Positron annihilation lifetime spectroscopy study of Kapton thin foils

Abstract

Variable energy positron annihilation lifetime spectroscopy (VE-PALS) experiments on polyimide material Kapton are reported. Thin Kapton foils are widely used in a variety of mechanical, electronic applications. PALS provides a sensitive probe of vacancy-related defects in a wide range of materials, including open volume in polymers. Varying the positron implantation energy enables direct measurement of thin foils. Thin Kapton foils are also commonly used to enclose the positron source material in conventional PALS measurements performed with unmoderated radionuclide sources. The results of depth-profiled positron lifetime measurements on 7.6 μm and 25 μm Kapton foils are reported and determine a dominant 385(1) ps lifetime component. The absence of significant nanosecond lifetime component due to positronium formation is confirmed.

Characterization of point defects in CdTe by positron annihilation spectroscopy

“…The room temperature measurements were performed using a spectrometer with a 203 ps full width half maximum (FWHM) IRF, variable temperature measurements using a system with a 265 ps FWHM IRF. Corrections for source annihilation events were performed assuming the known lifetime for Kapton foil, 14 and using the procedures outlined elsewhere. 13 Analysis was performed using the standard trapping model (STM).…”

Symmetrical positron annihilation lifetime spectrometer and single-sided measurements

“…This film is 0.12 mm in thickness, so we use a stack of 10 pieces to prevent positrons from penetrating it. Although this material is not totally the same with the 7.5-µm-thick Kapton film of 22 Na source, it also has single lifetime component of about 385 ps. For single-sided PAL spectra, the intensity of source components (include the reference sample) can be higher than 50%.…”

“…The detector that connects to the start input of TAC module (time-to-amplitude converter, ORTEC Model 567) is called detector-A, while the other one is detector-B. 22 Na γ-ray energy spectrum acquired by each detector after setting CFD thresholds is shown in figure 2 [1,17]. The range between 511 and 1275 keV photopeaks is included.…”

“…There are two more lifetime components: one is about 385 ps ascribed to the Kapton film of 22 Na source [21,22], the other is over 1 ns that may relate to positronium, air gap, and so on [12,23].…”

“…In former work, we developed a reconfigurable PAL spectrometer based on multi-channel digitizer and 22 Na radioactive source [13]. This is a conventional system utilizing two detectors and NIM standard electronic modules, but has powerful data acquisition and processing ability to realize more functions.…”