Neutron detector response functions

Responses of Bare Neutron Counters to Cosmic Rays During 1995 and 2009 Latitude Surveys

W. Nuntiyakul*,1,2, P.-S. Mangeard 3, A. Saiz 4, D. Ruffolo 4,2, P. Evenson 3, J.W. Bieber 3, J. Clem 3, A. Hallgren 5, J. Madsen 6, R. Pyle 7, M. L. Duldig 8, J. E. Humble 8, and S. Tilav 3
1 Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand
2 National Astronomical Research Institute of Thailand (NARIT), Chiang Mai 50180, Thailand
3 Bartol Research Institute and Department of Physics and Astronomy, University of Delaware, Newark, DE 19716, USA
4 Department of Physics, Faculty of Science, Mahidol University, Bangkok 10400, Thailand
5 Department of Physics and Astronomy, Uppsala University, Uppsala 75120, Sweden
6 Wisconsin IceCube Particle Astrophysics Center, University of Wisconsin-Madison, Madison, WI 53703, USA
7 Pyle Consulting Group, Inc., St. Charles, IL 60174, USA
8 School of Natural Sciences, University of Tasmania, Hobart, Tasmania 7001, Australia
* Presenting author

Ground-based neutron counters are a standard tool for detecting atmospheric showers from GeV range primary cosmic rays of either solar or galactic origin. Bare neutron counters, a type of lead-free neutron monitor, function much like standard neutron monitors but have different yield functions primarily because they are more sensitive to neutrons of lower energy. When operated together with standard monitors, the different yield functions allow estimates to be made of the energy spectrum of galactic or solar particles. At any given location, the magnetic field of the Earth excludes particles below a well-defined rigidity (momentum per unit charge) known as the cutoff rigidity, which can be accurately calculated using detailed models of the geomagnetic field. By carrying a neutron detector to different locations, e.g., on a ship, the Earth itself serves as a magnet spectrometer.

We will present the responses to cosmic rays of bare neutron counters operated on board a ship during 1995 and 2009 survey years over a wide range of magnetic latitude, that is, a latitude survey. In the 1995 survey, we carried an NM64 neutron monitor with three counter tubes, that is, a 3NM64, together with three bare neutron detectors. In the 2009 survey, two bare neutron detectors were operated on a ship where they ultimately were installed at the South Pole in 2010 to operate together with 3NM64 there. This study is supported in part by the Thailand Science Research and Innovation via Research Team Award 6280002 and Research Grant for New Scholar MRG6280155 and the U.S. National Science Foundation Awards OPP0838838, PLR-1245939, and PLR1341562.

Presentation


Variability of effective cutoff rigidities for neutron monitors during 1950 - 2050

Lev Dorman (a, b), Anatoly Belov (a), Evgenia Eroshenko (a), Raisa Gushchina (a), Lev PustilÕnik (b), and Victor Yanke (a)
(a) Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation, Russian Academy of Sciences, IZMIRAN, Moscow, Russia, 108840.
(b) Cosmic Ray and Space Weather Center of Tel Aviv University, Ariel University, Shamir Research Institute & Israel Space Agency with E. Segre Observatory on Mt. Hermon, ISRAEL

Presenting author, Lev Dorman

Modern development of the experiment requires more rigorous studies of magnetospheric effects in terms of both the duration of observations and the accuracy of the experimental data. This is associated, for example, with the fact that the geomagnetic field has decreased by about 4% for the more than sixty-year period of cosmic ray observations, and it decreases at a different rate in different regions. Impresses that the contribution of high harmonicas of the geomagnetic field for this period, on the contrary, increased by about 30%. Besides, magnetic anomalies have the common tendency to a drift to the west and to equator with an average speed of ? 0.15 ¡/year. For practical purposes to estimate consequences of such big reorganization of a magnetic field from the point of view of magnetospheric effects of cosmic rays, it is necessary to receive planetary distributions of effective geomagnetic cutoff rigidities for network of neutron monitor stations for each year and estimate the expected century variations of CR neutron component caused by geomagnetic variations.

Presentation


Comparison between the observed and the computer modeled neutron monitor count rates.

Danislav Sapundjiev, Royal Meteorological Institute of Belgium, KMI-IRM (speaker)
Stanimir M. Stankov, Royal Meteorological Institute of Belgium, KMI-IRM

Understanding the neutron monitor observations (its count rate) and the relation to the particle intensities in the space and atmospheric radiation environments is necessary for the application and use of these instruments for space weather research. The principal processes are the neutron production and diffusion within the atmosphere and within the different components of the neutron monitor. A unique opportunity to understand the theory of the neutron monitors presented itself during the construction of the second neutron monitor in Dourbes(Belgium). Given the available modern computational techniques and the recorded measurements during the construction phases we modeled the processes contributing to the count rate of the instrument. This work covers the first two stages of the construction - the assembly of the neutrons reflector and the installation of the lead producer. The results obtained from Monte-Carlo calculations of the modeled instrument compared with the corresponding observed count rates will be presented.

Presentation


FLUKA Simulation of Neutron Detector Responses in Latitude Surveys to Vertical Secondary Particles from Cosmic Rays

W. Nuntiyakul*,1,2, A. Pagwhan 3, K. Fongsamut 1, P. Jiang 4, P.-S. Mangeard 5, A. Saiz 6, D. Ruffolo 6,2, P. Evenson 5, K. Munakata 7, J. Madsen 8, P. Chuanraksasat 2, B. Soonthornthum 2, S. Komonjinda 1, and R. Macatangay 2
1 Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand
2 National Astronomical Research Institute of Thailand (NARIT), Chiang Mai 50180, Thailand
3 Graduate School, Chiang Mai University, Chiang Mai 50200, Thailand
4 Polar Research Institute of China, Pudong, Shanghai 200136, China
5 Bartol Research Institute and Department of Physics and Astronomy, University of Delaware, Newark, DE 19716, USA
6 Department of Physics, Faculty of Science, Mahidol University, Bangkok 10400, Thailand
7 Department of Physics, Faculty of Science, Shinshu University, Nagano 390-8621, Japan
8 Wisconsin IceCube Particle Astrophysics Center, University of Wisconsin-Madison, Madison, WI 53703, USA
* Presenting author

In the standard neutron monitor (NM64) design, there are lead rings to generate evaporation neutrons that are moderated by polyethylene before being detected in the neutron-sensitive proportional counter. A proportional counter without the lead, sometimes called a “lead-free” or “bare” counter, responds to lower energy particles on average and can be used in conjunction with an NM64 to estimate the energy spectrum of the primary cosmic rays. The objective of this work is initially to refine the understanding of the lead-free neutron monitor operation in latitude surveys using FLUKA Monte-Carlo simulations. Simulation of the responses to neutrons and other atmospheric particles, accounting for the dead time, will also be reported. This study is supported in part by the Thailand Science Research and Innovation via Research Team Award 6280002 and Research Grant for New Scholar MRG6280155.

Poster


Calculations of the sensitivity of the SEVAN network to galactic and solar cosmic rays

M.Zazyan, A.Chilingarian
Artem Alikhanyan National Lab (Yerevan Physics Institute) Armenia

To understand the sensitivity of the new type of particle detectors to the highest energy solar ions we investigate the response of the SEVAN basic units to galactic and solar protons. The hard spectra of solar ions at highest energies (−4 to −5 at rigidities of ≈10 GV) indicate the upcoming very intense solar ion flux with rigidities >50MV, very dangerous for satellite electronics and astronauts. Our calculations demonstrate that with the SEVAN network it will be possible: – Probe different populations of primary CR from 7GV up to 20–30GV; – Reconstruct SCR spectra and determine position of the spectral “knees”; – Classify GLEs in “neutron” or “proton” initiated events.

Poster


Study of multiplicity at the Antarctic high-altitude double neutron monitor DOMC and DOMB: atmospheric vs. instrumental cascades

M. Similä* (1), S. Poluianov (1,2), I. Usoskin (1,2)
(1) Sodankylä Geophysical Observatory, University of Oulu, Finland
(2) Space Physics and Astronomy unit, University of Oulu, Finland
* Presenting author

A pair of neutron monitors (NMs) is installed on the high Antarctic plateau, at the Concordia station (3200 m altitude) and measures the nucleonic component of nucleonic-muon-electromagnetic cascades induced by high-energy cosmic rays in the atmosphere. The installation includes two NMs: one, DOMC, is a standard mini-NM built using the NM64 design, and DOMB, which is a bare (lead-free) NM. Data acquisition system of both NMs records individual pulses in each detector making it possible to study the multiplicity (the number of registered pulses originated from the same cascade) of the NM counts. The multiplicity, related to the development of the atmospheric cascade can be evaluated from the bare NM DOMB, while the multiplicity measured by DOMC NM mostly reflects the internal cascade in the lead shield. We study the distributions of the multiplicity values in both NMs to show that they follow the expected exponential shape. The slopes have been analyzed in relation to the cosmic-ray variability. The data were obtained in the framework of the CRIPA-X (Academy of Finland) and LTCPAA (PNRA) projects.

Poster

Snow effect in neutron monitors

Dorman L.I. (1, 2), Belov A.V. (1), Dai U. (2), Eroshenko E.A. (1), Kobelev P.G. (1), Korotkov V. (3), Mavromichalaki H. (4), Pustilnik L.A. (2), Sternlieb A. (2), Trefilova K.A. (1), Yanke V.G. (1)
(1) IZMIRAN, Moscow, RUSSIA
(2) CR & SW Center with ESOI on Mt. Hermon, affiliated to Tel Aviv University, Ariel University, Shamir Research Unstitute, and Israel Space Agency, ISRAEL
(3) Magadan CR station, RUSSIA.4. Athens University, GREECE \

Presentation


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