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Introduction CLAS12 turn to turn short detector High resolution DC resistance A practical approach to detect turn to turn shorts during superconductive magnet fabrication Giovanni Gabrielli Supervisor: Luciano Elementi Coordinator: Emanuela

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SLIDE 1

Introduction CLAS12 turn to turn short detector High resolution DC resistance

A practical approach to detect turn to turn shorts during superconductive magnet fabrication

Giovanni Gabrielli

Supervisor: Luciano Elementi Coordinator: Emanuela Barzi Fermilab National Accelerator Laboratory

September 27, 2013

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Introduction CLAS12 turn to turn short detector High resolution DC resistance Introduction

CLAS12 for Hall B experiment

Six superconductive coils, forming a toroidal magnet, generate a toroidal magnetic field in order to deviate the debris coming from collisions between particles. Each magnet is a double layered Nb3Sn coil with 117 turns per layer, winded, clamped and cured in Technical Division.

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Introduction CLAS12 turn to turn short detector High resolution DC resistance Introduction

Turn to turn shorts

What is a short? It is an electrical contact between two consecutive turns

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Introduction CLAS12 turn to turn short detector High resolution DC resistance Introduction

Turn to turn shorts

What is a short? It is an electrical contact between two consecutive turns It may appear at any time, most probably during winding or clamping

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SLIDE 5

Introduction CLAS12 turn to turn short detector High resolution DC resistance Introduction

Turn to turn shorts

What is a short? It is an electrical contact between two consecutive turns It may appear at any time, most probably during winding or clamping Its model is a small resistance R, inversely proportional to the area and the pressure

  • f the contact between the turns
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SLIDE 6

Introduction CLAS12 turn to turn short detector High resolution DC resistance Introduction

Turn to turn shorts

What is a short? It is an electrical contact between two consecutive turns It may appear at any time, most probably during winding or clamping Its model is a small resistance R, inversely proportional to the area and the pressure

  • f the contact between the turns

Hard shorts are ≈ 0 Ω, soft shorts can be several Ω

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SLIDE 7

Introduction CLAS12 turn to turn short detector High resolution DC resistance Introduction

Turn to turn shorts

What is a short? It is an electrical contact between two consecutive turns It may appear at any time, most probably during winding or clamping Its model is a small resistance R, inversely proportional to the area and the pressure

  • f the contact between the turns

Hard shorts are ≈ 0 Ω, soft shorts can be several Ω Simulated with resistors or wires (see pictures)

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SLIDE 8

Introduction CLAS12 turn to turn short detector High resolution DC resistance Preliminary study

CLAS12 turn to turn short detector

Task Detect turn to turn shorts, both hard and as soft as possible. Problems: Solution:

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SLIDE 9

Introduction CLAS12 turn to turn short detector High resolution DC resistance Preliminary study

CLAS12 turn to turn short detector

Task Detect turn to turn shorts, both hard and as soft as possible. Problems: Novel approach Solution:

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SLIDE 10

Introduction CLAS12 turn to turn short detector High resolution DC resistance Preliminary study

CLAS12 turn to turn short detector

Task Detect turn to turn shorts, both hard and as soft as possible. Problems: Novel approach TL theory doesn’t work Solution:

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SLIDE 11

Introduction CLAS12 turn to turn short detector High resolution DC resistance Preliminary study

CLAS12 turn to turn short detector

Task Detect turn to turn shorts, both hard and as soft as possible. Problems: Novel approach TL theory doesn’t work Very low DC resistance Solution:

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SLIDE 12

Introduction CLAS12 turn to turn short detector High resolution DC resistance Preliminary study

CLAS12 turn to turn short detector

Task Detect turn to turn shorts, both hard and as soft as possible. Problems: Novel approach TL theory doesn’t work Very low DC resistance Solution: AC steady state, high frequency, high impedance

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SLIDE 13

Introduction CLAS12 turn to turn short detector High resolution DC resistance Preliminary study

CLAS12 turn to turn short detector

Task Detect turn to turn shorts, both hard and as soft as possible. Problems: Novel approach TL theory doesn’t work Very low DC resistance Solution: AC steady state, high frequency, high impedance Significant voltage drop between turns

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SLIDE 14

Introduction CLAS12 turn to turn short detector High resolution DC resistance Preliminary study

AC impedance analysis

Setup: Inductive zone: |Z| ≈ ωL, rising with frequency

Figure: Double layered unclamped coil AC

impedance

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Introduction CLAS12 turn to turn short detector High resolution DC resistance Preliminary study

AC impedance analysis

Setup: Inductive zone: |Z| ≈ ωL, rising with frequency Each turn has higher impedance

Figure: Double layered unclamped coil AC

impedance

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SLIDE 16

Introduction CLAS12 turn to turn short detector High resolution DC resistance Preliminary study

AC impedance analysis

Setup: Inductive zone: |Z| ≈ ωL, rising with frequency Each turn has higher impedance Softer short are more easily detectable

Figure: Double layered unclamped coil AC

impedance

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SLIDE 17

Introduction CLAS12 turn to turn short detector High resolution DC resistance Preliminary study

AC impedance analysis

Setup: Inductive zone: |Z| ≈ ωL, rising with frequency Each turn has higher impedance Softer short are more easily detectable High frequency needed

Figure: Double layered unclamped coil AC

impedance

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SLIDE 18

Introduction CLAS12 turn to turn short detector High resolution DC resistance Setup

General setup

Setup:

Signal Gen Trig coax Ref in Out coax Ch1 in Lock-in Amp Ethernet PC cable Power Amp

  • Ch. A

7 : 3 TIE 1023 Transf cable Probe Out + 1st layer

  • uter turn

Out − 1st layer, inner turn (dotted) OR 2nd layer, outer turn (red) COIL

1 2 3 4 5 6 9 8 7 12 11 10

Test areas

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Introduction CLAS12 turn to turn short detector High resolution DC resistance Setup

General setup

Setup: 19.8 kHz sine wave

Signal Gen Trig coax Ref in Out coax Ch1 in Lock-in Amp Ethernet PC cable Power Amp

  • Ch. A

7 : 3 TIE 1023 Transf cable Probe Out + 1st layer

  • uter turn

Out − 1st layer, inner turn (dotted) OR 2nd layer, outer turn (red) COIL

1 2 3 4 5 6 9 8 7 12 11 10

Test areas

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Introduction CLAS12 turn to turn short detector High resolution DC resistance Setup

General setup

Setup: 19.8 kHz sine wave 30 VRMS output

Signal Gen Trig coax Ref in Out coax Ch1 in Lock-in Amp Ethernet PC cable Power Amp

  • Ch. A

7 : 3 TIE 1023 Transf cable Probe Out + 1st layer

  • uter turn

Out − 1st layer, inner turn (dotted) OR 2nd layer, outer turn (red) COIL

1 2 3 4 5 6 9 8 7 12 11 10

Test areas

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SLIDE 21

Introduction CLAS12 turn to turn short detector High resolution DC resistance Setup

General setup

Setup: 19.8 kHz sine wave 30 VRMS output 3:7 step-up transformer

Signal Gen Trig coax Ref in Out coax Ch1 in Lock-in Amp Ethernet PC cable Power Amp

  • Ch. A

7 : 3 TIE 1023 Transf cable Probe Out + 1st layer

  • uter turn

Out − 1st layer, inner turn (dotted) OR 2nd layer, outer turn (red) COIL

1 2 3 4 5 6 9 8 7 12 11 10

Test areas

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SLIDE 22

Introduction CLAS12 turn to turn short detector High resolution DC resistance Setup

General setup

Setup: 19.8 kHz sine wave 30 VRMS output 3:7 step-up transformer Automatic data acquisition: LabView driver

Signal Gen Trig coax Ref in Out coax Ch1 in Lock-in Amp Ethernet PC cable Power Amp

  • Ch. A

7 : 3 TIE 1023 Transf cable Probe Out + 1st layer

  • uter turn

Out − 1st layer, inner turn (dotted) OR 2nd layer, outer turn (red) COIL

1 2 3 4 5 6 9 8 7 12 11 10

Test areas

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Introduction CLAS12 turn to turn short detector High resolution DC resistance Setup

Transformer

Transformer: Required by the Lock-in Amplifier

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Introduction CLAS12 turn to turn short detector High resolution DC resistance Setup

Transformer

Transformer: Required by the Lock-in Amplifier Low CMRR, huge offset

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SLIDE 25

Introduction CLAS12 turn to turn short detector High resolution DC resistance Setup

Transformer

Transformer: Required by the Lock-in Amplifier Low CMRR, huge offset ”Walking effect”

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Introduction CLAS12 turn to turn short detector High resolution DC resistance Setup

Transformer

Transformer: Required by the Lock-in Amplifier Low CMRR, huge offset ”Walking effect” Parasitic asymmetric capacitive coupling

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SLIDE 27

Introduction CLAS12 turn to turn short detector High resolution DC resistance Setup

Transformer

Transformer: Required by the Lock-in Amplifier Low CMRR, huge offset ”Walking effect” Parasitic asymmetric capacitive coupling Handmade transformer: more distant coils, high frequency wire, negligible parasitic effects

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SLIDE 28

Introduction CLAS12 turn to turn short detector High resolution DC resistance Setup

LabView Driver

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Introduction CLAS12 turn to turn short detector High resolution DC resistance Setup

Procedure

1 A few scannings of all turns, one position (corner 1-12), to see

repeatability, that is the precision of the method

  • ­‑2.00%
  • ­‑1.00%

0.00% 1.00% 2.00% 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 55 58 61 64 67 70 73 76 79 82 85 88 91 94 97 100 103 106 109 112 115

Repetibility ¡ratios ¡i.e. ¡% ¡relative ¡error ¡vs. ¡mean ¡

Normalized ¡error ¡08/29 ¡vs. ¡mean Normalized ¡error ¡08/30 ¡vs. ¡mean Normalized ¡error ¡09/03 ¡vs. ¡mean

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SLIDE 30

Introduction CLAS12 turn to turn short detector High resolution DC resistance Setup

Procedure

1 A few scannings of all turns, one position (corner 1-12), to see

repeatability, that is the precision of the method

2 Scannings with different shorts to see position and amount of

turn to turn voltage losses, that is the sensitivity and resolution of the method.

  • ­‑2.00%
  • ­‑1.00%

0.00% 1.00% 2.00% 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 55 58 61 64 67 70 73 76 79 82 85 88 91 94 97 100 103 106 109 112 115

Repetibility ¡ratios ¡i.e. ¡% ¡relative ¡error ¡vs. ¡mean ¡

Normalized ¡error ¡08/29 ¡vs. ¡mean Normalized ¡error ¡08/30 ¡vs. ¡mean Normalized ¡error ¡09/03 ¡vs. ¡mean

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Introduction CLAS12 turn to turn short detector High resolution DC resistance Results

Non shorted coil voltage curve

0.1 0.2 0.3 0.4 0.5 0.6 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 55 58 61 64 67 70 73 76 79 82 85 88 91 94 97 100 103 106 109 112 115

Turn ¡to ¡turn ¡voltage ¡vs. ¡shorts ¡

08/29 ¡154 ¡mOhm ¡turns ¡37/38 ¡-­‑ ¡Mag ¡(V) ¡@ ¡19.8 ¡kHz 08/29 ¡1 ¡Ohm ¡turns ¡35/36 ¡-­‑ ¡Mag ¡(V) ¡@ ¡19.8 ¡kHz 08/29 ¡154 ¡mOhm ¡turns ¡5/6 ¡-­‑ ¡Mag ¡(V) ¡@ ¡19.8 ¡kHz 08/29 ¡1 ¡Ohm ¡turns ¡9/10 ¡-­‑ ¡Mag ¡(V) ¡@ ¡19.8 ¡kHz Mean ¡Mag ¡(V) ¡08/29, ¡08/30, ¡09/03

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Introduction CLAS12 turn to turn short detector High resolution DC resistance Results

Non shorted vs. shorted coil voltage curves

0.1 0.2 0.3 0.4 0.5 0.6 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 55 58 61 64 67 70 73 76 79 82 85 88 91 94 97 100 103 106 109 112 115

Turn ¡to ¡turn ¡voltage ¡vs. ¡shorts ¡

08/29 ¡154 ¡mOhm ¡turns ¡37/38 ¡-­‑ ¡Mag ¡(V) ¡@ ¡19.8 ¡kHz 08/29 ¡1 ¡Ohm ¡turns ¡35/36 ¡-­‑ ¡Mag ¡(V) ¡@ ¡19.8 ¡kHz 08/29 ¡154 ¡mOhm ¡turns ¡5/6 ¡-­‑ ¡Mag ¡(V) ¡@ ¡19.8 ¡kHz 08/29 ¡1 ¡Ohm ¡turns ¡9/10 ¡-­‑ ¡Mag ¡(V) ¡@ ¡19.8 ¡kHz Mean ¡Mag ¡(V) ¡08/29, ¡08/30, ¡09/03

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Introduction CLAS12 turn to turn short detector High resolution DC resistance Results

Voltage losses

  • ­‑5.00%

0.00% 5.00% 10.00% 15.00% 20.00% 25.00% 30.00% 35.00% 40.00% 45.00% 1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46 49 52 55 58 61 64 67 70 73 76 79 82 85 88 91 94 97 100 103 106 109 112 115

Voltage ¡% ¡loss ¡vs. ¡shorts. ¡

154 ¡mOhm ¡turns ¡37/38 ¡-­‑ ¡% ¡loss ¡@ ¡19.8 ¡kHz 1 ¡Ohm ¡turns ¡35/36 ¡-­‑ ¡% ¡loss ¡@ ¡19.8 ¡kHz 154 ¡mOhm ¡turns ¡5/6 ¡-­‑ ¡% ¡loss ¡@ ¡19.8 ¡kHz 1 ¡Ohm ¡turns ¡9/10 ¡-­‑ ¡% ¡loss ¡@ ¡19.8 ¡kHz

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Introduction CLAS12 turn to turn short detector High resolution DC resistance Results

Non shorted vs. shorted coil phase curves

5 10 15 20 25 30 35 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 43 45 47 49 51 53 55 57 59 61 63 65 67 69 71 73 75 77 79 81 83 85 87 89 91 93 95 97 99 101 103 105 107 109 111 113 115

Turn ¡to ¡turn ¡phase ¡vs. ¡shorts ¡

08/29 ¡154 ¡mOhm ¡turns ¡37/38 ¡-­‑ ¡Phase ¡(deg.) ¡@ ¡19.8 ¡kHz ¡-­‑ ¡Approx. ¡OFS 08/29 ¡1 ¡Ohm ¡turns ¡35/36-­‑ ¡Phase ¡(deg.) ¡@ ¡19.8 ¡kHz ¡-­‑ ¡Approx. ¡OFS 08/29 ¡154 ¡mOhm ¡turns ¡5/6 ¡-­‑ ¡Phase ¡(deg.) ¡@ ¡19.8 ¡kHz ¡-­‑ ¡Approx ¡OFS 08/29 ¡1 ¡Ohm ¡turns ¡9/10 ¡-­‑ ¡Phase ¡(deg.) ¡@ ¡19.8 ¡kHz ¡-­‑ ¡Approx. ¡OFS Mean ¡Phase ¡(deg.) ¡08/29, ¡08/30, ¡09/03

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Introduction CLAS12 turn to turn short detector High resolution DC resistance Results

4 position method

In the very first turns it is harder to see a sharp loss with a smooth bending by its sides. A 4-position scanning can help increase the resolution.

20 40 60 80 100 120 140 160 180 1 3 6 9 1 3 6 9 1 3 6 9 1 3 6 9 1 3 6 9 1 1 1 1 2 2 2 2 3 3 3 3 4 4 4 4 5 5 5 5

Turn ¡to ¡turn ¡voltage ¡-­‑ ¡Turns ¡1 ¡to ¡5 ¡

08/30 ¡1 ¡Ohm ¡turn1-­‑2 ¡pos8 ¡BIS-­‑ ¡Mag ¡(mV) ¡@ ¡19.8 ¡kHz 08/30 ¡154 ¡mOhm ¡turn1-­‑2 ¡pos8 ¡-­‑ ¡Mag ¡(mV) ¡@ ¡19.8 ¡kHz 2 4 6 8 10 12 14 16 18 1 3 6 9 1 3 6 9 1 3 6 9 1 3 6 9 1 3 6 9 1 1 1 1 2 2 2 2 3 3 3 3 4 4 4 4 5 5 5 5

Turn ¡to ¡turn ¡phase ¡-­‑ ¡Turns ¡1 ¡to ¡5 ¡

08/30 ¡1 ¡Ohm ¡turn1-­‑2 ¡pos8 ¡BIS ¡-­‑ ¡Phase ¡(deg.) ¡@ ¡19.8 ¡kHz ¡-­‑ ¡no ¡zeroOFS 08/30 ¡154 ¡mOhm ¡turn1-­‑2 ¡pos8 ¡-­‑ ¡Phase ¡(deg.) ¡@ ¡19.8 ¡kHz ¡-­‑ ¡no ¡zeroOFS

NB: with low SNR, the help of the phase is fundamental.

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Introduction CLAS12 turn to turn short detector High resolution DC resistance Results

Conclusions and problems

Resolution: up to 1 Ω in middle turns, up to a few hundreds mΩ in the first 5. But: Example

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SLIDE 37

Introduction CLAS12 turn to turn short detector High resolution DC resistance Results

Conclusions and problems

Resolution: up to 1 Ω in middle turns, up to a few hundreds mΩ in the first 5. But: Example |Zcoil| = 735 Ω

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SLIDE 38

Introduction CLAS12 turn to turn short detector High resolution DC resistance Results

Conclusions and problems

Resolution: up to 1 Ω in middle turns, up to a few hundreds mΩ in the first 5. But: Example |Zcoil| = 735 Ω |Zturn| ≈ |Zcoil|

117·2 ≈ 3 Ω

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SLIDE 39

Introduction CLAS12 turn to turn short detector High resolution DC resistance Results

Conclusions and problems

Resolution: up to 1 Ω in middle turns, up to a few hundreds mΩ in the first 5. But: Example |Zcoil| = 735 Ω |Zturn| ≈ |Zcoil|

117·2 ≈ 3 Ω

|Zshort| = 150 mΩ

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SLIDE 40

Introduction CLAS12 turn to turn short detector High resolution DC resistance Results

Conclusions and problems

Resolution: up to 1 Ω in middle turns, up to a few hundreds mΩ in the first 5. But: Example |Zcoil| = 735 Ω |Zturn| ≈ |Zcoil|

117·2 ≈ 3 Ω

|Zshort| = 150 mΩ Loss ≈ 1 − |Zshort|

|Zturn| ≈ 95%

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SLIDE 41

Introduction CLAS12 turn to turn short detector High resolution DC resistance Results

Conclusions and problems

Resolution: up to 1 Ω in middle turns, up to a few hundreds mΩ in the first 5. But: Example |Zcoil| = 735 Ω |Zturn| ≈ |Zcoil|

117·2 ≈ 3 Ω

|Zshort| = 150 mΩ Loss ≈ 1 − |Zshort|

|Zturn| ≈ 95%

Problems

1 Why don’t we ever see such

huge losses?

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SLIDE 42

Introduction CLAS12 turn to turn short detector High resolution DC resistance Results

Conclusions and problems

Resolution: up to 1 Ω in middle turns, up to a few hundreds mΩ in the first 5. But: Example |Zcoil| = 735 Ω |Zturn| ≈ |Zcoil|

117·2 ≈ 3 Ω

|Zshort| = 150 mΩ Loss ≈ 1 − |Zshort|

|Zturn| ≈ 95%

Problems

1 Why don’t we ever see such

huge losses?

2 Why should a short influence

even the nearest turns?

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SLIDE 43

Introduction CLAS12 turn to turn short detector High resolution DC resistance Zero model for currents in a shorted coil

Zero model for currents in a shorted coil

Shorted turn (in red) is ”bypassed”

i1 From generator, + COM A ish B i1 ist i1 B COIL

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SLIDE 44

Introduction CLAS12 turn to turn short detector High resolution DC resistance Zero model for currents in a shorted coil

Zero model for currents in a shorted coil

Shorted turn (in red) is ”bypassed” B ∝ V const, i1 ∝

1 |Zcoil|

rises slightly

i1 From generator, + COM A ish B i1 ist i1 B COIL

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SLIDE 45

Introduction CLAS12 turn to turn short detector High resolution DC resistance Zero model for currents in a shorted coil

Zero model for currents in a shorted coil

Shorted turn (in red) is ”bypassed” B ∝ V const, i1 ∝

1 |Zcoil|

rises slightly High ist < 0 generates high Bst < 0 to compensate Btot

i1 From generator, + COM A ish B i1 ist i1 B COIL

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SLIDE 46

Introduction CLAS12 turn to turn short detector High resolution DC resistance Zero model for currents in a shorted coil

Zero model for currents in a shorted coil

Shorted turn (in red) is ”bypassed” B ∝ V const, i1 ∝

1 |Zcoil|

rises slightly High ist < 0 generates high Bst < 0 to compensate Btot High ish gives relatively high voltage drop Vsh

i1 From generator, + COM A ish B i1 ist i1 B COIL

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SLIDE 47

Introduction CLAS12 turn to turn short detector High resolution DC resistance Zero model for currents in a shorted coil

What (almost) really happens

V i0 All non-shorted turns + − Vsh Ish Short ist Shorted turn

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SLIDE 48

Introduction CLAS12 turn to turn short detector High resolution DC resistance Zero model for currents in a shorted coil

What (almost) really happens

V i0 All non-shorted turns + − Vsh Ish Short ist Shorted turn

Mutual induction: the shorted turn is the ”secondary”

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SLIDE 49

Introduction CLAS12 turn to turn short detector High resolution DC resistance Zero model for currents in a shorted coil

What (almost) really happens

V i0 All non-shorted turns + − Vsh Ish Short ist Shorted turn

Mutual induction: the shorted turn is the ”secondary” Vst is still positive because of Lenz’s Law

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SLIDE 50

Introduction CLAS12 turn to turn short detector High resolution DC resistance Zero model for currents in a shorted coil

What (almost) really happens

V i0 All non-shorted turns + − Vsh Ish Short ist Shorted turn

Mutual induction: the shorted turn is the ”secondary” Vst is still positive because of Lenz’s Law Bst < 0 influences mostly the nearest turns

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SLIDE 51

Introduction CLAS12 turn to turn short detector High resolution DC resistance Zero model for currents in a shorted coil

What (almost) really happens

V i0 All non-shorted turns + − Vsh Ish Short ist Shorted turn

Mutual induction: the shorted turn is the ”secondary” Vst is still positive because of Lenz’s Law Bst < 0 influences mostly the nearest turns Despite this is a zero model, experimental data fit this theoretical result with good approximation.

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Introduction CLAS12 turn to turn short detector High resolution DC resistance Setup

High Resolution DC resistance measure

Task Measure small DC resistances with as high precision as possible.

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Introduction CLAS12 turn to turn short detector High resolution DC resistance Setup

High Resolution DC resistance measure

Task Measure small DC resistances with as high precision as possible. 4-wire measurement with 81/2 digits resolution multimeter 3458A from Agilent: less than 4 significant digits for a 1 Ω shunt.

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Introduction CLAS12 turn to turn short detector High resolution DC resistance Setup

High Resolution DC resistance measure

Task Measure small DC resistances with as high precision as possible. 4-wire measurement with 81/2 digits resolution multimeter 3458A from Agilent: less than 4 significant digits for a 1 Ω shunt. ”Enhanced 4W” needed: higher currents for very low resistances.

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Introduction CLAS12 turn to turn short detector High resolution DC resistance Setup

Measuring the shunts

1 3458A as ammeter, I ≈ 1 A

imposed, measured R1 ≈ 1 Ω with 5 significant digits.

I A R1 V

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Introduction CLAS12 turn to turn short detector High resolution DC resistance Setup

Measuring the shunts

1 3458A as ammeter, I ≈ 1 A

imposed, measured R1 ≈ 1 Ω with 5 significant digits.

2 3458A as voltmeter on R1 as

shunt, I ≈ 1 A imposed, measured R2 ≈ 10 mΩ and R3 ≈ 1 mΩ with 4 and 3 significant digits.

I A R1 V I R1 R2 or R3 V V

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Introduction CLAS12 turn to turn short detector High resolution DC resistance Setup

Measuring the shunts

1 3458A as ammeter, I ≈ 1 A

imposed, measured R1 ≈ 1 Ω with 5 significant digits.

2 3458A as voltmeter on R1 as

shunt, I ≈ 1 A imposed, measured R2 ≈ 10 mΩ and R3 ≈ 1 mΩ with 4 and 3 significant digits.

I A R1 V I R1 R2 or R3 V V

3 The same way with just R2 and R3 to double check their ratio

at higher currents.

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Introduction CLAS12 turn to turn short detector High resolution DC resistance Setup

Measuring the coil

4 Coil as load, R2 and R3 as shunts, currents from 1 to 10 A.

Measured Rcoil with no less than 3 significant digits. NB: Voltage source used because current source did not work with reactive loads. − + V I R2 or R3 COIL V V

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Introduction CLAS12 turn to turn short detector High resolution DC resistance Results

Shunts

Im ¡avg Va ¡avg Vb ¡avg Vc ¡avg Ra ¡avg Rb ¡avg Rc ¡avg 1.00538 1.00577 10.02065 0.9955 1.000387913 9.967027393 0.99017287 0.901365 0.90175 8.9885 0.8928 1.00042713 9.972097874 0.990497745 0.8944 0.89479 8.909 0.885 1.000436047 9.960867621 0.989490161 0.89587 8.9345 0.8884 9.972987152 0.991661737 Average: 1.00041703 9.967839188 0.99066020

  • St. ¡Dev.

0.00002091 0.003986671 0.00074192 % ¡St. ¡Dev. 0.002090% 0.039995% 0.074891% Final ¡values: 1.0004 9.968 0.991

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Introduction CLAS12 turn to turn short detector High resolution DC resistance Results

Small test coil

Vshunt ¡(mV) Rshunt ¡(mOhms) I ¡meas ¡(A) Vcoil ¡(mV) R ¡coil ¡(mOhms) 10.325 9.968 1.035814607 26.919 25.98824136 20.831 9.968 2.089787319 54.315 25.99068312 40.791 9.968 4.092195024 106.33 25.98361011 70.705 9.968 7.093198234 184.3 25.98263772 102.76 9.968 10.30898876 267.95 25.99188011 1.025 0.991 1.034308779 26.876 25.98450341 2.0755 0.991 2.094349142 54.397 25.97322428 4.062 0.991 4.09889001 106.46 25.97288528 7.045 0.991 7.108980827 184.65 25.97418737 10.224 0.991 10.31685166 268.1 25.98660994 Average: 25.98284627

  • St. ¡Dev.

0.00675612 % ¡St.Dev. 0.0260% R: 25.98 4 ¡significant ¡digits. At ¡10 ¡A ¡my ¡small ¡coil ¡dissipates ¡around ¡1/4 ¡W, ¡so ¡heating ¡is ¡negligible.

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Introduction CLAS12 turn to turn short detector High resolution DC resistance Results

CLAS12 coil

Vshunt ¡(mV) Rshunt ¡(mOhms) I ¡meas ¡(A) Vcoil ¡(V) R ¡coil ¡(mOhms) 10.767 9.968 1.080156501 0.9124 844.692412 26.497 9.968 2.65820626 2.2447 844.4416198 65.198 9.968 6.540730337 5.5207 844.0494739 102.34 9.968 10.26685393 8.664 843.8807114 1.113 0.991 1.123107972 0.9484 844.4424079 2.589 0.991 2.612512614 2.205 844.0150637 6.211 0.991 6.26740666 5.2891 843.9056674 10.355 0.991 10.44904137 8.8176 843.8668856 Average: 844.1617802

  • St. ¡Dev.

0.2967168 % ¡St.Dev. 0.0351% R: 844 3 ¡significant ¡digits, ¡but ¡St. ¡Dev ¡is ¡much ¡less ¡than ¡half ¡of ¡the ¡last ¡digit. erature ¡o

  • easure ¡is ¡less
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SLIDE 62

Introduction CLAS12 turn to turn short detector High resolution DC resistance

A practical approach to detect turn to turn shorts during superconductive magnet fabrication

Giovanni Gabrielli

Supervisor: Luciano Elementi Coordinator: Emanuela Barzi Fermilab National Accelerator Laboratory

September 27, 2013