Hashi, Tsuneo

Hirai, Akira

Kawai, Takao

Sasaki, Masahumi

English

Kyoto University Research Information Repository

RIGHT:URL:CITATION:AUTHOR(S):ISSUE DATE:TITLE:Nuclear Magnetic Resonance PulseApparatusHashi, Tsuneo; Hirai, Akira; Sasaki, Masahumi;Kawai, TakaoHashi, Tsuneo ...[et al]. Nuclear Magnetic Resonance Pulse Apparatus. Memoirs of theCollege of Science, University of Kyoto. Series A 1959, 29(2): 205-2121959-09http://hdl.handle.net/2433/257430            Memoirs of the College of Science, University of l<yoto, Series A,                        Vol. XXIX, No. 2, Article 7, 1959.  NUCLEAR MAGNETIC RESONANCE PULSE APPARATUS                                                                        '                                    BY     Tsuneo gASIII, Akira IilRAI, Masahumi SASAIil ancl Takao KAWAI                             (Received Jt{ne 1, 1959)                                 ABSTRACT        A detailed description of the nuclear magnetic resonance pulse apparatus in our     laboratory is given. This apparatus is intended for measuring the spin-lattice relaxa-    tion time of proton in high polymer between 10 msec and 1,OOO msec.1. Introduction    The nuclear magnetic resonance method has been used to give valuable informa-tions about microscopi'c states ancl dynamical characters of many substances (1).Recently, the importance of informations about the spin-lattice relaxation time (Ti)has increased, particularly for high polymers, since the data obtained from nuclearmagnetic resonance line width or 12ne shape alone are not sufficient for full under-stancling of the internal motion in high polymer. '    The saturation method (2), which has been most frequently used for the measure-ment of Ti of high polymer, requires knowledge about the spin-spin relaxatien time(T2) and the magnetic rf field intensity (Hi). This method is rather complicatedand there are f"rther inconveniences caused by some anomalous phenomena associatedwith increasing magnetic rf field. intensity (3, 4), particularly in solid. The pulsemethod (5) is relatively simple and direct. Thus, we have constructed a pulseapparatus for the purpose of measuring Ti of proton ln high polymer. This apparatushas beeR successfully operated except for samples in the rigid state which have broadlines and require, for measurement, extremely intense and narrow rf p"lse and shortreceiver recovery time not realized in the present apparatus. This situation, however,is not serious for our present purpose, since the most interesting phenomena to beinvestigated for high polymers are about the internal motion and therefore thesamples concerned are not 2n the rigid state.    ReceBtly, a few articles have already appeared abottt the nucle.nr magneticresonaRce pulse apparatus (6, 7). Still we feel it worth-while to report and discussabout our apparatus, because lt is more convenient for measuring Ti from 10 to 1,OeOmsec than other apparatus already reported, and in addition, it is diMcult, in ourj206 T. HASHI A. HIRAI M. SASAKI andZKAWAI '                          ))country, to use even sorne of the commercial devices described in the above articles,such as Tektronix Pulse Generator.2. Censtruction of apparatus    The diagram of the whole apparatus is given in Fig. 1. We have adopted 900-900pulse method for its simplicity of both constrttction and adjustment. The pulse trainmethod is also applicable but was not adopted because of its critical dependence uponthe 900 pulse setting. The T, of proton in high polyrner is relatively long, so wehave measured the pulse interval with a frequency counter consisting of a standard                                                Synchroscope          Bagsgg,t;LItg.,g,er Deiay-l- iNtlixer r.i2i <IT.,S/llllilgv,,,. Detector                                         Triggei'                                         selector                                                  Cascode                                         rf pulse                                                           rf signalPulsed             Delay II               Pulser                                       signal                                         amplifier                                                           amplifier            oscillator                                                  am lifier                ,P,g52e,,i,p,Ze,ry,:i,, ' lbd3ab5,esc't ->-•)y[iiagnet                                          Sample                                           coi!                   Fig. 1. Block diagramaudio frequency osci}lator, a bistable multivibrator, a gate andoÅí the present apparatus are all of standard type as usedapparatus. Our measuremeRts have been done at 25 Mc/secEach unit is described in delail in the following.  (1) Basic trigger ge}ierator    This unit determines repetition interval (the intervalThe repetition interval should be very long compared withrepetition interval, the easier the meastirement. In ourinterval has been chosen between O.5 and 5 sec. That theenough has been ascertained by checking that the signalfirst pulse (yi) does not become larger for longerbasic triggers, a frequency dividing unit and a decatronThe block diagram is shown in Fig. 2.undesired components of the output from the decatron,a desirecl large pulse, a long tail followlng and nine smallof the frequency dividing(8) is shown in Fig. 3.Cryostatof the whele apparatus.decatrons. Otherin the ordinaryand about 6,OOO units pulsegauss.                           between basic triggers).                            Ti, wh }e the shorter the                          measurement the repetition                         repetitlon interval is long                           amplitude just after the                       repetition iRterva}. To obtain                            system were employed.          Last three sections are inserted for eliminating                       whose wave form consists of                          pu}ses. The circuit diagramunit consisting of a catliode coupled monostable multivibrcator 'NILJCLEAR MAGNETIC ROSONANCE PULSE APPARATUSau rm Lua-L "    Freq. divicler                 Decatroni   cathodecoupled             (lcigO:.d,gVing)     monostable    multi.(l2AU7/207Saw•t`)othgenerator'66Gi--- 60c•secDifferentiatorR,C,andGediodeAmplifier{i1212AU7)                  =L th JL--"-           ?•i:.l.pewlel,iSD(i(,`leleeil.11::,05Cii)tslft,/i,giSOi}gllfdÅ}                  Fig. 2. BIock diagram of basiÅë trigger generator.                       12AU7                                         + 250 volt                       10K C: 1oo pf--O,5Ff            sooK 2o l< `g '6' -TT 1ooK                                                  (as Freq. divider)            100 K          oj            50 p                          -tr-         Fig' 3. Circuit diagram of cathode coupled monostable multivibrator as                delay unit or as frequency dividing unit.  (2) Delay l    This is also a cathode coupled monostable multivibrator as in Fig. 3. This unitdetermines the pulse interval T, which is the interval between the first and the secondtriggers and is measured by the pulse interval measuring unit.  (3) Mixer '                                  12AU7                                      +250          First trigger 100p 100P second trigger-"L-.-J-----t---Le50psop`+ww'1 R(2M)el#100K10K501<(asDe!ay)INA4yHeS}20Kou    500 K- --L -- -r----rl----•--{g})iii 5oo l<              10K           ptFig. 4. Circuit diagramF-@poo1r.eixmfoOut208 T. HASHI, A. HIRAI, M. SASAI<I and T, KAWAI    In this unit, the first and the second triggers are mixed. They are desired tohave the same waveform. For this reason, the last section in the basic triggergenerator (Fig. 2) is inserted. The circuit diagram is shewn in Fig. 4.  (4) Delay ll    This unit serves the signal being located at a desired position oii the synchroscopescreen. The circuit diagram is the same as in Fig. 3.  (5) Pulser    This unit is triggered by the output of Delay II and creates a rectangular Nvave-form whose width (t,.) is controllable so as to be rH,t,.=rr/2 for 900 pulse. In ourCase, tw was about 5Ltsec for 900 pulse. We have used a cathode coupled nionostablemultivibrator, though a more excellent circuit, such as plate coupled multivibratorwith piate catching diode (9), woulcl be desirable.  (6) Pulsed oscillator    A contimious rf oscillation and pulse modulation system (7) would be desirablefer the frequency stability and the rf pulse wave shape. But it is very dithcult toavoid the rf power leakage during off-time and this leakage makes beat with thenuclear signal, so we have adopted a puised oscillation system. This unit is essentiallythe same a.s that of E. L. Halm (5). Care must be taken so that both the rf fieldintensity and the pulse width sliould not be modu}ated by heater httm voltage.  (7) Pulsed rf amPlifier    This unit is inserted for obtaining a large rf mcftgnetic field Hi, which shouldbe severcal times larger than the resonance line width dHii2. In our apparatus, Hiwas about 15 gauss, which was limited not by the available power fyom power tube 813but by rf ptilse wave shape. We have lowered the "Q" of the sample coil to preservegood wave shape at the expense of rf field intensity. It is also desirable to set therf amplifier, the sample coil, and the cascode signal amplifier in one chasis foravoiding the capacitive coaxial cable connections. The circuit diagvam of this unittogether with the sample coil is shown in Fig. 5.                                   Sample coil  fi'om pulsecl 8i3 ' Ls'rf osciltator9}    50 -N--25 Mc sgioo I<   '  o,oesFig. 5.rrCircuit}{.-fi.•..c5.00p r "'T      O.05-75V   diagramO.2tF300 of rfMJI: p. ulsel{.l?.C.     7p   1 5') pr1000p 101i.H . (-v1500V)    amplifier,gjrscEi6A <5,::: l      O.OOI      I{.l?.C.    T O.OOf, O.Olsample coil,      6.J4 I(X)i -'- ls ,,O.()Ol i:II< IK             x             T  -if 135and cascode signalto rf signal  jamplifierlE=Si)O,oo5amplifier,               NUCLEAR MAGNETIC ROSONANCE PULSE APPARATUS 209  (8) Cascode signal amPlifier    This unit serves for improving the overall S-N ratio, and is of original Wallmantype (10). '])he circuit diagram is shown in Fig. 5.  (9) rf signal amPlifier and detector    This unit is essentially of the standard type (IX) with some modlfications in theinput stage. The circuit diagram of this unit is shown in Fig. 6. We have adoptedthe straight amplification system (gain 90 db, btand-wrdth 4 Mc/sec, receiver recoverytime about 10ptsec). But a superheterodyne system would be convenient in the f,.. 6J4 6A U6 6A L]6 6A Ui6 6Al6 t' 6AQ8 -l}6AQ8C"ifii,'i,,,,,,i :-,,iSl,,T.:ltl()rx8:'li;scss/2"ne:'IliP                    Fig. 6. Circuit diagram of rf signal amplifier.variable rf frequency measurement. If the Eynchroscope hcas a geocl frequencycharacteristics up to about 30 Mc/sec, it is desirable to omlt the detector to shortenthe recovery time.  (10) SynchroscoPe    This is a commerclal procluct. In our measurement, tlie sig.nal cappears on screenonly once per several seconds, so a long persistent cathocie ray tul)e or a memoriscope(recently commercialized) would be convenieRtly used.  (11) Pulse interval measuring unit    The block dicftgram of this unit is shown in Fig. 7. 'I{'he audiofrequency oscillatoris a commercial variable audio frequency oscillator, which is suthcient for our presentpurpose. For more accurate ineasurement, the crystal oscillator and frequency dividingsystem should be used. Tl]e circuit diagrain of the bistable multivibrator (12) and      L Bistable tr                                                 --tfsetw---..m--                   multivibrator-:z$------ ---r-- ptorK r)K7f)IKe,ooriiTE-t`thtriil(<o.uts;"•,===:--'v'?ap,                               '--))--------                                                            becatrons                    Variable r'-                    audio freq.                    oscillator                               wwrwgAv--               Fig. 7. Block diagram of pulse interval measuring unit.the gate (13) is shown in Fig. 8. It may happen, however, that the decatrons begincounting the interval between the second and the next first triggers instead of thedesired pulse interval. The switch in the diag. ram serves to change the measgring210 T. HASKI, A. HIRAI, M. SASAKIand T, KAWAIfrom the unclesired interval to the desiredt12AX7   l2AU7        ÅÄ2soV20K 20Kone.Triggers e.OOI<bl,OOKi- 9V -Ef--   r-50 p I'..20 KS12AX7  500K Swush         v20 I<i8,82i 250 K,IOKso pr100ff'<12AX7'+2soV2scKs.r..t-Ssee K2 iiO K.tT3ovmultivibrator and gate.50 K  e.otLm---<ll)     to Decatronl----K9 froin      Variable5ooK a' f oscillator              Fig. 8. Circuit diagram of bistable  (12) Magnet    The diaineter of pole piece is 12cm. The pole gap is 3.6cm. The currentrequired for 6,OOe gauss is about 500mA. The fieid homogeneity is sgch that thefree induction decay signal lasts about 500ptsec for narrow lines, which was con-venient for adjustment and measurernent.  (13) Magnet Power suPPIy    This is essentially the sarne as th.at of Ii. L. Anderson (14). One measurementrequires about i5 minutes, at least cluring which the clc inagnetic field intensity (FIo)must ]" L- stable.  (14) Cryostat    A gas flow cryostat (15) has been used. The constancy of our app`Rrcnttts-wasnot so good, and about -J-10C. We cftre now planning some improvements.E. Preeedures    (1) The dc rr}agnetic fieid iiktensity JIo is a(ljustecl for exact resonance, searchingfor the mcaximum of the slgnai after the first pulse for a small pulse width t..    (2) Then, the pulse width is graclually expanded so as tQ satisfy 900 pulsecondition, ut'ilizing that the signal after the second pulse sheul.d be zero 'for a smallpulse interval (Delay I>, and 900-900 pulse condition (see Fig. 9 (a') .). In Fig. 9 (a), thesynchroscope trigger selector is set at 1(in Fig. 1) and the synchroscope sweep speeclis relatively low. With the trigger selector set at 3 (in Fig. 1) and the sweep speedincreased, and otherwise on the same condition, the screen pattern is like Fig. 9(b).    (3) Then the pulse interval is gradually expan.ded by changing R and C iRDelay I, and calibrated by the ptdse intervai measuring unit (see Fig. 10). 'lrhe(lifference between the signal after the first pulse y, and that after the second pulse(y2) is plotted against the puise interval T on semi-logarithnn.ic section paper. Thesiope of the plotted }ine, when straight, gives T, (see Fig. 11i.NUCLEARMAGNETIC ROSONANCE PULSEAPPARATUS 211Fig. 9.Sample :     (a) (b)Synchroscope screen pattern for 900-900 pulsesecond nuclear signal disappearing,PMA, Ternperature : 340C, Repetition interval ;Resonance frequency : yo=25 Mclsec,Pulse width: t,.==71xsec,(a) Synchroscope trigger selector set at 1,    Sweep rate : 200ixseclcm,(b) Synchroscope trigger selector set at 3,    Sweep rate: 50psec/cm.setting,2.2 sec,First    (a) (b) (c)pulse and nuclear Second pulse and nuclear First and second pulses  signal signal nuclear signals        Fig. 10. Synchroscope screen patterns for measuring Ti,     Sample: PMA, Temperature: 340C, Repetition interval: 2.2 sec,                Resonance frequency : vo=25 Mc/sec,                Pulse width: t,,=7ptsec,     Sweep rate ; 50Asec/cm, Pulse interval : T=140 msec,                (a) Synchroscope trigger selector set at 1,                (b) Synchroscope trigger selector set at 2,            ' (c) Synchroscope trigger selector set at 3.andcmYl-YL,   5Fig. 11.:1O.5         100 200 ?OO 400 Semi-logarithmic plot of difference between pulse (yi) and that after second pulse (y2) terval e,., slope giving Ti=290msec. Data are      T    m.sec  500signal after firstversus pulse in- given in Fig. 9.212 T. HASHI, A. HIRAI, M. SASAKI and T. KAWAI    The error of our measurement of T, is within about !O per cent. It would comemainly from the reading error of the signal amplitude on the synchroscope screen.The failure in adjustment of 900-900 pulse condition and the fluctuations in the shapeand width ef the pulsed rf magnetic field cause also error, particularly ln case ofnarrow intense pulse$.    As mentioned in Introduction, the mest important points for improvement tomake the apparatus app}icable to the sample in rigid state are to have a narrowintense rf puise of good wave shape, and to have a short receiver recovery timae.Both are very dithcttlt to attain, though some efforts have been done (6, 7, 16, 17, 18).The present apparatus, hovLrever, is suMcier.t for investigating the internal motion inhigh polymer. The full data obtained by the present apparatus wiil be published later.Acknewledgements •    The authors would iike to express their sincere thanks to Professor I. Takahashifor his continuous interest and discussion. The authors' thanks are also due to Mr. K.Sttgibuchi and other members of our laboratory for their assistance.                                REFERENCES 1• See, e•g. E. R` ANDREw, Nuclear Magnetie Resonance (Carnbridge University Press, New York, • 1955) ;    G• E. PAi<E, Nuclear Magnetic 1?esonance (`Solid State Physics' edited by F. SEiTz and      D. TuRNBuLL Vol. 2, Academic Press New York, 1956) p. 1 ;    M- H• CoHEN and F. REiF, Quadrupole Effects in Necclear Magnetic 1?esonance Studies of      (`Solid State Physics' edited by F. SEITz and D. TuRNBvLL Vol. 5, Academic Press Inc•,      New York, 1957) p. 321. 2• N BLoEMBERGEN, E. M. PuRcELL, and R. V. PouND, Phys, Rev., 73 (1948), 679. 3• A• G. REDFiELD, Phys. Rev., 98 (1955), 1786. 4. K. ToMiTA, Prog. Theer. Phys., 19 (1958), 541. 5. E. L. HAHN, Phys. Rev., 80 (1950), 580. 6• J• ScHwARTz, Rev. Sci. Instr., 28 (1957), 780. 7• J• C. BucHA, H. S. GuTowsi<y and D. E. WoEssNER, Rev. Sci. Instr., 29 (1958), 55. 8• J• MILLbe!AN and H.TAuB, Pulse and Digital Circuits <McGraw-Hill Book Company, New      York, 1956) p. 187 ff. and p. 363 ff. 9. Reference 8, p. 174 ff;    B• CHANcE, V, HvGHEs, E. E MAcNicHoL, D. SAyRE and E C. WiLLmMs, rvaveforms,      MIT Radiation Laboratory Series (McGraw-Kill Bcck Company, New York, 1949) p. 179 ff•10• G• E. VALLEy and H. M!LLMAN, Vacum Tube AmpliLliers, MIT Radiaticn Laboratory Series       (McGraw-Hill Book Company, Inc., New York, 1948) p. 656 ff.11. Reference 10, p. 166 ff.12. Reference 8, p. i40 ff.13. Reference 8, p. 435 ff.14. H. L. ANDERsoN, Phys. Rev., 76 (1949), 1460.15. E. L. ANDREw and R. G. EADEs, Proc. Roy. Soc., A216 (1953), 398. 16. L J. LowE and R. G. NoRBERG, Phy$. Rev., 107 (1951), 46. 17. L SoLoMoN, Phys. Rev., 110 (1958), 61. 18. R. J. BLuME, Phys. Rev., 109 (1958), 1867.

Nuclear Magnetic Resonance Pulse Apparatus

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Nuclear Magnetic Resonance Pulse Apparatus

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