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The GEANT4 Code Some Results From First Experiment Next Approved Experiment · 2018-07-09 · The...
Transcript of The GEANT4 Code Some Results From First Experiment Next Approved Experiment · 2018-07-09 · The...
SpecTAS IThe Setup
The TASCA Separator
* The GEANT4 Code
*
*
Some Results From First Experiment
Next Approved Experiment
*
*
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TASISpec − Setup, Simulations, Results and Future
SpecTAS I
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TASCA − TransActinide Separator and Chemistry Apparatus
Ch. E. Düllmann et al. Phys. Rev. Lett. 104, 252701 (2010)
Dipole
UNILACbeam
Target Qua
drup
ole
Qua
drup
ole
2005 Built
2006−2008 Commissioned
2009 Z=114 produced and identified
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The TASCA Separator at GSI
Two available transmission modes
(35 4)%
A. Semchenkov et al. Nuclear Instrum. and Meth. Phys. Res. B 266 4153 (2008).
High Transmission Mode (HTM)
Small Image−size Mode (SIM)
−
+(60 6)%
+
−
J. Gates et al. , submitted to PRC.
SpecTAS I
4 SSSSD (4*32 strips)
1 DSSSD (32+32 strips)
4 Ge Clover (4*4 crystals)
1 Ge Cluster (7 crystals)
TASCA
ER
The Detector Set−up
L−L Andersson et al., Nucl. Instr. and Meth. A 622, 164 (2010)
TASCA in Small Image Mode Spectroscopy
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SpecTAS I
Clover
Clover
Cluster
Clover
Clover
The Detector Set−up
Details of the construction
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The Full TASISpec Setup in Geant4
Programmed (in great detail) by: L. G. Sarmiento
0 200 400 600 800 1000 1200 1400 1600Eγ (keV)
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30
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50S
imul
ated
Abs
olut
e E
ffici
ency
(%
) simulated
experimental
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Comparing Experiment With Simulations
133Ba
152Eu
Relative gamma−ray efficiency with source on holder
(Compare the shape of the two curves)
0 200 400 600 800 1000 1200 1400 1600Eγ (keV)
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60A
bsol
ute
Effi
cien
cy (
%)
simulation with source on holdersimulation with source implanted into the DSSSD
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Comparing Simulations With Simulations
Different gamma−ray efficiency in different positions
133Ba152Eu
0 200 400 600 800 1000 1200 1400 1600Eγ (keV)
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60A
bsol
ute
Effi
cien
cy (
%)
simulation with source on holdersimulation with source implanted into the DSSSDABSOLUTE experimental efficiency
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Comparing Experiment With Simulations
133Ba152Eu
Absolute efficiency comparison!!!
E * E’ m ce2
E’ − E = (1 − cos )θCompton Scattering:
Min
Max
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There are no compton shields in the setup
Limiting Background and "False" Coincidences
2) Cross detector add−back (som combinations are more likely)
The limited geometric angles involved in scattering
gives defined ratios for the two energies!
1) Internal Add−back (between crystals in same detector)
SpecTAS I
*
* Total beam integral 2.4E18
to some 25% of the collected data
207 48Pb( Ca, 2n) No253
Results from a subset of runs, corresponding
* First main beam experiment run in 2010
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The beamtime
5500 6000 6500 7000 7500 8000 8500 9000 α - particle energy (keV)
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12000
Yie
ld (
Arb
itrar
y U
nits
)
249 F
m
253 N
o
245 C
f
211 P
o
211 P
o*
253 F
m
211 B
i
Alpha Particles Detected in the DSSSD
(In total 480 000 alpha from 253No)
some 120 000 alpha particles7.9−8.2 MeV:
DSSSD p−side Beam off alpha spectrum
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7.00 7.20 7.40 7.60 7.80 8.00 8.20 8.40Alpha Energy (MeV)
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15Y
ield
(A
rbitr
ary
Uni
ts)
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0.1
1
10
102
103
104
279
7.63 MeV
20 keV FWHM
221
150
669
Q α = 8.15-8.35 MeVX-rays
Eγ = 667-673 keV
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A. Lopez−Martens et al. Nuclear Physics A, in press.
Gates clearly show new(ish) gamma−ray transition at 669 keV
Alpha decaying 253No
F. Hessberger et al. Eur Phys J. D 45 33 (2007).
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15
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Yie
ld (
Arb
itrar
y U
nits
)
0 100 200Eγ (keV)
0
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163
221
163+58=221
α (58) = 51.4tot
α (71) = 28.4tot
α (129) = 8.3tot
No253
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Generous gate on the 58 keV transition
(Cross addback)
(Internal addback)
(No addback) α
Alpha Gamma−Gamma Coincidences and Addback
58
71129
221279
150
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100
0 100 200 300 400 500 600 700Eγ (keV)
0
50
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Yie
ld (
Arb
itrar
y U
nits
)
399
338
18815
1K
β 1
35,1
37,1
40
K α
1 1
21K
α2
115
109
?
166
?76
45439
4
266
?25
8 ?
K β
140
, 141
, 145
K α
2 1
19K
α1
125
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Gate: 119, 125 keV
Gate: 115, 121 keV
253Md
253Fm
Gated prompt on p−side DSSSD <600 keV + X−rays
Triple Coincidences
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0 100 200 300 400 500 600 700 800Energy (keV)
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ld (
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itrar
y U
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399
266
K= 257 keVL= 373 keVL= 240 keV
K= 124 keV
338
K= 196 keVL= 312 keV
K
L
K
L
K
L
188
K= 46 keVL= 162 keV
K
L
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253Fm comparison: All Ge detectors vs Si box detectors
Conversion Electrons and Gamma Rays
Predicted by
BrIcc v2.2b
NEW
M1 at 200 keV: K−conversion coefficient ~10!
E2 at 100 keV: L−conversion coefficient ~50!
K X−rays: ~ 150 keV
L X−rays: ~ 30 keV
Preference: odd−A nuclei/chains!
~0 keV
~0keV
~100−500 keV
α−dec
ay
gamma−ray emission or
INTERNAL CONVERSION
IDEA:
Want highly−converted transitions:
=> K and/or L X−rays
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Where are we going to go next?
One Step Ahead...
Next Step in SHE experiments: Z Fingerprinting via X−rays
NEEDED: Long Decay Chains && High Production && High Detection Efficiency!
2n
0.1
0.5
1
5
10
243Am−target
30 40 50
3n
115289
1152884n
287115
Cro
ss s
ectio
n (
pb
)
Excitation energy (MeV)
A=287, 288, 289
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3n4n
2n
Three different E115 Isotopes Produced
2α
0α
1α
5α
4α
3α
2α
1α
3α
4α
2α
1α
113
285
117
293
115
289
Rg
281
Bh
272
268
268
Mt
276
Rg
280
113
284
115
288
Rg
279
Mt
275
113
283
115
287
267
Bh
271
Rf
Db
Db
Yu. T. Oganessian et al., PRC72, 034611 (2005)
Yu. T. Oganessian et al., PRL 104, 142502 (2010)
Ca,xn)243 Am( 48 291−x 115 − 8 weeks approved!
Spokesperson: D. RudolphYu. T. Oganessian et al., JPG 34, R165 (2007)
V. Zagrebaev, NPA734, 164 (2004).
1) 287−115 decaying with a chain of 5 alphas
1.5 pb => 1 chain/week => 8 chains in total
=> 8*5 = 40 X−ray oppertunities
2) 289−115 confirm daughters in the 293−117
chanis from Dubna. Here ~0.5 pb
A=287, 288, 289
3) E115 alpha−gamma coincidence spectroscopy
Expected 20 decay chains =>100 oppertunities
+ Nuclear structure information
4) 287,288−115 confirmation of previous results
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To kill four birds with one stone!
Aims of the Experiment
2α
0α
1α
5α
4α
3α
2α
1α
3α
4α
2α
1α
113
285
117
293
115
289
Rg
281
Bh
272
268
268
Mt
276
Rg
280
113
284
115
288
Rg
279
Mt
275
113
283
115
287
267
Bh
271
Rf
Db
Db
Expected to produce 8 decay chains
N > 1 K−X−ray
X
N ~ 1 K−X−ray
X
N ~ 1 K−X−ray
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X
X
X
X=> N ~ 2−3 K−Xrays/chain!
A Scenario of X−rays in the Decay Chain
Nuclear structure arguments + numbers include realistic conversion factors
The populated excited state will alpha decaydirectly (not via groundstate)
The alpha populates the ground state
3α
4α
2α
1α
Rg
279
Mt
275
113
283
115
287
267
Bh
271
Db
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SpecTAS I
α −efficiency ~80%
4+1 segmented Ge detectors*
* Small−image mode => compact focal plane
* High segmentation => 192 Si strips
* Multi−coincidence capabilities
=> suitable for SHE experiments
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γ
A versatile SHE spectroscopy setup!
−efficiency > 50% @ 150 keV
(mm)Z identification of E115!
No alpha decays253