Isotopic Constitution of Plutonium (La Report 168)

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A -em-rpsatrographic exambation of plutonium has rsvenlsd a peak rt tho Of this perk i 8 not yet cap late.

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Panni fins aug ges hd that the anamdouely high sponta~aoua-2iceion rata Experimental tube tat i ation of thtr hypothesf8 Beretsfare, only OD. nethod m a available for estlmattng the mount of the irradiation, ne, ths ea mpla had received and on the value of a n Bacher hns cbsck on the qualitative nature or the fudamontal groossas8 Lnvolosdj and that in aombiaation with other obtainrbl e data, Pq uw t it at tvs mp1a- rpcctrographfc dst eni a a - o on at ant L~ and the value of N as a function of energy. 1) Positive identification of' the isotope %ao, Tho pr rd wr sxperiaoce of one of tha authors with the Nitr ho.W2uorids mall apectramstar lad us to believe that it ahauld be posaibls to detect and u5ab~:re

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report, i a that of the ion sourae. No cou~tnmdr,aP ph ton fm are knonrr a t the prsoemt the with vol at il it iar comparebla t o that o f urnaim hexafluoride. la fact, chemical knowlodge at Cia time of Efrfe report inbiorter that the most volatile compound of nhfch the cbanistry i s hr0m t r plutonium trichloride, whioh, according t o Wainstock2), ha8 a vapor proasurb of about b x 10-4 ma at TOOo C. Qa the ndvlce af Reinstook and Garner, us did not hygroocapia urd would. therefore, undoubtedly prrernt aerioue ~gcuumproblem i n tiha moms spsatrcznater unlrss very exacting handing technfquaa WOPO developed, Othbr hmd, the rrsults obtained by Petl mM, Wpktn, 0nQ Weissmra ham shown that under the proper coaditionr and with the proper technfquss, plutonium metal it a clf can b e readily vaporized in high vacuao bacardfngly, the ion Ltourco ia the sbd ard Bier spectrometer una modified t o include a mioro-fumacs o f tantalum frm ahich the filrmmt (Fig. La) uUoh i s rurroundad by a tantalum rodintian shield, (Fig. lC), The vspot prsluur*d) of plutonium at these tanperaturea are high snough to give Fig. I ira rode drawing of the modified arrangement. The 8uf fiG i - t ion ourrents to pann it aacurate mea ~ urs ma tls ~C artla vapor shielda nnich ware found nsaeraary to prnvmt de atrio al conduotion on the glras insulatorr are not ahom inthe flgura. Othor ds tail e of the rpeetromster hhto rlraady been publiahed by

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inverted r a d mauntud on a aoprrate open metal f+ame t o facilltaate operatiom on the It should be meatieaeb that in thi0 application the PpectromsCer tube m u E. Adjustaamk rad Tart8 of the Mass Spwtrornatrr rith Mercury Tho prarenoo o f msrourp in tho amas epectromatsr from tha mercury airfusion 60UrO6 o f $On# for pr61idnAry adjurtmglt and routine oheoking of t h e operation of - 0 dons through cut-cmd-try t e s t 8 on the resolution of the Hga2 and Hg20f 1003. p l o t of the ma60 agscttum about tha Hgm2 aad ggal peaks. The trvd vertical dotted lioor at the base af each peak represent the thsaretioal ddth of the pes& as @PQ

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apr eow a of about 10-9 mm. b further oheck ras mads on the parforrmnaa of the inh8ve vapor prssmr@r cc qur ble with that of plutonium. far uae as rtuld-in m d m8 lntroduoed in a Mo eruc%ble. eource did net rrr ul t in lonr of rsmolutian. The rrtia of the in tem lt irs of the taro pmkr of pig. 3 deer not give the Several metah ara haom to Thir reruft indicated thrt aabifyiag the ion. in wpectroaetsr out ra at during the detailed recording of thir epectnun. of tha ratio mads in rapid alteraatioo o on fim ed the ratio given by Astaa to P fer Thie f a mused by a shift The kokgrouzld at the 120,s ma81 posft.fan mi found to b e l o r 6 than 1/lO,OOO o f the cur rat due to baskground t o ba fourrd ktthe %a*p os it ion in the caae o f &9. at t h e 120.0 mas position. This fa$ indicative of ths IZJ. P mr mum RESULTS ON 49 During the experiment performed on t i n , difficulty ma encmnterfd in that the ms- did not oapotitr f’rbaly, prrrumably beccause of th a form tion of’ a rurface fib during the prwmsr of brling. ma of feat required the uno o f higher furnace taqerrh.lreu than mre mt fci pi fed, and a t such t qs rat ur08 it wa8 found that th6 ties d$rngpatrd on owl ing, ffeiamm, i t ma believed t bt the Pormrtion of ouch afilm oa 49 muld not aause dffficultiea, dime, aocording t o their experience, tantalum i n mt readily by moltea Ua tho hair of the e ~ or fs nc rof Wpkin, Perlman, pod

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of' 49 mdted, wrfacs teurian would oarry the frrs mrkl to ad3rcmt aleaa wallr of the o mci b lr, uhmco it aould vaporite frwly. to the large peak obierved, a r r u d t o bo rt maia 2%. a mall p& '*.Ifound at

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fier used. It irr, naoerthelesr, rearonably certain that such kn hoto pee id sts ; partieuLirly since duriag the coura e of the short tun, the currents were incr ~ aas duntil t h e a0 peak ms six times more intmase in current thnn illustrated in Fig. 4. several msaeuronentr on the ratio of current8 atthe 2&0 and 239 r m ~ 8 8p on l tiu cs, wo conclude thre 9ha0 f r preaeat t o J e 3 + 0.5 parts in id-+, During the publication of thi ~report, data from X giving the gram of produot pert on for the oomponsnts of Lot -P were reaeived. to oalculate the mount of U O In a given botch of 49 by meatla of a farmula prorfdtc' These data can be ueed The data and dou lrt fon are proranted in TIble Ift

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Ths agreement with our ffpre, 330 t 50 pp,ts good. of error is fortuitoua. The follorring may be eaid a0 to the rel&Rbiliey of our observation o f &as., 1) The epcctrmetsr was operated at 6 06cuum of t h e ordor of 1 x nm of To attain a vacuum of thi a order of aagaitudo in an inatrumeat of this MnC,norcury, prolonged baking and pumping a t high temperatures are necasaary. Bc grease or rubber; gaekot joints onn be used. it i every unlikely that heavy maleculeo present as m8idUar background in the appar ? . - a tu8 could have beon reaponsibla f o r this peak. found t a be preaant. 00 t h o baaia of the general behavior of eueh Znatrwnents, Heavy molecule background WOB not 2) The peaks a t mati position0 239 m d 240 wore both found to be very ratio of the inteaeities of the two linea over the period aC observation, which wa8, unfortunately, rather brief. The varfation with temperature me of such nature *hat ‘tho independent of temperature and tine 3) rt seem unlikely tint the peak a t 2ko iss “gho~t”,aince as far El8 o a ~ be a8eertainad from the data, itis of the aatlcipated ahape a d occur8 at the antialthough searcher were made for thm. Ro such “ghosts” appear i n either t h e mercury Or tin opectra, It ahould be stresred that this restilt i a E preliminary one, partloularly since the following addftjanal cliscks on the reality of the &O peak 6 1 1 be =d.e in I ) The preaatsre o f rator vapor in the eyetem CBTI be drastically reduced through the u8e of a liquid air on the cold trap. If the peak a t 240 were caused by a bydrfde, tho ratio of it a intensity to ths intensity ofthe 239 peak ahauld be at‘-

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3 ) Ir, principle, perhaps the laoat exhaustive tebt of the chdca1idents ty o f tho two peaks obeer ~ e di . s that their "appearance potsntiale" b e the SUES. h a 'ifre 115. st spcctrometer I s not designed tomke meaaurancnte of "appearance potential", this t cat mill probably not bs mads unless it fs pointed out t o ua that it io rmceae. eary . Unfortunately t h e operatian of the speetrometer in thir firot ru3 y1aa no% a8 eimpie as desired. sul ted in production of metallic film8 on may of tho glass insulators in the ion tor ehieXds, and although thia kill b e simple to do, the decontamination of' t kei cn nource prior to uichiniag of the parts mill take 8one time. The evaporation of 49 from the lip a of the micra-furnace rnFor ttris reaaon, it will be nec,ess ~ r yto Introduce much more oamplflte icixXz7 wbich developed very quickly, i t -8 not possible t o mnks en axhauative exo.mi,vation ~ i ' On the beair of the results to date it may be mid Vats 1) A -86 spwtromater has been est up which can be uaed t o study the tsa - topio oonstttutfon o f ' elan ent order of tro part a in I@. by rubsequent renarcho For the pre ~ ent,sensitivity for eCrrn i e 0: tke It i s quit6 poreible that thio rensitioity can b e increased 2) Bidenas brr been obtain& for the exia ten oe of the faotopm *ao, and =o parti cull r sample of 49 mta3 ham beem gives a prslbiaary aaalyria.

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3) It shauld now be poe sib le to meeeurc 4)1% i s now posa fb let Q get Ma be o lute value o f *y. 5) 1% m y become pos sib h, by coanidsrable development in the futurxto