SU-F-J-190: Time Resolved Range Measurement System Using Scintillator and CCD Camera for the Slow Beam Extraction

Purpose:To investigate the time structure of the range, we have verified the rang shift due to the betatron tune shift with several synchrotron parameters.Methods:A cylindrical plastic scintillator block and a CCD camera were installed on the black box. Using image processing, the range was determined the 80 percent of distal dose of the depth light distribution. The root mean square error of the range measurement using the scintillator and CCD system is about 0.2 mm. Range measurement was performed at interval of 170 msec. The chromaticity of the synchrotron was changed in the range of plus or minus 1% from reference chromaticity in this study. All of the particle inside the synchrotron ring were extracted with the output beam intensity 1.8×108 and 5.0×107 particle per sec.Results:The time strictures of the range were changed by changing of the chromaticity. The reproducibility of the measurement was sufficient to observe the time structures of the range. The range shift was depending on the number of the residual particle inside the synchrotron ring.Conclusion:In slow beam extraction for scanned carbon-ion therapy, the range shift is undesirable because it causes the dose uncertainty in the target. We introduced the time-resolved range measurement using scintillator and CCD system. The scintillator and CCD system have enabled to verify the range shift with sufficient spatial resolution and reproducibility.