arXiv subjects

Ivar Rydstrom

Publications and source records attributed to Ivar Rydstrom.

4 recordsLinked to original sources

arXiv2025

Correcting impedance measurements for background parasitics to characterize circuit components in cryogenic environments

Predictable circuit response is a critical prerequisite for accurate electronic measurements. We describe a powerful, yet straightforward, experimental method and analysis model that utilizes an affordable LCR meter in conjunction with an in situ parasitic impedance background correction procedure to measure the temperature-dependent impedance (magnitude and phase) of individual passive circuit elements mounted in a cryostat. We show how the model unambiguously identified a 20x drop in capacitance for 22 microF 5XR multilayer ceramic capacitors cooled from 300 K to 360 mK in an environment with parasitic capacitance of order 300 pF. The same experimental procedure, based on a simple two-wire measurement, was also used to successfully measure 10 pF and 22 pF thin-film capacitors and 100 MOhm thick-film resistors. The results showed that the resistor values increased by up to an order of magnitude when the devices were cooled from 300 K to 360 mK. Most importantly, the simple data acquisition method and robust analysis model were shown to effectively extend the accuracy of a simple benchtop LCR meter beyond its manufacturer-guaranteed values for a wide range of measurement frequencies.

physics.ins-det↗

arXiv2024

Low Energy Backgrounds and Excess Noise in a Two-Channel Low-Threshold Calorimeter

We describe observations of low energy excess (LEE) events, background events observed in all light dark matter direct detection calorimeters, and noise in a Transition Edge Sensor based two-channel silicon athermal phonon detector with 375 meV baseline energy resolution. We measure two distinct LEE populations: ``shared'' multichannel events with a pulse shape consistent with substrate athermal phonon events, and sub-eV events that couple nearly exclusively to a single channel with a significantly faster pulse shape. These ``singles'' are consistent with events occurring within the aluminum athermal phonon collection fins. Similarly, our measured detector noise is higher than the theoretical expectation. Measured noise can be split into an uncorrelated component, consistent with shot noise from small energy depositions within the athermal phonon sensor itself, and a correlated component, consistent with shot noise from energy depositions within the silicon substrate's phonon system.

physics.ins-det↗

arXiv2024

A Transition Edge Sensor Operated in Coincidence with a High Sensitivity Athermal Phonon Sensor for Photon Coupled Rare Event Searches

Experimental searches for axions or dark photons that couple to the standard model photon require photosensors with low noise, broadband sensitivity, and near zero backgrounds. Here, we introduce an experimental architecture, in which a small photon sensor, in our case a Transition Edge Sensor (TES) with a photon energy resolution $\sigma_\gamma = 368.4 \pm 0.4$ meV, is colocated on the same substrate as a large high sensitivity athermal phonon sensor (APS) with a phonon energy resolution $\sigma_\mathrm{phonon} = 701 \pm 2$ meV. We show that single 3.061 eV photons absorbed in the photon-sensing TES deposit $\sim$35\% of their energy in the electronic system of the TES, while $\sim$26\% of the photon energy leaks out of the photon-sensing TES during the downconversion process and becomes absorbed by the APS. Backgrounds, which we associate with the broadly observed ``low energy excess'' (LEE), are observed to be largely coupled to either the TES (``singles'' LEE), or phonon system, (``shared'' LEE). At high energies, these backgrounds can be efficiently discriminated from TES photon absorption events, while at low energies, their misidentification as photon events is well modeled. With significant sensitivity improvements to both the TES and APS, this coincidence technique could be used to suppress backgrounds in bosonic dark matter searches down to energies near the superconducting bandgap of the sensor.

physics.ins-det↗

arXiv2024

Linearized Stability of Harada Thin-Shell Wormholes

Using Darmois-Israel-Sen junction conditions, and with help of Visser's cut-and-paste method, we study the dynamics of thin-shell wormholes that are made of two conformally Killing gravity (a.k.a Harada gravity) black holes. We check the energy conditions for different values of the new parameter that Harada introduced, as alternative for dark energy. We examine the radial acceleration to reveal the attractive and repulsive characteristics of the thin-shell wormhole throat. We consider the dynamics and stability of the wormhole around the static solutions of the linearized radial perturbations at the wormhole throat. Finally, we determine the regions of stability by applying the concavity test on the ``speed of sound'' as a function in the throat radius and other spacetime parameters, particularly the new Harada parameter.

gr-qc↗