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Comment to “On the aging of the scintillation counters for RUN II Muon System at CDF”
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Nuclear Instruments and Methods in Physics Research A 591 (2008) 467 www.elsevier.com/locate/nima
Letter to the Editor
Comment to ‘‘On the aging of the scintillation counters for RUN II Muon System at CDF’’ I. Chirikov-Zorin Joint Institute for Nuclear Research, Dubna, Russian Federation Received 23 January 2008; received in revised form 24 January 2008; accepted 8 February 2008 Available online 4 March 2008
In the paper ‘‘On the of aging of the scintillation counters for RUN II Muon System at CDF’’ [1] the authors, investigating the degradation of plastic scintillation counters, erroneously assumed exponential decrease of light yield over the time of their operation, and determined the aging constant of different counters t (the time over which, the light signal is reduced by a factor e). I have been investigating the degradation of plastic scintillators for more than 15 years. The results of these studies for 12 years are published in the article ‘‘Properties of the Ukraine polystyrene-based plastic scintillator UPS 923A’’ [2], in which it is shown that the decrease of light yield of the 320-cm-long counter from the plastic scintillator UPS 923A with the WLS fibers read-out [3] has a linear nature with the rate of the degradation about 6% per year and is determined by the destruction of the polymeric base. The experimental data of work [1] also show the linear nature of a change in the light yield of CDF counters in the course of time (see Figs. 12 and 15). Therefore, the motivation of the authors [1], who approximate the experimental data by the exponential dependence, is not clear. Using the goodness of fit test of w2 it is possible to easily reject the hypothesis about the exponential dependence of the change in the light yield. The linear time dependence of the average values of the light yield is also observed (see Figs. 9b and 11b) [1]. It is necessary to note that the errors of the experimental data in Figs. 7b, 9b, and 11b, which follow from the histograms in Figs. 6, 8, and 10, are significantly reduced by the authors. If real errors are used for the data in Figs. 9b and 11b, the DOI of original article: 10.1016/j.nima.2007.05.327 E-mail address: [email protected] 0168-9002/$ - see front matter r 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.nima.2008.02.035
fitting by the exponential curve becomes absolutely meaningless. The authors of ‘‘Tests of new polystyrene-based scintillators’’ [4] investigated in detail the natural degradation of plastic scintillators for more than 4 years and also observed linear dependence of the change in the light yield from the long counters on the time with the rate of degradation few percent per year. Thus, the hypothesis about the exponential dependence of the degradation of the light yield from the plastic scintillation counters in the course of time is not confirmed experimentally. Therefore, the results given in Table 2 (table of the main results) [1] are incorrect. Exponential idea about the degradation of plastic scintillators in the course of time can lead to the serious errors in the planning of experiments in particle physics. In conclusion, I emphasize that plastic scintillators possess good long-term stability. For example, the decrease of light yield even from long polystyrene-based scintillator counters has linear dependence on time with the rate of degradation few percent per year [2,4]. References [1] A. Artikov, D. Chokheli, G. Pauletta, et al., Nucl. Instr. and Meth. A 579 (2007) 1122. [2] A. Artikov, J. Budagov, I. Chirikov-Zorin, et al., Nucl. Instr. and Meth. A 555 (2005) 125. [3] A. Artikov, J. Budagov, I. Chirikov-Zorin, et al., Nucl. Instr. and Meth. A 538 (2005) 358. [4] T. Hasegawa, M. Hazumi, S. Kasai, et al., Nucl. Instr. and Meth. A 311 (1992) 498.
Nuclear Instruments and Methods in Physics Research A 591 (2008) 467 www.elsevier.com/locate/nima
Letter to the Editor
Comment to ‘‘On the aging of the scintillation counters for RUN II Muon System at CDF’’ I. Chirikov-Zorin Joint Institute for Nuclear Research, Dubna, Russian Federation Received 23 January 2008; received in revised form 24 January 2008; accepted 8 February 2008 Available online 4 March 2008
In the paper ‘‘On the of aging of the scintillation counters for RUN II Muon System at CDF’’ [1] the authors, investigating the degradation of plastic scintillation counters, erroneously assumed exponential decrease of light yield over the time of their operation, and determined the aging constant of different counters t (the time over which, the light signal is reduced by a factor e). I have been investigating the degradation of plastic scintillators for more than 15 years. The results of these studies for 12 years are published in the article ‘‘Properties of the Ukraine polystyrene-based plastic scintillator UPS 923A’’ [2], in which it is shown that the decrease of light yield of the 320-cm-long counter from the plastic scintillator UPS 923A with the WLS fibers read-out [3] has a linear nature with the rate of the degradation about 6% per year and is determined by the destruction of the polymeric base. The experimental data of work [1] also show the linear nature of a change in the light yield of CDF counters in the course of time (see Figs. 12 and 15). Therefore, the motivation of the authors [1], who approximate the experimental data by the exponential dependence, is not clear. Using the goodness of fit test of w2 it is possible to easily reject the hypothesis about the exponential dependence of the change in the light yield. The linear time dependence of the average values of the light yield is also observed (see Figs. 9b and 11b) [1]. It is necessary to note that the errors of the experimental data in Figs. 7b, 9b, and 11b, which follow from the histograms in Figs. 6, 8, and 10, are significantly reduced by the authors. If real errors are used for the data in Figs. 9b and 11b, the DOI of original article: 10.1016/j.nima.2007.05.327 E-mail address: [email protected] 0168-9002/$ - see front matter r 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.nima.2008.02.035
fitting by the exponential curve becomes absolutely meaningless. The authors of ‘‘Tests of new polystyrene-based scintillators’’ [4] investigated in detail the natural degradation of plastic scintillators for more than 4 years and also observed linear dependence of the change in the light yield from the long counters on the time with the rate of degradation few percent per year. Thus, the hypothesis about the exponential dependence of the degradation of the light yield from the plastic scintillation counters in the course of time is not confirmed experimentally. Therefore, the results given in Table 2 (table of the main results) [1] are incorrect. Exponential idea about the degradation of plastic scintillators in the course of time can lead to the serious errors in the planning of experiments in particle physics. In conclusion, I emphasize that plastic scintillators possess good long-term stability. For example, the decrease of light yield even from long polystyrene-based scintillator counters has linear dependence on time with the rate of degradation few percent per year [2,4]. References [1] A. Artikov, D. Chokheli, G. Pauletta, et al., Nucl. Instr. and Meth. A 579 (2007) 1122. [2] A. Artikov, J. Budagov, I. Chirikov-Zorin, et al., Nucl. Instr. and Meth. A 555 (2005) 125. [3] A. Artikov, J. Budagov, I. Chirikov-Zorin, et al., Nucl. Instr. and Meth. A 538 (2005) 358. [4] T. Hasegawa, M. Hazumi, S. Kasai, et al., Nucl. Instr. and Meth. A 311 (1992) 498.