06/09/2004 Sebastien Couet 1

Desy Summerstudent Program 2004

Calibration of a 3D Hall probe for magnetic field investigations in

undalators and wigglers.

Outline:

•Motivation

•Experimental procedure

•Magnetic field characterisation

•Hall probe calibration

•Conclusion

06/09/2004 Sebastien Couet 2

Schematic wiggler

Electron remains in the ring for a long time.

They have to stay on track!

Motivation

We have to take great care of the influence of the magnetic

field in the wiggler.

Front view

Bx

Bz

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Motivation

Use of a Hall probe:

• Gives a voltage function of the magnetic field.

• Point like measurement.

• Fast response.

Problem:

•We need a precision of 10-6 T.

Apparition of non linear effect.

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23

3210

3210

xzxzz

xxx

VVcVcBccV

BaBaaV

Given Hall potentials:

Procedure:

• Characterisation of the field

- coil(horizontal)

- dipole magnet(vertical)

• Determination of c1

• Determination of a1, a2, c2

• Determination of cross sensitive parameter c3

Procedure

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Magnetic field characterisation

Use of a NMR probe:

Advantages:

- Gives a very precise absolute value of the field.

Disadvantages:

- No direction information.

- Need homogenous field(not point like).

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In the coil:

ImTBz *2185.40212.0)(

Magnetic field characterisation

(horizontal field)

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Magnetic Field Characterisation

In the dipole magnet:

Bx

Bz

BNMR22zxNMR BBB

22 )( baIBx

(Vertical + horizontal)

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Magnetic field characterisation

Finally, we get the evolution of the slope coefficient:

Conclusion.

Field determination is possible but:

- use of bigger coil

- need of stronger horizontal field

To get more accurate results.

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Hall probe calibration

Offset measurement:

Use of a zero gauss chamber.

Temperature dependence:

Dependence: 10-4 V/ºC

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Hall probe calibration

Horizontal component:zz BccV 10

Need a very precise alignment.

C1=5.10134 0.005 V/T

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Conclusion

Determination of a two component magnetic field is possible with NMR.

Need: - Better homogeneity

- bigger horizontal field

Bigger coil.

Calibration of a 3D hall probe.

- need to improve the precision of the measurement.