MUC LUC Trang phu bia | L5i cam ofn Lofi cam doan Muc luc Cac chG vi6't tat Trang M OAU CHUONGL NGUON PHAT TLF TRUDNG XUNG CAO VA CO S6 THIET KE CUPN NAM CHAM 1.1 Cac ngu6n tir trucrng tren the gidi 1.2 H6 tir trudng xung va cac thOng so ban dau 1.3 Co SOT v^t ly li^n quan den phat tir trucrng xung cao 12 1.4 Bai toan thi^'t ka'cudn day nam cham 1.4.1 Anh huang cua dang hlnh hoc cuOn day nam cham 1.4.2 Anh hucrng cua nhi6t do xung dong dien chay qua 16 17 19 1.4.3 Anh hirong cua ap sua't tir len cu5n day nam cham 1.5 Ket luan chuofng CHlfONG 22 33 DIEU KHIEN NAP VA PHONG DIEN TRONG NGUON PHATTLfTRUdNG XUNG CAO 35 2.1 Vong didu khien tu dong 37 2.2 Didu khiln di6n tu" va ghep n6i may tinh 39 2.3 Mach di6u khi^n SCR vdi tai cam cam khang 39 2.3.1 Su tri cua dong dien qua tai cam khang 40 "2.3.2 Dong qua d6 qua tai cam khang 41 2.4 Chuyen mach Thyristor c6ng sua't \6n 41 2.5 Bo tu dien 42 2.6 Ket luan chuong 43 CHUONG THUTHAPVAXLTLYTINHIEU TRONG HE TLf TRUdNG XUNG CAO 3.1 H6 cu6n pick-up 44 44 3.1.1 Phuongphap cam ung 44 3.1.2 Dae trung tan so 47 3.1.3 Anh huomg ciia nhi6t dO d6'n dac tinh cu6n pick-up 48 3.1.4 Anh huong ciaa cac th6ng s5' cu6n pick-up va hinh dang mSu den th6' 16i cua sensor 3.1.5 Cac loai cu6n day pick-up 3.2 He dien tu thu thap va xir ly tin hieu 49 52 55 3.2.1 CSu bu trijr va b6 ti^n khud'ch dai vi sai 56 3.2.2 Bo tich phan dien tu 57 3.2.3 Ba vi phan dien tu 58 3.2.4 Cac b6 bie'n d6i A/D va b6 nh6 s6 lifu RAM 58 3.3 Thu thap va xu ly s5' li6u bang ghep n6'i may tinh 59 3.4 Ke't luan chuang 59 CHlfONG THL/C NGHIEM XAY DL/NG HE TLf KETCfTRl/dNG XUNG CAO 61 4.1 Che tao cuOn nam cham 61 4.2 Xay dung khoi nap va phong dien 70 4.2.1 Mach didn cha'p hanh 70 4.2.2 Mach di6n cac rcf-le va bien thd'cao ap cOng sua't 16n 71 4.2.3 Thyristor va mach tao xung m6i 75 4.2.4 Cac dien trof cCng sua't lorn va b6 tu di6n 78 4.2.5 Mach I6gic di6u khien 80 4.3 xay dung thu thap va xu ly s6' Heu 95 4.3.1 Che tao cuOn day pick-up 95 4.3.2 Cac mach dien tu thu thap va xu ly tin hidu 99 4.3.3 Ghep n5'i he v6\ may vi tinh qua chudn GPIB va phSn m6m xu ly so lieu 106 4.3,4 Chu^n dO he va cac thao luan 113 4.4 Ket luan chuang 117 CHlfONG QNG DUNG HE TL/ KE TLf T R U N G XUNG TRONG NGHIEN CLfU VAT LIEU TLf 5.1 M6t s6'ke't qua su phu thu6c cua ti^ dO vao tir trucrng 119 120 5.1.1 Do tir d6 tren m^u b5t dinh huomg 120 5.1.2 Cac phep ti^ tren mau b6t rdi 121 5.1.3 Xac dinh hieu ung tijf nhiet cua mSu kh6'i cac hgp cha't Gd5(Ge,.,Si,) 5.2 Do \.\x trudng di hu6ng bang phuang phap SPD 127 129 5.2.1 Phuang phap SPD 129 5^2,2 Thuc nghiem dac 130 5.2.3 Xir ly s5'tin hieu phep SPD 131 5.3 5.4 Do ducmg cong xh trS ciia cac nam cham Ke't luan chuang KET LUAN Cac c6ng trinh lien quan de'n de tai Luan an Tai lieu tham kliao Phu luc 136 141 142 D A N H M U C C A C C H O VIJ^T T A T Chuf viet tat Tieng Anh Tieng Viet A/D Analog to Digital conversion Bien d6i tuang tu s5' AC Alternating Current Dong dien xoay chieu DC Direct Current Dong dien mdt chieu DIV Division D6 chia FOMP First Oder Magnetization Process Xir ly ti^ bac mot IPS In-phase Signal Tin hieu d6ng pha ISA Industrial Standard Architecture Kien true chudn cong nghiep OPTRON Chip dieu khien phan each quang OSC Oscilloscope PID Propotional-Integral-Derivative Control Dieu khi^n kieu ty le - tich Dao dOng ky phan-vi phan PIT Programmable Interval Timer Chip dinh thcri kha trinh PPI Programmable Peripheral Interface Chip ghep n6i ngoai vi kha trinh PSS Phase-shift signal Tin hieu c6 dich pha RAM Random Access Memory Bo nh6 ghi/doc dugc SCR Solid-state Conntrolled Rectifier Cai chinh luu c6 dieu khien bang mach ran (dugc che' tao bang vat lieu ban dSn) SPD Singular-point detection Ky thuat phat hien di^m di thudng, SQUID Superconducting Quantum Thie't bi giao thoa lugng tu Interferer Device sieu dSn UIB Universal Interface Board Ban mach ghep nO'i da nang VSM Vibrating Sample Magnetometer Tu ke' mSu rung FTiKR mil ^Au J hue nghiem tiJf trucrng cao mang lai nhieu thdng tin quan ve tinh cha't vat ly cua cac vat lieu Thuc vay, ttf trudng c6 dO lofn so sanh dugc v6i gia tri cua tru&ng trao d6i hoac trucrng tinh th^ dSn de'n pha v5 ca'u true tir cua cac phan mang tuf cac vat lieu hgp cha't lien kim loai, Cac chuyen pha tiir gia ben tach cac phan vung vdi spin "up" va "down" c6 the thuc hien vdi tir trucrng du Idfn Cac hieu iJng lai vijng nang lugng ciia cac vat lieu chufa Uran dSn de'n di hucfng tii khong 16 chi c6 the dugc phat hien v6i cac phep thuc hien tai tir trucrng cao Cac chuyen pha tiif trang thai femion nang hoac trang thai sieu dSn sang trang thai thucmg cung c6 the dugc gay bdi tur trucrng ngoai 16n han nhieu Idn tijr trucrng thudng diing cac phong thi nghiem Ngay ca cac nghien cuu gdn lien vdri ling dung ciia cac "sieu nam cham" che' tao bang cac vat lieu ivc cung chua da't hiem cung can CO tijf trucrng ra't Idn di nap tir cac nam cham hoac d^ dat dugc mot ducrng tir trS dSy du ciia chung So v6i tir trudng trai da't {5.10'^ Tesla) va ti^ trucrng cua cac nam cham thong thucmg phong thi nghiem {0,1 - Tesla) thi cac ngu6n tijr trucrng v6i cucmg han 10 Tesla dugc coi la ngu6n tiif trucrng cao [47] De tao cac ngu6n rw" trudng tinh c6 d6 \dn tren 10 Tesla cSn phai c6 cac phuang tien phiic tap va dat gia Thi du, ne'u dung phuang phap Bitter phai tao nhutig he di^u khi^n ngu6n dien c6 nang lugng hang MJ va c6ng sua't len i6i hang MW ciing cuon day nam cham kh6ng 16 dugc lam lanh dac biet bang he cap nude ap sua't cao Ne'u dirng phuang phap cu6n day sieu dSn phai c6 he ca'p He-li long Trong ca hai trucrng hgp tren, ngudi ta chi tao dugc cac tijf trudng tinh cue dai tren dudi 20 Tesla Phuang phap tao cac tit trudng xung, thi du dua tren nguyen tac nap dien cho bo tu dien nang lugng Idn r6i phong dien ra't nhanh qua cudn day nam cham dien cam, cho phep tranh dugc nhung dSu tu dat gia neu tren ma lai tao dugc cac xung tir trudng c6 bien d6 len tdi hang tram Tesla Do vay, ca b cac nude tien tien hien deu c6 xay dung cac trung tam nghien ciJu s\s dung tiJf trudng xung cao , Vdi kha nang kinh te' ciia cac phong thi nghiem d Viet nam hien chua cho phep xay dung dugc cac ngu6n tir trudng cao theo kieu tir trudng tinh, do yeu cSu nghien cihi cac vat lieu tijr hien dai, cSn c6 nhiJng ngu6n tijf trudng cao nhu vay Chinh ky thuat xung cd th^ dap u:ng dugc yeu cdu dugc dijng de tao cac xung tir trudng c6 bien dd tren 10 Tesla nhung khoang thdi gian t6n tai chi cd mili giay de'n giay R6 rang vdi m6t he tit trudng xung nhu vay thi bien d6 xung \.\x trudng van dat dugc rat Idn nang lugng chi cSn ca vai chuc KJ va dd ve mat kinh te' cac he tuf trudng xung c6 gia cha'p nhan dugc ddi vdi nude ta Hien c6 phuang phap tao cac tit trudng xung cao, dd la phuang phap pha huy (destructive) va phuang phdp khong pha huy (non-destructive) Phuang phap pha huy dijng d^ tao cac ngu6n ti^ trudng xung cao han 100 Tesla mot khdng gian CO cac dudng sure tir bi nen lai mdt cii n6; thdi gian t6n tai xung chi ca micrd giay trudc vach ngan khdng gian va cac vat ben bi vu n6 pha huy hoan toan Phuang phap khdng pha huy dirng mot ddng dien Idn phong qua cac cuOn dien cam nham tao ben loi ciia chung mdt tiJf trudng xung cao cd gia tri nho hem 100 Tesla Cac cudn nam cham g6m mdt vdng hoac nhieu vdng, dugc sir dung nhieu ISn va cho cac xung tijf trudng dai tir vai mili giay de'n hang giay Muc dich cua ban Luan an la nham xay dung dugc mot he tit ke tic trudng xung cao din tien tai Viet nam He phai phuc vu dugc cho cdng tac nghien cuu va dao tao tai cac trudng Dai hoc, cac Trung tam nghien curu linh vuc khoa hoc cdng nghe \i vat lieu tijf hien dai Noi dung va phuong phap nghien cihi: Luan an dugc tien hanh bang cac phuang phap nghien cuu thuc nghiem Luan an g6m cac ndi dung sau: T6ng quan cac nghien ciJu ly thuye't va thuc nghiem tren the' gidi tai nhOng va'n de lien quan de'n viec phat v^ dac cac thdng s6 ciia vat lieu tijf d tijf trudng cao Thie't ke' va xay dung mdt he tij: ke' i\x trudng xung cao, day la he d5u tien thudc loai d Viet nam He g6m khd'i; (a) Khdi phdt tit trudng xung dugc xay dung bang phuang phap napphong qua bd tu dien Khd'i dugc dieu khien tu ddng bang dien tir va ky thuat ghep nd'i vi tfnh Cac xung tijf trudng cd gia tri cue dai tren 20 Tesla, dd dai xung tit de'n tren 30 mili giay, ddng nha't mdt viing tai d'ng day c6 dudng kinh de'n 25 mm (b) Khdi cdc thdng sd vat ly ciia cac vat lieu tijf (dugc dat tijf trudng nay) bang cac phuang phap thu thap, xir ly tin hieu tuang tu va sd' ke't hgp vdi ky thuat ghep nd'i may vi tinh Cac thie't ke' ve phSn cufng va phSn mem dugc tien hanh tai Khoa Vat ly trudng Dai hgc Khoa hoc tu nhien - Dai hoe Qud'c gia Ha noi (DHKHTNDHQGHN), tai Vien Vat ly thuc nghiem - Dai hoc Tong hgp Ky thuat Vien (Cdng hoa Ao) va tai Trung tam Qud'c te' Dao tao ve Khoa hoc vat lieu (ITIMS) Cac linh kien va vat lieu quan trong he dugc nhap ngoai hoac dugc che' tao nude theo mfiu thiet ke' ciia tac gia va nhdm nghien ciiu He dugc che' tao, lap rap, dac kiem tra tai Phdng thi nghiem Tijf trudng xung cao - Trung tam ITIMS Do thir cac he mSu vat lieu tijf, dac biet la cac lien kim loai dat hiem - kim loai chuyen tiep bang cac phep khac nham khang dinh cac tinh nang ciia he tir ke' tij: trudng xung cao da dugc xay dung Cac mSu dugc che' tao va kiem tra bang cac phuang phap lien quan khac tai Khoa vat ly, DHKHTN-DHQGHN; Dai hgc Tdng hgp ky thuat Vien; Trung tam ITIMS; Trung tam Khoa hoc tu nhien va Cdng nghe Qud'c gia, Dai hoc Tong hgp Birmingham (Anh) va Dai hoc Tong hgp Amsterdam (Ha Ian) • Bd' cue ciia Luan an bao g6m chucmg, dd: Chuang la phSn tong quan ve cac ngu6n phat tir trudng cao va ti^ trudng xung cao; nhirng va'n di tinh toan ly thuyet cung nhu thuc nghiem che tao cudn nam cham da dugc khao sat lam tiln d6 cho viec xay dung chuang trinh thie't ke' tdi uu hoa cudn day Chuang va de cap tdi cac bai toan thie't ke' he dilu khien nap-phdng dien klid'i phat xung tijf trudng cao va he thu thap xir ly tin hieu khdi cac thdng sd' vat ly ciia vat lieu tijf dat ti^ trudng dd Chuang trinh bay cac thuc nghiem da dugc tie'n hanh xay dung he tii trudng xung cao Thdng sd, chi tieu ky thuat ciia cac bd phan he sau lap rap da dugc dac cung nhu cac van de chu^n dd tir trudng va tir dd da dugc bao cao Ndi dung ciia chuang la thuc nghiem dac cac mau vat lieu tir da dugc tie'n hanh tren he tij ke' tijr trudng xung cao nham kiem tra va khang dinh tinh diing dan va tin cay ciia he do, Cac phuang phap do, ke't qua va thao luan cho cac phep dac da dugc trinh bay CHlfONG NGUON PHAT TLf TRLTONG XUNG CAO VA CO S6 THIET KE CUON NAM CHAM Mot he tiJC keh& ky d6u bao g6m khO'i: kh6'i phat tut trucrng va khd'i lucmg cac thdng s6' cua vat heu dat tir trucmg nhu so d6 khd'i hinh , Khoi phat tCr trudng hoa nang tich luy luong nang lUdng Bo cam bien —> thu thap va XLf ly so lieu Buong chifa mau dat vung tCr trudng Hinh LI Sa d6 chung cua m6t tir ke' Kh6'i phat tiif truing g6m cac ca ca'u di6u khien qua trinh tich luy va chuyen hoa cac ngu6n nang lugng (thi du nhu nang lugng ngu6n dien ph6', nang lugng mdt vu nd sinh ) nang lugng tir c6 d5 Idn cSn thiet mOt khOng gian CO th^ tich xac dinh, MSu vat lieu dugc dat kh6ng gian Khoi g6m cac cam bie'n c6 nhiem vu bie'n d6i cac th6ng s6' c^n cua mSu (thi du nhu tir d5) cac tin hieu dien ty le r6i dua vao b6 thu thap xu ly tin hieu Trong cac tir ke' hien dai hSu he't cac qua trinh dieu khien va luc^ng ke tren deu dugc xir ly bang may tinh qua cac chuong trinh phSn mem Cac tin hieu thudng dugc so hoa va dugc xir ly s6 nham nang cao d5 tin cay va tfnh linh hoat cua he V6\ cac tir ke dac b dai \.\i trucrng tha'p va cue tha'p nhu tijf ke' xoan, tijf ke' mau rung, ti^ ke' giao thoa lugng tu sieu dan SQUID v.v doi hoi c6 nhung ngu6n phat tir trucmg tinh ra't 6n dinh va cac thie't bi cue nhay Trong cac tijf ke' tijr trucmg cao nhu tii ketic trudng xung cao lai cSn phai tao dugc nhirng xung dong dien cue lorn va thie't bi phai dam bao thu thap va xiT ly dugc cac th6ng s6 cua he mot thcri gian t6n tai xung ra't ngan Do dai phat tijf trucmg tu nhien va nhan tao de'n trai ra't r5ng, nhu se noi du6i day, nen viec nghien cu:u thie't ke' mOt he tir ke' cu the phai xua't phat tijf nhung yeu cSu cu th^ ciia cac nghien cu:u vat lieu ti^ c6 tinh de'n cac dinh hudng ve mat ly thuye't Do nhGng linh kien va phuang tien xay dung he ra't dat nen dieu kien kinh te' ciia m6i phong thf nghiem, m6i qu6'c gia cung la m5t nhan t5' quan phai tfnh de'n m6t chie'n luge c6 the mof r6ng tfnh nang ky thuat cua he tuang lai Dudi day se diim l^n lugt tijfng khia canh v^ mat ly thuye't lien quan de'n viec thie't ke' m6t ngu6n phat i\X trucmg xung cao cho he tijr ke' 1.1 CAC N G U N TIJ TRUCJNG TRfiN THE GICJI GiO'ng nhu nhiet dO va ap sua't, ti^ trucmg la m6t cac thOng s6 ca ban dugc dirng d^ thay d6i trang thai vat ly ciia vat lieu Viec ma rOng dai bie'n doi ciia tir tru6ng tac dOng len d6'i tugng nghien cuu se dSn t6i cac phat minh mdi va da dong gop nhieu cho cac hieu bie't ca ban vat ly cha't ran Cac ngu6n phat tij" trucmg CO sSn tu nhien va nhan tao Hinh la biJc tranh ve Idn ciia cac nguon tCf trudng dai tir lO"''* den 10^ Tesla [14] Cac ngu6n ti^ trudng nhan tao dung cho nghien ciJu vat lieu tij* cd the dugc phan cac ngudn tijf trudng tinh, gia tinh va tijf trudng xung a Tit trudng tinh: g6m cac loai sau - Cdc nam cham dien mot chieu: la cac cudn day dien cam cd loi sat hoac hgp kim sat Nhung nam cham dien Idn nhu b Bellevue (Phap) cd tir trudng ca 4,3 Tesla, nang 120 ta'n, tieu thu cdng suat 93 KW [14] Nhirng nam cham loai cac phdng thi nghiem nghien curu vat lieu tir dugc thay the' dSn bang nam cham cd cudn day sieu dSn vdi kfch thudc va lugng nho han - Nam cham sieu dan: cudn day nam cham dugc che tao bang cac vat lieu cd tfnh sieu dan tai cac nhiet tren 4,2K tdi 77K cung nhu cd tir trudng tdi han vugt qua 10 T ISThd cd mat ddng dien cao nen da xua't hien nhung nam cham sieu dan tren thi trudng cd ti^ trudng len tdi 20 T - Nam cham Bitter: Cudn day ciia nhirng nam cham la nhung dia dong mdng tach biet cd cac Id trdn ban kinh khac dugc ep vdi Ca'u true nhu vay cho phep lam lam lanh dugc nam cham cd ddng dien Idn chay qua Mot 37 kfch thudc khac vl nguydn tdc se khdng iriing hoan toan mac dii da bd chfnh trudng khu tir theo nhu cdng thiic (5.7) Nakagawa va cac tac gia [29] sir dung ngudn tir trudng tinh la cudn day nam cham dugc lam lanh bdng nude cd nang lugng cao vdi tiir trudng tdi I5T, da dua mdt dudng cong bilu didn su phu thudc cua hd sd 1.0 D khir tir D theo ty sd ty sd chilu dai L tren dudng 0,8 kfnh d cua cac mdu hinh tru (hinh 5.19) Cac tac 0.6 gia cung ddn tdi ket luan la: su bo chfnh hoan 0.4- toan chfnh xac trudng khir tiJ cho cac mdu dang la khdng thi dugc Tuy nhien vdi mdt sai sd 0.2 0.0 cho phep cd thi sir dung mdt he sd khir tir trung 0.0 0.5 1.0 1.5 2.0 2.5 3.0 Qii^u d^i/due^ngkinh [L/d] binh ling vdi mdi kfch thudc mdu Cac xung tii trudng cudn nam cham tao ^ ' " ' ' ^'^^ ^^P^M thudc cua he sd khir tir D vao ty sd' L/d he tir trudng xung co dang mdt chu ky hinh sin dai 32 mili giay (xem hinh 4.9a) Do vay ta co thi nhan dirge mdt dudng cong tir trd cac thdng sd ciia nam cham nhu dd tir du M^ , luc khang tir H^ cOng nhu tfch nang lugng BH,„^,^ dugc xac djnh Thuc nghiem dugc tieii hanh tren mdu nam cham Nd-Fe-B da thieu ket va xir ly nhiet Mdu da dugc che' tao va cac thdng sd bang phuang phap chudn cdng nghiep mach tir kfn tai phdng thf nghiem vat lieu tir Dai hgc Tdng hgp Birmingham (Anh) Khi tren he tir trudng xung vdi mach tir hd, vat lieu dugc cdt cac mdu hinh trii cd chilu dai L, dudng kfnh day d nhdm khao sat su phu thudc ciia he sd khir tir vao ty sd Lid Cac mdu dugc dat cho true ciia chiing triing theo phuang tir hoa ciia cudn nam cham Kfch thudc cac mdu dugc chi trdn bang 5.2 [49] Bdng 5.2 Kfch thudc cac mdu hinh tru Nd-Fe-B sir dung cho phep TT Ten mlu Chieu dai L (mm) Di/dng kfnh day (mm) Ty so L/d SH-1 0,4 SH-2 0.8 SH-3 10 2,0 38 Cudn tir trudng dugc dat d mdt vi trf dii xa mdu de tranh anh hudng ciia mdu de'n ke't qua tir trUdng ngoai Vi cac xung tir trudng la hinh sin tdt dan cd bien ciia ban chu ky duang Idn hon ciia ban chu ky am (hinh 5.20a) ndn dl dam bao c6 mdt dudng cong ttr trd ddy dii d ca hai chilu bien thien ciia tir trudng, gia trj cue dai cua xung tir trudng d ban ky duang phai dat cao han miic cdn thiet Hinh 5.20a cho tha'y mudn cd mdt dudng cong tir trd khoang T cua nam cham loai cdn phai dat mdt tir trudng ngoai cd i T va vay xung duang ciia trudng dd phai cd gdn r d nhiet dd phong Tren hinh 5.20b la dudng cong nhan dugc tai cac gdc phdn tu tir thu: nhat de'n thii ba sau xung tir -2*4 -16 0.8 -30 -20 -10 trudng ddu tien tren hinh 5.20a Ne'u bdn tie'p cii xung nira, ta se fjinh5.20 0 0.8 1.0 1.6 2.4 2.0 3.0 3,2 4.0 4,8 (lO^Wm] 4,0 5.0 60 [Teslal Xung tir trudng ban ky (a) va nhan dugc mdt dudng cong khep dudng cong tir tri ciia nam cham NdFeB nhan dugc kfn xua't phat va ke't thiic tai diim phep tir truang xung (b) Ph.1n in dam la ^ f ket qua tuang I'mg vdi xung hinh a -MR vk doan tir hoa ban dau tu U de'n Ms se khdng tdn tai Cac dudng cong tir hoa thu dugc cac mdu cua vat lidu nam cham Nd-Fe-B kl trdn tai nhiet dd phong dugc ddn tren hinh 5.21 Dudng cong tir trd va khu tir tai gdc phdn tu thii hai dugc chi tren hinh 5.22 1.500 -1.500-i n 70 -l"0 00 1.0 2.0 3.0 [Tesla] -30 -2.4 -20 -1.6 39 B [kGauss] M[kOel B [kGauss) M(kOe) ,.""'"y 000- Ud =0,8 ,"' 000- -"M B.OOO6 000- B 4.0002 0000.000 •1 000- 8000 i r -5000 -2500 00 000- • •1 0008000 H[Oe] f 1 -5000.0 -2500 0.0 Hinh 5,22 Cac dudng cong khii tir M(H) va B(H) cung phdn tu thu hai ciia hai mdu c6 ty so' L/d khac Cac thdng sd dac trung cho vat lieu nam cham vinh ciru loai dugc liet kd bang bdn Hinh 5.23 la dudng cong khir tir va cac thdng sd ciia nd nhan dugc hd tir kfn tai Birmingham L/d = 0,4 L/d = 0.8 MR 11,5 + 0,05kG 11.1 +0,05kG Hdnl 7,15±0,5kOe 7,05±0,5kOe •^cind 6.77 ±0,5kOe 6,60±0,5kOe BH^a, 28,27 WiGOe 27.90 MGOe Hinh 5.23 Cac dudng cong khir tir ciia nam cham ciing cac thdng sd dugc tren he mach tir kfn tai Birmingham CGS Unit Remanence M R = 11.29 ±0.01 kG Intrinsic Coercivity Hcmt^ 7.42 ± 0.12 kOe Inductive Coercivity Hcind= 6.84 i 0.19 kOe BHmax =30.19 ± 0.84 MGOe So sanh cac kd't qua nhan dugc bdi phep trdn he tir trudng xung vdi dudng cong trdn mach tir kfn ta thdy: • Hlnh dang dudng cong sau sira trudng khir tir vdi he sd b6 chfnh D nhu tren la cha'p nhan dugc Sai lech tuang ddi cue dai ciia cac thdng sd so vdi kd't qua thu dugc hd tir kfn la nhu sau: 140 TiidUMR: 1,86% Luc khang tti ndi tai H,i„,: 4,98% Luc khang tir cam ling H^.,^^: 3,50% Tfch nang luong BH^g,: 7,58% Mdt mdu nam cham thudc loai Nd-Fe-B khac Trung qud'c che tao cung da dugc kilm tra bdng phuang phap mach tir hd tren he tir trudng xung Dudng cong tir trd va dudng cong khir tir tai gdc phdn tu thii hai dugc chi trdn hinh 5.24 M [10 IcOe] 11,000Bp:Gausg] 10,000- M [ k O o ] 8.000G.OOO4.000 2,000- 0,000 •1.000•18000 -10000 Hinh 5.24 Ke't qua nam cham Nd-Fe-B ciia Trung qud'c: a, dudng cong tir trd trudc va sau bl chfnh b, dudng cong khir tir sau bl chfnh Trong mdu nay, dudng cong khir tir khdng dugc tran tru (bj 16m) quy trinh xir ly nhidt ciia vat lieu chua dugc hoan hao Tuy nhien, nhin vao kd't qua sau bd chfnh trudng khir td ta thdy dudng cong co vudng gdc cao, phii hgp vdi tidu chudn ciia cac nam cham Nd-Fe-B thdng thudng Qua cac kd't qua trdn cd thi rut kd't luan so bd cho viec sir dung he tir trudng xung cho viec tir tri cua cac nam cham dat hiem nhu sau: Dang dudng cong tir tri dugc mang lai cac thdng tin him fch vl chdt lugng va che dd xir ly nhiet nam cham Viec bd chfnh dudng cong tir tri cho cac mdu hinh tru mdc phai mdt sai sd tfnh ba't ddng nha't ciia tir dd quy dinh bdi hinh dang va cdu triic cua mdu Tuy nhidn mdt chiJng mUc nhiing ling dung cdng nghidp cd thi cha'p nhan nhiing sai sd ndy vdi cac hd sd bd chfnh trudng khir tir da neu trdn 141 Cac kd't qua thue nghidm trdn chiing to rdng cd thi sir dung he tir trudng xung d l kilm tra cac thdng sd ciia nam cham ddt hie'm co luc khang tir vd tfch nang lugng cao, nha't la dilu kifn hien d nude ta chua cd nhung ngudn tir trudng tinh dii cao (thf du nhu nam cham sidu ddn) 5.4 K ^ T LUAN CHlfONG Mdt he dugc xay dung chi dugc cha'p nhan chirng minh dugc cac kd't qua thuc nghidm dugc tie'n hanh tren no la diing ddn Vi vay cac phep phuc vu true tie'p cho nghien cdu, ddng thdi dl kilm tra chfnh he da dugc thuc hien Do la cac phep su phu thudc ciia tir dd vao tir trudng tai cac nhiet khac Cac phep la phong phu vi cd thi dugc thuc hien khdng nhiing trdn cac mdu khdi ma cdn ca tren cac mdu bdt djnh hudng va mdu bdt rdi Cac kd't qua la phii hgp vdi nhiing cdng trinh da dugc cdng bd trudc tai cac hd tir trudng tinh cung nhu tir trudng xung khac trdn thd' gidi Mdt ke't qua dac sdc la vide xac djnh hidu ling tir nhidt khdng Id cua cac hgp chdt Gd^(Ge].,SiJ hd tir trudng xung la phii hgp vdi cac kd't qua trdn cac hd khac nhu hd phiic tap SQUID Phuang phap SPD nhdm xac djnh gia tri tir trudng dj hudng H^ ciia cac mdu da tinh thi da dugc tien hanh trdn hd tir trudng xung vdi su chii y tdi cac kha nang ke't hgp giua xir ly dien tir analog va xir ly sd la mdt chiing minh vl kha nang cua he phuang phap ling dung Vdi cac nam cham ddt hie'm co tfch nang lugng cao, he ciing cho phep xac dinh chfnh xac cac thdng sd luc khang tir ^Hc va ^Z/^; ridng vdi tfch nang lugng BH^^^^x > ^^^ phep tren he cho mdt sai sd cha'p nhan dugc cdng nghidp Qua mdt thdi gian lam vide kilm nghiem, ket qua ciia cac phep ling dung dugc thuc hien tren he td ketvt trudng xung cao chiing to he da lam vide mdt each chfnh xac cQng nhu tin cay va do hoan toan co thi phuc vu cho cac nghidn ciiu vat lidu tir 142 pi]te KET L a t e Cd the tdm luge cac ndi dung ma Luan an da thue hidn dugc nhu sau: Da tid'n hanh thid't kd' sa dd t6ng thi he tir ke tir trudng xung cao tren ca sd yeu cdu thuc te' cua Viet nam va phan tfch cac nghien cii-u ly thuye't cung nhu thuc nghidm thie't ke' che' tao ciia cac he da dugc cdng bd tren the' gidi Tren ca sd nghien cdu su anh hudng ciia nhan td: dgng hinh hgc cuon ddy, nhiet vk dp sua't tdtd'i dong dien chay qua cudn day va tfnh bin virng vl nhidt cQng nhu vl ca khf cua chiing; da dung phuong phap sd dl thid't kd' va chd' tao dugc cudn nam cham Hai cudn day co dudng kfnh 25 mm cho phep dat viira dudi binh each nhidt dewar, lam tiln dl cho vide cac mdu dai tir nhiet dd Ni-ta Idng 77K de'n nhiet phong 300K Dd ddng nha't ciia tir trudng viing cd chilu dai 20 mm nho han 1% la dii dam bao dd tin cay cho cac phep Tir trudng cue dai ngudn phat ciia he sinh la 22,5 Tesla vdi nhidt dd ban ddu cudn nam cham la -lOO^C Cac xung tir trudng co dang mdt ban chu ky hoac mdt chu ky sin, dd rdng cd 3,9 mili giay va 32 mili giay Cac xung tir trudng cho phep tid'n hanh nhilu phep tren cac vdt lieu tir hien dai Cudn thii ba cho cudng dd t\S trudng Idn tdi Tesla diing dl nap tir cho cac nam cham cd dudng kfnh tdi 50 mm Da thid't ke che tao dugc he dilu khiln nap va phong dien cho mdt bd tu didn Idn vdi dien dung 24 mili Fara Vdi thd' nap cue dai la 2.500 V, he dilu khiln ngudn nang luong 75 KJ phong dien qua cac cudn day nam cham vdi xung dong cue dai Idn tdi trdn 40.000 Ampe thdi gian 3,9 mili giay He dugc phat triln trdn ca sd phdn ciing dien tir va chuang trinh phdn mIm ghep nd'i may vi tfnh gdm cac mach dilu khiln tu ddng va chdp hanh cdng sudt Idn cd chi tidu ky thuat cao Hd cGng da ddm bao dugc cac chiic nang bao ddng va an toan cho thid't bi va ngUdi sir dung Da thid't kd' xay dung phdn ciing va phdn mIm he thu thdp vd xu ly tin hieu bdng cac mach didn td tuang tu va xir ly sd Trong viec chi tao he cudn day thu tin 143 hidu (cudn pick-up) ddng true cd dd nhay, dd tuyd'n tfnh cao la quan trgng 1024 mdu tfn hieu tren kenh ty le vdi vi phan ciia tir trudng theo thdi gian dH/dt va vi phan cua txs dd theo thdi gian dM/dt dugc thu thap dong thdi va xir ly mdt phep Chuang trinh phdn mIm xir ly tin hieu sd theo thdi gian khdng thuc (post-time) da dugc phat triln trdn ngdn ngii hinh tugng Labview cho phep xir ly chfnh xac va mIm deo He dat dugc dd chfnh xac cho phep tir trudng vdi sai sd 2% va tir dd vdi sai sd 0,5% Dd nhay cac phep tir dd tdt han 10'^ emu Cac kd't qua la phii hgp vdi mdt hd tir ke tir trudng xung cao thdng dung trdn thd'gidi Trai qua thdi gian han mdt nam, hdng tram phep dd duac tien hdnh tren he nham phuc vu cho nghidn ciiu va ddo tao tai cac ca sd nude d6ng thdi chdng minh tinh chinh xac ciia hd D6 la cac phep su phu thudc ciia tir dd vao tir trudng M(H) tai cac nhiet khac va su phu thudc ciia tir theo nhidt dd M(T) tai cac tir trudng khac Cac phep dugc thuc hidn trdn ca cac mdu bdt djnh hudng, mdu bdt rdi va mdu khd'i Do la cac phep xac djnh tir trudng di hudng ciia cac mdu dan va da tinh thi bdng ky thuat phat hien diim dj thudng SPD Dd la cac phep nhdm thu nhan dugc mdt dudng cong tir trd ddy dii ciia cac nam cham cd tir trudng bao hoa cao Ngoai nhieu nam chdm cdc ca sd nghien cuu vd img dung dd duac nap td tren he vdi cudn day nam cham thii ba Ke't qua cho cac gia tri luc khang tir va tfch nang lugng cao han so vdi cac ngu6n nap tir thdng thudng vdi tii trudng tha'p hidn cd d Viet nam Cd the ndu mdt vai hudng phat triln tid'p theo cua hd nhdm nang cao han nua kha nang phuc vu cua nd Trudc mdt cdn che' tao bd sung binh chiia Nit-ta Idng cho nhidt dd ddu cudn nam cham xud'ng tdi 77K Dilu cho phep tang dugc ddng didn phdng, tire la tang dugc cudng tir trudng len xdp xy 30 Tesla nhu thid't ke' Mat khac he cho phep cd thi md rdng nhirng nghidn ciiu phuc vu ling dung cac thdng sd tir khac nhu dd cam tir, nghidn ciiu su chuyin ddng ciia vach domain tii trudng ngoai v.v , cac thdng sd phi tir nhu: didn trd, tir giao va cac tfnh cha't quang phu thudc vao tir trudng ciia cac loai vat lieu DANH MUC CAC CONG TRINH NGHIEN CQu LIEN QUAN DEN Di TAI LUAN AN Trdn Quang Vinh, Nguyin Phii Thuy vd Nguyin Minh H6ng (1991), He tu tu dd td trudjig xung, Ky ye'u Hdi nghj da't hie'm toan qud'c Idn thii 2, Trdn Quang Vinh, Nguydn Phii Thuy, Than Diic Hiln va Vu Anh Minh (1993), He tddg ghep ndi vdi vi tinh, Ky yd'u 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he sd tucnig tdc trao doi n,^ su dijng he td ketd trudng xung cao, Bao cao tai Hdi nghj Vat ly toan qud'c Idn thii V PHU LUC CHi TIEU KY THUAT CUA DAO DONG KY N H KENH HM -1007 • Lech doc: - Dai tdn truydn qua cho tfn hieu analog Id'i vao: 100 MHz, - Cac hd sd dilu khiln lech doc: tir mV/div tdi V/div - Md rdng thang Y: de'n mV/div - Trd khang Id'i vao: MQ 11 25 pF, Ghep DC - AC - GND - The' Idi vao cue dai: 400 V p-p • Lech ngang: - Cac thang quet thdi gian: tir 50 ns tdi Is/div - Md rdng thang X: 10 Idn de'n ns/div - Dai thdng bd khud'ch dai X: MHz • Sd hoa va Eg nhd: - Td'c dd la'y mdu cho chuyen doi A/D cue dai: 40 MS/s cho mdt kdnh - Dung lugng bd nhd: k x bit cho mdt kdnh - Triga trudc: hoac 50% - Dd phan giai: X = 200 diim / div; Y = 25 diim/div • Chi tieu chung: - Man hinh: D14-372 GH, vudng kfch thudc x div; cao thd' 14 KV - Cdng sudt tidu thu: 47 Watt - Trgng lugng: kg - Kfch thudc: W 285, H 145, D 380 ^-^^ PHU LUC Mdt thf du vl dd thi cdp bac (Hierarchy) ma ngu6n diagram ciia chuang trinh phu (SUB.VI) dilu khiln nap va phong dien dugc vie't ngdn ngu hlnh tugng Labview Cac hinh tugng (icon) chuang trinh la cac chuang trinh phu nOa Thf du, "Qut Port" la Chuang trinh phu xudt mdt byte cong co dja chi xac djnh, "In Port" la dgc trang thai ciia mdt c6ng vao cd dia chi xac djnh, "GPIB" la doc sd lieu tir ghep nd'i GPIB-IEE488, "LOAD" la nap mdt file v.v ... trudng xung: dac diim ciia cac ngudn phat tir trudng loai la chi cSn cd nang lugng nho nhung v5n cho phep nhan dugc cac xung tiJf trudng cd dinh cao thdi gian t6n tai ciia xung ngln Tijf trudng xung. .. nhu tii ketic trudng xung cao lai cSn phai tao dugc nhirng xung dong dien cue lorn va thie't bi phai dam bao thu thap va xiT ly dugc cac th6ng s6 cua he mot thcri gian t6n tai xung ra't ngan Do... thuat xung cd th^ dap u:ng dugc yeu cdu dugc dijng de tao cac xung tir trudng c6 bien dd tren 10 Tesla nhung khoang thdi gian t6n tai chi cd mili giay de'n giay R6 rang vdi m6t he tit trudng xung