Ⅲ-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 53

Preparation of Gd targets for in-beam fission measurements as a step
towards the handling of 243 Am targets with ultra-thin backings
T. Tanaka,∗1,∗2 D. J. Hinde,∗1,∗2 H. Haba,∗2 M. Dasgupta,∗1,∗2 S. Battisson,∗1 A. C. Berriman,∗1 L. T. Bezzina,∗1J. Buete,∗1 I. P. Carter,∗1 K. J. Cook,∗1 E. Graham,∗1 J. Heighway,∗1 T. D. Hume,∗1 D. Y. Jeung,∗1 Y. Komori,∗2P. McGlynn,∗1 D. Mori,∗2 S. A. Parker-Steele,∗1 C. Sengupta,∗1 C. Simenel,∗1 E. C. Simpson,∗1 M. A. Stoyer,∗1,∗3B. M. A. Swinton-Bland,∗1 Y. Wang,∗2 W. Wojtaczka,∗1 and T. Yokokita∗2Table 1. Combinations of backing material, thickness andsubstrate.
Backing material
TiCrAl∗1∗2∗3a)

Thickness
200 nm
300 nm
300 nm
300 nm
740 nmSubstrate
Cu(3.6–4.7 µm)
KI-coated glass
Cu (3.8–4.4 µm)
self-supporting

160
58

140
120
Counts

The study of in-beam ﬁssion characteristics is of fundamental importance in understanding heavy-ion induced fusion reactions and the shell structure of ﬁssioning nuclei. Characteristic information is extracted fromthe measured velocities of the ﬁssion fragments. Since
the fragments lose kinetic energy when passing throughthe target and/or backing to reach the detectors, thinner targets and backings are favored for studies to decrease the systematic error. Additionally, safe handlingand survival of radioactive isotope (RI) targets in beam
are important factors. Since thinner targets and backings are fragile, the optimization of the backing material,
thickness and preparation procedures are key for studies
with RI targets.
In order to ﬁnd the optimum backing, a variety ofbackings with diﬀerent material, thickness, and substrate, were prepared, as indicated in Table 1. As thethin backings are too thin for electrodeposition of theRI target, a substrate such as Cu is used to support thebacking during electrodeposition, and is subsequently removed. The Ti and Cr materials were evaporated using an evaporator at ANFF. a) The Cu substrates weredissolved by a solution made by combining 4 grams oftrichloroacetic acid (TCA), 20-mL 30% NH3 solution
and 20-mL deionized water, resulting in 40-mL of 9.3%
TCA solution, similar to that described in Refs. 1–3).
The success ratios for dissolving the Cu without breaking the backing materials were more than 80% for Ti
backing material and less than 50% for Cr backing material. Attempts to release the Ti-backings from KI-coatedglass by dissolving potassium iodide in water were notsuccessful because the backings were broken.
As a backing test, the backings, 200-nm Ti, 300-nm
Ti, and 300-nm Cr (once removed from the Cu sub-58

Ni+27Al

100806040200500 1000 1500 2000 2500 3000 3500 4000
Energy (ch)Fig. 1. Energy spectrum measured by a Si detector from thereaction of 58 Ni + nat Gd with Al backing.

strates), were irradiated by a 170 MeV 58 Ni12+ beam of1 mm diameter, which was provided by the Heavy Ion
Accelerator Facility of the Australian National University. The 300-nm Ti backing survived beam irradiationof 1.5 enA for more than one hour.
Gd target material, instead of RI 243 Am, was successfully deposited on Ti-backing and Al-backing by electrodeposition utilizing the Hot-Lab of RIKEN Nishina
Center. The detailed procedures are similar to that described in Ref. 4). The thicknesses of 1.6-mm-diameter(5-mm-diameter) Gd targets were between 130 and 190(40 and 120) µg/cm2 .
The Gd targets on 300-nm-Ti/740-nm-Al backings
were tested with the same conditions as the backing test.
An energy spectrum measured by a Si detector, which
was mounted 15 cm downstream of the target at 18◦ withrespect to the beam axis, is indicated in Fig. 1. The clear
peaks indicate the elastic scattering from the reactionsof 58 Ni + nat Gd and 58 Ni + 27 Al, which demonstrate
the uniformity and quality of the target and backing.
The safety of all of procedures for handling the target, as well as the uniformity and quality of the target,
have been conﬁrmed. The 243 Am target will be preparedusing the same procedures as the Gd targets.
References

Department of Nuclear Physics, The Australian National University
RIKEN Nishina Center
Lawrence Livermore National Laboratory
Australian National Fabrication Facility, ANU node

Ni+natGd

1) G. T. J. Arnison, Nucl. Instrum. Methods Phys. Res. 53,357 (1967).
2) B. Lommel et al., Nucl. Instrum. Methods Phys. Res. A655, 44 (2011).
3) M. A. Stoyer et al., LLNL-TR-752862 (2018).
4) Y. Kudou et al., RIKEN Accel. Prog. Rep. 42, 265 (2009).

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