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version 1.1, 2005/05/12 14:22:53
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version 1.1.2.1, 2005/05/12 14:22:53
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\documentclass{chowto} |
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\title{Enge Magnet} |
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\howtotype{expert} |
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\experiment{HKS} |
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\author{Liguang Tang} |
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\category{magnet} |
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%\maintainer{Name of person maintaining document} % Optional |
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\date{March 18, 2005} |
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\begin{document} |
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\begin{abstract} |
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This Howto outlines the purpose of the Enge magnet and its operation and |
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monitor. |
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\end{abstract} |
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\section {Purpose and Optics} |
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The Enge Split-Pole magnet is used behind and combined with the Splitter magnet |
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as the electron spectrometer which analyzes the electron's momentum and scattering |
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angle. The momentum and angular reconstructions are done using the measured |
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focal plane parameters, reconstruction matrices, and defined target point target |
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X position. |
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The central momentum is $316$ MeV/c with a bite of about $\pm30\%$. The solid angle |
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acceptance is about 9 msr in average. Due to the non-negligible momentum |
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dispersion from the front Splitter magnet and extremely small scattering angle, the |
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total virtual photon flux is obtained by more precise integrals over momentum bite |
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and angle rather than simply using this average acceptance. |
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At a location between the Splitter and Enge Split-Pole, the Enge magnet is tilted |
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by rotate about X-axis and followed by a shift along Y-axis. This arrangement |
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effects as rotating at the virtual target position then shifting this point off the Splitter |
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middle plane. By doing this, the spectrometer remains detecting small forward angle |
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scattered electrons but just avoid the high rate bramstrahlung and Moller electrons. |
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Such tilt does not effect the resolution but symmetry in acceptance. |
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\section {Setting the magnet} |
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Since this magnet is not directly effect the beam, thus it will be controlled and operated |
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by Hall C experimentalists. However, due to fringe field does have slight effect to beam |
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and other magnets nearby, such as Splitter and HKS Q1, it is preferred to turn off the |
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beam during the process of setting up the magnet. Since this magnet is sharing the |
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same power supply with Moller magnet, existing control will be used in setting up the |
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magnet by referring to steps of ``Getting started'' and ``Setting the magnets'' in ``How to |
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set the SOS magnets'' in Hall C online Howto document. Since no polarity change in |
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operating this magnet for hypernuclear experiment, step of ``Degaussing'' is not Needed. |
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\section {Monitor} |
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The field is monitored directly by a hall probe. The stability should be controlled within |
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an error of $\pm 10^{-4}$ or $\pm 1.5$ gauss. |
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\end{document} |
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% Revision History: |
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% $Log$ |
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% Revision 1.1.2.1 2005/05/12 14:22:53 saw |
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% Initial version |
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% |
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