Mass Resolution for Iron Isotopes in CR-39 Track Detector

Abstract

We have verified the capability of a CR-39 track detector for isotope identification using iron beam from the heavy-ion accelerator of HIMAC at NIRS. The same CR-39 stack was independently exposed to 56Fe and 55Fe ions with an energy of 460 MeV/nucleon. Mass resolutions for 56Fe and 55Fe ions were determined to be 0.28±0.12 amu and 0.28±0.11 amu in rms, respectively. A detailed analysis of the sources of the mass dispersion in the present mass identification experiment showed that significant errors were caused in the measurements of the surface position and the thickness of CR-39 sheets. By eliminating these errors as much as possible, the mass resolution is expected to be improved to ∼0.20 amu.

Track detector of CR-39-DAP-copolymer with variable threshold to detect trans-iron nuclei in galactic cosmic rays

“…A solidstate track detector (SSTD) such as CR-39 track detector is very promising for the large-scale observation of such nuclei in GCRs. It is known that CR-39 track detector has a good mass resolution for iron nuclei (Kodaira et al, 2004(Kodaira et al, , 2007. However, a large number of background tracks produced by iron nuclei and other particles lighter than iron will cover up the tracks of trans-iron nuclei in GCRs during exposure in space.…”

A Program for the Precise Observations of Ultra Heavy Nuclei in Galactic Cosmic Rays

“…The mass of an incident charged particle was determined using the L-R technique. 21) L and R are the track length of the etch pit and the residual range of the particle track, respectively. In the measurement techniques of mass identification, some measurement errors are included, which degrades the mass resolution.…”

“…In the measurement techniques of mass identification, some measurement errors are included, which degrades the mass resolution. 21) The improved of accuracy in microscopic image analysis and detector thickness measurement 22) allowed us to identify iron isotopes with high mass resolution in the CR-39 detector. As a consequence of reducing the systematic errors, the mass resolution for iron isotopes in the CR-39 detector was found to be 0.22 ± 0.03 amu in rms, as shown in Fig.…”

Temperature and pressure conditions for the appropriate performance of charge and mass resolutions in balloon-borne CR-39 track detector for the heavy cosmic rays

“…In recent studies, we experimentally demonstrated that the adjacent isotope (A = 55 and 56) of iron nuclei (Z = 26) are clearly resolved with mass resolution of <0.22 amu (atomic mass unit) [1,2] and individual nuclear charge of trans-iron nuclei (Z>30) is separated with the charge resolution of <0.21 cu (charge unit) [3]. These results were obtained using highly purified CR-39 detectors (BARYOTRAK) combined with high speed and precise measuring systems [4][5][6].…”