Measurement of the atmospheric families using an image scanner M.Tamada a , K.Honda b , S.Makino b , M.Hironaga a and N.Shimano a a School of Science and Engineering, Kinki University, Higashi-Osaka, 577-8502, Japan b Faculty of Engineering, University of Yamanashi, Kofu, 400-8511, Japan A possibility to use an image scanner is studied for the measurement of high energy atmospheric families detected in Chacaltaya emulsion chambers. Possible methods to remove noise spots and to identify shower spots in the X-ray films applying image processing techniques are discussed. Shower-spot darkness measured using an image scanner are compared with those measured by the usual photometric method. Also discussed is tracking of shower spots in successive layers of the emulsion chambers using neural-network techniques 1. Introduction Large area emulsion chamber experiments have been carried out at high mountains in order to study very high-energy cosmic-ray phenomena. An emulsion chamber is a multiple sandwich of lead plates and photo-sensitive layers (X-ray films and/or nuclear emulsion plates). An electromag- netic particle incident upon the chamber pro- duces a cascade shower in the chamber. Electrons in the cascade shower are recorded by photo- sensitive layers. After photographic development, we can observe the shower as a small dark spot (∼ 200μm in diameter ) on X-ray films. The dark- ness of shower spots detected by X-ray films in the emulsion chamber is usually measured layer by layer using a micro-photometer to estimate the energy of each shower. The measurement is, however, very time-consuming. Here we study the possibility of using a digital image-scanner for measuring the darkness of shower spots detected by the emulsion chamber in the Chacaltaya hy- brid experiment 1 2. Measurement by image scanner 2.1. Calibration The scanner which we use is EPSON ES8500 which has film scanning area of 290 × 420 mm 2 1 It is reported that semi-automatic measurements of emul- sion chamber data are successful in Tibet ASγ experimen- tal group[1]. 0 0.5 1 1.5 2 2.5 3 3.5 10 0 10 1 10 2 10 3 darkness d pixel value z (8bit) Figure 1. Calibration between darkness, d, mea- sured by micro-photometer, and pixel value, z , measured by image scanner, of test film chart. and can capture a film image with a spatial res- olution of 1600 dpi, at most, and with trans- parency value of each pixel as a 14-bit unsigned integer. In the present measurements, the film image is measured with a spatial resolution of 600 dpi (pixel size is 42.3 ×42.3μm 2 ) and with trans- parency value (pixel value) z as an 8-bit unsigned integer both input and output. In order to calibrate film darkness, d, and pixel Nuclear Physics B (Proc. Suppl.) 151 (2006) 240–243 0920-5632/$ – see front matter © 2005 Elsevier B.V. All rights reserved. www.elsevierphysics.com doi:10.1016/j.nuclphysbps.2005.07.065