1. Revisions and Updates, December 13. Some technical details:
Results shown at 5 Dec meeting had major bug: the Phase 2 simulations without HGTD also accidentally did not have ITk (the tracking volume was simply empty)
occurred due to typo in configuration file
Cross-check uncovered some issues in GDML file for ITk (overlapping volumes). Only some of these were fixed for 5 Dec results, now all are fixed.
Since we had a bit more time, we’ve run ~3x more statistics than we showed on 5 Dec
EWV1

2. Conclusions from studies with corrected materials
EWV2
Conclusions from studies with corrected materials
Main takeaway points are:
- In general, ITk seems to lead to higher radiation backgrounds than current tracker
- The presence of the HGTD does have a substantial effect on radiation in the ID region
- Rates in the NSW region are essentially unaffected by the options we’re considering

3. Radiation Backgrounds Studies In ATLAS Phase 21
Erich Varnes and Michael Shupe, Dec. 6, 2016, Rev. Dec. 13
* Rates and doses in the ATLAS inner detector, comparing
Run1 ID to Phase2 ITk.
* Comparisons of rates and doses in the Phase2 ITk,
without and with the HGTD (10cm to 28cm).
* Phase 2 rates and doses in the New Small Wheel (NSW)
without and with the HGTD.
* Reference section following the Conclusion for more
plots of background rates, doses, and ratios. Also
online access to all individual fluxplot and fluxtext files.

4. 2
RATES AND DOSES IN THE INNER DETECTOR: COMPARING RUN1 ID TO PHASE2 ITK WITH NO HGTD

5. NIEL Dose [1 MeV equiv N/cm^2/3000/fb] ATLAS Base Run1 and Phase2
Run1 Inner Detector
Run1 Inner Detector
Phase 2 ITk
EC Bpoly 5cm ID
ITk
FCal
FCal
With the Phase2 beampipe and ITk (right), the NIEL doses in the inner detector have been increased slightly. The local changes may be due to differences in services routing and detector support materials. 3

6. NIEL Dose with 3000/fb near end of ID: Z=260-264cm R=10-100 cm
The black line is the Run1 ID rate, and the red line is the Phase2 ITk rate. The ITk increases the NIEL dose by about 20% in this region. 6

7. Hadrons>20 MeV/cm^2/3000/fb - Displacement Damage5
Run 1 Inner Detector
ATLAS 2013
Phase2 ITk ID ID
FCal
FCal
Characteristic of high-energy backgrounds, the doses of hadrons >20MeV do not change significantly between the Run1 and Phase2 trackers. The effects are typically in the 5% to 10% range. See plots in additional materials.

8. SEUs with Ppi>10MeV + N>2MeV [/cm^2/3000/fb]6
Run1 Inner Detector
ATLAS 2013
Phase2 ITk ID ID
FCal
FCal
A mixed flux with different energy thresholds: SEU (Single Event Upset) doses. The SEU doses have local differences of x2 or more, as shown on slide 7. The ITk has higher doses near the beamline and lower doses at larger r.

9. SEUs with 3000/fb near end of ID: Z=260-264cm R=10-100 cm7
The black line is the Run1 ID dose, and the red line is the Phase2 ITk dose. In this z location, the SEU dose in the ITk is considerably higher than the Run1 ID at small radii, and considerably lower at large radii. . 9

10. Thermal Neutrons [kHz/cm^2]: ATLAS Base Run1 and Phase 28
Run1 Inner Detector
Baseline with Bpoly
Phase 2 ITk ID ID
FCal
FCal
The ITk has more light elements (mainly hydrogen and carbon), which moderate more of the low energy neutrons, leading to an increase the rates of thermal neutrons.

11. Thermal neutrons near end of ID: Z=260-264cm R=10-100 cm9
The black line is the Run1 ID rate, and the red line is the Phase2 ITk rate This reflects the additional hydrogenic materials in the Itk. 11

12. Energy Deposition [GeV/cm^3/s] ATLAS Base Run 1 and Phase 210
Run1 Inner Detector
Phase 2 ITk ID
ITk
FCal
FCal
The energy deposition rates are compared in the Run1 and Phase2 geometries. Since the two inner detectors are quite different, and energy is deposited in dense structures, the contour maps and radial plots are not particular informative.

13. Ionizing Dose [Gy/3000/fb] ATLAS Base Run1 and Phase211
Run1 Inner Detector
Phase 2 ITk
Phase 2 ITk ID
ITk ID
FCal
FCal
FCal
The ionizing dose in the inner detector have roughly similar contours. But the ionization dose varies sharply where there are high density materials, namely: detector elements and services, and structural members. See next slide.

14. Ionizing dose with 3000/fb in HGTD: Z=348-352cm R=20-70 cm12 14

15. 13
COMPARISONS OF RATES AND DOSES IN THE PHASE2 ITK: WITHOUT AND WITH THE cm HGTD HERE WE CONSIDER THE EFFECTS OF THE HGTD NEAR THE END OF THE ITK, AND RATES AND DOSES INSIDE THE HGTD

16. Geometry For HGTD In These Studies 14
Materials in HGTD Gaps
60-28 cm cm
3 W Absorber AIR
HEC1
EC Warm Wall
EMEC
5cm Bpoly on EC face
60 cm
W Absorber in 3 gaps
28 cm
FCal
Air in 3 gaps
10 cm
Alcove Moderator, as currently in ATLAS 16 16

17. 15 Plate Level Geometry for the HGTD Outer and Inner Regions
This example shows the option with 3 W plates outer, and 3 Air inner 15
HGTD Plate-level Geometry
5cm BPE on EC W W W
Mountings A A A
Bpoly
Inner radius is 10 cm

18. NIEL Dose [1 MeV equiv N/cm^2/3000/fb] Phase2 Without and With HGTD
Phase 2 ITk
Phase 2 ITk With HGTD
EC Bpoly 5cm
ITk
ITk
FCal
FCal
For the Phase2 beampipe and ITk: the NIEL doses are compared without (left) and with (right) the HGTD. With the HGTD, the NIEL dose in the ITk increases by ~x1.3 near the end of the tracker. 16

19. NIEL dose with 3000/fb near end of ITk: Z=260-264cm R=10-100 cm17
HGTD results in an increase of ~x1.3 in the NIEL dose in the tracker region 19

20. NIEL dose with 3000/fb inside the HGTD: Z=348-352cm R=20-70 cm18
For the Phase2 beampipe and ITk: the NIEL dose inside the HGTD is the red line on the left graph. The ratio comparison with no HGTD (the graph on right ) is not very useful. 20

21. Hadrons>20 MeV/cm^2/3000/fb: Phase 2 Without And With HGTD19
ATLAS 2013
Phase 2 ITk
Phase 2 ITk With HGTD
ITk
ITk
FCal
FCal
For the Phase2 beampipe and ITk: the hadron>20 MeV doses are compared without (left) and with (right) the HGTD. The rates with and without the HGTD are essentially the same near the end of the tracker.

22. Hadrons > 20 MeV near end of ITk: Z=260-264cm R=10-100 cm
The black line is the rate without the HGTD, and the red line is the rate with the HGTD. 22

23. Hadrons > 20 MeV with 3000/fb inside HGTD: Z=348-352cm R=20-70 cm21
The black line is the dose without the HGTD, and the red line is the dose inside the HGTD. The increase of ~1.2 in the hadrons >20 MeV dose is probably because the HGTD itself serves as a secondary target source of hadrons. 23

24. SEU Rates: Ppi>10MeV + N>2MeV [/cm^2/3000/fb] P2 Wo/W HGTD22
ATLAS 2013
Phase 2 ITk
Phase2 ITk
Phase 2 ITk With HGTD
ITk
ITk
FCal
FCal
With the Phase2 beampipe and ITk: the SEU doses are compared without (left) and with (right) the HGTD. With the HGTD, the SEU dose near the end of the ITk increases slightly (~10%) in this region.

25. SEUs with 3000/fb near end of ITk: Z=260-264cm R=10-100 cm23
The black line is the dose without the HGTD, and the red line is the dose near the end of the ITK, illuminated by HGTD albedo. The increase of ~10% in the hadrons >20 MeV dose is probably due to the HGTD itself serving as a secondary target . 25

26. SEUs with 3000/fb inside HGTD: Z=348-352cm R=20-70 cm24
The black line is the dose without a HGTD, and the red line is the dose inside the HGTD. The increase of ~2.0 in the SEU dose is probably because the HGTD itself serves as a secondary target. 26

27. Thermal Neutrons [kHz/cm^2]: Phase 2 Without and With HGTD25
Phase 2 ITk
Phase 2 ITk With HGTD
ITk
ITk
FCal
FCal
For the Phase2 beampipe and ITk: the thermal neutron doses are compared without (left) and with (right) the HGTD. With the HGTD, the thermal neutron flux in the ITk increases by ~x1.3 near the end of the tracker.

28. Thermal neutrons near end of ITk: Z=260-264cm R=10-100 cm
The thermal neutrons near the end of the ITk is the red line in these graphs when HGTD is present. The dose increases in this case by ~1.3 at the ends of the ITk, possibly from albedo from the HGTD. 28

29. Thermal neutrons inside HGTD: Z=348-352cm R=20-70 cm27
The rate of thermal neutrons inside the HGTD is the red line on the left graph. The rate increase is ~5.0 in the HGTD close to the beamline (where there is no absorber) and ~2.5 in the outer section of the HGTD with W absorbers. 29

30. 28 Energy Deposition [GeV/cm^3/s] Phase2 Without and With HGTD
Phase 2 ITk
Phase 2 ITk Inner Detector
ITk
ITk
FCal
FCal
The energy deposition rates are compared without, and with, the HGTD. In the tracker region the rates are comparable (Next slide.)

31. Energy deposition near end of ITk: Z=260-264cm R=10-100 cm29
Energy deposition near the end of the ITk is the red line in these graphs when the HGTD is present. The peaks are energy deposition in ITk structures. 31

32. Energy deposition inside HGTD: Z=348-352cm R=20-70 cm30
Energy deposition inside the HGTD is the red line in the left graph. The rate of energy deposition in HGTD is relatively low close to the beamline (where there are no absorbers) and much larger in the outer section of the HGTD with W absorbers beginning at r = 28 cm. 32

33. Ionizing Dose [Gy/3000/fb]_Without And With HGTD31
Phase 2 ITk
Phase 2 ITk With HGTD
Phase 2 ITk
ITk
FCal
FCal
For the Phase2 beampipe and ITk: the ionizing doses are compared without (left) and with (right) the HGTD. The doses are essentially the same in the tracker region (Next slide.)

34. Ionizing dose with 3000/fb near end of ITk: Z=260-264cm R=10-100 cm32
Ionizing dose near the end of the ITk is the red line in these graphs when the HGTD is present. The peaks are ionizing dose in ITk structures. 34

35. Ionizing dose with 3000/fb inside HGTD: Z=348-352cm R=20-70 cm33
Ionizing dose inside the HGTD is the red line in the left graph. The ionization in HGTD is relatively low close to the beamline (where there are no absorbers) and much larger in the outer section of the HGTD with W absorbers beginning at r = 28 cm. 35

36. 34
Phase 2 Rates And Doses in the New Small Wheel (NSW) Without and With HGTD
At this point, we have implemented a simple model of the
New Small Wheel (NSW), and modified the JD shielding. We have also
implemented an improved version of the JD shield, with additional
shielding disks, moderators, and Pb, following the latest SLAC geometry.

37. ATLAS Baseline Geometry vs JD Shield upgrade35
Phase2 Baseline
SLAC JD shields added
NSW
NSW
Added Shielding
FCal
FCal JD JD
The SLAC shielding includes (1) additional rings of material on the front of the flux return plate, (2) BPE and Pb layers at the inner front corner of the NSW, and (3) BPE layers at the back of the JD hub and on the JD core outer surface.

38. NIEL Dose [1 MeV equiv N/cm^2/3000/fb] Without And With HGTD36
NSW
NSW
No HGTD
HGTD JD JD
FCal
FCal
The additional SLAC shielding pieces reduce the maximum rates and doses in the NSW wheels. The next slide shows the NIEL dose as a function of r. The HGTD has little effect on the NSW backgrounds.

39. NIEL dose with 3000/fb inside NSW: Z=700-704cm R=40-120 cm37
The black line is the NIEL dose in the front of the NSW, with the highest dose at the minimum radius of the NSW, approximately 60 cm. 39

40. SEU Rates: Ppi>10MeV + N>2MeV [/cm^2/3000/fb]_In the NSW38
NSW
NSW
No HGTD
No HGTD
HGTD JD JD
FCal
FCal
SEU rates in the NSW are not very sensitive to changes in the JD shield. The NSW rates themselves are of interest for operation of the electronics and detectors.

41. SEUs with 3000/fb in NSW: Z=700-704cm R=40-120 cm39 41

42. Approximate Single Plane Counting Rates [kHz/cm^2] _In the NSW40
NSW
NSW
No HGTD
HGTD JD JD
FCal
FCal
The highest single plane counting rates in the NSW would be at the front, and near the inner radius, of the MicroMega (MM) detectors in the first wheel.

43. Approximate counting rates in NSW: Z=700-704cm R=40-120 cm41
The red line is the approximate single plane counting rate in the front of the NSW, with the highest dose at the minimum radius of the NSW, r = 60 cm. 43

44. 42
Conclusions from Previous Studies of Rates and Doses in the New Small Wheel, and Their Reduction with Added JD Shielding
Max dose reductions with SLAC shielding volumes added to the JD:
* NIEL dose in the NSW is reduced by a factor of Dose looks OK.
* SEU dose is little reduced (1.04) since low energy particles are ignored.
* Single-plane hit rates are reduced by But at max they are close to
the design limit anticipated in the NSW TDR. Further study is needed.

45. SUMMARY AND CONCLUSIONS FROM CURRENT STUDIES43
SUMMARY AND CONCLUSIONS FROM CURRENT STUDIES
Main takeaway points are:
- In general, ITk seems to lead to higher radiation backgrounds than current ATLAS tracker.
- The presence of the HGTD does increase radiation in the ID region.
- Rates in the NSW region are essentially unaffected by the options we’re considering.

46. 44
REFERENCE MATERIALS

47. Files Used For Studies Presented Here45
Files Used For Studies Presented Here
This talk contains only a small fraction of the information coming
from these simulations. All studied rates and doses are available at
the site below, in the subdirectories listed on the next slide.
Location of files:
atlas.physics.arizona.edu/~shupe/ATLAS_Phase2_Radiation_Backgrounds_Fixed/
Select Study (list on next slide): select FLUXPLOTS or FLUXTEXTS
Available doses and particle fluxes:
Detector impact: energy deposition, NIEL dose, ionizing dose,
hadrons > 20 MeV, SEU doses, star densities (for activation).
Particles: total neutrons, neutrons > 100 keV, thermal neutrons,
photons, electrons, protons, charged pions, muon single particle
detector rates. 47 47

48. Subdirectories Used for ATLAS Phase 2 Base and HGTD (Optional) Studies46
Subdirectories Used for ATLAS Phase 2 Base and
HGTD (Optional) Studies
Phase 2 Geometry With ITk And Beamline, NSW, and HGTD Option:
/FLUXPLOTS_HGTD_ (Number of events in title)
/FLUXTEXTS_HGTD_ (Text files with all backgrounds, all pixels, readable)
/FLUXPLOTS_noHGTD_32908
/FLUXTEXTS_noHGTD_32908
The chosen HGTD option is described earlier in this talk. 48 48

49. Radiation Background Normalizations In AZ Phase 2 Studies47
Radiation Background Normalizations In AZ Phase 2 Studies
As in past radiation background studies, the CM energy is 14 TeV. But we have changed the normalization of the flux and dose maps and histograms to match Phase 2 conditions. Up to 2015 studies used the luminosity 10^34 [cm^2/s]. But we now use the Phase 2 levelled luminosity of 5 X 10^34. This factor of 5 affects all rate calculations.
In the past, doses were for one running year of 10^7 s, leading to an integrated luminosity of 100/fb. But now we are reporting doses for the full Phase 2 expectation of 3000/fb, increasing the doses by a factor of 30.

50. RATES AND DOSES IN THE INNER DETECTOR: COMPARING RUN1 ID TO PHASE2 ITK WITH NO HGTD: ADDITIONAL PLOTS

51. NIEL Dose with 3000/fb near the endcap face: Z=348-352cm R=20-70 cm
The black line is the Run1 ID rate, and the red line is the Phase2 ITk rate. 51

52. Hadrons>20 MeV with 3000/fb near end of ID: Z=260-264cm R=10-100 cm
The black line is the Run1 ID rate, and the red line is the Phase2 ITk rate. 52

53. Hadrons>20 MeV with 3000/fb near endcap: Z=348-352cm R=20-70 cm
The black line is the Run1 ID rate, and the red line is the Phase2 ITk rate. 53

54. SEUs with 3000/fb near the endcap: Z=348-352cm R=20-70 cm
The black line is the Run1 ID rate, and the red line is the Phase2 ITk rate. 54

55. Thermal neutrons near the endcap: Z=348-352cm R=20-70 cm
The black line is the Run1 ID rate, and the red line is the Phase2 ITk rate. 55

56. Energy deposition near end of ID: Z=260-264cm R=10-100 cm
The black line is the Run1 ID rate, and the red line is the Phase2 ITk rate. 56

57. COMPARISONS OF RATES AND DOSES IN THE PHASE2 ITK: WITHOUT AND WITH THE cm HGTD ADDITIONAL PLOTS

58. Ionizing dose with 3000/fb near end of ID: Z=260-264cm R=10-100 cm58

59. Energy deposition in HGTD: Z=348-352cm R=20-70 cm59