Latest Publications
Performance Variance of Low Noise Resonant Capacitance Bridges While Replacing their Upgapped MnZn Perrite Cores
12/31/2024
Precision AC resonant capacitance bridges, with a planar printed circuit board transformer using an ungapped MnZn ferrite core, have shown excellent noise performance in high-precision measurements. As many applications use an ensemble of bridges, consistency of performance is critical to the functionality of the systems. If part of the same manufacturing batch and scaled to the same frequency, the noise performance of the ferrite cores at 293 K has a weighted mean variance of <0.3%, with all the cores within a +/- 1% band.
Noise and Low-Temperature Performance
for a Sub-Attofarad Capacitance Sensor for
Precision Measurements, Including Applications in Gravitational Wave Detectors
03/29/2024
We describe the design principles, fabrication, and characterization of a precision AC resonant capacitance bridge (RCB) sensor, based on a resonant differential planar printed circuit board transformer with a solid (ungapped) MnZn ferrite core, demonstrating a short-term sensitivity at 293 K of 0.225 ± 0.005 aF/√Hz at around 120 kHz resonance frequency and 1 Hz Fourier measurement frequency. At 120 K, the RCB short term noise sensitivity is 0.118 ± 0.005 aF/√Hz. We compare the ungapped configuration to five different RCBs: three with a core gap of 65 μm and two with a core gap of 130 μm..
Flight and ground demonstration of reproducibility and stability of photoelectric properties for passive charge management using LEDs
12/22/2022
Charges as small as 1 pC degrade the performance of high precision inertial reference instruments when accumulated on their test masses (TMs). Non-contact charge management systems are required for the most sensitive of these instruments, with the TMs free-floating, and their charges compensated by photoelectrons in a feedback loop with a TM charge measurement. Three space missions have successfully demonstrated this technique: the Relativity Mission, Gravity Probe-B launched in 2004, the LISA Pathfinder launched in 2015, and the UV-LED mission launched on SaudiSat 4 in 2014; with the first two using the 254 nm Hg discharge line and the last one a set of 255 nm UV-LEDs. UV-LEDs represent a significant improvement over the discharge sources, in terms of reliability, lifetime, switching speeds, power consumption, weight, and volume.
Two Approaches for the Passive Charge
Management of Contactless Test Masses
09/02/2022
Free floating test masses (TM) of inertial reference instruments accumulate charge mainly through the triboelectric effect during separation from their housings and, if in the space environment, from cosmic radiation. These charges will degrade the accuracy of high sensitivity accelerometers and drag-free sensors. We demonstrate in ground testing two passive bipolar charge management systems using photoelectrons emitted from gold coated surfaces under illumination by ultraviolet light emitting diodes (UV-LEDs) with 255 nm, 275 nm, and 295 nm central wavelengths.
Passive Charge Management of Contactless Test Masses using Ultraviolet LEDS with Fast and Slow Photoelectrons
08/12/2022
Free floating Test Masses (TM) of inertial reference instruments accumulate charge during separation from their housings and cosmic radiation. We demonstrate two charge management systems using fast and slow photoelectrons emitted from gold coated surfaces.
