The clinical trials of tumor therapy using heavy ions beam 12C are now in progress at Institute of Modern Physics in Lanzhou. In order to achieve the precise radiotherapy with the high energy 12C beam in active pencil beam scanning mode, we have developed an ionization chamber(IC) as an online monitor for beam intensity and also a dosimeter after calibration. Through the choosing of working gas and voltage, optimizing of the electrics and the read-out system, calibrating the linearity, the detector system provide us one of the simple and highly reliable way to monitoring the beam during the active pencil beam scanning treatments. The measurement results of this detector system show that it could work well under the condition of high energy 12C beam in active pencil beam scanning mode.
The total reaction cross section (1724±93 mb) of 17B at the energy of 43.7 A MeV on C target has been measured by using the transmission method at the Radioactive Ion Beam Line in Lanzhou (RIBLL). Assuming 17B consists of a core 15B plus two halo neutrons,the total cross section of 17B on C target was calculated with the zero-range Glauber model,where double Gaussian density distributions and Gaussian plus HO density distributions were used. It can fit the experimental data very well. The characteristic of halo structure for 17B was found with a large diffusion of the neutrons density distribution.
HU ZhengGuo1, WANG Meng1, XU HuShan1, SUN ZhiYu1, WANG JianSong1, XIAO GuoQing1, ZHAN WenLong1, XIAO ZhiGang1, MAO RuiShi1,2, LI Chen1, ZHANG XueYing1,2, ZHANG HongBin1, ZHAO TieCheng1, XU ZhiGuo1, WANG Yue1,2, CHEN RuoFu1,2, HUANG TianHeng1,2, FU Fen1,2, GAO Qi1,2, HAN JianLong1,2, ZHANG XueHeng1,2, ZHENG Chuan1,2, YU YuHong1,2 & GUO ZhongYan1 1 Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, China
In this paper we present a timing detector which has low detection threshold and is radiation-resistant.The photons induced by radioactive beam ions passing through a thin plastic-scintillator foil BC422,emit from the foil center corresponding to one focal point of an aluminum ellipsoidal mirror and are reflected to another focus point at which the cathode of a photomultiplier tube locates.A time resolution of about 115 ps can be achieved for1 2N of 58.5 MeV/u and 130 ps for1 7B of 43.7 MeV/u.The counting rate up to 10 8packets per second(pps) is allowed.
The mirror nuclei ^12N and ^12B are separated by the Radioactive Ion Beam Line in Lanzhou （RIBLL） at HIRFL from the breakup of 78.6 MeV/u 14N on a Be target. The total reaction cross-sections of ^12N at 34.9 MeV/u and ^12B at 54.4 MeV/u on a Si target have been measured by using the transmission method. Assuming ^12N consists of a ^11C core plus one halo proton, the excitation function of ^12N and ^12B on a Si target and a C target were calculated with the Glanber model. It can fit the experimental data very well. The characteristic halo structure for ^12N was found with a large diffusion of the protons density distribution.
A prototype of time-of-flight positron emission computed tomography （TOF-PET） has been developed for acquiring the coincident detection of 511 keV γ-rays produced from positron annihilation. It consists of two 80.5 minx80.5 mm LYSO scintillator arrays （composed of 35 ×35 pixel finger crystals） with the position sensitive photomultiplier tubes R2487 as the readout. Each array is composed of 2 mm ×2m×15 mm finger crystals and the average pixel pitch is 2.30 mm. The measured results indicate that the TOF information has the potential to significantly enhance the image quality by improving the noise variance in the image recon- struction. The best spatial resolution （FWHM） of the prototype for the pairs of 511 keV T-rays is 1.98 mm and 2.16 mm in the x and y directions, respectively, which are smaller than the average pixel pitch of 2.30 mm.
