Detection Systems for Heavy Element Spectroscopy at SPIRAL

1
Detection Systems for Heavy Element Spectroscopy
at SPIRAL

• R.D. Page

2
Heavy Element Spectroscopy
3
Heavy Element Spectroscopy
superheavies
shape coexistence
proton decay
r process
shell quenching
4
Decay Spectroscopy
5
Recoil Decay Tagging
6
Decay Studies at SHIP
ToF/veto detectors
electric fields
target
1 pmA

• stop detector (PSSD)
• backward Si BOX array
• Ge Clover

A.N. Andreyev et al. Conversion electron and b
decay spectroscopy at SHIP, NIM A533, 416 (2004)
7
GREAT
Side view
Ge Planar
Ge Clover
PINs
DSSSD

• MWPC (gas) detector
• 2 DSSSD (4800 pixels)
• 28 PIN BOX detectors
• Planar Ge detector (b,g)
• Clover Ge (up to 4)
• TDR (triggerless)

R.D. Page et al. The GREAT spectrometer, NIM
B204 (2003) 634 A.N. Andreyev et al. GEANT Monte
Carlo simulations for the GREAT spectrometer NIM
A533 (2004) 429
8
Heavy Element Spectroscopy
9
g rays from a-decay fine structure

• measure Eg precisely
• establish g-g coincidences
• determine multipolarities
• alpha decay hindrance factors

a
parent
g
daughter
10
a-decay tagged isomer decays

• measure Eg precisely
• establish g-g coincidences
• determine multipolarities

parent
a
daughter
11
Plot of ICC vs. Energy
Z 50
Both atot subshell ratios depend on the
multipolarity
12
177Hg a-tagged delayed g rays
Melarangi et al., Physical Review C68 (2003)
041301(R) 1-4
13
177Hg a-tagged delayed g rays
14
177Hg a-tagged delayed g rays
Hg K binding energy 83 keV
15
177Hg a-tagged delayed g rays
Hg K binding energy 83 keV Measure Ka/246
intensity ratio gt 246 keV g is M2
16
177Hg a-tagged delayed g rays
246 77 keV g rays coincident Intensity Ig( 77)
Ig(246) gt cascade
17
177Hg isomer lifetime B(M2)
Weisskopf estimates E1 14.44 fs M1 1.48
ps E2 10.67 ns M2 1.09 ms E3 12.02
ms M3 1.23 s E4 20.06 ks M4 2.06 Ms
1.5 0.2 ms
13/2
323
246
77
9/2
0
7/2
18
M.Carpenter et al.
90Zr 92Mo FMA
181Tl (gs)
181Pb
181Hg
7010
7070
Counts
181Tl (ms)
181Pb 1n channel 181Tl 1p channel 181Hg
181Tl b decay daughter
a ae-
Measure L X rays??
19
A more complicated case - 254No isomer
A.N. Andreyev et al., NIM A533 (2004) 422
20
254No electron cascade spectra in DSSSDs
Calorimeter method G.D. Jones, NIM A488 (2002)
471
21
254No coincident g-ray spectra
R.-D. Herzberg et al. NB L X rays 53 keV g!!
22
Spectroscopy of neutron-rich nuclei
Isomer spectroscopy still useful b particle
energy not unique
23
Beta-delayed g-ray spectroscopy

• measure Eg precisely
• establish g-g coincidences
• determine multipolarities
• log ft values

parent
b
g
daughter
24
Beta-delayed g-ray spectroscopy
neutron detection essential far from stability
parent
n
b
g
Doppler broadened g line
daughter
25
Maximum correlation times
t1/2 4.8 s Dt 15 s 4800 pixels
J. Pakarinen et al., PRC 72 (2005) 011304(R)
26
Some ideas for detection system

• Make it as general purpose as possible
• Detect a, b, g, X, protons, neutrons, electrons
• DSSSD parameters
• 8 cm x 8 cm (single wafer, compact,
• correlations, damage)
• 1 mm pitch (small, but not too small)
• 0.2 2 mm thick (protons electrons)
• Ge detectors (efficient, coincidences,
• low energy g detection)
• fast g timing (lifetimes, ordering g rays)

27
Some ideas for separator
High efficiency essential High beam suppression
(clean) Focal plane image size should match
DSSSD Short flight path (isomers, fast
decays) Mass separation crucial for b
emitters Compatibility with target spectrometers
28
Discussion
29
JUROGAM RITU GREATGAMMASPHERE FMA
DSSDEXOGAM VAMOS Si