Tiiu ban: Nghiin cim ca ban trong ITnh virc Todn, Ly ISBN: 978-604-913-009-0
NGHIEN Ctru VAT LY HAT NHAN TAI VIEN V A T LY
• • • • •
STUDYING NUCLEAR PHYSICS AT INSTITUTE OF PHYSICS
Le Hong Khiem
Trung tam Vat ly Hat nhan, Vien Vat ly, Vien KHCNVN Tom tat:
Bdo cdo ndy se diim lgi nhirng hogt ddng chinh cita Trung tdm Vdt ly Hgt nhdn thude Viin Vdt ly ki tir khi mdi thdnh ldp cho din nay. Nhirng hirdng nghien citu hiin tai dang duac trien khai cimg vdi cdc kit qud dd dgt ciing se duac dua ra.
Bdo cdo ciing se trinh bdy ngdn ggn dinh hudng phdt trien cua Trung tdm Vdt ly Hgt nhdn trong thdi gian tdi.
Abstract:
The main activities of the Center for Nuclear Physics since it was established will be presented in this paper. The current research topics will be described. The future research plan of the Center will be presented as well.
1. Mo dau
Trung tam Vat ly Hat nhan la mgt trong so cac dan vi nghien cuu quan trgng ciia Vien Vat ly. Hien tai, Trung tam Vat ly Hat nhan gom c6 20 can bg trong do co 2 giao su, 1 ph6 giao su, 5 tien si va 5 thac sT. Trong nhung nam qua, Trung tam da day manh nghien cim ca ban. Linh vuc nghien ciiu cua Trung tam la : nghien cim cau tnic hat nhan va phan ung hat nhan sir dung cac chiim buc xa tir cac may gia toe. Ngoai cac de tai nghien cuu vat ly hat nhan ca ban, Trung tam ciing buoc dau trien khai cac nghien cuu ung dung va tham gia tich cue vao viec dao tao. Nhiing boat dgng chinh ciia Trung tam se dugc trinh bay mgt each tom tit trong bao cao nay.
2. Cac huo-ng nghien cihi da va dang duoc trien khai tai Trung tam Vat ly Hat nhan Tai Trung tam Vat ly Hat nhan co 2 may gia toe nho va ciing la cac may gia tic diu tien ciia Viet Nam. May thu nhat la may phat notron san suit tai Hungary NA-3C lam viec vai thi nuoi 120 kV va tao ra chiim notron 14 MeV qua phan ung ^T(D,n)'*He. Thong lugng cua chiim notron dat tod gia tri 10'° notron/giay.
May gia toe thii hai la Microtron MT-17 do Vien lien hgp Nghien ciru Hat nhan Dubna chi tao. May nay gia toe chiim electron den nang lugng 15 MeV va dong electron eo thi dat din gia tri 18 p A. Cbirni electron nay dugc ham trong bia nang W dl tao ra chiim hire xa ham co pho nang lugng lien tuc den gia tri cue dai 15 MeV. Ngoai ra, co thi tao ra notron bing each cho chiim hue xa ham di qua bia phan bach Uran. Khi do se xay ra phan img quang phan bach voi viec tao ra notron. Thong lugng cua chiim notron tao ra bing each nay co thi dat tai gia trj lO" notron/giay.
May phat notron NA-3C va may gia tic Microtron MT-17 da dugc khai thac trong nhieu nam truac day de nghien ciiu vat ly hat nhan ca ban va vat ly hat nhan img dung.
Phuang phap diing de nghien cuu la kich boat mau do va do hue xa gamma bang detector ban
Hoi nghi Khoa hgc ky niim 35 ndm Vien Khoa hoc vd Cong nghe Viet Nam - Hd Noi 10/2010
dan CO do phan giai nang lugng cao. Pho ke gamma dugc tu dgng hoa nha may tinh va cac phin mim chuyen dung. Phi gamma dugc luu trir va phan tfch bang may tfnh.
2.1 Nghien ciru vi sd lieu hat nhdn
2.1.1 Do tiit diin phdn ung ciia mdt sd ddng vi dung chum notron 14 Me V [1,2,3]
So lieu hat nhan dong vai tro quan trgng khong chi trong viec phat trien cac ly thuylt hat nhan ma con ca trong ung dung ky thuat hat nhan va nang lugng hat nhan. Viec do tiet dien phan ung hat nhan gay bai chiim notron nang lugng 14 MeV dugc trien khai tai Trung tam Vat ly Hat nhan ngay tir nhung nam 1980 sir dung ky thuat do kich boat. Ky thuat nay c6 uu diem la dan gian, cho do nhay cao, de dang phan biet dugc cac kenh phan ung (n,x) va (n,n'x) do cac kenh nay tao ra cac san pham khac nhau sau khi hat nhan bi kich boat. Tiet dien phan ung hat nhan dugc do bang phuang phap tuong doi de loai bo cac hieu chinh phiic tap nham tang do chinh xac den mirc cao nhat. De tai nghien cuu "Do va phan tfch tilt dien notron a viing 14 MeV" da dugc IAEA tai trg. De tai nay da thuc hien viec do tiet dien cac phan ling (n,p), (n,n'p) va ( n , a ) tren cac dong vi ben Cr va Ti. So lieu cua cac nghien cuu nay da dugc IAEA dua vao trong tuyen tap so lieu chung.
2.1.2 Do ti sd tiit dien isomer [4,5]
Viec do ti so isomer se cho chiing ta biet nhieu thong tin khong chi ve cau triic mirc nang lugng cua hat nhan ma ca ve ca che cua phan iing hat nhan da tham gia vao viec tao mirc isomer. Ti so tiet dien isomer duac dinh nghia la ti so /? = cr / cr , trong do cr la tiet dien tao thanh mirc isomer con a^ la tiet dien tao thanh hat nhan a muc ca ban.
Viec do ti so tiet dien isomer cung la huang nghien cuu truyen thong truac day tai Trung tam Vat ly Hat nhan sir dung chiim notron 14 MeV thong qua phan ung (n,2n) va chiim hue xa ham thong qua phan img {y, n). Nhirng nghien cuu nay da dugc thuc hien tren cac dong vi Nd, Sm va Pd thong qua cac phan ung hat nhan sau day : ''*^Nd(n,2n)''"'"'°Nd, '''Nd(;',n)''""'SNd, '''Sm(n,2n)''''"'^Sm, '''^m{y ,n)''^"''^Sm, "'Pd(n,2n)'°''"'^Pd va
"°Pd(;^,n)'«^'"'^Pd.
2.1.3 Ddnh gid sd lieu hgt nhdn [6,7]
Viec danh gia cac so lieu hat nhan nham dua ra cac mo hinh ban thuc nghiem dong vai tro quan trgng vi no cho phep tfnh dugc cac gia tri chua do hoac khong do dugc bang thuc nghiem. Vi vay, mgt huang nghien ciru ciing dugc trien khai tai Trung tam Vat ly Hat nhan la thu thap cac so lieu hat nhan da cong bo va phan tich chiing nham dua ra cac mo hinh ban thuc nghiem. Chang ban, khi phan tich tiet dien cac phan ung hat nhan (n,p) trong viing 14 MeV, chiing toi da tim ra dugc cac cong thiic ban thuc nghiem mo ta sir phu thugc ciia tiet dien vao cac dai lugng vat ly khac nhu :
Lg{a^„^;) = a,+a,N + a^Z + a,{N-Z)IA"'+a,B„+a,B^
Trong d6 N va Z tuong irng la so notron va so proton cua hat nhan, Bn va Bp tuang ling la nang lugng lien ket ciia notron va proton trong hat nhan tinh theo MeV, con cac tham so ao, ai, a2, a^, a^ va a^ la cac tham so ban thuc nghiem.
Vai cac phan img hat nhan (n,2n) trong viing 14 MeV, chiing toi cung dua ra mo hinh ban thuc nghiem nhu sau :
Tiiu ban: .Nghiin cthi ca ban trong ITnh virc Todn, Ly ISBN: 978-604-913-009-0
(^(n.2n,["^b] = a^\r, + r, - — ^ + ;•,V + r.Z + r,B„ + r,B^ + r^E, N-Z
Trong do cac tham so ro, ri, X2, rs, r4, r, va X(, la cac tham so thuc nghiem. Dai lugng (j^ ={A^'^ +\)- la tilt dien hap thu notron.
2.2 Nghien cuu ve phdn hach hat nhdn [8,9,10]
Huang nghien curu phan img quang hat nhan ciing la mgt huang nghien cim truyen thing ciia Trung tam Vat ly Hat nhan. Muc tieu chinh ciia cac nghien cuu theo huong nay la phan b l cua khoi lugng va dien tich ciia cac manh phan bach. Phan bo khoi thu dugc tir iec do xac suit tich liiy tao thanh cac manh phan bach con phan bo dien tich thu dugc tir cac xac suat tao thanh timg manh phan bach. Phuang phap thuc nghiem la mau chira dong vi phan bach
^^^U hoac ^^^Th dugc chieu bang chiim biic xa ham. Khi do se xay ra hien tugng phan bach vai viec tao thanh ciing mgt luc rat nhieu dong vi co so A va Z khac nhau. Nhirng dong vi nay deu a trang thai kich thich va se phat ra hire xa y. Bang each do pho nang lugng cua cac hire xa y nay se xay dung dugc cac phan bo khoi lugng va dien tich cua cac manh phan hach.
3. Cac huoTig nghien cuu dua tren hop tac quoc te
Nhirng thi nghiem vat ly hat nhan hien dai ngay cang tra len rat dat tien do tinh phirc tap. Chiing doi hoi nhimg to hgp thiet hi dat gia bao gom cac may gia toe manh, cac he ghi do hat tinh vi va cac sieu may tinh de phan tich so lieu. De co the duy tri cac huong nghien cim trong ITnh vuc vat ly hat nhan hien dai cap nhat vai trinh do quoc te, cac can bg ciia Trung tam da no lire tim kiem cac hgp tac. Den nay Trung tam da thiet lap dugc nhirng quan he khoa hgc chat che vai cac vien nghien ciin manh ve vat ly hat nhan tren the giai nhu : Vien Vat ly va H6a hgc RIKEN, Trung tam Nghien cuu Hat nhan cua Dai hgc Tong hgp Tokyo (Nhat Ban), Vien Lien hgp Nghien cim Hat nhan Dupna (Nga), Trung tam gia tic Pohang (Han QuIc), Vien Nghien cim Hat nhan ORSAY va Trung tam nghien cim ion nang GANIL (Phap),...Cac huong nghien cim vat ly hat nhan ca ban dua tren hgp tac quIc t l bao gim :
a) Nghien cim phan ung quang hat nhan diing chiim hire xa ham co nang lugng thip tao ra tir cac may gia toe electron nhu MT-17 va MT-25. Nang lugng cue dai ciia chiim hire xa ham la 17 MeV va 25 MeV. Huong nghien cim nay dua tren hgp tac vai Vien Dupna [11,12,13].
b) Nghien cuu cac phan img quang hat nhan gay bai chiim buc xa ham nang lugng cao tao gia tir may gia toe proton nang lugng cao. Nang lugng cue dai cua hire xa ham la 70 MeV.
Huong nghien cuu nay dua vao hgp tac vai Vien Pohang (Han QuIc) [14,15,16].
c) Nghien cim cau true ciia cac hat nhan giau proton hoac giau notron nim xa duang ben gay bai chiim hat nhan phong xa. Cac phan irng hien nay dang tap trung nghien cim la cac phan img ma thien van hgc quan tam. Cac nghien cuu nay dua vao hgp tac vai Vien nghien cim Vat ly va Hoa hgc RIKEN, Trung tam Nghien cuu Hat nhan cua Dai hgc Ting hgp Tokyo, Vien Vat ly Hat nhan (ORSAY) va Trung tam gia tic ion nang GANIL [17,18,19,20].
d) Nghien cim ly thuyet cau triic ciia cac hat nhan la dua vao bgp tac vai cac Vien nghien cim quoc te. LTnh vuc nghien cuu cu the la tinh toan mat do miic va nghien cim tinh chat nhiet dgng hgc cua eae hat nhan nong dua vao ly thuyet Bardeen-Cooper-Schrieffer (BCS) va ly thuyet xap xi pha ngau nhien gia hat (SCQRPA). Nhieu tinh chat nhiet dgng hgc mai da thu dugc nhu khe tao cap, nang lugng tu do, nang lugng toan phan, nhiet dung va
Hoi nghi Khoa hoc ky- niem 35 ndm I 'iin Khoa hoc vd Cong nghe Viet Nam - Hd Noi 10 2010
entropy, mat do mirc. Day la ITnh vuc da va dang dugc quan tam ca ve ly thuyet lan thuc nghiem. Kit qua nghien cim da dugc so sanh vai so lieu thuc nghiem [21,22,23,24.25].
Tren ca sa cac hgp tac quoc te. can bg ciia Trung tam thuang xuyen den cac vien nghien cim dii tac dl thuc hien cac thi nghiem khoa hgc va so lieu sau do dugc phan tich mgt phan a nuac ngoai va mgt phan phan tfch tai Trung tam. Ciing vai cac doi tac nuac ngoai, cac can bg ciia Trung tam da cong bo nhieu bai bao dang tren cac tap chi quoc te \'a trong nuoc co uy tin ve vat ly hat nhan.
4. Nghien cihi irng dung [26,27,28,29,30].
Vat ly hat nhan tir lau da dugc img dung rgng rai trong cac ITnh vuc khac nhau ciia nen kinh te. Chang han nhu phan tich ham lugng dong vi la mgt trong nhiing nhu cau quan trgng trong bat ky nen kinh te nao. Phan tich kich boat la mgt trong nhirng phuong phap truyen thong va co rat nhieu uu the so vai cac phuong phap phan ticb khac. Tai Trung tam Vat ly Hat nhan da trien khai huong phan tich kich boat diing chiim notron va chiim birc xa ham ngay tir khi cac thiet hi nay dua vao hoat dgng. Quy trinh phan tich kich boat cho hang loat cac nguyen to vai cac doi tugng mau khac nhau da dugc xay dung. Cac quy trinh nay da dugc diing de phan tich rat nhieu mau dia chat, sinh hgc,...
Phan tich cac dong vi phong xa tu nhien dua tren viec do pho / ciia cac mau bang pho ke phan giai cao diing detector ban dan ciing dugc trien khai. Quy trinh phan tich cac dong vi phong xa tu nhien da dugc nghien cim va kiem nghiem tren cac mau chuan khac hau cho do tin cay cao. Tmng tam da ky mgt so hgp dong vai nhung co sa co nhu cau phan tich cac dong vi ph6ng xa tu nhien va ket qua phan tich tai Trung tam dugc cac ca sa img dung danh gia cao.
Phan tich huynh quang tia-X la phucmg phap phan tich nhanh, dong thai xac dinh dugc nhieu nguyen to va quan trgng hon ca la khong pha buy mau. Tai Trung tam Vat ly Hat nhan, da xay dung cac quy trinh phan tich huynh quang tia-X tren nguon dong vi ph6ng xa
^'"Am de phan tieh cac mau dia chat. Quy trinh nay cung dugc ung dung de xac dinh tuoi vang ta va vang tay.
5. Tham gia giang day dai hoc va sau dai hoc tai Trung tam Vat ly Hat nhan
Ngoai cong viec nghien cim khoa hpc, Trung tam Vat ly Hat nhan da tich cue tham gia dao tao can bg a trinh do dai hgc va sau dai hgc. Hang nam, bg mon vat ly hat nhan ciia Truang cao hgc thugc Vien Vat ly da va dang dao tao nhieu thac sT va tien sT. Ngoai viec dam nhiem giang day tai truang cao hgc vat ly cua Vien Vat ly, cac can bg cua Trung tam han nam lien tuc dugc mai den giang bai cho sinh vien dai hgc va sau dai hgc ciia cac truang : Dai hgc Khoa hgc Tu nhien, Dai hgc Cong nghe thugc Dai hgc Quoc gia Ha Ngi, Dai hgc Su Pham Ha Ngi, Dai hgc Bach Khoa Ha Ngi va Dai hgc Khoa hgc Tu nhien thugc truang Dao hgc Quoc gia Thanh pho Ho Chi Minh, Dai hgc Su pham Thanh pho Ho Chi Minh.
6. Phuong huong hoat dong cua Trung tam trong thoi gian toi
Trong nhung nam tiep theo, Trung tam Vat ly Hat nhan tiep tuc phat huy the manh ve nghien cim vat ly hat nhan ca ban tren may gia tic dua vao cac hgp tac quoc te va ly thuyet hat nhan. Tmng tam ciing se tich cue tham gia cac chuang trinh nghien cim phuc vu cho dien nguyen tir nhu : nghien cim vat ly notron, an toan hue xa, ghi nhan birc xa,... Trung tam se triln
Tiiu ban: Nghien cim ca ban trong ITnh virc Todn, Ly ISBN: 978-604-913-009-0
khai cac dl tai ciia vat ly hat nhan img dung trong cac linh vuc : phan tich khong pha buy bing cac phuang phap hat nhan cho cac doi tugng mau khac nhau nhu : dia chit, sinh hgc, vat lieu, bao tin, bao tang, kiem tra va danh dau cac co vat, cac san pham van boa quy,... Trung tam chu truang diy manh hgp tac vai sa khoa hgc cong nghe ciia cac tinh de nghien cuu img dimg cong nghe hat nhan trong cac ITnh -vuc khac nhau ciia nen kinh te nhu : dieu tra phong xa, phan tich nguyen tl, kilm tra khong pha buy mau bang cac phuong phap vat ly hat nhan, ung dung ky thuat hat nhan cho dieu tra nong hoa tho nhuong, nuac ngam, do di dap nuac,... Ngoai ra, huang vl khai thac cac may gia toe hien c6 a trong nuac ciing se dugc chii trgng.
7. Mot vai kien nghi
Mgt kh6 khan Ion cua Trung tam Vat ly Hat nhan la thieu trang thiet bi. De nghien ciiu hat nhan, cin co cac thiet bi Ion nhu may gia toe, 16 phan ung hat nhan va cac thiet hi do dac phong xa.. Hien nay, may phat notron NA-3C da hi hong tir lau. May gia toe Microtron MT-17 da qua lac hau can dugc thay the. Trung tam Vat ly Hat nhan mong muon se dugc trang hi mgt may gia toe cyclotron rfiai va mgt nguon notron dong vi co cuong do cao de c6 the trien khai cac huong nghien ciiu dung chiim hat tieh dien va chiim notron. Ngoai ra, cac thiet hi nay ciing se dugc diing de phuc vu cho viec dao tao nhan lire hat nhan a trinh do cao.
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