Abstract/Details

NEW CONCEPTS IN FREE ELECTRON LASERS

GROVER, LOV KUMAR.  Stanford University. ProQuest Dissertations Publishing, 1985. 8506194.

Abstract (summary)

Radiation from undulators (periodic transverse magnetic fields) was first studied by Motz with a view to generating shorter wavelength microwave radiation. Free electron lasers (FEL's) were proposed as sources of coherent optical radiation in 1971 and demonstrated in 1976. Since then there have been various experiments carried out. FEL's have the potential for generating higher powers and more broadly tunable radiation as compared to conventional solid state and gas lasers. The main problem with FEL's is that they are very sensitive to the imperfections on the electron beam, and only very small gain can be obtained with available electron beams. This makes it hard to obtain lasing action, since for this the gain has to be more than the loss. In this dissertation we propse a scheme to reduce this sensitivity.

We first give a simple technique for calculating the small signal characteristics of the free electron laser. The spontaneous emission is calculated by adding up the contribution due to each of the wiggler periods, as in a phased array antenna. Then Madey's theorem is used to obtain the stimulated emission by taking the derivative of the spontaneous emission with respect to the energy of the electrons. Using this technique we derive in a simple manner the small signal characteristics of the uniform wiggler free electron laser; the optical klystron; and for harmonics in a planar wiggler.

We show that the gain-energy acceptance product of the free electron laser is a maximum with respect to variations in dispersion or phase shift. For example in an optical klystron the gain can be increased by having a dispersive section in which interaction with the optical wave is sacrified in order to get increased dispersion. However this causes the gain-energy acceptance product to fall below that of a uniform wiggler FEL with the same number of wiggler periods.

Finally we suggest a scheme to overcome the limitation in interaction length due to the energy spread on the electron beam. In this scheme multiple wiggler sections are cascaded through compensatng sections whose dispersion is opposite that of the wiggler. This opposite dispersion is achieved by having the higher energy electrons traverse a longer path in the compensating section. We show that for N cascaded sections, the gain is N('2) times that of a single section whereas the energy acceptance is the same as that of a single section.

Indexing (details)


Subject
Electrical engineering
Classification
0544: Electrical engineering
Identifier / keyword
Applied sciences
Title
NEW CONCEPTS IN FREE ELECTRON LASERS
Author
GROVER, LOV KUMAR
Number of pages
99
Degree date
1985
School code
0212
Source
DAI-B 46/01, Dissertation Abstracts International
Place of publication
Ann Arbor
Country of publication
United States
University/institution
Stanford University
University location
United States -- California
Degree
Ph.D.
Source type
Dissertation or Thesis
Language
English
Document type
Dissertation/Thesis
Dissertation/thesis number
8506194
ProQuest document ID
303413335
Copyright
Database copyright ProQuest LLC; ProQuest does not claim copyright in the individual underlying works.
Document URL
https://www.proquest.com/docview/303413335