Neutron background expectation Simon JM Peeters - - PowerPoint PPT Presentation

▶
neutron background expectation
SMART_READER_LITE
LIVE PREVIEW

Neutron background expectation Simon JM Peeters - - PowerPoint PPT Presentation

Aug 05, 2023 209 likes •364 views

Neutron background expectation Simon JM Peeters s.j.m.peeters@sussex.ac.uk JT DAQ Physics Performance WG 2019.11.21 In G4: ENDF Data Base, Neutron capture in LAr slightly different (worse) n + 40 Ar 41 Ar * : dominant n + 36 Ar 37 Ar *

slide-1
SLIDE 1

Neutron background expectation

Simon JM Peeters s.j.m.peeters@sussex.ac.uk JT DAQ Physics Performance WG 2019.11.21

slide-2
SLIDE 2

Neutron capture in LAr

Hardell, R. and Beer, C., 1970. Thermal Neutron Capture in Natural Argon. Physica Scripta, 1(2-3), p.85.

n + 40Ar 41Ar* : dominant n + 36Ar 37Ar* Radiative neutron capture on Argon results in an excited atom

  • f the next heaviest argon

isotope. The excited argon isotopes de- excite with very specific total energy: 6.1 MeV for 41Ar, 8.8 MeV for 37Ar. This energy is carried away by at least one photon on the case of

37Ar and at least two photons in

the case of 41Ar.

=0.978 In G4: ENDF Data Base, slightly different (worse)

2019.11.21 Simon JM Peeters | Neutrons in DUNE | DAQ PPWG 2

slide-3
SLIDE 3

Low energy events

2019.11.21 Simon JM Peeters | Neutrons in DUNE | DAQ PPWG 3

Neutron capture

  • n 40Ar:

   (Compton) See Pierre’s talk last time (and at/around CM): https://indico.fnal.gov/event/22378/contribution/0/material/slides/0.pdf e CC events

slide-4
SLIDE 4

Simulation moving to full G4!

Aran, Tyler & Pierre – more details & motivation, see (amongst other talks): https://indico.fnal.gov/event/21861/session/6/contribution/20/material/slides/0.pdf

2019.11.21 Simon JM Peeters | Neutrons in DUNE | DAQ PPWG 4

Brief update from Aran at the end

slide-5
SLIDE 5

Neutron transport

Effective neutron mean free path could be ~30 m! (ENDF: as currently in GEANT4)

October 8-20 beam run Result expected by the end of the year

2019.11.21 Simon JM Peeters | Neutrons in DUNE | DAQ PPWG 5

slide-6
SLIDE 6

ACED

2019.11.21 Simon JM Peeters | Neutrons in DUNE | DAQ PPWG 6

arXiv:1902.00596

slide-7
SLIDE 7

Background workshop was held at CERN in June

https://indico.fnal.gov/event/20996/other-view?view=standard Report by review committee has been distributed but not published yet (?)

2019.11.21 Simon JM Peeters | Neutrons in DUNE | DAQ PPWG 7

slide-8
SLIDE 8

Overview

2019.11.21 Simon JM Peeters | Neutrons in DUNE | DAQ PPWG 8

Dominant (large mass):

  • Rock (238U/232Th)
  • Shotcrete (238U/232Th)
  • Support structure (1.5 ktonne)

(238U/232Th/56Fe(,n)/54Fe(,n)) Subdominant (low mass/activity):

  • 222Rn in LAr: source of s:

40Ar(,n)

  • Insulation (glass fibre)

(238U/232Th)

  • Cryostat steel

(238U/232Th,56Fe(,n)/54Fe(,n))

  • TPC CuBe wires Be(,n)
  • APA steel / materials (238U/232Th)

Also: cosmogenically-generated neutrons. Subdominant in rate, but possibly high- multiplicity events! Arxiv:1811.07912

slide-9
SLIDE 9

PS: Workshop on (α,n) yield in low background experiments @ CIEMAT

Today / tomorrow https://agenda.ciemat.es/event/1127/overview Vidyo: https://agenda.ciemat.es/event/1127/page/14-remote-connection Code: 232238

2019.11.21 Simon JM Peeters | Neutrons in DUNE | DAQ PPWG 9

slide-10
SLIDE 10

Neutrons from the rock

DarkSide simulation (Paola Sala) (200 events / year / ton) * 10 * 10^3 tons / (3e7 sec / year) * • 18 [flux factor] * 10 [fiducialization factor] * • 3 [PUF foam moderation] * 3 [dead LAr shell extinction] = 108 neutrons / sec captured

(J Reichenbacher @ CM https://indico.fnal.gov/event/21445/session/16/contribution/172/material/slides/0.pdf)

in good agreement with: 104 Hz Aran Borkum, DUNE LArSoft (Geant4) 81 Hz Beacom et al (FLUKA) We expect a factor 3 shielding from insulation, so around: 30 n/s

slide-11
SLIDE 11

Support structure

  • Mass of I-beam structure: 1.52 ktonne

protoDUNE sample: 4.15  1.59 Bq/kg in 238U

(J Reichenbacher, SDSM&T, https://indico.fnal.gov/event/21625/contribution/0/material/slides/0.pdf)

238U fission, 56Fe(,n) & 54Fe(,n):

O(10) Hz

(J Reichenbacher, SDSM&T, https://indico.fnal.gov/event/22323/contribution/0/material/slides/0.pptx)

Stratification during manufacturing process (226Ra out of equilibrium): sample steel coupons from different heights in smelt

2019.11.21 Simon JM Peeters | Neutrons in DUNE | DAQ PPWG 11

slide-12
SLIDE 12

Radon in LAr

2019.11.21 Simon JM Peeters | Neutrons in DUNE | DAQ PPWG 12

Vitaly (SOURCES4A): For 238U+235U chains in equlibrium the (,n) yield: 1.46*10-10 n/g/s/ppb Radon and below: 1.37*10-10 n/g/s/ppb For 232Th chain in equilibrium: 8.71*10^(-11) n/g/s/ppb. Even for worst case, we expect: < 1 n/s. ((alpha,gamma) 13 gammas/day)

(J Reichenbacher, SDSM&T, https://indico.fnal.gov/event/22323/contribution/0/material/slides/0.pptx)

slide-13
SLIDE 13

CuBe wires (preliminary)

2019.11.21 Simon JM Peeters | Neutrons in DUNE | DAQ PPWG 13

Preliminary measurement at Boulby (David Waters): 3 Bq/kg 616.9 kg in one module. Vitaly (SOURCES4A) has provided expected (,n) yield: again, much below 1 n/s

slide-14
SLIDE 14

Conclusions

  • Neutron rate is important and therefore we need to understand

this in detail, measure the relevant activities in materials, and put in controls where we can.

  • Dominant sources are the rock, shotcrete and the I-beam steel.
  • Many other materials, we suspect subdominant, but assays are

underway.

  • Full geometry simulations are underway to assess further the

effect/use of any shielding.

2019.11.21 Simon JM Peeters | Neutrons in DUNE | DAQ PPWG 14