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diff --git a/ediffract.tex b/ediffract.tex index 36918f7..5ee2ec8 100644 --- a/ediffract.tex +++ b/ediffract.tex @@ -3,7 +3,7 @@ \chapter{Electron Diffraction} -\textbf{Experiment objectives}: observe diffraction of the beam of electrons on a graphitized carbon target, and to calculate the intra-atomic spacings in the graphite. +\textbf{Experiment objectives}: observe diffraction of the beam of electrons on a graphitized carbon target and calculate the intra-atomic spacings in the graphite. \section*{History} @@ -80,9 +80,9 @@ electron's mass, and $V_a$ is the accelerating voltage. \textbf{Equipment needed}: Electron diffraction apparatus and power supply, tape, ruler. \subsection*{Safety} -You will be working with high voltage. Power supply will be connected for you, +You will be working with high voltage. The power supply will be connected for you, but inspect the apparatus when you arrive \textbf{before} turning the power on. -In any wires are unplugged, ask an instructor to reconnect them. Also, +If any wires are unplugged, ask an instructor to reconnect them. Also, \textbf{before} turning the power on, identify the high voltage contacts on the electron diffraction tube, make sure these connections are well-protected and cannot be touched by accident while taking measurements. @@ -123,7 +123,7 @@ Anode Current & $I_A$& 0.15 mA at 4000 V ( 0.20 mA max.) \begin{enumerate} \item Switch on the heater and wait one minute for the oxide cathode to achieve thermal stability. -\item Slowly increase $V_a$ until you observe two rings to appear around the direct beam. +\item Slowly increase $V_a$ until you observe two rings appear around the direct beam. Slowly change the voltage and determine the highest achievable accelerating voltage, and the lowest voltage when the rings are visible. \item Measure the diffraction angle $\theta$ for both inner and outer rings for 5-10 voltages from that range, @@ -158,7 +158,7 @@ radian: $\phi = s/2R$. To measure $\phi$ carefully place a piece of masking tap Use the graphical method to find the average values for the distances between the atomic planes in the graphite crystal $d_{11}$ (outer ring) and $d_{10}$ (inner ring). To determine the combination of the experimental parameters that -is proportional to $d$, one need to substitute the expression for the +is proportional to $d$, one needs to substitute the expression for the electron's velocity Eq.(\ref{Va}) into the diffraction condition given by Eq.(\ref{bragg}): \begin{equation}\label{bragg.analysis} |