Erich Varnes and Michael Shupe Radiation Backgrounds Working Group, July 5, And HGTD General Meeting, July 6-7, 2016 Erich Varnes and Michael Shupe Department of Physics, The University of Arizona The Arizona group uses the Phojet event generator, Geant3, for detector description and particle transport, with GCalor for neutron transport. The G3/Gcalor interface was written by Christian Zeitnitz. Topics to be covered in Working Group, July5: * Phase 2 rates and doses in the ATLAS inner detector and the NSW, and the effects of EC moderator. Topics for HGTD 2-Day Meeting, July 6-7, starting slide 22: * Phase 2 rates and doses in the HGTD for various HGTD design options, and effects in the inner detector.

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.

Studies of Phase 2 rates and doses in the ATLAS Inner Detector (with new beamline), and in the New Small Wheel (NSW). (1) Influence of EC Bpoly moderator on rates and doses in the ID and the NSW. (2) Affects on rates and doses in the NSW if FCal Plug3 is shortened to allow for sFCal services at back of Plug3. First, the inner detector plots (+ HGTD preview)

NIEL Dose [1 MeV equiv N/cm^2/3000/fb]: The effect of 5cm Bpoly on the EC ATLAS Baseline EC Bpoly removed EC Bpoly 5cm ID ID FCal FCal If the EC Bpoly is removed, the NIEL dose in the inner detector increases by a factor ~2 in the tracker regions near the face of the endcap calorimeter.

NIEL Dose with 3000/fb near end of ID: Z=344-348cm R=5-70 cm All Options – EC Bpoly, HGTD, etc. HGTD options Green – No ECPoly Black – Baseline Red – sFCal Plug3 This is the ratio for the ATLAS Base, with EC Bpoly removed. 5

NIEL Dose with 3000/fb inside the ID: Z=260-264cm R=5-70 cm All Options – EC Bpoly, HGTD, etc. Black – Baseline Red – sFCal Plug3 Green – NoECPoly All other colors are HGTD options 6

NIEL Dose with 3000/fb at center of ID: Z=0-4cm R=5-70 cm All Options – EC Bpoly, HGTD, etc. Black – Baseline Red – sFCal Green – NoECPoly All other colors are HGTD options No ratio plot needed. All options are identical 7

SEU Rates: Ppi>10MeV + N>2MeV [/cm^2/3000/fb] ATLAS Baseline ATLAS 2013 EC Bpoly removed ID ID FCal FCal If the EC Bpoly is removed, the SEU doses in the inner detector increase somewhat in front of the EC. The graphs showing rates and ratios are below

SEU: Ppi>10MeV+N>2MeV [/cm^2/3000/fb] Z=344-348cm R=5-70 cm All Options – EC Bpoly, HGTD, etc. Black – Baseline Red – sFCal Plug3 Green – NoECPoly All other colors are HGTD options This is the ratio for the ATLAS Base, with EC Bpoly removed. 9

SEU: Ppi>10MeV+N>2MeV [/cm^2/3000/fb] Z=260-264cm R=5-70 cm All Options – EC Bpoly, HGTD, etc. No ratio plot needed. All options are identical 10

SEU: Ppi>10MeV+N>2MeV [/cm^2/3000/fb] Z=0-4cm R=5-70 cm All Options – EC Bpoly, HGTD, etc. No ratio plot needed. All options are identical 11

Hadrons>20 MeV/cm^2/3000/fb - Displacement Damage ATLAS Baseline ATLAS 2013 EC Bpoly removed ID ID FCal FCal The doses of hadrons >20MeV do not change significantly due to the presence/absence of Bpoly on the endcap cryostat.

Thermal Neutrons [kHz/cm^2]: Possible increases in flux of capture gammas ATLAS Baseline Baseline with Bpoly Bpoly removed ID ID FCal FCal The thermal neutron rate in the inner detector increases significantly if the EC Bpoly is removed. If the ITk electronics contains Boron, neutron capture could create a large flux of capture gammas in the inner detector region (with or without Bpoly).

New Small Wheel rates and doses below are for (1) ATLAS Baseline, (2) Baseline with EC Bpoly removed, (3) Baseline with Plug3 reduction for the sFCal. The simplified NSW model uses G10 for the modules and Aluminium plates for the structure. Densities are adjusted to give the correct NSW total masses for modules and structures.

SEU Rates: Ppi>10MeV + N>2MeV [/cm^2/3000/fb]_In the NSW ATLAS 2013 ATLAS Baseline NSW EC Bpoly removed NSW ID ID FCal FCal SEU rates in the NSW are not sensitive to changes in the EC moderator. The NSW rates themselves are of interest for operation of the electronics and detectors.

The following four slides show some of the critical rates and doses in the NSW. The backgrounds are highest at the front of the modules in the first NSW wheel, nearest the beamline. The plotted backgrounds in the NSW detectors are: NIEL, SEU (low threshold, previous slide), TID, and single-particle hits rate (weighted sum of rates of N + photons + P + pi + mu + e, as used in Run1).

NIEL Dose First Module Black – Baseline Red – sFCal Plug3 Green – NoECPoly

SEU Rate First Module Black – Baseline Red – sFCal Plug3 Green – NoECPoly

TID Dose First Module Black – Baseline Red – sFCal Plug3 Green – NoECPoly

NSW Detector Single Hits Rate First Wheel Caveat Emptor! From Run 1 data, the maximum hit rate is expected to be 15 kHz/cm^2 at 93 cm. We need to determine the response factors for the new NSW detectors, by simulation and/or testbeam data. Black – Baseline Red – sFCal Plug3 Green – NoECPoly Also! The hit rate would be higher if Plug3 is shortened for sFCal services. The inner radius of the first NSW wheel is the only region where the radiation shielding has been thinned appreciably, due to the removal of the brass cone in front of the CSC’s.

Conclusions and Suggestions from Preliminary Studies of Rates and Doses in the Inner Detector and NSW * The 5 cm Bpoly moderator on the front of the endcap calorimeter is essential for reducing backgrounds near the ends of the inner detector. It would also be needed for the front of any HGTD options. * The NSW backgrounds are not changed by EC moderator, or any of the HGTD options, but they are increased by thinning of FCal Plug3. -> Detector responses to incoming particles need to be updated by simulation or test beam measurements, to update the estimation of hit rates in new Phase 2 detectors. -> The VI beampipe will need to be updated again if the 3-segment scheme is adopted. -> Accurate studies of inner detector rates cannot go forward until the ITk design is finalized, and translated into simulation geometries.

Studies of Various HGTD Options: Impact on Inner Detector Rates and Doses, and Rates Within the HGTD Detector

Geometries for HGTD Option Studies Many HGTD options studied: * Always WTD and EC Bpoly * With and without TD 10cm * With and without Bpoly on WTD and TD sections All options use plate-level descriptions of WTD and TD HEC1 EC Warm Wall EMEC EC Bpoly, All Options WTD with 3 W Plates for preshower material 60 cm 28 cm FCal TD, no W preshower 10 cm Alcove Moderator, as currently in ATLAS 23 23

HGTD Plate-level Geometry with WTD and TD 5cm Bpoly on EC 5cm Bpoly on WTD Mountings WTD W W W TD Bpoly

Results of HGTD Option Studies: Rate and Dose Backgrounds, And Comparison Graphs. In this presentation we focus on NIEL doses and TID, in the inner detector and in the HGTD itself, first with dose maps, and then with ratio graphs.

NIEL Dose [1 MeV equiv N/cm^2/3000/fb] – Only WTD, no Bpoly ATLAS Baseline WTD R=28-60 cm ID ID FCal FCal The NIEL dose in the inner detector increases in front of the HGTD. Each contour changes by ~2 between its boundaries, so the NIEL dose increase is significant.

NIEL Dose [1 MeV equiv N/cm^2/3000/fb] – Only WTD, with 5cm Bpoly ATLAS Baseline WTD R=28-60 cm ID ID FCal FCal With the addition of Bpoly on the WTD, the inner detector rates decrease, but not precisely to the levels of the ATLAS baseline.

NIEL Dose [1 MeV equiv N/cm^2/3000/fb] – WTD and TD, no Bpoly ATLAS Baseline WTD R=28-60 cm and TD 10-28 cm ID ID FCal FCal The NIEL dose increases for greater distance into inner detector than with the WTD alone (without Bpoly). (Compare to 2nd slide back.)

NIEL Dose [1 MeV equiv N/cm^2/3000/fb] – WTD and TD, WTD Bpoly only ATLAS Baseline WTD R=28-60 cm and TD 10-28 cm ID ID FCal FCal Adding Bpoly on the face of the WTD alone reduces the rates relative to the slide above, but not to Baseline levels.

NIEL Dose [1 MeV equiv N/cm^2/3000/fb] – WTD and TD, both Bpoly ATLAS Baseline WTD R=28-60 cm and TD 10-28 cm ID ID FCal FCal With Bpoly on the whole HGTD (WTD+TD) the NIEL dose in the inner detector is closer to the ATLAS Baseline. (Compare to previous slide.)

NIEL Dose [1 MeV equiv N/cm^2/3000/fb] – WTD and TD 5cm, no Bpoly ATLAS Baseline WTD R=28-60 cm and TD 5-28 cm ID ID FCal FCal This would be the worst-case scenario. Previous studies considered a TD with Ri=5cm. The ID rates are similar to 3 slides back. The differences are very small because the TD has little material compared to the WTD section. But rates and doses in the TD itself could be unacceptably large. (See following plots.)

Recall: NIEL Dose with 3000/fb near end of ID: Z=344-348cm R=5-70 cm All Options – EC Bpoly, HGTD, etc. Black – Baseline Red – sFCal Plug3 Green – NoECPoly All other colors are HGTD options These are all the ratios for the various HGTD options studied here. 32

NIEL Dose with 3000/fb inside the HGTD: Z=348-352cm R=5-70 cm Black – Baseline Red – sFCal Plug3 Green – NoECPoly All other colors are HGTD options These are all the ratios for the various HGTD options studied here. 33

Ionizing Dose [Gy/3000/fb] – HGTD WTD TD10 Full 5cm Moderator ATLAS Baseline HGTD Preferred Option ID ID FCal FCal The ionizing dose in the inner detector is little affected by the HGTD. The material in the preshower does move the TID contours forward at the inner EMEC.

TID at 3000/fb near end of ID: Z=344-348cm R=5-70 cm All Options – EC Bpoly, HGTD, etc. Black – Baseline Red – sFCal Plug3 Green – NoECPoly All other colors are HGTD options These are all the ratios for the various HGTD options studied here. 35

TID at 3000/fb inside the front of the HGTD: Z=348-352cm R=5-70 cm Black – Baseline Red – sFCal Plug3 Green – NoECPoly All other colors are HGTD options These are all the ratios for the various HGTD options studied here. 36

Conclusions and Suggestions from Preliminary Studies of Rates and Doses from HGTD Options Any HGTD option should include 5 cm of Bpoly on the front of the HGTD. The only region that appears to be influenced by an HGTD with tungsten preshower is the EMEC near its inner radius. It’s backgrounds shift forward, closer to the HGTD, but it is not clear that the EMEC’s performance is affected. This would require particle response simulations, of the HGTD and EMEC in tandem. -> The VI beampipe will need to be updated again if the 3-segment scheme is adopted. -> Accurate studies of inner detector rates cannot go forward until the ITk design is finalized, and translated into simulation geometries. -> The NIEL and TID doses at the inner radius of the TD (10 cm) and WTD (28 cm) are quite high at 3000/fb. Hopefully irradiation studies of the electronics and sensors can determine their viability.

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: http://atlas.physics.arizona.edu/~shupe/Cavern_Backgrounds_Phase2/ Select Study (list on next slide): then FLUXPLOTS or FLUXTEXTS Available doses and particle fluxes: Detector impact: energy deposition, NIEL dose, ionizing dose, hadrons > 20 MeV, SEU rates, star densities (for activation). Particles: total neutrons, neutrons > 100 keV, thermal neutrons, photons, electrons, protons, charged pions, muon single particle detector rates. 38 38

Subdirectories Used for ATLAS Base and HGTD Studies Baseline ATLAS with New beampipe and NSW, and two options: Phase2_NBP_NSWA_Baseline_14TeV Phase2_NBP_NSWA_Baseline_NoECModr_14TeV Phase2_NBP_NSWA_Base_sFCal_Plug3_14TeV HGTD Options (M5 means 5cm Bpoly) HGTD_Plate_Geom_WTD28cmRi WTD, no M5 HGTD_Plate_Geom_WTD28cmRi_5cmModr WTD, with M5 HGTD_Plate_Geom_WTD28cmRi_TD10cmRi WTD+TD10, no M5 HGTD_Plate_Geom_WTD28cmRi_TD10cmRi_5cmModr WTD+TD10, only WTD M5 HGTD_Plate_Geom_WTD28cmRi_TD10cmRi_5cmModF WTD+TD10, WTD+TD M5 HGTD_Plate_Geom_WTD5cmRi WTD+TD5, no M5 39 39