This thesis is a study of the celestial gamma-ray flux. It reviews several of the proposed mechanisms for producing high energy gamma rays and describes several of the attempts to detect their presence. Also included is a short historical review of the spark chamber, along with a qualitative description of its operation.

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An Xipo = 低能电子能量损失谱中多重散射效应的修正 / 安西坡. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (leaves 55-56). / Text in English; abstracts in English and Chinese. / An Xipo = Di neng dian zi neng liang sun shi pu zhong duo zhong san she xiao ying de xiu zheng / An Xipo. / Abstract --- p.i / 摘要 --- p.ii / Acknowledgement --- p.iii / Table of contents --- p.iv / Chapter Chapter 1: --- Introduction --- p.1 / Chapter Chapter 2: --- Background / Chapter 2.1 --- Theory of electron scattering --- p.3 / Chapter 2.1.1 --- Elastic scattering --- p.3 / Chapter 2.1.2 --- Inelastic scattering --- p.4 / Chapter 2.1.2.1 --- The bethe theory --- p.5 / Chapter 2.1.2.2 --- The dielectric formulation --- p.6 / Chapter 2.1.3 --- Excitation of out-shell electrons --- p.6 / Chapter 2.1.3.1 --- Volume plasmon and its dispersion --- p.6 / Chapter 2.1.3.2 --- Single electron excitation --- p.8 / Chapter 2.2 --- Single and multiple scattering process --- p.8 / Chapter Chapter 3 --- Fourier transform based deconvolution method / Chapter 3.1 --- Theory --- p.10 / Chapter 3.1.1 --- Derivation of the single scattering distribution (SSD) --- p.10 / Chapter 3.1.2 --- K-K analyais --- p.12 / Chapter 3.2 --- Effectiveness of the F-log algorithm and data interpretation --- p.13 / Chapter 3.2.1 --- Removal of the plural scattering using F-log --- p.13 / Chapter 3.2.2 --- Deduction of the dielectric function --- p.14 / Chapter 3.3 --- Shortcomings and limitations --- p.15 / Chapter 3.3.1 --- Spectrum collection range --- p.15 / Chapter 3.3.2 --- Artificial peaks in the low energy range (0-5 eV) --- p.18 / Chapter 3.3.3 --- Thin specimens --- p.19 / Chapter 3.3.4 --- Spectra taken at q>0 --- p.22 / Chapter Chapter 4 --- Direct deconvolution method / Chapter 4.1 --- Theory --- p.26 / Chapter 4.2 --- Results and discussion --- p.31 / Chapter 4.2.1 --- Results of the original direct deconvolution algorithm --- p.31 / Chapter 4.2.2 --- Results of the revised direct deconvolution algorithm --- p.32 / Chapter 4.2.2.1 --- Removal of the plural scattering of the spectra taken at zero momentum transfer --- p.32 / Chapter 4.2.2.2 --- Removal of the plural scattering of the spectra taken at q>0 --- p.38 / Chapter 4.2.3 --- Evaluation of the revised direct deconvolution algorithm --- p.39 / Chapter Chapter 5 --- Elastic-inelastic interaction multiple scattering correction / Chapter 5.1 --- Theory --- p.44 / Chapter 5.2 --- Solution --- p.46 / Chapter 5.3 --- Results and discussion --- p.49 / Chapter Chapter 6 --- Conclusions --- p.52 / Reference --- p.54 / Appendix: / Chapter A1 --- The F-log deconvolution program code / Chapter A2 --- The Kramer-Kronig analysis program code / Chapter A3 --- The revised F-log program code to make allowance for the collection range problem / Chapter A4 --- Program code to reconstruct the ZLP / Chapter A5 --- The direct deconvolution program code

Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1990. / Vita. Abstract. Includes bibliographical references (leaves 138-141). Also available via the Internet.

The design, implementation and commissioning of a time-resolved electron energy spectrometer system are discussed. Since its installation at the FELIX free-electron laser user facility in Nieuwegein, The Netherlands, the spectrometer system has been in regular use as a diagnostic and investigative tool. The system provides 0.2% energy resolution with 32 channels, and time resolution of 50 ns. The spectrometer is positioned immediately following the undulator so that the gain medium—the relativistic electron beam—can be probed immediately following its interaction with the optical field in the laser cavity. The system permits real-time calculation and graphical display of key beam parameters as well as the archiving of raw data, and has been used to provide insight into the operation of an FEL in the high slippage, short pulse regime. In particular, direct measurement of the extraction efficiency is possible from macropulse to macropulse. A systematic study of efficiency as a function of wavelength and cavity desynchronisation has been undertaken. At low values of cavity desynchronisation the efficiencies measured exceed the conventional 1/2/V estimate by between 50% and 100% and these results are shown to be consistent with the formation of ultrashort optical pulses—approximately of 6 optical cycles in length. An investigation into the way in which the electron beam energy can be swept on a microsecond time scale has made it possible to produce given sweeps in wavelength—of up to 2 %, limited only by the constraints of the electron beam transport system—which have been used by molecular spectroscopists to excite target molecules through an anharmonic ladder of states. Further evidence for the recent observation of superradiance in an FEL oscillator has been provided by an investigation which shows that the efficiency and intracavity power of the radiation scale respectively as the inverse square root and the inverse square of the cavity losses, verifying the superradiant scaling laws predicted by the supermode theory. An important consequence of this observation is that it indicates that shorter and more intense optical pulses may be produced by increasing the bunch charge and reducing optical cavity losses.

Thesis (Ph. D.) in Physics--University of Maine, 2003. / Includes vita. Includes bibliographical references (leaves 153-158).

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