PULSED EMISSION OF VERY HIGH ENERGY GAMMA RAYS FROM CRAB PULSAR

We present here the results of observation of very high energy(VHE) gamma-ray emission from Crab Pulsar with the Beijing Atmospheric Cerenkov Telescopes, named ACT2 and ACT3, during the 1995－1996 season. The data are based on 168 h (ACT2) and 125 h (ACT3) of exposure over the period of observation in tracking mode. After converting the event time to the solar barycentre, the data have been searched for evidence of pulsed emission at 33 ms period of Crab Pulsar. We found no steady emission of VHE Gamma-ray with 33 ms period at the time scale of month or nights. But there are two evidences of sporadic emission over an hour duration with the same period as the one at radio wave band.     

寻找来自原始黑洞蒸发的TeV γ射线暴

用兴隆站的两台大气切伦科夫望远镜ACT2和ACT3在1995—1997年间的观测数据,寻找来自原始黑洞(PBH)蒸发终态的0.1sTeVγ射线暴.分析这些资料没发现有这样的γ射线暴.据此估算出在太阳系附近、在99%的置信水平下原始黑洞的蒸发率-密度的上限为3×10⁸/年·pc3.     

观测来自银道面的TeV γ射线

给出来自银经79.3866°的银道面的TeV γ射线的观测结果.数据是在1995年10月至1998年11月间的晴朗无月夜,用兴隆站的大气契伦科夫望远镜ACT2和ACT3以向源–背景(ON–OFF)观测方式取得的,总观测时间为224.4h.在望远镜计数服从高斯分布的情况下,导出了最大似然比λ的表达式,它直接给出显著性水平的概率.用它分析观测资料,在统计误差范围内没发现有来自银道面的TeV γ射线.     

用微扰增强双共振对Na_22~3Π_g和3~3Π_g能级进行新观测(英文)

Na2 2 3 Πg 和 33 Πg 态在 3486 0cm-1(相对基态Te)和 3s+3d解离限之间的Ω =0 ,1,2能级进行了脉冲激光微扰增强双共振探测 .观测到两个态之间强烈的相互微扰 .给出忽略微扰情况下Ω =0能级的Tv 和Bv.     

相界附近Pb(Zn1/3Nb2/3)O3-PbZrO3-PbTiO3固溶体的弛豫相变研究

利用常规电子陶瓷工艺在相界附近合成得到纯钙钛矿相的Pb(Zn1/3Nb2/3)O3PbZrO3PbTiO3(PZNPZT)三元系固溶体,其相界位于Zr/Ti比37/33处.在实验中发现和证实了相界附近PZNPZT三元系固溶体存在铁电弛豫顺电相变.在极化后Zr/Ti比为37/33及39/31PZNPZT样品的介电温度谱观测到菱方四方相相变,认为PZNPZT固溶体相界是向富Zr区弯曲. 关键词：     

延迟质子先驱核~(33)Ar、~(49)Fe的实验研究

用65MeV的~(12)C束轰击~(24)Mg、~(40)Ca靶,通过(~(12)C,3n)反应,产生了延迟质子先驱核~(33)Ar及~(49)Fe,观测了它们的β~ 延迟质子谱,其主峰能量分别在3.28±0.07MeV与1.98±0.04MeV,截面分别为0.4±0.08μb与0.7±0.14μb,测得~(33)Ar的半衰期为167±24ms。     

Yb3+掺杂铝氟磷酸盐玻璃的光谱和激光性能

研究了Yb3 掺杂铝氟磷酸盐 (AFP)玻璃的吸收光谱、荧光光谱 ,测量了Yb3 离子的荧光有效线宽 (Δλeff>5 5nm)以及2 F5 2 能级的荧光寿命 (τmax=2ms)及随掺杂浓度的变化 .应用倒易法计算了Yb3 的发射截面 ,其发射截面可达 0 6 6 82 3pm2 ,且激光增益系数τfσemi达 1 2 89ms.pm2 .评估了Yb3 在AFP玻璃中的激光性能 ,发现其具有较理想的激发态最小粒子数 (0 15 )、饱和抽运强度 (8 3kW cm2 )和最小抽运强度 (1 2 4 5kW cm2 )值及良好的热稳定性 .研究结果表明掺Yb3 氟磷酸盐玻璃是实现高功率超短可调谐激光器的理想增益介质 .     

Nd_(1.67)Sr_(0.33)NiO_4中的热导反常

报道了两个典型掺杂的镍氧化物Nd2 -xSrxNiO4 (x=0 33,1 35 )的低温热导率、电阻率和低场交流磁化率 ,测试温区为 77— 30 0K .在Nd2 -xSrxNiO4 (x=0 33)样品的热导率_温度曲线上在电荷有序转变温度 (TCO)和自旋有序转变温度 (TSO)附近分别观测到反常 ,电荷有序使热导率在TCO 以下有所增加 ,反铁磁自旋有序使热导率在TSO 附近被压制 .在低场交流磁化率_温度曲线上也分别观测到对电荷有序和自旋有序的响应 ,而在其电阻率_温度曲线上仅观测到电荷有序 .作为比较 ,Nd0 6 5Sr1 35NiO4 样品中没有观测到输运性质和磁性质上的反常 .两个样品中声子热导占主导地位 .Nd1 6 7Sr0 33NiO4 样品中电荷有序和自旋有序导致的热导率的反常表明样品中存在强的电荷_声子和自旋_声子相互作用     

HL-2Aװ��ʵʱ��������λ���ؽ�ϵͳ�ļ����Ż�

现有的HL-2A实时平衡重建系统采用的是网格尺寸为33×33,将无法满足HL-2M装置对控制精度和速度要求.为此开发了网格尺寸为129×129的重建系统,并通过GPU并行、算法重构等优化方法,使得新的重建系统在保证计算精度的情况下能够使得每一次平均重建计算维持在600μs内,可满足HL-2A和HL-2M中周期为1ms等离子体控制系统对重建系统精度和速度要求.     

为什么生理节奏不是24小时?

人们发现大多数生物的生物钟周期约为 2 2— 2 8小时 ,很少有生物钟正好是 2 4小时的种族 .这一点让人不可思议 ,因为从光线的强弱和温度的变化来说 ,种族的生物钟应该与地球自转的周期同步才便于与环境的协调并组织自身的日常活动 .为了研究这个论点 ,日本大阪大学的物理学家Ｈ .Ｄｉａｄｏ设计了一个数学模型来研究具有不同生物周期的种族间的竞争。在他的模型中有两点重要的假定 :首先他假定种族的繁殖率依赖于它的生物钟的时间与 2 4小时之间的差 ,如正好是 2 4小时的话 ,其繁殖率为最大 ,因为这类种族在白天要受到紫外线的伤害 .其次他…     

Pulsed Emission of Very High Energy Gamma-Rays From Crab Pulsar

We present here the results of observation of- very high energy(VHE) gamma-ray emission from Crab Pulsar with Beijing Atmospheric Cerenkov Telescopes, named ACT2 and ACT3, for the duration of the fall 1995-spring 1996 season. The data are based on 168 hours (ACT2) and 125 hours (ACT3) of exposure over the period of observation in tracking model. After conversion the event time to the solar barycenter, the data have been searched for evidence of pulsed emission at 33ms period of Crab Pulsar, We found no steady emission of VHE Gamma-ray with 33ms period at the scale of month or night. But there are two evidences of sporadic emission over an hour duration with the same period as the one at radio frequency.     

寻找超高能宇宙线源——西藏广延空气簇射实验

总结了１９９０年６月到１９９３年１０月期间西藏空气簇射阵列的观测结果。寻找了来自于蟹状星云、Ｘ射线双星、脉冲星、活动星系核和其它活动天体的能量为１０ＴｅＶγ射线连续发射，没有发现连续稳定发射的迹象，但给出了每个源的流强上限。在阵列所观测的天区寻找了１０ＴｅＶ的γ暴，结果没有发现能量１０ＴｅＶ的γ暴，最后也给出了发现此种γ暴的上限。应用该阵列，明显地观测到了能量为１０ＴｅＶ的宇宙线流强的太阳和月亮阴影。观测了朝向和远离太阳的行星际空间磁场对宇宙线阴影的影响，这是行星际磁场对阴影位移影响的第一次直接观测。研究并发现在实验期间，太阳阴影的位置每年都在变化。同时观测在此期间，朝向和远离方向的宇宙线阴影的不同变化。另外，应用该实验的数据，给出了所谓的“膝”区的原初宇宙线能谱。     

VHE gamma-ray sources and implications

Summary This paper highlights the status of very high-energy (VHE) gamma-ray astronomy with emphasis on the astrophysical significance of the discovery of TeV γ-radiation from four celestial objects, Crab Nebula, PSR B1706-44, Mrk 421 and Mrk 501, detected at very high confidence levels using the atmospheric Cherenkov imaging technique. Paper presented at the Special Session on ground-based gamma-ray astronomy of the XXIV International Cosmic-Ray Conference, Rome, August 28–September 8, 1995.     

Temporal integration in normal hearing, cochlear impairment, and impairment simulated by masking

To assess temporal integration in normal hearing, cochlear impairment, and impairment simulated by masking, absolute thresholds for tones were measured as a function of duration. Durations ranged from 500 ms down to 15 ms at 0.25 kHz, 8 ms at 1 kHz, and 2 ms at 4 and 14 kHz. An adaptive 2I, 2AFC procedure with feedback was used. On each trial, two 500-ms observation intervals, marked by lights, were presented with an interstimulus interval of 250 ms. The monaural signal was presented in the temporal center of one observation interval. The results for five normal and six impaired listeners show: (1) normal listeners' thresholds decrease by about 8 to 10 dB per decade of duration, as expected; (2) listeners with cochlear impairments generally show less temporal integration than normal listeners; and (3) listeners with impairments simulated using masking noise generally show the same amount of temporal integration as normal listeners tested in the quiet. The difference between real and simulated impairments indicates that the reduced temporal integration observed in impaired listeners probably is not due to splatter of energy to frequency regions where thresholds are low, but reflects reduced temporal integration per se.     

Ground-based gamma-ray astronomy

Summary This report covers developments in the field of gamma-ray astronomy, essentially in the energy range 300 GeV to 300 TeV, reported at the XXIV International Cosmic-Ray Conference in Rome in 1995. Highlights which receive the main attention are the failure of several experiments to detect TeV photons from several supernova remnants at the level predicted on current models of shock acceleration of cosmic-ray protons, and the detection of a rapidly variable flaring output of TeV photons from two BL Lac objects (Markarian 421 and Markarian 501). Although techniques are now maturing to the extent that different measurements of the flux and spectrum from the Crab Nebula are now converging, unresolved differences remain over the existence of TeV pulses from certain pulsars. However, one well-supported instance of very intense pulsation for an hour from AE Aquarii was presented. The Vela Pulsar was reported as a steady source. Rapporteur talk given at the XXIV International Cosmic-Ray Conference, Rome, August 28–September 8, 1995.     

一种聚焦型X射线探测器在轨性能标定方法

X射线探测器是X射线天文观测及脉冲星导航的核心器件,受发射振动、高能粒子辐射损伤及元器件老化等影响,X射线探测器空间观测性能会逐渐变化,X射线探测器在轨标定有利于观测天体X射线辐射信息的准确获取及精确建模.研究利用了脉冲星辐射能谱标定X射线探测器性能的方法,能较好地消除探测器本底及空间环境噪声的影响,通过处理脉冲星导航试验卫星(XPNAV-1卫星)的Crab脉冲星观测数据,评估了我国首款聚焦型X射线探测器的在轨性能.计算结果表明,XPNAV-1卫星上聚焦型X射线探测器的有效面积在0.6-1.9 keV能段内优于2 cm~2,其中在0.7 keV能量处取得最大值3.06 cm~2,探测效率约10%;有效面积随着探测能量增大而减小,在2—3.5 keV能段内有效面积约为1 cm~2,而大于5 keV能段的有效面积约为0.1 cm~2,且此能段估计精度明显受光子统计误差影响.同时研究了考虑能量响应矩阵的探测器有效面积标定新方法,利用地面性能测试中五个特征能谱处的能量分辨率重构其能量响应矩阵,重新标定了聚焦型X射线探测器有效面积,发现该能量响应矩阵对结果影响较小.最后建议观测某些超新星遗迹监测能量分辨率及能量线性等指标的变化.     

Pulsar search in M33

Summary In this paper we describe the scientific goals and the experimental set-up of the projectPulsar search in M33. Its aim is the discovery of radio pulsars in the Scd spiral Galaxy M33 (NGC 598). A complete survey of the H _a area of M33, with an exagonal grid somewhat less than one-half power of the Arecibo telescope at 1400 MHz, has been performed and about 100 observations over the 40% of the grid areas are now available. An improved version of the analysis procedure has been realized and is shortly described in the following. Some considerations about the detectability of pulsars eventually present in M33 are reported. Paper presented at the 6th Cosmic Physics National Conference, Palermo, 3–7 November 1992.     

Stellar X-ray polarimetry

Summary Stellar X-ray polarimetry has for a long time been indicated as a very powerful diagnostic tool. In spite of this widely recognised interest, positive results are limited to just one: the detection, in the now far 1978, of the polarisation of the X-ray emission from the Crab Nebula. Novel-generation experiments promise a wider and richer amount mess of results, at least for strong galactic sources. Polarimetry however, remains an unusually delicate technique that requires a very tight control of systematic effects (at the level of 1% or better) over the very long observing period (10⁵ seconds or more) needed for obtaining a reasonable sensitivity. Paper presented at the 6th Cosmic Physics National Conference, Palermo, 3–7 November 1992.     

The possibility of searching for new physics in cosmic rays

One possible explanation of cosmic-ray energy spectrum behavior around the knee (3–5 PeV) by means of production of new heavy particles or a new state of matter is considered. It is shown that, in this case, a large excess of muons and neutrinos with energies of >100 TeV must be generated. The existing VHE muon experimental data are analyzed. Possible experiments on VHE muon investigations are discussed.     

X射线脉冲轮廓稳定性对导航精度的影响

X射线脉冲星具有广阔的导航应用前景,稳定的脉冲轮廓是自主导航的基础,然而在X射线脉冲轮廓的稳定性及其对导航精度的影响方面一直缺乏系统的研究.采用Pearson相关系数、标准偏差及功率谱熵三组指标量化脉冲轮廓的稳定性.利用罗西X射线计时探测器卫星X射线段(2—16 keV)11年的观测资料,统计了包括周期跃变在内的Crab脉冲轮廓稳定性.在此基础上,引入Cramer-Rao理论建立了脉冲轮廓稳定性对距离测量误差影响的数学模型,并通过分析各误差因素确定脉冲轮廓稳定性对距离测量误差的影响范围.实测数据处理表明,Crab脉冲星的X射线脉冲轮廓具有极高的稳定性,跃变期间脉冲轮廓无明显变化,脉冲轮廓的稳定性导致沿脉冲星方向上产生34 m±25 m的距离测量误差.