核電工程外文翻譯----國際空間站(空間站)上進(jìn)行的阿爾法磁譜儀(ams02)實(shí)驗(yàn)

1、<p><b>　　翻譯原文</b></p><p>　　Alpha Magnetic Spectrometer(AMS02)experiment on the International Space Station (ISS)</p><p>　　Abstract The Alpha Magnetic Spectrometer experiment

2、is realized in two phases. A precursor flight (STS-91) with a reduced experimental configuration (AMS01) has successfully flown on space shuttle Discovery in June 1998.The final version (AMS02) will be installed on the I

3、nternational Space Station (ISS) as an independent module in</p><p>　　early 2006 for an operational period of three years. The main scientific objectives of AMS02 include the searches for the antimatter and

4、dark matter in cosmic rays. In this work we will discuss the experimental details as well as the improved physics capabilities of AMS02 on ISS.</p><p>　　Keywords Alpha Magnetic Spectrometer, International S

5、pace Station, Antimatter, Dark matter</p><p>　　Introduction</p><p>　　A possible existence of cosmologically large domains of antimatter or astronomical "anti objects" and the nature of

6、 dark matter in the universe are fundamental questions of the modern astroparticle physics and cosmology.</p><p>　　The AMS02 experiment thanks to its large acceptance (~0.65 m2) and its particle identificati

7、on capability, will study these fundamental aspects with unprecedented sensitivity. This requires the measurement of the physical quantities such as particle momentum, charge and velocity with highest possible degree of

8、confidence.</p><p>　　An unambiguous proof of existence of cosmicantimatter would be observation of antinuclei (Z>2)in cosmic rays. An observation even of a single antihelium or heavier nuclei would demons

9、trate that primordial antimatter indeed exists and it is not too far from us. The AMS02 will be able to distinguish a single antihelium nuclei among~10^9 estimated background particles over 3 years.</p><p&

10、gt;　　The project is realized in two phases. In June 1998, a baseline configuration of the experiment has down on the space shuttle Discovery for 10 days mission on 51.70 orbit at altitudes between 320 and 390km. From thi

11、s mission (STS-91) we gathered precious information on detector performance in actual space conditions and on possible background sources. </p><p>　　AMS01 has also measured,

12、for the first time, with such an accuracy from space, cosmic ray fluxes in GeV region covering almost the whole Earth surface.The detector layout, performance and the physics resuits of AMSO1 during STS-91 flight (AMS-0l

13、 ) are described in detail elsewhere.</p><p>　　In this work we will discuss the experimental configuration as well as the physics capabilities of AMS02 on the international Space Station.</p><p>

14、;　　2.Details of the AMS02 experiment </p><p>　　The AMS02 is a large acceptance, high precision superconducting magnetic spectrometer designed to measure cosmic ray spectra of individual elements with Z<

15、;--25 up to TeV region. It can also measure the high energy gamma rays up to few hundreds GeV with very good y source pointing capability. Fig.l shows the details of AMS02 experiment.</p><p>　　There are a

16、total of 227,300 electronics channels each providing 16 bits of information with event rates up to 2 kH corresponding to a total raw data rate of over 1 Gbit/s. The DAQ electronics will reduce the event size, through pro

17、per filtering, to the allocated downlink data rate of 2 Mbit/s.</p><p>　　All electronics and mechanical parts of AMS02 are tested for operation in vacuum. The effect of total ionization dose (up to 6 Gy/yea

18、r) on all critical components is extensively tested.</p><p>　　The detector has been designed to identify the cosmic rays but at the same time minimizing the multiple scattering and large angle nuclear scatt

19、ering occurring inside the tracking part of the detector. Large acceptance for antihelium search, good particle rigidity and velocity resolutions as well as their redundant measurements and h/e rejection of >10^6 were

20、 other key parameters for its design.</p><p>　　The AMS02 will weigh 6760 kg and will have a power consumption of 2 kW.</p><p>　　In the following the AMS02 sub-detectors will be described from up

21、 to downstream. 2.1 Transition Radiation Detector (TRD) </p><p>　　The Transition Radiation Detector is designed to separate a/p signals to distinguish e+ and p from relative backgrounds (p and e一respectiv

22、ely) with a rejection factor of 103一 102 in the energy range from 10~300 GeV. This rejection factor combined with the Electromagnetic Calorimeter will provide an over-all e+/p rejection factor of 10^6 at 90% of e+ effic

23、iency.</p><p>　　The detector consists of 20 layers of 6 mm diameter straw tubes alternating with 20 mm layers of 10 hum polyethylene/polypropylene fiber radiator. The tubes are filled with a 80%~ 20% m

24、ixture of Xe÷CO2 at 1 bar from a recirculating gas system designed to operate in space for>3 years. The wall material of straw tubes is a 72 μm kapton foil. The upper and lower 4 layers run in the x direction (p

25、arallel to AMS02 magnetic field) while central layers run in the perpendicular y direction to pro</p><p>　　2.2 Time of Flight (ToF) system</p><p>　　The ToF system is designed to provide fast (

26、first level) trigger to the experiment, measurement of time of flight of the particles traversing the detector with up/down separation better than 10-g, the measurement of the absolute charge of the particle (in addition

27、 to dE/dX measured from the Silicon Tracker) and the identification of electrons and positron from antiprotons and protons up to 1--2 GeV. The expected overall time resolution is≈ 140 ps for protons and better for heavie

28、r cosmic ray nuc</p><p>　　2.3 Superconducting Magnet (SCM) </p><p>　　One of the challenging features of the AMS02 detector is its strong superconducting magnet. It is the first large sup

29、erconducting magnet used in space and it has a bending power of B}LZ } 0.8 Tm^2 which will be essential to perform a sensitive search for antimatter(He)in the rigidity (p/Z) range from 0.1 GV to several TV.</p>&l

30、t;p>　　The magnet consists of 2}dipole coils together with 2 sets of smaller racetrack coils (see Fig.5) with a total cold mass of about 2300 kg. The racetrack coils is designed to increase the overall dipole field, to

31、 minimize the stray dipole field outside the magnet (max stray field at a radius of 3 m is 4 mT) in order to avoid an undesirable torque on the ISS caused by the interaction with the Earth magnetic field. All coils are

32、wound from high purity aluminum-stabilized niobium-titanium conductor</p><p>　　2.4 Anticoincidence (AC)</p><p>　　The AMS02 anticoincidence system (Fig.6) is designed to assure to trigger only

33、on those particles passing through the aperture of the AMS02 superconducting magnet. It is placed inside the magnet free bore covering the inner surface of the superconducting magnet. AC system consists of thin scintilla

34、tor slabs readout on both ends by PMs.</p><p>　　2.5 Silicon Tracker (ST) </p><p>　　The Silicon Tracker of AMS02 is designed to perform high precision measurements of the rigidity he sign of c

35、harge and the absolute charge of the particle traversing it.</p><p>　　There are a total of 192 ladders with variable number of silicon ensors glued together and readout on one extremity y the front-end elect

36、ronics. The lengths of the ladders vary from 36 cm to about with 60 cm (active part)corresponding to ≈6.4 m^2 of active double sided surface. Fig.8 shows a detailed design of a ladder and its main components.</p>

37、<p>　　One of the key points in the assembling of long ladders is that it requires high precision in cutting of the sensors and during the ladder assembly. Fig.9 shows the differences between measured (through refer

38、ence crosses on each sensor) and nominal (perfectly aligned) positions of the sensors of 73 ladders.</p><p>　　The r.m.s. of distribution is about 4 μm. The readout electronics is based on low noise,low power

39、 (~0.7 mW/ch), high dynamic range(士70MIPs) VA_ HDR VLSI, preamplifier, shaper, sample and hold circuit connected to the silicon sensors through 700 pF decoupling capacitors.</p><p>　　The performance of the A

40、MS02 ladders has been tested with minimum ionizing particles and with heavy ions.Fig.10 shows the residuals of the reconstructed and expected positions of 400 GeV muons traversing the prototype ladders. The resultin

41、g spatial resolutions are on bending (non bending) directions for 400 GeV muons and 20 GeV/A helium particles respectively.The tracker cooling system bases on variable conductive heat-pipes in which the cooling fluid (C0

42、2) runs by the capillary forces. The</p><p>　　The particle identification capabilities of the AMS-U2 proximity focused RICH detector will improve the confidence in the determination of the sign of the charg

43、e, will provide high level of redundancy required for high purity samples of positrons and antiprotons, will perform the identification of isotopes of mass A<~15-20, over a momentum range 1 GeV/c <p/A<-12 GeV/c

44、 and will identify the chemical composition of elements up to Fe (Z--26) to the upper rigidity limit of the spectrometer, p/Z<</p><p>　　The AMS02 RICH detector consists of a plane of radiator material,

45、separated from the detector plane by a drift space in which Cherenkov rings can expand. A detector module includes a matrix of light guides coupled to a PM (Hamamatsu 87900-00-M16) connected to a socket and front-end ele

46、ctronics readout.</p><p>　　The choice made by the Collaboration is to have an Aerogel radiator 3 cm thick with n=1.05 in order to cover the momentum interval with a velocity resolutionΔβ/β of about 1.5 * 10^

47、3. In addition an 0.5 cm thick NaF placed at the central square, corresponding to the hole in the pixels plane, will improve the detection of particles traveling to the central hole direction.</p><p>　　Since

48、 the Electromagnetic Calorimeter (ECAL) is located just below the RICH photomultipliers plane, the plane is designed with a central hole in order to avoid passive materials in front of ECAL. Fig.14 shows a 3-D design of

49、RICH counter along with the performance test results obtained during the CERN SPS Test beam.</p><p>　　Electromagnetic Calorimeter (ECAL) </p><p>　　In order to achieve good a/p separation (des

50、ign rejection factor of一105) which is essential to perform accurate measurement of positron spectra (from few GeV up to一1 TeV), AMS02 comprises a fine grained sampling electromagnetic calorimeter (ECAL) capable of 3-D im

51、aging of the shower development and of discrimination between hadronic and electromagnetic cascades.</p><p>　　ECAL is a sampling device with a lead-scintillating fibers structure. It has a square parallelepi

52、ped shape with 65.8 cm side and 16.5 cm depth. It is segmented in 9 superlayers along its depth and each superlayer, of 18.5 mm total thickness, contains 11 grooved lead foils interleaved with 1 mm diameter scintillating

53、 fibers glued with an epoxy resin (average superlayer density of --6.8 1 0.3 g/cm3). The calorimeter has a radiation length of about l0mm, total thickness of almost 16 radiation lengt</p><p>　　2.8 Star track

54、er (AMICA) </p><p>　　The main purpose of Astro Mapper for Instrument Check of Attitude (AMICA) is to provide accurate pointing direction for AMS02. AMICA will give a precise measurement of the AMS02 observin

55、g direction with a few arc-sec accuracy. The electronics unit is based on a VME bus which contains the processor (DSP21020) and housebeeping boards. </p><p>　　3 AMS02 Physics</p><p>　　3.1 An

56、timatter search</p><p>　　Our region of the universe is certainly dominated by matter. Tiny amount of antiprotons and positrons present in cosmic rays can be explained as secondaries of ordinary matter (proto

57、ns, electrons and nuclei consisting in protons and neutrons) and gamma rays interacting with interstellar material. At present day, from the direct observation we have Ny= 411.4/cm^3 and NB-> NB (at least in our neigh

58、borhood). According to Sakharov,}'4} to generate the baryon asymmetry three principles of karyogenesi</p><p>　　It has been shown that the ratio of extragalactic/galactic cosmic rays should increase with

59、energy owing to the fact that the escape rate of the galactic cosmic rays from the galaxy </p><p>　　increases with energy. It is also argued that the galactic wind impedes the entrance of extragalactic cosm

60、ic rays and the cosmic rays may not propagate towards the Earth from tens of Mpc as required by some models. On the other hand it would not be accurate to estimate from how far the extragalactic nuclei can reach the Eart

61、h since we have very limited knowledge about the extragalactic field strength. It is however true stating that more sensitive test for extragalactic antimatter can be done at</p><p>　　Until recently, the sea

62、rch for antinuclei and antiproton has been carried out by stratospheric balloons,and on spacecrafts and no antinuclei was observed. The limits on antihelium/helium ratio published by various.</p><p>　　Dark m

63、atter</p><p>　　The observation of stars in spiral galaxies enable rotational velocities of stars to calculate the mean density of the matter as a function of the distance from the galactic center. From the r

64、ecent WMAP measurements of Cosmic Microwave Background (CMB) anisotropies, the total amount of matter is close to the critical density for a flat Universe with matter=0.27 1 0.04. The contribution of the luminous matte

65、r (stars, emitting clouds of gases) isΩ<0.01 and a precise determination of primeval abu</p><p>　　The stable cosmic ray species generated in neutralino annihilations include gamma rays, neutrinos,positron

66、s, antiprotons and antideuterons and, in the same amounts, their counterparts with opposite lepton and baryon numbers.</p><p>　　In the following we will discuss AMS02's capabilities, being the unique exp

67、eriment to measure all neutralino annihilation products (except neutrinos) with the same apparatus.</p><p>　　3.2.1 Gamma rays </p><p>　　The gamma rays are important tracers to probe the high

68、energy processes in Universe. They travel over the entire Universe along straight lines without significant absorption and transport information about high/extreme energy interactions, objects or events from distant doma

69、ins. Among proposed dark matter gamma ray sources, there are the Galactic center, the whole Milky Way halo, external galaxies and cosmological sources.</p><p>　　About 20~30% of the energy released in WIMP an

70、nihilations goes into gamma rays. Most of them (-90%) are generated in the decay of neutral pions in fragmentation processes.</p><p>　　A compilation of estimates of flux sensitivities is given in Fig.20 for

71、space borne (upper,left part in the Figure) and Earth based (lower right) experiments showing which will be the progress in next decade arid what signal levels will be.</p><p>　　Most of the high energy gamm

72、a ray data come from EGRET experiment on Gamma Ray Observatory (GRO). After the completion of GRO program (in June 2000) there is no experiment measuring high energy gamma rays in space. In upcoming decade there will be

73、three experiments, AGILE (in 2004), AMS02 on ISS and GLAST (2007) which will be able to cover the energy spectrum region from 20 MeV up to about 300 GeV.</p><p>　　Despite their low flux, high energy gamma ra

74、ys bring valuable information complementary to those gathered from charged particles. Since they do not deflect on their path during the travel in the (inter) galactic magnetic field, it is possible to point to the galac

75、tic or extra galactic source directions. A good source pointing and capability to perform accurate spectral studies require good angular and energy resolutions respectively.</p><p>　　3.2.2 Antiprotons</

76、p><p>　　Calculation of secondary antiprotons, due to interactions of cosmic rays with Interstellar material,have greatly improved in recent years}4a,as1 and have shown that at low energy (below kinematic limit)

77、 the secondary spectrum is much flatter than previously believed and fits remarkably well the experimental data.}46} This makes the extraction of supersymmetric signal from the background more difficult. Although the mea

78、sured antiproton flux gives rather stringent limits on MSSM models with the hi</p><p>　　Fig.21 shows antiproton/proton ratio given by balloon experiments together with predictions by theoretical calculati

79、ons. Solid curves are upper and lower limit assuming secondary production only. Dashed curve is a similar calculation by L. Bergstrom and P. Ullio.</p><p>　　Instead, Fig.22 includes few thousands of antiprot

80、ons measured during last four decades by balloon borne experiments as well as AMSO1.The errors (both statistic and systematic) are larger at higher energies. The figure shows also the AMS02 capability to extend the energ

81、y range up to about 300 GeV with much higher statistics.</p><p>　　3.2.3 Electrons and Positrons</p><p>　　There has been a measurement in a balloon-borne experiment (HEAT) with an excess of pos

82、itrons around 7 GeV over that expected from ordinary sources. However, since there are many other possibilities to create positrons by astrophysical the interpretation is not yet conclusive. The measurement of positron i

83、ndication for neutralinos spectra could give sources accurate a clear annihilation with rather precise determination of the neutralinos mass.</p><p>　　3.2.4 Antideuterons</p><p>　　Antideuteron

84、production from proton-proton collisions is a rare process and it may be less rare in neutralinos annihilation and recently has been pointed out that antideuterons in space could be more promising probe to look for the

85、 exotic sources than antiprotons.In particular considering the WIMP pair annihilation in the galactic halo, at energies below about 1 GeV per nucleon the primary antideuteron spectrum would be quite dominant over the sec

86、ondary one (see Fig.24). The antideuterons meas</p><p>　　The study of relative abundances of elements and isotopes will yield to a better understanding of origin, propagation, acceleration and confinement ti

87、me of cosmic rays in our galaxy. The presence of Earth atmosphere restricts this kind of measurements to be carried out at high altitudes with as low as possible residual atmosphere or better, in space where the effect

88、of Earth's atmosphere is negligible. Nowadays, the experiments aiming to perform elemental and isotopic measurements have suffered</p><p>　　In galactic cosmic ray propagation models the diffusion coeffic

89、ient as a function of momentum and the reacceleration are determined by the energy dependence of B/C ratio. The radioactive nuclei data are used, instead to derive a range for the height of the cosmic ray halo as well as

90、 to determine the residence time of the galactic cosmic rays in different propagation models. 4 Conclusions </p><p>　　The AMS02 is scheduled for installation on the main external truss of the International

91、 Space Station in early 2006. Its three years exposure, large acceptance, state-of-art detectors and. superconducting magnet will allow accurate measurements of cosmic rays up to the unexplored TeV region.</p>&l

92、t;p>　　AMS02 will accurately measure the light element fluxes which are essential for better understanding of cosmic ray origin, propagation, and acceleration mechanisms .</p><p>　　AMS02 will search fo

93、r cosmological antimatter (antihelium and anamson) with unprecedented sensitivity. It is worth underlining that, among those planned for next decade, it will be the unique detector capable of measuring simultaneou

94、sly four different rare products of } annihilation. In addition the AMS02 will open up a window on exotic/other physics such as the study of strangelets.</p><p><b>　　翻譯中文</b></p><

95、;p>　　國際空間站(空間站)上進(jìn)行的阿爾法磁譜儀(ams02)實(shí)驗(yàn)</p><p>　　摘要:阿爾法磁譜儀實(shí)驗(yàn)基于兩種實(shí)驗(yàn)現(xiàn)象.</p><p>　　簡化實(shí)驗(yàn)配置(ams01)的首次航行(sts-91)已經(jīng)在1996年6月在發(fā)現(xiàn)號(hào)航天飛機(jī)上成功進(jìn)行.實(shí)驗(yàn)儀器配置的最終版本(ams02)將被安裝在國際空間站(空間站)作為一個(gè)獨(dú)立的模塊,2006年初在經(jīng)營期三年.ams02的主要科學(xué)目

96、標(biāo)包括尋找反物質(zhì)和暗物質(zhì)在宇宙射線.在這項(xiàng)工作中我們將討論實(shí)驗(yàn)的細(xì)節(jié)比如說在在國際空間站上如何改進(jìn)ams02的物理性能.</p><p>　　關(guān)鍵詞:阿爾法磁譜儀,國際空間站,反物質(zhì),暗物質(zhì)</p><p><b>　　1簡介</b></p><p>　　一個(gè)可能存在于宇宙學(xué)領(lǐng)域的反物質(zhì)或天文“反”的對(duì)象和性質(zhì)的暗物質(zhì)在宇宙中是現(xiàn)代天體物理學(xué)和

97、宇宙學(xué)的根本問題.</p><p>　　該阿爾法磁譜儀實(shí)驗(yàn)由于其大接受范圍(~0.65平方米)和較強(qiáng)的粒子的識(shí)別能力,將這些基本方面以前所未有的靈敏度研究.這要求測(cè)量的物理量如粒子的動(dòng)量,電荷和速度與最高程度的信心.</p><p>　　一個(gè)明確的證明存在宇宙反物質(zhì)會(huì)觀察反物質(zhì)核在宇宙射線.一個(gè)觀察一個(gè)單一反氦或較重的原子核,表明原始反物質(zhì)確實(shí)存在,它是離我們不遠(yuǎn)的.該阿爾法磁譜儀02將能

98、夠在10^9個(gè)氦核區(qū)分一個(gè)反氦核之間的~估計(jì)背景顆粒超過3年.</p><p>　　該項(xiàng)目的目的是實(shí)現(xiàn)兩相.1998年六月,基線配置實(shí)驗(yàn)在發(fā)現(xiàn)號(hào)航天飛機(jī)任務(wù)10天51.70軌道在海拔320到390公里之間.從這個(gè)使命(sts-91)我們收集的珍貴信息探測(cè)器性能在實(shí)際空間的條件和可能的來源的背景.</p><p>　　阿爾法磁譜儀一號(hào)也測(cè)量,為第一時(shí)間,準(zhǔn)確性等空間,宇宙射線通量電子伏特地區(qū)