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Measurements of the Ratio of Charge to Mass of Free Electrons Using a Resonant Cavity


Wilts, Charles Harold (1948) Measurements of the Ratio of Charge to Mass of Free Electrons Using a Resonant Cavity. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/4HDY-1E79.


NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document. A deflection method for measuring (e/m[subscript o]) for free electrons is described. A beam of electrons is directed along the axis of a cylindrical cavity excited in the TM[...] mode. A null in the subsequent deflection of the beam occurs when the transit time is nearly equal to an integral number of cycles of the cavity oscillation. The average velocity of the electron beam is calculated from knowledge of the cavity dimensions and the resonant frequency of the cavity. The value of (e/m[subscript o]) is obtained by equating the energy required to accelerate the electrons and their kinetic energy. Three quantities must be measured, a distance, a frequency and a difference of potential, and two very small corrections most be made. Errors due to unmeasurable work function potentials, etc., are eliminated by taking two sets of data with different transit times and subtracting the two energy equations. A probable error of less than 1 part in 10,000 sees to be achievable. Preliminary apparatus gave a value (e/m[subscript o]) = 1.759 [plus or minus] .007 (10)[superscript 7] emu per gram.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:(Electrical Engineering, Physics and Mathematics)
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Electrical Engineering
Minor Option:Mathematics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Smythe, William Ralph
Thesis Committee:
  • Unknown, Unknown
Defense Date:1 January 1948
Record Number:CaltechETD:etd-11212003-110622
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:4612
Deposited By: Imported from ETD-db
Deposited On:21 Nov 2003
Last Modified:22 Mar 2023 22:35

Thesis Files

PDF (Wilts_ch_1948.pdf) - Final Version
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