Progress and Outstanding Problems

1. Progress and Outstanding Problems Dennis Wright 6 April 2017

2. Outline • Progress • Updated and coordinated databases • Floating levels fully implemented • Correlated gammas implemented • Better integration with G4PhotonEvaporation • Outstanding problems • Irreproducibility returns • Biasing • Multithreading • Rare processes (double beta decay, etc.) • Publication

3. Databases • At lot of work done in this area – see Laurent’s talk • databases are now consistent with one another w.r.t. data • gamma correlation data included • Latest co-working set of databases • RadioactiveDecay5.1.1 • PhotonEvaporation4.3.2 • ENDFSTATE2.1 • agreed with Gabriele that fixes in DBs could be included with patches as long as numbering is clear  another decimal place

4. Floating Levels Fully Implemented • Floating Levels: nuclear energy levels which are known or expected to exist but whose energy is not known • Represented by X, Y, Z, … • All three databases consistently updated to contain this information • Nuclides with floating energies are now tracked by Geant4 as particles distinct from nuclides with non-floating levels • decays from floating levels may go to other floating levels in the correct chain • represented as, e.g., Pa234[73.92+X] • replaces old system of using very small energies to distinguish levels (0.000004)

5. Correlated Gamma Emission Fully Implemented • Using Jp values of nuclear levels, angular distribution of a gamma in decay chain now depends on previous gamma emission • Legendre and Associated Legendre polynomials used to calculate angular distribution • No longer isotropic • Still several bugs • warnings and irreproducibility • will address in work session • Extension of database and many mods of photon evaporation code required and implemented – see Vladimir’s talk

6. Better Integration with G4PhotonEvaporation • Now use G4RadioactiveDecay::BuildPhysicsTable to set photon evaporation parameters • because choices must be made at initialization time • can decide whether or not to use correlation, new file structure • Added production of e- and gamma spectra from de-excitation of excited levels in biased mode • Instantiate G4PhotonEvaporation only once in G4ITDecay to reduce memory churn • can do better  will move instantiation to G4RadioactiveDecay

7. Irreproducibility • Returns when correlated gammas turned on • according to Alberto’s tests • may be due to incorrect caching of polarization state • Still some problems even when correlated gammas turned off • maybe in de-excitation • maybe in RDM • Subject of a working session

8. Biased Mode • An old user-reported problem • still waiting on re-design of biasing code to try and tackle this • New user-reported bug (#1946): weight of parent track not propagated to daughters in G4RadioactivedDecay::DecayIt() • now fixed, but what effect on biased running in the past? • Biasing still done as part of process • should be separated from actual RDM process and done in an application •  re-design working session

9. Rare Processes • Not much work done on double beta decay • have code – must translate • are there more? • Beta-delayed n, p

10. Multithreading • Not really used in RDM • gave rise to irreproducibility • code redesign? • Lazy initialization could be a problem • decay table for a given nuclide only created when needed • local threads not properly entering new nuclides in master table?  work session

11. Publication • A lot has gone on in the last several years • RDM greatly improved • let’s publish! • We have everything we need to write a paper, except some pretty plots • need to produce some validation plots •  work session