ORCID Profile
0000-0002-0381-5921
Current Organisation
Wayland Additive Ltd
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Publisher: AIP Publishing
Date: 10-2020
DOI: 10.1063/5.0021229
Abstract: A modular, customizable, and low-cost experimental control system for electron spectrometers is described. LabVIEW is used to interface with a suite of Arduino-controlled power supplies, detectors, and stepper motors enabling a variety of different types of measurements to be performed. The structure of the LabVIEW control system and the general design of the Arduino-controlled modules are described. Ex les of results from electron scattering and electron impact ionization experiments performed using this control system are presented.
Publisher: IOP Publishing
Date: 17-01-2018
Publisher: IOP Publishing
Date: 08-10-2020
Abstract: An optical chopper is described that has comparable performance to commercially available units. The new chopper is built within the frame of a hard disk drive, and uses the existing motor and its disk for operation. The rotation speed is measured using a photo-interrupter and is adjusted with a microcontroller. Chopping frequencies from 150 Hz to 1650 Hz with phase jitter less than 0.38 degrees per revolution have been demonstrated. The hardware design and control algorithm are described, and results showing the phase jitter characteristics are presented. The performance of this new design is comparable to that of commercial optical choppers, and can be built for a fraction of their cost.
Publisher: AIP Publishing
Date: 16-05-2019
DOI: 10.1063/1.5097670
Abstract: We report an experimental and theoretical investigation of electron-impact single ionization of the highest occupied molecular orbital 1t2 and the next highest occupied molecular orbital 2a1 states of CH4 at an incident electron energy of 250 eV. Triple differential cross sections measured in two different laboratories were compared with results calculated within the molecular 3-body distorted wave and generalized Sturmian function theoretical models. For ionization of the 1t2 state, the binary peak was observed to have a single maximum near the momentum transfer direction that evolved into a double peak for increasing projectile scattering angles, as has been seen for ionization of atomic p-states. A detailed investigation of this evolution was performed. As expected because of its s-type character, for ionization of the 2a1 state, only a single binary peak was observed. Overall, good agreement was found between experiment and theory.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2019
Publisher: AIP Publishing
Date: 19-11-2019
DOI: 10.1063/1.5127121
Abstract: A new study of electron-impact single ionization of the HOMO 1t2 state of CH4 has been conducted at incident electron energies 20 eV and 40 eV above the ionization energy of the state. Triple differential cross sections were measured from a coplanar symmetric geometry, where scattered and ionized electrons were detected at equal angles, through to the perpendicular geometry where the outgoing electrons emerged orthogonal to the incident electron beam. At the lower energy, the electrons were detected with equal energies of 10 eV, whereas at the higher energy, data were obtained for equal energies of 20 eV and for unequal energies of 5 eV and 35 eV. The results are compared to a molecular 3-body distorted wave approximation that used a full averaging procedure to allow for the random orientation of the target, an orientation averaged molecular orbital model that averages the target wavefunction over all orientations prior to the collision, and a distorted wave Born approximation that does not include postcollisional interactions.
Publisher: American Physical Society (APS)
Date: 09-08-2018
Publisher: IOP Publishing
Date: 11-2017
Publisher: IOP Publishing
Date: 2017
Publisher: American Physical Society (APS)
Date: 23-05-2022
Publisher: IOP Publishing
Date: 14-10-2020
Abstract: Although largely superseded by transistors for small signal lification, the thermionic valve (or tube) still finds use in high-fidelity audio lifiers, in guitar lifiers and in high-power radio and television transmitters, where their power to size scalability has advantages over solid state devices. In the undergraduate experiments detailed here students construct a triode inside a vacuum chamber, and investigate the effects of different designs on signal gain. The characteristics of their triodes are measured to determine the optimal condition for signal lification. The triode is then used to lify an audio signal to determine the frequency response, and they can listen to the results via headphones using an input signal of their choice. This experiment hence introduces students to vacuum technology, to electron beams and to analog electronics.
Publisher: AIP Publishing
Date: 07-2021
DOI: 10.1063/5.0050169
Abstract: A digital system for controlling the frequency of a continuous wave (CW) ring laser is described. The system utilizes Doppler-free absorption to steer the laser onto a resonance peak within a vapor cell and can hold the laser at this frequency for long periods of time using active feedback. The vapor cell is immersed in a sinusoidally varying magnetic field that produces a feedback signal by exploiting the Zeeman effect so that the laser frequency does not need to be dithered to achieve lock. A bias field can also be applied to adjust the frequency over several MHz while maintaining lock. This is advantageous for cold atom studies that require the laser to be red-detuned from resonance. Signals from the absorption cell and magnetic field are digitized and fed to a dedicated microcontroller that calculates and produces the feedback signal. The digital control system is described, and measurements are presented where the locked frequency is compared to data obtained from a commercial wavemeter. The locked frequency standard deviations ranged from 250 to 450 kHz within a 1 h period. The Allan deviations of the locked frequency had the best stability at a value of 6 × 10−11 in a 10 s averaging period. The locking system described here has application in experiments that require very stable laser frequency control and can also be used for regular recalibration of wavemeter parameters. The design can easily be adapted to control different CW laser systems and hence can be used for a range of atomic targets.
Publisher: IOP Publishing
Date: 05-11-2012
Publisher: American Physical Society (APS)
Date: 23-03-2022
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Matthew Harvey.