Radiation Backgrounds in the ATLAS New Small Wheelatlas.physics.arizona.edu/~shupe/Cavern... · Phase2_NBP_NSWA_Baseline_14TeV, or Phase2_NBP_NSWA_SLACshie_14TeV Then select: FLUXPLOTS

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Radiation Backgrounds in the ATLAS New Small WheelErich Varnes and Michael Shupe, University of Arizona

July 17, 2016

The ATLAS Radiation Backgrounds Working Group is focusing on detectorsubsystem upgrades for high luminosity operation of the LHC in Phase 2.The Arizona group has long experience with the FCal region, the SmallWheel, and ATLAS radiation shielding. In tandem with other radiationbackgrounds groups at Sheffield, SLAC, and CERN, we are updating oursimulation geometries to match the detector revisions for Phase 2.At this point, we have updated the beamline (matching Sheffield),implemented a simple model of the New Small Wheel (NSW), and modifiedthe JD shielding. We have also implemented an improved version of theJD shield, with additional shielding disks, moderators, and Pb, following the latest SLAC geometry.In this report, we study the highest background rates and doses in the NSW for the initial JD design, and for the improved design from SLAC.

ATLAS Baseline Geometry vs JD Shield upgradeSLAC JD shields added

FCal JDFCal

NSW

Phase2 Baseline

JD

NSW

Added Shielding

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.

NIEL Dose [1 MeV equiv N/cm^2/3000/fb]: Base Geom vs JD Shield upgrade

The additional SLAC shielding pieces reduce the maximum rates and doses in the small wheels. The next slide shows the reduction of the dose.

SLAC JD shields added

FCal

JD

FCal

NSWPhase2 Baseline

JD

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NIEL Dose For 3000/fb In

First Wheel At

Inner Radius 94 cm

Black – Baseline

Red – SLAC JD shielding

Base JD: 1.95E14/cm^2SLAC JD: 5.94E13/cm^2

SEU Rates: Ppi>10MeV + N>2MeV [/cm^2/3000/fb]_In the NSW

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.

ATLAS 2013

FCal

JD

FCal

JD

ATLAS Baseline NSW NSWSLAC JD shields added

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SEU 2MeV Dose For 3000/fb In

First Wheel At Inner Radius 94 cm

Black – Baseline

Red – SLAC JD shielding

Base JD: 2.33E13/cm^2SLAC JD: 2.23E13/cm^2

Approximate Single Plane MM Counting Rates [kHz/cm^2] _In the NSW

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.

ATLAS 2013

FCal

JD

FCal

JD

ATLAS Baseline NSW NSWSLAC JD shields added

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From Run 1 data, the expected maximum hit rate is

15 kHz/cm^2.

For Phase 2, our hit

estimator will need to be retuned.

Single Plane Hit Rate In First Wheel

At Inner Radius 94cm

Black – Baseline

Red – SLAC JD shielding

Base JD: 58.6 kHz/cm^2SLAC JD: 15.2 kHz/cm^2

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Conclusions from Studies of Rates and Doses in the New Small Wheel, and Their Reduction with Added JD Shielding

Max dose reductions with SLAC geometry volumes added to the JD:* NIEL dose in the NSW is reduced by a factor of 3.3. Dose looks OK.* SEU dose is little reduced (1.04) since low energy particles are ignored.* Single-plane hit rates are reduced by 3.9. But at max they are close to

the design limit anticipated in the NSW TDR. Further study is needed.

Future studies:-> Detector responses to incoming particles need to be updated by

simulation or test beam measurements, to refine the estimation ofhit rates in new Phase 2 detectors.

-> The VI beampipe will need to be updated again if the 3-segmentscheme is adopted.

-> Final studies cannot go forward until the ITk design is finalized,and translated into simulation geometries.

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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.

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Location of files:

http://atlas.physics.arizona.edu/~shupe/Cavern_Backgrounds_Phase2/

Select Study:

Phase2_NBP_NSWA_Baseline_14TeV, or

Phase2_NBP_NSWA_SLACshie_14TeV

Then select: 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.

Files Used For Studies Presented Here

This report contains only a small fraction of the information comingfrom these simulations. All studied rates and doses are available atthe site below, in the subdirectories listed on the next slide.