Taddei Phillip J, Borak Thomas B, Guetersloh Stephen B, Gersey Brad B, Zeitlin Cary, Heilbronn Lawrence, Miller Jack, Murakami Takeshi, Iwata Yoshiyuki
Department of Environmental and Radiological Health Sciences, Colorado State University, Fort Collins, CO 80523, USA.
Radiat Meas. 2006 Oct;4179(9-10):1227-1234. doi: 10.1016/j.radmeas.2006.01.003.
A tissue-equivalent proportional counter (TEPC) has been used as a dosimeter in mixed radiation fields. Since it does not measure LET directly, the response function must be characterized in order to estimate quality factor and thus equivalent dose for the incident radiation. The objectives of this study were to measure the response of a spherical TEPC for different high-energy heavy ions (HZE) having similar velocity and to determine how quality factors can be determined. Data were obtained at the HIMAC heavy ion accelerator for (4)He and (12)C at 220 +/- 5 MeV/nucleon (beta = 0.59) and (12)C, (16)O, (28)Si and (56)Fe at 376 +/- 15 MeV/nucleon (beta = 0.70). A particle spectrometer recorded the charge and position of each incident beam particle. Events with low energy deposition were observed for particles that passed through the wall of the TEPC but not through the sensitive volume. The frequency averaged lineal energy, y(f), was always less than the LET of the incident particles. The dose averaged lineal energy, y(D), was approximately equal to LET for particles with LET greater than 10 keV/mum, whereas y(D) was larger than LET for the lighter particles with lower LET. Part of this effect is due to detector resolution and energy straggling that increases the variance of the response function. Although the TEPC is not a LET spectrometer, it can provide real time measurements of dose and provide estimates of quality factors for HZE particles using averaged values of lineal energy.
组织等效正比计数器（TEPC）已被用作混合辐射场中的剂量计。由于它不能直接测量传能线密度（LET），因此必须对响应函数进行表征，以便估算品质因数，进而估算入射辐射的当量剂量。本研究的目的是测量球形TEPC对具有相似速度的不同高能重离子（HZE）的响应，并确定如何确定品质因数。在HIMAC重离子加速器上，以220±5 MeV/核子（β = 0.59）的能量获取了（4）He和（12）C的数据，以及以376±15 MeV/核子（β = 0.70）的能量获取了（12）C、（16）O、（28）Si和（56）Fe的数据。粒子谱仪记录每个入射束粒子的电荷和位置。对于穿过TEPC壁但未穿过灵敏体积的粒子，观察到了低能量沉积事件。频率平均线能量y(f)始终小于入射粒子的LET。对于LET大于10 keV/μm的粒子，剂量平均线能量y(D)近似等于LET，而对于LET较低的较轻粒子，y(D)大于LET。这种效应部分归因于探测器分辨率和能量离散，它们增加了响应函数的方差。尽管TEPC不是LET谱仪，但它可以提供剂量的实时测量，并使用线能量的平均值来估算HZE粒子的品质因数。
