Article

Study of saturation of CR39 nuclear track detectors at high ion fluence and of associated artifact patterns

Department of Physics, University of Nevada, Reno, Reno, Nevada, United States
Review of Scientific Instruments (Impact Factor: 1.58). 02/2007; 78(1):013304. DOI: 10.1063/1.2400020
Source: PubMed

ABSTRACT The occurrence of saturation in CR39 solid state nuclear track detectors has been systematically studied as a function of the incident ion (alpha particles and laser-accelerated protons) fluence and the etching time. When overexposed (i.e., for fluences above approximately 10(8) particles/cm(2)) and/or overetched, the CR39 detectors enter a saturated regime where direct track counting is not possible anymore. In this regime, optical measurements of saturated CR39 detectors become unreliable as well, since the optical response of the saturated detectors with respect to the ion fluence is highly nonlinear. This nonlinear optical response is likely due to scattering from the surface of irregular clumping patterns which have a diameter approximately 20 microm, i.e., ten times larger than the diameter of individual tracks. These patterns, which aggregate many individual tracks, are observed to develop in highly saturated regimes. For fluences typical of high energy short pulse laser experiments, saturation occurs, inducing the appearance of artifact ringlike structures. By careful microscopic analysis, these artifact ring patterns can be distinguished from the genuine rings occurring below saturation and characteristic of low energy laser accelerated proton beams.

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    • "Therefore , diagnosis of laser-accelerated ion beams attracts much attention and a precise characterization of accelerated ions is a crucial issue to develop a compact laser ion accelerator for medical and industrial applications. Solid state nuclear track detectors (Fleischer et al., 1975) such as CR-39 detectors have been so far extensively used to detect accelerated ions (Fukuda et al., 2009; Gaillard et al., 2007; Haberberger et al., 2011; Tampo et al., 2010), because the CR-39 are insensitive to high energy photons and electrons and capable of detecting only ions (Oda et al., 1997). It is, however, impossible to detect ions with energies higher than the detection threshold limit of the CR-39, where the detection threshold limit is defined as the particle energy where the stopping power in the detector becomes smaller than the sensitivity of the detector. "
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    ABSTRACT: A new diagnosis method for high energy ions utilizing a single CR-39 detector mounted on plastic plates is demonstrated to identify the presence of the high energy component beyond the CR-39’s detection threshold limit. On irradiation of the CR-39 detector unit with a 25 MeV per nucleon He ion beam from conventional rf-accelerators, a large number of etch pits having elliptical openings are observed on the rear surface of the CR-39. Detailed investigations reveal that these etch pits are created by heavy ions inelastically backscattered from the plastic plates. This ion detection method is applied to laser-driven ion acceleration experiments using cluster-gas targets, and ion signals with energies up to 50 MeV per nucleon are identified.
    Radiation Measurements 05/2013; 50:92. DOI:10.1016/j.radmeas.2012.10.010 · 1.14 Impact Factor
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    • "On the other hand, the measured deflection can provide, besides thermal and optical parameters [2], with carrier transport properties such as lifetime of photo-induced free carriers [3], detailed analysis of the defect structure of thin films [4] [5]. Nuclear track detector CR-39 offers many advantages to other detectors besides their low cost and simplicity in exploitation, preferred ion detector like alpha particles and insensitive to gamma and x-rays [6], dosimetric determination [7]. These detectors require long processing time and extensive chemical etching [8]. "
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    ABSTRACT: Photothermal deflection is described in this article to detect the change in the thermal and optical properties of the track nuclear detector CR-39 when irradiated to alpha particles. The probe laser beam deflection was found to decrease with the increase of time of exposure to alpha particles. A novel technique, in-situ image analysis of the photothermal deflection spot is presented to assess the detection of the CR-39 to any nuclear particle or radiation instantaneously. This technique offers the ability to acquire data very rapidly and can be used for monitoring any source of nuclear radiations immediately.
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    01/2008, Degree: PhD
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Questions & Answers about this publication

  • Kirk Flippo added an answer in Nuclear Chemistry:
    CR-39 detectors can be used to determine radon concentrations,is there any other application of CR-detectors?
    Radiation and health Physics
    Kirk Flippo · Los Alamos National Laboratory
    Here is a paper on using CR-39 near saturation. As Afshan points out CR-39 is used in laser-ion acceleration experiments (especially for low yields), it is also used on the Nation Ignition Laser facility in the Magnetic Recoil Spectrometer (run by MIT), as well as a neutron diagnostic, or alpha detector. Radiochromic Film (a self developing film) is used for higher flux radiography of ion beams, and in general radiotherapy applications at hospitals. A NOTE OF CAUTION, Pons and Fleishman (http://en.wikipedia.org/wiki/Cold_fusion) used CR-39 in their now (in)famous cold fusion experiments to detect neutrons. These erroneous results were likely (IMHO) due to a bad batch of detectors. The vendor matters in using CR-39, as does the need for etching controls on all batches. Homolite, another CR-39 vendor does not process their polymer for these types of applications, and no QA is done to assure the batch will not give you tracks when not exposed to any radiation, so buyer beware!