Empirical assessment of the detection efficiency of CR-39 at high proton fluence and a compact, proton detector for high-fluence applications

Abstract

CR-39 solid-state nuclear track detectors are widely used in physics and in many inertial confinement fusion (ICF) experiments, and under ideal conditions these detectors have 100% detection efficiency for ∼0.5-8 MeV protons. When the fluence of incident particles becomes too high, overlap of particle tracks leads to under-counting at typical processing conditions (5 h etch in 6N NaOH at 80 °C). Short etch times required to avoid overlap can cause under-counting as well, as tracks are not fully developed. Experiments have determined the minimum etch times for 100% detection of 1.7-4.3-MeV protons and established that for 2.4-MeV protons, relevant for detection of DD protons, the maximum fluence that can be detected using normal processing techniques is ≲3 × 10(6) cm(-2). A CR-39-based proton detector has been developed to mitigate issues related to high particle fluences on ICF facilities. Using a pinhole and scattering foil several mm in front of the CR-39, proton fluences at the CR-39 are reduced by more than a factor of ∼50, increasing the operating yield upper limit by a comparable amount.

Angularly resolved characterization of ion beams from laser-ultrathin foil interactions

“…The time taken to overetch will depend on the particles' density per unit surface and pit size. Some species may be overetched before other species are detectable [39,40].…”

Impact of x-ray dose on track formation and data analysis for CR-39-based proton diagnostics

“…The TasTrak® CR-39 samples used in the experiment were 1.5 mm thick sheets acquired from TASL, 36 as has been used extensively in charged particle spectrometry and imaging applications in ICF 12,16,17,19,37 and the response of which has been investigated in several related studies. 25,30,38,39 The samples were laser-cut into 5 cm round discs.…”

“…Care must be taken in the etching process to ensure that all tracks are sufficiently large to be distinguished from intrinsic noise, but sufficiently small to avoid overlap of tracks in samples with high fluence. 39 In principle, the diameter-energy relationship may be used to infer more information about the proton spectrum from this data. In the development of such an analysis technique the absorbed dose in each region, which has been shown to vary substantially with the filtering across a single CR-39 sample, must be taken into account.…”

Effects of ECE duration on alpha particle tracks in polycarbonate nuclear track detectors over broad ranges of fluence and energy

“…few to 100 tracks/cm 2 or higher) in any track detector affects accuracy of low track density applications, high track density applications (e.g. >10 6 tracks/cm 2 ) suffer from overlapping of ECE tracks, depending on the ECE parameters applied.…”

“…Some studies have used chemically-etched CR-39 detectors for high particle track density parametric studies such as; overlapping of alpha particle tracks [5], using scattering foils to mitigate high proton fluences for extending the yield of DD-proton track measurements [6], applying models for recognizing track overlaps [7,8], and applying net bulk etch rates and optical absorbance in exposed CR-39 to high alpha particle fluences [9].…”