NEUTRON MONITOR AT LOMNICKÝ ŠTÍT:BRIEF DESCRIPTION AND REVISED DATA FOR
12/1981-12/1999

K. Kudela, P. Bobik, V. Kollár, R. Langer, I. Strhársky, S. Štefánik

INSTITUTE OF EXPERIMENTAL PHYSICSSLOVAK ACADEMY OF SCIENCES, WATSONOVA 47,043 53 KOŠICE, SLOVAKIAKOŠICE, DECEMBER 2000

1. INTRODUCTION.
This report includes a short description ( chap. 2, p.3-7) of the device 8 NM 64 working at
Lomnický štít from December 1981 until present and the plots of the following data:monthly averages over the whole period (p. 8), daily averages in each year ( p. 9-13 ) andhourly values for each month separately (p 14-67). The data in digital form can beobtained at ultra.upjs.sk in pub/incoming/archiv/archivkk/LOMSTITARCHIV.
Lomnický štít Neutron Super Monitor of the Department of Space Physics, Institute ofExperimental Physics, Slovak Academy of Sciences, Košice is continually in operationfrom December 1981 when it replaced the older 4 NM 64 one. In part 3 the plots of therevised pressure corrected data for the period 12/1981-12/1999 are presented. The revisionwith respect to our earlier reports ( September 1993, May 1999) is due to two reasons.
First is the change of barometric correction coefficient (the correct one already included in
May 1999 report). Second is due to the checking of long term drift of the count rate of thesections A and B significant especially after July 1, 1993. This effect is now corrected byusing sections C and D of the monitor.
The percentages are here normalized to 100 % level reached in September 1986 andrepresenting 1,745.200 counts per hour. Data are obtained as sums of four sections
including the linear drift corrections of sections A and B. Gaps in the graphs indicate themissing data.
Main characteristics of Lomnický štít station:

Detector type
Geographic latitude
Geographic longitude
Cutoff rigidity
AltitudeMean barometric pressure
Barometric coefficient

SNM-1549.20 N
20.22 E
3.84 GV2634 m733.3 mb
0.72 % per mb

Address: Institute of Experimental Physics, Slovak Academy of Sciences, Watson str. 47,
043 53 Kosice, e-mail: kkudela@kosice.upjs.sk, tel. ++421 95 6224554,
fax ++421 95 6336292
In the following parts a short schematic description of the device (part 2, prepared mainlyby Vladimír Kollár) and the graphs of corrected data from Lomnický štít (part 3)are given.

22. DESCRIPTION OF THE NM- 64 COSMIC RAY MONITOR AT LOMNICKÝ
ŠTÍT.
The network consists from the three basical parts included in scheme of Fig.1:

Fig. 1: The block scheme of NM.

2.1. THE DETECTOR PART
It consists of the 8 BF3 neutron counters. The counters are proportional counters filled withboron trifluoride gas in whitch B10 isotope has been enriched to >90 per cent of the totalboron. The quantity of B10 in the effective volume of each counter should be aproximely 2.1 x1023 atoms. We have used former soviet union made type tubes CNM-15 (equivalent of NM64 tube.) The counters are instaled in polyethylen tube of wall with thickness 2 cm andoutside diameters 24 cm. The producer is of lead, of not less than 99.9 per cent purity in theform of cylinders 25 cm internal diameter and 35 cm outside diameter surround each of thecounter. The cylinders are spaced apart 50 cm betwen centers. The lenght of each cylinder(solid lead) is 205 cm. The mass of lead is 1608 ± 10kg per counter. The detector unit consistsof 8 counters installed in the reflector.
Reflector is a rectangular box, constructed of low-density polyethylene slabs of 7x 37cm.

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Fig. 2: The detector composition.

Fig. 3: Scheme of electronic wiring of a detector tube and of preamlifier.

The circuit comprising amplifier and discriminator should be attached to each counter as anintegral part of the assembly. Level of the discrimination voltage is adjusted individually foreach counter, depending on the quality of the counter tube. The next circuit, monostable
generator provides impulses of the TTL level. This generator determining death time of full4network and time constant is set on the 14 microseconds.

Fig.4: Original way of connecting tubes into channels for SMP-01.

Fig.5: The newer method of data aquisition for SAPI-02.

2.2. DATA AQUISITION PARTAt this time we are provided duplex system data aquisition. We have used two independent
devices for data aquisition. The oldest one, SMP-01, is the logical automat, which is working
from 1981 year. The newest, SAPI-02, is asembled on the the base microcomputer SAPI-02.
SMP-01 is independent unit, for continuous aquisition date across four ttl counters, where arerecieved impulses from the distributor. It contains the block of counters, the time unit, theprogram proccesor unit, the air pressure meter, and the block of output interface. The outputs
during years are changed from teletype, drive of puncher and latest serial port RS 2325

SMP-01 is providing 1min, 5min and hourly data in four chanels.

Fig.6: The block scheme of SMP-01.
SAPI-02 is an industrial microcomputer providing single data from each tube. This system isable to provide continuously the data to same as the SMP-01 and to give the information
about each tube for diagnostic apparatus in time.

Fig.7. The block scheme of SAPI-02

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2.3. PRESSURE MEASUREMENTS
Electronic pressure meter working on the principe distuning oscilator, where tuning isproviding by pressure sensor. Pressure sensor is on the base aneroid boxes.
Stability of pressure meter depend from air temperature. Therefore pressure meter is locatedin thermoisolated box with thermostat.

Fig.8: Principial scheme of electronic pressure meter.

2.4. SUPPORT PART.
For continuely meassurement is nessesery have sofistic power supply. The apparature ispowerred from UPS 24V/250Ah. For all error of works of apparature electronic circuits havepossibility made acustical allarm.

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3.

PLOTS OF PRESSURE CORRECTED COSMIC RAY INTENSITY.

3.1. MONTHLY AVERAGES.

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3.2. DAILY AVERAGES.

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3.3. HOURLY VALUES.

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