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Progress on the MICE Cooling Channel Magnets

Michael A. GreenLawrence Berkeley National Laboratory

28 June 2005

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3D View of the MICE Cooling Channel

AFC Module

RFCC Module

Coupling Magnet Cryostat

Courtesy of S. Yang Oxford University

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Three Quarter Section View of the MICE Cooling Channel

Coupling Coil

Focusing Magnet Coil

Courtesy of S. Yang Oxford University

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Half Section View of theMICE Cooling Channel

Coupling Coil

Focusing Magnet CoilLiquid Hydrogen Absorber

201 MHz RF Cavities

Courtesy of S. Yang Oxford University

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Cooling Channel Magnet Progress

• The cooling channel consists of three AFC modules and two RFCC modules.

• This report will discuss the progress made since the last meeting on the focusing magnet and the coupling magnet.

• Progress on the tracker magnet (detector magnet) will not be presented. This information was presented on June 27th.

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Focusing Magnet

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The MICE AFC Module

Courtesy of S. Yang Oxford University

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The Center of the MICE AFC Module

Magnet Mandrel

Safety Window

LH2 Pipes

Liquid Helium Feed Pipe

Gas He Pipe

Hydrogen Window

S/C Coil #1

LH2 Absorber

S/C Coil #2

Coil Cover Plate

Courtesy of S. Yang Oxford University

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The Focusing Magnet Parameters

Parameter Non-flip Flip

Coil Inner Radius (mm)Coil Thickness (mm)No. of Layers per CoilNo. Turns per Layer

2638476127

Magnet J (A mm-2)* 72.0 138.2Magnet Current (A)* 130.5 250.7Magnet Self Inductance (H) 137.4 98.6Peak Induction in Coil (T)* 5.04 7.67Magnet Stored Energy (MJ)* 1.17 3.104.2 K Temp. Margin (K)* ~2.0 ~0.6Inter-coil Z Force (MN)* 0.56 3.53

These are the worst cases based on p = 240 MeV/c and b = 420 mm

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Focusing Magnet Progress

• Progress has been made on the focusing magnet quench protection system and in the power system for the magnets.

• The quench simulations show that the focusing magnets can be passively quenched without a formal quench protection system.

• The three focusing magnets can be connected in series. External diodes and resistors are used to control the voltages across the coils.

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Focusing Magnet QuenchOne Magnet & 3 in Series

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Current 1Hot Spot T 1Current 2Hot Spot T 2

Time from Start of the Quench (s)

Magnet Current (A) and the Hot Spot Temperature (K)

Single Magnet

Three Magnets in Series

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250 A Focusing Magnet QuenchFlip Mode & Non-flip Mode

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Current 1Hot Spot T 1Current 3Hot Spot T 3

Time from the Start of the Quench (s)

Current in the Coil (A) and Hot Spot T (K)

Single Magnet Flip Mode

Single Magnet Non-flip Mode

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Focusing Magnet Mandrel Tafter a Quench in the Flip Mode

Max T = 51.9 KMin T = 4.41 KQuench Time = 4 sIstart = 250.8 A

= ~0.80p = 240 MeV/c = 420 mm

Courtesy of H. Witte Oxford University

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Focusing Magnet Mandrel Tafter a Quench in the Non-flip Mode

Max T = 41.7 KMin T = 4.69 KQuench Time = 4 sIstart = 130.3 A

= ~0.80p = 240 MeV/c = 420 mm

Courtesy of H. Witte Oxford University

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Focusing Magnet Mandrel Hot Spot Tas a Function of Time

Max T = 51.9 KMin T = 4.41 KQuench Time = 4 sIstart = 250.8 A

= ~0.80p = 240 MeV/c = 420 mmQuench back occurs.

Courtesy of H. Witte Oxford University

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Focusing Magnet Power System

PSPower Supply10 V, 300 A

Total Inductance from 295 H to 410 H

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Coupling Magnet

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The MICE RFCC Module

Coupling MagnetCavity RF Coupler

Dished Be Window

RF CavityModule Vacuum Vessel

Vacuum PumpMagnet Vacuum Vessel

Courtesy of S. Yang Oxford University

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Coupling Magnet Parameters

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Coupling Magnet Progress

• Progress has been made on the coupling magnet quench protection system and in the power system for the magnets.

• The quench simulations show that the coupling magnets can be passively quenched without a formal quench protection system.

• The two coupling magnets can be connected in series, but it may be better to power the two magnets separately. Cold diodes and resistors are used to control the voltages within the coils.

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Coupling Magnet QuenchOne & Two Magnets in Series

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Current 1Hot Spot T1Current 2Hot Spot T2

Time from the Start of the Magnet Quench (s)

Magnet Current (A) and Coil Hot Spot Temperature (K)

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Coupling Magnet Quench6061-T6 and 1100-O Mandrels

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Current 1Hot Spot T1Current 3Hot Spot T3

Time after the Start of the Quench (s)

Magnet Current (A) and Hot Spot Temperature (K)

6061-T6 Mandrel (RRR = 1.9)

1100-O Mandrel (RRR = 14)

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Coupling Magnet Mandrel Tafter a Quench in the Flip Mode

Max T = 83.9 KMin T = 4.21 KQuench Time = 5 s

= ~0.92p = 240 MeV/c = 420 mm

Courtesy of H. Witte Oxford University

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Coupling Magnet Mandrel Hot Spot Tas a Function of Time

Max T = 83.9 KMin T = 4.21 KQuench Time = 5 s

= ~0.92p = 240 MeV/c = 420 mmQuench back occurs.

Courtesy of H. Witte Oxford University

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Coupling Magnet Power System

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Coupling between Magnet Circuits

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Coupling Coefficients between CoilsMagnet Circuit Self Inductance and the Mutual Inductances in the Flip Mode

Magnet Circuit Self Inductance and the Mutual Inductance in the Non-flip Mode

Courtesy of H. Witte Oxford University

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Conclusions from the Self and MutualInductance Calculations

• Every magnet circuit in MICE is coupled to every other magnet circuit in MICE.

• The charging or discharging of one magnet circuit will affect every other magnet circuit, but the power supplies can handle the effect.

• A quench of one magnet circuit will not drive other magnets normal by changing the currents too much. AC losses induced by a quench do not appear to be a factor, except from mandrel heating.

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Coupling between Magnet CoilCircuits and other Magnet Mandrels

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Currents for Various Cases and theCoupling Coefficients

Coil Currents for Various Cases where p = 240 MeV/c and = 420 mm

Coil to Mandrel Coupling Coefficients for Various Cases

Courtesy of H. Witte Oxford University

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Heating of the Coupling Mandrelby a Focusing Quench (Flip Mode)

Max T = 4.45 KMin T = 4.41 KQuench Time = 4

= ~0.0018p = 240 MeV/c = 420 mm

A quench of the focusing magnet circuit is unlikely to quench the coupling magnet in the flip mode.

Courtesy of H. Witte Oxford University

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Heating of the Coupling Mandrel by a Focusing Quench (Non-flip Mode)

Max T = 4.76 KMin T = 4.69 KQuench Time = 4 s

= ~0.0137p = 240 MeV/c = 420 mm

A quench of the focusing magnet circuit may quench the coupling magnet in the non-flip mode, at high momenta.

Courtesy of H. Witte Oxford University

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Heating of the Focusing Mandrel by a Coupling Quench (Flip Mode)

Max T = 6.30 KMin T = 4.22 KQuench Time = 5 s

= ~0.0813p = 240 MeV/c = 420 mm

A quench of the coupling magnet circuit is likely to quench the focusing magnet in either mode.

Courtesy of H. Witte Oxford University

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Coupling Coefficients between Magnet Circuits and Various Mandrels

The quench of a cooling channel magnet circuit is unlikely to cause a quench of a tracker magnet. A tracker magnet quench won’t quench the channel magnets.

Courtesy of H. Witte Oxford University

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Conclusions from the Magnet Coupling Calculations

• A quench of a focusing magnet is unlikely to quench any other magnet except the coupling magnet at high muon momenta in the non-flip mode.

• A quench of a coupling magnet is likely to quench the focusing magnet except at low muon momenta. A coupling magnet quench will not quench the tracking magnet.

• A quench of the tracker magnet is unlikely to quench any of the other magnets in MICE.

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Concluding Comments

• Engineering progress has been made on all of the MICE magnets and their sub-systems.

• Quench calculations show that the MICE focusing and coupling magnets will quench safely. It is probable that the detector magnets will also quench safely. This will be verified before the next meeting.

• A coupling magnet quench will cause the focusing magnet to quench, but a quench of the other magnets is unlikely to cause a quench of other magnets in MICE.