- Genie2000, Canberra (2000)
1chieu dai biic xa (XQ)
20
Be dSy bia Ta
Hinh 3.13. Phan bo natron nhiet theo bi day bia Ta
Khi be day Ta nho thong lugng natron nhiet tang va dat cue dai tai bk day bia CO Icm tuong ung voi 1,2 XQ sau do khi tilp tuc tang bk day th6ng lugng
notron se giam do sir hap thu cac photon va notron trong vat lieu Tạ Ket qua thu dugc phii hgp voi cac toan ly thuyet su dung phuong phap Monte- Carlo[l,8].
3.3.3. Phan bo thong lugng cua notron nhanh
t f
De do phan b6 notron nhanh thi nghiem da sir dung la do Al thong qua phan ling bat notron: ^ Al(n,a) Nạ Cac dac tarng co ban cua phan ling dugc dua ra trong Bang 3.10. Hoat do phong xa ciia cac la " Na dugc hinh thanh sau khi chieu dugc xac dinh dira tren dien tich dinh pho gamma 1368.63 KeV.
Hinh 3.14 la dang ph6 gamma dac trung cua cac la do Al dugc kich hoat trong truong buc xa phat ra tu bia Pb. Viec ghi nhan va xu ly ph6 dugc thuc hien tren may tinh vai phan mem Genie 2000 (Canberra).
Bang 3T0. Dac trung phan ling ^^AI(n,a)^'^Na: Phan ling hat
nhan ^^Al(n,a)^^Na Nang lugng nguong, Eth 3,25 MeV T 1/2 14,96 gio a bam 687,7E-6
Nang lugng cac tia gammăkeV(%))
1368,63(100)
• 7
Hinh 3.14 la dang ph6 gamma dac trung ciia cac la do Al dugc kich boat trong truang biic xa phat ra tu bia Pb. Viec ghi nhan va xii ly ph6 dugc thuc hien tren may tinh voi phan mem Genie 2000 (Canberra).
ỊOEOBE 1.0E05 1.0E05 ^^ 1000 >o CO 100 10 1368.63 keV. Nâ-^ SV* i^'^'if^^ff •^^M^/l^m^-i"'"^*'^^'^'^'' 1 1.00 642-00 128200 192200 256100 Nang lUDng (ke\0
Hinh 3.14. PhS gamma dgc tnmg cua la Al duac kich hogt trong truang buc xgphdt ra tu bia Pb
Tu cac ph6 biic xa gamma ciia la ^''Na thu dugc trong phan Lrng-^Al(n,a)^^Na, tai cac dilm c^n do thong lugng tuong doi ciia notron nhiet. xac dinh dugc dien tich dinh buc xa gamma dac trung, tu do xac dinh dugc thong lugng tich phan cila notron nhanh. Phan b6 thong lugng ciia notron nhanh dgc theo be day cua bia Pb dugc dua ra tren Hinh 3.15.
c c (0 JC c c 2 2 c c §• c T ! thirc nghiem -dudng khdp Be d a y bia Pb (cm) f ^
Hinh 3.15.. Phan bo thong luang natron nhanh theo be day bia Pb
f r 1
Tu cac so lieu thuc nghiem theo phuong phap binh phuong toi thieu
r y
xac dinh ham giai tich m6 ta phan bo notron nhiet theo be day x ciia biạCac s6 lieu thuc nghiem dugc lam khop voi ham da thiic: