MEASURING ELECTROMAGNET POLARITY USINGMAGNETIC REMANENCE
WEP014K. P. Wootton, Argonne National Laboratory, Lemont, IL, USA

TURN THE MAGNET ON AND
OFF AGAIN, THEN CHECKTHE POLARITY SAFELYMETHODABSTRACT▪ We motivate the measurement of magnet
polarity in a manner that is electrically safe, bymeasuring the magnetic remanence of ironyokes of normal conducting electromagnets.
▪ This has been used to confirm the polarities ofiron-dominated dipole and quadrupoleelectromagnets at the Linac Extension Area at
the Advanced Photon Source.

MOTIVATION▪ Installation and commissioning of accelerator
systems, a common quality assurance task isensuring that magnets are connected to power
supplies with the correct polarity [1-4].
▪ Powered electromagnets present bothelectrical and magnetic hazards to personnel
approaching them [5].
▪ Different ways of mitigating these hazards,
electrically insulating shielding or shielding tokeep people out of magnetic field.
▪ Another way is to switch off the magnet power
supply, and Lock-Out-Tag-Out (LOTO) thesource of hazardous energy.

DISCUSSION▪ Safe, quick: a few seconds at most permagnet. It took longer to record the result.
▪ Alternatives such as such as little power
supply may introduce new measurement
errors: supply has to be connected with thecorrect polarity.
▪ Future work: a quadrupole with horizontal andvertical corrector trims▪ Why this poster format?
− Why not try something new [6]?

▪ Magnet polarity checker Magnaprobe MKII. The north poleis red, south pole is blue.

Figure 1: Probe.

Figure 2: Polarity convention.
Figure 1: Measurement▪ Procedure steps:
1.

Accelerator enclosure secured.

2.

Accelerator magnets energised at its nominal current
setpoint for 10 minutes using its connected power
supply. This puts the magnet on its hysteresis curve.

3.

Accelerator magnets de-energised, leaving only theremnant field in the magnet.

4.

LOTO accelerator magnets, and verify zero energy
state by Zero Voltage Verification (ZVV). At this point, all
LOTO requirements should be complete to enableauthorised access to the accelerator enclosure.

5.

Lower the accelerator access control system level toauthorised access.

6.

Enter the accelerator enclosure and approach theunpowered electromagnet which is LOTOed.

7.

Measure the polarity of the remnant field (without any
electrical hazard) using a permanent magnet probe.

RESULTS▪ Magnet types 𝑄1
correspond to uprightquadrupole, and 𝐵2 toskew dipole (verticallydeflecting).
▪ Deliberately included
a couple ofquadrupoles from thePTB line, so that wecould associate aknown focussing or
defocussing polarity
with the existing,operational lattice of
the accelerator
beamline.
▪ Booster bypass (BBand LA) had thecorrect polarity, while
newly installed
magnets in the LEA
beamline did not all
have the correct
polarity.
▪ Used this information
to correct the polarityof magnets in the LEA
beamline.

SUMMARY▪ Step-by-step procedure to test the polarity ofmagnets installed with their associated power
supply off.
▪ By exciting the magnet briefly, we propose
putting the magnet on its hysteresis curve, andobserving the polarity of the excitation using
the remnant magnetic field.
▪ A measurement procedure that can be
performed by someone approaching themagnet without electrical hazards.

Table 1: Initial Measurements.
Magnet

TypePTB:Q8
PTB:Q9
BB:QE1
BB:QE2
BB:Q1
BB:BM:1-1
BB:BM:1-2
BB:BM:1-3
BB:BD:1
BD:Q1
BB:Q2
BB:Q3
BB:Q4
BB:BM:2-1
BB:BM:2-2
BB:BM:2-3
BB:Q5
BB:Q6
LA:Q1
LA:Q2
LEA:Q1
LEA:Q2
LEA:Q3
LEA:Q4
LEA:Q5
LEA:Q6
LEA:Q7
LEA:BD

𝑄1𝑄1𝑄1𝑄1
𝑄1𝐵2𝐵2𝐵2𝐵2𝑄1𝑄1𝑄1𝑄1𝐵2𝐵2𝐵2
𝑄1
𝑄1
𝑄1
𝑄1
𝑄1
𝑄1
𝑄1
𝑄1
𝑄1
𝑄1
𝑄1
𝐵2

Polarity
meas.
Blue
Red
Blue
Red
Blue
Blue
Blue
Blue
Red
Red
Red
Blue
Red
Red
Red
Red
Blue
Red
Blue
Red
Blue
Red
Red
Red
Blue
Red
Red
Red

Correct?
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
NoNo
NoNoYes
Yes

Table 2: After Correcting Polarity.
MagnetType

LEA:Q1
LEA:Q2
LEA:Q3
LEA:Q4
LEA:Q5
LEA:Q6
LEA:Q7
LEA:BD

𝑄1
𝑄1
𝑄1
𝑄1
𝑄1
𝑄1
𝑄1
𝐵2

Polarity
meas.
Blue
Red
Blue
Blue
Red
Blue
Red
Red

Correct?
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes

REFERENCES
[1]
[2]
[3]

[4]

[5]
[6]

A. Nadji, “Commissioning of an Accelerator: Tools and Management”, in Proc.
11th European Particle Accelerator Conf. (EPAC’08), Genoa, Italy, Jun. 2008,
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J. Galambos, “Commissioning strategies and methods”, CERN, Geneva,Switzerland, Rep. CERN-2013-001, Mar. 2013.
doi:10.5170/CERN-2013-001.465
S. M. Liuzzo, N. Carmignani, A. Franchi, T. Perron, K. B. Scheidt, E. Taurel,
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Phys.: Conf. Ser., vol. 1350, p. 012022, 2019.
doi:10.1088/1742-6596/1350/1/012022
S. Tepikian et al., “SNS Ring and Transport System Magnet Acceptance andInstallation Preparation”, in Proc. 2003 Particle Accelerator Conf., Portland, OR,USA, May 2003, paper WPPE033, pp. 2390–2392.
doi:10.1109/PAC.2003.1289130
T. Otto, “Risks and Hazards of Particle Accelerator Technologies”, in Safety for
Particle Accelerators, Springer, Cham, Switzerland, 2021, pp. 5–54.
doi:10.1007/978-3-030-57031-6_2
M. Morrison, “How to create a better research poster in less time (#betterposter
Generation 1)”, Video, Mar. 25, 2019.
url:https://youtu.be/1RwJbhkCA58

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