Recent TASISpec Results - GSI Webserver WWW-WIN

Multi−Coincidence Spectroscopy of SHE
*
using the TASISpec Setup
The TAS ISpec
Setup
* The GEANT4 Code
First Experimental Results
*
*
*
Next Approved Experiment
TRAPSpec
Lise−Lotte Andersson Helmholtz−Institute Mainz

The TAS ISpec
Detector Set−up
TASCA in Small Image Mode Spectroscopy
1 DSSSD (32+32 strips)
4 DSSSD (4*[16+16] strips)
4 Ge Clover (4*4 crystals)
1 Ge Cluster (7 crystals)
ER
TASCA
L−L Andersson et al., NIM A 622, 164 (2010)

Clover
The TAS ISpec
Detector Set−up
Clover
Clover
Details of the construction
Cluster
Clover

The Full TASISpec Setup in Geant4
Programmed (in great detail) by: L. G. Sarmiento

Simulated Absolute Efficiency (%)
40
30
20
10
Comparing Experiment With Simulations
Relative gamma−ray efficiency with source on holder
133Ba
152Eu
(Compare the shape of the two curves)
Experimental
Simulated
Singles
0
0 200 400 600 800
E (keV)
γ
1000 1200 1400

Detection Efficiency (%)
40
30
20
10
Comparing Simulations With Experiment
Gamma−ray efficiency obtained via alpha−gamma coincidences
Singles
Exp. α−γ coincidences
0
0 500 1000 1500
E (keV)
γ
60
50
40
30
20
10
0
0 10 20 30 40 50 60
180
160
140
120
100
80
60
40
20

Limiting Background and "False" Coincidences
There are no Compton shields in the setup
1) Internal Add−back (between crystals in same detector)
2) Cross detector add−back (some combinations are more likely)
Compton Scattering:
E’ − E = (1 − cos θ )
2
E * E’ m c
e
Geometric limits of possible scattering angles
lead to restricted ratios for the two energies, E and E’!
Min
Max

Detection Efficiency (%)
40
30
20
10
Simulating Addback Efficiencies
Implanted nuclei decaying with a single gamma−ray
No add-back
Internal add-back
Internal + cross detector add-back
0
0 500 1000 1500
E (keV)
γ

TAS ISpec
The Next Step in Superheavy Element Spectroscopy
* First main beam experiment run in May
207
Pb(
48
Ca, 2n)
253
No
* Total beam integral 2.4E18
* Results from a subset of runs, corresponding
to some 25% of the collected data

Yield (Arbitrary Units)
12000
10000
8000
6000
4000
2000
Alpha Particles Detected in the DSSSD
DSSSD p−side beam−off alpha spectrum
7.9−8.2 MeV:
some 120 000 alpha particles
(In total ~480 000 alpha from 253No)
211 Bi
253
Fm
245
Cf
211 *
Po
0
5500 6000 6500 7000 7500 8000 8500 9000
α - particle energy (keV)
211 Po
249 Fm
253 No

Yield (Arbitrary Units)
15
10
5
0
7.00 7.20 7.40 7.60 7.80 8.00 8.20 8.40
Alpha Energy (MeV)
10 4
10 3
10 2
10
1
Gates clearly show new(ish) gamma−ray transition at 669 keV
X-rays
150
221
7.63 MeV
279
20 keV FWHM
E γ = 667-673 keV
Q α = 8.15-8.35 MeV
0.1
0 100 200 300 400 500 600 700
E (keV) γ
A. Lopez−Martens et al. Nuclear Physics A 852, 15 (2011).
Alpha Decaying 253No
669

Yield (Arbitrary Units)
15
10
5
0
7.00 7.20 7.40 7.60 7.80 8.00 8.20 8.40
Alpha Energy (MeV)
10 4
10 3
10 2
10
1
Gates clearly show new(ish) gamma−ray transition at 669 keV
X-rays
150
221
7.63 MeV
279
20 keV FWHM
E γ = 667-673 keV
Q α = 8.15-8.35 MeV
0.1
0 100 200 300 400 500 600 700
E (keV) γ
A. Lopez−Martens et al. Nuclear Physics A 852, 15 (2011).
Alpha decaying 253No
669
F.P. Hessberger et al. Eur. Phys. J. D 45, 33 (2007).

Yield (Arbitrary Units)
100
50
0
150
100
50
0
Gamma−Gamma Coincidences
76 K 119 76
α2
K 125
α1 109 ?
K 135,137,140
K 140, 141, 145
β
β 151
166 ?
188
258 ?
266 ?
338
394
399
454
454
Gated prompt on p−side DSSSD

Yield (Arbitrary Units)
150
100
50
0
0 100 200 300 400 500 600 700 800
200
150
100
50
0
Conversion Electrons and Gamma Rays
253Fm comparison: All Ge detectors vs Si box detectors
K
K
K= 46 keV K= 196 keV
L= 162 keV L= 312 keV
K= 124 keV
L= 240 keV
L
188
K
L
266
K
L
338
L
399
K= 257 keV
L= 373 keV
0 100 200 300 400 500 600 700 800
Energy (keV)
Predicted by
BrIcc v2.2b

~100−500 keV
~0 keV
IDEA:
TAS ISpec
Fingerprinting E115 decay chains via X−rays
Direct measurement of proton number of the new SHE island!
8 weeks of beamtime approved at GSI.
1 α − X−ray coincidence detection per week expected.
Set−up and settings are prepared and at any time!
α−decay
~0 keV
γ−ray
emission or
INTERNAL CONVERSION
Flagship Experiment
ready to run
highly−
converted
M1
transitions
=> K X−rays
Long decay chains of odd−A nuclei!
Spokesperson D. Rudolph (Lund University)

Predicted X−rays in the Decay Chain
Numbers include realistic conversion factors
48 243 Ca + Am
267
Db
α4
271
Bh
275
Mt
α3
X
α2
279
Rg
N ~ 1 K−X−ray
X
X
N ~ 1 K−X−ray
X
α1
283
113
287
115
X
Expected to detect 8 decay chains
N ~ 1 K−X−ray
Predictions say the populated excited state
will alpha decay directly (not via groundstate)
Predictions say the alpha populates the ground state
=> N X ~ 2−3 K−Xrays/chain!
=> TASISpec efficiencies; detect one alpha−X−ray coincidence/week!

Counts /10keV
15
10
5
195Po
1.9s 6.7 MeV
4.6s 6.6 MeV
TASISpec + SHIPTRAP = TRAPSpec
6.4 sec
0.5 sec
0
5000 5500 6000 6500 7000 7500
Si energy (keV)
Second test, October 2011

α
TAS ISpec
A versatile SHE spectroscopy setup!
* Small−image mode => compact focal plane
* High segmentation => 192 Si strips
−efficiency ~80%
* 4+1 segmented Ge detectors
γ−efficiency
~40% @ 150 keV
* Multi−coincidence capabilities
=> suitable for SHE experiments
Next up: E115!
60
50
40
30
20
10
0
(mm)
253
No alpha decays
0 10 20 30 40 50 60
180
160
140
120
100
80
60
40
20

..
TAS ISpec
Many thanks to the ’updated’ collaboration:
TASCA @ GSI, DE
Helmholtz−Institut Mainz, DE
Lund University, SWE
University of Liverpool, UK
Universidad Nacional de Colombia, CO
Universitat Mainz, DE
Lise−Lotte Andersson Helmholtz−Institute Mainz