ELOG S1287

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S1287

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Fri Nov 16 07:12:32 2012

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I have sorted the 4.11MeV/u data runs (the ones which had the common stop mode on the TDCs) and applied the following cuts:
<ol>
 <li>There must be a hit registered in each side of the detectors.</li>
 <li>equal energy must be deposited in both sides of the detectors.</li>
 <li>Low energy cut is applied to each detector.</li>
 <li>Must have a hit in the TDC for the front strips.</li>
 <li>Must have multiplicity greater than 3.</li>
 <li>Must have hits in both S2-1 and S2-2.</li>
 <li>Particles must hit at 180 degrees to in the detectors. (back spoke cut)</li>
</ol>
Looking at the back spoke in S2-1 vs back spoke in S2-2 plot cut number 7 should be changed to +/- 3 back strips to ensure no particles are being cut out due to position straggling in the gas.
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Plotting S2-2 energy vs time with these cuts gives attachment 1. I need to redo the timing calibration for S2-2 as strip 96 has the wrong offset and the resolution needs to be improved. The protons can be seen clearly as they punch through the detector and around 8MeV. I have also attached as attachment 2 the monte carlo plot for S2-2 at this energy. There are two monte carlo codes one for 21Ne beam scattering and one for the reaction which means the number of each type of event are not correctly proportional, in the data there is far more scattering. Here you can see the protons from ~4-8MeV lying underneath the alpha line.&nbsp;The time spread in the actual data of the proton/alpha line is about 25ns whereas in the monte carlo it is about 10 ns for combined alpha and protons.&nbsp;
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Because the protons will punch through the detector at approx 8MeV I believe that the points after this could be alphas. Attachment 3 shows the projection for the polygon which selects particles after the protons in the energy vs time plot. As can be seen from the energy projection the energy dips where you would expect it to for alphas, however there are some higher energy points and I am not sure what these might be.
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I then plotted Energy vs time in S2-1 gating on energy in S2-2 greater than 8.2MeV. This plot is shown in attachment 6. Attachment 4 shows the Monte Carlo simulated energy vs time for 18F in S2-1, with attachment 5 shows simulated energy vs time for scattered 21Ne in S2-1. I plotted these separately as they have the similar timing and so cant be seen separately on the same plot. Here you can see the 21Ne clearly in the data, so some of the protons are depositing more than 8.2 MeV in S2-2. If I change the cut so that the energy in S2-2 must be greater than 9MeV and plot energy vs time for S2-1 again the 21Ne is no longer visible (will not let me attach this file due to capacity so I will attach it in a new elog entry straight after this one). The energy spread of the points in the S2-1 energy vs time plot cut on what could be alphas in S2-2 gives the correct energy spread for 18F in the monte carlo simulated data.
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Next:
<ul>
 <li>Redo timing calibration for S2-2</li>
 <li>Look at gas out run</li>
 <li>Work out how to separate lower energy alphas and protons</li>
 <li>Work out what higher energy points in S2-2 could be.</li>
</ul>
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