Electrolytic Preparation of Isotopically Enriched Hard Chromium Layers on Gold Backings for Nuclear Reaction Studies

Abstract

The chemical forms of chromium, employed as target material in the study of nuclear reactions, consist of Cr 2 O 3 1 and Cr, 2-7 also in the case of isotopically enriched chromium. [8][9][10][11] Both the chromium metal and the sesquioxide are thermally very resistent. 12 Generally the metallic chromium targets are preferred for two reasons; first, no other interfering elements are present and second, chemical processing of the irradiated targets is easier. The nonnoble metal (⑀ 0 ϭ Ϫ0.74 V, nonpassivated 12 ), however, is easily oxidized on the surface to sesquioxide at high local temperatures induced by high beam currents. Since the sesquioxide is insoluble in mineral acids, there may be a leaching problem at the start of the chemical processing. Especially if isotopically enriched chromium is used as the target, the losses of the enriched material due to the unleached sesquioxide have to be avoided because a quantitative recovery is mandatory. In nuclear reaction studies low beam currents are sufficient and thus metallic chromium targets are most suitable.Thin metallic chromium layers can be achieved by electrodeposition and chemical vapor deposition (CVD). 13-16 The latter procedure, however, is rather cumbersome. Although the electrodeposition of metallic chromium has been a well established procedure for about 70 years, it was essential to investigate whether this procedure could be adapted to low chromium concentrations. In this context the recently developed Cr III baths seemed to be very promising since Cr III is easily prepared and handled at low chromium concentrations. As regards the reprocessing of the enriched material, electrolytes used in electrodeposition should enable a simple and complete recovery of the enriched chromium. An exact analysis of the chromium content of the electrolyte was also desired to adjust the chosen concentrations for optimum depositions.Batch electrodeposition.-Electrolytes based on chromic acid "CrO 3 aq" are very commonly used. 13,[17][18][19][20][21][22] The Cr III baths became more promising only in recent years. [23][24][25][26] They are prepared by the addition of complexing agents such as carboxylic acids, 27,28 polycarboxylic acids 29 or cyanide derivatives, 30 but only a few fundamental investigations on the mode of operation of these new baths have been done. 29,31 Little is known about the chemical reactions in the interface between electrolyte and cathode, only thin layers can be achieved out of trivalent baths, which are useful only in decorative electroplating, 32 although efforts are under way to achieve a hard chromium plating. 33 Since just thin targets are needed in nuclear data measurements, the trivalent alternative was investigated first. However, both the citrate and the ethylenediamine tetraacetic acid (EDTA)-based trivalent baths in the pH range of 2 to 3 at 313 K did not yield deposits thicker than 0.5 mg cm Ϫ2 within 15 min of electrodeposition at about 100 mA cm Ϫ2 . This thickness was not sufficient even for nuclear reaction cross-sectional meas...

Cross-section measurements for the formation of manganese-52 and its isolation with a non-hazardous eluent

“…Relatively thin foils of elemental chromium are not commercially available, due to its brittle nature. Therefore thin target layers were prepared by an electro-deposition method of Fessler et al [12], as a newer electro-deposition method by Klein et al [6] did not prove to be reproducible.…”

“…β + -energy: 575 keV) are promising candidates. Extensive studies have been carried out in our Institute on 51 Mn [6][7][8][9]. In this work we concentrate on 52 Mn.…”

Investigation of 50Cr(d,n)51Mn and natCr(p,x)51Mn processes with respect to the production of the positron emitter 51Mn

“…The electrolyte was obtained by dissolution of the trioxide Table 2 (for more details cf. [12]). The chromium depositions were washed with water and acetone and finally air dried.…”

“…by spectrophotometric determination of chromate in the Cr-fraction (cf. [12]). The amount of chromium obtained by this method was used to calculate the plane weight and the thickness of the 50 Cr°target layer.…”

Production of the positron emitter 51Mn via the 50Cr(d, n) reaction: targetry and separation of no-carrier-added radiomanganese

“…Fig. 1) [31]. The production cycle started with one of the two available chemical forms of 50 Cr, the metal or the sesquioxide (for details cf.…”