Paul Oxley

College of the Holy Cross · Department of Physics

Experimental cross section measurements for charge transfer and for electron loss from lithium via charge transfer and direct ionization are reported for collisions between light ions and lithium atoms. Beams of protons, deuterium ions, and helium ions intersect a lithium atom beam, and collision cross sections are inferred by measuring the number...

We provide experimental and theoretical details of a simple technique to determine absolute line-of-sight integrated atomic beam densities based on resonant laser absorption. In our experiments, a thermal lithium beam is chopped on and off while the frequency of a laser crossing the beam at right angles is scanned slowly across the resonance transi...

The fine structure interval of the 10p atomic state of 7Li has been measured by laser spectroscopy. Our result of 74.97 (74) MHz for the 10p interval has a precision five times higher than previous measurements of fine structure intervals of Rydberg lithium p states. It also provides an experimental value for the only n = 10 fine structure interval...

In this paper we report details of the apparatus and experimental techniques used to excite Rydberg states of 7Li using multiple diode lasers. Special attention is paid to frequency stabilization of the lasers and we show how three lasers can be stabilized using the fluorescence from a single atomic state. Laser spectroscopy of the 8p,9p, and 11p–1...

Laser-induced florescence spectroscopy of an atomic Lithium beam has been performed and the absolute energies of the np atomic states with 8

We report a measurement of the fine structure interval of the 7Li 10p atomic state with a precision significantly better than previous measurements of fine structure intervals of Rydberg 7Li p states. Our result of 74.97(74) MHz provides an experimental value for the only n=10 fine structure interval which is yet to be calculated. We also report a...

This paper describes an electrical circuit that can be used to automatically magnetize and ac-demagnetize moderately soft magnetic materials and with minor modifications could be used to demagnetize harder magnetic materials and magnetic geological samples. The circuit is straightforward to replicate, easy to use, and low in cost. Independent contr...

The magnetic properties of ten types of ferritic and martensitic stainless steels have been measured at room temperature and at 77K. The steel samples studied were in the annealed state as received from the manufacturer. Our room temperature measurements indicate significantly harder magnetic properties than those quoted in the ASM International Ha...

We have measured the amplitude of optical sidebands produced by RF current modulation of extended cavity diode lasers and studied its dependence on laser drive current, modulation frequency, and external cavity length. The modulated laser light is used in our work for optical repumping for laser cooling (Rb) and atomic beams (Li), but this can be (...

Although commercial packages are available for calculating the electric potential in atom-ion chambers, it is often difficult to input the details of the specific geometry and configuration of various components. One can obtain highly accurate solutions to Laplace's equation for any type of chamber using the finite element method (FEM). FEM is suff...

The finite element method is used to solve Laplace's equation for ion-atom chambers. We first consider a simplified model chamber for which an analytical solution can be obtained; the model chamber serves as a test case to verify the accuracy and convergence of the finite element method. We apply the finite element method to an experimental chamber...

We give experimental details of diode laser excitation of 7Li atoms to the 10p atomic state. The excitation uses three narrow bandwidth grating-stabilized diode lasers to reach the 10p state, via the 2p and 3s states. Simultaneous locking of all three lasers produces a continuous source of 10p atoms. Locking of the 3s-10p transition is achieved by...

Using the Oxford electron beam ion trap (EBIT), we have studied a number of magnetic-dipole fine-structure transitions in highly charged argon and barium, which lie in the visible and near-UV region of the spectrum. Our wavelength measurements, with uncertainties of between 7 and 20 ppm, are the most accurate yet reported using an EBIT as a spectro...

ATRAP’s e+ cooling of in a nested Penning trap has led to reports of cold produced during such cooling by the ATHENA and ATRAP collaborations. To observe , ATHENA uses coincident annihilation detection and ATRAP uses field ionization followed by storage. Advantages of ATRAP’s field ionization method include the complete absence of any background ev...

We have constructed a cryogenic induction motor to turn the rotor of a superconducting magnetic bearing (SMB). Both the motor and the SMB are operated at liquid He temperatures. We give a model for the motor and present measurements of its operation. The rotation speed is very stable. Over 8h it shows an RMS variation of only 0.005Hz from a mean of...

We have constructed an achromatic half-wave plate (AHWP) suitable for the millimeter wavelength band. The AHWP was made from a stack of three sapphire a-cut birefringent plates with the optical axes of the middle plate rotated by 50.5 deg with respect to the aligned axes of the other plates. The measured modulation efficiency of the AHWP at 110 GHz...

We have constructed an achromatic half wave plate (AHWP) suitable for the millimeter wavelength band. The AHWP was made from a stack of three sapphire a-cut birefringent plates with the optical axes of the middle plate rotated by 50.5 degrees with respect to the aligned axes of the other plates. The measured modulation efficiency of the AHWP at 110...

EBEX is a balloon-borne polarimeter designed to measure the intensity and polarization of the cosmic microwave background radiation. The measurements would probe the inflationary epoch that took place shortly after the big bang and would significantly improve constraints on the values of several cosmological parameters. EBEX is unique in its broad...

The density and geometry of p̄ and e+ plasmas in realistic trapping potentials are required if the rate of antihydrogen formation from them is to be understood. A new measurement technique determines these properties of trapped positron (e+) and antiproton (p̄) plasmas, the latter for the first time. The method does not require the common assumptio...

A Reply to the Comment by C. F. Driscoll.

This version is available at the following Publisher URL: http://prl.aps.org

Thesis (Ph. D.)--Harvard University, 2003. Includes bibliographical references.

Cold antihydrogen is produced when antiprotons are repeatedly driven into collisions with cold positrons within a nested Penning trap. Efficient antihydrogen production takes place during many cycles of positron cooling of antiprotons. A first measurement of a distribution of antihydrogen states is made using a preionizing electric field between se...

A background-free observation of cold antihydrogen atoms is made using field ionization followed by antiproton storage, a detection method that provides the first experimental information about antihydrogen atomic states. More antihydrogen atoms can be field ionized in an hour than all the antimatter atoms that have been previously reported, and th...

The stacking of cold antiprotons is currently the only way to accumulate the large numbers of the cold antiprotons that are needed for low energy experiments. Both the largest possible number and the lowest possible temperature are desired, especially for the production and study of cold antihydrogen. The antiprotons accumulated in our particle tra...

Progress in the quest for cold antihydrogen includes the first substantial accumulation of cold positrons and the first demonstration of positron cooling. Stacking of cold antiprotons is key to using the new Antiproton Decelerator facility at CERN.

Only our ATRAP Collaboration is yet able to accumulate and store 4.2 K antiprotons and positrons. The antiprotons come initially from the new Antiproton Decelerator facility at CERN. Good control of such cold antimatter plasmas is key to aspirations to produce and study antihydrogen atoms that are cold enough to confine by their magnetic moments. I...

Positrons are used to cool antiprotons for the first time. The oppositely charged positrons and antiprotons are first simultaneously accumulated in separate Penning trap volumes, and then are spatially merged in a nested Penning trap. The antiprotons cool until they reach a low relative velocity with respect to the cold positrons, the situation exp...

An overview is given of the current spectroscopic effort on the Oxford electron beam ion trap. Recent results from three different experiments are discussed: a precision measurement of the 1s2s 3 S1–1s2p 3 P2 transition in helium-like neon by VUV emission spectroscopy, a measurement of the two-electron contribution to the ground state energy of hel...

A study of the 1s^{2}2s2p ^{3}P_{2}–^{3}P_{1} fine-structure transition in beryllium-like argon is planned on the Oxford electron beam ion trap (EBIT), using laser-induced resonance. This transition wavelength was measured previously as 594.373(4) nm, which is accessible using a dye laser. The ions are produced and excited in the EBIT and are confi...

We describe progress towards a precision measurement of the 2s Lamb shift in hydrogen-like silicon. This will use the Oxford electron beam ion trap (EBIT) as a source of highly charged ions for laser spectroscopy. We have successfully trapped silicon ions in the EBIT, and are determining the optimum operating conditions required to maximize the num...

The evolution of the ion charge state balance in an electron beam ion trap has been studied using a computer program which models the atomic processes occurring within the trap. The predictions of this modelling code have been compared with experimentally-determined charge state distributions. Results are presented here for highly charged nickel.

We have constructed and tested a vacuum system and a simple lithium oven. Lithium atoms from this oven will be excited to high principal quantum number by a combination of three lasers. We have also built and tested the hardware needed to operate the first of these lasers. In the future we will study charge transfer collisions between excited lithi...

The quest for cold antihydrogen, interrupted with the shut-down of LEAR, resumed with the operation of the newest antiproton decelerator (AD) at CERN.[See G.Gabrielse,Adv. in AMO Physics,vol.45,pp.1-38(2001).] Antiprotons injected into the AD with 2.75 GeV of kinetic energy slow to 5.31 MeV before extraction into the ATRAP apparatus, built for anti...