Ⅱ-9. Instrumentation
RIKEN
Accel. Prog. Rep. 56 (2023)

RIKEN Accel. Prog. Rep. 56 (2023)

The extraction test aiming for the laser spectroscopy of actinoid
elements by PALIS
T. Sonoda,∗1 V. Sonnenschein,∗2 H. Iimura,∗3 H. Miura,∗2 Y. Hirayama,∗4 D. Hou,∗4 S. Iimura,∗1 H. Ishiyama,∗1I. Katayama,∗1 T. M. Kojima,∗1 S. Nishimura,∗1 M. Rosenbusch,∗3 A. Takamine,∗1 H. Tomita,∗2 M. Wada,∗4Y. X. Watanabe,∗4 W. Xian,∗4 J. M. Yap,∗4,∗5 and BigRIPS Collaborators∗1The laser spectroscopy of actinide RIs oﬀers an opportunity to study atomic/nuclear structure in termsof relativistic eﬀects, nuclear shell eﬀects, deformations
etc. The BigRIPS provides a wide variety of actinide
RI-beams by using in-ﬂight projectile fragmentation ofuranium. In this year, we were granted 24 hours beamtime for the extraction test of actinide isotopes and simultaneously performing a commissioning test for thelow-energy RI-beam production system by laser ionization(PALIS),1) in a director’s beam times.
During the beam time, the BigRIPS optics weretaken over from the previous beam user’s setup. Themain beam optics was 225 Ac (T1/2 = 10 d), which wasexpedient for the extraction test of actinides. Howeveras the half-life of 225 Ac was too long to measure for ourexperimental setup, we fully opened the F1 slits at BigRIPS to obtain more yield of the relatively short-lived223
Ac (T1/2 = 2.1 min). Figure 1 shows the expected
RI-beams and its intensity which were implanted to thePALIS gas cell, simulated by LISE.

219Pa 220Pa(53ns)
216Th(0.78us)217Th 218Th 219Th

222U

223U

224U

225U

226U

227U

228U

229U

230U

(1.0us)(18us)(0.7ms)(61ms)(0.35s)(1.1m)(9.1m)(58m)(4.2d)

221Pa

222Pa

223Pa

224Pa

225Pa

(5.9us) (2.9ms)(5.1ms) (790ms) (1.7s)

220Th 221Th 222Th 223Th 224Th(26.0ms) (251us) (117ns) (1.05us) (9.7us) (1.73ms) (2.24ms) (600ms) (1.05s)
214Ac

215Ac 216
Ac

(8.2s)(0.17s)(440us) (69ns)

213Ra 214Ra 215Ra(2.74m) (2.46s)
211Fr

212Fr

213Fr

(3.10m) (20.0m) (34.6s)

217Ac 218Ac

221Ac(1.08us) (11.8us) (26.4ms) (52ms)

216Ra 217Ra 218Ra 219Ra(1.55ms) (182ns)(1.6us) (25.2us) (10ms)

214Fr 215Fr

216Fr(86ns)(700ns)(5.0ms)219Ac 220Ac

217Fr(19us)

209At

210At

211At

(1.63h)(5.41h)(8.1h)(7.2h)

207Po

208Po

209Po

210Po 211Po 212Po(5.80h) (2.898y) (102y)(138d) (516ms) (294.7ns)

212At 213At 214
At 215At(314ms) (125ns) (588ns) (100us)(1.8m)(38.3m)(22h)(8.75m) (30.57m) (18.7d)

222Ac 223Ac 224Ac

225Ac 226Ac(5.0s)(10.0d) (1.224d)(2.1m)

229Pa 230Pa

231Pa

232Pa

(1.50d) (17.4d) (3.3x104y) (1.32d)

225Th 226Th 227Th 228Th 229Th(2.78h)(1.9y)(7920y)220Ra 221Ra 222Ra 223Ra 224Ra(18ms)

(28s)

(38s)

218Fr 219Fr 220Fr 221Fr(1.0ms) (20ms) (27.4s) (4.77m)

209Rn 210Rn 211Rn 212Rn 213
Rn 214Rn 215Rn 216Rn 217Rn 218Rn(28.5m) (2.4h) (14.6h) (23.9m) (25.0ms) (0.27us) (2.3us) (45us) (540us) (35ms)
208At

226Pa 227Pa 228Pa

231U 232U 233U 234U
(68.9y) (2.4x105y) (1.6x105y)(2.4x105y)

Laser
Gas cellQuadruPole Ion Guide

SextuPole Ion Guide
Alpha counting

~70cm

Exit

Differential pumping
Silicon detector

Ar 300mbar
Rotational degrader

Fig. 2. PALIS experimental setup.

Figure 3 shows the energy spectra of detected alpha particles, taken with a primary beam intensity of
10 particle nA and implantation/measurement periodof 300 s each. The rate enhancement of the alpha counting by laser eﬀect was not clearly conﬁrmed, implyingthat the extracted alpha emitters were ions that survived against neutralization inside the gas cell. The insensitivity of the laser eﬀect is attributed to the impossibility of identifying only 223 Ac from the superimposed
α-ray’s spectra by many types of α emitters, which hindered the optimization of the proper degrader thicknessfor 223 Ac. In addition, the evaluation of laser eﬀect wasdistorted by other alpha-rays. Next we will utilize aprecise mass identiﬁcation device for extracted RIs.

(11.43d) (3.66d)

main beam

Alpha counts
70

alpha decay>105cps60>10000cps>1000cps50>100cps>10cps40

Fig. 1. Expected RI-beams and its beam intensity (primarybeam 1 particle nA, fully opened F1 slits) by LISE.

Implantation time 300s
Measurement time 300s

3020To conﬁrm the low-energy RI-beam extraction, the αrays produced via α decays were detected at the silicondetector, which was placed in the diﬀerential pumping
area at the PALIS, as shown in Fig. 2. The stopped
and extracted RIs from the gas cell were transported
through the sextupole and quadrupole ion beam guides,
respectively, and then deposited to the surface of thesilicon detector. To reduce the background, the beam
was stopped during α-ray measurement.
∗1∗2
∗3
∗4
∗5RIKEN Nishina Center
Faculty of Engineering, Nagoya University, Nagoya
Japan Atomic Energy Agency
Wako Nuclear Science Center (WNSC), IPNS, KEK
Department of Physics, University of Hong Kong

1000200

400

600

800

1000

1200

ADC channel (the silicon detector) (ch)Fig. 3. Observed alpha spectra at silicon detector.

We successfully observed the extracted RIs as a lowenergy RI-beam. The eﬃciency improvement and theinstallation of the mass identiﬁcation are in progress.
Reference1) T. Sonoda et al., Prog. Theor. Exp. Phys. 113, D02(2019).

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