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Present and future limitations of SHE in-beam experiments
R-D Herzberg
Outline
Decay studies Equipment Present bottlenecks
– Separator– Spectrometer– DAQ
Sample calculatons
In-beam studies Equipment Present bottlenecks
– Target– Spectrometer– Recoil ID– DAQ
Sample calculations– 253No, 256Rf, 260Sg
Decay Studies (high beam: 10 pµA)
Target: (Sigurd)– Temperature!
Separator: (Sigurd)– Cleanliness– Transmission– Recoil Identification
Instrumentation
Equipment
GREAT – type spectrometer
Sensitivity to all emitted radiation
Clean Recoil ID DAQ: Triggerless to
avoid correlation losses due to deadtime
Bottlenecks
Geometric efficiencies– Active tape (moving Si)– Can yield extra 25 %
over “tunnel” designs– Very clean– Might induce losses for
short primary times.
Preamplifiers with large dynamic range required (Recoil -> Alpha -> CE)
Bottlenecks II
Ge detectors: – Close geometry– Sensitivity to X-rays
Conversion electrons– Low thresholds on all Si– Thick Si required
DAQ
Must be able to handle a large number of channels
Common deadtime approaches not really suitable -> triggerless DAQ!
Short decays (µs) require digital cards to allow distinction
Sample calculation 261Bh
209Bi(54Cr,2n)261Bh XS ~ 0.1 nb (NPA273 (76) 505)
To do spectroscopy of 257Db one needs to see >1000 alpha decays
Separator efficiency 60% Br(alpha) = 100% 21 days at 1000 pnA -> straightforward If XS 10 pb and beam 5000 pnA 42 days
(marginal)
Conclusions
No insurmountable problems at the focal plane.
Spectroscopy after alpha decay is an excellent way to identify single particle structure in SHE
Possible down to 10 pb
In-beam Studies
Experience with gamma and CE studies Unique set of problems Main challenge is Fission
Equipment
Target (Wheel) Prompt Spectrometer capable of high rate Separator with large transmission Excellent Recoil ID DAQ capable of high rate
Gamma Ray spectrometer
Dominant channel is constant ~0.1 - 1b Fission. This limits Ge rate!
Target wheel spokes need beam sweeping High granularity and large distance to keep
individual rates low (Jurogam, Euroball) Background from entrance windows etc.
– Need windowless system!
Electron Spectrometer
Fission does not readily procuce CE SHE produce more CE than Gamma
Delta electrons require HV barrier Generally difficult Rate concentrated near field axis Baseline dirty -> need digital cards
SACRED
At present, electron experimentsUse 20% of the beam current of Gamma experiments.
Rate adjustable with HV barrier.
Targets need to be thinner (0.25 mg/cm2)
Recoil ID
Mainly the task of the separator
Scattered beam
Fm recoils
Rate calculation basics
10 pnA on 500 µg/cm2 at 1 µb = 325 Reactions/h At maximum XS ~20 ħ in the system Fission rates adjusted to match experimentally
observed Ge rates, then scaled Two spectrometers: 5% and 10% Efficiency
e.g. Jurogam or Euroball
Bottlenecks
Ge rate. Present: 10 kHz/detector With digital electronics and high throughput
preamplifiers: 30 kHz/detector, eventual aim is 100 kHz/detector
DAQ must handle these rates to preprocess and write to tape. Data rates up to 50MB/s– BGO suppression– Recoil coincidence
Sample calculationsN
uc
leu
s
Th
ick
ne
ss
I_B
ea
m
X S
ec
t
Re
ac
/h
No
de
t
Eff
G/h
T_
tot
Fis
s/s
Ga
mm
ab
g/s
Ge
_ra
te
Da
tara
te
Tra
ns
mis
sio
n
(ug
/cm
^2
)
(pn
A)
(nb
)
% de
tec
ted
(da
y)
(kH
z)
raw
(M
B/s
)
%
254No 500 10 2000 650 45 5 41 5 90000 134996 3000 1 25253No 500 10 1000 325 45 5 20 10 90000 134996 3000 1 25252No 500 20 220 143 45 5 9 23 180000 269991 6000 2 25256Rf 500 150 5 24 200 10 7 29 1350000 4046392 20232 31 60260Sg 500 210 0.28 2 200 10 1 365 1890000 5664948 28325 43 60
Conclusions
Decay studies will be possible without large changes to existing detector technology and electronics. Target/Separator are crucial.
In-beam studies will need highest rate capabilities – electronics, DAQ. Target must allow the beam, 1 nb level possible.
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