Difference between revisions of "Sadiq Proposal Defense"

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I propose a measurement of the positron production efficiency using a quad triple collection system.  The quad triplet collection system was proposed by ...  A previous experiment at the IAC observed positrons.  I have optimized a beam line to improve that experiment and will quantify the positron production efficiency.
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[[File:sadiq_proposal.pdf]]
  
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= Abstract =
 
  
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I propose measure positron production efficiency for a positron source that uses a quadrupole triplet system to collect positrons from a Tungsten target that are produced when the target is impinged by electrons from the High Rep Rate Linac (HRRL) at  Idaho State University's (ISU) Idaho Accelerator Center (IAC). In the previous experiment conducted at IAC, we observed positrons. Dr. G. Stancari proposed to use quadrupole triplet system to collect positrons. Positrons produced at the target has wide spread of momentum and divergence. Using triplet system we can focus positron beam, thus increase our efficiency. HRRL cavity is relocated and new beamline is setup to use quadrupole triplet system. I also intend to perform simulations to study optimum beamline settings before running experiment. I want to use NaI detectors to measure and quantify the positrons.
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= text =
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= Introduction =
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\documentclass{article} % essential first line
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\usepackage{float} % this is to place figures where requested!
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\usepackage{times} % this uses fonts which will look nice in PDF format
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\usepackage{graphicx} % needed for the figures
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\usepackage{url}
  
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== New Beamline ==
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\usepackage{rotating}
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\usepackage[none]{hyphenat}
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\usepackage{booktabs}
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\usepackage{epstopdf}
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\usepackage{subfig}
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I propose a measurement of the positron production efficiency using the High Repetition Rate Linac (HRRL) located at the Beam Lab of the Physics Department, at Idaho State University (ISU).  HRRL is a S-band electron linac located in the Beam Lab of the Physics Department at Idaho State University (ISU). It is one the 15 small size linacs dedicated for nuclear application operated by the IAC. HRRL can provide electron beam with energies between 3 MeV and 16 MeV, and Maximum repetition rate of 1 kHz. HRRL beamline had recently been reconfigured to generate and collect positrons, while it still can provide electron beam with improved quality.
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%\usepackage{epsfig}
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More details about HRRL is shown in Table 1.
 
  
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{| border="3"  cellpadding="5" cellspacing="0"
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\tolerance=1 % no hyphenation, no zig-zag line.
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| Beam Energy ||Max Peak Current || Repetition Rate ||Max Pulse Length
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\emergencystretch=\maxdimen % no hyphenation, no zig-zag line.
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|-
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\hyphenpenalty=10000 % no hyphenation, no zig-zag line.
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| 16 MeV || 80 mA || 1 kHz || 250 ns (FWHM)
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\hbadness=10000 % no hyphenation, no zig-zag line.
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|}
 
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New beamlien first designed by Dr. G. Stancari, it uses quadrupole triplet to collect positrons. The design further optimized by Dr. Y Kim, and J.Ellis. Beamline is constructed, as shown in Fig.1, in the Beam Lab which is located in the basement of ISU physical sciences complex. Beam Lab is divided into two parts by a L-shaped cement wall. The accelerator cell houses the cavity and magntic elements needed to transport electrons to an experimental cell. The experimental cell is located in an adjacent room to the accelerator cell. The HRRL beamline was reconfigured into an achromat by moving the accelerator cavity to accomdate two dipoles and a system of quadrupole magnets optimized for collecting positrons.
 
  
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In the new beamline, the electron beam exits the HRRL cavity and passes through first the set of quadruple triplet magnets which will be used to focus the electron beam onto the positron target. Positrons produced from the positron target will be collected by second set of quadruple triplet that will be optimized to collect positrons.  The first dipole magnet bends the positrons or electrons, depending on the polarity setting, by 45 degrees towards a second dipole magnet. The second dipole will bend the beam another 45 degrees, thus completes a 90 degree bend. A third quadruple triplet will be used focus the e-/e+ beam, as users desired.
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%\restylefloat{figure}
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\floatstyle{ruled}
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\newfloat{program}{thp}{lop}
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\floatname{program}{Program}
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%\floatstyle{boxed}
  
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[[Image:BeamLine_Yim_10-14-10.png| 450 px |thumb | Fig.1 HRRL beamline for positron generation.]]
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%\renewcommand{\topfraction}{0.85}
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%\renewcommand{\textfraction}{0.1}
  
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{| border="1" cellpadding="4"
 
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|-
 
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|Item || Description
 
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|-
 
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| T1 || Positron target
 
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|-
 
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| T2 || Annihilation target
 
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|-
 
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| EnS || Energy Slit
 
−
|-
 
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| FC1, FC2  || Faraday Cups
 
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|-
 
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| Q1,...Q10 || Quadrupoles
 
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|-
 
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| D1, D2 || Dipoles
 
−
|-
 
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| NaI || NaI Detecotrs
 
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|-
 
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| OTR || OTR screen
 
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|-
 
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| YAG || YAG screen
 
−
|}
 
  
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Positron annihilation target at the end of the beamline is set up for the measurement of the positrons created. When positrons annihilated at the positron target, two 511 keV photons will be created. Photons go back to back, and isotropically. The two detectors placed closely to the to the target, will used to detect these 511 keV photons.
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%\usepackage{lipsum}% http://ctan.org/pkg/lipsum
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%\usepackage[demo]{graphicx}% http://ctan.org/pkg/graphicx
  
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%% Here I adjust the margins
  
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== Earlier measurements ==
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\oddsidemargin -0.25in % Left margin is 1in + this value
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\textwidth 6.75in % Right margin is not set explicitly
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%\topmargin 0in % Top margin is 1in + this value
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\textheight 9in % Bottom margin is not set explicitly
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\columnsep 0.25in % separation between columns
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%\setlength{\parindent}{15pt}
  
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Earlier measurements were conducted at Idaho Accelerator Center of ISU, May of 2008. Setup are shown in Fig.2. Accelerator was operated at 300 Hz repetition rate. Positrons at the end of the linac annihilated in the Ta target, 511 keV photons were observed in both HpGe and NaI detectors. In the Fig.3, the spectrum was taken over 600 seconds.  
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%%          prepended by Figure X. The number X can be referenced
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{| border="1"  |cellpadding="20" cellspacing="0
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\def\EPSFIG[#1]#2#3#4{ % Don't be scared by this monsrosity
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|-
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\begin{figure}[H] % it is a macro to save typing later
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|Run # || MPA file name || W || Ta || Description
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\begin{center} %
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|-
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\includegraphics[#1]{#2} %
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|60|| NaI060.mpa || IN || In|| Dipole at 3 MeV (1.44 on Pot), 300 Hz rep rate, (802 set to 15.7 kV,  27<math>\pm</math>6  counts at 500 keV, Live=600 seconds, grid = 1.64, Gun = 3 kV.
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\end{center} %
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|}
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\caption{#3} %
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\label{#4} %
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\end{figure} %
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} %
  
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{| border="1" cellpadding="4"
 
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|-
 
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|Item || Description
 
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|-
 
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|[http://en.wikipedia.org/wiki/Tantalum Tantalum] Foil|| 6 mm thick 20 mm x 20 mm area
 
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|-
 
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|[http://en.wikipedia.org/wiki/Tungsten Tungsten] Foil|| 2 mm thick 20 mm x 20 mm area
 
−
|-
 
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|[http://en.wikipedia.org/wiki/Phosphorus Phosphorus] Flag|| 1 mil aluminum backing
 
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|-
 
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|[[Media:HpGe_Crystal_GEM-60195-Plus-P.pdf]]|| 81.3mm Diameter, 55.5mm Length
 
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|-
 
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|NaI detector||
 
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|}
 
  
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{| border="1" cellpadding="4"
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%% Define the fields to be displayed by a \maketitle command
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|-
 
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|[[Image:Example.jpg | 200 px |thumb|Fig.2 Setup for 2009 run.]] || [[Image:Run60_HpGe-NaI.gif | 200 px |thumb|Fig.3 Spectrum from HpGe Detector and NaI detecotrs.]] || [[Image:PositronYield_SweeperMagnet_run60-61.gif | 200 px |thumb|Fig.4 ]]
 
−
|}
 
  
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=Preparation for the Positron Production Experiment=
+
\author{Sadiq Setiniyaz (Shadike Saitiniyazi)\thanks{Email: sadik82@gmail.com}}
 +
%{address={Department of Physics, Idaho State University}}
 +
\title{PROPOSAL FOR POSITRON PRODUCTION EFFICIENCY STUDY USING HIGH REPETITION RATE LINAC AT IAC}
  
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== HRRL Emittance measurements ==
+
%%
 +
%% Header now finished
 +
%%
  
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Emittance is an important parameter in accelerator physics. If emittance with twiss parameters are given at the exit of the gun, we will be able to calculate beam size and divergence any point after the exit of the gun. Knowing the beam size and beam divergence on the positron target will greatly help us study the process of creating positron. Emittance with twiss parameters are also key parameters for any accelerator simulations. Also, energy and energy spread of the beam will be measured in the emittance measurement.
+
\begin{document} % Critical
 +
\twocolumn
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\thispagestyle{empty} % Inhibit the page number on this page
 +
\maketitle % Use the \author, \title and \date info
  
−
Optical Transition Radiation (OTR) emittance measurement was carried out on HRRL on March of 2011 with a 10 <math>\mu m</math> thick aluminium screen.  Transition radiation is emitted when a charge moving at a constant velocity cross a boundary between two materials with different dielectric constant. Emitted photons are observed on the camera give us information about the size of the electron beam.
+
%% Next comes the abstract, notice the curly-braces surrounding the
 +
%% text.
  
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We used quadrupole scanning method to measure emittance. In this method we turn off all the quads except one we use for scanning, we change quad current and we observe beam spot changes.  In the Fig.5-7 are shown beam spots for quadrupole coil currents.
+
\abstract{
 +
\indent
  
−
{|  border="0" style="background:transparent;"  align="center"
+
I propose to measure the positron production efficiency for a positron source that uses a quadrupole triplet system to collect positrons from a tungsten target that are produced when the target is impinged by electrons from the High Repetition Rate Linac (HRRL) at Idaho State University's (ISU) Idaho Accelerator Center (IAC). Positrons were observed in May of 2008 at the IAC without the use of a quadrupole triplet collection system. When a 10~MeV electron beam is used on the tungsten target, positrons escaping from the downstream side of the tungsten have a wide momentum spread of 0 to 2~MeV and a large divergence of $\pi$ rad. A quad triplet collection system, after the tungsten target, is used to focus the positron beam and as a result increase our positron collection efficiency. I will install the collection system and associated beam line components and measure the positron production efficiency using the HRRL.}
−
|-
 
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|[[File:OTR_Q1Scan03182011_10.png | 300 px |thumb|Fig.5 OTR image of 0 Amp Q1 coil current.]] ||[[File:OTR_Q1Scan03182011_15.png | 300 px |thumb|Fig.6 OTR image of +1 Amp Q1 coil current.]] ||
 
−
[[File:OTR_Q1Scan03182011_20.png | 300 px |thumb|Fig.7 OTR image of +2 Amp Q1 coil current.]]
 
−
|}
 
  
−
I used the MATLAB to analyze the data. The results shows that:
+
\section{Introduction}
 +
\indent
  
−
<math> \sigma_x^2= (3.678  \pm 0.022) + (-4.17 \pm 0.22)k_1L + (5.55 \pm 0.42)(k_1L)^2 </math>
+
I propose to measure the positron production efficiency for a positron source that uses a quadrupole triplet system to collect positrons from a tungsten target that are produced when the target is impinged by electrons from the HRRL. A polarized positron source, as a new probe to explore nuclear and particle physics at Jefferson Lab, is being studied at the Continuous Electron Beam Accelerator Facility (CEBAF). While their main mission is to optimize polarization, ISU's goal is to optimize positron production efficiency. Additionally, a positron beamline at ISU is also a potential tool for nuclear physics studies. I have measured the emittance of the HRRL electron beam and constructed PMT bases for four NaI detectors. I will install the collection system and associated beam line components to measure the positron production efficiency using the HRRL.
  
−
<math> \epsilon_x = 0.417 \pm 0.023~mm*mrad ~\Rightarrow~ \epsilon_{n,x} = 11.43 \pm 0.64~mm*mrad</math>
+
\section{Previous Measurements}
 +
\indent
  
−
<math> \beta_x=1.385 \pm 0.065, \alpha_x=0.97 \pm 0.07 </math>
+
Earlier positron production measurements were conducted at ISU's IAC in the May of 2008. The setup is shown in Fig.~\ref{fig:2008-pos-beamline} and the beamline elements are described in Table~\ref{tab:2008-pos-beamline-elements}. The accelerator was operated at a 300~Hz repetition rate and 10~MeV energy. Electrons were bent by the first dipole and sent to a 2~mm thick tungsten target. Any positrons produced were focused using two quadrupoles and bent 45 degrees by a second dipole which was set to transport 3~MeV positrons. Positrons were transported to the end of the linac where they annihilated in a Ta target. A HpGe and a NaI detector were used to detect the 511~keV positrons produced as a result of annihilation. Fig.~\ref{fig:2008-spectrum} shows the spectrum taken over a 600 second time interval.
  
−
<math>\sigma_y^2 = (2.843 \pm 0.044) + (1.02 \pm 0.52)k_1L + (3.8 \pm 1.2)(k_1L)^2 </math>
 
  
−
<math> \epsilon_y = 0.338 \pm 0.065~mm*mrad  ~\Rightarrow~  \epsilon_{n,y} = 9.3 \pm 1.8~mm*mrad</math>
+
\begin{figure}[htbp]
 +
\centering
 +
\includegraphics[width=80mm]{2008_positron_measurement_at_IAC.eps}
 +
\caption{The HRRL beamline configured for positron production at IAC in 2008. }
 +
\label{fig:2008-pos-beamline}
 +
\end{figure}
  
−
<math> \beta_y=1.17 \pm 0.19, \alpha_y=0.22 \pm 0.10 </math>
+
\begin{table}[htbp]
 +
\caption{Beamline elements for positron production at IAC in 2008.}
  
−
== Positron Detection using NaI crystal ==
+
\begin{tabular}{ll}
 +
\hline
 +
      \textbf{Item} & {$\textbf {Description}$} \\
 +
\hline
 +
          Tantalum foil  &  6 mm thick 20 mm x 20 mm area  \\
 +
          Tungsten foil  &  2 mm thick 20 mm x 20 mm area    \\
 +
          Phosphorus flag  & 1 mil aluminum backing            \\
 +
          HpGe detector & 81.3mm Diameter, 55.5mm Length \\
 +
          %NaI detector &
 +
\hline
 +
\end{tabular}
 +
\label{tab:2008-pos-beamline-elements}
 +
\end{table}
  
−
To detect positrons created, I want a put Ta target at the end of 90 degree beamline as my Annihilation. When positrons hit W-target, 511 keV photons will be created. I want to use NaI detectors to detect these 511 keV photons.
+
\begin{figure}[htbp]
 +
\centering
 +
  \includegraphics*[scale=0.45]{2008_Run60_HpGe-NaI}
 +
\caption{Spectrum from HpGe Detector and NaI detecotrs.}
 +
\label{fig:2008-spectrum}
 +
\end{figure}
  
−
I acquired some NaI crystals from Idaho Accelerator Center (IAC). I built our own PMT bases for them, since their own bases not working properly. I modified the design of model PA-14 from Saint-Gobain crystals & detectors ltd. Now these detectors are tested and calibrated, and ready to use for the measurement.
+
%\begin{figure}[htbp]
 +
%\centering
 +
%  \includegraphics[scale=0.45]{2008_PositronYield_SweeperMagnet_run60-61}
 +
%\caption{Spectrum.}
 +
%\label{fig:2008-spectrum-zoom}
 +
%\end{figure}
  
−
{| border="1" cellpadding="4"
 
−
|-
 
−
|[[File:IAC_NaI_Detectors_and_Parts_7.png | 450 px ]]|| [[File:Hrrl_pos_det_calb_det3_r2637_r2636_2.png | 450 px]]
 
−
|-
 
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| Fig. The NaI detector and base built. || Fig. Detector 3 calibrated Spectrum.
 
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|-
 
−
|}
 
  
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Even though now the 511 keV peak seems to be very wide and resolution is low, But this can be improved by doing coincidence of two detectors in the experiment.
+
\section{Proposed Beamline}
 +
\indent
  
−
= Future Plan =
 
  
−
== Positron Target ==
+
I propose a measurement of the positron production efficiency using the HRRL. The HRRL can provide electron beams with energies between 3~MeV and 16~MeV, and a maximum repetition rate of 300~Hz. The HRRL beamline has recently been reconfigured to generate and collect positrons, see Fig.~\ref{fig:HRRL-e+-line} and Table~\ref{tab:hrrl}.
  
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A tungsten target will be placed in the space between 1st and 2nd triplet. The tungsten target will be placed inside a big chamber.  
+
\begin{table}[hbt]
 +
  \centering
 +
  \caption{Operational Parameters of The HRRL Linac.}
 +
  \begin{tabular}{lccc}
 +
      \toprule
 +
      Parameter    & Unit  & Value \\
 +
      \midrule
 +
        maximum electron beam energy $E$  &  MeV    &  16  \\
 +
      \midrule
 +
      electron beam peak current $I_{\textnormal{peak}}$ &  mA      &  80    \\
 +
        \midrule
 +
        macro-pulse repetition rate                  &  Hz      &  300  \\
 +
        \midrule
 +
        macro-pulse pulse length (FWHM)          &  ns      &  250    \\
 +
        \midrule
 +
        rms energy spread                                &  \%      &  4.23  \\
 +
  \bottomrule
 +
\end{tabular}
 +
\label{tab:hrrl}
 +
\end{table}
  
−
== Positron Yield ==
+
The new beamline was first designed by Dr. G. Stancari to use a quadrupole triplet system to collect positrons~\cite{stancari}. The design was further optimized by Dr. Y Kim. The final design of the beamline is shown in Fig.~\ref{fig:HRRL-e+-line}. The HRRL accelerator room is divided into two parts by an L-shaped cement wall. The accelerator cell houses the cavity and other elements needed to transport electrons to an experimental cell. The experimental cell is located in a room adjacent to the accelerator cell. The HRRL beamline was reconfigured into an achromat by moving the accelerator cavity to accommodate two dipoles and a system of quadrupole magnets optimized for collecting positrons.
  
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I will insert the first tungsten target and create positrons. I am expecting to collect part these positrons and transport them down the second tungsten target at the end of the 90 degree beamline. By doing these, 511 keV photons will be created and I want to detect them by our NaI detectors.
+
In the new beamline, shown in Fig.~\ref{fig:HRRL-e+-line}, the electron beam exits the cavity and passes through a quadruple triplet  that will focus the electron beam onto the positron target. Positrons produced from the positron target will be collected by the second quadruple triplet that will be optimized to collect positrons. The first dipole magnet bends the positrons/electrons, depending on the magnet polarity, by 45 degrees towards the second dipole magnet. The second dipole will bend the beam another 45 degrees, thus completing a 90 degree bend. A third quadruple triplet will focus the e-/e+ beam, as users desire. All beam elements are described in Table~\ref{tab:new-hrrl-line-elements}.
  
−
= References =
 
  
−
<references/>
 
  
 +
%\begin{figure*}[htbp]
 +
\begin{sidewaysfigure*}[htbp]
  
 +
\centering
 +
%\includegraphics[scale=0.28]{HRRL_Pos_and_Ele_Go}
 +
\includegraphics[scale=0.35]{HRRL_Pos_and_Ele_Go.eps}
 +
\caption{The new HRRL beamline cofiguration for positron generation.}
 +
\label{fig:HRRL-e+-line}
 +
\end{sidewaysfigure*}
  
 +
%\end{figure*}
  
−
[[File:Emittance.tex]]
+
 
 +
 
 +
\begin{table}[hbt]
 +
  \centering
 +
  \caption{The new HRRL positron beamline elements.}
 +
  \begin{tabular}{lccc}
 +
      \toprule
 +
        Item  &  Description \\
 +
      \midrule
 +
        T1    & Positron target \\
 +
      \midrule
 +
        T2    &  Annihilation target \\
 +
        \midrule
 +
        EnS    & Energy Slit  \\
 +
        \midrule
 +
        FC1, FC2& Faraday Cups \\
 +
        \midrule
 +
        Q1,...Q10     & Quadrupoles \\
 +
        \midrule
 +
          D1, D2     & Dipoles \\
 +
        \midrule
 +
        NaI    &  NaI Detecotrs \\
 +
        \midrule
 +
        OTR    &  Optical Transition Radiaiton screen\\
 +
        \midrule
 +
        YAG    & Yttrium Aluminium Garnet screen\\
 +
  \bottomrule
 +
\end{tabular}
 +
\label{tab:new-hrrl-line-elements}
 +
\end{table}
 +
 
 +
%00000000000000000000000000000000000000000000000000000000000
 +
\section{Preparation for the Positron \\ Production Experiment}
 +
\subsection{HRRL Emittance measurements}
 +
\indent
 +
 
 +
 
 +
Emittance, a key parameter in accelerator physics, is used to quantify the quality of an electron beam produced by an accelerator. The beam size and divergence at any point in the beamline can be described using emittance and Twiss parameters.
 +
 
 +
An Optical Transition Radiation (OTR) based viewer was installed to allow measurements at the high electron currents available from 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 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 distribution.
 +
 
 +
The emittance of the HRRL was measured to be less than 0.4~$\mu$m using the OTR based tool at an energy of 15~MeV.  The details of this emittance measurement using the quadrupole scanning method were described in the IPAC12 proceedings~\cite{setiniyaz-q-scan}. The results are summarized in Table~\ref{results}.
 +
 
 +
\begin{table}[hbt]
 +
  \centering
 +
  \caption{Emittance Measurement Results.}
 +
  \begin{tabular}{lcc}
 +
      \toprule
 +
        {Parameter}        & {Unit}    &    {Value}    \\
 +
      \midrule
 +
        projected emittance $\epsilon_x$        &  $\mu$m    &    $0.37 \pm 0.02$    \\
 +
          projected emittance $\epsilon_y$            &  $\mu$m    &    $0.30 \pm 0.04$    \\
 +
%   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    &  $8.06 \pm 1.1$          \\
 +
        $\beta_x$-function                            &  m                          &  $1.40  \pm  0.06$          \\
 +
        $\beta_y$-function                                &  m                          &  $1.17  \pm 0.13$        \\
 +
  $\alpha_x$-function                          &  rad                        &  $0.97  \pm  0.06$          \\
 +
  $\alpha_y$-function                              &  rad                        &  $0.24  \pm 0.07$        \\
 +
    micro-pulse charge                                    &  pC                          &  11        \\
 +
    micro-pulse length                                    &  ps                          &  35          \\
 +
  energy of the beam $E$                                &  MeV                        &  15    $\pm$ 1.6    \\
 +
  relative energy spread $\Delta E/E$                                &  \%                        &  10.4        \\
 +
  \bottomrule
 +
  \end{tabular}
 +
  \label{results}
 +
\end{table}
 +
 
 +
\subsection{Positron Detection using NaI crystals}
 +
\indent
 +
 
 +
A tungsten target will be placed at the end of the 90 degree beamline to annihilate positrons. I want to use two NaI detectors to detect the 511~keV photons created when positrons annihilate. I acquired some NaI crystals from Idaho Accelerator Center (IAC). Since their original bases used a slow post-amplifier, I built new PMT bases. I modified the design of model PA-14 from Saint-Gobain Crystals \& Detectors Ltd. These detectors are tested, calibrated, and ready to be used for the measurement. Fig.~\ref{fig:IAC-dets} shows the crystals and the bases I built. Fig.~\ref{fig:IAC-dets-Co60-Na22-spec} shows the spectrum taken by the detector using button sources.
 +
%I expect by doing coincidence, the resolution of 511~keV peak in the spectrum will be improved.
 +
 
 +
\begin{figure}[htbp]
 +
\centering
 +
\includegraphics[scale=0.08]{IAC_NaI_Detectors}
 +
\caption{The NaI detector and base built.}
 +
\label{fig:IAC-dets}
 +
\end{figure}
 +
 
 +
\begin{figure}[htbp]
 +
\centering
 +
\includegraphics[scale=0.18]{Na22_Co60Spectrum_by_IAC_Detectors}
 +
\caption{Detector 3 calibrated Spectrum.}
 +
\label{fig:IAC-dets-Co60-Na22-spec}
 +
\end{figure}
 +
 
 +
%\subsection{Positron Target Installation}
 +
%\indent
 +
%
 +
%A step motor is ready to be installed once the vacuum chamber is ready. The step motor, shown in the Fig.~\ref{fig:step-motor}, will hold 8 tungsten targets.
 +
%
 +
%\begin{figure}[htbp]
 +
%\centering
 +
%\includegraphics[scale=0.08]{setep_motor}
 +
%\caption{Step motor for holding W targets.}
 +
%\label{fig:step-motor}
 +
%\end{figure}
 +
 
 +
\section{Future Plan}
 +
\indent
 +
 
 +
We want to produce positrons using the HRRL beam line. We can improve positron collection efficiency by applying following methods:
 +
 
 +
1. By using a quadrupole triplet before tungsten a target, we will have control over the beam size and divergence at the target.
 +
 
 +
2. Cryogenically cooled converter will be installed, and these targets will be able to take on more beam power and increase positron yield.
 +
 
 +
3. Positrons will be collected by the quadrupole triplet system, which will improve collection efficiency.
 +
 
 +
4. Simulations will optimize beam elements for positron collection.
 +
 
 +
%\bibliographystyle{unsrt} % Order by citation
 +
%\bibliography{report}
 +
 
 +
\begin{thebibliography}{9}
 +
%{stancari}
 +
%@techreport{stancari,
 +
% title      ={{stancari's proposal-------}},
 +
% month      ={Nov.},
 +
% year = {2005},
 +
% author      ={J. Stancari},
 +
% address    ={Frascati, Italy},
 +
% number      ={},
 +
% institution ={DAFNE Technical Note}
 +
\bibitem{stancari}
 +
G. Stancari and T. Forest "Design of a new beamline for electrons, positrons and photons at the HRRL lab", Pocatello, ID, USA (2009).
 +
 
 +
 
 +
%@techreport{OTR,
 +
% title      ={{Optical Transition Radiation}},
 +
% month      ={},
 +
% year = {1992},
 +
% author      ={B. Gitter},
 +
% address    ={Los Angeles, CA 90024},
 +
% institution ={Particle Beam Physics Lab, Center for Advanced Accelerators, UCLA Department of Physics}
 +
%}
 +
 
 +
\bibitem{OTR}
 +
B. Gitter, Tech. Rep., Los Angeles, USA (1992).
 +
 
 +
%\bibitem{setiniyaz-q-scan}
 +
%@InProceedings{setiniyaz-q-scan,
 +
%  author = {S. Setiniyaz, K. Chouffani, T. Forest, and Y. Kim},
 +
%  title = {TRANSVERSE BEAM EMITTANCE MEASUREMENTS OF A 16 MeV LINAC AT THE IDAHO ACCELERATOR CENTER},
 +
% booktitle = {IPAC2012},%pages = {151--158},
 +
% year = 2012,
 +
% address = {New Orleans, USA}
 +
%}
 +
\bibitem{setiniyaz-q-scan}
 +
S. Setiniyaz, K. Chouffani, T. Forest, and Y. Kim, in $Proc$. $IPAC2012$, New Orleans, USA.
 +
 
 +
%\bibitem{emit-mat}
 +
%C.F. Eckman $et$ $al$., in $Proc$. $IPAC2012$, New Orleans, USA.
 +
 
 +
 
 +
\end{thebibliography}
 +
 
 +
\end{document}

Latest revision as of 23:38, 21 August 2012

File:Sadiq proposal.pdf


text

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\author{Sadiq Setiniyaz (Shadike Saitiniyazi)\thanks{Email: sadik82@gmail.com}} %{address={Department of Physics, Idaho State University}} \title{PROPOSAL FOR POSITRON PRODUCTION EFFICIENCY STUDY USING HIGH REPETITION RATE LINAC AT IAC}

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\abstract{ \indent

I propose to measure the positron production efficiency for a positron source that uses a quadrupole triplet system to collect positrons from a tungsten target that are produced when the target is impinged by electrons from the High Repetition Rate Linac (HRRL) at Idaho State University's (ISU) Idaho Accelerator Center (IAC). Positrons were observed in May of 2008 at the IAC without the use of a quadrupole triplet collection system. When a 10~MeV electron beam is used on the tungsten target, positrons escaping from the downstream side of the tungsten have a wide momentum spread of 0 to 2~MeV and a large divergence of $\pi$ rad. A quad triplet collection system, after the tungsten target, is used to focus the positron beam and as a result increase our positron collection efficiency. I will install the collection system and associated beam line components and measure the positron production efficiency using the HRRL.}

\section{Introduction} \indent

I propose to measure the positron production efficiency for a positron source that uses a quadrupole triplet system to collect positrons from a tungsten target that are produced when the target is impinged by electrons from the HRRL. A polarized positron source, as a new probe to explore nuclear and particle physics at Jefferson Lab, is being studied at the Continuous Electron Beam Accelerator Facility (CEBAF). While their main mission is to optimize polarization, ISU's goal is to optimize positron production efficiency. Additionally, a positron beamline at ISU is also a potential tool for nuclear physics studies. I have measured the emittance of the HRRL electron beam and constructed PMT bases for four NaI detectors. I will install the collection system and associated beam line components to measure the positron production efficiency using the HRRL.

\section{Previous Measurements} \indent

Earlier positron production measurements were conducted at ISU's IAC in the May of 2008. The setup is shown in Fig.~\ref{fig:2008-pos-beamline} and the beamline elements are described in Table~\ref{tab:2008-pos-beamline-elements}. The accelerator was operated at a 300~Hz repetition rate and 10~MeV energy. Electrons were bent by the first dipole and sent to a 2~mm thick tungsten target. Any positrons produced were focused using two quadrupoles and bent 45 degrees by a second dipole which was set to transport 3~MeV positrons. Positrons were transported to the end of the linac where they annihilated in a Ta target. A HpGe and a NaI detector were used to detect the 511~keV positrons produced as a result of annihilation. Fig.~\ref{fig:2008-spectrum} shows the spectrum taken over a 600 second time interval.


\begin{figure}[htbp] \centering \includegraphics[width=80mm]{2008_positron_measurement_at_IAC.eps} \caption{The HRRL beamline configured for positron production at IAC in 2008. } \label{fig:2008-pos-beamline} \end{figure}

\begin{table}[htbp] \caption{Beamline elements for positron production at IAC in 2008.}

\begin{tabular}{ll} \hline 

      \textbf{Item} & {$\textbf {Description}$} \\

\hline 

          Tantalum foil   &  6 mm thick 20 mm x 20 mm area   \\
          Tungsten foil   &  2 mm thick 20 mm x 20 mm area    \\
          Phosphorus flag  & 1 mil aluminum backing             \\
          HpGe detector & 81.3mm Diameter, 55.5mm Length \\
          %NaI detector	&

\hline \end{tabular} \label{tab:2008-pos-beamline-elements} \end{table}

\begin{figure}[htbp] \centering 

 \includegraphics*[scale=0.45]{2008_Run60_HpGe-NaI}

\caption{Spectrum from HpGe Detector and NaI detecotrs.} \label{fig:2008-spectrum} \end{figure}

%\begin{figure}[htbp] %\centering % \includegraphics[scale=0.45]{2008_PositronYield_SweeperMagnet_run60-61} %\caption{Spectrum.} %\label{fig:2008-spectrum-zoom} %\end{figure}


\section{Proposed Beamline} \indent


I propose a measurement of the positron production efficiency using the HRRL. The HRRL can provide electron beams with energies between 3~MeV and 16~MeV, and a maximum repetition rate of 300~Hz. The HRRL beamline has recently been reconfigured to generate and collect positrons, see Fig.~\ref{fig:HRRL-e+-line} and Table~\ref{tab:hrrl}.

\begin{table}[hbt] 

  \centering
  \caption{Operational Parameters of The HRRL Linac.}
  \begin{tabular}{lccc}
      \toprule
      Parameter     & Unit   & Value \\
      \midrule
       maximum electron beam energy $E$   &  MeV     &  16   \\
      \midrule
      electron beam peak current $I_{\textnormal{peak}}$ &  mA      &  80     \\
       \midrule
       macro-pulse repetition rate                   &   Hz       &  300  \\
       \midrule
       macro-pulse pulse length (FWHM)          &   ns       &  250    \\
       \midrule
       rms energy spread                                &  \%      &   4.23   \\
 \bottomrule

\end{tabular} \label{tab:hrrl} \end{table}

The new beamline was first designed by Dr. G. Stancari to use a quadrupole triplet system to collect positrons~\cite{stancari}. The design was further optimized by Dr. Y Kim. The final design of the beamline is shown in Fig.~\ref{fig:HRRL-e+-line}. The HRRL accelerator room is divided into two parts by an L-shaped cement wall. The accelerator cell houses the cavity and other elements needed to transport electrons to an experimental cell. The experimental cell is located in a room adjacent to the accelerator cell. The HRRL beamline was reconfigured into an achromat by moving the accelerator cavity to accommodate two dipoles and a system of quadrupole magnets optimized for collecting positrons.

In the new beamline, shown in Fig.~\ref{fig:HRRL-e+-line}, the electron beam exits the cavity and passes through a quadruple triplet that will focus the electron beam onto the positron target. Positrons produced from the positron target will be collected by the second quadruple triplet that will be optimized to collect positrons. The first dipole magnet bends the positrons/electrons, depending on the magnet polarity, by 45 degrees towards the second dipole magnet. The second dipole will bend the beam another 45 degrees, thus completing a 90 degree bend. A third quadruple triplet will focus the e-/e+ beam, as users desire. All beam elements are described in Table~\ref{tab:new-hrrl-line-elements}.


%\begin{figure*}[htbp] \begin{sidewaysfigure*}[htbp]

\centering %\includegraphics[scale=0.28]{HRRL_Pos_and_Ele_Go} \includegraphics[scale=0.35]{HRRL_Pos_and_Ele_Go.eps} \caption{The new HRRL beamline cofiguration for positron generation.} \label{fig:HRRL-e+-line} \end{sidewaysfigure*}

%\end{figure*}


\begin{table}[hbt] 

  \centering
  \caption{The new HRRL positron beamline elements.}
  \begin{tabular}{lccc}
      \toprule
        Item   &  Description \\
      \midrule
        T1    & Positron target \\
      \midrule
        T2    &  Annihilation target \\
       \midrule
        EnS    & Energy Slit  \\
       \midrule
        FC1, FC2& Faraday Cups \\
       \midrule
        Q1,...Q10	     & Quadrupoles \\
       \midrule
         D1, D2	    & Dipoles \\
       \midrule
        NaI     &  NaI Detecotrs \\
       \midrule
        OTR     &  Optical Transition Radiaiton screen\\
       \midrule
        YAG    & Yttrium Aluminium Garnet screen\\
 \bottomrule

\end{tabular} \label{tab:new-hrrl-line-elements} \end{table}

%00000000000000000000000000000000000000000000000000000000000 \section{Preparation for the Positron \\ Production Experiment} \subsection{HRRL Emittance measurements} \indent


Emittance, a key parameter in accelerator physics, is used to quantify the quality of an electron beam produced by an accelerator. The beam size and divergence at any point in the beamline can be described using emittance and Twiss parameters.

An Optical Transition Radiation (OTR) based viewer was installed to allow measurements at the high electron currents available from 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 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 distribution.

The emittance of the HRRL was measured to be less than 0.4~$\mu$m using the OTR based tool at an energy of 15~MeV. The details of this emittance measurement using the quadrupole scanning method were described in the IPAC12 proceedings~\cite{setiniyaz-q-scan}. The results are summarized in Table~\ref{results}.

\begin{table}[hbt] 

  \centering
  \caption{Emittance Measurement Results.}
  \begin{tabular}{lcc}
      \toprule
       {Parameter}         & {Unit}     &    {Value}    \\
      \midrule
        projected emittance $\epsilon_x$        &   $\mu$m    &    $0.37 \pm 0.02$     \\
         projected emittance $\epsilon_y$            &   $\mu$m    &    $0.30 \pm 0.04$     \\

% 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 & $8.06 \pm 1.1$ \\ 

        $\beta_x$-function                            &  m                           &   $1.40  \pm  0.06$          \\
        $\beta_y$-function                                &  m                           &   $1.17   \pm 0.13$         \\

$\alpha_x$-function & rad & $0.97 \pm 0.06$ \\ $\alpha_y$-function & rad & $0.24 \pm 0.07$ \\ micro-pulse charge & pC & 11 \\ micro-pulse length & ps & 35 \\ energy of the beam $E$ & MeV & 15 $\pm$ 1.6 \\ relative energy spread $\Delta E/E$ & \% & 10.4 \\ 

 \bottomrule
  \end{tabular}
  \label{results}

\end{table}

\subsection{Positron Detection using NaI crystals} \indent

A tungsten target will be placed at the end of the 90 degree beamline to annihilate positrons. I want to use two NaI detectors to detect the 511~keV photons created when positrons annihilate. I acquired some NaI crystals from Idaho Accelerator Center (IAC). Since their original bases used a slow post-amplifier, I built new PMT bases. I modified the design of model PA-14 from Saint-Gobain Crystals \& Detectors Ltd. These detectors are tested, calibrated, and ready to be used for the measurement. Fig.~\ref{fig:IAC-dets} shows the crystals and the bases I built. Fig.~\ref{fig:IAC-dets-Co60-Na22-spec} shows the spectrum taken by the detector using button sources. %I expect by doing coincidence, the resolution of 511~keV peak in the spectrum will be improved.

\begin{figure}[htbp] \centering \includegraphics[scale=0.08]{IAC_NaI_Detectors} \caption{The NaI detector and base built.} \label{fig:IAC-dets} \end{figure}

\begin{figure}[htbp] \centering \includegraphics[scale=0.18]{Na22_Co60Spectrum_by_IAC_Detectors} \caption{Detector 3 calibrated Spectrum.} \label{fig:IAC-dets-Co60-Na22-spec} \end{figure}

%\subsection{Positron Target Installation} %\indent % %A step motor is ready to be installed once the vacuum chamber is ready. The step motor, shown in the Fig.~\ref{fig:step-motor}, will hold 8 tungsten targets. % %\begin{figure}[htbp] %\centering %\includegraphics[scale=0.08]{setep_motor} %\caption{Step motor for holding W targets.} %\label{fig:step-motor} %\end{figure}

\section{Future Plan} \indent

We want to produce positrons using the HRRL beam line. We can improve positron collection efficiency by applying following methods:

1. By using a quadrupole triplet before tungsten a target, we will have control over the beam size and divergence at the target.

2. Cryogenically cooled converter will be installed, and these targets will be able to take on more beam power and increase positron yield.

3. Positrons will be collected by the quadrupole triplet system, which will improve collection efficiency.

4. Simulations will optimize beam elements for positron collection.

%\bibliographystyle{unsrt} % Order by citation %\bibliography{report}

\begin{thebibliography}{9} %{stancari} %@techreport{stancari, % title =Template:Stancari's proposal-------, % month ={Nov.}, % year = {2005}, % author ={J. Stancari}, % address ={Frascati, Italy}, % number ={}, % institution ={DAFNE Technical Note} \bibitem{stancari} 

G. Stancari and T. Forest "Design of a new beamline for electrons, positrons and photons at the HRRL lab", Pocatello, ID, USA (2009).


%@techreport{OTR, % title =Template:Optical Transition Radiation, % month ={}, % year = {1992}, % author ={B. Gitter}, % address ={Los Angeles, CA 90024}, % institution ={Particle Beam Physics Lab, Center for Advanced Accelerators, UCLA Department of Physics} %}

\bibitem{OTR} B. Gitter, Tech. Rep., Los Angeles, USA (1992).

%\bibitem{setiniyaz-q-scan} %@InProceedings{setiniyaz-q-scan, % author = {S. Setiniyaz, K. Chouffani, T. Forest, and Y. Kim}, % title = {TRANSVERSE BEAM EMITTANCE MEASUREMENTS OF A 16 MeV LINAC AT THE IDAHO ACCELERATOR CENTER}, % booktitle = {IPAC2012},%pages = {151--158}, % year = 2012, % address = {New Orleans, USA} %} \bibitem{setiniyaz-q-scan} S. Setiniyaz, K. Chouffani, T. Forest, and Y. Kim, in $Proc$. $IPAC2012$, New Orleans, USA.

%\bibitem{emit-mat} %C.F. Eckman $et$ $al$., in $Proc$. $IPAC2012$, New Orleans, USA.


\end{thebibliography}

\end{document}

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