Testing the k100sim for automatic PuBe gammas

Testing the k100sim for automatic PuBe gammas

Anthony's default k100sim code will throw a spectrum of gammas corresponding to the gammas expected from the PuBe source (with several-MeV energies) with every event. Previously I commented out lines in the code to prevent this. But there's a command you can add to a macro to turn them off:

/CDMS/PuBe/doPuBeGammas false

Here are some tests to make sure that this works. I ran three sims. In each of them the macro shoots a beam of 100keV particles at the detector. I did three versions: 1) gamma beam without turning off PuBe gammas 2) gamma beam with PuBe gammas turned off and 3) neutron beam with PuBe gammas turned off.

Deposited energy spectrum

Test 1

When the PuBe gammas are not explicitly turned off, we see energy depositions up to several MeV

Test 2

With the PuBe gammas turned off, we see only 100keV events deposited in the detector (same spectrum shown above in two ranges)

Test 3

With PuBe gammas off and throwing 100keV neutrons, we see mostly events below 100keV (neutron scatters), but also some high-energy events. I guessed these were neutron captures with high-energy gammas after capture. The spectrum on the right removes all events with neutron capture and we see it's all low energy events.

Parent particle energy spectrum

Test 1

When the PuBe gammas are not explicitly turned off, the first recorded kinetic energy of the parent shows a peak around 9.5 MeV (this are probably the initial energy of those parents). On the right is a zoom showing we also have a peak at 100 keV from the gammas thrown by the macro.

Test 2

With the PuBe gammas turned off, the parent particle never has energies above 100 keV.

Test 2

Also when throwing neutrons, when the PuBe gammas are off we never see parent energies above 100 keV.

Parent type

There was some question as to whether the default behavior of the sim would change the identity of particles thrown in the macro to gammas. Here we look at parent identities.

Test 1

Here PuBe gammas have not been turned off and the macro throws gammas. All parents are gammas (type 22).

Test 2

Here PuBe gammas are turned off and the macro throws gammas. All parents are gammas (type 22).

Test 3

Here PuBe gammas are turned off and the macro throws neutrons. All parents are neutrons (type 2112).

Test 4

Here is one additional test: PuBe gammas not turned off, macro throws neutrons. We see that some parents are neutrons, some are gammas.

Also for Test 4 (macro throws neutrons and PuBe gammas not turned off), the lines below show that every event contains both parent neutrons and parent gammas:

root [3] simtree->GetEntries("Sum$(Type==22&&P==0)")
(Long64_t)1000
root [4] simtree->GetEntries("Sum$(Type==2112&&P==0)")
(Long64_t)1000
root [5] simtree->GetEntries("Sum$(Type==2112&&P==0)&&Sum$(Type==22&&P==0)")
(Long64_t)1000

This actually says something more: that the PuBe gammas must be thrown from the same place and with the same angular distribution as the source in the macro. Above we see that every PuBe gamma reaches the detector, so clearly they are not being thrown isotropically.

Conclusion

The PuBe gammas in the code seem to work the way they should. They don't change the energy or identity of particles thrown by the macro itself. PuBe gammas are thrown along with every event in the macro, if they are left on. If PuBe gammas are explicitly turned off the code has no effect on particles thrown by the macro.

Macro

Here's the macro used