1 / 30

Marek Zreda - Arizona Devendra Lal - Scripps John Clem - Bartol Darin Desilets - Arizona

Development of energy-dependent scaling for cosmic-ray neutron intensities and for in-situ cosmogenic nuclide production rates. Marek Zreda - Arizona Devendra Lal - Scripps John Clem - Bartol Darin Desilets - Arizona. Neutron measurements Neutron modeling Artificial chemical targets.

candy
Download Presentation

Marek Zreda - Arizona Devendra Lal - Scripps John Clem - Bartol Darin Desilets - Arizona

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Development of energy-dependent scaling for cosmic-ray neutron intensities and for in-situ cosmogenic nuclide production rates Marek Zreda - ArizonaDevendra Lal - ScrippsJohn Clem - BartolDarin Desilets - Arizona Neutron measurements Neutron modeling Artificial chemical targets

  2. Energy spectra for neutrons and nuclides

  3. Vertical cutoff rigidity (GV) for Epoch 1980

  4. Spatial variations of neutron intensity Important discovery Attenuation length in the air for neutrons depends on energy Dorman function for neutrons depends on energy

  5. Neutron Monitor

  6. polyethylene lead counter tube John Clem - http://www.bartol.udel.edu/~clem/nm/display/intro.html

  7. Arizona mobile neutron monitor

  8. Sample results from Arizona neutron monitor

  9. Bare counter (BC) tubes? Lower energy sensitivity

  10. Thermal neutron detector (counter) Specifications: Diameter 2.6 cm Length 39.2 cm Total pressure 1.03 MPa Voltage range 1100 - 1600 V Water resistance up to 8 m Background counting rate 6 cts/hr Counting rate on Mt. Lemmon, AZ (2788 m) 3830 cts/hr Counting rate in Tucson, AZ (667 m) 900 cts/hr

  11. Thermal neutron detector assembly

  12. Sample results from our neutron detector

  13. Comparison with previous models(attenuation lengths for high-energy and thermal neutrons)

  14. NM > 9 latitude surveys 2 comprehensive altitude/latitude surveys numerous NM stations BC 1 latitude survey 1 comprehensive altitude/latitude survey Current data

  15. Possible outcomes: • (1) All nuclides scaled by NM • (2) All nuclides scaled by BC • (3) Low-E interactions scaled by BC, • high-E scaled by NM • (4) Many scaling functions • Other results: • Angular sensitivity • E sensitivity • Neutron spectrum from NM • Muon sensitivity

  16. Attenuation length for production of 36Cl(lava-flow samples, Mauna Kea, Hawaii)

  17. Comparison of targets with geological samples Geological samples Targets Cosmic-ray intensity Estimated (from geological records) Known Exposure duration Determined (by geological dating) Known Exposure geometry Unknown (assessed, guessed) Known Exposure time Long Short Chemistry Complex Simple Expected accuracy Poor Good Expected precision GoodGood Other things ?????? ??????

  18. Proposed target experiments Primary objectives (1) To determine attenuation lengths for production of nuclides - at known magnetic cutoff rigidity - for low- and high energy reactions (2) To relate these to measured attenuation lengths for neutrons Secondary objective (3) To determine absolute production rates of selected other nuclides Primary objectives (1) To determine attenuation lengths for production of nuclides - at known magnetic cutoff rigidity - for low- and high energy reactions (2) To relate these to measured attenuation lengths for neutrons

  19. Experimental design matrix Hawaii, 13 GV California, 4 GV Target type O(n,x)10Be yes yes Primary 32S(n,p)32P yes yes Primary K(n,x)36Cl yes yes Secondary Ca(n,x) 36Cl yes yes Secondary Experimental design matrix Hawaii, 13 GV California, 4 GV Target type O(n,x)10Be yes yes Primary 32S(n,p)32P yes yes Primary K(n,x)36Cl yes yes Secondary Ca(n,x) 36Cl yes yes Secondary Proposed target experiments Objectives (1) To determine attenuation lengths for nuclide production (2) To compare with neutron attenuation lengths (3) To determine absolute production rates of selected other nuclides

  20. Selected targets - primary High-energy reaction: O(n,x)10Be t½ = 1.5 My Emed = 140 MeV Target: H2O (water) Concentration: 100% Target size: 100-200 kg Exposure time: >3 years Repeated exposure: no Measurement: AMS (Purdue) High-energy reaction: O(n,x)10Be t½ = 1.5 My Emed = 140 MeV Target: H2O (water) Concentration: 100% Target size: 100-200 kg Exposure time: >3 years Repeated exposure: no Measurement: AMS (Purdue) Low-energy reaction: 32S(n,p)32P t½ = 14.3 days Emed = 7 MeV Target: CS2 Concentration: 100% Target size: 10-15 L Exposure time: >2 months Repeated exposure: yes Measurement: Quantulus (Arizona)

  21. Selected targets - secondary Low-energy reaction: K(n,x)36Cl Emed = 13 MeV Target: KNO3 Concentration: 15% Target size: 20 kg Exposure time: >3 years Repeated exposure: no Measurement: AMS (Purdue) Low-energy reaction: K(n,x)36Cl Emed = 13 MeV Target: KNO3 Concentration: 15% Target size: 20 kg Exposure time: >3 years Repeated exposure: no Measurement: AMS (Purdue) Mid-energy reaction: Ca(n,x)36Cl Emed = 55 MeV Target: Ca(NO3)2 Concentration: 10% Target size: 40 kg Exposure time: >3 y Repeated exposure: no Measurement: AMS (Purdue)

  22. Field locations Hawaii - 13 GV: Mauna Kea & Mauna Loa: several secure locations (government facilities) between the summit (~4 km) and the saddle (~1.6 km) Why Hawaii: high magnetic cutoff rigidity large elevation span much neutron/nuclide data exist permanent neutron monitor (Maui) Hawaii - 13 GV: Mauna Kea & Mauna Loa: several secure locations (government facilities) between the summit (~4 km) and the saddle (~1.6 km) Why Hawaii: high magnetic cutoff rigidity large elevation span much neutron/nuclide data exist permanent neutron monitor (Maui) California - 4 GV: White Mountains: several secure locations (government facilities) between the summit (~4 km) and the Owens Valley (~1.6 km) Why California: low magnetic cutoff rigidity large elevation span close to Arizona and Scripps permanent neutron monitor (Climax)

More Related