1. Eberhard Pulz Karl-Heinz Jäckel, Oliver Bronkalla

2. 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

3. Serson‘s Method A - additional field strength F o - magnetic field strength without an additional field F +/- magnetic field strength with an additional field S – auxiliary quantity T – magnetic field strength at desired direction F 0 T - A A T F_ S F +

4. Cs-He-Magnetometer Cs - Lamp Cs- Sensor Cs-He- Sensor

5. He Conversations Formula

6. Measuring Sequence for Each Second 180 msec 02004006008001000 time msec frequency counter in current switching operation 180 msec C+C+ E-E- FC-C- E+E+ True North Bias field Top view

7. Measurement Arrangement Magnetometer Electronics Switching Unit Current source Frequency Counter GPS 10MHz Clock LINUX Computer Sensor Coils

8. Estimation of Errors  Additional field strength for a given magnetometer noise about 0,005nT rms and 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 coil for ±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

11. . g North South Mirror Laser PSD (20x20mm 2 ) (Position Sensitive Diode) Top view g = 1’ is about 5mm at PSD a Coil system

16. s =2.110 -2 s =810 -3 s =1.910 -2

22. Conclusions  Cs-He magnetometer absolute accuracy 0.1 nT sum 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