TCHoU 26 Nov. 2021

蓄積リングを用いたRIの質量測定に関する研究
Research of nuclear mass measurements
for radioactive isotopes with storage ring
鈴木伸司 (Shinji Suzuki)

University of Tsukuba

Contents● Nuclear masses● Methods of nuclear mass measurement● Detector developments● Mass resolution

Nuclear masses
mass → binding energy → interaction

Nuclear mass = N ×+Z×- Binding energy

Field of application
Chemistry: identification of molecules
Nuclear physics: shells, sub-shells, pairing
Nuclear fine structure: deformation, halos✔ Astrophysics: r-process, rp-process
Nuclear models and formulas: IMME
Weak interaction studies: CVC hypothesis, CKM unitarity
Atomic physics: binding energies, QED

K. Blaum, Physics Reports 425, 1 (2006)

Requireduncertainty
10−5–10−6
10−6
10−7–10−8
10−7
10−7–10−8
10−8
10−9–10−11

predicted~7000
discovered ~3200
mass known ~2500<100keV~2300

sserocr-p

AME2016
Chinese Physics C, 41, 030001 (2017)

Mass uncertainty [keV]

Mass uncertainty

Mass prediction
Sp=0

r-process

Sn=0

K. Blaum,Physics Reports,425 (2006) 1-78.

Cs isotopes

Masses of radionuclides should be measured

Methods of nuclear mass measurement
Penning trap

Storage ring

1 Δ(m /q)
γ 2 Δv
ΔT= 2− 1− 2Tγt m /qγt ) v(Isochronous mass spectrometry (IMS)

B q
fc =2π m

𝛾21− 2 → 0𝛾𝑡 )(Schottky mass spectrometry (SMS)

Δ𝑣
→ 0𝑣

Multi-reflection TOF (MR-TOF)

Bρ TOF

T(n) = T(0) + n ⋅ b m• Time： Bρ-TOF, IMS < MR-TOF < PTMS < SMS• Precision： PTMS > SMS, IMS, MR-TOF > Bρ-TOF
IMS is suitable for short-lived radionuclides

𝐵𝜌 =𝑚𝛽𝛾c𝑞Isochronous mass spectrometry (IMS)First IMS experiment in GSI
Nucl. Inst. Meth A 446 (2000) 569-580
Signals of TOF detector

Double TOF IMSSingal TOF

RIビーム

Revolution time can becorrected by velocity

CSRe(experimental Cooler Storage Ring)C ~ 120 m

T [ns]

Doubel TOF

ΔT1 Δ(m/q)
γ 2 Δv= 2− 1− 2T
γt m/qγt ) v(γ = γT~18 m

Two TOF detectors (T, v)
T [ns]

Devised in GSI
ion

J. Pays. G 31 (2005) S1779-S1783

Performed in IMPsha1_base64="GHkdpbSUMsU3zE79oTpCnEmnH4w=">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</latexit><latexit

IMS with R3 (Rare RI Ring) in RIKEN

F5RI beamm/q: mass to charge ratio, c: speed of light
0: known-mass nucleus、1: target nucleus

Position-sensitive detector（Bρ）

F3

TOF detector (β, T)

TOF measurement (β) <1μs

Mass determination from T corrected by β/Bρ
TOF measurement (T)~1msextraction

S0

R3
C ~ 60 minjectionParticle identification

IMS in RIKEN∆E [arb.]

IMS with in-ring detector

78Ge77Ga76Zn75Cu
74Ni

Particle identification is based on
the revolution time analysis→ ions having the same A/Z cannot
be identified (e.g. A/Z = 2: 40Ca, 100Sn)

TOF [arb.]
Particle identification can be
performed by using detectors
installed in the beam line

TOF detector using secondary electrons
Requirements• Time resolution < 100 ps (∆β/β<1×10−4)• Good detection efficiency close to 100%
• Must be as thin as possible (∆β/β < 1×10−4)• Detection efficiency• Aluminized Mylar foil (φ45 mm)• B ~ 150 gauss• E ~ 500 V/mm• Time resolution: 38.6(2) ps

S.Suzuki et al., Nuclear Inst. and Methods A 965, 163807 (2020)

10Novel position-sensitive detector
10020MCP size~3×MCP

80706005040−103071.3%−20B = 36 ~ 110 gauss/E = 10 ~ 380 V/mm

9010z [mm]z [mm]

φ1540×15 mm2−30−3020Foil size
−20−100x [mm]102030100Detection efficiency [%]30Detection efficiency [%]change in ion velocity in a position-sensitive detector (PPAC) cannot be ignored (∆β/β~1×10-3)

MCP

Foil301201010080060−10Counts

20Countsx [mm]x [mm]14040−20−30

20−1−0.5

00.5
TF-TB [ns]1Preliminary

0TF-TB [ns]S.Suzuki et al., JPS Conf. Proc. 35, 011017 (2021)

The best position resolution of ~ 0.9 mm
was obtained in about 70 gauss

Basic research for the detector finishedMeasured masses using R3
Phys. Rev. Lett. 114 192501 (2015)

124Ag, 123Pd, 122Rh*
125Ag, 124Pd*, 123Rh*

74Ni*, 76Ni** unknown mass

Analysis is under goingCollaborators
University of Tsukuba
A. Ozawa, T. Moriguchi,N. Kaname, A. Yano
Saitama University
T. Yamaguchi
Kyushu University
D. Nagae
JAEA
F. Suzaki

RIKEN
Y. Yamaguchi, S. Naimi,
Y. Abe, T. Uesaka,
M. Wakasugi
GSI (Germany)
Y. A. Litvinov
IMP (China)
M. Wang, H. F. Li,
Y. H. Zhang