Orsay: srimulations and Ex + Jpi

In our last exciting episode, we learned about different detector configurations and how they affect our total detection efficiency. This time we'll learn about the energy resolution of the detectors. Can our intrepid hero(in)es see the effect of the extra level, or are they doomed to not be able to resolve it? Stay tuned.

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Srimulations:
beam in target:
double EStraggleEntrance = 0.2*targetLoss*random.nextGaussian()/2.35;
double angStraggleBeamEntrance = 0.03*random.nextGaussian()*xtarg/(100*2.35);
double ThetaBeam = Math.abs(0.03+angStraggleBeamEntrance);

¹⁸O in target: srimulated 8 MeV, since these are about the lowest energy produced in the relevant angular range
double EStraggleResidTarget = 0.04*residualTargetLoss*random.nextGaussian()/2.35;
thetaResidLab = thetaResidLab+0.7*random.nextGaussian()*xtarg/(100*2.35);

alpha in target: srimulated 10 and 1 MeV
double EStraggleTarget=0.33*a1TargetLoss*random.nextGaussian()/2.35;
thetaDlabPF1=thetaDlabPF1+0.12*random.nextGaussian()*xtarg/(100*2.35);

alpha in delta-E detector: srimulated 30,20,15,10 MeV in 60 um of Si
DELoss1 = DELossCalc.getThinEnergyLoss(projfrag,TflightPF1,PF1ThetaInc) *(0.001+0.00007*random.nextGaussian()/2.35);
double fwhm=0.5;
if (DELoss1>2.5) fwhm=DELoss1-2;
double angStraggleDE1=fwhm*random.nextGaussian()/2.35;

srimulated 7, 14, 30, 60 MeV 18O in dead layer of X2 detectors; in all cases, the energy loss fwhm was 0.08 MeV (!).

checked energy loss in various absorbers:

• the beam energy loss in the target looks the same in the simulation as in the SRIMulation.
  
• The dead layer parameters were copied from the E1031 sims.
  
• The alpha energy loss in the pad detector is the same at 20 MeV, but greater for lower energy. This is the dedx vs srim issue again. I don't know how to fix it properly...but it is important to have the right energy loss in the pad detectors, since we use the alpha energies to calculate the Q value.... How about this: for energies above 20 MeV, use the energy loss the simulation would normally calculate, but below 20 MeV use an energy dependent function...
  

(this is filler text to thwart the evil computer.)

double mod2=1;
if (TflightPF2<20) mod2=0.77+0.0115*TflightPF2; deloss2=0.001*mod2*DELossCalc.getThinEnergyLoss(projfrag,TflightPF2,PF2ThetaInc);
destrag2=0.055*DELoss2*random.nextGaussian()/2.35;

(this is filler text to thwart the evil computer.)

That energy dependence makes the simulation's result match SRIM's. all is well.

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Allowed Jpi values: Jpi selection rules



i.e. for small angular momentum transfers, 0+,1-,2+,... levels in ¹⁸O will be populated; same thing in ²²Ne (from reactions on 16O contaminant); and in ¹⁹O (from reactions on ¹³C contaminant) the 1/2-, 3/2+, 5/2-... levels will be populated.

The ¹⁸O level of interest (6.404 MeV) has Jpi=3-. The potential contaminant (6.351 MeV) is thought to have Jpi=2-. If this is the correct Jpi assignment, the level won't be populated--but the assignment might be incorrect so I'll simulate its effect anyway.

In ²²Ne, there are natural parity levels at:
Ex (MeV) Jpi
0 0+
1.275 2+
3.3577 4+
4.4558 2+
5.3632 2+
5.5237 4+
5.9101 3-
6.1201 2+
6.2343 0+
63103 6+
6.3465 4+
6.691 1-
6.8194 2+
6.9003 (0,1)+
7.0509 1-
7.3407 0+
7.3428 (3,4)+
7.4059 3-
7.469 ?
7.491 1-
7.6430 2+
7.722 3-
7.9226 (2)+
8.0764 (4)+
8.1343 2+
8.1618 2+,3,4+
8.3759 (3)-
8.452 ?
8.4887 2+
8.553 (1,2)+
8.573 ?
8.5960 2+
8.7400 (3)-
8.8549 4+
8.8990 ?
8.976 ?
9.045 2+,3-
9.097 1-
9.162 ?
9.1775 (4)+
9.229 2+
9.250 ?
9.324 ?
9.508 ?
9.541 2+
9.625 ?
9.652 ?
9.725 (3-)
9.842 (2+)

and in ¹⁹O, the natural parity levels are at
Ex (MeV) Jpi
0.0960 3/2+
2.7790 7/2+
3.0674 3/2+
3.2316 (1/2, 3/2-)
4.1093 3/2+
4.3281 3/2, 5/2
4.4025 3/2, 5/2, 7/2
4.9683 5/2, 7/2
5.0070 3/2, 5/2
5.0820 1/2-
5.1484 >=5/2+
5.3840 9/2, 11/2, 13/2
5.5035 ?
5.540 3/2+
5.7046 7/2-, 5/2
6.1196 3/2+
6.1916 ?
6.4058 ?
6.4662 7/2, 9/2, 11/2
6.583 ?
6.903 ?
6.988 ?