GOSIA

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(No Transcript)
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GOSIA

• As a Simulation Tool
• J.Iwanicki,
• Heavy Ion Laboratory, UW

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OUTLINE

• Our goal is to estimate gamma yieds
• What the yield is
• Point Yield vs. Integrated Yield
• What they are needed for
• What is needed to calculate it
• Definition of the nucleus considered
• Definition of the experiment

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YIELD

• GOSIA recognizes two types of yields
• Point yields calculated for
• Excited levels layout
• Collision partner
• Matrix element values
• CHOSEN particle energy and scattering angle
• Integrated yields calculated for
• (... as above but ...)
• A RANGE of scattering angles and energies

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POINT YIELD

• How GOSIA does it?
• Assumes nucleus properties and collision partner
• starts with experimental conditions (angle,
  energy) and matrix element set
• solves differential equations to find level
  populations
• calculates deexcitation using gamma detection
  geometry, angular distributions, deorientation
  and internal conversion into acount.

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POINT YIELD

• Point yields
• are fast to be calculated...
• ...so they are used at minimisation stage
• OP,POIN if one needs a quick look
• but are good for one energy and one (particle
  scattering) angle

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INTEGRATED YIELD

• Integrated yields
• are something close to reality
• but quite slow to calculate
• Useful integration options
• axial symmetry option
• circular detector option
• PIN detector option (multiple particle detectors)

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YIELD CORRECTION

• However
• Correction Factors can be found by comparison of
  calculated point and integrated yields.
• Correcting the yield is like averaging point
  yields over energy and angular range,
• so the better the choice of mean energy/angle,
  Correction Factor is closer to 1.
• One needs as many C.F.s as gamma yields

CF
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YIELD CORRECTION

• Correction depends on the matrix element set so
  it is usually performed after satisfactory
  initial set is found.
• Minimisation is usually performed using corrected
  yields
• After minimisation, another correction should be
  performed with the new found matrix element set
  so the process is recursive but converges very
  well.

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YIELD

• GOSIA calculates yields as differential cross
  sections, integrated over in-target particle
  energies and particle scattering angles
• differential in ? but integrated for particles
• The GOSIA yield may be understood as a mean
  differential cross section multiplied by target
  thickness (in mg/cm2)

Ymb/sr ? mg/cm2
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88Kr simulation level layout
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88Kr simulation level layout
5 6
4 3 2 1
One usually adds some buffer states on top of
observed ones to avoid artificial population
build-up it the highest observed state
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megengeneration of matrix elements set

• Apply ? transition selection rules to create a
  set of all possible matrix elements involved in
  excitation.
• This is easy but takes time and any error will
  corrupt the results of simulation!
• Tomek quickly wrote a simple code to do the job
  which uses data in GOSIA format.

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megengeneration of matrix elements set
level number
parity
spin
level energy MeV
input termination
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megengeneration of matrix elements set

•  
• iwanicki_at_buka/Coulex/88Kr megen
• 1
• Create setup for this multipolarity (y/n)
• n
• 2
• Create setup for this multipolarity (y/n)
• y
• Do you want them coupled ?
• n
• Please give limit value
• -1.5 1.5
• 3
• Create setup for this multipolarity (y/n)
• n
• ()
• 7
• Create setup for this multipolarity (y/n)
• y

E2
M1
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megenoutput
E2
initial level final level starting value (1)
low limit high limit
M1
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How to get matrix elementsfor simulation from?

• Check the literature for published values
• Get all the available spectroscopic data
  (lifetimes, E2/M1 mixing ratios, branching
  ratios)
• Ask a theoretician
• Use OP,THEO to generate the rest from rotational
  model
• Do some fitting with spectroscopic data only

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OP,THEOgeneration of a starting point

• From the GOSIA manual
• OP, THEO generates only the matrix specified in
  the ME input and writes them to the (...) file.
• For in-band or equal-K interband transitions only
  one (moment) marked Q1 is relevant. For non-equal
  K values generally two moments with the
  projections equal to the sum and difference of
  Ks are required (Q1 and Q2), unless one of the
  Ks is zero, when again only Q1 is needed.
• For the K-forbidden transitions a three parameter
  Mikhailov formula is used.

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OP,THEO for 88Kr
OP,THEO 2 0,4 1,2,3,4 2,2 5,6 2 1,1 0.3,0,0 1,2 0.
05,0,0 0,0 7 1,2 0.05,0,0 0,0 0
number of bands (2) First band, K and number of
states band member indices Second band, K and
number of states Multipolarity E2 Bands 1 and 1
(in-band) Moment Q1 of the rotational
band Multipolarity M1
band 1 band 2
4 3 2 1
5 6
end of band-band input end of multipolarities
loop
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Minimisation with OP,MINI

• Some minimisation would be in order but
  minimisation itself is a bit complex subject...
• Lets assume we have some best possible Matrix
  Elements set.
• Next step is the integration over particle energy
  and angle.

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Integration with OP,INTG

• Few hints
• READ THE MANUAL, it is not easy!
• Integration over angles assume axial symmetry if
  possible (suboption of EXPT)
• Theta and energy meshpoints have to be given
  manually, do it right or GOSIA will go astray!

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Integration with OP,INTG

• Yield integration over energies stopping power
  used to replace thickness with energy for
  integration
• One has to find projectile energy Emin at the end
  of the target to know the energy range for
  integration.

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elo screen dump
iwanicki_at_jedrek/Coulex/88Kr elo Notes to
ELO users 1) Maximum of energy steps
100 2) Maximum of absorbers number 40 3)
Maximum of projectiles number 40 4) For
energies less than 10 keV/u uncertainty of range
(and energy loss) may be greater then 10,
especially for lighter projectiles or absorbers
Input data
Absorbers specification Enter
number of absorbers 1 Absorber 1 Solid of
1 components Enter mass and atomic numbers and
number of atoms in component 1 120 50 1
Element 1 120Sn 1 atoms Enter thickness of
solid absorber ( lt 0 - mm, gt 0 - mg/cm2) 1
Equivalent Values Z 50.00, A 120.00,
Av.Ion.En. 511.800 eV Thickness
0.0014 mm ( 1.0000 mg/cm2 )
Projectile specification Enter
number of projectiles 1 Mass and atomic numbers
of projectile 1 88 36
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elo screen dump
Projectile specification
Enter number of projectiles 1 Mass and
atomic numbers of projectile 1 88 36
Projectile 1 88Kr
Energy specification Enter indeks, if indeks
0 - total energy, if indeks 1 - energy per
nucleon 1 Enter minimum, maximum and step of
energy 1 3 0.1 Choose output specification -
enter iout iout 1 - only energy losses iout
2 - energy losses and ranges iout 3 -
energy losses, ranges and stopping powers 3
End of input data reading Output data will be
written on file ELO.OUT
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YIELD ? COUNT RATE

• GOSIA is aware of gamma detectors set-up
• Gamma yield depends on detector angle (angular
  distribution)
• However, angular distributions are flattened by
  detection geometry (both for particle and gamma )
• Gamma detector geometry is calculated at the
  initial stage (geometry correction factors are
  calculated and stored for yield calculation)

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YIELD ? COUNT RATE

• One may try to reproduce gamma detector set-up of
  the intended experiment
• or assume the symmetry of the detection array and
  calculate everything with a virtual gamma
  detector covering 2? of the full space (huge
  radius, small distance to target)

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YIELD ? COUNT RATE

• Taking into account the solid angle, Avogadro
  number, barns etc, beam current, total
  efficiency...

Count Rate
target
y2c code
yield ? ? count rate
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Having the yields calculated...

• Kasia is going to show the way to estimate
  experimental errors of matrix elements to be
  measured

generated yields
matrix element errors estimate
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Saturation of the yield
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88Kr on 208Pb target, simple sensitivity to the
diagonal E2 matrix element of the 21 state
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How does GOSIA work? (1/3)
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How does GOSIA work? (2/3)
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How does GOSIA work? (3/3)
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How does GOSIA work?
calculated yield
experimental yield
normalisation factor
spectroscopic data point
calculated magnitude