& 2013 - 2014 作业宝. All Rights Reserved. 沪ICP备号-9The Ring Imaging Cherenkov detector of the AMS experiment test beam results with a prototyp85
上亿文档资料，等你来发现
The Ring Imaging Cherenkov detector of the AMS experiment test beam results with a prototyp85
002naJ92]hp-ortsa[1v4844；Lu′?saArrudaa,；FernandoBar?aoa,Patr′?ci；LIP/IST；Av.EliasGarcia,14,1oanda；TheAlphaMagneticSpectrom；1.TheAMS02detector；AMS[1](AlphaMagneticSpec；Thedetectionm
8002 naJ 92
]hp-ortsa[
1vviXraTheRingImagingCherenkovdetectoroftheAMSexperiment:testbeamresultswithaprototypeLu′?saArrudaa,?FernandoBar?aoa,Patr′?ciaGon?calvesa,RuiPereiraaaLIP/ISTAv.EliasGarcia,14,1oandarLisboa,Portugale-mail:luisa@lip.ptTheAlphaMagneticSpectrometer(AMS)tobeinstalledontheInternationalSpaceStation(ISS)willbeequippedwithaproximityRingImagingCherenkov(RICH)detectorformeasuringthevelocityandelectricchargeofthechargedcosmicparticles.ThisdetectorwillcontributetothehighlevelofredundancyrequiredforAMSaswellastotherejectionofalbedoparticles.Chargeseparationuptoironandavelocityresolutionoftheorderof0.1%forsinglychargedparticlesareexpected.ARICHprotoptypeconsistingofadetectionmatrixwith96photomultiplierunits,asegmentofaconicalmirrorandsamplesoftheradiatormaterialswasbuiltanditsperformancewasevaluated.Resultsfromthelasttestbeamperformedwithionfragmentsresultingfromthecollisionofa158GeV/c/nucleonprimarybeamofindiumions(CERNSPS)onaleadtargetarereported.Thelargeamountofcollecteddataallowedtotestandcharacterizedi?erentaerogelsamplesandthesodium?uorideradiator.Inaddition,there?ectivityofthemirrorwasevaluated.Thedataanalysiscon?rmsthedesigngoals.1.TheAMS02detectorAMS[1](AlphaMagneticSpectrometer)isaprecisionspectrometerdesignedtosearchforcos-micantimatter,darkmatterandtostudytherel-ativeabundanceofelementsandisotopiccompo-sitionoftheprimarycosmicrays.Itwillbein-stalledintheInternationalSpaceStation(ISS),whereitwilloperateatleastforthreeyears.Thespectrometerwillbecapableofmeasuringtherigidity(R≡pc/|Z|e),thecharge(Z),thevelocity(β)andtheenergy(E)ofcosmicrayswithinageometricalacceptanceof～0.5m2sr.Fig.1showsaschematicviewoftheAMSspectrometer.Thesystemiscomposedofsev-eralsubdectors:TransitionRadiationDetector(TRD),Time-of-Flight(TOF),SiliconTracker(STD),AnticoincidenceCounters(ACC),super-conductingmagnet,RingImagingCerenkovˇde-tectorandelectromagneticcalorimeter(ECAL).2Thedetectionmatrixiscomposedof680mul-tipixelizedphotonreadoutcellseachconsistingofaphotomultipliercoupledtoalightguide,HVdi-viderplusfront-end(FE)electronics,allhousedandpottedinaplasticshellandthenenclosedinamagneticshielding.ThephotondetectionismadewithanarrayofmultianodeHamamatsutubes(R)coupledtoalightguide.Thee?ectivepixelsizeis8.5mm.Ahighre?ectivityconicalmirrorsurroundsthewholeset.Itconsistsofacarbon?berre-inforcedcompositesubstratewithamultilayercoatingmadeofaluminiumandSiO2depositedontheinnersurface.Thisensuresare?ectiv-ityhigherthan85%for420nmwavelengthpho-tons.Figure2(left)showsaschematicviewoftheRICHdetector.RICHwasdesignedtomeasurethevelocity(β≡v/c)ofsinglychargedparticleswithares-olution?β/βof0.1%,toextendthechargesep-aration(Z)uptoiron(Z=26),tocontributetoe/pseparationandtoalbedorejection.InordertovalidatetheRICHdesign,apro-totypewithanarrayof9×11cells?lledwith96photomultiplierreadoutunitssimilartopartofthematrixofthe?nalmodelwasconstructed.TheperformanceofthisprototypehasbeentestedwithcosmicmuonsandwithabeamofsecondaryionsattheCERNSPSproducedbyfragmentationofaprimarybeamin2002and2003.Thelightguidesusedwereprototypeswithaslightlysmallercollectingarea(31×31mm2).Di?erentsamplesoftheradiatormaterialsweretestedandplacedatanadjustablesupportingstructure.Di?erentexpansionheightsweresetinordertohavefullycontainedphotonringsonthedetectionmatrixlikeinthe?ightdesign.Asegmentofaconicalmirrorwith1/12ofthe?nalazimuthalcoverage,whichisshowninleftpictureofFigure3,wasalsotested.TheRICHassemblyhasalreadystartedatCIEMATinSpainandisforeseentobe?nishedinJuly2007.Arectangulargridhasalreadybeenassembledandhasbeensubjecttoamechani-cal?ttest,functionaltests,vibrationtestsandvacuumtests.Theothergridswillfollow.Therefractiveindexoftheaerogeltilesisbeingmea-suredandtheradiatorcontainerwassubjectedtoamechanicaltest.The?nalintegrationofRICHinAMSwilltakeplaceatCERNin2008.Figure2.Ontheleft:ViewoftheRICHdetector.Ontheright:BerylliumeventdisplaygeneratedinaNaFradiator.3.Velocity(β)andcharge(Z)reconstruc-tionAchargedparticlecrossingadielectricmaterialofrefractiveindexn,withavelocityβ,greaterthanthespeedoflightinthatmediumemitsphotons.Theapertureangleoftheemittedpho-tonswithrespecttotheradiatingparticletrackisknownastheCerenkovˇangle,θc,anditisgivenbycosθc=1Figure3.Protypewithre?ector(left).Topviewofthetestbeam2003experimentalsetupusingCERNSPSfacility(right).Cerenkovˇpatternandniisthehitsignal.ForamorecompletedescriptionoftheTheCerenkovˇmethodsee[3].photonsproducedintheradia-torareuniformlyemittedalongtheparticlepathinsidethedielectricmedium,L,andtheirnumberperunitofenergy(N)dependsontheparticle’scharge,Z,andvelocity,β,andontherefractiveindex,n.Thereforeelectriccharge(Z)isdeter-minedfromthesignalevaluationandtakingintoaccountthedi?erentN∝Z2?L??detectione?ciencies.1?13A??4hancesastructureofwellseparatedindividualchargepeaksoverthewholerangeuptoZ=28.Thechargeresolutionforeachnuclei,showninrightpanelofFigure5,wasevaluatedthroughin-dividualGaussian?tstothereconstructedchargepeaksselectedbytheindependentmeasurementsperformedbytwoscintillatorsandsilicontrackerdetectors.Achargeresolutionforprotoneventsslightlybetterthan0.17chargeunitsisachieved.ThechargeresolutionasfunctionofthechargeZoftheparticlefollowsacurvethatcorrespondstotheerrorpropagationonZwhichcanbeex-pressedas:σ(Z)=11+σ2peN??2.(4)systThisexpressiondescribesthetwodistincttypesofuncertaintiesthata?ectZmeasurement:thesta-tisticalandthesystematic.ThestatisticaltermisindependentofthenucleichargeanddependsessentiallyontheamountofCerenkovˇsignalde-tectedforsinglychargedparticles(N0～14.7)andontheresolutionofthesinglephotoelec-tronpeak(σpe).ThesystematicuncertaintyscaleswithZ,dominatesforhigherchargesandisaround1%.Itappearsduetonon-uniformitiesattheradiatorleveloratthephotondetection.Inordertokeepthesystematicuncertaintiesbelow1%,theaerogeltilethickness,therefractiveindexandtheclarityshouldnothaveaspreadgreaterthan0.25mm,10?4and5%,atthedetectionlevelapreciseknowledge(&5%level)ofthesingleunitcellphoto-detectione?ciencyandgainsisrequired.Runswithamirrorprototypewerealsoper-formedanditsre?ectivitywasderivedfromdataanalysis.Theobtainedvalueisingoodagreementwiththemanufacturervalue.4.ConclusionsAMS-02willbeequippedwithaproximityfocusingRICHenablingvelocitymeasurementswitharesolutionofabout0.1%andextendingthechargemeasurementsuptotheironelement.Velocityreconstructionismadewithalikelihoodmethod.Chargereconstructionismadeinanevent-by-eventbasis.Evaluationofbothalgo-cerZ(scint&std)Figure5.ChargepeaksdistributionmeasuredwiththeRICHprototypeusingan=1.05aero-gelradiator,2.5cmthick.Individualpeaksareidenti?eduptoZ～28(left).ChargeresolutionversusparticleZforthesameaerogelradiator.Thecurvegivestheexpectedvalueestimatedasexplainedinthetext(right).rithmsonrealdatatakenwithin-beamtestsatCERN,inOctober2003wasdone.Thedetec-tordesignwasvalidatedandarefractiveindex1.05aerogelwaschosenfortheradiator,ful?ll-ingboththedemandforalargelightyieldandagoodvelocityresolution.TheRICHdetetectorisbeingconstructedanditsassemblingtotheAMScompletesetupisforeseenfor2008.REFERENCES1.S.P.Ahlenetal.,Nucl.Instrum.MethodsA350,34(1994).2.T.YpsilantisandJ.Seguinot,Nucl.Instrum.MethodsA343,30(1994).3.F.Bar?ao,Nucl.Instrum.MethodsA502,510(2003).4.P.Aguayo,L.Arrudaetal.,NIMA560,291(2006).包含各类专业文献、幼儿教育、小学教育、各类资格考试、中学教育、行业资料、生活休闲娱乐、文学作品欣赏、专业论文、The Ring Imaging Cherenkov detector of the AMS experiment test beam results with a prototyp85等内容。Featured Research
from universities, journals, and other organizations
DOE/Fermi National Accelerator Laboratory
A unique experiment called the Holometer has started collecting data that will answer some mind-bending questions about our universe -- including whether we live in a hologram.
Share This
A Fermilab scientist works on the laser beams at the heart of the Holometer experiment. The Holometer will use twin laser interferometers to test whether the universe is a 2-D hologram.
Credit: Fermilab
A unique experiment at the U.S. Department of Energy's Fermi National Accelerator Laboratory called the Holometer has started collecting data that will answer some mind-bending questions about our universe -- including whether we live in a hologram.
Related Articles
Much like characters on a television show would not know that their seemingly 3-D world exists only on a 2-D screen, we could be clueless that our 3-D space is just an illusion. The information about everything in our universe could actually be encoded in tiny packets in two dimensions.
Get close enough to your TV screen and you'll see pixels, small points of data that make a seamless image if you stand back. Scientists think that the universe's information may be contained in the same way and that the natural "pixel size" of space is roughly 10 trillion trillion times smaller than an atom, a distance that physicists refer to as the Planck scale.
"We want to find out whether space-time is a quantum system just like matter is," said Craig Hogan, director of Fermilab's Center for Particle Astrophysics and the developer of the holographic noise theory. "If we see something, it will completely change ideas about space we've used for thousands of years."
Quantum theory suggests that it is impossible to know both the exact location and the exact speed of subatomic particles. If space comes in 2-D bits with limited information about the precise location of objects, then space itself would fall under the same theory of uncertainty. The same way that matter continues to jiggle (as quantum waves) even when cooled to absolute zero, this digitized space should have built-in vibrations even in its lowest energy state.
Essentially, the experiment probes the limits of the universe's ability to store information. If there is a set number of bits that tell you where something is, it eventually becomes impossible to find more specific information about the location -- even in principle. The instrument testing these limits is Fermilab's Holometer, or holographic interferometer, the most sensitive device ever created to measure the quantum jitter of space itself.
Now operating at full power, the Holometer uses a pair of interferometers placed close to one another. Each one sends a one-kilowatt laser beam (the equivalent of 200,000 laser pointers) at a beam splitter and down two perpendicular 40-meter arms. The light is then reflected back to the beam splitter where the two beams recombine, creating fluctuations in brightness if there is motion. Researchers analyze these fluctuations in the returning light to see if the beam splitter is moving in a certain way -- being carried along on a jitter of space itself.
"Holographic noise" is expected to be present at all frequencies, but the scientists' challenge is not to be fooled by other sources of vibrations. The Holometer is testing a frequency so high -- millions of cycles per second -- that motions of normal matter are not likely to cause problems. Rather, the dominant background noise is more often due to radio waves emitted by nearby electronics. The Holometer experiment is designed to identify and eliminate noise from such conventional sources.
"If we find a noise we can't get rid of, we might be detecting something fundamental about nature -- a noise that is intrinsic to space-time," said Fermilab physicist Aaron Chou, lead scientist and project manager for the Holometer. "It's an exciting moment for physics. A positive result will open a whole new avenue of questioning about how space works."
The Holometer experiment, funded by the U.S. Department of Energy Office of Science and other sources, is expected to gather data over the coming year.
Story Source:
The above story is based on
provided by . Note: Materials may be edited for content and length.
Cite This Page:
DOE/Fermi National Accelerator Laboratory. "Do we live in a 2-D hologram? Experiment will test the nature of the universe." ScienceDaily. ScienceDaily, 26 August 2014. &/releases/.htm&.
DOE/Fermi National Accelerator Laboratory. (2014, August 26). Do we live in a 2-D hologram? Experiment will test the nature of the universe. ScienceDaily. Retrieved February 10, 2015 from /releases/.htm
DOE/Fermi National Accelerator Laboratory. "Do we live in a 2-D hologram? Experiment will test the nature of the universe." ScienceDaily. /releases/.htm (accessed February 10, 2015).
Share This
Related Topics
More From ScienceDaily
More Matter & Energy News
Featured Research
from universities, journals, and other organizations
Feb. 10, 2015 ? Researchers have designed a tiny cage that can trap a single strand of DNA after it has been pulled through a nanopore. While caged, biochemical experiments can be performed on the strand, which can ...
Feb. 10, 2015 ? A new multiferroric film keeps its electric and magnetic properties even when highly curved, paving the way for potential uses in wearable ...
Feb. 10, 2015 ? The master craftsmanship behind Indian swords was highlighted when scientists and conservationists from Italy and the UK joined forces to study a curved single-edged sword called a shamsheer. The ...
Feb. 10, 2015 ? Researchers have developed a method for preparing methylammonium-lead bromide hybrid nanoparticles with extraordinary luminescence. They have successfully increased the luminescence efficiency of ...
Feb. 10, 2015 ? “Antiaromatic compounds” is what chemists call a class of ring molecules which are extremely instable – the opposite of the highly stable aromatic molecules. Because they exist for mere split ...
Feb. 10, 2015 ? With a four-meter diameter primary mirror, the telescope will be able to pick up unprecedented detail on the surface of the Sun -- the equivalent of being able to examine a coin from 100 kms away. It ...
Feb. 10, 2015 ? Innovative robotic sock, which mimics tentacle movements of corals, can benefit bedridden or immobile ...
Feb. 9, 2015 ? Imagine printing out molecules that can respond to their surroundings. Chemists teamed up with engineers who are using 3-D printers to create 3-D printed objects with new capabilities. Scientists ...
Feb. 9, 2015 ? Injectable nanoparticles that could protect an injured person from further damage due to oxidative stress have proven to be astoundingly effective in tests to study their ...
Feb. 9, 2015 ? Treated carbon-60 molecules have the ability to recover valuable metals from liquids, including water and potential pollutants. In testing various metals, researchers found that charge and ionic ...
Featured Videos
from AP, Reuters, AFP, and other news services
Battery-Powered Train Brings Low-Carbon Commuting to UK
Reuters - Innovations Video Online (Feb. 10, 2015) ? The first battery-powered passenger train to run on Britain&s tracks in over 50 years completes a five-week trial in a bid to prove the viability of more eco-friendly alternatives to diesel-powered locomotives. Mia Reakes went aboard.
Video provided by Reuters
Chocolate Sniffing Sales High
Reuters - Business Video Online (Feb. 10, 2015) ? A chocolate sniffing device designed by a Belgian chocolatier has been flying off the shelves.
As Hayley Platt reports it offers customers a cocoa high without the calories.
Video provided by Reuters
Print Your Own Phone from Home
Reuters - Business Video Online (Feb. 10, 2015) ? British start-up OwnFone launches Kickstarter campaign that offers users the chance to 3D print their own cellphone - and even draw its design by hand. Jim Drury reports.
Video provided by Reuters
Boston Dynamics' New Robot Dog Can Run and Climb
Buzz60 (Feb. 10, 2015) ? Boston Dynamics is putting out a video showing off how agile its new robot is. The robot dog can tackle tough terrain and stairs. Patrick Jones (@Patrick_E_Jones) explains.
Video provided by Buzz60
Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.
Breaking News:
Related Stories
Science News
Health News
Environment News
Technology News
Save/Print:
Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:
Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:
Have Feedback?
Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Subscribe:
features breaking news and videos about the latest discoveries in health, technology, the environment, and more -- from major news services and leading universities, scientific journals, and research organizations.
Quick Links
Site Information
Read ScienceDaily's top , or browse by topic:
Read ScienceDaily's top , or browse by topic:
Read ScienceDaily's top , or browse by topic:
Read ScienceDaily's , or browse by topic:
Read ScienceDaily's top , or browse by topic:Jinan Sumspring Experiment Instruments Co., Ltd.& specializedspecialized in various testing instruments of plastic packaging, paper packaging, adhesive and medical packaging. We have professional technicians and researchers, providing excellent instruments and serv ...
Jinan Sumspring Experiment Instruments Co., Ltd, which is a joint-stock enterprise for researching and development, sale for laboratory analysis instruments,established in 2007, is focusing on providing first-class laboratory apparatus and perfect quality control soluti ...Biochemical mechanisms in the Killmann experiment: critique of the deoxyuridine suppression test.
The Journal of Clinical Investigation
Collections
Advertisement
Find articles by
Pelliniemi, T. T. in:
Find articles by
Beck, W. S. in:
Research Article
Biochemical mechanisms in the Killmann experiment: critique of the deoxyuridine suppression test.
T T Pelliniemi and
The degree of inhibition of [3H]thymidine incorporation into DNA by exogenous deoxyuridine is assayed in a procedure known as the deoxyuridine suppression test. We report studies of the biochemical basis of this phenomenon in phytohemagglutinin-stimulated lymphocytes, which suggest that its mechanism has not been fully understood. Results show that inhibition by deoxyuridine is caused only in part by expansion of the intracellular pools of nonradioactive dTMP and dTTP, which dilutes the specific radioactivity of the [3H]dTMP and [3H]dTTP derived from [3H]thymidine. Increased dTTP levels also inhibit thymidine kinase. In addition, thymidine kinase is competitively inhibited by intracellular deoxyuridine. Inhibition of thymidine kinase activity by both mebolites further decreases the specific radioactivity of [3H]dTMP and [3H]dTTP. Deoxyuridine also inhibits the incorporation of [3H]deoxyadenosine and [3H]deoxyguanosine into DNA in these cells. Exogenous deoxyuridine still inhibits [3H]thymidine incorporation in cells whose de novo thymidylate synthesis has been strongly inhibited by 5-fluorodeoxyuridine or methotrexate. In such drug-treated cells, exposure to high concentrations of exogenous deoxyuridine can partially overcome the inhibition of thymidylate synthetase with resulting increase in the severely depleted dTTP pools. This increase is associated with enhanced DNA synthesis, as measured by incorporation into DNA of labeled deoxyribonucleosides other than [3H]thymidine. We conclude that exogenous deoxyuridine has multiple effects on [3H]thymidine incorporation, which must be considered in interpretations of deoxyurindine suppression test results.
Browse pages
Click on an image below to see the page.
Advertisement
Copyright © 2015