Beam-helicity asymmetry in photon and pion electroproduction in the Delta(1232) resonance r
a r X i v :h e p -p h /0612248v 2 14 M a r 2007
EPJ manuscript No.
(will be inserted by the editor)
Beam-helicity asymmetry in photon and pion electroproduction in the ?(1232)resonance region at Q 2=0.35(GeV/c)2
I.K.Bensafa 1,P.Achenbach 2,M.Ases Antelo 2,C.Ayerbe 2,D.Baumann 2,R.B¨o hm 2,D.Bosnar 5,E.Burtin 3,X.Defa¨y 1,N.D’Hose 3,M.Ding 2,M.O.Distler 2,L.Doria 2,H.Fonvieille 1,a ,J.M.Friedrich 8,J.Friedrich 2,J.Garc′?a Llongo 2,P.Janssens 4,G.Jover Ma?n as 2,M.Kohl 2,https://www.wendangku.net/doc/503422674.html,veissi`e re 1,M.Lloyd 2,M.Makek 5,J.Marroncle 3,H.Merkel 2,P.Merle 2,U.M¨u ller 2,L.Nungesser 2,B.Pasquini 7,R.P′e rez Benito 2,J.Pochodzalla 2,M.Potokar 6,
G.Rosner 9,S.S′a nchez Majos 2,M.Seimetz 2,3,S.ˇSirca 6,T.Spitzenberg 2,G.Tamas 2,R.Van de Vyver 4,
L.Van Hoorebeke 4,Th.Walcher 2,and M.Weis 2
1Laboratoire de Physique Corpusculaire IN2P3-CNRS,Universit′e Blaise Pascal,F-63170Aubi`e re Cedex,France.2Institut f¨u r Kernphysik,Johannes Gutenberg-Universit¨a t,D-55099Mainz,Germany.3CEA Dapnia-SPhN,C.E.Saclay,F-91191Gif-sur-Yvette Cedex,France.
4Department of Subatomic and Radiation Physics,University of Gent,B-9000Gent,Belgium.5Department of Physics,University of Zagreb,HR-10002Zagreb,Croatia.6Institut Joˇz ef Stefan,University of Ljubljana,SI-1001Ljubljana,Slovenia.7Dipartimento di Fisica Nucleare e Teorica,Universit`a degli Studi di Pavia,and INFN,Sezione di Pavia,Pavia,Italy.8Physik Department,Technische Universit¨a t M¨u nchen,D-85748Garching,Germany.9
Department of Physics and Astronomy,University of Glasgow,Glasgow G128QQ,UK.
Received:date /Revised version:date
Abstract.The beam-helicity asymmetry has been measured simultaneously for the reactions →
e p →e p γand →
e p →e p π0in the ?(1232)resonance region at Q 2=0.35(GeV/c)2.The experiment was performed at MAMI with a longitudinally polarized beam and an out-of-plane detection o
f the proton.The results are compared with calculations based on Dispersion Relations for virtual Compton scatterin
g and wit
h the MAID model for pion electroproduction.There is an overall good agreement between experiment and theoretical calculations.The remaining discrepancies may be ascribed to an imperfect parametrization of some γ(?)N →πN multipoles,mainly contributing to the non-resonant background.The beam-helicity asymmetry in both channels (γand π0)shows a good sensitivity to these multipoles and should allow future improvement in their parametrization.
PACS.13.40.-f Electromagnetic processes and properties –13.60.Fz Elastic and Compton scattering –13.60.Le Meson production –14.20.Gk Baryon resonances with S=0
1Introduction
Polarization observables are powerful tools to study hadron structure.They have seen intensive developments in the recent years in semi-inclusive and exclusive reactions,at high and low energies.At high energies they are detailed probes of mechanisms at the parton level,e.g.in the study of the transverse spin structure of the nucleon in semi-inclusive deep inelastic scattering [1],or of the general-ized parton distributions in exclusive deep virtual Comp-ton scattering (DVCS)[2].At lower energies,models of nucleon structure have to address the non-perturbative regime of QCD without the help of hard sub-mechanisms.The relevant degrees of freedom can be quarks,like in con-stituent quark models,or bare hadrons surrounded by a
2I.K.Bensafa et al.:Beam-helicity asymmetry in photon and pion electroproduction... ergy of the outgoing photon
[5].These observables have
been measured recently at di?erent values of the four-
momentum transfer squared Q2at MAMI[6],JLab[7]
and MIT-Bates[8].
When going above the pion threshold,the VCS ampli-
tude T V CS acquires an imaginary part due to the coupling
to theπN channel.Therefore single polarization observ-
ables,which are proportional to I m(T V CS),become non-
zero above pion threshold.A particularly relevant observ-
able is the single-spin asymmetry(SSA)or beam-helicity
asymmetry:SSA=(σ↑?σ↓)/(σ↑+σ↓)whereσ↑andσ↓
designate the photon electroproduction cross section with
beam helicity state+and?,respectively.As it was?rst
pointed out in ref.[9],the SSA yields direct information
on the absorptive part of the VCS amplitude,and on the
relative phase between the VCS amplitude and the Bethe-
Heitler(BH)contribution.The BH process refers to the
photon emission by the incoming or outgoing electron and
it adds coherently to the VCS amplitude.Moreover,the
VCS amplitude can be split into a Born part,given in
terms of nucleon ground state properties(the electromag-
netic form factors),and a non-Born part which contains all
nucleon excitations and meson-loop contributions.Since
the BH and Born-VCS contributions are purely real,the
SSA is proportional to the imaginary part of the non-Born
VCS amplitude.In particular,the numerator of the SSA
can be written as I m(T V CS)·R e(T V CS+T BH).After
development,one obtains the sum of a pure VCS contri-
bution and a VCS-BH interference term which has the
e?ect to enhance the asymmetry.The absorptive part of
the VCS amplitude can be obtained,through unitarity re-
lation,from the photo-and electro-production amplitudes
on the nucleon.In the region of W～1.2GeV,the most
important contribution is fromπN intermediate states,
as schematically depicted in?g.1,while mechanisms in-
volving more pions or heavier mesons in the intermediate
states are suppressed.Regarding the Q2-dependence,the
pion photoproduction description is on solid experimental
grounds,while electroproduction data are scarce.There-
fore a measurement of the beam SSA in the?-resonance
region gives a direct test of how well the description of
the VCS amplitude holds,in terms of the available phe-
nomenological information on pion photo-and electro-
production amplitudes.This is the main purpose of the
experiment described in the present paper.
In the case of DVCS one has a knownφ-dependence of
the numerator and denominator of the SSA.In our kine-
matic regime this dependence is not known analytically.
However,the Dispersion Relations(DR)model calcula-
tion discussed in section4gives a shape of the asymmetry
close to a sinφ,despite the distortion of the numerator
and denominator due to the BH process.
Since in the experiment the reaction ep→epπ0was de-
tected too,the beam SSA was also measured in this chan-
nel,complementing previous measurements of this type
at di?erent kinematics[3,10].In pion electroproduction,
the beam SSA,also calledρ′LT,is proportional to the?fth
structure function R′LT[11]and is mainly sensitive to the
Im ...
multipole ratios S1+/M1+and S0+/M1+in the region of
the?resonance.
2The experiment
The experiment was performed at the Mainz Microtron
MAMI using the100%duty cycle electron beam at an
energy of883.2MeV,allowing for a longitudinal beam po-
larization P e of75-85%.Helicity reversal was performed
every second,and beam current values were typically13-
25μA.The experiment used the standard equipment of
the A1collaboration[12]:the M?ller polarimeter to mea-
sure P e once a day,the5cm long liquid Hydrogen target,
spectrometer A to detect the scattered electron at a?xed
setting,and spectrometer B to detect the?nal proton at
three di?erent out-of-plane settings.Table1summarizes
the kinematical settings,corresponding to an average Q2
of0.35(GeV/c)2and a virtual photon momentum in the
center-of-mass q cm=600MeV/c,similar to a previous
VCS experiment at MAMI[6].However,here W is above
pion threshold(W～1.2GeV)and the virtual photon po-
larization?=0.48is the highest achievable at this value
of W.
The detector package in each spectrometer includes a
set of two double-planes of vertical drift chambers(VDC)
for particle tracking and two segmented planes of scintil-
lators for particle identi?cation and timing measurements.
The experiment also uses the threshold gasˇCerenkov coun-
ter in spectrometer A for electron identi?cation.The beam
was o?-centered horizontally in order to minimize the path-
length in Hydrogen for the low-energy emitted protons.
Analysis cuts include particle identi?cation for the?nal
electron and proton,good quality tracks in the VDCs,and
rejection of backscattered protons at the entrance window
of spectrometer B.A speci?c cut is applied to eliminate
protons emitted at the most upward angles,which hit
a piece of the target holding system.Empty target cell
studies showed that the rate of background events from
I.K.Bensafa et al.:Beam-helicity asymmetry in photon and pion electroproduction (3)
C o u n t s
5000
10000
15000
T (ns)AB
Fig.2.The coincidence time spectrum for a sample of the data (no cuts).Inserts:zoom on the central peak after analysis cuts,for the full statistics in both channels:γ(left)and π0(right)electroproduction.
eA →epX reactions in the target walls was negligible compared to the rate of ep →epπ0events,but not negli-gible compared to the rate of ep →epγevents.Therefore a cut on the target length is applied in the analysis of the γchannel,but not in the π0channel.
Fig.
2shows the spectrum of coincidence time (T AB )for triggers in coincidence between the two spectrometers.The central peak represents the true (e,p )coincidences and has a FWHM of 1ns.Without any cuts,one notices a secondary peak near T AB =?2ns due to true (π?,p )
coincidences,which is eliminated by a cut on the ˇCerenkov
counter signal in spectrometer A.After all cuts,the level of random coincidences is still high for the γchannel,as il-lustrated by the insert on ?g.2.Events are selected within ±1.4ns in the central peak,and random coincidences are subtracted using side-band events.
The four-momentum of the third,undetected particle is reconstructed by the missing energy and missing mo-mentum associated to the detected (ep )system.Fig.3shows the ?nal spectrum of the missing mass squared (M 2x ).The most prominent peak is due to π0electropro-duction events.The second peak,centered on M 2
x
=0,is due to photon electroproduction events,and its smallness re?ects the smallness of the corresponding cross section.This spectrum is obtained after a careful calibration of ex-perimental parameters,such as the beam position along the horizontal transverse axis,a casual layer of frost on the target walls,and the central momentum of spectrom-eter B for each run period,which was changed by less than a few 10?3w.r.t.its nominal value.The separation
between the two peaks in M 2
x is well-achieved.Both peaks are similar in shape:they have the same central width due to experimental resolution,and a radiative tail extending to larger values.An empirical ?t of this shape (see curves on ?g.3)allows to quantitatively estimate the residual π0events under the photon peak,yielding a contamination C =4%.All other background processes,https://www.wendangku.net/doc/503422674.html,ing
C o u n t s
10000
20000
5001000
M x 2 (GeV 2
)
Fig.3.Top:the missing mass squared spectrum within analy-sis cuts and after subtraction of random coincidences.Bottom:the same histogram truncated in ordinate to enhance the pho-ton peak,plus a ?t function drawn for each peak (solid lines)and the sum (dashed line).
from the target walls,are reduced to a negligible level within the analysis cuts.Finally,the two physics channels
are selected by the following cuts in M 2
x :[?0.005,0.005]
GeV 2
for the ep →epγprocess and [0.013,0.029]GeV 2for the ep →epπ0process.The achieved statistics are then 38k true γevents and 1M true π0events.More details on the analysis can be found in refs.[13,14].
3Analysis method and results
Fig.4shows the angular phase space coverage for photon
electroproduction events:θcm
γ?γis the polar angle between the initial and ?nal photons of the Compton scattering process and φis the azimuthal angle between the leptonic and hadronic planes as illustrated on ?gure 5.The value of φ=+90?corresponds to the missing particle emitted along the direction of k ×k ′,where k and k ′are the mo-menta of the incoming and scattered electrons.The three settings cover altogether the region of forward polar an-gles up to 40?,and a domain in φnarrowing around 220?
as θcm γ?γincreases.According to model calculations,the asymmetry is maximal at forward polar angles for VCS,whereas it is maximal at backward angles for π0electro-production.The region of forward angles was chosen,since the experiment was optimized for VCS.
Since the SSA is a relative quantity,the data do not need to be corrected for detector ine?ciencies,deadtimes,etc.Only false asymmetries were checked,and found to be very small:the beam charge asymmetry (for which the data are corrected)is of the order of 10?3.The phase
space is binned in θcm
γ?γ(4
?wide,large compared to the
4I.K.Bensafa et al.:Beam-helicity asymmetry in photon and pion electroproduction ...
Θ (deg)φ (d e g )
γ*γ
cm
Fig.4.The accepted phase space in terms of the polar and
azimuthal angles of the Compton scattering process.
Fig.5.Kinematics of the ep →epγreaction in the γp center-of-mass.
experimental resolution)and in each θ-bin the SSA is de-termined as one value,corresponding to one central kine-matical point.To this end the asymmetry is ?tted to the assumption SSA =K ·sin φ(cf.section 1)and the fac-tor K is determined by a maximum likelihood method.The probability associated to event i is proportional to (1+h i P e K sin φi )where h i is the beam helicity state (+1or ?1)and φi the azimuthal angle of the event.The like-lihood method includes the treatment of random coinci-dences and also yields the statistical error on K .As a cross-check,a more classical method is used,based on the count rates N +and N ?:the asymmetry A =(N +?N ?)/(N ++N ?)/P e is calculated in ?nite bins in φand then ?tted to the same shape A =K ·sin φ.
The ?nal asymmetry is computed as K ·sin 220?,i.e.it is projected to φ=220?,a value close to the average over the acceptance.Since the central kinematics vary slightly from bin to bin,one makes a projection to a ?xed,nominal kinematics in (Q 2,W,?):
SSA exp nom.kin.
=
SSA exp exp.kin.
×
SSA model nom.kin.
2)π0contamin.(γ)
?C =±2%(C =4%)
4)proj.to nom.kin.
proj.factor varied by ±10%
6)stability within cuts
cuts in T AB ,acceptance,M 2
x etc.
I.K.Bensafa et al.:Beam-helicity asymmetry in photon and pion electroproduction (5)
Table3.Beam SSA result for the two reactions,at nominal
kinematics:Q2=0.35(GeV/c)2,W=1.19GeV,?=0.48,φ=
220?.
→e p→e pγchannel
2.6-0.0210.0260.015
6.0-0.0350.0170.006
9.8-0.0320.0200.011
14.0-0.0260.0300.016
17.9-0.0140.0340.020
21.9-0.1210.0440.021
26.1-0.0500.0460.023
29.9-0.0530.0500.034
33.7-0.0040.0700.047
→e p→e pπ0channel
2.50.00160.00350.0017
5.9-0.00070.00280.0011
9.9-0.00590.00330.0024
14.0-0.00640.00400.0018
17.9-0.00770.00430.0021
22.1-0.00550.00530.0031
26.2-0.00330.00430.0022
30.0-0.00320.00390.0016
33.7-0.00780.00490.0014
37.4-0.02050.00900.0039
6I.K.Bensafa et al.:Beam-helicity asymmetry in photon and pion electroproduction ...
Θ (deg)
S S A
cm γ*π
Fig.8.The beam SSA in π0electroproduction at nominal kinematics,compared to theoretical calculations.Same con-vention as ?gure 6for the error bars.
ular,?gure 7shows that the calculation with this re-?t gives a lower asymmetry,in better agreement with the trend of the data at increasing angles.Nevertheless,since this MAID re-?t [4]was performed at kinematics di?erent from the present experiment,there is room left for further πN multipole adjustment.Other possibilities like contri-butions beyond πN are very unlikely,since our measured range in W is mostly below the two-pion threshold.
4.2Pion electroproduction channel
The result of the measurement of →
e p →epπ0is displayed
on ?g.8.At small angles up to θcm γ?π=20?
,the data are in very good agreement with the MAID model [16](ver-sions “2000”and “2003”)and the DMT model [22].Also shown is the MAID re-?t [4]mentioned above,in which the longitudinal multipoles S 1+and S 0+have been adjusted essentially at Q 2=0.2(GeV/c)2.Applied to our Q 2of 0.35(GeV/c)2[23],this version yields a much lower asymme-try than the other predictions,and not in better agree-ment with our measurement.It was already suggested in [10]that a simple rescaling of the S 1+and S 0+multipoles cannot account for the Q 2-dependence of the data.
Beyond 20?the data of ?g.8tend to suggest some structure which no model can reproduce.In the s and p wave M 1+-dominance approximation,the ?fth structure
function R ′LT is proportional to sin θcm γ?π·I m {(6cos θcm
γ?πS 1++S 0+)?M 1+}[11].To describe the rapid θ-variations that we observe for the SSA is quite challenging;it requires the contribution from higher-order multipoles which produce a non-resonant background modulating the resonant M 1+contribution,as already noticed in ref.[10].
5Conclusion
The beam-helicity asymmetry has been measured simulta-neously for photon and π0electroproduction in the ?(1232)resonance region.The measured asymmetries are of the order of a few percent for γand smaller than 1%for π0.There is an overall good agreement between our measure-ment and the theoretical calculations,based on the DR and MAID models.The remaining discrepancies in shape or magnitude of the asymmetry might be ascribed to an imperfect parametrization of some πN multipoles,mainly contributing to the non-resonant background.
Concerning virtual Compton scattering,which was the main goal of the experiment,we have performed the ?rst measurement of the beam SSA in photon electroproduc-tion at low energies.The latter provides an important cross-check for the input to the DR formalism for VCS since the imaginary part of the VCS amplitude is con-nected through unitarity to the γ(?)N →πN multipoles.In order to improve the agreement between experiment and theory for the beam SSA in the photon and electro-production channels,one could attempt a simultaneous ?t of the two observables,by changing the parametrization of some π0electroproduction multipoles.In that view,the observables in the two physics channels become coupled.Therefore the data presented in this paper address in a new way important questions by showing how the simul-taneous measurements in several de-excitation channels (γN and πN )can help to gain new insights for our un-derstanding of the nucleon and resonance phenomena at low energy.
We thank the MAMI accelerator sta?for providing the excellent polarized beam.We thank L.Tiator for valu-able discussions and for providing his MAID re-?t result,and M.Vanderhaeghen and G.Smirnov for their contribu-tion to the calculation of radiative corrections.This work was supported by the Deutsche Forschungsgemeinschaft (SFB 443),the Federal State of Rhineland-Palatinate,the French CEA and CNRS/IN2P3,the BOF-Gent University and FWO-Flanders (Belgium)and the EPSRC,UK.
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一级注册建筑师之建筑物理与建筑设备知识汇总
采光窗种类、特性及使用范围 二、采光窗种类、特性及使用范围 (一)侧窗：侧窗构造简单，布置方便，造价低，光线的方向性好，有利于形成阴影，适于观看立体感强的物体，并可通过窗看到室外景观，扩大视野，在大量的民用建筑和工业建筑中得到广泛的应用。侧窗的主要缺点是照度分布不均匀，近窗处照度高，往里走，水平照度下降速度很快，到内墙处，照度很低，离内墙lm处照度最低。侧窗采光房间进深不要超过窗口上沿高度的2倍，否则需要人工照明补充。 侧窗分单侧窗、双侧窗和高侧窗三种，高侧窗主要用于仓库和博览建筑。 (二)天窗：随着建筑物室内面积的增大，只用侧窗不能达到采光要求，需要设计天窗。天窗分为以下几种类型： 1.矩形天窗：这种天窗的突出特点是采光比侧窗均匀，即工作面照度比较均匀，天窗位置较高，不易形成眩光，在大量的工业建筑，如需要通风的热加工车间和机加工车间应用普遍。为了避免直射阳光射入室内，天窗的玻璃最好朝向南北，这样阳光射人的时间少，也易于遮挡。天窗宽度一般为跨度的一半左右，天窗下沿至工作面的高度为跨度的0.35-0.7倍。 2.横向天窗(横向矩形天窗)：这种天窗比避风天窗采光系数高，均匀性好，省去天窗架，造价低，能降低建筑高度。设计时，车间长轴应为南北向，即天窗玻璃朝向南北。 3.锯齿形天窗：这种天窗有倾斜的顶棚作反射面，增加了反射光分量，采光效率比矩形天窗高，窗口一般朝北，以防止直射阳光进入室内，而不影响室内温度和湿度的调节，光线均匀，方向性强，在纺织厂大量使用这种天窗，轻工业厂房、超级市场、体育馆也常采用这种天窗。 4.平天窗：这种天窗的特点是采光效率高，是矩形天窗的2-3倍。从照度和亮度之间的关系式召E=L.Ω.cosa看出，对计算点处于相同位置的矩形天窗和平天窗，如果面积相等，平天窗对计算点形成的立体角大，所以其照度值就高。另外乎天窗采光均匀性好，布置灵活，不需要天窗架，能降低建筑高度，在大面积车间和中庭常使用平天窗。设计时应注意采取防止污染、防直射阳光影响和防止结露措施。 5.井式天窗：采光系数较小，这种窗主要用于通风兼采光，适用于热处理车间。 设计时，可用以上某一种采光窗，也可同时使用几种窗，即混合采光方式。 天然采光基本知识 二、采光窗种类、特性及使用范围 (一)侧窗：侧窗构造简单，布置方便，造价低，光线的方向性好，有利于形成阴影，适于观看立体感强的物体，并可通过窗看到室外景观，扩大视野，在大量的民用建筑和工业建筑中得到广泛的应用。侧窗的主要缺点是照度分布不均匀，近窗处照度高，往里走，水平照度下降速度很快，到内墙处，照度很低，离内墙lm处照度最低。侧窗采光房间进深不要超过窗
非制冷红外技术及应用
非制冷红外技术及应用 蓝海光学招募：镜头装配主管，镜头销售人员光学人生，你的精彩人生！一、红外热成像技术简介自然界所有温度在绝对零度（-273℃）以上的物体都会发出红外辐射，红外图像传感器则将探测到的红外辐射转变为人眼可见的图像信息。红外成像技术涵盖了红外光学、材料科学、电子学、机械工程技术、集成电路技术、图像处理算法等诸多技术，红外成像装置的核心为红外焦平面探测器。 二、非制冷红外技术概述2.1 非制冷红外技术原理非制冷红外探测器利用红外辐射的热效应，由红外吸收材料将红外辐射能转换成热能，引起敏感元件温度上升。敏感元件的某个物理参数随之发生变化，再通过所设计的某种转换机制转换为电信号或可见光信号，以实现对物体的探测。 非制冷红外焦平面探测器分类2.2 非制冷红外探测器的关 键技术 热释电型红外辐射使材料温度改变，引起材料的自发极化强度变化，在垂直于自发极化方向的两个晶面出现感应电荷。通过测量感应电荷量或电压的大小来探测辐射的强弱。热释电红外探测器与其他探测器不同，它只有在温度升降的过程中才有信号输出，所以利用热释电探测器时红外辐射必须经过调制。探测材料：硫酸三甘肽、钽酸锂、钽铌酸钾、钛（铁
电）酸铅、钛酸锶铅、钽钪酸铅、钛酸钡热电堆由逸出功不同的两种导体材料所组成的闭合回路，当两接触点处的温度不同时，由于温度梯度使得材料内部的载流子向温度低的一端移动，在温度低的一端形成电荷积累，回路中就会产生热电势。（塞贝克效应Seebeck）而这种结构称之为热电偶。一系列的热电偶串联称为热电堆。因而，可以通过测量热电堆两端的电压变化，探测红外辐射的强弱。二极管型利用半导体PN结具有良好的温度特性。与其他类型的非制冷红外探测器不同，这种红外探测器的温度探测单元为单晶或多晶PN结，与CMOS工艺完全兼容，易于单片集成，非常适合大批量生产。热敏电阻型（微测辐射热计）利用热敏电阻的阻值随温度变化来探测辐射的强弱。一般探测器采用悬臂梁结构，光敏元吸收红外热辐射，由读出电路测量热敏材料电阻变化而引起的电流变化，通过读出电路对电信号采集分析并读出。探测器一般采用真空封装以保证绝热性好。探测材料：氧化钒、非晶硅、钛、钇钡铜氧等氧化钒VOx的TCR 一般为2%~3%，特殊方法制备的单晶态VO2和V2O5可达4%。VOx具有电阻温度系数大，噪声小的特点，被广泛用作非制冷式红外焦平面传感器的热敏材料。全球的非制冷红外热像仪市场中，使用VOx非制冷红外探测器的占80%以上。氧化钒VOx的制备方法：溅射法、溶胶-凝胶法、脉冲激光沉积法、蒸发法。读出电路IC技术ROIC对微弱的红
中远红外探测器发展动态
中远红外探测器发展动态 1 红外光电探测器的的历史 红外探测成像具有作用距离远、抗干扰性好、穿透烟尘雾霾能力强、可全天候、全天时工作等优点在军用和民用领域都得到了极为广泛的应用按照探测过程的物理机理，红外探测器可分为两类即热探测器和光电探测器。光电探测器的工作原理是目标红外辐射的光子流与探测器材料相互作用，并在灵敏区域产生内光电效应。因具有灵敏度高、响应速度快的优点，光电探测器在预警、精确制导、火控和侦察等红外探测系统中得到广泛应用。 红外焦平面阵列可探测目标的红外辐射，通过光电转换、电信号处理等手段，可将目标物体的温度分布图像转换成视频图像，是集光、机、电等尖端技术于一体的红外光电探测器H。目前许多国家，尤其是美国等西方军事发达国家，都花费大量的人力、物力和财力进行此方面的研究与开发，并获得了成功。红外光电探测器研究从第一代开始至今已有40余年历史，按照其特点可分为三代。第一代(1970s～1980s)主要是以单元、多元器件进行光机串／并扫描成像，以及以4×288为代表的时间延迟积分(TDI，time delay integration)类扫描型(scanning)红外焦平面列阵。单元、多元探测器扫描成像需要复杂笨重的二维、一维扫描系统结构，且灵敏度低。第二代红外光电探测器是小、中规格的凝视型(staring)红外焦平面列阵。M×N凝视型红外焦平面探测元数从1元、N元变成M×N元，灵敏度也分别从l与N1/2增长M×N1/2倍和M1/2。而且，大规模凝视焦平面阵列，不再需要光机扫描，大大简化整机系统。 目前，正在发展第三代红外光电探测器。探测器具有大面阵、小型化、低成本、双色(two-color)与多色(multi-color)、智能型系统级灵巧芯片等特点，并集成有高性能数字信号处理功能，可实现单片多波段融合高分辨率探测与识别。因此，本文将重点综述三代红外光电探测器的材料体系及其研究现状，并分析未来红外光电探测器的材料选择及发展趋势。 2 三代探测器的材料体系与发展现状 红外光电探测器的材料很多，但真正适于发展三代红外光电探测器，即响应波段灵活可调的双色与多色红外焦平面列阵器件的材料则很少。目前，主要有传统的HgCdTe和QWIPs，以及新型的二类SLs和QDIPs，共四个材料体系。作为
制冷型探测器在不同大气条件下红外搜索系统作用距离计算问题
制冷型探测器在不同大气条件下红外搜索系统作用距离计算问题 已知条件： 1、制冷型探测器：3~5μ 30μ（像元） 像素：320×240 2、3~5μm 波段在海面情况下（分别针对喷气式飞机和舰艇）传输透过率分析。（晴朗和浓雾） 3、能量计算（探测距离） （1）海面对空 20km ，喷气式飞机，翼展30m （2）海面 20km ，舰艇 （3）相对孔径、透过率 4、非制冷型红外探测器光学系统参数：f′=30~180；F ：2.1；透过率：τ〉70% 求晴朗和浓雾大气条件下红外搜索系统作用距离。 解： 搜索系统的作用距离方程为： 21 2 1 *0])(4[n s f F DD I S υυωσττπα? ?= 其中：i I ： 红外辐射强度 ατ： 大气透过率 0τ： 光学系统透过率 D ： 通光口径 *D ： 探测率 σ： 信号过程因子 F ： 光圈数 ω： 视场角 f ?： 系统带宽 n s u u ：信噪比 对于制冷型波段在3-5μm, 30u (像元) 分辨率为320?240 'f =180mm=18cm F=2.1 晴朗时T=25C ? RH=90% 1) 通过查阅《红外技术》知在3-5μm 波段范围内，飞机的辐射强度 53-I =483.49sr w 2) 大气透过率为大气中水蒸气透过率与大气中CO 2中透过率的乘积即 2 2 CO O H τττα?= 相对湿度为空气中试样水蒸气含量与饱和时水蒸气含量比值
即S RH ρρω = 经查表知25C ?饱和水蒸气的质量为S ρ=22.80 3 m g 则356.42080.22m g RH s w =???=?=ρρ 又因为高度为h 的水平距离X 所具有的透射比等于长度为0X 的等效海平面上透射比即 k P P X X ??? ? ???=0 0 其中P ：高度为h 处的大气压强 P 0：平面上的大气压强 k ：常数 对H 2O 系统k=0.5，对CO 2系统k=1.5 。 又因为根据已知有h=10km d=20km ∴水平距离X=22h d -=221020-=103km 经查表得 当h=10km 时 对于H 2O 系统：k ???? ??0ρρ=0.518 对于CO 2系统：k ??? ? ??0ρρ=0.141 根据以上数据可求得对于水蒸气全路程可凝结水的毫米数为 K O H W W X X O H 220 0W ???? ????=?=ρ ρ ρρ = 4.56?17.32?0.518 = 40.911mm 经查表可得在3-5μm 范围内，可凝结水毫米数为40.911mm 的透过率对所有数值进行加和取平均 ()2 3.0 5.0 3.1 3.2 4.9( /202 2 H O τττ τττ=+++????++ 晴朗） =0.001+0.029+0.084+0.233+0.509+0.768+0.883+0.922+0.961+0.961+0.940+0.92 2+0.883+0.824+0.623+0.465+0.334+0.233+0.172+0.0375）/20 = 0.539 对于CO 2的等效海平面的水平距离为 km X X K CO CO 442.2141.072.132 2 =?=???? ???=ρ ρ 经查表可得在3-5μm 范围内,海平面水平距离为2CO X 的CO 2的透射率的平均值为：
红外光电探测器技术的发展(学术前沿专题)
量子点红外光电探测器技术的发展 （学术前沿专题） 专业：测试计量技术及仪器 班级：硕研22班 学生学号： S0908******* 学生姓名：李刚
量子点红外光电探测器 目前大多数红外焦平面阵列（FPA）都以量子阱红外光电探测器（QWIP）或碲镉汞（MCT）光电探测器为基础，而这两类探测器都存有重大的不足。 QWIP对垂直入射光的探测效率很低，因为垂直方向上光子的跃迁被禁止。尽管利用光栅可以弥补这一缺点，但光栅的制作无疑会增加系统的成本。另外，QWIP在高温工作时暗电流较高，所以通常采用冷却方式使其在低温下工作，这便大大增加了成像系统的成本、体积和功耗。 MCT光电探测器则因为MCT固有的不稳定性，很难实现高度均匀的探测器阵列，而且以MCT为基础的FPA还具有成本高和效率低的缺点。 近年来，量子点红外光电探测器（QDIP）在工作温度和量子效率方面取得的重大进步，将有望引领新一轮成像技术热潮，并将在医学与生物学成像、环境与化学监测、夜视与太空红外成像等领域开辟新的应用天地。目前，通过采用纳米技术形成量子点，研究人员已经在开发室温或接近室温工作的高性能成像器方面迈出了一大步。 量子点又称“人造原子”，目前量子点作为提高电子与光电子器件性能的一种手段，已经被广泛应用。量子点的尺寸很小，通常只有10nm，因此其具有独特的三维光学限制特性。将量子点应用在红外光电探测器上，可以使探测器在更高的温度下工作。 开发高温工作的红外光电探测器，可以降低红外成像系统的成本，减小重量，提高效率，这将极大地拓展红外光电探测器的应用范围。研究人员已经开发出了首个以QDIP为基础的焦平面阵列。
国际光学与光子学会SPIE简介
国际光学与光子学会SPIE简介 SPIE成立于1955年，致力于推动以光为基础的技术，服务了超过170个国家。SPIE 每年组织或赞助近25个大型技术论坛、展览以及培训项目，范围遍及北美、欧洲、亚洲及澳洲。 1957年，出版了第一期SPIE报刊，举办了第一届国家技术研讨会。 1960年，SPIE报刊刊登了第一组技术论文。 1963年，SPIE举办了第一届研讨班形式的会议并出版了第一批会议记录。 1973年，总部从Redondo Beach迁往加州的Palos V erdes。 1975年，协会收入达到50万美元，实现了财政自给。 1977年，成立了协会金牌奖。总部迁往华盛顿Bellingham。 1995年，举办了成立40周年庆典。合作赞助了在西安举办的国际传感器应用与电子器件展览会。 2000年，SPIE会员Zhores I. Alferov因在半导体异质结构和高速光电子学方面的贡献获得诺物理学奖。 2003年，SPIE数字图书馆启动，提供了期刊和会议纪要的七万篇文献。 现在的光学和光电子学大都围绕信息光学展开研究。在集成光信息处理方面，有光计算、光学互连、衍射光学等前沿领域；在成像方面，较热门的技术有光学计算机断层成像和三维共焦成像系统；在光学传感器方面，人们越来越关注三维传感技术；新一代的全息术和光学信息处理技术也亟待开发。同时，信息光学的材料和装置也成为了热门领域。更加偏向应用领域的还有人机接口与显示技术。当然还有很多基础理论问题，如非线性光学、超快光学现象、散射、位相共轭等。 Statement of Purpose SPIE is an international society advancing an interdisciplinary approach to the science and application of light. About the Society SPIE is the international society for optics and photonics founded in 1955 to advance light-based technologies. Serving approximately 180,000 constituents from more than 170 countries, the Society advances emerging technologies through interdisciplinary information exchange, continuing education, publications, patent precedent, and career and professional growth. SPIE annually organizes and sponsors approximately 25 major technical forums, exhibitions, and education programs in North America, Europe, Asia, and the South Pacific. In 2010, the Society provided more than $2.3 million in support of scholarships, grants, and other education programs around the world.
光电探测器 入门详细解析
光电探测器 摘要 本文研究了近期崛起的高科技新秀：光电探测器。本文从光电探测器的分类、原理、主要参数、典型产品与应用、前景市场等方面简单介绍了光电探测器，使大家对光电探测器有一个初步的理解。了解光电探测材料的原理不仅有利于选择正确适宜的光电探测材料，而且对研发新的光电探测器有所帮助 一、简单介绍引入 光电探测器是指一类当有辐射照射在表面时，性质会发生各种变化的材料。光电探测器能把辐射信号转换为电信号。辐射信号所携带的信息有：光强分布、温度分布、光谱能量分布、辐射通量等，其进过电子线路处理后可供分析、记录、储存和显示，从而进行探测。 光电探测器的发展历史： 1826年，热电偶探测器→1880，金属薄膜测辐射计→1946，热敏电阻→20世纪50年代，热释电探测器→20世纪60年代，三元合金光探测器→20世纪70年代，光子牵引探测器→20世纪80年代，量子阱探测器→近年来，阵列光电探测器、电荷耦合器件（CCD） 这个被誉为“现代火眼金睛”的光电探测材料无论在经济、生活还是军事方面，都有着不可或缺的作用。 二、光电探测材料的分类。 由于器件对辐射响应的方式不一样，以此可将光电探测器分为两大类，分别是光 1
子探测器和热探测器。 ○1光子探测器：光子，是光的最小能量量子。单光子探测技术，是近些年刚刚起步的一种新式光电探测技术，其原理是利用新式光电效应，可对入射的单个光子进行计数，以实现对极微弱目标信号的探测。光子计数也就是光电子计数，是微弱光（低于10－14W）信号探测中的一种新技术。 ○2利用光热效应制作的元件叫做热探测器，同时也叫热电探测器。（光热效应指的是当材料受光照射后，光子能量会同晶格相互作用，振动变得剧烈，温度逐渐升高，由于温度的变化，而逐渐造成物质的电学特性变化）。 若将光电探测器按其他种类分类，则 按应用分类：金属探测器，非成像探测器（多为四成像探测器），成像探测器（摄像管等）。 按波段分类：红外光探测器（硫化铅光电探测器），可见光探测器（硫化镉、硒化镉光敏电阻），紫外光探测器。 2
光子学基础
摘要：本文介绍了光纤传感器与传统传感器的优点及传光、传感型光纤传感器的原理。之后 讲述了光纤传感器的分类及其特点，最后重点讲述了光纤传感器的应用，主要有在结构工程 检测方面、在桥梁检测方面、在岩土力学与工程方面、在食品工业中、军事技术。 关键字：光纤传感器原理军工应用工程检测 Abstract: This paper mainly introduces the advantages of the optical fiber sensor and the traditional sensor as well as the principles of the optical fiber sensor, including the type of light and the type of sensor. Besides, it describes the classification and features of the optical fiber sensor. At last, the paper focuses on the application of the optical fiber sensor, mainly in the aspects of structural engineering detection, bridge detection, rock-soil mechanics and engineering, food industry and military technology. Keywords: the optical fiber sensor; principle; military application; engineering detection 1.引言 光纤传感技术的发展始于20世纪70年代，是光电技术发展最活跃的分支之一[1]。近年来传感器产品收益日益增大，传感技术已成为衡量一个国家科学技术的重要标志。光纤传感器与传统的各类传感器相比，可用光作为敏感信息的载体，用光纤作为传递敏感信息的媒质，具有光纤及光学测量的特点，电绝缘性能好，抗电磁干扰能力强，非侵入性，高灵敏度，容易实现对被测信号的远距离监控，耐腐蚀，防爆，光路有可挠曲性，便于与计算机联接。因此光纤传感技术发展迅速，种类多样，被测物里量达70多种。基于相位调制的高精度、大动态光纤传感器也越来越受到重视，光纤光栅、多路复用技术、阵列复用技术使光纤传感器的应用范围和规模大幅度提高，分布式光纤传感器和智能结构更是当今的研究热点[2]。 2.原理 光纤传感器主要由光源、光纤、敏感元件、光电探测器和信号处理系统等部分组成，如图 1 所示[3]。由光源发出的光经光纤引导至敏感元件，光的某一性质在这里受到被测量调制，已调光经接收光纤耦合到光电探测器，使光信号变为电信号，最后经信号处理系统处理得到被测量。
量子线红外光子探测器的研究进展
收稿日期:2008-09-24 作者简介:王忆锋(1963-),男,湖南零陵人,高级工程师.曾在美国内布拉斯加大学林肯分校计算机系做国家公派访问学者.目前主要从事器件仿真研究. 文章编号:1673-1255(2008)06-0031-05 量子线红外光子探测器的研究进展 王忆锋 (昆明物理研究所,云南 昆明 650223) 摘 要:基于半导体量子线子能带间跃迁的量子线红外光子探测器(Q RI P )由于其独特的电子性质,具有工作温度较高、信噪比较高、暗电流较低、光谱范围较宽以及垂直入射光响应等特点.对于新型红外探测器的研发而言,Q RI P 是颇具潜力的候选者之一.通过对近年来部分相关文献的分析介绍,总结和评述了Q RI P 制备工艺、物理性质、仿真方法等方面的研究进展.关键词:量子线;量子线红外光子探测器;光子探测器;红外探测器中图分类号:O471.1 文献标识码:A R ecent Developments of Q uantum Wire Infrared Photodetectors WAN G Y i 2feng (Kunming Institute of Physics ,Kunming 650223,China ) Abstract :The quantum wire infrared photodetectors (QRIP )are based on intersubband transitions in semicon 2ductor quantum wires and have the potential for higher operational temperature ,increased signal 2to 2noise ratio ,reduced dark current ,wider spectral range and sensitivity to normal incident radiation due to their unique elec 2tronic properties.It is one of the potential candidates for the developments of new infrared detectors.The devel 2opments of QRIP in the fabrication process ,physical features and simulation methods are summarized and re 2viewed according to the published information in recent years. K ey w ords :quantum wire ;quantum wire infrared photodetector ;photodetector ;infrared detector 在半导体理论中,将电子在各个方向均可以自由运动的结构称为三维结构,例如体材料.当电子在一个或几个方向的运动被限制在小于100nm 的范围内时,将出现量子尺寸效应,即形成一系列离散量子能级.电子在一个方向受限的结构称为量子阱;在2个方向受限的结构称为量子线;在3个方向受限则称为量子点,如图1所示.这些结构通常称为低维量子结构.由于其中至少有一个方向的尺寸小到纳米尺度(0.5～100nm ),故也称为低维纳米结构. 能量状态密度D (E )定义为单位能量变化区域内的能量状态数.D (E )随维数的变化如图1所示,随着维数的降低,连续能带消失,直至量子点中出现完全分立的能级.低维量子结构与体材料在D (E )上的差异,导致了它们电子性质上的不同.例如,与 体材料和量子阱相比,量子线在能带边上具有更加尖锐的电子态密度,这一点有望使量子线获得较高的量子效率,激发了人们对于量子线红外光子探测器(quantum wire infrared photodetector ,QRIP )的研究兴趣.QRIP 的发展潜力包括较高的工作温度、信噪比增加、暗电流降低、光谱波段较宽、以及垂直入射光响应等[1-3].以下介绍了近年来有关QRIP 的研究进展. 1 QRIP 的制备工艺 QRIP 可以利用Ⅲ-Ⅴ族、Ⅳ族或Ⅱ-Ⅵ族半 导体制成[1].图2为一种QRIP 的结构示意图,器件包含由一段量子线有源区和一段量子线势垒区构成 第23卷第6期2008年12月 光电技术应用 EL ECTRO -OPTIC TECHNOLO GY APPL ICA TION Vol.23,No.6December.2008
高中物理光学知识点总结
二、学习要求 1、知道有关光的本性的认识发展过程：知道牛顿代表的微粒、惠更斯的波动说一直到光的波粒二象性这一人类认识光的本性的历程，懂得人类对客观世界的认识是不断发展不断深化的。 2、知道光的干涉：知道光的干涉现象及其产生的条件；知道双缝干涉的装置、干涉原理及干涉条纹的宽度特征，会用肥皂膜观察薄膜干涉现象。知道光的衍射：知道光的衍射现象及观察明显衍射现象的条件，知道单缝衍射的条纹与双缝干涉条纹之间的特征区别。 3、知道电磁场，电磁波：知道变化的电场会产生磁场，变化的磁场会产生电场，变化的磁场与变化的磁场交替产生形成电磁场；知道电磁波是变化的电场和磁场——即电磁场在空间的传播；知道电磁波对人类文明进步的作用，知道电磁波有时会对人类生存环境造成不利影响；从电磁波的广泛应用认识科学理论转化为技术应用是一个创新过程，增强理论联系实际的自觉性。知道光的电磁说：知道光的电磁说及其建立过程，知道光是一种电磁波。 4、知道电磁波波谱及其应用：知道电磁波波谱，知道无线电波、红外线、紫外线、X 射线及γ射线的特征及其主要应用。 5、知道光电效应和光子说：知道光电效应现象及其基本规律，知道光子说，知道光子的能量与光学知识点其频率成正比；知道光电效应在技术中的一些应用 6、知道光的波粒二象性：知道一切微观粒子都具有波粒二象性，知道大量光子容易表现出粒子性，而少量光子容易表现为粒子性。 光的直线传播．光的反射 二、光的直线传播 1．光在同一种均匀透明的介质中沿直线传播，各种频率的光在真空中传播速度：C ＝3×108m/s ； 各种频率的光在介质中的传播速度均小于在真空中的传播速度，即 v