背景:超高剂量率(UHDR)束线中的剂量学受到实时监测和准确测量束输出的限制的显着挑战,梁参数,使用传统的辐射探测器提供剂量,在超高剂量率(UHDR)和高剂量每脉冲(DPP)束线条件下表现出依赖性。
目的:在本研究中,我们表征了ExradinW2塑料闪烁体的响应(标准成像,Inc.),相当于水的探测器,提供100赫兹的时间分辨率的测量,以确定其用于UHDR电子束线的可行性。
方法:通过改变脉冲重复频率(PRF),将W2闪烁体暴露于具有不同束参数的UHDR电子束,脉冲宽度(PW),电子UHDR线性加速器系统的脉冲幅度设置。W2闪烁体的响应被评估为递送的总积分剂量的函数。DPP,以及平均和瞬时剂量率。为了解释探测器的辐射损伤,测量并跟踪W2闪烁体的信号灵敏度(pC/Gy)作为剂量历史的函数。
结果:对于DPP≤1.5Gy(R2>0.99)和PRF≤90Hz,W2闪烁体表现出平均剂量率独立性和线性与积分剂量和DPP的关系。在DPP>1.5Gy时,蓝色和绿色信号中的非线性行为和信号饱和度作为DPP的函数,PRF,综合剂量变得明显。在没有切伦科夫修正的情况下,W2闪烁体表现出PW依赖性,即使DPP值<1.5Gy,对于0.5至3.6µs的PWs,测得的蓝色和绿色信号的差异高达31%和54%。对于测得的蓝色和绿色信号响应,W2闪烁体的信号灵敏度随累积剂量的变化约为4%/kGy和0.3%/kGy。分别,作为综合剂量史的函数。
结论:如果DPP保持≤1.5Gy(对应于使用的系统中平均剂量率高达290Gy/s),ExradinW2闪烁体可以提供既独立于剂量率又响应为线性的输出测量值,只要执行适当的校准以考虑PW和作为累积剂量的函数的信号灵敏度的变化。对于DPP>1.5Gy,W2闪烁体的响应变得非线性,可能是由于与高信号强度有关的静电计的限制。
BACKGROUND: Dosimetry in ultra-high dose rate (UHDR) beamlines is significantly challenged by limitations in real-time monitoring and accurate measurement of beam output, beam parameters, and delivered doses using conventional radiation detectors, which exhibit dependencies in ultra-high dose-rate (UHDR) and high dose-per-pulse (DPP) beamline conditions.
OBJECTIVE: In this study, we characterized the response of the Exradin W2 plastic
scintillator (Standard Imaging, Inc.), a water-equivalent detector that provides measurements with a time resolution of 100 Hz, to determine its feasibility for use in UHDR electron beamlines.
METHODS: The W2 scintillator was exposed to an UHDR electron beam with different beam parameters by varying the pulse repetition frequency (PRF), pulse width (PW), and pulse amplitude settings of an electron UHDR linear accelerator system. The response of the W2
scintillator was evaluated as a function of the total integrated dose delivered, DPP, and mean and instantaneous dose rate. To account for detector radiation damage, the signal sensitivity (pC/Gy) of the W2 scintillator was measured and tracked as a function of dose history.
RESULTS: The W2 scintillator demonstrated mean dose rate independence and linearity as a function of integrated dose and DPP for DPP ≤ 1.5 Gy (R2 > 0.99) and PRF ≤ 90 Hz. At DPP > 1.5 Gy, nonlinear behavior and signal saturation in the blue and green signals as a function of DPP, PRF, and integrated dose became apparent. In the absence of Cerenkov correction, the W2
scintillator exhibited PW dependence, even at DPP values <1.5 Gy, with a difference of up to 31% and 54% in the measured blue and green signal for PWs ranging from 0.5 to 3.6 µs. The change in signal sensitivity of the W2 scintillator as a function of accumulated dose was approximately 4%/kGy and 0.3%/kGy for the measured blue and green signal responses, respectively, as a function of integrated dose history.
CONCLUSIONS: The Exradin W2
scintillator can provide output measurements that are both dose rate independent and linear in response if the DPP is kept ≤1.5 Gy (corresponding to a mean dose rate up to 290 Gy/s in the used system), as long as proper calibration is performed to account for PW and changes in signal sensitivity as a function of accumulated dose. For DPP > 1.5 Gy, the W2
scintillator\'s response becomes nonlinear, likely due to limitations in the electrometer related to the high signal intensity.