Surface Processing and Discharge-Conditioning of High Voltage Electrodes for the Ra EDM Experiment

Abstract

The Ra EDM experiment uses a pair of high voltage electrodes to search for the atomic electric dipole moment of ${}^{225}$Ra. We use identical, plane-parallel electrodes with a primary high gradient surface of 200 mm${}^2$ to generate reversible DC electric fields. Our statistical sensitivity is linearly proportional to the electric field strength in the electrode gap. We adapted surface decontamination and processing techniques from accelerator physics literature to chemical polish and clean a suite of newly fabricated large-grain niobium and grade-2 titanium electrodes. Three pairs of niobium electrodes and one pair of titanium electrodes were discharge-conditioned with a custom high voltage test station at electric field strengths as high as $+52.5$ kV/mm and $-51.5$ kV/mm over electrode gap sizes ranging from 0.4 mm to 2.5 mm. One pair of large-grain niobium electrodes was discharge-conditioned and validated to operate at $\pm 20$ kV/mm with steady-state leakage current $\le 25$ pA ($1\sigma$) and a polarity-averaged $98\pm 19$ discharges per hour. These electrodes were installed in the Ra EDM experimental apparatus, replacing a copper electrode pair, and were revalidated to $\pm 20$ kV/mm. The niobium electrodes perform at an electric field strength 3.1 times larger than the legacy copper electrodes and are ultimately limited by the maximum output of our 30 kV bipolar power supply.

arXiv comment16 pages, 11 figures

References in corpus (10)

• Electric Dipole Moments of the Atoms, Molecules, Nuclei and Particles
• Electroweak Baryogenesis and Standard Model CP Violation
• Nuclear time-reversal violation and the Schiff moment of 225Ra
• Collective T- and P- Odd Electromagnetic Moments in Nuclei with Octupole Deformations
• Electric Dipole Moments: A Global Analysis
• Electric dipole moments of Hg, Xe, Rn, Ra, Pu, and TlF induced by the nuclear Schiff moment and limits on time-reversal violating interactions
• Improved limit on the ${}^{225}$Ra electric dipole moment
• Fully self-consistent calculations of nuclear Schiff moments
• A study of DC electrical breakdown in liquid helium through analysis of the empirical breakdown field distributions
• Alignment of a Vector Magnetometer to an Optical Prism

Cited by in corpus (5)

• Opportunities for Fundamental Physics Research with Radioactive Molecules
• Measurement of the Electric Dipole Moment of ${}^{171}$Yb Atoms in an Optical Dipole Trap
• A practical approach to calculating magnetic Johnson noise for precision measurements
• Weinberg operator contribution to the CP-odd nuclear force in the quark model
• Measuring the nuclear magnetic quadrupole moment of optically trapped ytterbium atoms in the metastable state