2626Al and Al and 3636Cl AMS system at the University of
Tsukuba: A progress repor t Cl AMS system at the University of
Tsukuba: A progress repor t Kimikazu Sasa1), Yasuo Nagashima1),
Tsutomu Takahashi1), Riki Seki1), Yuki Tosaki1), Keisuke
Sueki1),
Kotaro Bessho2), Hiroshi Matsumura2) Taichi Miura2) and Ming
He3)
1) AMS Group, Tandem Accelerator Complex, Univer sity of
Tsukuba, 1-1-1 Tennoudai, Tsukuba, Ibaraki, 305-8577, Japan2)
Radiation Science Center , High Energy Accelerator Research
Organization, 1-1 Oho, Tsukuba, Ibaraki, 305-0801, Japan3) Depar
tment of Nuclear Physics, China Institute of Atomic Energy, 102413,
Beijing, 275(49), China
IntroductionThe present status of the Tsukuba AMS system on the
12UD Pelletron tandem accelerator is
r epor ted. At present, long lived radioisotopes of 26Al, 36Cl
and 129I are able to be measured by the Tsukuba AMS system. After
the AMS-9 conference, several effor ts have been paid on the 26Al
and 36Cl-AMS system in order to impr ove the per for mance. Several
improvements have been applied on the AMS beam line, so that
36Cl-AMS is able to be per for med with 10 MV ter minal voltage
instead of 9 MV. Therefore, the energy of the 36Cl9+ beam increases
from 90 MeV to 100 MeV. This energy increment helps us to get more
clear separation between 36Cl and 36S.
UTTAC Japan
Tsukuba science city University of Tsukuba
NEC 12UD Pelletron tandem accelerator (1975)University of
Tsukuba, Tsukuba, Japan.・MODEL : Vertical Tandem Van de
Graaff・Terminal voltage range: 2.0 - 11.0 MV・Insulation Gas : SF6
pressure: 0.6 MPa・Accelerator Tank : Height: 17.9 m
Diameter: 4.8 mVolume : 350 m3Total weight: 120 ton
・Analyzing Magnet : ME/Z2=200 amu MeV
Tandem Accelerator Complex
Corresponding author: Kimikazu [email protected]
Accelerator Complex,Research facility Center for Science and
Technology,University of Tsukuba,Tsukuba, Ibaraki,
305-8577,JapanTel: +81-29-853-2494Fax:+81-29-853-2565Summary of
36Cl-AMS
As a result of these improvements, the detection efficiency of
36Cl increased to 1.5 times and the discr imination between 36Cl
and 36S was much impr oved. Over all accuracy is ±3% and the
effective detection limit is r eached to 2 10−14 for 36Cl/35Cl
ratio.
46.5 m
9th floor
7th floor
5th floor
Ion sour ce r oom
4th floor
Accelerator room
1st target room 2nd targer room
SF6 SF6
41.6 m
AMS-IS120 -magnetIon Source
(25samples) 35Cl-FC
EQ
Analyzer magnet
Stripper foil
45 -magnet
8 -electrostatic deflector
SW
AMS-beam line
QMQM
ST ST
ST
2nd stripper foil
Object slit
Inflection magnet
ESEQ
ES
QM
ST
ST
Image slit
TOF chamber
E- E detector chamber
12UD Pelletron tandem accelerator
ES : E lectrostatic steerer EQ : Electrostatic quadrupole (tr
iplet) QM: Quadrupole magnet (doublet) ST : Magnetic steer er SW :
Switching magnet
SWQM QM
Accelerator facility
Tsukuba AMS system (36Cl-AMS)
36Cl-AMS
AMS data analysis
New target corn
Diameter of a sample pocket: 1mmSample: AgCl 1 5mgTa sheet
In order to reduce 36S influence.
Ta sheetAｌ corn
AgCl sample
2mm0
Cross sectional view of the target corn
EQ
Analyzer magnet
Stripper foil
Object slit
ES
QM
ST
12UD Pelletron tandem accelerator
BPM:Beam profile monitor ES : Electr ostatic steer er EQ :
Electrostatic quadrupole (tr iplet) FC : Faraday cup QM :
Quadrupole magnet (doublet) ST : Magnetic steer er SW : Switching
magnet
AMS-IS
36Cl-
35Cl-FC
115kV37Cl-FC
15 kV
Inflection magnet
120magnet
Ion Source (25 samples)
FCEQ ES
ESEinzel
AMS-beam line
45 -magnet8 -electrostatic deflector
SW QMQM
ST
ST
2nd stripper foil
Image slit
E- E detector chamber
ST
36Cl- 12Cl3-
36Cl9+ (100MeV) 12Cl3+
VT=10 MV
36Cl14+ (100 MeV)
36Cl- 12Cl3-
BPM FC
FC
BPM
BPM FC
FC
A new E-E detector
36Cl14+(100MeV)
Aramid film4 m
Iso-butane 670 Pa
SSD 300 m45 45mm2
ΔE1ΔE2
Double gas E sections (2004 - )ΔE1 gateΔE2 gate
A gasΔE - SSD E counter telescope
Non gateΔE1 gateIn order to reduce 36S influence
AMS beam line
45 magnet
2nd str ipper foil
8 electrostatic deflector
A new E-E detector
AcknowledgementThis work is suppor ted in par t by the
Grand-in-Aid for Scientific Research of the Ministry of Education,
Science,
Spor ts and Culture of Japan.
Summary of 26Al-AMS26Al-AMS has also progressed in AMS
technique. The ions extracted from the ion source were changed to
26AlO− ions from 26Al− because several advantages would be
expected. 26MgO− molecular ion is used as the pilot beam. After
passing through the accelerator at 10.2 MV, 26Al7+ and 26Mg7+ with
the energy of 77.7 MeV are selected by the analyzing magnet. 26Al7+
ions are changed to full str ipped 26Al13+ ions by a second charge
exchange foil and then they are separated by the following energy
and momentum selector s. The effective detection limit is reached
to better than 5.8 10−15 for 26Al/27Al ratio.
Instead of the GVM stabilizer , a slit cur rent feedback control
system is used as a terminal voltage stabilizer . A molecular pilot
beam method is applied to stabilize the ter minal voltage. The ter
minal voltage is kept stably within 0.1% accuracy by this method. A
tr i-carbon molecular , 12C3− ion is used as the pilot beam for
36Cl-AMS. It is impor tant to reduce the strong 36S isobar ic inter
ference on 36Cl measurements.
0.0001
0.001
0.01
0.1
1
0 10 20 30 40 50 60
Charge fraction F(q) of 90MeV 35Cl9+ emerging from a ca rbon
foil
891011121314151617
10
100
1000
1 10
by C.J .Sofield et al., 1984 This work35Cl + C
The optimum thickness of 2nd str ipper foil:About 12-15 g/cm2
[F(14+)]
C-foil [ g/cm2]
Cha
rge
frac
tion
Incident energy of 35Cl [MeV/u]
Cha
rge
equi
libri
um th
ickn
ess
Teq
[g/
cm2 ]
2nd str ipper foilWe measured the charge state distr ibution of
35Cl and 37Cl ions after the passage thr ough a carbon
foil in order to optimize the thickness of 2nd str ipper
foil.
Foil thickness attaining charge equilibr ium:over 100 g/cm2
35Cl [100MeV]
Automatic sample changer(25 samples on the rotating wheel)
AMS ion source
115 kV35Cl- -FC
EQ
120 -magnet
Slit ESSputter ing ion source
Automatic sample changer
Incidence 35Cl9+ 37Cl9+ foil C 108 g/cm2 C 108 g/cm2 Incident
energy 90 MeV 95.026 MeV Exit energy 87.948 MeV
2.5128 MeV/u 92.974 MeV 2.5128 MeV/u
dE/dx 19.0 MeV/(mg/cm2) 19.0 MeV/(mg/cm2) F(11+) 0.01080 0.01079
F(12+) 0.06704 0.06752 F(13+) 0.2163 0.2143 F(14+) 0.3494 0.3514
F(15+) 0.2941 0.2932 F(16+) 0.05876 0.05877 F(17+) 0.003655
0.003979 Mean charge qb 14.04 14.041 Distribution width 1.069
1.0695
Isotope dependence of equilibr ium charge states of 35Cl and
37Cl ions passing thr ough a car bon foil
Equilibr ium char ge distr ibutions of 35Cl and 37Cl ions after
the passage thr ough a carbon foil have been measured. Results show
that the isotope effect of charge distr ibutions between 35Cl and
37Cl ions has not been obser ved when they are compared at equal
exit energy.
Sample preparation
Str ipper foil4mm
6mm8mm
12mm
5mm15mm
I-MagObject pointemittance
EQ1-2 EQ3-4
X-plane
Y-plane
(x, x’)=(y, y’)=(1.5mm, 10mrad)
Beam envelope
Terminal pointemittance
36Cl- beam transpor t
We improved the accelerator tr ansmission from 30% to 60% .
E
New Terminal
Str ipper foils at the terminal36Cl- ⇒ 36Cl9+ (A/q=4)12C3-⇒
12C3+ (A/q=4)
Sample: 1 5 g A few mg of AgCl sample
Sample (10–20 mL)
Centrifugation (2500 rpm, 10 min)
13 M HNO3 (1 mL)
Precipitate (AgCl)
0.3 M AgNO3 (1 mL)
30% H2O2 (1 mL)
Supernatant
3 M NH4OH (2 mL) sat. Ba(NO3)2 (3 mL)
Filtration (Filter Paper)
Precipitate (BaSO4)Filtrate ([Ag(NH3)2] Cl )
Drying (130 C, 3 h)
Washing (with 0.01 M HNO3, 2 times)
13 M HNO3 (0.5 mL)
Washing (with 99.5% C2H5OH)
Sulfur Reduction (2 times)
Centrifugation (2000 rpm, 15 min)
Precipitate (AgCl)Supernatant
Sample (10–20 mL)
Centrifugation (2500 rpm, 10 min)
13 M HNO3 (1 mL)
Precipitate (AgCl)
0.3 M AgNO3 (1 mL)
30% H2O2 (1 mL)
Supernatant
3 M NH4OH (2 mL) sat. Ba(NO3)2 (3 mL)
Filtration (Filter Paper)
Precipitate (BaSO4)Filtrate ([Ag(NH3)2] Cl )
Drying (130 C, 3 h)
Washing (with 0.01 M HNO3, 2 times)
13 M HNO3 (0.5 mL)
Washing (with 99.5% C2H5OH)
Sulfur Reduction (2 times)
Centrifugation (2000 rpm, 15 min)
Precipitate (AgCl)Supernatant
A benzene saturated solution of Fullerene (C60) for 12C3- pilot
beam. [7.6 l / AgCl: 1 mg]
FC
Switching mag.
Analyzing mag.
Inflection mag.
AMS ion source
27AlO-
Vt=10.2MV
26MgO-26AlO-
26Mgn+26Alm+
1st Str ipperfoil
120°mag.
26Mg7+26Al7+(77.7 MeV)
2nd str ipperfoil (40 g/cm2)
ΔE-E detector
45°mag.
26Al13+
26Mg7+Slit curr ent feedback
26Mg n’+ (m’ 12)26Alm’+ (n’ 13)
deflector（8°）
Outline of 26Al-AMS
26Al is very clear ly separated from 26Mg with the detector
.Upper limit of the 26Al-AMS sensitivity: 5.8×10-15
Full str ipping technique:26Al13+/27AlO- [counts/ C]Pilot beam:
26MgO-Beam cur rent of AlO-from Al2O3 sample : 1.5 A
E- E
Standard sample (36Cl/35Cl =6.5×10-12)
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0 10 20 30 40 50 60 70 80 90 100
Run No.
36C
l /35
Cl (
coun
ts/μ
C)
No. 18No. 20No. 18
Standard sample: 36Cl / 35Cl=5.9 10-113 minutes measurement
36Cl-AMS measurement: 36Cl14+/35Cl- [counts/ C]Pilot beam:
12C3-Beam cur rent of Cl- from AgCl sample: 20 A
Equilibr ium charge fraction of 35Cl ion after passage through a
carbon foil. [by Shima et al., ]
26Al-AMS
Charge fraction F(q) of 35Cl9+ increased 1.5 times from 20% to
30% .
The standard deviation of the fluctuation of the 36Cl/35Cl ratio
is kept within 3%
26Al13+
26Mg12+26Mg11+ 1054 counts
Standard sample26Al/27Al=7.44 10-115 minutes measurement
Blank sample80 minutes measurement
26Al
No count
Standard sample26Al/27Al=4.69 10-1210 minutes measurement
26Al
99 counts
Standard sample26Al/27Al=4.99 10-1310 minutes measurement
26Al
16 counts
36Cl
36S
7777counts
2330 counts
9MV 10MV
E [MeV]
E- E
E
After the AMS-9 conference, 36Cl-AMS is able to be per formed
with 10 MV ter minal voltage instead of 9 MV.
