Investigation of cosmic ray intensity variation at primary rigidity above 1.7 TV

by Lee, Yiu-wa

(Uncorrected OCR) Abstract of thesis entitled

. Investigation of cosmic ray intensity variation

at primary rigidity above 1.7 TV'

submitted by LEE Yiu-wa

for the degree of Master of Philosophy

at the University of Hong Kong

in November, 1986.

------------------------------

A telescope has been set up in an underground

laboratory to study the cosmic ray intensity variations at

The intensity weighted average depth of

the laboratory is found to be 587 hg cm-2 which

corresponds to a mean muon threshold energy of about 147

GeV and a median rigidity about 1750 GV.

The telescope is composed of triple layers of

proportional counters, each layer of area about 3.65m x 2m

and their separation o. Sm.

Event selection is achieved by

triple coincidence of the counter layers and by software

track identification.

Arrival direction histograms are

accumulated and recorded hourly.

The counters are

continuously checked by a monitor spectrum.

Data in the period from November 1983 to February

1986 are analysed.

The duty cycle is about 81% and a

total of 1. 98x1 07 are accumulated.

The total barometer

coefficients for the above period is found to be

(0. 00677?. 00475) % mb- l.

The result obtained so far in

the first and second harmonics in sidereal frequency are

Amplitude( x10-4)

Phase (hr)

First harmonic

+5.4 7.9 -5.9

4. 2:!:1 .7

Second harmonic

+5.0

4.2 8

-3.

1. 7:!:3. 6

where the confidence limits for the amplitudes are 5% and

95% and those for the phases are 68%. The calculation is

based on the non-Gaussian distribution.

The first and second harmonics in anti-sidereal

frequency are found to be statistically insignificant.

The result is consistent with recent measurements in other

stations.