1 / 30

Development of a Novel Charge Spectrometer at IoP Nuclear and Particle Physics Divisional Conference

This presentation discusses the development of a new charge spectrometer, including its motivation, how it works, empirical principles, experimental details, and recent results. It also reviews the applications, goals, and outlook of the spectrometer.

jeromel
Télécharger la présentation

Development of a Novel Charge Spectrometer at IoP Nuclear and Particle Physics Divisional Conference

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Development of a Novel Charge Spectrometer IoP Nuclear and Particle Physics Divisional Conference John Thornby University of Warwick

  2. Overview • Motivation for a new technique • How it works • Empirical principles • Experimental details • Instrument characterisation • Recent results • Review: Applications, Goals and Outlook

  3. Acknowledgements & Disclaimer Acknowledgements: Dr. Yorck Ramachers, Adrian Lovejoy, Disclaimer: This is not strictly a Nuclear Physics talk!

  4. Motivation for a new Technique • Once upon a time in Warwick… This man had a crazy idea • β-endpoint experiment • View to perhaps measuring absolute υ mass • Borrowing concepts from Mainz & Troitsk BUT • Laboratory scale & fraction of budget!

  5. The Idea… • Past experiments basically count electrons • Replace with a continuous rate of change observable?

  6. The Idea Continued C • β-isotope used as a current source • Charges a capacitor (simply a charge collector) • Charges converted to Voltages • Obtain an integrated β-spectrum e- Isource VC

  7. e- e- e- e- e- e- e- e- e- e- e- e- e- e- e- e- e- e- e- e- So, how does it work? • Process self-quenches: • Accrued e- provide increasing retardingpotential → Cost and noise-free!  • Only most energetic e- overcome repulsion • Eventually no more electrons will make it… • Corresponds to end-point energy. Measure it! Source Collector 63Ni

  8. Integrated β-Spectrum Only rare high-energy electrons contribute → dVC/dt small End-point @ dVC/dt = 0 Most electrons energies contribute → dVC/dt large

  9. Now the clever part… • Capacitor actually a dipole magnetball bearing… • Magnetically levitated & held ~ 10-4 mbar vacuum • Accrued charge cannot escape!

  10. Levitating the Ball • Magnetic forces balance gravity • Unique in-house designed electronics • Provides stable, reproducible configuration Levitation coil Permanent Magnets Hall Probe

  11. Levitation Electronics • Ball equilibrium maintained with μW Power!

  12. Non-Invasive Voltage Measurement – Inverse Kelvin Technique • Supply 11 Hz, 1V p-p sine wave to coil • AC in levitation coil → field oscillates • Ball oscillates up and down above a special pickup plate

  13. Inverse Kelvin Technique Continued • Ball oscillates, capacitance wrt pickup plate changes → induces AC voltage on pickup • Amplify the signal and analyze AC output with PSD (Lock-in amplifier)

  14. Contact potential Calibration Vball(V) ~ 0.2 × VPSD(mV) • Induced AC voltage on pickup proportional to DC voltage on ball • PSD Returns an error voltage

  15. 2mV band Collector Insulation • Need to know how stable voltage is in order to reliably determine the quench/end point • Justified in quoting stability of ±1mV Corresponds to 1meV energy resolution!

  16. Charging the Ball in vacuum • Can we charge the ball in vacuum? • β/conversion electron isotopes • Stimulated emission electrons

  17. Tungsten needle, atomically sharp e- Ball ~ -1.5 kV Plan “B” – Stimulated Emission • Sharp needle at a large –ve potential • At ~ -1.5 kV electrons are emitted • Detected on the ball! ~ 1.5 cm

  18. 0 V ΔV0 = 0.903 V -250 V increments, every 5 minutes ΔV0 = ΔV1 + ΔV2 + ΔV3 -1.5 kV ΔV1 = 0.030 V -1.75 kV ΔV2 = 0.315 V -2.0 kV ΔV3 = 0.561 V Electron Collection Demonstration Offset consistent with genuinely charging the ball

  19. Ball Voltage vs. Time Air Conductivity Measurement • Capacitors can be discharged too… • Low voltages are well-fit by exponential • Not so good for higher voltages • Physics to be investigated here • Need to measure Capacitance, since exponential decay constant is f(C,R)

  20. Outlook, Review and “to do” list… • Exciting and innovativeprototype experiment • Demonstrated insulation & charging of collector • Next step is to use a real source in vacuum • Calibrate HT controller • 109Cd, mono-energetic particles as a reference • Measure Capacitance of ball to surroundings (non-trivial) → Air/Vacuum conductivity • Perform tests in a variety of configurations

  21. Potential Applications • β-endpoint →υ mass • Possible sensitivity to neutrino mass hierarchy • Air & vacuum conductivity - C(P,T) • Gas purities via conductivity • Calibration of a new High Voltage standard • Possible sensitivity to Lunar activity! SUGGESTIONS WELCOME!

  22. The End

  23. Bonus Material…

  24. Why 63Ni? • Cheaper than Tritium! • Well understood Gamow-Teller decay • Easy to handle, Ni plating is easy • Can coat ball, box & plate in Ni • Reduce contact potentials • Q value 66.945 keV (comparitively high) • We are therefore insensitive to electrons resulting from beta decays of lower Q value sources • Can therefore use Pb shielding!

  25. Source C3 C1 To HT system… C2 To amplifier… NB: Not to scale Vacuum Chamber (Earth) Stray Capacitance • Require ball’s capacitance to the system • Spectrum Reconstruction:

  26. Eliminating Externals • 10-4 mbar vacuum • Ball floating (no leakage to ground) • Box “boot-strapped” to same potential as ball • All surfaces coated in Nickel (no contact p.d)

  27. letter of intent - 2001 hep-ex/0109033 Goal: to reach sub-eV sensitivity on Mυ • Strategy • better energy resolution  DE ~ 1 eV • higher statistics  stronger T2 source – longer measuring times • better systematic control  in particular improve background rejection KATRIN design report Jan 2005 Pre-spectrometer selects electrons with E>Q-100 eV (10-7 of the total) • Better detectors: • higher energy resolution • time resolution (TOF) • source imaging Double source control of systematic • Main spectrometer • high resolution • ultra-high vacuum (p<10-11 mbar) • high luminosity KATRIN: Next generation MAC spectrometer

  28. zero neutrino mass finite neutrino mass • effect of: • background • energy resolution • excited final states Q  (dN/dE) dE  2(dE/Q)3 Q-dE And on the Kurie plot… The Kurie plot K(Ee) is a convenient linearization of the beta spectrum Q K(E) Q–Mnc2 Q

  29. The weight of each sub – Kurie plot will be given by |Uej|2, where 3 |ne = SUei |nMi  i=1 K(Ee) Q – M3 Q – M2 Q – M1 K(Ee) Q Ee Ee Mass Hierarchy • Kurie plot  superposition of three different sub - Kurie plots • each sub - Kurie plot corresponds to one of the three different mass eigenvalues

  30. High Voltage System (work in progress)

More Related