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

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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 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

Intrinsic Neutron Rate from Detector Materials and Cryostat (Requirements)

External moderator

• nly partially useful

for this

=> Tighten Up Radon Requirement by Factor 10

(should be achievable with reasonable means)

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Old (10 mBq/kg Rn-222): 40 mBq/kg a-activity uniformly distributed in LAr to account for 4 subsequent a- decays of Rn-222 to quickly check on origin of MicroBooNE background (Gleb Sinev) New (1 mBq/kg Rn-222): 4 mBq/kg a-activity uniformly distributed in LAr to account for 4 subsequent a- decays of Rn-222 (=> 1000 uBq/kg Rn-222) (will also mitigate new background 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)

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Gamma-, Alpha- and Beta-Ray Spectrometers at SD Mines for Radiological Assays

Large, Fast Loading and Versatile Gamma-Ray Spectrometer (BEGe) Large Alpha-, Beta-Ray Spectrometers (big AlphaBACH and portable AlphaBACH) Uniquely large volume AND meeting world’s best sensitivity!

RABBIT:

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Measuring Samples for Gamma-Ray Assays with RABBIT

125 ml bottles of cement, fly ash, sand, gravel, water, Cu-getter, molecular sieve Steel samples Geant4 simulations

• f each sample with

Ge-detector geometry

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Geant4 Simulated Detection Efficiencies (e.g. Steel Samples)

=> U-238 => Rn-222 => Th-232 => Th-232

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More than 24 Samples Assayed with RABBIT in one month

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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)

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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)