAG_2 MS Upstream 4117 N P A
Expressed in the magnetic
measurement reference frame
Expressed in the magnetic
measurement reference frame
(…) 4 types of cryodipoles, 61 + 16 types of short straight section in the arcs and insertions(…) 4 types of cryodipoles, 61 + 16 types of short straight section in the arcs and insertions
L Bottura, M Buzio, JG Perez, A Masi, N Smirnov, A Tikhov, et al., “A Polarity Checker for LHC Magnets”IMMW 2005, 14th International Magnetic Measurement Workshop, CERN, 26-29 September 2005
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The calibration of the probe concerns mainly two parameters:
Voltage-to-field transfer function of the Hall plate + preamplifier combination (~8.5 mT/V):determined by measuring the loadline of a reference dipole and cross-checking with a Metrolab NMR teslameter
Angular offset between Hall plate and tilt sensor (~10 mrad):determined as the average of the field direction obtained from two harmonic measurements in a reference dipole, inserting the probe from both ends.
Other systematic and random factors affecting the measurement that were neglected include:
- roll/pitch angle error of the Hall plate ( pick-up of tangential/longitudinal field component)- error R in the radial position R of the Hall plate ( error (n-1)R/R in the field coefficients)- planar effect - temperature drift
linearity error of the Hall sensor:<3% for all cases of interest
linearity error of the Hall sensor:<3% for all cases of interest
L Bottura, M Buzio, JG Perez, A Masi, N Smirnov, A Tikhov, et al., “A Polarity Checker for LHC Magnets”IMMW 2005, 14th International Magnetic Measurement Workshop, CERN, 26-29 September 2005
results were consistent in both casesresults were consistent in both cases
The polarity of Hall sensor output was verified with two methods:1) deformation of current-carrying wire from right-hand rule: F = I × B2) commercial 3D Hall probe teslameter (Metrolab THM7025)
N
S
B
magneticfield
force
current
+ -
L Bottura, M Buzio, JG Perez, A Masi, N Smirnov, A Tikhov, et al., “A Polarity Checker for LHC Magnets”IMMW 2005, 14th International Magnetic Measurement Workshop, CERN, 26-29 September 2005
A systematic verification procedure was carried out on magnets of order n=1 to 5 (total = 5x4x2 measurements):
1) Install magnet so that field is normal positive2) Check polarity with commercial Hall teslameter 3) Verify multipole order, magnet type and polarity with the Polarity Checker in four cases: { current, insertion from connection or non-connection end} polarity must reverse with the current (always) and with insertion side (only n=2,4)4) Turn magnet by -/n to make it skew, repeat step 3)
e.g. Normal negative quadrupole
Rotating Hall probe measurement
-2
-1.5
-1
-0.5
0
0.5
1
1.5
2
0 50 100 150 200 250 300 350 400
Angle (deg)
Radia
l Fie
ld (
mT)
results were conforming to expectations in all casesresults were conforming to expectations in all cases
expected Br()
measured Br()
L Bottura, M Buzio, JG Perez, A Masi, N Smirnov, A Tikhov, et al., “A Polarity Checker for LHC Magnets”IMMW 2005, 14th International Magnetic Measurement Workshop, CERN, 26-29 September 2005
repeatability of the main field: better than ~1% in all tested casesrepeatability of field direction: between 2 and 8 mrad
repeatability of the main field: better than ~1% in all tested casesrepeatability of field direction: between 2 and 8 mrad
The repeatability of the system was checked by running 60 consecutive measurements in the reference magnets.
affected by errors in the dynamic readout of the electrolytic tilt sensor + feed-forward control of the
stepper motor
affected by errors in the dynamic readout of the electrolytic tilt sensor + feed-forward control of the
stepper motor
L Bottura, M Buzio, JG Perez, A Masi, N Smirnov, A Tikhov, et al., “A Polarity Checker for LHC Magnets”IMMW 2005, 14th International Magnetic Measurement Workshop, CERN, 26-29 September 2005
main field accuracy: depends on repeatability + linearity error field direction accuracy: depends on repeatability + main field error time required for
- single acquisition: 0.75 s (motor must be switched off)- harmonic measurement: 90 s- full standard cryomagnet: ~1 hour
10% rejection threshold on the difference between measured and expected T.F.
10% rejection threshold on the difference between measured and expected T.F.
inadequate for field direction measurements
inadequate for field direction measurements
main field accuracy << amplitude of other harmonic componentsmain field accuracy << amplitude of other harmonic components
field direction accuracy << threshold to discriminate phase of main component (worst case=dodecapole=15°)
field direction accuracy << threshold to discriminate phase of main component (worst case=dodecapole=15°)
no errors reasonably expected for the target measurement resultsno errors reasonably expected for the target measurement results
L Bottura, M Buzio, JG Perez, A Masi, N Smirnov, A Tikhov, et al., “A Polarity Checker for LHC Magnets”IMMW 2005, 14th International Magnetic Measurement Workshop, CERN, 26-29 September 2005
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6 – Test results:6 – Test results: Summary of results of first 505 cryoassemblies Summary of results of first 505 cryoassemblies 6 – Test results:6 – Test results: Summary of results of first 505 cryoassemblies Summary of results of first 505 cryoassemblies
Magnet Type Tested Faults Type
Cryodipoles 330 3 Any - Main dipoles (MB) 330 0 - - Spool piece correctors 990 3 Polarity Short Straight Sections 175 34 Any - Main Quadrupoles (MQ) 175 0 -
1% of faults in cryodipoles, 20% in Short Straight Sectionsnon-critical errors, all easily rectified at CERN
1% of faults in cryodipoles, 20% in Short Straight Sectionsnon-critical errors, all easily rectified at CERN
L Bottura, M Buzio, JG Perez, A Masi, N Smirnov, A Tikhov, et al., “A Polarity Checker for LHC Magnets”IMMW 2005, 14th International Magnetic Measurement Workshop, CERN, 26-29 September 2005
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7 – 7 – Conclusions and outlookConclusions and outlook7 – 7 – Conclusions and outlookConclusions and outlook
• 4 units built and in use at CERN, proved reliable and easy to use
• 505 cryoassemblies tested, 1200 to go before end 2006
• Automated test procedures for cryodipoles and short straight sections fully established: inner-region insertion quadrupoles/correctors being finalized now
• Possible further developments (not really necessary for series tests) include:- improving the mechanics of the longitudinal transport system - characterization of neglected error sources