Transcript Application of heavy charged particle spectrometry

Application of heavy charged particle spectrometry
1) Identification of superheavy elements by means of alpha decay sequence
2) Study of hot and dense nuclear matter by means of charged particle spectrometry
Table of isotopes in the range of superheavy elements
Heavy ion collision with
ultrarelativistic energy
Production of superheavy elements
Drop model: 1) stability decreases with increasing proton number
2) excess of neutrons increases with increasing proton number
Competition of volume energy (strong nuclear interaction) and coulomb energy
Existence of „more stable“ superheavy elements made possible by existence of
magic numbers - shell structure ↔ shell model
Stability island – Z = 114 and N = 184 – depends on potential form, significant
uncertainty
Problem: very small cross-sections
production only single nuclei – necessary unambiguous identification
Energy : 1) sufficient for overcoming of Coulomb barrier
2) as small as possible, to obtain “relatively stable“ compound nucleus
Production possibilities: 1) Neutron capture – up to Z = 100 (earlier decay then
neutron capture)
2) Reaction of light nucleus on heavy target
3) „Cold“ fusion of heavy nucleus – projectile A ~ 40, EEX ~ 10 MeV
4) „Hot“ fusion of heavy nucleus – usage of 48Ca (Z = 20) EEX ~ 40 MeV
Decay of alpha decay sequence → alpha particles contain information about energy
differences between following nuclei
Detection of superheavy elements at GSI Darmstadt
Elements 107 – 112 device SHIP at GSI Darmstadt: fusion reaction on Pb, Bi nuclei:
usage of separation, separation of compound nucleus, implantation to active volume of
detector and identification by means of alpha decay sequences
Identification of single cases of superheavy element production and decay :
1) Capture of all alpha from decay sequence and determination of their energy
2) Identification of fission
TOF
Stopping
of beam
Rotated target (Pb, Bi) low thaw point
intensive beam – 1012 nuclei/s
dipole
magnets
Choice of incurred compound nucleus:
Velocity filter:
vCM 
mp
m p  mt
vp
rotated
target
Electric deflectors and dipole magnets:
Fel = q·E
Fmag = q·v·B
Right choice E a B  for vCM is FTOT = Fel – Fmag = 0
electric
deflectors
quadrupole magnets
SHIP device
Suppression of residual background:
TOF spectrometer:
Start – transition detectors, thin carbon foils (electron
production) and mikrochannel plates
Efficiency 99,8%, resolution 700 ps
Stop – 16 silicon strip detectors ΔE = 14 keV
for alpha from 241Am
transition detectory
Coverage: 80% of 2π
HPGe detectors – photons from deexcitation of excited nuclei
Cross sections až ~ pb, single nucleus per tens days
Very intensive beams during many months
stop detector
(silicon)
Fusion per low energies:
107
108
109
110
111
112
Bh
Hs
Mt
Dm
Rg
Cp
Bohrium
Hassium
Meitnerium
Darmstadtiumu
Roentgenium
Copernicium
First identified decays of named element with present second highest Z
Further – fusion by means of higher energies:
(112, 113, 114, 115, 116, 117, 118)
Problem – sequence ends by unknown isotopes,
rather long decay time
(problem with identification by means of coincidences)
Year 2006 – join – looks OK
Results from GSI confirmed also by
Japanese laboratory RIKEN
Reaction: 48Ca + 244Pu → Z = 114, A = 292
Excitation function for C+Pu reaction
Map of superheavy elements
Proton number
Cold fusion
Hot fusion
Neutron number
Stability
island
Chemical analysis of single atoms
Nucleus decays early than new is produced
108 Hassium – one from last element chemically studied
Known isotopes of hassium
Nucleon
number
Decay
halftime
only elements in this
column can be octavalent
First produced hassium nucleus
Oxid of ruthenium RuO4
Oxid of osmium
OsO4
Oxid of hassium
HsO4
Element density [g/cm3] melting point [oC] boiling point [oC] stiffness [Mohs]
Study of volatility → oxides of VIII group are very volatile
Production of more stable Hs isotopes
Narrow channel with decreasing temperature from -20oC up to -170oC → the more
volatile the further molecules will flight before adsorption
Hs with A ~ 288 will be maybe very stable
Study of hot and dense nuclear matter by means of charged particles production
Relativistic heavy ion collisions→
Big number of produced charged particles
Effort to build 4π detectors of charged particles
Example of FOPI spectrometer at GSI Darmstadt
Determination of nuclear matter temperature – spectrum
Determination of pressure – particle collective flow
Scheme of FOPI spectrometer
Determination of
nuclear matter
equation of state
Spectrometer of charged particles FOPI
Display of event detected by FOPI
spectrometer
Introduction of transfer mass mT :
E

 pz 

and rapidity y: y  1 ln c

2  E p 

z 
c

mT2 c 2  m2 c 2  p 2x  p 2y
1  mc  mv cos  1  1    cos 

y

ln
  ln
and then:
2  mc  mv cos  2  1    cos 
Relative rapidity: YREL = (Y - YPRO/2)/(YPRO/2)
Target region YREL  -1
Collision region YREL  0
Identification of charged particles
YPROJ – projectile rapidity
Projectile region YREL  +1
Spectra of charged particles (Ni+Ni a Au+Au
experiments with beam energy 1 GeV/A)
Two Arm Photon Spectrometer
Detection of gamma, neutrons and charged particles
384 BaF2 detectors
with plastic veto –
distinguishing of neutral
cooperation with TOF plastic wall
- collision characteristic:
and charged particles
Beam energy: 10 MeV - 200 GeV
(GSI Darmstadt, KVI Groningen
GANIL Caen, CERN)
Collective flow of nucleons
N = N0( 1 + A·cosφ + B·cos(2·φ))
A – magnitude of asymmetry in the collision plane
B – magnitude of asymmetry perpendicular to it
(eliptical flow)
Relative rapidity: YREL = (Y - YPRO/2)/(YPRO/2)
A < 0, B = 0
Target region YREL  -1
A = 0, B < 0
Collision region YREL  0
YPROJ – projectile rapidity
A > 0, B = 0
Projectile region YREL  +1
Dependence of collective flows on rapidity (origin of nukleons)
Experimental data – dependency of collective flow on nucleons
number – agreement of hydrodynamical models
Bounce off particles to the
Reaction plane:
Squeeze out of particles perpendicular to
reaction plane
Target region
Target region
Collision region
Projectile region
Application at material research - scattering, channeling, ion reaction ...
Usage ions for modification and studies of structure of surface layers of solid materials
Usage of ion accelerators for relatively low energies in the range from keV up to MeV
Spectrometers of charged nuclei – often semiconductor silicon detectors
Different types of silicon semiconductor
detectors of charged particles
Tandetrom 4130 MC at NPI ASCR is used
for material research – from H up to Au, energies
from hundreds keV up to tens MeV
Elastic scattering ions:
RBS (Rutheford Backscattering Spectroscopy) - spectrometry of charged pasrticles back scattered
by Rutheford scattering – layers from nm up to μm – spectrometry of scattered ions by
semiconductor detectors. Change of energy given by momentum change and ionisation losses –
profiles of impurities distribution materials are determined – mainly heavy nuclei
RBS channeling – channeling of charged particles – crystal structures – determination of distinctive
directions of crystal axes and impurities – slight turning of crystal sample
ERDA (Elastic Recoil Detection Analysis) – detection of atoms knocked on by ions – mostly lighter
nuclei, from hydrogen up to nitrogen – possibility of control changes of surface properties –
study of hydrogen amount at polymers – connection with measurement of ion time of flight
detector
scattered
ion
incident
ion
reflected
ion
incident
ion
detector
ERDA
RBS
Ion reaction with nuclei
PIGE (Particle Induced Gamma ray Emission)
PIXE – (Particle Induced Gamma ray Emission)
see gamma spectroscopy
Material modification and working
Ion microprobe – very narrow and intensive ion beam – usage – scanning of object surface with
micrometer accuracy
Ion implantation – modification of surface material layers
Ion litography and ion beam machining – preparing of microelectronical a optoelectronical
components and microscopic mechanical devices.
AMS – accelerator mass spectroscopy
– impurity of elements with
concentration 10-15 – often for carbon
dating
Sprockets produced by ion litography method at
photoresistive material