1 / 13

ANITA neutron source

ANITA neutron source. Characteristic measurements with activation detectors. Measurement requests. The homogeneity of the neutron beam Low-energy neutrons in the neutron beam Protons in the neutron beam Positions “user2” and “user3” (positions 6 and 12 m from the target). Activation method.

rowena
Download Presentation

ANITA neutron source

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. ANITA neutron source Characteristic measurements with activation detectors

  2. Measurement requests • The homogeneity of the neutron beam • Low-energy neutrons in the neutron beam • Protons in the neutron beam • Positions “user2” and “user3” (positions 6 and 12 m from the target)

  3. Activation method • Monoisotopic materials • Al, Au, Bi, Ta, natCu • ca. 1g of material – 10^8 neutrons • Irradiation (8h of 350 nA beam) • Gamma spectra measurements (days after) • Analysis of spectra

  4. Detectors positions cross of detectors + Cu detector user2, user3 positions (6m, 12m) collimator for LE neutrons concrete wall

  5. Irradiation

  6. Measurements

  7. Results • Neutron beam uniformity: • No non-homogeneity out of the limits of statistical error ~ 5% • Low-energy neutrons: • Present in all foils, less near the wall ? • Spectrum cannot be determined from our data • Extra positions: • “user2” - 6 m : 4x less LE neutrons than at “user1”, 7x less 196Au, 3x less 194Au (196Au, 194Au not reliable, close to detectable limits) • “user3” - 12 m : 8x less LE neutrons, others not detected, upper limit for 196Au ~ 7x less

  8. Protons in neutron beam I • Protons are monitored by the reactions in natCu: • 63Cu(p,n)63Zn • 63Cu(p,2n)62Zn • No traces of Zn isotopes were found in the Cu detector • The amount of 63Zn and 62Zn ca. 10x lower than the amount of 61Cu would be detected • 61Cu was well detected • 63Zn and 62Zn lines should have more that 3s*resolution counts ~ 200 counts • 200 counts corresponds to 10x lower amount of Zn comparing to 61Cu

  9. Calculations • Neutron (and proton) spectra can be simulated: • MCNPX • FLUKA (can simulate also in magnetic field) • Simplified target was used in simulations • Cross-sections are taken from TALYS and verified against values from EXFOR (agreement is good enough for our estimations) • The spectrum multiplied with appropriate cross-sections = the amount of produced radioisotope • Absolute and relative comparison

  10. Simulated spectra • Shapes (FLUKA, MCNPX and preliminary spectrum – same shape, but different absolute values, because of simplified target, distance-detector target) • Relations between n and p spectra (there is in total 1000x less p than n) • Magnetic field - no noticeable difference

  11. Protons in neutron beam II • Simulated p and n spectra (MCNPX) are convoluted with xs for 62Zn and 61Cu • Result: 100x less 62Zn than 61Cu, this is 10x lower than our detection limit (10x, slide Protons – part 1) • We experimentally set the upper limit for the proton spectrum to 10x higher values than was simulated (1 proton per 100 neutrons):

  12. Experiment / calculation • Average value of exp/sim : 1.64 • Causes of discrepancies are: • Simplified simulation • Cross-sections • Systematic errors

  13. Conclusion • Measurements with activation detectors showed that ANITA neutron source meets all requirements for a good neutron source: • Homogenous neutron beam • LE neutron background measured (simulations for understanding) • Low proton background (at least 100x less protons than neutrons) • Relative neutron intensities in positions at 6 m and 12 m were measured (LE neutrons measure reliably, for 196Au and 194Au some upper estimations were set) • Calculated spectra convoluted with cross-sections give acceptable production rates – the shape of the real spectrum (10-100 MeV) is determined • Magnetic field in simulation does not change the results (codes MCNPX and FLUKA are both usable)

More Related