eberhard pulz karl-heinz jäckel, oliver bronkalla

Eberhard PulzKarl-Heinz Jäckel, Oliver Bronkalla

1. Introduction

2. Serson’s Method

3. Cs-He-Magnetometer

4. Measuring Method

5. Coil System and Switching Technique

6. Theoretical Estimations and Limits

7. Design of Coil System

8. Installation of the Instrument

9. Results

10. Conclusion

1. Introduction

2. Serson’s Method

3. Cs-He-Magnetometer

4. Measuring Method

5. Coil System and Switching Technique

6. Theoretical Estimations and Limits

7. Design of Coil System

8. Installation of the Instrument

9. Results

10. Conclusion

Serson‘s Method

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22

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4

FFFA

A

FFST

TSF

ATSF

ATSF

A - additional field strengthFo - magnetic field strength without an additional fieldF+/- magnetic field strength with an additional fieldS – auxiliary quantityT – magnetic field strength at desired direction

F 0

T - A

A

T

F_

S

F+

Cs-He-Magnetometer

Cs - Lamp

Cs- Sensor

Cs-He- Sensor

He Conversations Formula

0236888.28

frequencyF

Measuring Sequence for Each Second

180 msec

0 200 400 600 800 1000 timemsecfrequency counter in current switching

operation 180 msec

C+ E- F C- E+

True North

Bias field

Top view

Measurement Arrangement

Magnetometer Electronics

Switching Unit

Current source

Frequency Counter

GPS10MHz

Clock

LINUXComputer

SensorCoils

Estimation of Errors

Additional field strength for a given magnetometer noise about 0,005nT rmsand a desired noise in the components of 0,01nT rms

additional field strength of about 5000nT

Effect of tilting of the vertical axis of the bias coilfor ±1’tilting, we got for X= ±13nT

Effect of tilting the azimuth angle between the additional Field and the magnetic meridian

for ±1’tilting, we got for Y= ±5,5nT ΔX= ±3E-03

.g

North South

MirrorLaser

PSD (20x20mm2)(Position Sensitive Diode)

Top viewTop view

E

a

mE

2tan

9

g = 1’ is about 5mm at PSD

a

Coil system

s=2.1•10-2

s=8•10-3

s=1.9•10-2

Conclusions

Cs-He magnetometer absolute accuracy 0.1 nTsum of noise at NGK < 5 pT rms @ 180 msec

Orthogonal coil system: suspended, turnable, LASER controlled

Realtime (GPS) LINUX-controlled system

Result: 1 sec mean values for all components

Reducing the number of manually absolute measurements to some / year

Thank you for your attention