Lunchtime S.I.E.S.T.A. James Butterworth Finding Atomic Nuclei Offenders with James the Nuclear...
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Transcript of Lunchtime S.I.E.S.T.A. James Butterworth Finding Atomic Nuclei Offenders with James the Nuclear...
Lunchtime S.I.E.S.T.A.
James Butterworth
Finding Atomic NucleiOffenders with James the Nuclear Detective
“It’s element.. element...
elementary my dear Watson!”
Setting the Scene
CERNLHC CMS
ATLAS
ALICE
LHCb
ISOLDE
How ISOLDE works – The Primary Target
Primary Target
1.4 GeV Protons Exotic Nuclei – Reaction Products
1.4 Gev protons impinge on primary target
Reactions occur Exotic nuclei are liberated
Reactions:• Fission• Fragmentation• Spallation
How ISOLDE works – The Ion Source
Ion Source
Ion source ionises atom by knocking out one or more electrons
Ion is now in charge state +q
Types of ion source:• Surface• Laser• Plasma
How ISOLDE works – The Separator Z = Number of
protons A = Number of
protons + number of neutrons
Separates ions according to their A/q ratio So only ions of the mass we’re interested in get through
How ISOLDE works – REX
Cooler and Buncher
Electron Beam Ion Source Linear Accelerator
Electrostatic AcceleratingElements
Ions are trapped, cooled and bunched
Ions are ionised further by EBIS
Ions are accelerated along linear accelerator to experimental station
How ISOLDE works – Miniball
SecondaryTargetγ
γ
Miniball Detector
Miniball Detector
What can we learn from these gamma rays?
Nothing – we’re just doing it for fun...
Nuclear structure – a fundamental part of the fabric of the universe
Nuclear astrophysics – how the elements were created Applications – MRI, nuclear power etc.
So why do we need a detective?
Blue Z = 38 (Sr), A = 78, q = +1 Green Z = 37 (Rb), A = 78, q = +1
Problem: We get contamination from nuclei with different Z but the same A: isobars
These are our atomic nuclei offenders
Separator
The scale of the problem
The Solution – The Detector
SecondaryTargetγ
γ
Miniball Detector
Miniball Detector
The YorkBragg
Detector
The York Bragg Detector
Gas detector Consist of six flared modules The modules sit after the secondary target position and
surround the ongoing beamline
How does a Bragg Detector work?
0 5 10 15 20 250
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0.09
0.1
Bragg Curves for the 35 Isobar
35-Ca
35-K
35-Ar
35-Cl
35-S
Target Depth (cm)
Ioni
satio
n (e
V/an
g/io
n)
How does a Bragg Detector work?
Where are we now?Simulations
Construction
The future... The York Bragg Detector will be set up and used routinely at Miniball, for
nuclear physics experiments A package of simulations will be available for the users of the detector
Thank you - Any questions?
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