IPAC 2012 - Revision history

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Setisadi at 19:32, 13 May 2012

2012-05-13T19:32:03Z

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 latex file: [[File:IPAC_2012_Sadiq.txt]]
-= Latex =
+= latex =
 \documentclass[acus]{JAC2003}
@@ Line 23: / Line 22: @@
 \usepackage{graphicx}
 \usepackage{amstext}
-\usepackage{hyperref}
+%\usepackage{hyperref}
 %\usepackage{caption}
 %\usepackage{subcaption}
@@ Line 169: / Line 171: @@
 Digital images from the JAI camera were extracted in a matrix format in order to take projections on both axes and perform a Gaussian fit. The observed image profiles were not well described by a single Gaussian distribution.  The profiles may be described using a Lorentzian distribution, however, the rms of the Lorentzian function is not defined. The super Gaussian distribution seems to be the best option~\cite{sup-Gau}, because rms values may be directly extracted.
-Fig.~\ref{par-fit}  shows the square of the rms ($\sigma^2_\textnormal{s}$) $vs$ $k_1L$ for $x$ (horizontal) and $y$ (vertical) beam projections along with the parabolic fits using Eq.~\ref{par_fit} . The emittances and Twiss parameters from these fits are summarized in Table.~\ref{results}.  Further details of the fitting procedures are described in reference~\cite{emit-mat}. The normalized emittance is obtained by multiplying the projected emittance by the average relativistic factor $\gamma$ and $\beta$ of the electron beam.
+Fig.~\ref{par-fit}  shows the square of the rms ($\sigma^2_\textnormal{s}$) $vs$ $k_1L$ for $x$ (horizontal) and $y$ (vertical) beam projections along with the parabolic fits using Eq.~\ref{par_fit} . The emittances and Twiss parameters from these fits are summarized in Table.~\ref{results}.  Further details of the fitting procedures are described in reference~\cite{emit-mat}.
 \begin{figure}
 \begin{tabular}{cc}
@@ Line 187: / Line 189: @@
           projected emittance $\epsilon_x$        &   $\mu$m    &    $0.37 \pm 0.02$     \\
            projected emittance $\epsilon_y$            &   $\mu$m    &    $0.30 \pm 0.04$     \\
-	   normalized\thanks{normalization procedure assumes appropriate beam chromaticity} emittance $\epsilon_{n,x}$  &   $\mu$m    &   $10.10 \pm 0.51$         \\
+%	   normalized \footnote{normalization procedure assumes appropriate beam chromaticity.} emittance $\epsilon_{n,x}$  &   $\mu$m    &   $10.10 \pm 0.51$         \\
-	   normalized emittance$^*$ $\epsilon_{n,y}$      &   $\mu$m    &   $8.06 \pm 1.1$          \\
+	   %normalized emittance $\epsilon_{n,y}$      &   $\mu$m    &   $8.06 \pm 1.1$          \\
           $\beta_x$-function                            &  m                           &   $1.40  \pm  0.06$          \\
           $\beta_y$-function                                &  m                           &   $1.17   \pm 0.13$         \\
@@ Line 204: / Line 206: @@
 \section{Conclusions}
-A diagnostic tool was developed and used to measure the beam emittance of the High Rep Rate Linac at the Idaho Accelerator Center. The tool relied on measuring the images generated by the optical transition radiation of the electron beam on a polished thin aluminum target.  The electron beam profile was not described well using a single Gaussian distribution but rather by a super Gaussian or Lorentzian distribution. The system appears to more accurately measure the beam's horizontal size because of the larger dynamic range of the imaging system's pixels.  The projected emittance of the High Rep Rate Linac, similar to medical linacs, at ISU was measured to be less than 0.4~$\mu$m as measured by the OTR based tool described above when accelerating electrons to an energy of 15~MeV.  We plan to perform similar measurements over the energy range of the linac in the near future.
+A diagnostic tool was developed and used to measure the beam emittance of the High Rep Rate Linac at the Idaho Accelerator Center. The tool relied on measuring the images generated by the optical transition radiation of the electron beam on a polished thin aluminum target.  The electron beam profile was not described well using a single Gaussian distribution but rather by a super Gaussian or Lorentzian distribution. The system appears to more accurately measure the beam's horizontal size because of the larger dynamic range of the imaging system's pixels.  The projected emittance of the High Rep Rate Linac, similar to medical linacs, at ISU was measured to be less than 0.4~$\mu$m as measured by the OTR based tool described above when accelerating electrons to an energy of 15~MeV. The normalized emittance may be obtained by multiplying the projected emittance by the average relativistic factor $\gamma$ and $\beta$ of the electron beam. We plan to perform similar measurements over the energy range of the linac in the near future.
 \section{ACKNOWLEDGMENT}

@@ Line 187: / Line 187: @@
           projected emittance $\epsilon_x$        &   $\mu$m    &    $0.37 \pm 0.02$     \\
            projected emittance $\epsilon_y$            &   $\mu$m    &    $0.30 \pm 0.04$     \\
-	   normalized emittance $\epsilon_{n,x}$  &   $\mu$m    &   $10.10 \pm 0.51$         \\
+	   normalized\thanks{normalization procedure assumes appropriate beam chromaticity} emittance $\epsilon_{n,x}$  &   $\mu$m    &   $10.10 \pm 0.51$         \\
-	   normalized emittance $\epsilon_{n,y}$      &   $\mu$m    &   $8.06 \pm 1.1$          \\
+	   normalized emittance$^*$ $\epsilon_{n,y}$      &   $\mu$m    &   $8.06 \pm 1.1$          \\
           $\beta_x$-function                            &  m                           &   $1.40  \pm  0.06$          \\
           $\beta_y$-function                                &  m                           &   $1.17   \pm 0.13$         \\

@@ Line 204: / Line 204: @@
 \section{Conclusions}
-A diagnostic tool was developed and used to measure the beam emittance of the High Rep Rate Linac at the Idaho Accelerator Center. The tool relied on measuring the images generated by the optical transition radiation of the electron beam on a polished thin aluminum target.  The electron beam profile was not described well using a single Gaussian distribution but rather by a super Gaussian or Lorentzian distribution. The system appears to more accurately measure the beam's horizontal size because of the larger dynamic range of the imaging system's pixels.  The prjected emittance of the High Rep Rate Linac, similar to medical linacs, at ISU was measured to be less than 0.4~$\mu$m as measured by the OTR based tool described above when accelerating electrons to an energy of 15~MeV.  We plan to perform similar measurements over the energy range of the linac in the near future.
+A diagnostic tool was developed and used to measure the beam emittance of the High Rep Rate Linac at the Idaho Accelerator Center. The tool relied on measuring the images generated by the optical transition radiation of the electron beam on a polished thin aluminum target.  The electron beam profile was not described well using a single Gaussian distribution but rather by a super Gaussian or Lorentzian distribution. The system appears to more accurately measure the beam's horizontal size because of the larger dynamic range of the imaging system's pixels.  The projected emittance of the High Rep Rate Linac, similar to medical linacs, at ISU was measured to be less than 0.4~$\mu$m as measured by the OTR based tool described above when accelerating electrons to an energy of 15~MeV.  We plan to perform similar measurements over the energy range of the linac in the near future.
 \section{ACKNOWLEDGMENT}

@@ Line 50: / Line 50: @@
 \section{Introduction}
-The HRRL is an S-band electron linac located in the beam lab of the Physics Department at Idaho State University (ISU).  The HRRL accelerates electrons to energies between 3 and 16~MeV with a maximum repetition rate of 1~kHz. The HRRL beamline has recently been reconfigured to generate and collect positrons.
+The HRRL is an S-band electron linac located in the beam lab of the Physics Department at Idaho State University (ISU).  The HRRL accelerates electrons to energies between 3 and 16~MeV with a maximum repetition rate of 1~kHz. The HRRL beamline has recently been reconfigured to generate positrons to be as a secondary beam.
 %The electron beam characteristics of the HRRL are summarized in Table~\ref{tab:hrrl}.
-An Optical Transition Radiation (OTR) based viewer was installed to allow measurements at the high electron currents available using the HRRL. The visible light from the OTR based viewer is produced when a relativistic electron beam crosses the boundary of two mediums with different dielectric constants.  When the electron beam intersects the OTR target at a 45${^\circ}$ angle, visible radiation is emitted at an angle of 90${^\circ}$ with respect to the incident beam direction~\cite{OTR}. These backward-emitted photons are observed using a digital camera and can be used to measure the shape and intensity of the beam based on the OTR image distribution.
+An Optical Transition Radiation (OTR) based viewer was installed to allow measurements at the high electron currents available using the HRRL. The visible light from the OTR based viewer is produced when a relativistic electron beam crosses the boundary of two mediums with different dielectric constants.  Visible radiation is emitted at an angle of 90${^\circ}$ with respect to the incident beam direction~\cite{OTR} when the electron beam intersects the OTR target at a 45${^\circ}$ angle. These backward-emitted photons are observed using a digital camera and can be used to measure the shape and intensity of the electron beam based on the OTR image distribution.
-Emittance is a key parameter in accelerator physics that is used to quantify the quality of an electron beam produced by an accelerator. An emittance measurement can be performed in a several ways~\cite{emit-ways, sole-scan-Kim}. This work used the Quadrupole scanning method~\cite{quad-scan}  to measure emittance, Twiss parameters, and the beam energy.
+Emittance is a key parameter in accelerator physics that is used to quantify the quality of an electron beam produced by an accelerator. An emittance measurement can be performed in a several ways~\cite{emit-ways, sole-scan-Kim}. This work used the Quadrupole scanning method~\cite{quad-scan}  to the measure emittance, Twiss parameters, and the beam energy.
 %\begin{table}[hbt]
 %   \centering
@@ Line 78: / Line 78: @@
 \section{The Experiment}
 \subsection{Quadrupole Scanning Method}
-As shown in Fig.~\ref{q-scan-layout} illustrates the basic components used to measure the emittance  with the quadrupole scanning method.   A quadrupole is positioned at the exit of the linac to focus or de-focus the beam as observed on a downstream view screen. The distance between the quadrupole and the screen was chosen in order to minimize chromatic effects and to satisfy the thin lens approximation.
+Fig.~\ref{q-scan-layout} illustrates the apparatus used to measure the emittance  with the quadrupole scanning method.   A quadrupole is positioned at the exit of the linac to focus or de-focus the beam as observed on a downstream view screen. The 3.1~m distance between the quadrupole and the screen was chosen in order to minimize chromatic effects and to satisfy the thin lens approximation.
 %The quadrupole and the screen are located far away to minimize chromatic effects and to increase the veracity of the thin lens approximation used to calculate beam optics.
 \begin{figure}[htb]
@@ Line 106: / Line 106: @@
 \end{array}\Bigr),
 \end{equation}
-where $l$ is the distance between the scanning quadrupole and the screen. The transfer matrix of the scanning region is given by the matrix product $\mathbf{MQ}$.
+where $l$ is the distance between the scanning quadrupole and the screen. The transfer matrix of the scanning region is given by the matrix product $\mathbf{SQ}$.
 In the horizontal plane, the beam matrix at the screen ($\mathbf{\sigma_{s}}$) is related to the beam matrix of the quadrupole ($\mathbf{\sigma_{q}}$)  using the similarity transformation
 \begin{equation}
@@ Line 134: / Line 134: @@
 \label{par_fit}
 \end{equation}
-The emittance measurement was performed by changing the quadrupole current, which changes $k_{1}L$, and measuring the  corresponding beam image on the view screen. The measured two-dimensional beam image was projected along the images abscissa and ordinate axes.  A Gaussian fitting function is used on each projection to determine the  rms value, $\sigma_\textnormal{s}$ in Eq.~(\ref{par_fit}),  of the image along each axis. Measurements of $\sigma_\textnormal{s}$ for several quadrupole current ($k_{1}L$) is then fit using the parabolic function in Eq.~(\ref{par_fit}) to determine the constants $A$, $B$, and $C$.  The emittance ($\epsilon$)  and the Twiss parameters ($\alpha$ and $\beta$) can be found using Eq.~(\ref{emit-relation}).
+The emittance measurement was performed by changing the quadrupole current, which changes $k_{1}L$, and measuring the  corresponding beam image on the view screen. The measured two-dimensional beam image was projected along the images abscissa and ordinate axes.  A Gaussian fitting function is used on each projection to determine the  rms value, $\sigma_\textnormal{s}$ in Eq.~(\ref{par_fit}). Measurements of $\sigma_\textnormal{s}$ for several quadrupole currents ($k_{1}L$) is then fit using the parabolic function in Eq.~(\ref{par_fit}) to determine the constants $A$, $B$, and $C$.  The emittance ($\epsilon$)  and the Twiss parameters ($\alpha$ and $\beta$) can be found using Eq.~(\ref{emit-relation}).
 \begin{equation}
 \epsilon=\frac{\sqrt{AC}}{l^2},~\beta=\sqrt{\frac{A}{C}},~\alpha=\sqrt{\frac{A}{C}}(B+\frac{1}{l}).
@@ Line 140: / Line 140: @@
 \end{equation}
 \subsection{The OTR Imaging System}
-The OTR target is 10 $\mu$m thick aluminum foil with a 1.25 inch of diameter. The OTR is emitted in a cone shape with the maximum intensity at an angle $1/\gamma$ with respect to the reflecting angle of the electron beam~\cite{OTR}.  Three lenses, 2 inches in diameter, are used for the imaging system to avoid optical distortion at lower electron energies. Focal lengths and position of the lenses are shown in Fig.~\ref{image_sys}. The camera used was a JAI CV-A10GE digital camera with 767 by 576 pixel area. The camera images were taken by triggering the camera during synchronously with the electron gun.
+The OTR target is 10 $\mu$m thick aluminum foil with a 1.25 inch diameter. The OTR is emitted in a cone shape with the maximum intensity at an angle of $1/\gamma$ with respect to the reflecting angle of the electron beam~\cite{OTR}.  Three lenses, 2 inches in diameter, are used for the imaging system to avoid optical distortion at lower electron energies. The focal lengths and position of the lenses are shown in Fig.~\ref{image_sys}. The camera used was a JAI CV-A10GE digital camera with a 767 by 576 pixel area. The camera images were taken by triggering the camera synchronously with the electron gun.
 \begin{figure}
 \centering
@@ Line 164: / Line 164: @@
 \label{bg}
 \end{figure}
-The electron beam energy was measured using a dipole magnet downstream of the quadrupole used for the emittance measurements.  Prior to energizing the dipole, the electron micro-pulse bunch charge  passing through the dipole was measured using a Faraday cup located approximately 50~cm downstream.  The dipole current was adjusted until a maximum beam current was observed on another Faraday cup located just after the 45 degree exit port of the dipole.  A magnetic field map of the dipole suggests that the electron beam energy was 15~MeV.  Future emittance measurements are planned to cover the entire energy range of the linac.
+The electron beam energy was measured using a dipole magnet downstream of the quadrupole used for the emittance measurements.  Prior to energizing the dipole, the electron micro-pulse bunch charge  passing through the dipole was measured using a Faraday cup located approximately 50~cm downstream of the OTR screen.  The dipole current was adjusted until a maximum beam current was observed on another Faraday cup located just after the 45 degree exit port of the dipole.  A magnetic field map of the dipole suggests that the electron beam energy was 15$\pm$1.5~MeV.  Future emittance measurements are planned to cover the entire energy range of the linac.
 \subsection{Data Analysis and Results}
-Images from the JAI camera were calibrated using the OTR target frame.  An LED was used to illuminate the OTR aluminum frame  that has a known inner diameter of 31.75~mm.  Image processing software was used to inscribe a circle on the image to measure the circular OTR inner frame in units of pixels.  The scaling factor can be obtained by dividing this length with the number of pixels observed. The result is a horizontal scaling factor is 0.04327$\pm$0.00016~mm/pixel and vertical scaling factor is 0.04204$\pm$0.00018~mm/pixel.
+Images from the JAI camera were calibrated using the OTR target frame.  An LED was used to illuminate the OTR aluminum frame  that has a known inner diameter of 31.75~mm.  Image processing software was used to inscribe a circle on the image to measure the circular OTR inner frame in units of pixels.  The scaling factor can be obtained by dividing this length with the number of pixels observed. The result is a horizontal scaling factor of 0.04327$\pm$0.00016~mm/pixel and vertical scaling factor of 0.04204$\pm$0.00018~mm/pixel.
 Digital images from the JAI camera were extracted in a matrix format in order to take projections on both axes and perform a Gaussian fit. The observed image profiles were not well described by a single Gaussian distribution.  The profiles may be described using a Lorentzian distribution, however, the rms of the Lorentzian function is not defined. The super Gaussian distribution seems to be the best option~\cite{sup-Gau}, because rms values may be directly extracted.
-Fig.~\ref{par-fit}  shows the square of the rms ($\sigma^2_\textnormal{s}$) $vs$ $k_1L$ for $x$ (horizontal) and $y$ (vertical) beam projections along with the parabolic fits using Eq.~\ref{par_fit} . The emittances and Twiss parameters from these fits are summarized in Table.~\ref{results}.  Further details describing the fitting procedures are described in reference~\cite{emit-mat}. The normalized emittance obtained by projected emittance multiplied with average relativistic factor $\gamma$ and $\beta$ of the electron beam.
+Fig.~\ref{par-fit}  shows the square of the rms ($\sigma^2_\textnormal{s}$) $vs$ $k_1L$ for $x$ (horizontal) and $y$ (vertical) beam projections along with the parabolic fits using Eq.~\ref{par_fit} . The emittances and Twiss parameters from these fits are summarized in Table.~\ref{results}.  Further details of the fitting procedures are described in reference~\cite{emit-mat}. The normalized emittance is obtained by multiplying the projected emittance by the average relativistic factor $\gamma$ and $\beta$ of the electron beam.
 \begin{figure}
 \begin{tabular}{cc}
@@ Line 195: / Line 195: @@
 	    micro-pulse charge                                     &  pC                           &   11         \\
 	    micro-pulse length                                     &  ps                           &   350.16          \\
-	   energy of the beam $E$                                 &  MeV                         &   15         \\
+	   energy of the beam $E$                                 &  MeV                         &   15     $\pm$ 1.5    \\
 	   relative energy spread $\Delta E/E$                                 &  \%                         &   10.4         \\
@@ Line 204: / Line 204: @@
 \section{Conclusions}
-A diagnostic tool was developed and used to measure the beam emittance of the High Rep Rate Linac at the Idaho Accelerator Center. The tool relied on measuring the images generated by the optical transition radiation of the electron beam on a polished thin aluminum target.  The electron beam profile was not described well using a single Gaussian distribution but rather a super Gaussian or Lorentzian distribution. The system appears to more accurately measure the beam's horizontal size because of the larger dynamic range of the imaging system's pixels.  The normalized emittance of the High Rep Rate Linac, similar to medical linacs, at ISU was measured to be less than 10~$\mu$m when accelerating electrons to an energy of 15~MeV as measured by the OTR based tool described above.
+A diagnostic tool was developed and used to measure the beam emittance of the High Rep Rate Linac at the Idaho Accelerator Center. The tool relied on measuring the images generated by the optical transition radiation of the electron beam on a polished thin aluminum target.  The electron beam profile was not described well using a single Gaussian distribution but rather by a super Gaussian or Lorentzian distribution. The system appears to more accurately measure the beam's horizontal size because of the larger dynamic range of the imaging system's pixels.  The prjected emittance of the High Rep Rate Linac, similar to medical linacs, at ISU was measured to be less than 0.4~$\mu$m as measured by the OTR based tool described above when accelerating electrons to an energy of 15~MeV.  We plan to perform similar measurements over the energy range of the linac in the near future.
 \section{ACKNOWLEDGMENT}

@@ Line 143: / Line 143: @@
 \begin{figure}
 \centering
-{\scalebox{0.20} [0.20]{\includegraphics{image_sys.eps}}} {\scalebox{0.20} [0.20]{\includegraphics{imaging_sys}}}
+{\scalebox{0.16} [0.16]{\includegraphics{image_sys.eps}}} {\scalebox{0.20} [0.20]{\includegraphics{imaging_sys}}}
 \caption{The OTR Imaging system.}
 \label{image_sys}