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1.
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 Nonlinear Responses of Poly(vinyl toluene) Plastic Scintillators at High Excitation Doses
The light output intensities from commercial Pilot B and similar plastic scintillators having a poly(vinyl toluene) host were measured as a function of dose from a pulsed electron beam machine. At doses exceeding ∼ 1.5 × 104 rad in 3 × 10−9 sec, nonlinear responses were observed. For pure poly(vinyl toluene) the nonlinear responses can be explained by bimolecular interaction of the host excited states, and the product of the excited‐state yield times the interaction rate constant is 8.5 × 10−10 cm3 sec−1 per 100 eV. For Pilot B it is concluded that the dominant quenching mechanism is the reabsorption of scintillator light by mononegative ions of th e center fluor, p‐terphenyl. This conclusion is corroborated by the observation of the spectrum of decreased light transmission through the sample after electron excitation at high doses. The observed product of ion yield times extinction coefficient is 2.3 × 105 liter mole−1⋅cm−1 per 100 eV.
URL: http://jcp.aip.org/resource/1/jcpsa6...i4/p1878_s1
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2.
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Dose Rate Saturation in Plastic Scintillators
The light output intensity as a function of dose rate
from pulsed electron beam excitation was investigated for
coni'nercial Pilot B and similar plastic scintillators. Nonlinear
responses were observed above about 5 x 1012 rais/
sec. The various possible quenching mechanisms which may
be responsible for these saturation effects are discussed,
and it is suggested that the dominant quenching mechanism
in Pilot B is the absorption of the light emission by mononegative
p-terphenyl ions. This assumption is substantiated
by the observation of decreased light transmission during
electron excitation at high dose rates.
URL: http://www.lsc-international.org/con...970_265.pdf
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3.
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Saturation effects of organic scintillators to nanosecond-pulses of low-energy x-rays
The nonlinear saturation effects of organic scintillators were investigated using low-energy X-rays from a laser produced plasma. The laser system consisted of a Nd: glass facility operating at pulse widths between 2 and 6.5 ns at levels up to 15 J. The average energy of the X-ray spectrum was approximately 1.25 keV with a (1-e−1) penetration depth of 10 μm. The organic scintillators studied were NE102, NE111, and NE111 doped with 2%, 5%, and 10% benzophenone, 5% acetophenone, and 10% piperidine. It was observed that for a 6.5 ns wide pulse, the 10% nonlinearity point is at an irradiance of approximately 2 mJ/cm2 ns, while that for a 4 ns pulse is somewhat higher. No saturation was observed for pulses ⩽2 ns wide at the upper levels of irradiance (∼ 5 mJ/cm2ns) achieved in this experiment.
URL: http://www.sciencedirect.com/science...54X79900843
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4.
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Transient Nonlinear Response of Plastic Scintillators
The peak dose rate for which light output is linearly proportional to incident radiation intensity was measured by bombarding 80-mil-thick samples of NE 102 and MEL 150C scintillators with 12-MeV electrons from the EG&G/AEC linear accelerator. To obtain the equivalent gamma dose rate, the sensitivity of the scintillator-photodiode detector used in this work was measured with a calibrated Co60 source. Nonlinear behavior was observed for excitation pulse widths between six nanoseconds and 0.5 microseconds. Analysis of the detector signals indicates that nonlinearity is a function of total dose as well as dose rate. Thus for an excitation pulse width of 0.5 microseconds, scintillator output was found to be linear at the start of the burst, but showed marked nonlinearity by the end of the pulse. The data also indicate that if the dose rate drops below the threshold value after a scintillator is driven into nonlinear operation, the scintillator will continue to behave nonlinearily for some time. The decay time associated with recovery from nonlinearity is greater than 0.5 microsecond. Data are presented, showing the average dose rate required to produce 5% and 10% nonlinear behavior as a function of exposure time. As a typical case, 10% nonlinear behavior for NE 102 results from an average dose rate of 6.5 Ã 1011 R/sec for an exposure time of 10 nanoseconds.
URL: http://ieeexplore.ieee.org/xpl/artic...A4324907%29
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5.
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Temporal characteristics and saturation effects of organic scintillators to low-energy X-rays
Rise time, short and long term decay characteristics and possible saturation effects of the fluorescence of NE102, NE111, and doped NE111 organic scintillators were investigated using low-energy X-rays from a laser produced plasma. The laser system consisted of a pulsed Nd: glass facility operating at a pulse width of 0.2 ns at level up to 10J. The NE111 samples consisted of a matrix of scintillators doped with benzophenone, acetophenone, and piperidine each at concentrations of 0, 1, 2, 5, and 10 percent. The rise time of NE102 was measured at (640±50) ps while that of both the doped and undoped NE111 was ≤ 120ps. The response widths and a characterization of the short and long term decay components out to 1 s are given. Saturation effects for the NE102 and NE111 were not observed at the upper limits (15 mJ/cm2 ns) of irradiance used in this investigation.
URL: http://www.sciencedirect.com/science...54X7990435X
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