Hi ngh Sinh vin NCKH khoa Vt l nm 2013

Hi ngh Sinh vin NCKH khoa Vt l nm 2015

NH GI NH HNG CNG SUT, TN S LP LI CA LASER KCH THCH TRONG PHP O THI GIAN SNG HUNH QUANG

Hong Th Hi Yn1, Vng Vn Cng1, Phm Hng Minh21Khoa Vt l, Trng i hc s phm H Ni2Trung tm in t hc lng t, Vin Vt l, VAST1. M UKhi chiu nh sng c tn s thch hp vo mt s cht s xy ra hin tng hunh quang. Thi gian sng hunh quang l mt thng s ng hc v cng quan trng. N c trng cho phn t trong mt mi trng v cung cp nhng thng tin nh v: kh nng hp th, pht x laser; s bin i cu trc phn t v c bit trong s truyn nng lng gia hai phn t khc nhau.Vic xc nh thi gian sng hunh quang c ngha to ln trong nghin cu cc cht. V vy, ta cn kho st nh hng tn s lp li v cng sut ca laser kch thch i vi thi gian sng hunh quang iu chnh ph hp cho tng cht nhm khng lm sai lch thi gian sng.2. NI DUNG NGHIN CU2.1. H th nghim2.1.1. K thut o m n photon tng quan thi gianHnh 1. Nguyn l tng qut ca k thut m n photon tng quan thi gian [1,3]

Hnh 2. S tng qut ca h m n photon tng quan thi gian [1,2,3]H hot ng nh sau: Xung laser c qua gng chia, mt phn c dng kch thch mu, mt phn dng lm xung trigger so snh. Tn hiu nh sng t mu pht quang c hi t v qua filter hoc qua my n sc thu nh sng n sc. H quang hc c iu chnh ph hp tn hiu nh sng ti u thu l nhng photon n l. Tn hiu n photon c chuyn thnh xung tn hiu in t u thu, sau c khuch i qua khi tin khuch i v n b CFD. Ton b h quang v u thu phi c t trong bung ti trnh nhiu nh sng bn ngoi. B CFD cho php trigger v ly mu nhanh vi chnh xc v n nh cao. Xung tn hiu ra t CFD c chuyn thnh xung TTL v n khi TDC vi vai tr xung start (nu s dng TAC phi c thm b chuyn i tng t s - ADC). Phn laser c s dng to xung so snh c thu bng mt u thu nhanh (nh PIN photodiode). Xung so snh sau khi c qua b tch xung (discriminator c th l theo phng php leading-edge hoc CFD) cng s c chuyn i thnh xung TTL v n TDC vi vai tr xung stop. Khi TDC s o thi gian t xung start n xung stop, d liu thi gian c chuyn sang dng tn hiu s v c ghi vo b nh. Card c v ghi d liu, chuyn sang my tnh my tnh dng li biu theo thi gian ca cng [1,2,3].2.1.2. Mu o

CdTe: C=10-3M, nh ph hunh quang 610nm.

Thi gian sng hunh quang di. C nhng ng dng ht sc to ln trong rt nhiu lnh vc nh quang in t, y sinh, thng tin lng t, RhB: C= 10-5M. nh ph hunh quang 580nm Thi gian sng hunh quang ngn. Rhodamine B c s dng trong sinh hc nh mt loi thuc nhum nhum hunh quang, i khi kt hp vi auramine O, nh cc vt auramine-rhodamine chng minh sinh vt acid-nhanh chng, c bit l Mycobacterium. Rhodamine B c khi c s dng nh mt loi thuc nhum laser.2.1.3. Cng sut v tn s lp li ca Laser kch thch.a, Cng sut Cng sut ca laser c thay i nh thay i th ngun nui.

Hnh 3. S ph thuc cng sut ca laser theo in th

Bng 1. S ph thuc cng sut ca laser theo in thin th(V)8910111213141516

Cng sut(W)72033445361677378

b, Tn s lp li

Tin hnh o thi gian sng hunh quang hai tn s: 4MHz v 12MHz.2.2. Kt qu v tho lun2.2.1. S ph thuc ca thi gian sng hunh quang vo cng sut laser kch thch.

ab

Hnh 4. S ph thuc ca thi gian sng hunh quang CdTe(a) v RhB(b) vo cng sut laser kch thch.

Tho lun: Khi thay i cng sut laser, thi gian sng hunh quang gn nh khng thay i. Do cng sut ca laser thay i t, khng lm thay i mng v kch thc ht nn thi gian sng hunh quang gn nh khng thay i. C s sai khc l do fit hm trong qu trnh x l s liu.2.2.2. S ph thuc ca thi gian sng hunh quang vo tn s laser kch thch

Hnh 5.Ph hunh quang CdTe khi b kch thch bi laser tn s 4Mhz(a) v 12Mhz(b).

Hnh 6. Ph hunh quang RhB khi b kch thch bi laser tn s 4Mhz( a) v 12 MHz(b).Bng 2. Thi gian sng hunh quang ca CdTe v RhB tn s 4 MHz v 12 MHz ti in th 9V.CdTeRhB

Tn s(MHz)412412

Thi gian(ns)22,0847512,873111,802311,81028

Tho lun:

Vi tn s12 Mhz th thi gian thu d liu nhanh gp 3 ln khi dng 4Mhz do chu k kch gim 3 ln.

Vi RhB c thi gian sng ngn nn thch hp vi c 4Mhz v 12 Mhz.

Vi CdTe do c thi gian sng di nn dng tn s 4 Mhz l hp l nht. Nu dng tn s12 Mhz th do CdTe c thi gian sng di ( c 22 ns) nn khi CdTe cha kp hi phc v trng thi cn bng th li b xung laser khc kch thch lm cho thi gian sng b o sai.3. KT LUN Khi cng sut ca laser thay i nh, thi gian sng hunh quang ca mu khng thay i do cu trc ht khng thay i. Khi o thi gian sng hunh quang cn ch ti tn s laser kch thch v: i vi mu c thi gian sng ngn th khng nh hng khi thay i tn s, nhng vi nhng mu c thi gian sng di nh CdTe th c nh hng rt ln. TI LIU THAM KHO[1]. o Duy Thng (2011), Lun vn thc s H m n photon ng dng trong nghin cu thi gian sng pht quang ca mt s vt liu cu trc nano, trng i hc Cng ngh- i hc Quc Gia H Ni.[2]. J. R. Lakowicz (2006), Principles of Fluorescence Spectroscopy - 3rd Ed. Springer, New York, Ch. 13.[3]. W. Becker (2005), Advanced time-correlated single photon counting techniques, Springer. Gio vin hng dn

Ngun kch thch

CFD

TDC

Tn hiu in

Gng chia.

Amp

TTL

H quang hc

u thu

u thu

Mu

My tnh

Khi c v truyn d liu

Xung stop

CFD

Xung start

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