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Measurements of Proton, Helium and Muon Spectra at Small Atmospheric Depths with the BESS S

Measurements of Proton, Helium and Muon Spectra at Small Atmospheric Depths with the BESS S
Measurements of Proton, Helium and Muon Spectra at Small Atmospheric Depths with the BESS S

a r X i v :a s t r o -p h /0304102v 2 6 M a y 2003

Measurements of Proton,Helium and Muon Spectra

at Small Atmospheric Depths with the BESS

Spectrometer

K.Abe a ,?,1,T.Sanuki a ,K.Anraku a ,2,Y .Asaoka a ,3,H.Fuke a ,S.Haino a ,N.Ikeda b ,M.Imori a ,K.Izumi a ,T.Maeno b ,4,Y .Makida c ,S.Matsuda a ,N.Matsui a ,T.Matsukawa b ,

H.Matsumoto a ,J.W.Mitchell d ,A.A.Moiseev d ,J.Nishimura a ,M.Nozaki b ,S.Orito a ,5,J.F.Ormes d ,M.Sasaki c ,6,E.S.Seo e ,Y .Shikaze b ,T.Sonoda a ,R.E.Streitmatter d ,J.Suzuki c ,K.Tanaka c ,K.Tanizaki b ,T.Yamagami f ,A.Yamamoto c ,Y .Yamamoto a ,K.Yamato b ,T.Yoshida c ,K.Yoshimura c

a The

University of Tokyo,Bunkyo,Tokyo 113-0033,Japan

b Kobe

University,Kobe,Hyogo 657-8501,Japan

c High

Energy Accelerator Research Organization (KEK),Tsukuba,Ibaraki 305-0801,

Japan d National

Aeronautics and Space Administration (NASA),Goddard Space Flight Center,

Greenbelt,MD 20771,USA.

e University

of Maryland,College Park,MD 20742,USA

f Institute

of Space and Astronomical Science (ISAS),Sagamihara,229-8510,Japan

Preprint submitted to Elsevier Science 2February 2008

1Introduction

Primary cosmic rays interact with nuclei in the atmosphere,and produce atmo-spheric secondary particles,such as muons,gamma rays and neutrinos.It is impor-tant to understand these interactions to investigate cosmic-ray phenomena inside the atmosphere.For precise study of the atmospheric neutrino oscillation[1],it is crucial to reduce uncertainties in hadronic interactions,which are main sources of systematic errors in the prediction of the energy spectra of atmospheric neutrinos. At small atmospheric depths below a few ten g/cm2,production process of muons is predominant over decay process,thus we can clearly observe a feature of the hadronic interactions.In spite of their importance,only a few measurements have been performed with modest statistics because of strong constraints of short obser-vation time of a few hours during balloon ascending periods from the ground to the balloon?oating altitude.

In2001,using the BESS spectrometer,precise measurements of the cosmic-ray ?uxes and their dependence on atmospheric depth were carried out during slow descending from4.5g/cm2to28g/cm2for12.4hours.The growth curves of the cosmic-ray?uxes were precisely measured.The results were compared with the predictions based on the hadronic interaction models currently used in the atmo-spheric neutrino?ux calculations.

2BESS spectrometer

The BESS(B xperiment with a S pectrometer)de-tector[2,3,4,5,6]is a high-resolution spectrometer with a large acceptance to per-form precise measurement of absolute?uxes of various cosmic rays[7,8,9],as well as highly sensitive searches for rare cosmic-ray components.Fig.1shows a schematic cross-sectional view of the BESS instrument.In the central region,a uniform magnetic?eld of1Tesla is provided by a thin superconducting solenoidal coil.The magnetic-rigidity(R≡Pc/Ze)of an incoming charged particle is mea-sured by a tracking system,which consists of a jet-type drift chamber(JET)and two inner-drift-chambers(IDC’s)inside the magnetic?eld.The de?ection(R?1)is

calculated for each event by applying a circular?tting using up-to28hit-points, each with a spatial resolution of200μm.The maximum detectable rigidity(MDR) was estimated to be200GV.Time-of-?ight(TOF)hodoscopes provide the veloc-ity(β)and energy loss(d E/d x)measurements.A1/βresolution of1.4%was achieved in this experiment.For particle identi?cation,the BESS spectrometer was equipped with a threshold-type aerogel Cherenkov counter and an electromagnetic shower counter.The refractive index of silica aerogel radiator was1.022,and the threshold kinetic energy for proton was3.6GeV.The shower counter consists of a plate of lead with two radiation lengths covering a quarter area of the lower TOF counters,whose output signal was utilized for e/μidenti?cation.

The data acquisition sequence is initiated by a?rst-level TOF trigger,which is a simple coincidence of signals in the upper and lower TOF counter.In order to build a sample of unbiased triggers,one of every four events were recorded.The TOF trigger ef?ciency was evaluated to be99.4%±0.2%by using secondary proton beam at the KEK12GeV proton synchrotron.In addition to the TOF trigger,an auxiliary trigger is generated by a signal from the Cherenkov counter to record par-ticles above threshold energy without bias or sampling.An ef?ciency of Cherenkov trigger were evaluated as a ratio of the Cherenkov-triggered events among the un-biased trigger sample.It was95.1%for relativistic particles(β→1).For?ux determinations,the Cherenkov-triggered events were used only above9.5GV for protons,11.1GV for helium nuclei,and0.90GV for muons.Below these rigidities, the TOF-triggered events were used.

3Balloon?ight

The BESS-2001balloon?ight was carried out at Ft.Sumner,New Mexico,USA (34?49′N,104?22′W)on24th September2001.Throughout the?ight,the vertical geomagnetic cut-off rigidity was about4.2GV.The balloon reached at a normal ?oating altitude of36km at an atmospheric depth of4.5g/cm2.After a few hours, the balloon started to lose the?oating altitude and continued descending for more than13hours until termination of the?ight.During the descending period,data were collected at atmospheric depths between4.5g/cm2and28g/cm2.The atmo-spheric depth was measured with accuracy of±1g/cm2,which comes mainly from an error in absolute calibration of an environmental monitor system.Fig.2shows a balloon?ight pro?le during the experiment.

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4Data analysis

4.1Data reduction

We selected“non-interacted”events passing through the detector without any inter-actions.The non-interacted event was de?ned as an event,which has only one iso-lated track,one or two hit-counters in each layer of the TOF hodoscopes,and proper d E/d x inside the upper TOF counters.There is a slight probability that particles in-teract with nuclei in the detector material and only one secondary particle goes into the tracking volume to be identi?ed as a non-interacted event.These events were rejected by requiring proper d E/d x inside the upper TOF counters,because the interaction in the detector is expected to give a large energy deposit in the TOF counter.According to the Monte Carlo simulation with GEANT[10],these events are to be considered only below a few GeV.In order to estimate an ef?ciency of the non-interacted event selection,Monte Carlo simulations were performed.The probability that each particle can be identi?ed as a non-interacted event was eval-uated by applying the same selection criterion to the Monte Carlo events as was applied to the observed data.The systematic error was estimated by comparing the hit number distribution of the TOF counters.For muons,the simulated data were compared with muon data sample measured on the ground.The systematic error for protons below1GeV was directly determined by the detector beam test using ac-celerator proton beam[11].The resultant ef?ciency and its error of non-interacted event selection for protons was83.3±2.0%at1.0GeV and77.4±2.5%at 10GeV,and that for helium nuclei was71.6±2.6%at1.0GeV/n and66.0±2.9%at10GeV/n.The ef?ciency for muons was94.0±0.9%and92.8±0.8% at0.5GeV and10GeV,respectively.

The selected non-interacted events were required to pass through the?ducial vol-ume de?ned in this analysis.The?ducial volume of the detector was limited to the central region of the JET chamber for a better rigidity measurement.The zenith angle(θz)was limited within cosθz≥0.90to obtain nearly vertical?uxes.For the muon analysis,we used only the particles which passed through the lead plate to es-timate electron contaminations.For the proton and helium analysis,particles were required not to pass through the lead plate so as to keep the interaction probability inside the detector as low as possible.

In order to check the track reconstruction ef?ciency inside the tracking system,the recorded events were scanned randomly.It was con?rmed that996out of1,000vi-sually identi?ed tracks which passed through the?ducial volume were successfully reconstructed,thus the track reconstruction ef?ciency was evaluated to be99.6±0.2%.It was also con?rmed that rare interacted events are fully eliminated by the non-interacted event selection.

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4.2Particle identi?cation

In order to select singly and doubly charged particles,particles were required to have proper d E/d x as a function of rigidity inside both the upper and lower TOF hodoscopes.The upper TOF d E/d x was already examined in the non-interacted event selection.The distribution of d E/d x inside the lower TOF counter and the selection boundaries are shown in Fig.3.

In order to estimate ef?ciencies of the d E/d x selections for protons and helium nu-clei,we used another data sample selected by independent information of energy loss inside the JET chamber.The estimated ef?ciency in the d E/d x selection at 1GeV was98.3±0.4%and97.2±0.5%for protons and helium nuclei,respec-tively.The accuracy of the ef?ciency for protons and helium nuclei was limited by statistics of the sample events.Since muons could not be distinguished from elec-trons by the JET chamber,the d E/d x selection ef?ciency for muons was estimated by the Monte Carlo simulation to be99.3±1.0%.The error for muons comes from the discrepancy between the observed and simulated d E/d x distribution inside the TOF counters.The d E/d x selection ef?ciencies were almost constant in the whole energy region discussed here.

Particle mass was reconstructed by using the relation of1/β,rigidity and charge, and was required to be consistent with protons,helium nuclei or muons.An appro-priate relation between1/βand rigidity for each particle was required as shown in Fig.4.Since the1/βdistribution is well described by Gaussian and a half-width of the1/βselection band was set at3.89σ,the ef?ciency is very close to unity (99.99%for pure Gaussian).

4.3Contamination estimation

4.3.1Protons

Protons were clearly identi?ed without any contamination below1.7GV by the mass selection,as shown in Fig.4.Above1.7GV,however,light particles such as positrons and muons contaminate proton’s1/β-band,and above4GV deuterons (D’s)start to contaminate it.

To distinguish protons from muons and positrons above1.7GV,we required that light output of the aerogel Cherenkov counter should be smaller than the threshold. This requirement rejected96.5%of muons and positrons while keeping the ef?-ciency for protons as high as99.5%.The aerogel Cherenkov cut was applied below 3.7GV,above which Cherenkov output for protons begins to increase rapidly. Contamination of muons in proton candidates after the aerogel Cherenkov cut was

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estimated and subtracted by using calculated muon?uxes[20],which was nor-malized to the observed?uxes below1.0GeV where positive muons were clearly separated from protons.The positron contamination was calculated from the nor-malized positive muon?uxes and observed e/μratios.The resultant positive muon and positron contamination in the proton candidates was less than0.8%and4.1% below and above3.7GV,respectively,at26.4g/cm2where observed(μ+e)/p ratio is largest during the experiment.The error in this subtraction was estimated from the ambiguity in the normalization of the muon spectra to be less than0.2%and 0.8%below and above3.7GV,respectively.

Since the geomagnetic cut-off rigidity is4.2GV,most of deuterons contaminating proton candidates above4GV are considered to be primary cosmic-ray particles. The primary D/p ratio was estimated by our previous measurement carried out in1998–2000at Lynn Lake,Manitoba,Canada,where the cut-off rigidity is as low as0.5GV.The D/p ratio was found to be2%at3GV.No subtraction was made for deuteron contamination because there is no reliable measurement of the deuteron?ux above4GV.Therefore,above4GV hydrogen nuclei selected which included a small amount of deuterons.The D/p ratio at higher energy is expected to decrease[12]due to the decrease in escape path lengths of primary cosmic-ray nuclei[13]and the deuteron component is as small as the statistical error of the proton?ux.

4.3.2Helium nuclei

Helium nuclei were clearly identi?ed by using both upper and lower TOF d E/d x as shown in https://www.doczj.com/doc/1510399827.html,ndau tail in proton’s d E/d x might contaminate the helium d E/d x band,however this contamination from protons was as small as3×10?4.It was estimated by using another sample of proton data selected by d E/d x in the JET chamber.No background subtraction was made for helium.Obtained helium?uxes include both3He and4He.

4.3.3Muons

Electrons and pions could contaminate muon candidates.To estimate electron con-tamination,we used the d E/d x information inside the lower TOF counters covered with the lead plate.We calculated lower TOF d E/d x distribution for muons and electrons using the Monte Carlo simulation.The most adequate e/μratio was es-timated by changing weights both for muons and electrons so as to reproduce the observed d E/d x distribution.The simulated distributions well-agreed with the ob-served data as shown in Fig.5.The electron contamination was about10%of muon candidates at0.5GV,and less than1%above1GV.Since in the lower energy re-gion,the difference between the d E/d x distributions for electrons and muons are small,rejection power of d E/d x selection are lower.The error was estimated during

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the?tting procedure to be about5%at0.5GV and0.1%at8.0GV.Accuracy of the electron subtraction was limited by poor statistics of electron events.For the pion contamination we made no subtraction,thus the observed muon?uxes include pions.According to a theoretical calculation[14],theπ/μratio at a residual atmo-sphere of3g/cm2through10g/cm2was less than3%at1GV and less than10% at10GV.

Between1.6and2.6GV,protons contamination in the positive muon candidates and its error were estimated by?tting the1/βdistribution with a double-Gaussian function as shown in Fig6.The estimated ratio of proton contamination in muon candidates was less than3.3±1.3%.

4.4Corrections

In order to determine the proton,helium and muon spectra,ionization energy loss inside the detector material,live-time and geometrical acceptance need to be esti-mated.

The energy of each particle at the top of the instrument was calculated by sum-ming up the ionization energy losses inside the instrument with tracing back the event trajectory.The total live data-taking time was measured exactly to be40,601 seconds by counting1MHz clock pulses with a scaler system gated by a“ready”status that control the?rst level trigger.The geometrical acceptance de?ned for this analysis was calculated as a function of rigidity by using simulation technique[15]. In the high rigidity region where a track of the particle is nearly straight,the geo-metrical acceptance is0.097m2sr for protons and helium nuclei,and0.030m2sr for muons.The acceptance for muons is about1/3of that for protons and helium nuclei,because we required muons to pass through the lead plate while protons and helium nuclei were required not to pass through the lead plate.The simple cylindri-cal shape and the uniform magnetic?eld make it simple and reliable to determine the precise geometrical acceptance.The error which arose from uncertainty of the detector alignment was estimated to be1%.

5Results and discussions

The proton and helium?uxes in energy ranges of0.5–10GeV/n and muon?ux in 0.5GeV/c–10GeV/c,at small atmospheric depths of4.5g/cm2through28g/cm2, have been obtained from the BESS-2001balloon?ight.The results are summarized in Table1.The statistical errors were calculated as68.7%con?dence interval based on Feldman and Cousins’s“uni?ed approach”[16].The overall errors including both statistic and systematic errors are less than8%,10%and20%for protons,

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helium nuclei and muons,respectively.The obtained proton and helium spectra are shown in Fig.7.Around at3.4GeV for protons and1.4GeV/n for helium nuclei, a geomagnetic cut-off effect is clearly observed in their spectra.The proton spec-trum measured by the AMS experiment in1998[17]at the similar geomagnetic latitude(0.7<ΘM<0.8,whereΘM is the corrected geomagnetic latitude[18])is also shown in Fig.7.The AMS measured proton spectra in space(at an altitude of380km),which are free from atmospheric secondary particles7.In the BESS results the atmospheric secondary spectra for protons below2.5GeV are observed. Fig.8shows the observed proton and helium?uxes as a function of the atmospheric depth.Below2.5GeV the proton?uxes clearly increase as the atmospheric depth increases.It is because the secondary protons are produced in the atmosphere.In the primary?uxes above the geomagnetic cut-off,the?uxes attenuate as the at-mospheric depth increases.In this energy region,the production of the secondary protons is much smaller than interaction loss of the primary protons.This is be-cause the?ux of parent particles of secondary protons is much smaller due to the steep spectrum of primary cosmic rays.

Figs.9and10show the observed muon spectra together with theoretical predic-tions.The predictions were made with the hadronic interaction model,DPMJET-III[19],which was used for the evaluation of atmospheric neutrino?uxes[20]. The obtained proton?uxes were used to reproduce the primary cosmic-ray?uxes in the calculation.Fig.11shows the observed muon?uxes as a function of atmo-spheric depth together with the calculated?uxes.The calculated?uxes show good agreement with the observed data.Further detailed study of the hadronic interaction models will be discussed elsewhere.

6Conclusion

We made precise measurements of cosmic-ray spectra of protons,helium nuclei and muons at small atmospheric depths of4.5through28g/cm2,during a slow descending period of12.4hours,in the BESS-2001balloon?ight at Ft.Sumner, New Mexico,USA.We obtained the proton and helium?uxes with overall errors of8%and10%,respectively,in an energy region of0.5–10GeV/n.The muon ?uxes were obtained with an overall error of20%in a momentum region of0.5–10GeV/c.The results provide fundamental information to investigate hadronic interactions of cosmic rays with atmospheric nuclei.The measured muon spectra showed good agreement with the calculations by using the DPMJET-III hadronic interaction model.The understanding of the interactions will improve the accuracy of calculation of atmospheric neutrino?uxes.

Acknowledgements

We would like to thank NASA and the National Scienti?c Balloon Facility(NSBF) for their professional and skillful work in carrying out the BESS?ights.We are indebted to M.Honda and T.Kajita of ICRR,the University of Tokyo for their kindest cooperation for Monte Carlo simulations and theoretical interpretations.We would like to thank ISAS and KEK for their continuous support and encouragement for the BESS experiment.The analysis was performed with the computing facilities at ICEPP,the University of Tokyo.This experiment was supported by Grants-in-Aid(12047206and12047227)from the Ministry of Education,Culture,Sport, Science and Technology,MEXT.

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[19]S.Roeseler,et al.,SLAC-PUB-8740,hep-ph/0012252,unpublished.

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Fig.1.Cross sectional view of the BESS detector.

010203040

Local time(hour)

A l t i t u d e (k m )

-60

-40-200T e m p e r a t u r e (°C )

10

2030

Altitude(km)

A t m . d e p t h (g /c m 2

)

Fig.2.Altitude during the BESS-2001balloon ?ight experiment(top).Temperature and residual atmosphere as a function of altitude(bottom).

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1

10

Rigidity(GV)

Fig.3.Distribution of d E /d x inside the lower TOF counters.Solid lines show selection boundaries for protons and helium nuclei.Dashed lines show those for muons.

1

10

R(GV)

Fig.4.Distribution of 1/βfor Z =1particles.Solid lines show the selection boundaries for protons.Dashed lines show those for muons.

12

10

1

10

10

10

e v e n t

s

Fig.5.Observed and simulated distribution of d E /d x inside the lower TOF counters for the events in which track passed through the lead plate.Dashed line shows the selection bound-ary for 0501001502002503003504001/β

e v e n t s

Fig.6.An estimation of proton contamination by the TOF information.Hatched area shows an estimated proton contamination.

13

10

10

2

1

10

E kinetic (GeV/n)

F l u x (m -2s r -1s e c -1(

G e V /n )-1

)

-1

1

10

1

10

E kinetic (GeV/n)

Fig.7.The observed proton and helium spectra.The error bars include statistical error only.In the proton spectra,atmospheric secondary components are clearly observed below 2.5GeV in the BESS results.

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10

10

Atm. depth (g/cm 22

)

F l u x (m -2

s r -1s e c -1

(G e V /n )-1

)

1

10

Atm. depth (g/cm 2

2

)

Fig.8.The observed proton and helium ?uxes as a function of atmospheric depth.

15

10

-1

11010

2

Atm. depth (g/cm 2)

F l u x (m -2s r -1s e c -1(

G e V /c )-1)

-1

1

10

10

2

Atm. depth (g/cm 2)

Fig.11.The observed negative and positive muon ?uxes.The solid lines show theoretical predictions calculated by using DPMJET-III.

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氦氖激光器的调腔实验

氦氖激光器的调腔实验 (北京师范大学物理系) 摘要:本实验分别通过准直法和十字叉丝法来调节谐振腔两端腔镜的位置,使得两个腔镜平行且和毛细管垂直,发射激光,并通过统调法获得最强激光。 理论: 激光器由激励电流、增益介质和谐振腔组成,如图1。对He-Ne激光器而言增益介质就是在两端封有布儒斯特窗的毛细管内按一定的气压充以适当比例的氦氖气体,当氦氖混合气体被电流激励时,与某些谱线对应的上下能级的粒子数发生反转,使介质具有增益。 介质增益与毛细管长度、内径粗细、两种气体的比例、总气压以及放电电流等因素有关。对谐振腔而言腔长要满足频率的驻波条件,谐振腔镜的曲率半径要满足腔的稳定条件。总之腔的损耗必须小于介质的增益,才能建立激光振荡。由于介质的增益具有饱和特性,增益随激光强度增加而减小。初始建立激光振荡时增益大于损耗,随着激光的增强而增益逐渐减小直到增益等于损耗时才有持续稳定的振荡。 图1 激光器原理图 实验内容: 1.清洗镜头 在清洗镜头时候可以通过腔镜的具体情况选择合适的清洗方法,首先应用洗耳球吹去镜头上的灰尘等颗粒物,对于软膜我们采用拖曳的方法,首先将镜头放置在水平的桌面上,取一张镜头纸并将光滑一面放置在镜头上,并且在此之前确保不会用手去接触光滑面,在擦镜纸上接触镜头的部位滴一到两滴丙酮试剂,轻轻拖曳擦镜纸的一端直到整张擦镜纸擦过镜头。

图2 软膜清洗法 对于硬膜,洗耳球吹去镜头上的灰尘等颗粒物之后,将镜头着对折,如图,用止血钳夹住擦镜纸,露出一段,在露出一端上滴一到两滴丙酮,轻甩之后擦 拭镜头,擦拭的过程保证擦拭方向永远朝着一个方向,不来回擦拭。 图3 硬膜清洗法 2.准直法调腔 用具:He-Ne激光器、准直激光器、贴有白纸的立板。 步骤: (1)通过上述方法清洗完镜头和布儒斯特窗后,打开准直激光器; (2)首先调节准直激光器的上下高度和俯仰角度,使得准直激光器打出来的光与毛细管的中心在同一水平线上; (3)将准直激光器固定在谐振腔一端的前段,将激光穿透整个毛细管,此时可以调节准直激光器的横向位移和左右偏移动,直到穿透的光打在对面的白 纸上呈现同心圆环状; (4)装上阴极反射镜,调整反射镜的左右偏转和俯仰,使反射回的激光与出来的激光重合出现在准直激光器镜头上的正中心; (5)装上阳极反射镜,调整反射镜的左右偏转和俯仰,使反射回的激光出现规则的明暗变化;

如何成功治愈肿瘤——氩氦刀冷冻治疗

肿瘤治疗新突破——氩氦刀冷冻治疗 肿瘤即机体在各种致癌因素作用下,局部组织的某一个细胞在基因水平上失去对其生长的正常调控,导致其克隆性异常增生而形成的异常病变。 肿瘤是一种常见病、多发病,也是因危害性极大、难治愈等特点令人望而生畏的疾病,其中恶性肿瘤(俗称“癌症”)是仅仅次于心血管疾病居第二位造成人类高死亡率的疾病。 但随着科技的发展和进步,各种医疗新技术的开发,让肿瘤变得不再可怕,在众多新技术中,氩氦刀冷冻治疗技术的效果尤为突出。 氩氦刀并不是真正意义上的手术刀,它是一种可以经皮摘除体内病变组织的微创技术。这种采用多项美国太空火箭制导技术和十余项欧美专利的氩氦刀系统,是世界上第一个、也是惟一具有超低温冷冻和热疗双重效能的医疗系统,为肿瘤的治疗技术带来了新的突破和发展。 氩氦刀冷冻治疗就是在CT或B超的引导下,用特殊的超细穿刺针,直接准确地定位穿入癌瘤组织,到达病灶后,通过氩气和氦气的转换,几分钟内将癌瘤组织冻成冰球,使病灶处的局部温度下降至零下100多度,在细胞内外迅速形成冰晶,使肿瘤细胞破裂,彻底摧毁肿瘤细胞,组织坏死。同时坏死的细胞还能刺激机体产生抗体,提高免疫能力。氩氦刀冷冻治疗代表着国际二十世纪九十年代超低温冷冻治疗仪器的最先进水平,激起了超低温手术和癌瘤治疗的革命。 氩氦刀治疗肿瘤有许多独特的优点,如不开刀、不出血或少出血,手术损伤轻微,病人痛苦小,恢复快;成功率高,并发症少;可以重复做;既可单独施行也可与放化疗或血管栓塞疗法结合应用;效果显著,操作简便。 氩氦刀冷冻治疗实体肿瘤的范围非常广泛,如肝癌、肺癌、肉瘤、骨转移瘤、软组织肿瘤、肢体肿瘤、颅内肿瘤等有非常好的治疗效果,使许多本来不能切除的肿瘤得到根治的机会,大大提高了晚期肿瘤患者的生存质量和存活时间。 更重要的是,由于氩氦刀制冷或加热只局限在超冷刀尖端,刀杆又有很好的热绝缘,因此不会对穿刺路径上的组织产生损伤。对早、中期肿瘤,可以达到治愈的效果;对于晚期较大的压迫周围脏器的肿瘤,亦可作为姑息治疗手段,减轻肿瘤负荷,减轻疼痛及压迫症状,提高生活质量,延长生存时间,是临床肿瘤治疗的一种新思路新方法。

5-1 氦氖激光器的模式分析 实验报告

近代物理实验报告 指导教师: 得分: 实验时间: 2009 年 03 月 17 日, 第 三 周, 周 三 , 第 5-8 节 实验者: 班级 材料0705 学号 200767025 姓名 童凌炜 同组者: 班级 材料0705 学号 200767007 姓名 车宏龙 实验地点: 综合楼 501 实验条件: 室内温度 ℃, 相对湿度 %, 室内气压 实验题目: 氦氖激光器的模式分析 实验仪器:(注明规格和型号) 扫描干涉仪;高速光电接收器;锯齿波发生器;示波器; 半外腔氦氖激光器及电源;准直用氦氖激光器及电源;准直小孔。 实验目的: (1) 了解扫描干涉仪原理,掌握其使用方法; (2) 学习观测激光束横模、纵模的实验方法。 实验原理简述: 1. 激光器模式的形成 激光器由增益介质、谐振腔、激励能源三个基本部分组成。如果用某 种激励的方式,使介质的某一对能级间形成的粒子数反转分布,由于 自发辐射的作用,将有一定频率的光波产生,并在谐振腔内传播,被 增益介质增强、放大。形成持续振荡的条件是:光在谐振腔内往返一 周的光程差为波长的整数倍,即 q q uL λ=2 满足此条件的光将获得极大的增强。 每一个q 对应纵向一种稳定的电磁场分布λq ,叫一个纵模,q 称为纵模 序数。纵模的频率为 uL c q q 2=ν 相邻两个纵模的频率间隔为 uL c q 21= ?=?ν 因此可以得知, 缩短腔长的方法是获得单纵模运行激光器的办法之一。

当光经过放电毛细管时,每反馈一次就相当于一次衍射,多次反复衍射,就在横向的同一波腹处形成一个或多个稳定的衍射光斑。每一个衍射光斑对应一种稳定的横向电磁场分布,称为一个横模。模式指激光器内能够发生稳定光振荡的形式,每一个膜,既是纵模,又是横模,纵模描述了激光器输出分立频率的个数,横模描述了垂直于激光传播方向的平面内光场的分布情况。激光的线宽和相干长度由纵模决定,光束的发散角、光斑的直径和能量的横向分布由横模决定。,一个膜由三个量子数表示,通常记作TEM mnq 。 横模序数越大,频率越高。不同横模间的频率差为: ?? ??????????????--?+?=?2/121,)1)(1(arccos )(12''R L R L n m uL c n m mn πν 相邻横模频率间隔为: ?? ??????????????--?=?=?=?+?2/12111)1)(1(arccos 1'R L R L q n m πνν 相邻横模频率间隔与纵模频率间隔的比值是一个分数,分数的大小由激光器的腔长和曲率半径决定,腔长与曲率半径的比值越大,分数值就越大。 另外, 激光器中产生的横模个数,除了与增益有关外,还与放电毛细管的粗细、内部损耗等因素有关。 2. 共焦球面扫描干涉仪 共焦球面干涉仪用压电陶瓷作为扫描元件或用气压进行扫 描。 2.1 共焦球面扫描干涉仪的机构和工作原理 共焦球面扫描干涉仪是一个无源腔,由两块球形凹面反射镜 构成,两块镜的曲率半径和腔长相等(即R 1=R 2=l ,构成共焦 腔)。其中一块反射镜固定不动,另一块反射镜固定在可随 外电压变化而变化的压电陶瓷环上。如右图所示,由低膨胀 系数材料制成的间隔圈,用以保持两球形凹面反射镜R 1、R 2 总处于共焦状态。 当一束波长为λ的光近轴入射到 干涉仪内时,在忽略球差的条件 下,在共焦腔中经四次反射形成 一条闭合路径,光程近似为4l , 如右图所示 编号为1和1’ 的两组透光强分别为: 1222201]sin )12(1)[1(--+-=βR R R T I I 和 121'I R I = β为往返一次所形成的相位差,即

光纤激光器简介

目录 第一章、激光基础 第二章、激光器 第三章、光纤的特性 第四章、光纤激光器 第五章、实验室激光器型号及操作安全

第一章激光基础 1.1什么是激光? 激光在我国最初被称为“莱赛”,即英语“Laser”的译音,而“Laser”是“Light amplification by stimulated emission of radiation”的缩写。意为“辐射的受激发射光放大”,大约在1964年,根据钱学森院士的建议,改名为“激光”。激光是通过人工方式,用光或者放电等强能量激发特定的物质而产生的光。 激光的四大特性:高亮度、高单色性、高方向性、高相干性。具有高亮度的激光束经过透镜聚焦后,能在焦点附近产生数千度乃至上万度的高温,这就使其能够加工几乎所有材料。由于激光的单色性极高,从而保证了光束能精确地聚焦到焦点上,得到很高的功率密度。 1.2激光产生的基本理论 1.2.1原子能级和辐射跃迁 按照玻尔的氢原子理论,绕原子核高速旋转的电子具有一系列不连续的轨道,这些轨道称为能级,如图1-1。 图1-1 原子能级图

当电子在不同的能级时,原子系统的能量是不相同的,能量最低的能级称为基态。当电子由于外界的作用从较低的能级跃迁到较高的能级时,原子的能量增 图1-2 电子跃迁图 加,从外界吸收能量。反之,电子从较高能级跃迁到较低能级时,向外界发出能量。在这个过程中,若原子吸收或发出的能量是光能(辐射能),则称此过程为辐射跃迁。发出或吸收的光的频率满足普朗克公式(hv=E2-E1)。 1.2.2受激吸收、自发辐射、和受激辐射 受激吸收:处于低能级上的原子,吸收外来能量后跃迁到高能级,则称之为受激吸收。 自发辐射:由于物质有趋于最低能量的本能,处于高能级上的原子总是要自发跃迁到低能级上去,如果跃迁中发出光子,则这个过程称为自发辐射。

无痛无麻醉恢复快 全面剖析氩氦刀肿瘤消融治疗

无痛无麻醉恢复快全面剖析氩氦刀肿瘤消融治疗 随着科技的进步,与传统治疗相比,在治疗肿瘤方面微创治疗技术逐渐得到广泛的认可和支持。随着介入微创治疗技术和影像设备的完善和发展,肿瘤消融治疗已经成为一种快速原位灭活肿瘤细胞并对正常组织尽最大限度保护作用的微创治疗方法。 氩氦刀冷冻消融作为肿瘤消融治疗的手段之一,因其创伤小、效果显著、安全性高、患者耐受性好等优点逐渐受到广泛的关注,目前该技术已在实体肿瘤治疗中显示出显著的疗效。

发展:氩氦刀消融治疗如何形成 氩氦刀是一种先进的肿瘤微创治疗技术。外科手术切除是以往公认的肿瘤治疗方法,但约70%的肿瘤患者确诊时已无法手术,通常是因为肿瘤部位关键、边界不清及体积较大而无法彻底切除,或患者年老体弱、身体状况不能耐受手术,或肿瘤发生远处转移而失去手术机会。常规的放疗和化疗对实体瘤的作用有限且副作用大,治疗中耐药性和治疗敏感性问题均是目前临床上难以逾越的屏障。因此,以原位灭活肿瘤细胞、消除肿瘤负荷为目的的氩氦刀冷冻消融术得到广泛应用。 氩氦刀治疗系统可在超声、CT或磁共振成像(MRI)引导下经皮穿刺对肿瘤实施精确的消融治疗,其创伤小、手术操作简便,且不影响其他综合治疗方法的实施。 原理:氩氦刀消融治疗为什么能杀死肿瘤 氩氦刀采用了氩气制冷、氦气制热、适时监控等多项电子计算机和航天技术。 氩氦刀最细刀头外径仅为1.47mm,中空绝缘。循环氩气时,刀尖温度瞬间降至零下140℃,在几分钟内将肿瘤组织冻成冰球,使肿瘤细胞破裂坏死。而在循环氦气时,刀尖温度则快速升温至20~45℃,将冰球融化,使肿瘤细胞崩解,加速肿瘤组织变性坏死。如此冷热循环逆转,彻底摧毁癌瘤组织,同时低温损伤小血管引起微循环血栓形成进而导致组织缺血坏死。 人体并未立即清除冷冻坏死的肿瘤组织,但坏死组织可作为抗原激活和促进机体产生抗肿瘤免疫反应,提高人体全身免疫力,启动对肿瘤细胞的免疫杀伤作用,进一步抑制肿瘤。 据报道,少数病例在原位肿瘤冷冻灭活后,其他部位转移瘤亦消退,其机制尚未完全明确。 特点:氩氦刀消融治疗与其他消融治疗技术的区别

5-1 氦氖激光器的模式分析 实验报告

近代物理实验报告 指导教师: 得分: 实验时间: 2009 年 03 月 17 日, 第 三 周, 周 三 , 第 5-8 节 实验者: 班级 材料0705 学号 200767025 姓名 童凌炜 同组者: 班级 材料0705 学号 200767007 姓名 车宏龙 实验地点: 综合楼 501 实验条件: 室内温度 ℃, 相对湿度 %, 室内气压 实验题目: 氦氖激光器的模式分析 实验仪器:(注明规格和型号) 扫描干涉仪;高速光电接收器;锯齿波发生器;示波器; 半外腔氦氖激光器及电源;准直用氦氖激光器及电源;准直小孔。 实验目的: (1) 了解扫描干涉仪原理,掌握其使用方法; (2) 学习观测激光束横模、纵模的实验方法。 实验原理简述: 1. 激光器模式的形成 激光器由增益介质、谐振腔、激励能源三个基本部分组成。如果用某种激励的方式,使介质的某一对能级间形成的粒子数反转分布,由于自发辐射的作用,将有一定频率的光波产生,并在谐振腔内传播,被增益介质增强、放大。形成持续振荡的条件是:光在谐振腔内往返一周的光程差为波长的整数倍,即 q q uL λ=2 满足此条件的光将获得极大的增强。 每一个q 对应纵向一种稳定的电磁场分布λq ,叫一个纵模,q 称为纵模序数。纵模的频率为 uL c q q 2=ν 相邻两个纵模的频率间隔为 uL c q 21= ?=?ν 因此可以得知, 缩短腔长的方法是获得单纵模运行激光器的办法之一。

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氩氦刀冷冻治疗恶性肿瘤的影像学分析

氩氦刀冷冻治疗恶性肿瘤的影像学分析 发表时间:2014-01-02T14:30:05.420Z 来源:《医药前沿》2013年11月第32期供稿作者:王绍龙 [导读] 治疗前要进行局部麻醉,全面掌握病变的大小、位置,而后明确冷冻探针的数量、深度和路径。用超声进行动态引导。王绍龙(安阳市肿瘤医院影像科 455000) 【摘要】目的探讨氩氦刀冷冻治疗恶性肿瘤在的影像学中的价值;方法分析2012年8月至2013年8月我院应用氩氦刀冷冻治疗恶性肿瘤94例患者的效果;结果经过3个月的治疗,病灶明显缩小,但是肿瘤直径超过3厘米的结果则与之相反;结论氩氦刀在治疗恶性肿瘤的术中情况较好,无明显并发症,术后恢复快。 【关键词】氩氦刀恶性肿瘤影像学 【中图分类号】R730.4 【文献标识码】A 【文章编号】2095-1752(2013)32-0188-02 随着计算机技术的不断发展,低温冷冻技术作为一种全新的治疗肿瘤的方法被广泛应用,本文选取2012年8月至2013年8月在我院进行恶性肿瘤治疗的94例患者作为研究对象,给予其低温冷冻治疗,效果较为突出,具体情况现报道如下。 1 资料与方法 1.1 一般资料 本组资料共计94例,均为2012年8月至2013年8月在我院进行恶性肿瘤治疗的患者,其中男53例,女41例,年龄37~77岁,平均53.2±2.6岁。 1.2 方法 治疗前要进行局部麻醉,全面掌握病变的大小、位置,而后明确冷冻探针的数量、深度和路径。用超声进行动态引导。CT引导过程中,在肿瘤的位置处用胶布团或橡皮盖进行标记,接着予以CT扫描。在布针的时候不要对附近的关键结构或组织造成伤害,而后尽可能的消除肿瘤组织。若肿瘤低于3厘米,那么可直接单根探针;若3~6厘米,那么要探入两根针,两针的间隔为2至3厘米。若患者是颅脑肿瘤,那么要先进行颅骨开窗,接着在CT引导下进行冷冻治疗。若患者的病灶较大,那么要在将探针和外鞘退出20~30毫米后,继续再治疗。 1.3 观察指标 观察冰球的大小、形成时间、冰球覆盖率、CT及超声表现以及治疗完成2星期时的病灶病理学变化和3个月病灶的缩小程度。 2 结果 2.1 冰球形成的时间 在接入氩气60秒内,温度马上下降到-130℃,在进行冷冻的过程中,温度始终在-150℃处维持着。有88.3%的病灶在形成冰球的时间均在50秒内。 2.2 超声和CT表现 (1)超声表现:冰球初步形成时,冰球外围的横断面有弧形的强回声,纵断面有强烈的回声并轻微向前隆起,后面有轻微的声影;(2)CT表现:冷冻后马上进行扫描,冷冻部分的密度现相互下降,辩解较清晰,CT值是-10~15HU。由于时间的增加,病灶的密度呈不均匀的增长趋势,最终钙化纤维化到高密度。 2.3 冰球大小变化 冷冻的时间在5至15分钟的时候冰球的变化是最佳显著的,而15至20分钟时其增加的幅度并不明显。 2.4 冰球覆盖率及病灶缩小率 肿瘤直径小于3厘米的冰球覆盖率很高,经过3个月的治疗,病灶明显缩小,但是肿瘤直径超过3厘米的结果则与之相反。 2.5 术中并发症 超声引导下4例肝肾间隙出血,3例肝包膜下出血,2例胆汁漏;CT引导下6例少量气胸。没有大量气胸、出血性休克等重大并发症。 3 讨论 氩氦刀属于是低温冷冻设备的一种,主要分为导线、探针、主机三部分[1]。经探针可将冷媒氩气导入,此时局部的温度就会迅速下降,组织就会出现变性坏死。经实验表明,温度较低就会在细胞内形成冰晶,冰晶在较低的温度下就会杀死组织,然而,在多数情况下肿瘤组织对低温的承受能力要远远超过正常细胞。在本次研究中,在接入氩气60秒内,温度马上下降到-130℃,在进行冷冻的过程中,温度始终在-150℃处维持着。有88.3%的病灶在形成冰球的时间均在50秒内。衡量冷冻效果的一个最显著的指标就是冰球的大小。临床中认为,当冰球的边缘多余病灶1厘米时被称为最佳冷冻[2]。但是在实际操作的过程中,是无法对内部情形进行全面观察的,所有在本次研究中选择CT和超声影像学对其进行监测,不仅能够准确的监测到冰球的变化情况,还能够及时发现术中存在问题及术后并发症。经相关研究表明,冷冻的时间在5至15分钟的时候冰球的变化是最佳显著的,而15至20分钟时其增加的幅度并不明显。这也就表明氩氦刀在一个周期内的最佳冷冻时间是15分钟。经超声监测的结果与之完全吻合。因为由于病灶的部位、形状、大小等关系各部相同,所以在进行氩氦刀治疗的过程中将所有的病灶全部切除是很不现实的问题。此次研究中,肿瘤直径小于3厘米的冰球覆盖率很高,经过3个月的治疗,病灶明显缩小,但是肿瘤直径超过3厘米的结果则与之相反。这也就表示小于3厘米的肿瘤采用氩氦刀进行低温冷冻治疗的效果更好。 本次研究表明,氩氦刀在治疗继发或原发肿瘤,特别是病灶位置较为特殊的选择手术难以治愈的方面效果更加明显,它的术中情况较好,无明显并发症,术后恢复快。 参考文献 [1]苏海庆, 叶海洪, 黄筱华, 等. 超声在氩氦刀冷冻治疗肝癌中的价值研究[J]. 中国医学影像技术, 2003, 19(8) : 1055-1057. [2]王洪武, 段蕴铀, 张燕群, 等.CT 引导下经皮肺穿刺氩氦靶向治疗肺转移癌[J]. 海军总医院学报,2003,16(3): 152-155.

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