Photomultiplier tubes (PMTs) are used to detect light that comes from gamma-ray-initiated showers in the earth's atmosphere. The gains of the PMTs are key to determining the amount of light detected and, subsequently, the energy of the incoming gamma ray. In this thesis, a new method of measuring the gain of a PMT is proposed. It relates the PMT gain to the variance of the PMT signal divided by the average current. The new method is mathematically motivated, tested with a series of experiments, and verified using simulations. In addition, it is compared with an existing method of measuring the gain. The new method is shown to be able to predict the gain to within a constant of multiplication. This constant is intrinsic to each PMT and varies from one PMT to another.

Thesis (Ph. D.)--University of California, Berkeley, 1922. / Issued in 1924 under title: Photoelectric thresholds of elements under ordinary conditions.

Author's dissertation, Warszawa. / "Literatura," p. [32]

Thesis (Ph. D.)--Columbia University, 1932. / Includes bibliographical references (p. 26).

The design of a system for studying human eyeball movements is presented. The system output provides eyeball location and pupil size in the form of step-wise voltages which are up-dated a minimum of 4000 times per second. Eye movements up to ± 45 degrees in two dimensions can be tracked. The frequency response of the system ensures continuous tracking of all eye movements including the fastest saccades. The method employed is a photoelectric scan which uses feedback to lock onto the pupil and follow its movements. In the final system, this is performed by a scanning photo-multiplier tube which electronically dissects an optical image of the eye. To check the feasibility of the proposed system before the scanning photomultiplier is purchased, the work is performed in two parts: first the circuitry required to perform the scan is developed and tested without the use of a scanning photomultiplier tube; then an experiment is performed which simulates the scanning photomultiplier and enables the over-all system performance to be evaluated. In the first part, a system is constructed which performs similarly to the final system except that the electronic dissection of the image is performed using an oscilloscope in conjunction with a simple photomultiplier instead of the scanning photomultiplier. This "flying-spot system" is used to test the circuitry required to perform the scan: the circuitry proves to be entirely, satisfactory. In the second part, the simulation enables the signal noise ratio of the scanning photomultiplier to be predicted. On the basis of this, a recommendation is made to purchase the scanning photomultiplier and to construct the complete system. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

No description available.

Typescript, etc. / Digitized by Kansas State University Libraries

Call number: LD2668 .T4 1932 A42

Typescript, etc.

Aerosol particulate matter adversely affects the climate, environment and human health. Mechanistic studies have indicated that ultrafine aerosol nanoparticles, those under 100 nm in diameter, may have significant health impacts due to their relatively high number concentration, surface area and potential for deep penetration into the human lung. However, epidemiological evidence remains limited due to the lack of measurement networks that monitor local concentrations of ultrafine particles. Direct ultraviolet (UV) photoionisation electrically charges aerosol nanoparticles for subsequent detection by a mechanism distinct from the ion-particle collisions of conventional methods. The aim of this work is to evaluate photoionisation theory in order to understand and interpret measurements from a low-cost aerosol particle sensor. To accomplish this, theoretical equations are analysed, modelled and compared with experimental results for validation. The photoelectric yield of aerosol particles is explored in terms of particle size, concentration, material, and morphology giving insight into the interaction of light and particles. This thesis introduces the first analysis of photoionisation, recombination, convection/diffusion and transport of particles in an electric field using analytical, numerical, and computational fluid dynamics (CFD) techniques. Characteristic times and dimensionless parameters are defined to determine regimes under which the measurement system is dominated by each of the charging or transport mechanisms. The level of modelling detail required for accurate prediction of aerosol charging and capture methods is demonstrated over a range of conditions. In a continuous flow of aerosol particles, an electric field is applied to capture charge as it is photoemitted from particles and before the emitted charge and particles can recombine. This method yields a novel current measurement directly representative of photoemission. The CFD model agrees well with electrical current measurements demonstrating that the physics of the problem is suitably represented. It is demonstrated that photoemission is linearly proportional to total (mobility) surface area for a large range of sizes and concentrations of particles of self-similar material and morphology, with agglomerated silver particles having 5$\times$ yield of agglomerated carbon from a propane flame. It is shown for the first time that agglomerated particles have a significantly higher photoelectric yield (2.6$\times$) than sintered, close-packed spheres of the same mobility diameter and material, directly contradicting two of the three previous relevant studies. Close-packed spheres have less material exposed to both the photon flux and the particle's surroundings than an agglomerate of the same particle mobility diameter, thereby reducing photoelectric activity. The photoelectrically active area is defined explicitly in this work to reflect the effect of a particle's morphology; the revised definition produces good agreement with experimental results.