Presentation on theme: "Thesis Proposal August 24, 2011. IGY MonitorStandard NM64 (1964) Developed to WHAT IS A NEUTRON MONITOR (NM)? (International Geophysical Year) Design."— Presentation transcript:
IGY MonitorStandard NM64 (1964) Developed to WHAT IS A NEUTRON MONITOR (NM)? (International Geophysical Year) Design by Simpson (1948) Design by Hatton and Carmichael The efficiency of neutron counters to record evaporation neutrons produced in The lead of a monitor increased from 1.9% for the IGY to 5.7% for the NM64, an increase of 3.3 times the counting rate per unit area of lead producer. The efficiency of neutron counters to record evaporation neutrons produced in The lead of a monitor increased from 1.9% for the IGY to 5.7% for the NM64, an increase of 3.3 times the counting rate per unit area of lead producer.
BARE Detection Method: Older type-proportional counter filled with BF 3 : n + 10 B + 7 Li Newer type-proportional counter filled with 3 He: n + 3 He p + 3 H A large instrument, weighing 32 tons (18 tube NM64 is “supermonitor”) Detects secondary neutrons generated by collision of primary cosmic rays with air molecules. NM64 CHARACTERISTIC OF NEUTRON MONITOR Image Credit: PSNM station at Doi Inthanon, Chiang Mai, Thailand
Image Credit : Paul Evenson, January 2009 NEUTRON MONITOR PRINCIPLE An incoming hadron interacts with a nucleus of lead to produce several low energy neutrons. These neutrons thermalize in polyethylene or other material containing a lot of hydrogen Thermal neutrons cause fission reaction in a 10 B ( 7 Li + 4 He) or 3 He ( 3 H + p) gas proportional counter. The large amount of energy released in the fission process dominates that of all penetrating charged particles. There is essentially no background. 5
Geomagnetic cutoff rigidity; Pc are a quantitative measure of the shielding provided by the earth’s magnetic field, was estimated from Rigidity; P is a concept used to determine the effect of particular magnetic fields on the motion of the charged particles. It is defined as Early period: geomagnetic-dipole moment Later period: the effect of the higher-order terms of the magnetic field Final period: numerical calculation of cosmic-ray orbits in the geomagnetic field WHAT ARE THE RIGIDITY AND CUTOFF RIGIDITY ? P = B ρ = p / q Rigidity Magnetic field Gyroradius of particle Momentum Charge Note: gyration depends on pitch angle
NEUTRON MONITOR LATITUDE SURVEYS Transportable Monitor Differential Response f n. Counting Rate G alactic cosmic ray spectrum geomagnetic T ransmission heliospheric M odulation Y ield function (not to scale) Assuming T as a box function, L is a limiting rigidity as a numerical convenience
THE WORLDWIDE NETWORK OF NM Image Credit : http://physik.uibk.ac.at
WHY USE A CALIBRATION NM? TO DERIVE DIFFERENTIAL RESPONSE FUNC. OR ENERGY SPECTRA Moraal et al. (2000) Fig 1. Example of expected differential response function for 11 inter-calibrated neutron monitors. dN/dP = differential response f n. P c1 = cutoff rigidity at location 1 P c1 = cutoff rigidity at location 2 N(P c1 ) = count rate at P c1 N(P c2 ) = count rate at P c2
a = LND25382, 51 mm in diameter c = lead producer with diameters 101 and 193 mm b = polyethylene(PE) moderator with inner d = reflector with diameters 194 and 350 mm and outer diameters of 60.5 and 99.5 mm The name of Calibrator is “CALMON”
COUNTS BAROMETRIC PRESSURE HIGH VOLTAGE TEMPERATURE GPS CO-ORDINATES GPS ALTITUDE WHAT THE SYSTEM RECORDS ? Image Credit: PSNM station at Doi Inthanon, Chiang Mai, Thailand
2.1To compare count rates of the calibration monitor under various conditions. The residual uncertainties in the intercalibration are mainly due to (a)Different responses to primary intensity variations of NM of different design. (b)Different atmospheric (pressure and temperature) responses of the monitors. (c) Environmental differences due to the fact that the calibrator can usually not be transported to the identical environment of the stationary neutron monitor. Moraal et al. (2000) The calibration accuracy of Neutron Monitors needs to be within 0.2%. 2.2To determine the best method to characterize the evolution of the cosmic ray spectrum using data from the series of latitude surveys conducted from 1994 through 2007.
Calibration Procedure Ability to compare the cosmic ray intensity at any two sites with different cutoff rigidity and atmospheric depth. Latitude Surveys Derive useful differential response functions from the neutron monitor network. Develop optimal methods for extracting cosmic ray spectra from latitude surveys Provide correct information on how the solar cycle affects cosmic rays.
PRINCESS SIRINDHORN NEUTRON MONITOR Location: At Doi Inthanon, Chiang Mai, Thailand. Design: 18BP28-NM64 Altitude: 2,565 m above sea level Geographic Coordinates: 18.59 ๐ North 98.49 ๐ East Vertical cutoff rigidity: 16.8 GV at Chiang Mai Standard Pressure: 750.6 hPa (563 mmHg) Barometric Coefficient: -0.623%/hPa (-0.83%/mmHg) PRINCESS SIRINDHORN NEUTRON MONITOR Location: At Doi Inthanon, Chiang Mai, Thailand. Design: 18BP28-NM64 Altitude: 2,565 m above sea level Geographic Coordinates: 18.59 ๐ North 98.49 ๐ East Vertical cutoff rigidity: 16.8 GV at Chiang Mai Standard Pressure: 750.6 hPa (563 mmHg) Barometric Coefficient: -0.623%/hPa (-0.83%/mmHg) http://www.dfi.uchile.cl 4.1 THE CALIBRATION PROCEDURE AT PSNM STATION
Image Credit: PSNM station at Doi Inthanon, Chiang Mai, Thailand PRINCESS SIRINDHORN NEUTRON MONITOR SET UP THE CALIBRATION NEUTRON MONITOR ELECTRONICS HEAD from BARTOL RESEARCH INSTITUTE UNIVERSITY OF DELAWARE, USA from POTCHEFSTROOM CAMPUS NORTH - WEST UNIVERSITY, SA Original PSNM Station Modified PSNM Station (April 2010)
Test for stability and repeatability of the Calibrator with eliminating of environmental effects. Table 1. 15 configurations of the calibration procedure The Calmon data were put on the Doi Inthanon FTP. The URL is ftp://126.96.36.199/CalmonData/
Fig 2. The ratio of the count rates of the IGY and calibration neutron monitor as function of the height of the calibration neutron monitor above a concrete Floor, with different amounts of water and brick underneath the calibrator. Krüger et al. (2010)
Determine a normalization factor for the count rate of the stationary neutron monitor relative to the others in the world-wide network.
Preliminary Results report in International Cosmic Ray Conference (ICRC), Beijing 2011 Fig 3. The ratio of the count rates of the Potchefstroom NM (open circles) and the NM at Doi Inthanon as Function of varying heights of water beneath the calibrator. 1 st experiment Performed in Potchefstroom, SA 2 nd experiment Performed in Kiel, GE [from March to May, 2008] 3 rd experiment Performed in Doi Inthanon, TH [from Nov, 2009 to Jun, 2010] Decrease 1.56% [Doi Inthanon 140 cm] Decrease 4.2% [Doi Inthanon 70 cm] Decrease 4.0% [Potchefstroom] The counting decreases with an increase in the amount of water, and the counting rate levels off when the water level 30 cm
To quantify the calibration process, consider two NMs at different cutoff rigidities and altitudes, with different efficiencies (due to difference in type of neutron monitor, number of counters, and different environment). Suppose NM1 is calibrated against the calibrator at time t 1, and similarly NM2 at time t 2. Then we have the following five measurements: At time t 1 the counting rate (cr.) of NM1 is N 1,1 At time t 2 the cr. of NM1 is N 1,2 At time t 2 the cr. of NM2 is N 2,2 At t 1 the cr. of the calibrator at NM1 is C 1,1 At t 2 the cr. of the calibrator at NM2 is C 2,2 At time t 2 the counting rate of the calibrator at NM1 can then be calculated as C 1,2 = (N 1,2 /N 1,1 )*C 1,1. Determine the ratio of efficiency of the two NMs. The measured ratio of the two NMs at time t 2 The measured ratio of the calibrator counts at the two positions. NM calibrator calculation measurement
Table 2. Hourly counting rates during the calibrations Table 3. Characteristics, barometric coefficient, and efficiency ratio of each NM relative to the Potchefstroom NM. Preliminary Results report in International Cosmic Ray Conference (ICRC), Beijing 2011
U.S. Coast Guard icebreakers, the Polar Sea or the Polar Star carry a Neutron monitor standard 3-NM64 4.2ANALYZE THE DATA FROM A SHIP-BORNE MONITOR WITH THREE COUNTER TUBES. Made trips across the Pacific ocean from Seattle to Antarctica and back, over a wide range of cutoff rigidities, over 1994 to 2007. U.S. Coast Guard icebreakers Fig 4.
The latitude survey data were put on the Bartol FTP. The URL is as follows: ftp://ftp.bartol.udel.edu/pyle/OtherData/LatSurvSegments/ Part of the listing: … A: S(eattle)-C(utoff)E(quator) B: CE - M(cMurdo) C: M - CE D: CE - S. The format is as follows: YY/MM/DD HH:MM:SS Vcutoff Rate1 Rate2 … Download and analyze the latitude survey data. Fig 5. Sample fit of a segment’s data to a Dorman function, along with the corresponding derivative Bieber et al. (2003) Latitude or Longitude changed by greater than 0.002 degrees during the hour (>0.14 miles/hour)
Fig 6. Data (left) and model fit (Right) to the moderated neutron detector latitude survey. Yield Function - This term is due to the energy dependence of the neutron production and expresses the x-dependence of Y in high-energy region - This term expresses the decrease of the production mainly due to the decrease of the number of effective nucleons in the atmosphere with the increase of x and with the decrease of u Characterize Cosmic Ray Spectra. [Nagashima et al (1989)] u = U/U 0 U = the total energy U 0 = the rest energy ------------------------- x = pressure in mbar (atmospheric depth)
Fig 7. Residuals (counts/second) from the fit shown in Figure 6 as a function of geomagnetic cutoff.
NumberDetailsTime periodMonth 1.Theoretical study and reviews 6 monthsNovember 2010-May 2011 2.Data analysis9 monthsMay 2011-Febuary 2012 3.Data characterization and synthesizing existing and/ or new concepts 8 monthsOctober 2011-June 2012 4.Interpretation9 monthsJune 2012-March 2013 5.Writing thesis6 monthsMarch 2013-September 2013
RGJ ScholarshipPSNMMahidol U. Prof. David Ruffolo Prof. Paul Evenson Dr. Alejandro Sáiz Space Physics and Energetic Particles Group
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Image Credit: Clem et al. (1997) Apparent Cutoff is a new method for calculating geomagnetic cutoffs that incorporates obliquely incident primaries, using it to interpret a sea level neutron monitor latitude survey. Stoker (1995) suggested that oblique particles might also be responsible for anomalies in neutron monitor latitude surveys.
Fig 3. (a) The ratio of the count rates of the Pochefstroom neutron monitor (IGY) and Calibrator as function of thickness of absorbing material underneath the calibrator, with the calibrator in an enclosed building. The calibrator was kept at a fixed height of 40 cm above the floor. (b) The same ratio as function of height on the open roof of building, while the calibrator was kept immediately above the water level; (c) a repetition of (b) on ground level far removed from any building. 3.5% decrease in the count rate, reaching a minimum for an amount of 30 g/cm 2 of moderator/absorber. The decrease in the count rate with an increase in the amount of water beneath the calibrator is 5.3%, with the saturation point at 20. The count rate decreased by 3.8%, but it saturated again at 20 cm. Krüger et al. (2010)
Rigidity P (GV) Pairs of response functions at 11 and 22 year intervals illustrate the “spectral crossover” effect
1.Dowload the data from ftp://188.8.131.52/CalmonData/ftp://184.108.40.206/CalmonData/ 2.Calculate the values of fracDOY, Count/hour, N, Tave, pave File name: secselhour