Geant4 Radioactive Decay Highlights from the Geant4 Radioactive Decay Mini-workshop Dennis Wright 25 May 2016

Outline Summaries from talks Notes from discussions last year’s progress handling floating levels database improvements RDM tests (biased and un-biased) problems with random number generators using Geant4 for super-heavy elements improvements in PhotonEvaporation code Notes from discussions multithreading issues discussion of floating levels atomic deexcitation beta-delayed neutrons use cases and requirements for biasing

Progress Since Last Year (D.H. Wright) RDM, PhotonEvaporation and ENSDFSTATE databases now consistent with one another Reproducibility problems (in both sequential and multithreading mode) have all been fixed Improved energy conservation for all RDM channels Refactoring of RDM non-biased code completed Code for angular correlation of cascade gammas nearly ready to be installed Photon evaporation code improved and updated New channels added (decay by proton emission, neutron emission) Many lost levels found and bugs fixed

Handling Unresolved (Floating) Levels (T. Koi) A non-negligible number of decay chains are based on levels whose energies are not known Levels denoted by guessed energy level plus X, Y, Z, etc. e.g. 108Tc[176.6+X] Currently treated in Geant4 as having energy 176.600004 in order to distinguish from known level nearby 92 isomers have no listed ground state at 0; 79 of these are 0+X levels; 13 have no information for ground state Agreed last year that these levels should be handled by model and propagated as a unique ion (distinct from nearby level)

Handling Unresolved (Floating) Levels (T. Koi) Proposed solution: set minimum difference between levels to be 1 meV in particle category and add character to particle name, e.g. 108Tc [176.6X] How to handle transitions from floating levels to non-floating levels (energy conservation problems) 234Pa[73.92+X] particularly important example (floating levels confused with fixed)

A Few Notes on X, Y, Z Levels (M. Venhart) Floating levels (X, Y, Z, ..) occur for several reasons gamma ray spectroscopy difficult in some cases they decay by low energy transitions (hard to measure) states fed only by other floating states decay only by beta decay (hard to fit) nobody tried to measure mistakes were made Such states are general problem of nuclear physics we must identify critical cases and evaluate data ourselves 92 cases known so far

Database Improvements (L. Desorgher) Levels in RadioactiveDecay4.3.1, PhotoEvaporation3.2.1 and ENSDFSTATE1.2 now consistent some corrections for Geant4 10.2. p01 Q values now taken directly from Qcalc PhotonEvaporation db now has easy-to-read format corrected use of BRICC to compute internal conversion coefficients

RDM Tests (L. Desorgher) Use single decay of different nuclei from example rdecay02 (gamma, x-rays, electrons from 214Bi, alphas from 238U, Generally good comparison to data In biased mode, looked at activity in bunker walls from 45 MeV electrons (very good agreement) Example rdecay02: 137Cs, 99Mo, 226Ra => generally good agreement

Random Number Generators (A. Howard) Granularity and repetition are crucial for radioactive decay Serious issues with granularity and computation time observed Several engines tested: Ranecu, Ranlux, Ranshi, Ranlux64, Mersenne Twist, MixMax Race conditions appear in MixMax Ranshi doesn’t produce randoms over full interval (0:1) Serious clumping observed in Ranlux Many other results plotted

SuperHeavy Elements in Geant4 (L. Sarmiento) proton emission experiment described – very sensitive excellent agreement of experiment and Geant4 for 53Co better atomic relaxation code is needed for x-ray fingerprinting of new heavy elements high quality code is available – need to implement it rather than make work-around for current code move away from current G4AtomicShells to G4AtomicShells_EADL

PhotonEvaporation Improvements (V. Ivantchenko) Messy design, many problems over the years Many problems fixed 4-momentum balance reduced memory churn and overhead … In order to fix many other problems, new code developed default for 10.2 old code still available Code used by hadron inelastic neutron capture radioactive decay (with single gamma transition)

Multithreading Issues Locks currently slow down RDM when reading decay tables checking that data is there causes delay possible solution: use double checking as done in ion table (thread-local bool) or G4LevelManager in G4PhotonEvaporation Database storage could be optimized by using less granular groupings of files (such as one file with decay data from all nuclei with same A) convert to binary to speed up reading users would see no changes (granular ascii files still visible) consider using SQLite which supports multithreading

Dealing with Floating Levels How do we handle transitions which are floating to fixed fixed to floating Check to see if any floating levels can be made fixed by evaluating existing data When any change made, document in data file header also any data coming from other than ENSDF (e.g. Nuclear Wallet Cards) should be documented in header User should be able to configure data reader to set X, Y, and Z Nuclides with X, Y, Z etc. levels should be trackable objects, unique from nuclides with fixed level

Dealing with Floating Levels Implementation: extra argument for ions (character representing X, Y, Z, etc.) Get, Find, Create methods in G4IonTable must all be changed levels represented as 108Tc[176.6X], instead of 108Tc[176.600004] does this pose a problem with too many digits? extra column (with X, Y, Z etc.) to be added to database entries still need to work out how to do transitions (truncate?)

Atomic Deexcitation Current model is approximate and does not handle pick-up or loss of electrons into outer shells (e.g. for alpha, beta decay) results in energy non-conservation RDM currently uses G4UAtomicDeexcitation should use G4VAtomicDeexcitation detailed model of Tibor Kibedi is available as a possible replacement Currently local energy deposit is not done implementing this may help a bit with energy non-conservation

Beta-delayed Neutrons Correct model would be to invoke precompound model after beta decay to highly excited level however, the emission of beta and neutron appears to be nearly simultaneous also the energy levels are spread out -> do we know level density at high excitations? decide to implement directly within RDM (no precompound) details of decay listed in ENSDF new entries in table will be made use 29Na as test case

Redesign of Biased Radioactive Decay Large project Currently in biased mode the RDM process accumulates rates within the process no other Geant4 process does this -> should not be allowed Attempt to re-design based on generic Geant4 biasing can generic biasing handle all existing RDM biasing options? is it correct for both at-rest and in-flight decays List of use cases and requirements compiled see slides below An example of how to proceed is in example GB01 /examples/extended/biasing/GB01

Redesign of Biased Radioactive Decay What is biasing? allowing RDM only in certain volumes integrating over unobserved particles (fast beta, e.g.) emphasizing specific branching ratios sampling rates, weights within time windows collimation Implementation make a non-biased version of RDM process wrap it in biasing class move all current biasing methods to wrapper develop UI commands for configuring biasing

Redesign of Biased Radioactive Decay Tallying of histories should be done by scorers attach scorer to process Input source time profiles by macro (not data or histogram file) Must be able to collect activities using Bateman equations

Use Cases and Requirements for Biasing Activation in radiation detectors spacecraft in beam line shielding Decay chains in low background experiments Radioactive source simulations specify source activity and time (DAQ) window make UI command for this source profiles Radiotherapy observation of decay within energy or time windows (in beam imaging) Examine biasing options in MCNP, FLUKA

Use Cases and Requirements for Biasing Isotope production splitting branching ratio biasing Backgrounds due to accidental coincidences PET rare decays with gammas Total dose, pulse height tallies Integrating un-observed particles fast beta decay when neutrinos or other particles are not needed GUI for nuclide tables

Use Cases and Requirements for Biasing Weight window for branching ratio biasing to replace existing option for equal branching ratios Specification of ranges in (A,Z) list of (A,Z,E) specify levels by time limit (minimum time?) Retain attachment to volumes currently logical volumes – what about physical? do this within process

Backup Slides

Tasks Martin Venhart Laurent Desorgher Alberto Ribon Alex Howard examine 92 known floating levels to see if existing data can be used to fix them contact T. Kibede to see if Geant4 may use his atomic relaxation code Laurent Desorgher add column in photon evaporation database for multi-polarity and delta add beta-delayed neutron data to database Alberto Ribon test for thread saturation in random number generation Alex Howard continue testing of random number generators

Tasks Makoto Asai Andrea Dotti Dennis Wright Marc Verderi add character argument to ions, as well as Get, Find, Create methods attach scorer to process (for biasing) work on binary database implementation Andrea Dotti test for thread saturation in random number generation Dennis Wright make RDM model for testing which has all biasing code removed replace G4UAtomicRelaxation with G4VAtomicRelaxation implement double beta decay using spectrum from Luciano Pandola Marc Verderi check correctness of generic biasing in both at-rest and in-flight modes

Tasks Luis Sarmiento Unassigned write code for beta-delayed neutron channel Unassigned check lower limit on life time (10e-14 ?) 9B decays develop new RDM example (rdecay03) to demonstrate new decay channels according to XEON-Phi tests Geant4 is now CPU-bound -> general improvement in coding is required allow assignment of RDM to G4Region as well as G4LogicalVolume

Design Teams Floating Levels Biasing Makoto Asai Martin Venhart Tatsumi Koi Vladimir Ivantchenko Laurent Desorgher Biasing Marc Verderi Alex Howard Luis Sarmiento Dennis Wright Giovanni Santin Makoto Asai Laurent Desorgher

Design Teams Beta-delayed neutrons Random Numbers Luis Sarmiento Laurent Desorgher Dennis Wright Tatsumi Koi Random Numbers Alex Howard Alberto Ribon Andrea Dotti