elec tro chem i cal etching pro cesses for the de tec … · elec tro chem i cal etching pro cesses...

12 Nu clear Tech nol ogy & Ra di a tion Pro tec tion –1/2004

ELEC TRO CHEM I CAL ETCHING PRO CESSES FOR THEDE TEC TION OF NEU TRONS AND RA DON-DECAY PROD UCTS

by

Luigi TOMMASINO

Re ceived on De cem ber 1, 2003; ac cepted on March 23, 2004

The elec tro chem i cal etch ing, be cause of its com plex ity, is of in ter est when it makes itpos si ble to achieve de tec tion char ac ter is tics which are not en coun tered with the chem -i cal etch ing. These unique char ac ter is tics can be found for ex am ple for the per sonaldo sim e try of low-energy neu trons around nu clear re ac tors and for the de tec tion of both low- and high-energy cos mic-ray neu trons at civil avi a tion al ti tudes. In par tic u -lar, suf fi ciently large sig nal-to-noise ra tios for cos mic ray neu tron mea sure ments canbe achieved by us ing stack of polycarbonate- and/or CR-39-detectors, since the elec -tro chem i cal etching pro cesses make it pos si ble: (a) the rapid scan ning of large de tec torar eas, and (b) the count ing of co in ci dence events in paired de tec tors in duced bya-few-microns long tracks.The de tec tion of the ra don de cay prod ucts is hin dered by the fact that their con cen tra -tions are al tered in the vi cin ity of de tec tor sur face dur ing the mea sure ment.Polycarbonate de tec tors may be use ful in solv ing these prob lems both be cause theyreg is ter ra don-decay prod ucts far away from the plated-out sur face and they can beman u fac tured with any pos si ble ge om e try and/or shape. How ever, it is pos si ble to usesev eral com bi na tions of chem i cal and elec tro chem i cal etch ing steps which im plies thepos si bil ity of new ap pli ca tions of track de tec tors for the reg is tra tion of neu trons, cos -mic rays and ra don de cay prod ucts.

Key words: ra don, neu trons, cos mic rays, track de tec tors, do sim e try, chem i cal etch ing,elec tro chem i cal etch ing

IN TRO DUC TION

The most im por tant in cen tive for the de vel op -ment of elec tro chem i cal etch ing (also re ferred to asECE) was the ur gent need to im prove neu tron do -sim e try [1]. The per sonal fast neu tron dosimeteravail able in the 1970’s was based on nu clear emul -sions [2], which re lied on de tec tion of the tracks ofin di vid ual re coil pro tons in thin pho to graphicemul sions. This do sim e ter man i fested var i ous

short com ings such as poor low-energy re sponse,track fad ing and sen si tiv ity to low-energy gamma-and X-rays. These draw backs were very se vere in thecase of per sonal neu tron do sim e try in fa cil i ties hav -ing large num bers of low-energy neu trons andmixed gamma neu tron fields, such as re ac tors [2].

Soon af ter the dis cov ery of the elec tro chem i -cal etch ing, it was pos si ble to de velop a per sonalneu tron do sim e ter based on neu tron-induced re -coils in polycarbonate (PC) de tec tors, whose re -sponse was un af fected by X-ray or gamma ra di a -tion, by fad ing or by en vi ron men tal pa ram e ters,such as high tem per a ture and hu mid ity [2, 3]. Thisde tec tor was quite prom is ing, so that, soon af ter itsdis cov ery, a com mer cial do sim e try ser vice adoptedit for the use in rou tine per son nel do sim e try [2].How ever, with this do sim e ter it was pos si ble onlyto reg is ter doses of neu trons with en ergy larger than 1 MeV. It was the dis cov ery of CR-39 [4] that madeit pos si ble to de tect neu tron-induced pro ton re coilswith en ergy as low as tens of keV [5, 6].

Sci en tific pa perUDC: 539.1.074:541.138BIBLID: 1451-3994, 19 (2004), 1, pp. 12-19

Au thor’s ad dress:Na tional Agency for En vi ron men tal Pro tec tion andTech ni cal Ser vices – APATVia V. Brancati, 48, 00144 Rome, It aly

Au thor’s e-mail:[email protected]

DO SIM E TRY OF LOW-ENERGYNEU TRONS

To un der stand the im por tance of elec tro -chem i cally etched de tec tors for neu tron do sim e tryit is use ful to de scribe the dif fer ences be tween thechem i cal-and elec tro chem i cal etch ing pro cesses.

For ex am ple, fig. 1 il lus trates the dif fer ences in re sponse be tween these two etch ing pro cesses forthe par tic u lar case low-energy pro ton re coil tracks,as sum ing that they orig i nate from the sur face.

The track for ma tion is shown sche mat i cally atdif fer ent etch ing times t1, t2, t3, etc., [5]. In the caseof chem i cal etch ing (up per part of the fig ure),tracks (a) and (b) re main pointed un til they areetched to the ends of their tra jec to ries. Since pro -longed etch ing is usu ally re quired in or der to be able to etch high-energy pro tons, track (c), tracks (a)and (b) both be come blurred and may dis ap pearfrom view.

At the end of etch ing, thick de tec tor lay ers(typ i cally 5-15 mm thick) have been etched awayfrom the orig i nal sur face and most of theshort-range tracks within these lay ers may have dis -ap peared from view or are very dif fi cult to count.This is par tic u larly rel e vant for neu tron en er gies be -low 500 keV, where, for a sin gle do sim e ter, largevari a tions in the num ber of counted tracks oc curamong dif fer ent ob serv ers and, for a given ob server, at dif fer ent times of count ing [5, 6].

The lower part of fig. 1 shows the ini ti a tionand prop a ga tion of tree ing phe nom ena in newlyformed tracks for purely elec tro chem i cal etch ingpro cesses. In this case, once a track with apointed shape has been formed, it starts tree ing.As the elec tro chem i cal etch ing pro ceeds, those

tracks al ready tree ing, (a) and (b), con tinue toen large while more tracks are formed and ini ti ate tree ing, track (c). This type of etch ing can becon sid ered as just the op po site of the chem i caletch ing at the same tem per a ture, sincelow-energy re coil tracks keep en larg ing and be -com ing more vis i ble un der elec tro chem i cal etch -ing pro cesses, while they may dis ap pear fromview un der con ven tional etch ing as shown in theup per part of fig.1. If tracks are formed at the be -gin ning of elec tro chem i cal etch ing pro cesses,

they will grow to a greater ex tent than thosewhich will be formed at a later time, thus re sult -ing in very dif fer ent spot di am e ters [7, 8]. The re -sponse to pro tons of CR-39 de tec tors was thor -oughly in ves ti gated by Cross et al. [6], whodem on strated that the elec tro chem i cal etch ingpro ce dure can si mul ta neously de tect pro tonsfrom 10 keV to 3 MeV. Fig ure 2 shows trackspots pro duced by pro tons with en er gies of 30,50, 100, and 145 keV re spec tively [5]. On the ba -sis of these re sults Cross et al., [6] cal cu lated there sponse of CR-39 to neu trons. The re sults ofthis cal cu la tion are shown in fig. 3 [6]. The solidline shows the num ber of tracks per cm2 per 10mSv cal cu lated for CR-39 with a 2 mm thickpoly eth yl ene ra di a tor in front of it. The dashedcurves show the sep a rate con tri bu tions ofprotons gen er ated in the etched layer, which pre -dom i nate at low en er gies, and pro tons from thera di a tor which pre dom i nates above 1 MeV. Thepoints were mea sured for nor mally-incidentmonoenergetic neu trons. All the above re sultswere ob tained by us ing a 25 kVcm–1 rms elec tricfield at 60 Hz with 6 N KOH in wa ter for 5 h at60 °C [6].

L. Tommasino: Elec tro chem i cal Etshing Pro cesses for the De tec tion of Neu trons ... 13

Fig ure 1. Sche maticil lus tra tion of chem i cal andelec tro chem i cal etch ingpro cesses


DO SIM E TRY OF COS MIC-RAYHIGH-ENERGY NEU TRONS BYECE DE TEC TORS

With the com plex fields pres ent at flight al ti -tudes and/or around high en ergy ac cel er a tors, thereg is tra tion of suf fi ciently low neu tron doses by

dam age track de tec tors is ham pered by the poor sig -

nal-to-noise ra tio of these de tec tors.The sim plest way to in crease the reg is tra tion

sen si tiv ity of dam age track de tec tors is to in crease

both the ex po sure time and the de tec tor area. Be -

cause of their unique stor age prop erty, dam age track

de tec tors can be ex posed for any de sired length of

Fig ure 2. Elec tro chem i cally etchedpro ton-induced tracks

Fig ure 3. The re sponse ofelec tro chem i cally etched CR-39de tec tors ver sus neu tron en ergy

time. On the other hand, the reg is tra tion of large ar -eas (hun dreds of cm2) can eas ily be car ried out byelec tro chem i cal etch ing de tec tors. How ever, thepos si bil ity to in crease the reg is tra tion sen si tiv ity byin creas ing the de tec tor area is lim ited by the strongvari abil ity of the back ground of track de tec tors.

The back ground prob lems were fi nally solvedby a new reg is tra tion method based on count ing co -in ci dence spots in a matched pair of de tec tors [9].By us ing elec tro chem i cal etch ing, co in ci dence spots can eas ily be in duced even by a few-microns-longtrack in paired de tec tor-surfaces.

The co in ci dent method is well es tab lished forlong-range par ti cles which cross dif fer ent track de -tec tors in a stack (up per part of fig. 4). This co in ci -dence method has been suc cess fully ex ploited forthe reg is tra tion of high charge and en ergy (HZE)par ti cles in cos mic rays since the early dis cov ery ofdam age track de tec tors [10].

A com pletely new co in ci dence method is pro -posed in the lower part of fig. 4, where theetched-track ranges are so short that they do notcross any of the de tec tors, but they just pen e trateboth of the matched de tec tor sur faces. These tracksare typ i cally pro duced by neu tron-induced re coils in PC and CR-39 de tec tors [9]. It is ob vi ous that theonly way to pro duce co in ci dent spots with afew-micron long tracks (which can be eas ilycounted in large ar eas) is through the elec tro chem i -cal etch ing pro cesses.

The up per part of fig. 5 shows co in ci denceevents pro duced by elec tro chem i cal etch ing spotson two paired polycarbonate de tec tors as they ap -pear in a mi cro fiche reader. The iden ti fi ca tion of co -in ci dence events is very sim ple, in spite of the poorim age. The lower part of the fig ure shows a pair ofelec tro chem i cal etch ing spots, which do not form a

true co in ci dence since they be long to the same de -tec tor sur face: they have the same con trast andpres ent the typ i cal in ter act ing char ac ter is tics ofclose elec tro chem i cal etching spots.

When com pared with the re sponses of de tec -tors based on count ing tracks on a sin gle sur face, the re sponse of the de tec tors based on the co in ci -dence-method pres ent the fol low ing ad van tages[9]:

(1) con sis tently low back ground,(2) rel a tively flat re sponse, and(3) de tec tion with dif fer ent neu tron-energy

thresh olds.

COM BI NA TION OF CHEM I CAL- ANDELEC TRO CHEM I CAL ETCHINGPRO CESSES FOR NEU TRON ANDRA DON DO SIM E TRY

The most at trac tive char ac ter is tics of elec tro -chem i cal etch ing pro cesses in volve the pos si bil ity of us ing a va ri ety of com bi na tions of etch ing pa ram e -ters and/or chem i cal and elec tro chem i cal etch ingpro cesses for the pur pose of en hanc ing the de siredde tec tor re sponse. This can eas ily be achieved bycon trol ling the etch ing pro ce dure with an ex ter nalap pa ra tus. Bart lett and Steel [11] sug gested the useof a mi cro pro ces sor-controlled com bi na tion ofchem i cal- and elec tro chem i caletch ing pro cesses topro vide a rea son ably low back ground and an ac -cept able en ergy re sponse for neu tron do sim e try.

In prac tice, by proper choice and con trol ofthe elec tro chem i cal etch ing pa ram e ters in CR-39dur ing etch ing, it is pos si ble to ex pand con sid er ably the use ful ness of the elec tro chem i cal etch ing pro -


Fig ure 4. Up per part: co in ci -dences in duced by long-rangepar ti cles.Lower part: co in ci dencesin duced by short-range par ti cles

cesses [12] both for the de tec tion of neu trons, ra -don, and its de cay prod ucts.

Track for ma tion by chem i caletch ing prior to elec tro chem i cal etching

The elec tro chem i cally pro cessed de tec tors cansuc cess fully be used when track den sity is less than a

few thou sand tracks per square centi metre. Forhigher track den si ties both the spot di am e ter andelec tro chem i cal etching ef fi ciency de crease as thetrack den sity in creases [13]. How ever, a chem i caletch ing step for track for ma tion prior to the elec tro -chem i cal etch ing may be use ful to in crease the re -sponse lin ear ity [14]. Fig ure 6 shows elec tro chem i -cally etched tracks of al pha par ti cles from ra don onCR-39 [15], where the track for ma tion has been ob -tained by a chem i cal pre-etching. When the CR-39foil is ob served un der an op ti cal trans mis sion mi -cro scope, tracks ap pear as dark spots, as shown onthe left-hand side of fig. 6. By fo cus ing close to thesur face (es pe cially with a re flec tion type of mi cro -scope) the elec tro chem i cally etched spots will dis ap -pear and only chem i cally etched tracks ap pear, asclearly il lus trated on the right-hand side of fig. 6.The pos si bil ity to sep a rate the chem i cally-etchedtracks from the elec tro chem i cally etched tree-spotsmakes it fea si ble to ex ploit the ad van tages of bothtypes of etch ing.

Elec tro chem i cal etch ing fol lowed bychem i cal etch ing

When us ing elec tro chem i cally etching trackde tec tors for neu tron do sim e try in space, it is im -por tant to dif fer en ti ate the re sponse to neu trons(and pro tons) from that of heavy charged par ti cles(HZE par ti cles). This can be sim ply car ried out by a two steps etch ing. A first step of elec tro chem i caletch ing is car ried out only on one de tec tor sur facefor rapid scan ning of large ar eas. To iden tify thespots due to HZE par ti cles, Bart lett et al., [16] firstpro posed to use a sec ond step con sist ing of chem i -cal etch ing only. Be cause of the large range of theHZE, an etched pit is pro duced on the non elec tro -


Fig ure 5. Paired spots in duced by neu tron re coils inelec tro chem i cally etched polycarbonate

Fig ure 6. Chem ically- pluselec tro chem i cally etched tracks:(a) tree ing com po nents,(b) chem i cal-track com po nents. For view ing con di tions, see text

chem i cally etched sur face and also at the back of theelec tro chem i cally etched pit, al low ing track of HZE to be dis tin guished from tracks of neu tron sec ond -ar ies [16].

CR-39 WITH NO RE SPONSETO THE PLATED-OUT RA DON-DECAYPROD UCTS

Be cause of its high sen si tiv ity, CR-39 reg is -ters full-energy al pha par ti cles from ra don de cayprod ucts plated-out on its sur face, while the cel lu -lose ni trate and the polycarbonate de tec tors areboth in sen si tive to full-energy a’s from plate-out. These lat ter char ac ter is tics are very im por tant forthe mea sure ment of ra don de cay prod ucts or, ingen eral, when us ing track de tec tors in the barecon fig u ra tion [17]. How ever, CR-39 could bemade in sen si tive to plate-out, if pro cessed in sucha way that the tracks of al pha par ti cles (with en er -gies of 6 and 7.7 MeV) from ra don daugh ters arenot re vealed. This can be achieved by a two-stepsetch ing con sist ing re spec tively of a chem i cal etch -ing step for the for ma tion of only those trackswith en ergy be low 6 MeV, fol lowed by an elec tro -chem i cal etch ing step to en large only those trackswhich have been formed [14, 18].

Ta ble 1 shows the reg is tra tion ef fi ciency of dif -fer ent bare de tec tors (LR-115, PC, and CR-39) ex -posed at the NRPB ra don cham ber to 356 kBqm–-3hof ra don gas at an equi lib rium fac tor of F = 0.4. Theetch ing con di tions are:

– Chem i cal etch ing for 90 min utes in 10% (byweight) of NaOH in wa ter at 60 °C for LR115;

– 5 hours chem i cal pre-etching with PEW so lu -tion at 60 °C plus elec tro chem i cal etch ing at 30 °C in30% KOH in wa ter for 5 hours at 30 [kVcm–1] rmsand 2 kHz for polycarbonate. In the case of CR-39,the elec tro chem i cal etch ing pro cesses are the same ofthose for polycarbonate, while dif fer ent types ofchem i cal pre-etching were used, such as the fol low -ing:

– 5 hours chem i cal pre-etching at 24 °C with30% KOH in wa ter,

– 10 hours chem i cal pre-etching at 24 °C with30% KOH in wa ter, and

– 5 hours chemical pre-etching at 70 °C with30% KOH in wa ter.

While the 5-hours chem i cal pre-etching at 70 °C in duces the for ma tion of all al pha-particle tracks fromra don-decay prod ucts plated-out on the CR-39 sur -face, the reg is tra tion of these al pha par ti cles does notoc cur with the other types of pre-etching con di tions,listed above for CR-39.

These lat ter etch ing con di tions make it pos si bleto reg is ter only par ti cles with en ergy less than 5 MeV[14, 18] and thus al pha par ti cles from plated-outdaugh ters are not reg is tered. In con trast with theshort com ings of CR-39 etched only chem i cally (be -ing sen si tive to plate-out), the CR-39 may prove to bethe most in ter est ing de tec tor when both chem i cal andelec tro chem i cal etch ing pro cesses are con cerned. Inthis case, it is pos si ble to ob tain a de tec tor with all thechar ac ter is tics re quired (in clud ing the same of thoseof LR-115 and PC) by an ap pro pri ate choice of thechem i cal etch ing con di tions prior to the elec tro chem i -cal etch ing.

The polycarbonate de tec tor has the low est reg is -tra tion sen si tiv ity. In fact, this is the prop erty whichmakes this de tec tor very valu able for the de tec tion ofra don de cay prod ucts, as de scribed in the fol low ing.

THE UNIQUE CHAR AC TER IS TICS OFELEC TRO CHEM I CALLY ETCHEDPOLYCARBONATE DE TEC TORS

It is well known that the plate-out of ra don de -cay prod ucts on sur faces of dif fer ent ma te ri alscauses a de ple tion of their con cen tra tion in the sur -round ings of all the ma te rial-surfaces, which de -pends on many fac tors such as sur face-area, en vi -ron men tal pa ram e ters, elec tro static charges,ven ti la tion rate etc., [19-22]. This de ple tion oc cursalso in the vi cin ity of the de tec tor sur face, thus af -fect ing what is in tended to be mea sured. For a given at mo sphere of ra don and ra don de cay prod ucts, this ef fect in creases with the area of the de tec tor sur face.Even tually the de ple tion of ra don de cay prod uctsde creases as the dis tance from the de tec tor-surfacein creases [23-24]. Bigazzi et al., [20] and Hadler etal., [21] claim that the de ple tion oc curs mostlywithin 3 cm from the de tec tor sur face.

Since elec tro chem i cally etched polycarbonatefoils reg is ter only al pha par ti cles with en ergy lessthan about 2 MeV, they could de tect only ra don de -cay prod ucts at a dis tance greater than about 4 cmfrom their sur faces. The ideal de tec tor for this ap pli -ca tion would be a sphere made of polycarbonatewhich could eas ily be man u fac tured or are al readyavail able as a con sumer-type of prod uct. This spherecould also be an ex cel lent de tec tor for neu trons, sincethe ma jor prob lem with the dam age track de tec torsfor neu tron do sim e try is the strong an gu lar de pend -


Ta ble 1. Reg is tra tion sen si tiv ity of dif fer ent de tec tors

Detector typeSensitivity

[cm–2 kBq–1 h–1]

LR–115 1.10 ± 0.13

Polycarbonate 0.52 ± 0.05

CR–39 (5 hours pre-etching) 0.80 ± 0.11

CR–39 (10 hours pre-etching) 3.0 ± 0.4

CR–39 (heavy pre-etching at 70 °C) 6.6 ± 1.6


ence of their re sponse. In ci dentally, the prob lem ofthe strong an gu lar de pend ence of the polycarbonate neu tron do sim e ter could be solved by us ing [25]elec tro chem i cally etched polycarbonate test tubesor small bot tles. These con tainer types of de tec torscould be of in ter est also for their use as bare de tec -tors for ra don and its de cay prod ucts. It is pos si bleto have de tec tors of any shape (of ten al ready avail -able as con sumer prod uct), which makes the elec -tro chem i cal etch ing of polycarbonate a de tec torwith unique char ac ter is tics.

AC KNOWL EDG EMENTS

The sup port from Dr. S. P. Tripathy for theed it ing of this pa per has been highly ap pre ci ated.

REFERENCES

[1] Tommasino, L., Elec tro chem i cal Etch ing of Dam -aged Track De tec tors by H. V. Pulse and Si nu soi -dal Wave forms, Re port N° RT/PROT (71) 1970,Comitato Nazionale Energia Nucleare, Rome;also Ital ian Pat ent N° 51929 A/70

[2] Grif fith, R. V., Hankins, D. E., Gammage, R. B.,Tommasino, L., Wheeler, R. V., Re cent De vel op -ment in Per sonal Neu tron Do sim e try, A Re view,Health Phys., 36 (1979), pp. 235-260

[3] Sohrabi, M., The Am pli fi ca tion of Re coil Par ti cleTracks in Poly mers and its Ap pli ca tion in FastNeu tron Per sonal Do sim e try, Health Phys., 27(1974), pp. 598-602

[4] Cart wright, B. G., Shirk, E. K., Price, P. B., A Nu -clear-Track-Recording Poly mer of Unique Sen si -tiv ity and Res o lu tion, Nucl. Instrum. Methods, 153(1978), pp. 457-461

[5] Tommasino, L., Zapparoli, G., Djeffal, S., Cross,W. G., Pro ton- and Neu tron-Registration byChem ically and Elec tro chem i cally Etched CR-39De tec tors, Pro ceed ings, 5th Sym po sium onNeutron Do sim e try, Mu nich/Neuherberg, Sep -tem ber 17-21, 1984, CEC Radiat. Pro tect., EUR9762 EN, pp. 469-475

[6] Cross, W. G., Arneja, A., Ing., H., The Re sponseof Elec tro chem i cally-Etched CR-39 to Pro tons of10 keV to 3 MeV, Nucl. Tracks Radiat. Meas., 12,(1986), pp. 649-653

[7] Zapparoli, G., Tommasino, L., Djeffal, S.,Maiorana, A., Ad di tional Re sults with Elec tro -chem i cally Etched CR-39 Neu tron Dosime ters,Nu clear Tracks, 12 (1986), pp. 675-678

[8] Tommasino L. Fu ture De vel op ments in EtchedTrack De tec tors for Neu tron Do sim e try, Rad.Prot. Dos., 20 (1987), pp. 121-124

[9] Tommasino, L., Dam age Track De tec tors inRadioprotection Do sim e try: A novel Ap proach,Ra di a tion Mea sure ments, 31 (1999), pp. 395-400Pat ent Pend ing N° 1300503

[10] Fleischer, R. L., Price, B. P., Walker, R. M., Nu -clear Tracks in Solids: Prin ci ple and Ap pli ca tions.Univ. of Cal i for nia Press, Berke ley, USA, 1975

[11] Bart lett, D. J., Steel, J. D., The NRPB CR-39 FastNeu tron Per sonal Do sim e ter, Pro ceed ings, 6th Int. Congr. Int. Radiat., 1984, pp. 1111-1115

[12] Grif fith, R.V. Tommasino, L., Etch Track De tec -tors in Ra di a tion Do sim e try, in: Do sim e try ofIon izing Ra di a tion (Eds. K. Kase, et al.), Ac a -demic Press, Inc., Vol. 3, 1991, pp. 323-426

[13] Al-Najjar, S. A. R., Bull, R. K., Durrani, S. A.,Elec tro chem i cal Etch ing of CR-39 Plas tic: Ap pli -ca tions to Ra di a tion Do sim e try, Nucl. Tracks, 3(1979), pp. 169-172

[14] Espinoza, G., Gar cia, G., Golzarri, J. L.,Tommasino, L., Raponi, F., Elec tro chem i cal Etch -ing Reg is tra tion and Track-Formation Time, Pro -ceed ings, 11th Con fer ence on Solid StateNuclearTrack De tec tors (Eds. P. H. Fowler, V. M.Clap ham), Bris tol, 1981, Pergamon Press, Ox -ford, pp. 241-245

[15] Tommasino, L., Track Reg is tra tion: Etch ing andCounting Methods for Nu clear Tracks, in: Ra donMea sure ments by Etched Track De tec tors (Eds. S. A. Durrani, R. Ili}), World Sci en tific, 1997, Sin -ga pore, pp. 129-141

[16] Bart lett, D. T., Hager, L. G., Tan ner, R. J., TheDe ter mi na tion of the Neu tron Com po nent ofCos mic Ra di a tion Fields in Space craft. Pres entedat the 21st In ter na tional Con fer ence on Nu clearTracks in Solids, Dehli, Oc to ber 21– 25, 2002

[17] Domanski, B., Chruscielewski, W., Swiatnicki, G., The Performance of Pas sive Dif fer en ti ating TrackDe tec tors Con taining a Dif fu sion Bar rier, Radiat.Prot. Dosim., 2 (1982), pp. 27-33

[18] Dajko, G., Turek, K., Elec tro chem i cal Etch ing ofCR-39 De tec tors Ir ra di ated with Al pha Particles,Nucl. Tracks Radiat. Meas., 16 (1989), pp.241-246

[19] Wrenn, M. E., Rosen, J. C., Van Pelt, W. R.,Steady State So lu tions for the Dif fu sion Equa -tions of Ra don-222 Daugh ters, Health Phys ics, 16(1969), pp. 647-656

[20] Bigazzi, G., Hadler, J. C., Paulo, S. R., On In doorRa don Con tam i na tion Mon i toring withSSNTDs: Ex per i men tal Re sults Con cern ingPlate-Out and Self-Plate-out Ef fects, Nucl.Instrum. and Methods in Phys ics Re search, A280(1989), pp. 506-509

[21] Hadler, J. C., Iunes, P. J., Osorio, A. M., Paulo, S.R., The In flu ence of the Size of Ma te rial Sur faceson Ra don Daugh ters Plate-Out, Nucl. Instr. andMethods in Phys ics Re search, A313 (1992), pp.290-294

[22] Hadler, J. C., Paulo, S. R., In door Ra don Daugh -ter Con tam i na tion Mon i toring: The Ab so lute Ef -fi ciency of Cr-39 Taking into Ac count thePlate-Out Ef fect and En vi ron men tal Con di tions,Rad. Prot. Dos., 51 (1994), pp. 283-296

[23] Brager, G. S., Revzan, K. L., Trans port and De po -si tion of In door Ra don De cay Prod ucts. II In flu -ence of En vi ron men tal Con di tions, At mo sphericEn vi ron ment, 25B, 3 (1991), pp. 359-368

[24] Card, J. F., Bell, K., Ra don De cay Prod ucts andtheir Ap pli ca tion to Ura nium Ex plo ra tion, TheCa na dian Mining and Met al lur gi cal Bul le tin, De -cem ber 1979, pp. 1-7

[25] Lounis, Z., Cavaioli, M., Tommasino, L., TheCom bined Use of Bub ble Dosemeters and Elec -tro chem i cally Etched Track De tec tors, Rad. Prot.Dos., 59 (1995), pp. 299-302; Ital ian Pat entENEA N° 49495/A/77


Lui|i TOMASINO

PROCESI ELEKTROHEMIJSKOG RAZVIJAWA DETEKTORAZA REGISTROVAWE NEUTRONA I PRODUKATA

RADIOAKTIVNOG RASPADA RADONA

Usled svoje sloènosti, elektrohemijsko razvijawe od interesa je kada omogu}ava da sedostignu svojstva detekcije koja hemijsko razvijawe ne obezbe|uje. Ove jedinstvene okolnosti moguse, na primer, susresti u li~noj dozimetriji niskoenergetskih neutrona u okolini nuklearnihreaktora, ali i pri detekciji kako niskoenergetskog tako i visokoenergetskog kosmi~kog zra~ewaneutrona na visinama koje odgovaraju civilnom avionskom saobra}aju. Posebno, dovoqno velikiodnos signala i {uma pri merewu kosmi~kog neutronskog zra~ewa moè biti ostvarenkori{}ewem polikarbonatnog paketa ili CR-39 detektora, budu}i da procesi elektrohemijskograzvijawa omogu}avaju da se izvr{i: (a) brzo skenirawe prostranih detektorskih povr{ina i (b)prebrojavawe pomo}u detektorskih parova koincidentnih doga|aja izazvanih tragovima od teknekoliko mikrona.

Detekcija produkata radioaktivnog raspada radona oteàna je usled promene wihovekoncentracije tokom merewa u okolini povr{ine detektora. Polikarbonatni detektori mogubiti korisni u re{avawu ove te{ko}e time {to beleè produkte radioaktivnog raspada radonadaqe od spoqne povr{ine detektora i {to se mogu proizvesti u razli~itoj geometriji i obliku.[ta vi{e, mogu}e je koristiti ve}i broj kombinacija hemijskih i elektrohemijskih koraka uwihovom razvijawu {to nagove{tava nove primene trag detektora za registrovawe neutrona,kosmi~kog zra~ewa i produkata radioaktivnog raspada radona.

elec tro chem i cal etching pro cesses for the de tec … · elec tro chem i cal etching pro cesses...

Documents