Difference between revisions of "Sadiq Proposal Defense"

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= Abstract =
+
[[File:sadiq_proposal.pdf]]
  
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We are constructing a achromatic positron source in the Beam Lab of Department of Physics at Idaho State University. We have studied the radiation impact of moving the cavity to new location, with GEANT4 simulation and experiment. Our conclusion was it was safe to do so. We Constructed new beamline, performed emittance measurements, and we calculated emittance and twiss parameters.
 
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We acquired 4 NaI crystals from Idaho Accelerator Center (IAC). We built our own PMT bases for them by modifying one the design. NaI detectors with new base are tested and they worked properly.
 
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A tungsten target will be placed in a chamber between 1st and 2nd triplet. The dipole magnet was remapped for emittance test with energy scan.
 
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We are expecting to collect positrons and transport them down the second positron annihilation target at the end of the 90 degree beamline. Two NaI detectors in opposite side will detect 511 keV photons created from annihilations, which will tell us the efficiency of the positron generation.
 
  
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= Introduction =
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= text =
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%% The comment character in TeX / LaTeX is the percent character.
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%% The following chunk is called the header
  
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We want to measure the efficiency of producing positrons using the High Repetition Rate Linac (HRRL) located at the Beam Lab of the Physics Department, at Idaho State University (ISU). HRRL S-band electron linear accelerator, with max beam energy of 16 MeV, max peak current of 80 mA, max repetition rate of 1 kHz, and max pulse length of 250 ns (FWHM).
+
\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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The Beam Lab is, located in the basement of the physics department, divided into two parts by a L-shaped cement wall. The accelerator cell houses the cavity and magntic elements needed to transport electrons. The experimental cell is located in an adjacent room to the accelerator cell. Previously cavity was located at the center of the accelerator cell. To adapt positron project, it was relocated closer the walls, which allow us to add more dipole and quadrupole magnets.
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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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\usepackage{graphicx}
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\usepackage{amstext}
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%\usepackage{hyperref}
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%\usepackage[bottom]{footmisc}
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%\usepackage{tabularx }
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%\usepackage{footnote}
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%\usepackage{caption}
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%\usepackage{subcaption}
  
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In the new beanline, the electron beam comes out of HRRL cavity will pass through first set of quadruple triplet magnets, which is going to focus electron beam on the positron target. Positrons created in the target will be collected by second set of quadruple triplet, then will be bent 45 degree by first dipole magnet. We want to insert or removed positron target from beamline, so that we can run in positron or electron dual mode. Accordingly, we will change the polarity of the dipoles to run on e-/e+ modes. The The second dipole will bend beam another 45 degree, thus complete total of 90 degree bend. Third set of quadruple triplet will be used create desired e-/e+ beam profile sutable for users' need.
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%\usepackage{epsfig}
  
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\tolerance=1 % no hyphenation, no zig-zag line.
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\emergencystretch=\maxdimen % no hyphenation, no zig-zag line.
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\hyphenpenalty=10000 % no hyphenation, no zig-zag line.
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\hbadness=10000 % no hyphenation, no zig-zag line.
  
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[[Image:BeamLine_Yim_10-14-10.png| 800 px |thumb | Fig. HRRL beamline for positron generation.]]
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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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This is the setup and apparatus we want run for positron creation and collection for the future.
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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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| EnS || Energy Slit
 
−
|-
 
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| F1, F2, F3 || Flang
 
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|-
 
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| FC1, FC2  || Faraday Cup
 
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|-
 
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| Q1,...Q10 || Quadrupole
 
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|-
 
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| D1, D2 || Dipole
 
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|-
 
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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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|}
 
  
 +
%\usepackage{lipsum}% http://ctan.org/pkg/lipsum
 +
%\usepackage[demo]{graphicx}% http://ctan.org/pkg/graphicx
  
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Earlier measurements were conducted at Idaho Accelerator Center of ISU, May of 2008. Setup are shown in figure below. 511 keV photons from annihilation were detected.
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{| border="1" cellpadding="4"
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\oddsidemargin -0.25in % Left margin is 1in + this value
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|-
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\textwidth 6.75in % Right margin is not set explicitly
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|Item || Description
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%\topmargin 0in % Top margin is 1in + this value
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|-
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\topmargin -1in % Top margin is 0in + this value
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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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\textheight 9in % Bottom margin is not set explicitly
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|-
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\columnsep 0.25in % separation between columns
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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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%\setlength{\parindent}{15pt}  
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|-
 
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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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|NaI detector||
 
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|}
 
  
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{| border="1" cellpadding="4"
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%% Define a macro for inserting postscript images
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|-
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%% ==============================================
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|[[Image:Example.jpg | 200 px |thumb|Fig. Setup for 2009 run.]] || [[Image:Run60_HpGe-NaI.gif | 200 px |thumb|Fig. Spectrum from HpGe Detector and NaI detecotrs.]] || [[Image:PositronYield_SweeperMagnet_run60-61.gif | 200 px |thumb|Fig. ]]
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%% This is a macro which nominally takes 3 parameters,
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|}
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%% it would be used as follows to insert and encapsulated postscript
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%% image at the location where it is used.
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%% \EPSFIG{epsfilename}{caption}{label}
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%% - epsfilename is the name of the encapsulated postscript file to be
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%%              inserted at this location
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%% - caption is the text to be shown as the figure caption, it will be
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%%          prepended by Figure X. The number X can be referenced
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%%          using the label parameter.
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%% - label is a name given to the figure, it can be referenced using the
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%%        \ref{label} command.
  
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=Experiments=
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\def\EPSFIG[#1]#2#3#4{ % Don't be scared by this monsrosity
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\begin{figure}[H] % it is a macro to save typing later
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\begin{center} %
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\includegraphics[#1]{#2} %
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\end{center} %
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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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== HRRL Emittance measurements ==
 
  
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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.
+
%% Define the fields to be displayed by a \maketitle command
  
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=== What is Emittance ===
+
\author{Sadiq Setiniyaz (Shadike Saitiniyazi)\thanks{Email: sadik82@gmail.com}}
−
[[image:sadiq_phd_emittance_phase_space_ellipse.png | 200 px |thumb |Fig.1 Phase space ellipse <ref name="MConte08"></ref>.]]
+
%{address={Department of Physics, Idaho State University}}
 +
\title{PROPOSAL FOR POSITRON PRODUCTION EFFICIENCY STUDY USING HIGH REPETITION RATE LINAC AT IAC}
  
−
In accelerator physics, Cartesian coordinate system was used to describe motion of the accelerated particles. Usually the z-axis of Cartesian coordinate system is set to be along the electron beam line as longitudinal beam direction. X-axis is set to be horizontal and perpendicular to the longitudinal direction, as one of the transverse beam direction. Y-axis is set to be vertical and perpendicular to the longitudinal direction, as another transverse beam direction.
+
%%
 +
%% Header now finished
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%%
  
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For the convenience of representation, we use <math>z</math> to represent our transverse coordinates, while discussing emittance. And we would like to express longitudinal beam direction with <math>s</math>. Our transverse beam profile changes along the beam line, it makes <math>z</math> is function of <math>s</math>, <math>z~(s)</math>. The angle of a accelerated charge regarding the designed orbit can be defined as:
+
\begin{document} % Critical
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\twocolumn
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\thispagestyle{empty} % Inhibit the page number on this page
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\maketitle % Use the \author, \title and \date info
  
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<math>z'=\frac{dz}{ds}</math>
+
%% Next comes the abstract, notice the curly-braces surrounding the
 +
%% text.
  
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If we plot <math>z</math> vs. <math>z'</math>, we will get an ellipse. The area of the ellipse is an invariant, which is called Courant-Snyder invariant. The transverse emittance <math>\epsilon</math> of the beam is defined to be the area of the ellipse, which contains 90% of the particles <ref name="MConte08"> M. Conte and W. W. MacKay, “An Introduction To The Physics Of Particle Accelera
+
\abstract{
−
tors”, World Scientifc, Singapore, 2008, 2nd Edition, pp. 257-330. </ref>.
+
\indent
  
−
By changing quadrupole magnetic field strength <math>k</math>, we can change beam sizes <math>\sigma_{x,y}</math> on the screen. We make projection to the x, y axes, then fit them with Gaussian fittings to extract rms beam sizes, then plot vs <math>\sigma_{x,y}</math> vs <math>k_{1}L</math>. By Fitting a parabola we can find constants
+
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.}
−
<math>A</math>,<math>B</math>, and <math>C</math>, and get emittances.
 
  
−
===Emittance Measurement Using a YaG crystal ===
+
\section{Introduction}
−
In July 2010y, Emittance measurement of HRRL was conducted at Beam Lab, at Physics Department of ISU. We installed a YAG crystal on the HRRL beam line to see electron beam. A quadrupole magnet was installed between HRRL gun and the YAG screen. We changed current on the quadrupole to control magnetic field strength of the quadrupole magnet, thus we changed electron beam shape on the YAG screen.
+
\indent
  
−
==== Experimental Setup ====
+
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.
  
−
We did quadrupole scan to measure emittance of the electron beam in HRRL. In quadrupole scan method, the strength of the quadrupole magnet was changed by changing the current go through quadrupole coils. The electron beam were coming out of the gun went through quadrupole, then beam would enter a 3-way cross. Two end of the 3-way cross was installed on the beam line. The third end of the 3-way cross was placed upward and there was a actuator installed to it.  The YAG crystal was mounted in the actuator, which can put the YAG in the beam line or take it out of the beam line. A camera was placed inside the actuator to look through vacuum a window and to capture the image on the YAG crystal created by electron beam. A Faraday cup was mounted at the end of the beam line to measure the transmission of the charge.
+
\section{Previous Measurements}
 +
\indent
  
−
Setup and beam line and are shown in figures 1.2 and 1.3:
+
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.
  
−
{| border="0" style="background:transparent;"  align="center"
 
−
|-
 
−
|
 
−
[[image:sadiq_phd_emittance_HRRL_July_Emit_Lay_Out.png | 470 px |thumb|Fig.2 Experiment set up of HRRL 2010 July emittance test.]]
 
−
|
 
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[[image:Constructed Beam Line for Emittance Test 1.jpg | 300 px |thumb|Fig.3 Beam Line of HRRL 2010 July emittance test.]]
 
−
|}
 
  
 +
\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}
  
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Figures 4, 5, and 6 show Faraday cup, Quadrupole Magnet, and YAG Chrystal used in the test:
+
\begin{table}[htbp]
 +
\caption{Beamline elements for positron production at IAC in 2008.}
  
−
{| border="0" style="background:transparent;" align="center"
+
\begin{tabular}{ll}
−
|-
+
\hline
−
|
+
      \textbf{Item} & {$\textbf {Description}$} \\
−
[[image:Beam_Line_Parts_HRRL_Emittance_Test_FC.jpg | 280 px |thumb|Fig.4 Faraday cup used for HRRL 2010 July emittance test.]]
+
\hline
−
|
+
          Tantalum foil  & 6 mm thick 20 mm x 20 mm area  \\
−
[[image:Beam_Line_Parts_HRRL_Emittance_Test_QuadT1.jpg | 200 px |thumb|Fig.5 Quadrupole Magnet used for HRRL 2010 July emittance test.]]
+
          Tungsten foil  &  2 mm thick 20 mm x 20 mm area    \\
−
|
+
          Phosphorus flag  & 1 mil aluminum backing            \\
−
[[image:Beam_Line_Parts_HRRL_Emittance_Test_YAG.jpg | 240 px |thumb|Fig.6 YAG Christal used for HRRL 2010 July emittance test.]]
+
          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}
  
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Emittance measurement was carried out on HRRL on July of 2010 under the experimental setup discussed in previous section. In this measurement we used analog camera to take images.
 
  
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When relativistic electron beam pass through YAG target, Opitcal Transition Radiation (OTR) is produced. OTR are taken for different quadrupole coil current (0-20 A).
+
\section{Proposed Beamline}
 +
\indent
  
  
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{|  border="0" style="background:transparent;"  align="center"
+
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}.
−
|-
 
−
| [[image:HRRL_Emit_test_Quad_Scan_First_0Amp.jpg | 300 px |thumb|Fig. OTR image of 0 Amp quadrupole coil current.]] ||[[image:HRRL_Emit_test_Quad_Scan_First_5Amp.jpg | 300 px |thumb|Fig. OTR image of 5 Amp quadrupole coil current.]] ||[[image:HRRL_Emit_test_Quad_Scan_First_10Amp.jpg | 300 px |thumb|Fig. OTR image of 10 Amp quadrupole coil current.]]
 
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|-
 
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|[[image:HRRL_Emit_test_Quad_Scan_First_15Amp.jpg | 300 px |thumb|Fig. OTR image of 15 Amp quadrupole coil current.]] ||[[image:HRRL_Emit_test_Quad_Scan_First_20Amp.jpg | 300 px |thumb|Fig. OTR image of 20 Amp quadrupole coil current.]] ||
 
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[[image:HRRL_Emit_test_Quad_Scan_Second_10Amp_2.jpg | 300 px |thumb|Fig. OTR image of -10 Amp quadrupole coil current.]]
 
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|}
 
  
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==== Data Analysis ====
+
\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}
  
−
[[image:Fit_Rotated_HRRL_Emit_test_Quad_Scan_Second_2Amp.jpg |thumb | 300 px |thumb|Fig. Gaussian fits for OTR images.]]
+
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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In the mages we can see a bright spot at the center. This spot did not change by changing quad coil current. So, this is image of hot filament. The bigger spot at the right side of the filament was changing by changing quad coil current, hence it is OTR. We also see 10 mm circle mounted on the OTR target, as well as beam hallow.
+
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}.
  
−
We did Guassian fits to beam image to extract x, y RMS values for different quad currents. We discovered that the camera was rotated slightly. To compensate for images were rotated, so that we have beam image upright. To reduce back ground, we just focused on OTR beam image and took out the filament spot from data, as shown in image below.
 
  
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==== Results ====
 
  
−
{| border="0" style="background:transparent;"  align="center"
+
%\begin{figure*}[htbp]
−
|-
+
\begin{sidewaysfigure*}[htbp]
−
|
 
−
[[image:HRRL_Emitt_2010_Jul_Refit_After_Correcting_Calibration_Projection_X.png | 300 px |thumb|Fig. Square of RMS beam size <math> \sigma_x^2 </math> vs. quad strength times quad pole length <math> k_1L </math> for x projection of electron beam profile ]]
 
−
|
 
−
[[image:HRRL_Emitt_2010_Jul_Refit_After_Correcting_Calibration_Projection_Y.png | 300 px |thumb|Fig. Square of RMS beam size <math> \sigma_x^2 </math> vs. quad strength times quad pole length <math> k_1L </math> for y projection of electron beam profile ]]
 
−
|}
 
  
 +
\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*}
  
−
<math> \sigma_x^2= (8.05  \pm 0.25) + (4.18 \pm 0.19)k_1L + (0.64 \pm 0.034)(k_1L)^2 </math>
+
%\end{figure*}
  
−
<math> \epsilon_x = 2.2 \pm 1.3~mm*mrad ~\Rightarrow~ \epsilon_{n,x} = 42.4 \pm 25.4~mm*mrad</math>
 
  
−
<math> \beta_x=0.72 \pm 0.31, \alpha_x=-1.23 \pm 0.56 </math>
 
  
 +
\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}
  
−
<math>\sigma_y^2 = (8.52 \pm 0.40) + (-3.88 \pm 0.28)k_1L + (0.57 \pm 0.048)(k_1L)^2 </math>
+
%00000000000000000000000000000000000000000000000000000000000
 +
\section{Preparation for the Positron \\ Production Experiment}
 +
\subsection{HRRL Emittance measurements}
 +
\indent
  
−
<math> \epsilon_y = 2.6 \pm 2.0~mm*mrad  ~\Rightarrow~  \epsilon_{n,y} = 50.5 \pm 38.3~mm*mrad</math>
 
  
−
<math> \beta_y=0.54 \pm 0.22, \alpha_y=2.68 \pm 1.13 </math>
+
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.  
  
−
=== Emittance Measurements with an OTR ===
+
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.
  
−
During first emittance measurement, we see our electron beam image at YAG crystal is much bigger than expected. Comparison study shows that for same beam YAG screen shows bigger beam size than Optical Transition Radiation (OTR) screen. Yag is good for low charge beam. Electron beam from HRRL has a big charge in a single pulse and beam size is big.  
+
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}.
  
−
We did out second emittance measurement with 10 <math>\mu m</math> thick aluminium OTR screen. We also improved our optical imaging system by using better digital camera that can be triggered by the same pulse trigger electron gun and also by using three 2 inch diameter lenses to focus the lights from OTR to the CCD of the camera.  
+
\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}
  
−
==== Experimental Setup ====
+
\subsection{Positron Detection using NaI crystals}
 +
\indent
  
−
[[image:hrrl_2011_mar_emit_test_quad_scan_quad.png |thumb | 400 px |thumb|Fig. Simplified setup configuration for HRRL beamline at 2011 March measurement.]]
+
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.
  
−
The cavity was moved the new location and beam line was built by the design of Dr. Yujong Kim, as shown in figure
+
\begin{figure}[htbp]
 +
\centering
 +
\includegraphics[scale=0.08]{IAC_NaI_Detectors}
 +
\caption{The NaI detector and base built.}
 +
\label{fig:IAC-dets}
 +
\end{figure}
  
−
Experimental setup is shown in the following 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}
  
−
We chose one of the quad at a time to do the scan and turned off all the other quads. Optical transition radiation was observed at OTR target. At the end of 0 degree beamline we have a Faraday cup to measure the charge of the beam. Camera cage system was located below the OTR target. There are 3 lenses used to focus lights from target to the CCD camera. Target can be pushed into or taken out of the beamline by the actuator at the top.
+
%\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}
  
−
We chose one of the quad at a time to do the scan and turned off all the other quads. Optical transition radiation was observed at OTR target. At the end of 0 degree beamline we also have a Faraday cup to measure the charge of the beam.
+
\section{Future Plan}
 +
\indent
  
−
OTR Target can be pushed into or taken out of the beamline vertically by the actuator at the top, which is attached to the 6-way cross. This actuator controlled remotely at the control desk.  
+
We want to produce positrons using the HRRL beam line. We can improve positron collection efficiency by applying following methods:
  
−
Camera cage system was located below the OTR target. Cage system attached to the bottom of the 6-way cross, and where there is a transparent window. There are 3 lenses used to focus lights from target to the CCD camera. They have focal length of 100 mm, 500 mm, and 50 mm.  
+
1. By using a quadrupole triplet before tungsten a target, we will have control over the beam size and divergence at the target.
  
−
The lens closest to the OTR target is 10 cm away from the target, an it has 100 mm focal length. This lens was located as close to the target as possible, so that we might collect as much OTR light as possible, and it was thus called collector lens. The lens in the middle has focal length of 500 mm. Moving this lens will change total focal length in a small amount, and this allow us to do fine tuning. Thus, we called this lens fine tuning lens. The last lens, which is furthest from target, and closed to the CCD camera has the shortest focal length of 5o mm. Its short focal length allow us to focus the light on the very small sensing area of the CCD camera.  
+
2. Cryogenically cooled converter will be installed, and these targets will be able to take on more beam power and increase positron yield.
  
−
{| border="0" style="background:transparent;"  align="center"
+
3. Positrons will be collected by the quadrupole triplet system, which will improve collection efficiency.
−
|-
 
−
| [[image: HRRL_Mar_Emit_lay_Out_Camera.png  | 500 px |thumb|Fig. HRRL beamline: Optical cage system to focus OTR lights on CCD camera.]]
 
−
| [[image: HRRL_Mar_Emit_lay_Out_Camera_2.png| 500 px |thumb|Fig. HRRL beamline: Optical lenses lay out for optical cage system.]]
 
−
|-
 
−
|}
 
  
−
==== Experiment with OTR ====
+
4. Simulations will optimize beam elements for positron collection.
  
−
Optical Transition Radiation (OTR): Transition radiation is emitted when a charge moving at a constant velocity cross a boundary between two materials with different dielectric constant.
+
%\bibliographystyle{unsrt} % Order by citation
 +
%\bibliography{report}
  
−
Emittance measurement was carried out on HRRL on March of 2011 under the experimental setup discussed in previous section. In this measurement we used JAI digital camera.  
+
\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).
  
−
When relativistic electron beam pass through Aluminum target OTR is produced. OTR are taken for different quadrupole coil currents.
 
  
−
{|  border="0" style="background:transparent;"  align="center"
+
%@techreport{OTR,
−
|-
+
% title      ={{Optical Transition Radiation}},
−
|[[File:OTR_Q1Scan03182011_10.png | 300 px |thumb|Fig. OTR image of 0 Amp Q1 coil current.]] ||[[File:OTR_Q1Scan03182011_15.png | 300 px |thumb|Fig. OTR image of +1 Amp Q1 coil current.]] ||
+
% month      ={},
−
[[File:OTR_Q1Scan03182011_20.png | 300 px |thumb|Fig. OTR image of +2 Amp Q1 coil current.]]
+
% year = {1992},
−
|}
+
% author      ={B. Gitter},
 +
% address    ={Los Angeles, CA 90024},
 +
% institution ={Particle Beam Physics Lab, Center for Advanced Accelerators, UCLA Department of Physics}
 +
%}
  
−
==== Data Analysis and Results====
+
\bibitem{OTR}
 +
B. Gitter, Tech. Rep., Los Angeles, USA (1992).
  
−
The projection of the beam is not Gaussian distribution. So, we fit Super Gaussian fitting <ref name="BeamDisBeyondRMS"> F.-J Decker, “Beam Distributions Beyond RMS”, BIW94, Vancouver,CA,Sep 1994, . </ref>.
+
%\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.
  
−
We used the MATLAB to analyze the data. The results shows that:
+
%\bibitem{emit-mat}
 +
%C.F. Eckman $et$ $al$., in $Proc$. $IPAC2012$, New Orleans, USA.
  
−
<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>
 
  
−
<math> \epsilon_x = 0.417 \pm 0.023~mm*mrad ~\Rightarrow~ \epsilon_{n,x} = 11.43 \pm 0.64~mm*mrad</math>
+
\end{thebibliography}
  
−
<math> \beta_x=1.385 \pm 0.065, \alpha_x=0.97 \pm 0.07 </math>
+
\end{document}
−
 
 
−
<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>
 
−
 
 
−
<math> \beta_y=1.17 \pm 0.19, \alpha_y=0.22 \pm 0.10 </math>
 
−
 
 
−
==Beamline parameters for optimal positron production using the measured emmittance==
 
−
 
 
−
 
 
−
 
 
−
= Positron Detection using NaI crystal =
 
−
 
 
−
[[File:HRRL_Positron_Our_Modified_PMT_Base_Design.png |thumb | 350 px | Fig. NaI detector base circuit.]]
 
−
 
 
−
 
 
−
To detect positrons created, we want a put Tungsten target at the end of 90 degree beamline. When positrons hit W-target, 511 keV photons will be created. We want to use NaI detectors to detect these 511 keV photons, so we might have an estimate on the numbers of the positrons we collect at the end of the 90 degree beamline.
 
−
 
 
−
We acquired some NaI crystals from Idaho Accelerator Center (IAC). We built our own PMT bases for them, since the bases we had not working properly. We modified the design of model PA-14 from Saint-Gobain crystals & detectors ltd. Following image is the design.
 
−
 
 
−
[[File:IAC_NaI_Detectors_and_Parts_7.png | 450 px | Fig. The NaI detector and base built.]]
 
−
 
 
−
[[File:Hrrl_pos_det_calb_det3_r2637_r2636_2.png | 450 px|Fig. Detector 3 calibrated Spectrum.]]
 
−
 
 
−
Even though now the 511 keV peak seems to be very wide and our resolution is low, we are expecting to improve these by doing coincidence in the future experiments.
 
−
 
 
−
= Future Plan =
 
−
 
 
−
== Positron Target ==
 
−
 
 
−
A tungsten target will be placed in the space between 1st and 2nd triplet. The tungsten target will be placed inside a big chamber.
 
−
 
 
−
We are going to run
 
−
 
 
−
== Emittance Tests with Energy Scan ==
 
−
 
 
−
We will do emittance test with precise energy scan. We remapped dipole magnet for more precise energy scan. This will also improve our emittance measurement. 
 
−
 
 
−
== Positron Yield ==
 
−
 
 
−
We will insert the first tungsten target and create positrons. We are 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 we want to detect them by our NaI detectors.
 
−
 
 
−
= References =
 
−
 
 
−
<references/>
 
−
 
 
−
 
 
−
 
 
−
 
 
−
[[File:Emittance.tex]]
 

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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