Determination of number and diameter of superheated droplets in bubble detectors (BD) of Type T-12 by irradiation with high energy heavy ions 56Fe, 84Kr and 132Xe at accelerator

The number (n) and diameter (d) of superheated droplets in bubble detectors of Type T-12 have been determined with high-energy heavy ions ⁵⁶Fe, ⁸⁴Kr and ¹³²Xe at HIMAC accelerator in the National Institute of Radiological Sciences (NIRS), Chiba Japan. The approach to determining the number and diameter of superheated droplets is based on determination of (1) the average gap distance (g) between two neighboring bubbles in a track of high-energy heavy ion and (2) the volume ratio (V_L/V) of superheated droplets to the whole volume of the detector. The volume ratio is known from preparation process of bubble detectors. The average gap distance can be obtained from the mean of gap distances measured between two neighboring bubbles in a track of heavy ion. From g and V_L/V one can obtain the two basic parameters n and d of the bubble detector, which are unknown due to invisibility of superheated droplets in bubble detector. Four batches of bubble detectors of Type T-12 were calibrated by this approach. It shows that the average gap distance of bubbles in the detectors is ∼1 mm, the volume density (number n) of superheated droplets in the detectors is ∼10⁶ cm⁻³ and the diameter of superheated droplets is in the range from ∼30 to 50 μm. It also shows that the two parameters n and d are different from batch to batch of the detectors when V_L/V is the same. Therefore, one should make a calibration of bubble detectors at accelerator with heavy ions before using the detectors. This property is similar to that of etch track detectors (SSNTD).