SD Mines Results of Radiological Assays of Shotcrete & Cryostat - PowerPoint PPT Presentation

SD Mines Results of Radiological Assays of Shotcrete & Cryostat Materials for DUNE Juergen Reichenbacher Layne Tieszen (undergrad), Madan Timalsina (LZ grad), James Haiston (DUNE grad) South Dakota School of Mines & Technology (SDSMT) DUNE Far Detector Backgrounds Task Force Meeting Aug 23, 2019

Intrinsic Neutron Rate from Detector Materials and Cryostat (Requirements) U-238 w/ SF factor of 5.45e-5 Mass I-Beam max: 9,500 kg x 40 x 4 sides = 1.52 ktons  83 Hz Neutron Rate with 1 Bq/kg of U-238 (and just 1 neutron per fission enters)  Requirement (<10 Hz): 0.1 Bq/kg External moderator only partially useful for this Mass APA steel frame max: 0.5 ton x 150 APAs = 75 tons  8 Hz Neutron Rate with 1 Bq/kg of U-238 (and 2 neutrons per fission contained)  Requirement (<10 Hz): 1.2 Bq/kg Mass CPA (3 mm thick FR4): 0.3 cm x 1.85 g/cm^3 x 12 m x 60 m x 2 =  0.9 Hz Neutron Rate with 1 Bq/kg of U-238 (and 2 neutrons per fission contained)  Requirement (<10 Hz): 11 Bq/kg 6/17/19 Juergen Reichenbacher (SDSM&T) 2

=> Tighten Up Radon Requirement by Factor 10 (should be achievable with reasonable means) New (1 mBq/kg Rn-222): Old (10 mBq/kg Rn-222): 4 mBq/kg a -activity uniformly 40 mBq/kg a -activity uniformly distributed in LAr distributed in LAr to account for 4 subsequent a - to account for 4 subsequent a - decays of Rn-222 decays of Rn-222 (=> 1000 uBq/kg Rn-222) to quickly check on origin of MicroBooNE background (Gleb (will also mitigate new background Sinev) 40Ar(alpha, gamma) -> Dan Pershey’s Light and Charge Cluster Trigger Studies)  Emanation QA and QC much more important now (for comparison LZ’s radon requirement is 20 mBq in 10 tons = 2 uBq/kg) 6/17/19 Juergen Reichenbacher (SDSM&T) 3

Gamma-, Alpha- and Beta-Ray Spectrometers at SD Mines for Radiological Assays RABBIT: Large, Fast Loading and Versatile Large Alpha-, Beta-Ray Spectrometers Gamma-Ray Spectrometer (BEGe) (big AlphaBACH and portable AlphaBACH) Uniquely large volume AND meeting world’s best sensitivity! 6/17/19 Juergen Reichenbacher (SDSM&T) 4

Measuring Samples for Gamma-Ray Assays with RABBIT 125 ml bottles of Steel samples cement, fly ash, sand, gravel, water, Cu-getter, molecular sieve Geant4 simulations of each sample with Ge-detector geometry 6/17/19 Juergen Reichenbacher (SDSM&T) 5

Geant4 Simulated Detection Efficiencies (e.g. Steel Samples) => Rn-222 => Th-232 => Th-232 => U-238 6/17/19 Juergen Reichenbacher (SDSM&T) 6

More than 24 Samples Assayed with RABBIT in one month 6/17/19 Juergen Reichenbacher (SDSM&T) 7

Identified Local Companies for Shotcrete & Concrete Work for DUNE FD and Tracked Down Their Supply Chain and Obtained Samples - GCC Cement Plant (Rapid City): Portland cement with rock from local RC quarry, fly ash (coal firing plant in NB) - Pete Lien (Rapid City): GCC cement, fly ash (coal firing plant in NB), gravel (RC quarry), sand (near Uranium-Mine) - TCC (Rapid City): GCC cement, fly ash (coal firing plant in NB), gravel (South America), sand (packaged) - Croell (Spearfish): GCC cement, fly ash (coal firing plant in NB), gravel (Sundance), sand (near Uranium-Mine) - ProtoDUNE Cu-getter & molecular sieve (zeolite) -> Stephen Pordes, David Montanari - ProtoDUNE Steel (I-beams) and SS cryo-wall -> Filippo (Luxembourg corp.) - Industrial and sump water from SURF (Davis 4850 ft) 6/17/19 Juergen Reichenbacher (SDSM&T) 8

Most Important Concerning Results from Assays: - Molecular sieve (zeolite) is high: (20.86 +/- 1.61) Bq/kg in Ra-226 could translate into ~100 mBq/kg of Rn-222 (if all radon emanates into LAr, requirement is 1 mBq/kg => measure cold emanation!) - Steel of I-beams is high: (4.15 +/- 1.59) Bq/kg in U-238 translates into 344 Hz of neutron rate! But signs of stratification during manufacturing process (Ra-226 out of equilibrium) => sample steel coupons from different heights in smelt (-> Dimitar, Filippo) 6/17/19 Juergen Reichenbacher (SDSM&T) 9