Charm production in fixed target experiments

Prompt lepton production in proton beam dump experiments has been critically analysed within the general frame work of \(A_c \bar D\) and \(D\bar D\) production and their subsequent semileptonic decays. Realistic decay modes based on recent experiments are used. We have investigated the effect of using differentx dependences for the charm particles obtained either from simple quark counting rules or as inferred from strange particle production data. The \(D\bar D\) production is assumed to have a linearA dependence and for the \(A_c \bar D\) process bothA ¹ andA ^2/3 dependence is used. We show that by a simultaneous fit to the energy and angular distributions of prompt leptons in all the experiments the ratio of \(A_c \bar D\) to \(D\bar D\) production cross section can be determined. A comparison of this fit with these experimental distributions indicates that thex dependences based on strange particle data are strongly favoured. AnA ^2/3 dependence for \(A_c \bar D\) production, which corresponds to a quasi-diffractive process, is favoured although within existing errorsA ¹ dependence cannot be ruled out. Putting together the cross section results from our analysis with other results at similar energies (p _1ab ～400GeV/c) the production cross sections ( \(A_c \bar D\) ) and ( \(D\bar D\) ) are estimated to be ～25 and ～20 μb/nucleon respectively leading to a total inclusive charm cross section of ～90 μb/nucleon.     

Light gluinos and fixed target experiments

Light gluino production cross sections in πp and pp interactions, and the missing energy distribution have been calculated for a calorimetry beam-dump experiment, at present and future accelerators. The effect of experimental cuts combined with the gluino fragmentation is discussed and compared with collider experiments.     

Polarized proton target for RI Beam experiments

We have constructed a polarized proton solid target system for radioactive nuclear beam experiments at the Center for Nuclear Study, the University of Tokyo. The proton polarization is based on an electron population difference in a photo-excited triplet state of pentacene molecule. The target system was completed in 2003 and applied to a RI beam experiment in 2003 and 2005 by using the projectile fragment separator, RIPS at RIKEN. The maximum polarization reached 20% under the condition of T=100 K and B=0.09 T. Overview of the polarized target and its application in physics experiments at RIPS and RIBF of RIKEN are presented.     

Time-resolved experiments on the photoablation of polystyrene and PMMA by ArF-laser radiation

The photoablation of polystyrene (PS) and polymethylmethacrylate (PMMA) was studied in real-time during the uv laser pulse at 193 nm. The transmission and total reflection of thin polymer layers on quartz glass substrates was measured time-resolved. From the results for the strongly absorbing PS it can be concluded that the emission of material starts within the first few nanoseconds of the laser pulse. Photoablation of PMMA, which is a relatively weak absorber at 193 nm, is accompanied by strong modifications of the transmission by the first several ten laser pulses.     

Why are polarized beam and target experiments interesting?

The objective of this talk is subjective, namely to pick out for discussion a few topics which I find interesting.Presented at the Symposium on Hadron-Hadron Scattering at High Energies, Liblice, Czechoslovakia, June 16–21, 1975.     

The first target experiments on the National Ignition Facility

A first set of shock timing, laser-plasma interaction, hohlraum energetics and hydrodynamic experiments have been performed using the first 4 beams of the National Ignition Facility (NIF), in support of indirect drive Inertial Confinement Fusion (ICF) and High Energy Density Physics (HEDP). In parallel, a robust set of optical and X-ray spectrometers, interferometer, calorimeters and imagers have been activated. The experiments have been undertaken with laser powers and energies of up to 8 TW and 17 kJ in flattop and shaped 1–9 ns pulses focused with various beam smoothing options. The experiments have demonstrated excellent agreement between measured and predicted laser-target coupling in foils and hohlraums, even when extended to a longer pulse regime unattainable at previous laser facilities, validated the predicted effects of beam smoothing on intense laser beam propagation in long scale-length plasmas and begun to test 3D codes by extending the study of laser driven hydrodynamic jets to 3D geometries.     

ICF分解实验用双介质调制靶的研制

为了研究惯性约束聚变（ICF）实验用靶丸不同密度界面的流体力学不稳定性增长,设计并制备了聚苯乙烯（CH）/碳气凝胶（CRF）, CRF /硅气凝胶（SiO2）和CH/Al三种双介质调制靶。采用溶胶-凝胶工艺制备了密度分别为250和800 mg/cm3的CRF气凝胶薄片;采用激光微加工工艺分别在两种不同密度的CRF薄片和工业用纯Al箔上引入调制图形;采用旋涂工艺在Al箔和CRF薄片（250 mg/cm3）的调制表面制备一层CH薄膜,得到CH/Al和CH/CRF双介质调制靶,采用溶胶-凝胶工艺在CRF薄片（800 mg/cm3）表面制备一层低密度SiO2气凝胶,得到CRF/SiO2双介质调制靶。采用电子天平、扫描电子显微镜、工具显微镜和台阶仪对所制备的CH/CRF, CRF/SiO2和CH/Al三种双介质调制靶进行靶参数测量。结果表明:三种双介质调制靶层与层之间结合紧密,界面清晰,调制图形为正弦,靶参数测量准确。     

ICF分解实验用双介质调制靶的研制

为了研究惯性约束聚变(ICF)实验用靶丸不同密度界面的流体力学不稳定性增长,设计并制备了聚苯乙烯(CH)/碳气凝胶(CRF),CRF/硅气凝胶(SiO2)和CH/Al三种双介质调制靶。采用溶胶-凝胶工艺制备了密度分别为250和800mg/cm3的CRF气凝胶薄片;采用激光微加工工艺分别在两种不同密度的CRF薄片和工业用纯Al箔上引入调制图形;采用旋涂工艺在Al箔和CRF薄片(250mg/cm3)的调制表面制备一层CH薄膜,得到CH/Al和CH/CRF双介质调制靶,采用溶胶-凝胶工艺在CRF薄片(800mg/cm3)表面制备一层低密度SiO2气凝胶,得到CRF/SiO2双介质调制靶。采用电子天平、扫描电子显微镜、工具显微镜和台阶仪对所制备的CH/CRF,CRF/SiO2和CH/Al三种双介质调制靶进行靶参数测量。结果表明:三种双介质调制靶层与层之间结合紧密,界面清晰,调制图形为正弦,靶参数测量准确。     

Recent results from fixed target charm and beauty experiments

In the last year there have been new observations of beauty by two fixed target experiments (E672/706 and E653). A few new results on charm have recently been presented by the photoproduction experiment E687 and by E789 and E769. An intriguing result on the purely muonic decay of charm comes from the CERN experiment WA75. These results are summarized and we conclude with a hint of the promise of E791, the very high statistics charm experiment, which is beginning to produce physics results     

Foam target experiments with the PF-1000 plasma focus facility

This paper describes experiments on foam liners performed with the PF-1000 plasma focus facility. A streak camera has been used to observe interaction of a hydrogen plasma current sheath with a cylindrical foam target. It is shown that a thin foam liner can be uniformly imploded by a plasma focus current sheath. Received: 11 February 1999 / Received in final form: 30 March 1999     

ICF物理实验用纳米Cu块体靶材的制备研究

 采用自悬浮定向流法制备了金属纳米粉体并采用真空手套箱专利技术和冷压法在高压（1.5 GPa）作用下保压40 min后，成功制备出了相对密度达97％和显微硬度达1.85 GPa的金属Cu纳米晶材料。经XRD分析，其晶粒大小为20 nm。正电子湮没(PAS)实验结果表明，其空隙大小和数量与采用惰性气体冷凝法原位压制(IGC)的样品相比，空位簇数量较多，微空隙的大小和数量基本相当。激光惯性约束聚变（ICF）模拟实验表明：采用该方法制备的纳米Cu块体材料靶的激光转换效率比常规Cu材料靶高5倍。     

利用成像型速度干涉仪进行聚苯乙烯材料中冲击波调速的实验研究

利用一维实验,模拟了惯性约束聚变中烧蚀层中冲击波传输和多次冲击追赶过程.针对聚苯乙烯材料(CH)容易被X射线离化的问题,通过较详细的数值模拟,分析了用Au和Cu做阻挡层对冲击波信号的影响.利用两种不同的辐射源,研究了辐射源两个台阶强度变化对两次冲击信号的影响.经过分析,使用在Al基底上面加厚度为5 μm的Au膜以挡X射线的办法,获得了单次冲击在CH材料中加载和减速的清晰条纹图.利用在Al基底上加厚度为2 μm的Au膜和厚度为3 μm的Cu膜的方法,获得了两次冲击在CH材料中加速、减速和二次加载的条纹图.实 关键词： 光学诊断 冲击波调速 离化效应     

皮秒激光在激光状态方程靶制备中的应用

介绍了激光状态方程靶中金属薄膜台阶的切割方法。采用皮秒激光加工技术切割了宽度百μm量级的金属薄膜台阶,研究了金属薄膜台阶宽度控制的方法,讨论了切割过程中产生热效应的因素,优化了激光加工参数。实验加工中,采用加工的参数:功率为0.5W,脉宽10ps,波长355nm,扫描速率为100mm/s,获得了宽度400μm和120μm的金属薄膜。测量结果表明,金属薄膜的宽度能精确控制,切割后金属薄膜表面质量能保持切割前的质量。     

皮秒激光在激光状态方程靶制备中的应用

介绍了激光状态方程靶中金属薄膜台阶的切割方法。采用皮秒激光加工技术切割了宽度百m量级的金属薄膜台阶,研究了金属薄膜台阶宽度控制的方法,讨论了切割过程中产生热效应的因素,优化了激光加工参数。实验加工中,采用加工的参数：功率为0.5 W,脉宽10 ps,波长355 nm,扫描速率为100 mm/s,获得了宽度400 m和120 m的金属薄膜。测量结果表明,金属薄膜的宽度能精确控制,切割后金属薄膜表面质量能保持切割前的质量。     

神光-Ⅱ装置三倍频实验中靶场单元技术的改进

 主要介绍为了满足神光-Ⅱ高功率激光装置三倍频光（351nm，3ω）的物理实验要求，靶场三倍频模拟光源和瞄准监视系统两个主要单元技术的改进，即三倍频模拟光源由基频光（1 053nm，3ω）通过腔外的KTP+BBO晶体倍频获得，再经八路分光系统和主激光耦合；瞄准监视系统由透射式光学系统改进为反射式光学系统，避免原系统存在较大的色差，提高瞄准精度。     

First polar direct-drive exploding-pusher target experiments on the ShenGuang laser facility

Low density and low convergence implosion occurs in the exploding-pusher target experiment, and generates neutrons isotropically to develop a high yield platform.In order to validate the performance of ShenGuang(SG) laser facility and test nuclear diagnostics, all 48-beam lasers with an on-target energy of 48 kJ were firstly used to drive room-temperature, DT gas-filled glass targets.The optimization has been carried out and optimal drive uniformity was obtained by the combination of beam repointing and target.The final irradiation uniformity of less than 5% on polar direct-drive capsules of 540 μm in diameter was achieved, and the highest thermonuclear yield of the polar direct-drive DT fuel implosion at the SG was 1.04 × 10~(13).The experiment results show neutron yields severely depend on the irradiation uniformity and laser timing,and decrease with the increase of the diameter and fuel pressure of the target.The thin CH ablator does not impact the implosion performance, but the laser drive uniformity is important.The simulated results validate that the cos γ distribution laser design is reasonable and can achieve a symmetric pressure distribution.Further optimization will focus on measuring the symmetry of the hot spot by self-emission imaging, increasing the diameter, and decreasing the fuel pressure.     

CSRm内靶实验中的轻离子束流寿命模拟研究

 建立了内靶对兰州冷却储存环主环束流影响的单粒子跟踪模拟程序,对pellet小丸靶和碳靶对束流带来的负面影响进行了模拟研究,主要讨论CSRm内靶实验中的束流存活率和束流寿命状态。结果显示利用厚度为1×10¹⁶ atoms×cm^-2小丸内靶时,2.6 GeV质子束流寿命在100 s量级,而对于目前技术水平下的碳膜靶 (厚度为 5×10¹⁷ atoms×cm^-2),质子束流寿命为s量级;束流寿命和束流能量基本成正比关系,束流寿命和内靶厚度近似成反比关系。     

Measurement of filtration efficiency of Nuclepore filters challenged with polystyrene latex nanoparticles: experiments and modeling

Membrane filtration has been demonstrated to be effective for the removal of liquid-borne nanoparticles (NPs). Such technique can be applied to purify and disinfect drinking water as well as remove NPs in highly pure chemicals used in the industries. This study aims to study the filtration process of a model membrane filter, the Nuclepore filter. Experiments were carried out using standard filtration tools and the nanoparticle tracking analysis (NTA) technique was used to measure particle (50–500 nm) concentration upstream and downstream of the filter to determine the filtration efficiency. The NTA technique has been calibrated using 150-nm polystyrene latex particles to determine its accuracy of particle concentration measurement. Measurements were found reliable within a certain concentration limit (about 10⁸–10¹⁰ particles/cm³), which is dependent on the camera settings during the measurement. Experimental results are comparable with previously published data obtained using the aerosolization method, validating the capability of the NTA technique. The capillary tube model modified from that developed for aerosol filtration was found to be useful to represent the experimental results, when a sticking coefficient of 0.15 is incorporated. This suggests that only 15% of the particle collisions with the filter results in successful attachment. The small sticking coefficient found can be explained by the unfavorable surface interactions between the particles and the filter medium.     

Measuring deuteron beam parameters with solid-state track detectors in experiments with the QUINTA target assembly

The results of measurements of the beam parameters on the target upon irradiation of the QUINTA subcritical uranium assembly with deuterons with energies of 1, 4, and 8 GeV are presented. Data on the position of the incident particle beam relative to the assembly axis and on the actual geometric parameters of the beam make it possible to analyze information on the spatial distributions of reaction rates within the target assembly correctly, comparing such distributions obtained at different irradiation sessions and modeling the experiments with the use of MCNPX, GEANT4, FLUKA, and other similar software tools.     

Laser ablation of a molten Ga target; comparison of experiments and simulation

The laser ablation mechanism of a molten Ga target was examined through comparison of experiments and simulation. The ablation was performed using an ArF excimer laser (193-nm wavelength and 20-ns duration) in vacuum. The observed existence of the threshold laser fluence (necessary for onset of the ablation) and linear increases in both the Ga deposition rate and the Ga emission (fluorescence) intensity with the laser fluence were satisfactorily explained by the simulation based on the thermal ablation model. In addition, it was found that most of the ablated particles are transferred to the substrate not in the form of an excited ion but an excited neutral atom, except at and near the target. Received: 3 September 2001 / Accepted: 7 November 2001 / Published online: 20 December 2001