1. Advances in rf Contactless Measurements in Pulsed Magnetic Field. Moaz Altarawneh FSU, NHMFL, LANL. Moaz Altarawneh FSU, NHMFL, LANL. Chuck Mielke LANL. James S. Brooks NHMFL, FSU. Neil Harrison, LANL.

2. outline The traditional Tunnel diode oscillator (TDO). Why we need a new rf method. Proximity Detector Oscillator (PDO). New. Data obtained from the new method.

3. Traditional TDO experimental setup in dc field At room temperature At low temperature C. T. VanDegrift. Rev. Sci. Instrum, 46(3):599, October 1975 Oscillation condition With small coils, circuit needs to be cooled down 3

4. Why we need a new rf method. Bias dependence of the TDO couples electrical noise to frequency. Extreme case of being kicked outside operating range by dB/dt. Bias dependence of the TDO couples electrical noise to frequency. Extreme case of being kicked outside operating range by dB/dt. V induced = 60 mV for 1 mm 2 area in 60T magnet 4

5. The PDO Circuit M. M. Altarawneh, C. H. Mielke and J. S. Brooks. Rev. Sci. Instrum., 80, June 2009 5 The PDO operation is insensitive to voltages induced by pulsed magnetic fields due to its wide operating voltage range (5 to 35 volt) where TDO (~100mV). Less sensitive to the interference from the pulsed field environment No voltage tuning is required (always Oscillating). High stability frequency during the pulse.

6. PDO used for Studying superconductivity in Ba 0.55 K 0.45 Fe 2 As 2 M. M. Altarawneh et al., Phy. Rev. Rapid Comm., 2008.

7. The PDO is used to perform rf measurements at very high magnetic fields This data was collected for a High-temperature superconducting sample (HTS) in the 60 T long pulse magnet at LANL. The PDO is used in 100T magnet too. 1K to 18K 7 The PDO is used in 65T.

8. Thanks To Dr. Stan Tozer and Mr. James A. Powell and electronic shop staff at NHMFL for reproducing a number of the PDO devices to be used at LANL and NHMFL –Tallahassee. Thanks to Dr. Suchitra E. Sebastian for providing figures and data obtained from PDO. This work was funded by LANL LDRD-DR200713. My research is supported in part by NSF DMR-0602859. Dr. Stan Tozer and Mr. James A. Powell and electronic shop staff at NHMFL for reproducing a number of the PDO devices to be used at LANL and NHMFL –Tallahassee. Thanks to Dr. Suchitra E. Sebastian for providing figures and data obtained from PDO. This work was funded by LANL LDRD-DR200713. My research is supported in part by NSF DMR-0602859.

9. Questions…

10. Comparison between the PDO and the TDO methods.