Heavy-ion conformal irradiation in the shallow-seated tumor therapy terminal at HIRFL

Basic research related to heavy-ion cancer therapy has been done at the Institute of Modern Physics (IMP), Chinese Academy of Sciences since 1995. Now a plan of clinical trial with heavy ions has been launched at IMP. First, superficially placed tumor treatment with heavy ions is expected in the therapy terminal at the Heavy Ion Research Facility in Lanzhou (HIRFL), where carbon ion beams with energy up to 100 MeV/u can be supplied. The shallow-seated tumor therapy terminal at HIRFL is equipped with a passive beam delivery system including two orthogonal dipole magnets, which continuously scan pencil beams laterally and generate a broad and uniform irradiation field, a motor-driven energy degrader and a multi-leaf collimator. Two different types of range modulator, ripple filter and ridge filter with which Guassian-shaped physical dose and uniform biological effective dose Bragg peaks can be shaped for therapeutic ion beams respectively, have been designed and manufactured. Therefore, two-dimensional and three-dimensional conformal irradiations to tumors can be performed with the passive beam delivery system at the earlier therapy terminal. Both the conformal irradiation methods have been verified experimentally and carbon-ion conformal irradiations to patients with superficially placed tumors have been carried out at HIRFL since November 2006.

Correlation between initial chromatid damage and survival of various cell lines exposed to heavy charged particles

The biophysical characteristics of heavy ions make them a rational source of radiation for use in radiotherapy of malignant tumours. Prior to radiotherapy treatment, a therapeutic regimen must be precisely defined, and during this stage information on individual patient radiosensitivity would be of very great medical value. There are various methods to predict radiosensitivity, but some shortfalls are difficult to avoid. The present study investigated the induction of chromatid breaks in five different cell lines, including one normal liver cell line (L02), exposed to carbon ions accelerated by the heavy ion research facility in Lanzhou (HIRFL), using chemically induced premature chromosome condensation (PCC). Previous studies have reported the number of chromatid breaks to be linearly related to the radiation dose, but the relationship between cell survival and chromatid breaks is not clear. The major result of the present study is that cellular radiosensitivity, as measured by D-0, is linearly correlated with the frequency of chromatid breaks per Gy in these five cell lines. We propose that PCC may be applied to predict radiosensitivity of tumour cells exposed to heavy ions.

Effect of phase relaxation on quantum superpositions in complex collisions

We study the effect of phase relaxation on coherent superpositions of rotating clockwise and anticlockwise wave packets in the regime of strongly overlapping resonances of the intermediate complex. Such highly excited deformed complexes may be created in binary collisions of heavy ions, molecules, and atomic clusters. It is shown that phase relaxation leads to a reduction of the interference fringes, thus mimicking the effect of decoherence. This reduction is crucial for the determination of the phase-relaxation width from the data on the excitation function oscillations in heavy-ion collisions and bimolecular chemical reactions. The difference between the effects of phase relaxation and decoherence is discussed.

Survival and initial chromatid breakage in normal and tumour cells exposed in vitro to gamma rays and carbon ions at the HIRFL

Human hepatoma and normal liver cells were irradiated with C-12(6+) ion beams (linear energy transfer (LET) = 96 keV mu m(-1)) and gamma-rays at the Heavy Ion Research Facility in Lanzhou (HIRFL). The numbers and types of chromatid breaks were detected using the premature chromosome condensation technique. Irradiation with C-12(6+) ions produced a majority of isochromatid break types, while chromatid breaks were dominant for irradiation with gamma-rays. Experimental results showed that the initial level of chromatid breaks is clearly related to the absorbed dose from C-12(6+), ions and gamma-rays. The (12)C(6+)ions are relatively more effective at inducing initial chromatid breaks when compared with the gamma-rays. A relative biological effectiveness (RBE) of about 2.5 resulted for the induction of initial chromatid breaks by C-12(6+) ions relative to gamma-rays in both cell lines.

ATOMIC PHYSICS RESEARCHES AT COOLER STORAGE RING IN LANZHOU

The commissioning of the cooler storage rings (CSR) was successful, and the facility provides new possibilities for atomic physics with highly charged ions. Bare carbon, argon ions, were successfully stored in the main ring CSRm, cooled by cold electron beam, and accelerated up to 1 GeV/u. Heavier ions as Xe44+ and Kr28+ were also successfully stored in the CSRs. Both of the rings are equipped with new generation of electron coolers which can provide different electron beam density distributions. Electron-ion interactions, high precision X-ray spectroscopy, complete kinematical measurements for relativistic ion-atom collisions will be performed at CSRs. Laser cooling of heavy ions are planned as well. The physics programs and the present status will be summarized.

Slow highly charged ions induced electron emission from clean Si surfaces

The electron emission yields from the interaction of slow highly charged ions (SHCI) He2+, O2+ and Ne2+ with clean Si surface are measured separately. It is found that electron emission yield gamma increases proportionally to projectile kinetic energy E-p/M-p, ranging from 0.75 keV/u to 10.5 keV/u (i.e. 3.8 x 10(5) m/s <= v(p) <= 1.42 x 10(6) m/s), and it is higher for heavy ions (O2+ and Ne2+) than for light ion (He2+). For O2+ and Ne2+, gamma increases with Z(p) decreasing in our energy range, and it shows quite different from the result for higher projectile kinetic energy. After calculating the stopping power by using TRIM 2006, it is found that the fraction of secondary electrons induced by recoil atoms increases significantly at lower projectile energy, thereby leads to the differences in gamma for heavy ions O2+ and Ne2+ between lower and higher projectile kinetic energy.

Parton energy loss in heavy-ion collisions via direct-photon and charged-particle azimuthal correlations

Charged-particle spectra associated with direct photon (gamma(dir)) and pi(0) are measured in p + p and Au + Au collisions at center-of-mass energy root(S)(NN) = 200 GeV with the STAR detector at the Relativistic Heavy Ion Collider. A shower-shape analysis is used to partially discriminate between gamma(dir) and pi(0). Assuming no associated charged particles in the gamma(dir) direction ( near side) and small contribution from fragmentation photons (gamma(frag)), the associated charged-particle yields opposite to gamma(dir) (away side) are extracted. In central Au + Au collisions, the charged-particle yields at midrapidity (vertical bar eta vertical bar < 1) and high transverse momentum (3 < (assoc)(PT) < 16 GeV/c) associated with gamma(dir) and pi(0) (vertical bar eta vertical bar < 0.9, 8 < (trig)(PT) < 16 GeV/c) are suppressed by a factor of 3-5 compared with p + p collisions. The observed suppression of the associated charged particles is similar for gamma(dir) and pi(0) and independent of the gamma(dir) energy within uncertainties. These measurements indicate that, in the kinematic range covered and within our current experimental uncertainties, the parton energy loss shows no sensitivity to the parton initial energy, path length, or color charge.

Observation of charge-dependent azimuthal correlations and possible local strong parity violation in heavy-ion collisions

Parity (P)-odd domains, corresponding to nontrivial topological solutions of the QCD vacuum, might be created during relativistic heavy-ion collisions. These domains are predicted to lead to charge separation of quarks along the orbital momentum of the system created in noncentral collisions. To study this effect, we investigate a three-particle mixed-harmonics azimuthal correlator which is a P-even observable, but directly sensitive to the charge-separation effect. We report measurements of this observable using the STAR detector in Au + Au and Cu + Cu collisions at root s(NN) = 200 and 62 GeV. The results are presented as a function of collision centrality, particle separation in rapidity, and particle transverse momentum. A signal consistent with several of the theoretical expectations is detected in all four data sets. We compare our results to the predictions of existing event generators and discuss in detail possible contributions from other effects that are not related to P violation.

Spectra of identified high-p(T) pi(+/-) and p((p)over-bar ) in Cu + Cu collisions at root s(NN)=200 GeV

We report new results on identified (anti) proton and charged pion spectra at large transverse momenta (3 < p(T) < 10 GeV/c) from Cu + Cu collisions at root s(NN) = 200 GeV using the STAR detector at the Relativistic Heavy Ion Collider (RHIC). This study explores the system size dependence of two novel features observed at RHIC with heavy ions: the hadron suppression at high-p(T) and the anomalous baryon to meson enhancement at intermediate transverse momenta. Both phenomena could be attributed to the creation of a new form of QCD matter. The results presented here bridge the system size gap between the available pp and Au + Au data, and allow for a detailed exploration of the onset of the novel features. Comparative analysis of all available 200 GeV data indicates that the system size is a major factor determining both the magnitude of the hadron spectra suppression at large transverse momenta and the relative baryon to meson enhancement.

Ion acceleration with mixed solid targets interacting with circularly polarized lasers

The interaction of a circularly polarized laser pulse with a mixed solid target containing two species of ions is studied by particle in cell simulations and analytical model. After the interaction tends to be stable, it is demonstrated that the acceleration is more efficient for the heavier ions than that in plasmas containing a single kind of heavy ion and the acceleration efficiency is higher when its proportion is lower. To obtain monoenergetic heavy-ion beams, a sandwich target with a thin mixed ion layer between two light ion layers and a microstructured target are proposed. The influences of parameters of the laser pulse and target on ion acceleration are discussed in detail. It is found that, when the target is thick enough, a cold target is more appropriate for heavy-ion acceleration than a warm target, and the velocity of the reflected heavy ions is proportional to the laser amplitude.

Two overrun phenomena and their effects on fusion yield in the Coulomb explosion of heteronuclear clusters

Two overrun effects in the Coulomb explosion dynamics of heteronuclear clusters have been investigated theoretically by the use of a simplified electrostatic model. When the charge-to-mass ratio of light ions is higher than that of heavy ions, the light ions can overtake the heavy ions inside the cluster and acquire a higher kinetic energy. Further, if the charge density of the heavy ions is twice as high as that of the light ions, i.e. a proposed competitive parameter xi = rho BqB/rho AqA > 2, the inner light ions can overtake those light ions on the surface of the cluster and form a shock shell during the explosion, which might drive the intracluster collision and fusion of the light ions. Different regimes of nuclear fusion are discussed and the corresponding neutron yields are estimated. Our analysis indicates that the probability of intracluster fusion is quite low even if deuterated heteronuclear clusters such as (DI)(n) with large size and high competitive parameter are employed. However, heteronuclear clusters are still a better candidate compared with homonuclear clusters for enhancing the total intercluster fusion yield because both a higher energy region and a higher proportion of deuterons distributing in the energy region can be created in the deuterated heteronuclear clusters.

云母模板中Cu纳米线的制备及其光学性质研究

Nanopores with diameters between 30 nm and 180 nm have been fabricated by inducing latent track with fast heavy ions and etching process in 25 μm thick,single-crystal muscovite mica.For short etching time,the nanopores are columns with circular cross section.For long etching time the cross section of nanopores becomes rhombic.Thus the shape of nanopores depends on the etching time.Cu nanowires have been fabricated with controlled dimensions by electrodeposition into the nanopores.The ultraviolet-visible lig...中文文摘：利用快重离子辐照的单晶白云母片产生潜径迹,蚀刻得到直径在30—180nm纳米孔道.孔道形状依赖于蚀刻时间,蚀刻时间短得到圆柱形孔道,蚀刻时间长得到菱柱形孔道.从而在云母模板孔道中电化学沉积得到不同直径和形状的Cu纳米线.通过紫外可见光谱分析,发现铜纳米线的尺寸和形状影响其光学性质.直径小于60nm的近似为圆柱状Cu纳米线有一个明显的表面等离子体共振峰和一个微弱的次峰.随着直径增加,菱柱状的Cu纳米线主峰有明显的红移,次峰逐渐增强.同时利用扫描电子显微镜、X射线衍射对Cu纳米线的形貌和晶体结构特征进行了表征.

兰州重离子加速器深层治癌扫描电源研究与设计

This paper describes the technique targets and operation principle of the scanning power supply for the deep tumor therapy facility with heavy ions in Cooler-Storage-Ring of the Heavy Ion Research Facility in Lanzhou(HIRFL-CSR).To ensure the specified accuracy of the current,the hysteresis loop control strategy was adopted,and tracking error was constrained in the specified tolerance.One prototype was designed and installed.And the simulation results and test results were listed in the paper.The results sho...中文摘要：阐述了用于兰州重离子深层治癌装置的扫描电源的技术指标和工作原理,为保证该电源输出电流的精度,采用滞环控制策略,将跟踪误差限制在设计要求的误差范围内。研制了1台扫描电源样机,并给出了电路仿真和测试结果。测试结果显示各项指标均达到了设计要求,表明所选电路结构和滞环控制方案是切实可行的。

Commissioning of electron cooling in CSRm

A new generation electron cooler has started operation in the heavy ion synchrotron CSRm which is used to increase the intensity of heavy ions. Transverse cooling of the ion beam after horizontal multi-turn injection allows beam accumulation at the injection energy. After optimization of the accumulation process an intensity increase in a synchrotron pulse by more than one order of magnitude has been achieved. In given accumulation time interval of 10 seconds, 108particles have been accumulated and accelerated to the final energy. The momentum spread after accumulation and acceleration in the 10−4 range has been demonstrated in six species of ion beams. Primary measurements of accumulation process varying with electron energy,electron beam current, electron beam profile, expansion factor and injection interval have been performed.The lifetimes of ion beams in the presence of electron beams were roughly measured with the help of DCCT signal.