1. 1 Background radiation studies in LHCb with GAUSS/Geant4 giuseppe.daquino@cern.ch Giuseppe G. Daquino PH/SFT

2. 2 Summary  Introduction  Methods  Results  Discussion  Conclusions Giuseppe G. Daquino CERN, 2 nd May 2005 SoFTware Development for Experiments Group Experimental Physics, CERN

3. 3 Introduction  Knowledge of particle fluences 1, their energy spectra and absorbed doses 2 is necessary to estimate the damage probability of detectors and electronics  Possible background radiation effects are:  Gradual, such as total ionizing dose or displacement damage  Local and acute, such as SEU (upset of a memory cell and revert individual triggers or switches) or SEL (permanent damage of the device)  Previous calcs have been performed using MARS, GCALOR and FLUKA 1 Fluence (1/cm2) , where V is the voxel volume 2 Dose (Gy) , where M is the voxel mass Giuseppe G. Daquino CERN, 2 nd May 2005 SoFTware Development for Experiments Group Experimental Physics, CERN

4. 4  The displacement damage can be evaluated through the calculation of the 1MeV-neutrons equivalent fluence for silicon.  The displacement damage cross section for silicon for 1 MeV-neutrons is set as normalizing value: 95 MeV  mb. Damage efficiency of any particle is described by the hardness factor, defined as:  EDK is the energy spectrum averaged displacement KERMA  The hardness factor is used as multiplication factor for the fluence distribution  eq 1MeV = k·  p Giuseppe G. Daquino CERN, 2 nd May 2005 SoFTware Development for Experiments Group Experimental Physics, CERN

5. 5  Interest from Geant4 and LHCb collaboration to verify how to use Geant4 for the background radiation studies  In the past, a parametrization of the GCALOR (with SICBMC) results has been used to correct standard simulation for low energy background component in muon system  In the LHCb collaboration radiation calculations have been performed making use of FLUKA.  A different pp collision generator and geometry  The GAUSS framework has been used to study the background radiation in LHCb Giuseppe G. Daquino CERN, 2 nd May 2005 SoFTware Development for Experiments Group Experimental Physics, CERN

6. 6 Methods  An ad hoc module, named SensPlane, has been integrated in GAUSS in order to score doses and fluences in planes positioned in proper locations  The main items are: 1) scoring planes defined and integrated in the LHCb geometry via XML description 2) the module takes the geometry info on the scoring plane directly from the XML description 3) the scored particles are defined via job options 4) the parameters to monitor have been defined via job options: tallying of doses and fluences in a specific plane and for a specific particle 5) the module provides automatically the 2D distributions and the energy spectra, provided that the geometry description of the scoring plane is a voxel parametrization. Giuseppe G. Daquino CERN, 2 nd May 2005 SoFTware Development for Experiments Group Experimental Physics, CERN

7. 7  No tracking cuts have been used  The doses and fluences are calculated taking the full information from G4Step (->G4Track)  Four scoring planes positioned in LHCb setup, taking into account the angular coverage (300 mrad)  The space around the “beampipe” is approximated via a box-shaped hole, with size calculated through 10 mrad inclination  The arbitrary choice of the 2D map binning can lead to a mismatch between the hole and the adjacent scoring voxels.  Used Gauss v18r4, Geant4 v62r0p2, LHCb v17r3, Gaudi v15r3 Conditions and constraints...  Scoring planes cannot be positioned overlapping pre-existing geometry. Double navigation is not implemented yet in Geant4 Giuseppe G. Daquino CERN, 2 nd May 2005 SoFTware Development for Experiments Group Experimental Physics, CERN

8. 8  SensPlane provides automatically the following results:  particle “tallyable” are: p, n,  ±, K , , e , …  energy spectra of fluence (1/cm 2 ) registered on the scoring plane by the tallied particles  2D distribution of the high energy hadrons (>20 MeV) fluence (1/cm 2 ) registered on the scoring plane  2D distribution of the fluence of the tallied particle, registered in each voxel of the parametrized structure  2D distribution of the dose delivered in each voxel by each tallied particles  In post-processing this data can be combined in order to obtain other fruitful information:  2D distribution of the total ionising dose  2D distribution of the total charged hadrons fluence  1MeV neutron equivalent fluence: a weighted sum of all the fluences due to protons, neutrons, electrons and pions, rescaled to the 1 MeV neutrons damage Tallies... Giuseppe G. Daquino CERN, 2 nd May 2005 SoFTware Development for Experiments Group Experimental Physics, CERN

9. 9  It is also possible to create automatically:  the histograms of the particles going in forward and backward direction  detailed information in the job output related to the particle hitting on the scoring plane (momentum, position, parent, etc.)  1 MeV-neutrons equivalent fluence for silicon is calculated as sum of the weighted fluence contributions of each particle type.  1 MeV-neutrons equivalent fluence calculations are performed assuming that the scoring planes are made by silicon  The following results have been obtained with 6 hadronic physics lists: lhep, lhep_hp, qgsp, qgsp_hp, lhep_bert_hp, qgsp_bert_hp Post-processing... Giuseppe G. Daquino CERN, 2 nd May 2005 SoFTware Development for Experiments Group Experimental Physics, CERN

10. 10 G4 physics lists...  G4 provides many models for hadronic interaction (specialized for particles in different energy ranges)  Predefined combination of models are provided as Physics Lists. The combination of the models depends on the type of studies/applications.  CPU performance is different for various physics lists.  Being G4 a toolkit, you can built yourself the most appropriate physics list  Physics lists used:  LHEP: parametrized models (similar to GEISHA/G3)  QGSP: quark gluon string (>5 GeV) + parametrization (between 5GeV and 100 MeV) + pre-compound (<100MeV)  HP: extension for the treatment of low energy neutrons (<20 MeV)  BERT: Bertini cascade (for , p, n, but not yet for K) Giuseppe G. Daquino CERN, 2 nd May 2005 SoFTware Development for Experiments Group Experimental Physics, CERN

11. 11 LHCb layout  and 4 scoring planes… Giuseppe G. Daquino CERN, 2 nd May 2005 SoFTware Development for Experiments Group Experimental Physics, CERN

12. 12 … more in details, around 2690 mm Giuseppe G. Daquino CERN, 2 nd May 2005 SoFTware Development for Experiments Group Experimental Physics, CERN

13. 13 Results LHEP @ 7830 Giuseppe G. Daquino CERN, 2 nd May 2005 SoFTware Development for Experiments Group Experimental Physics, CERN Neutron fluenceTotal charged hadrons fluence

14. 14 Giuseppe G. Daquino CERN, 2 nd May 2005 SoFTware Development for Experiments Group Experimental Physics, CERN Gamma fluence Total ionising dose

15. 15 Giuseppe G. Daquino CERN, 2 nd May 2005 SoFTware Development for Experiments Group Experimental Physics, CERN Electrons/Positrons spectrumNeutrons spectrum

16. 16 Giuseppe G. Daquino CERN, 2 nd May 2005 SoFTware Development for Experiments Group Experimental Physics, CERN Total charged hadrons spectrum

17. 17 2 bands for physics lists comparison Band 3 Band 2 Giuseppe G. Daquino CERN, 4 th May 2005 SoFTware Development for Experiments Group Experimental Physics, CERN …finding the most appropriate physics list

18. 18 Giuseppe G. Daquino CERN, 2 nd May 2005 SoFTware Development for Experiments Group Experimental Physics, CERN Electrons/Positrons fluence Band 2 @ 7830 Electrons/Positrons fluence Band 3 @ 7830

19. 19 Giuseppe G. Daquino CERN, 2 nd May 2005 SoFTware Development for Experiments Group Experimental Physics, CERN Protons fluence Band 2 @ 7830 Protons fluence Band 3 @ 7830

20. 20 Giuseppe G. Daquino CERN, 2 nd May 2005 SoFTware Development for Experiments Group Experimental Physics, CERN Total charged hadrons fluence Band 2 @ 7830 Total charged hadrons fluence Band 3 @ 7830

21. 21 Giuseppe G. Daquino CERN, 2 nd May 2005 SoFTware Development for Experiments Group Experimental Physics, CERN Neutrons fluence Band 2 @ 7830 Neutrons fluence Band 3 @ 7830

22. 22 Giuseppe G. Daquino CERN, 2 nd May 2005 SoFTware Development for Experiments Group Experimental Physics, CERN Total ionising dose Band 2 @ 7830 Total ionising dose Band 3 @ 7830

23. 23 Spectra calculated with all 4 physics lists Giuseppe G. Daquino CERN, 2 nd May 2005 SoFTware Development for Experiments Group Experimental Physics, CERN Out of the evaporation code of the parametrized model Neutrons spectrum @ 2690 Neutrons spectrum @ 7830

24. 24 Giuseppe G. Daquino CERN, 2 nd May 2005 SoFTware Development for Experiments Group Experimental Physics, CERN Out of the evaporation code Neutrons spectrum @ 11920 Neutrons spectrum @ 13370 QGSP_BERT_HP

25. 25 Giuseppe G. Daquino CERN, 2 nd May 2005 SoFTware Development for Experiments Group Experimental Physics, CERN Electrons/positrons spectrum @ 11920 Total charged hadrons spectrum @ 11920

26. 26 QGSP_BERT_HP results Total ionising dose 1 MeV neutron equivalent fluence Scoring plane @ 2960 Giuseppe G. Daquino CERN, 2 nd May 2005 SoFTware Development for Experiments Group Experimental Physics, CERN

27. 27 Scoring plane @ 7830 Total ionising dose1 MeV neutron equivalent fluence Giuseppe G. Daquino CERN, 2 nd May 2005 SoFTware Development for Experiments Group Experimental Physics, CERN

28. 28 Scoring plane @ 11920 Total ionising dose1 MeV neutron equivalent fluence Giuseppe G. Daquino CERN, 2 nd May 2005 SoFTware Development for Experiments Group Experimental Physics, CERN

29. 29 Scoring plane @ 13370 Total ionising dose 1 MeV neutron equivalent fluence Giuseppe G. Daquino CERN, 2 nd May 2005 SoFTware Development for Experiments Group Experimental Physics, CERN

30. 30 Discussion Giuseppe G. Daquino CERN, 2 nd May 2005 SoFTware Development for Experiments Group Experimental Physics, CERN  Results show expected 2D distributions for:  neutrons (uniform)  protons (slightly peaked on the right due to the polarity of the magnet, during the simulation)  electrons/positrons balance  low statistics at far-from-center bands  neutrons production increase using the HP extension. Additional increase using the Bertini cascade to be investigated further.  Peak-centered 2D distribution for the total ionising dose (up to ~10 -12 Gy/collisions). Influence of the magnet on the distribution.

31. 31 Giuseppe G. Daquino CERN, 2 nd May 2005 SoFTware Development for Experiments Group Experimental Physics, CERN  Energy spectra show:  physics lists provide a good agreement for the electrons/positrons and total charged hadron  low energy neutrons are treated through the HP extension. But it still contains a 1keV peak, due to the evaporation code of the pararametrized model  The addition of the Bertini cascade to the pre-compound, to the quark-gluon model with HP extension is an adequate solution for the proper treatment of the neutrons throughout all the energy range (QGSP_BERT_HP)  The use of the LHEP integrated with the Bertini cascade provides a physics list, which still shows the 1keV peak, because the Bertini does not replace completely the parametrized model for this energy range. Discussion (cont’d)

32. 32  The 1MeV neutrons equivalent fluence gives an indication on the displacement damage. The QGSP_BERT_HP results show a centered- peak distribution (up to 10 -1 collisions -1  cm -2 ) in all the scoring planes  Bigger values are present @ 2690 mm (mostly due to the primaries) and @ 13370 mm (due to the calorimeter effect)  The total ionising dose is a reference for the gradual radiation damage. QGSP_BERT_HP results show centered-peak distributions (up to 10 -12 Gy/collisions). Discussion (cont’d) Giuseppe G. Daquino CERN, 2 nd May 2005 SoFTware Development for Experiments Group Experimental Physics, CERN

33. 33 Conclusions Giuseppe G. Daquino CERN, 2 nd May 2005 SoFTware Development for Experiments Group Experimental Physics, CERN  A module has been implemented in Gauss to “tally” a set of particles, to be monitored for the evaluation of the possible electronics damage  We have shown that Geant4 can be used for background radiation studies in LHCb, within the GAUSS framework.  The combination of the QGSP, the Bertini cascade and the HP extension gives a good answer to the problem requirements (QGSP_BERT_HP physics list).  All the 6 physics lists show a reasonable agreement for the other tallied particles fluence and the total ionising dose.  Neutron fluence results show sensible differences between the use of 6 different physics lists. The reason is due to the models contained in them.

34. 34 Giuseppe G. Daquino CERN, 2 nd May 2005 SoFTware Development for Experiments Group Experimental Physics, CERN Addendum on the G4/Fluka comparison of the background radiation studies results  Work is in progress  2D maps comparison with bands  Spectra are still under investigation  Results on scoring plane @ 7830 mm

35. 35 Giuseppe G. Daquino CERN, 2 nd May 2005 SoFTware Development for Experiments Group Experimental Physics, CERN 7830 mm plane Band 1 Band 2 Neutron fluence

36. 36 Giuseppe G. Daquino CERN, 2 nd May 2005 SoFTware Development for Experiments Group Experimental Physics, CERN Band 1Band 2

37. 37 Giuseppe G. Daquino CERN, 2 nd May 2005 SoFTware Development for Experiments Group Experimental Physics, CERN Charged hadrons fluence 7830 mm plane

38. 38 Giuseppe G. Daquino CERN, 2 nd May 2005 SoFTware Development for Experiments Group Experimental Physics, CERN Band 1Band 2

39. 39 Giuseppe G. Daquino CERN, 2 nd May 2005 SoFTware Development for Experiments Group Experimental Physics, CERN Electron/positron fluence 7830 mm plane

40. 40 Giuseppe G. Daquino CERN, 2 nd May 2005 SoFTware Development for Experiments Group Experimental Physics, CERN Band 1Band 2

41. 41 Giuseppe G. Daquino CERN, 2 nd May 2005 SoFTware Development for Experiments Group Experimental Physics, CERN Total ionising dose 7830 mm plane

42. 42 Giuseppe G. Daquino CERN, 2 nd May 2005 SoFTware Development for Experiments Group Experimental Physics, CERN Band 1Band 2

43. 43 Giuseppe G. Daquino CERN, 2 nd May 2005 SoFTware Development for Experiments Group Experimental Physics, CERN THANK YOU