STUDY ON NEUTRON MODERATION IN ICE AT CRYOGENIC LIQUID NITROGEN TEMPERATURES

Abstract

Abstract

The present study concentrates on the measurement of neutron fluence in the flux of cold neutrons emanating from an H₂O ice moderator when it is cooled from ambient to several liquid nitrogen cryogenic temperatures. The temperature of neutrons when the moderator is at cryogenic temperature has been determined from this fluence. The integrated cold neutron flux is obtained by using a polycrystalline beryllium low pass filter in the path of a scattered neutron beam – a small angle neutron scattering beam line available at Malaysian TRIGA reactor. The water was cooled inside the cryogenic cooling chamber which based on a simple continuous flow (SCF) cryostat concept. The neutron spectrums were measured using a Portable Spectroscopic Neutron Probe (N-Probe Microspec Version 6). It was observed that the fluence dropped as the water transforming to ice.

Abstrak

Kajian ini tertumpu kepada pengukuran fluence neutron dalam aliran neutron sejuk yang berasal daripada penyederhanaan ais H₂O apabila ia disejukkan daripada suhu ambien ke beberapa suhu kriogenik nitrogen cair. Suhu neutrontelah ditentukan dari ‘fluence’ ini apabila moderator berada pada suhu ‘cryogenic’. Fluks neutron sejuk bersepadu diperoleh dengan menggunakan penapis rendah polikristalin berilium yang diletakkan dalam alur neutron yang terserak pada sudut kecil yang terdapat di reaktor TRIGA di Malaysia. Air disejukkan di dalam ruang penyejukan kriogenik yang berdasarkan konsep mudah ‘cryostat’ aliran berterusan (SCF). Spektrum neutron diukur dengan menggunakan ‘Probe Neutron Portable Spectroscopic’ (N-Probe Microspec Version 6). Pemerhatian menunjukkan bahawa ‘fluence’ turun apabila air berubah menjadi ais.