arXiv subjects

T. Walker

Publications and source records attributed to T. Walker.

5 recordsLinked to original sources

arXiv2025

AION-10: Technical Design Report for a 10m Atom Interferometer in Oxford

This Technical Design Report presents AION-10, a 10-meter atom interferometer to be located at Oxford University using ultracold strontium atoms to make precision measurements of fundamental physics. AION-10 serves as both a prototype for future larger-scale experiments and a versatile scientific instrument capable of conducting its own diverse physics programme. The design features a 10-meter vertical tower housing two atom interferometer sources in an ultra-high vacuum environment. Key engineering challenges include achieving nanometer-level vibrational stability and precise magnetic field control. Solutions include active vibration isolation, specialized magnetic shielding, and a modular assembly approach using professional lifting equipment. Detailed analysis confirms the design meets all performance requirements, with critical optical components remaining within our specifications 97% of the time under realistic operating conditions. Vacuum and vibration measurements in the host building validate that the instrument will achieve the precision needed for quantum sensing applications. This work establishes the technical foundation for scaling atom interferometry to longer baselines while creating a cutting-edge facility for precision measurements that could advance our understanding of fundamental physics.

physics.atom-ph↗

arXiv2025

A prototype differential atom interferometer for fundamental physics

Gravitational waves and ultralight dark matter are among the most compelling frontiers in fundamental physics, motivating proposals for Very Long-Baseline Atom Interferometers (VLBAIs) such as AION, MAGIS, AICE and AEDGE that aim to detect frequencies at which ground-based and space-borne laser interferometers lose sensitivity. VLBAIs look for signals by comparing the quantum phase evolution of widely separated atomic ensembles interrogated by a common laser. However, their performance depends critically on suppressing noise sources, particularly laser phase noise. Experimental validation of such noise rejection remains an important challenge. Here we demonstrate a prototype differential atom interferometer based on the single-photon clock transition of fermionic 87Sr, realising for the first time a gradiometer configuration with a species intrinsically suited to kilometre-scale and space-baseline operation. The instrument operates at the Standard Quantum Limit with no excess noise beyond atom shot noise, and the differential configuration maintains quantum-limited sensitivity in the presence of several radians of artificially injected laser phase noise per shot, emulating the conditions expected in a VLBAI. We further demonstrate recovery of coherent oscillatory signals across a broad frequency range under fully phase-randomised conditions, a capability that is inaccessible to a single interferometer operating in the same regime. These results provide an experimental validation of the noise-immune measurement principle underlying VLBAIs and mark an important step towards next-generation quantum sensors for gravitational-wave detection and searches for ultralight dark matter.

hep-ex↗

arXiv2022

Development of a hardened THz energy meter for use on the kilojoule-scale, short-pulse OMEGA EP laser

A highly adaptable and robust THz energy meter has been designed and implemented to detect energetic THz pulses from high intensity (greater than 1E18 watts per square centimeter) laser plasma interactions on OMEGA EP. THz radiation from the laser driven target is detected by a shielded pyrometer. A second identical pyrometer is used for background subtraction. The detector can be configured to detect THz pulses in the 1 mm to 30 microns (0.3 to 10 THz) range and pulse energies from joules to microjoules via changes in filtration, aperture size and position. Additional polarization selective filtration can also be used to determine THz pulse polarization. The design incorporates significant radiation and EMP shielding to survive and operate within the OMEGA EP radiation environment. We describe the design, operational principle, calibration and testing of the THz energy meter. The pyrometers were calibrated using a benchtop laser and show linear sensitivity up to 1000 nJ of absorbed energy. Initial results from four OMEGA EP THz experiments detected up to 15 microjoules at the detector, which can correspond to 100s of mJ depending on THz emission and reflection models.

physics.plasm-ph↗

arXiv2008

DUSEL Theory White Paper

The NSF has chosen the site for the Deep Underground Science and Engineering Laboratory (DUSEL) to be in Lead, South Dakota. In fact, the state of South Dakota has already stepped up to the plate and contributed its own funding for the proposed lab, see http://www.sanfordlaboratoryathomestake.org/index.html. The final decision by NSF for funding the Initial Suite of Experiments for DUSEL will be made early in 2009. At that time the NSF Science Board must make a decision. Of order 200 experimentalists have already expressed an interest in performing experiments at DUSEL. In order to assess the interest of the theoretical community, the Center for Cosmology and Astro-Particle Physics (CCAPP) at The Ohio State University (OSU) organized a 3-day DUSEL Theory Workshop in Columbus, Ohio from April 4 - 6, 2008. The workshop focused on the scientific case for six proposed experiments for DUSEL: long baseline neutrino oscillations, proton decay, dark matter, astrophysical neutrinos, neutrinoless double beta decay and N-Nbar oscillations. The outcome of this workshop is the DUSEL Theory White paper addressing the scientific case at a level which may be useful in the decision making process for policy makers at the NSF and in the U.S. Congress. In order to assess the physics interest in the DUSEL project we have posted the DUSEL Theory White paper on the following CCAPP link http://ccapp.osu.edu/whitepaper.html . Please read the white paper and, if you are interested, use the link to show your support by co-signing the white paper.

hep-ph↗

arXiv2000

Spin-axis relaxation in spin-exchange collisions of alkali atoms

We present calculations of spin-relaxation rates of alkali-metal atoms due to the spin-axis interaction acting in binary collisions between the atoms. We show that for the high-temperature conditions of interest here, the spin relaxation rates calculated with classical-path trajectories are nearly the same as those calculated with the distorted-wave Born approximation. We compare these calculations to recent experiments that used magnetic decoupling to isolate spin relaxation due to binary collisions from that due to the formation of triplet van-der-Waals molecules. The values of the spin-axis coupling coefficients deduced from measurements of binary collision rates are consistent with those deduced from molecular decoupling experiments. All the experimental data is consistent with a simple and physically plausible scaling law for the spin-axis coupling coefficients.

physics.atom-ph↗