The History

The Aberdeen Tunnel Laboratory is the first and only underground particle physics laboratory in Hong Kong.

The site's potential for particle physics experiments was recognised during a survey of traffic tunnels by The University of Hong Kong, when the Aberdeen Tunnel was still under construction. The laboratory was completed in 1980 and was used as a cosmic ray telescope to study anisotropy and sidereal variations of the cosmic ray background.

Old contour map Cosmic ray telescope

The telescope consisted of 3 horizontal layers, each having 48 cylindrical proportional counters mounted on a rigid steel frame and pointing along the East-West direction. Lead sheets covered the counters, the floor and walls to reduce natural radiation from surrounding rocks. The walls were also sprayed with waterproof material to keep relative humidity below 50%. Two phone lines were available for communication between the tunnel laboratory and the main laboratory in HKU.

The original detector Early Workers at Aberdeen

Inside the tunnel laboratory, pulses from the counters were amplified, shaped and then temporarily stored in latches. The coincidence unit determined passage of muons by selecting triple coincidence counter events. A microprocessor controlled reading of data from latches and transmission of data to the main laboratory.

Microcomputers at the main laboratory determined the direction of incoming muons and stored the event in appropriate directional bins. Events could be monitored using a video display terminal and a dot matrix printer was available for printing hard copies. Data were also stored in floppy diskettes and transferred to other computers for analysis.

The photo above shows the project leader Dr. L.K. Ng (at the right) and the technicians.

The small anisotropy discovered in cosmic ray distribution in the local interstellar medium (Y.W.Lee, 1986) was consistent with contemporary results from Australia, Japan and the United States.

The laboratory was closed after the anisotropy experiment was completed and was only recently re-opened for the Daya Bay Neutrino Experiment.