Simulations on “Energy plus

Transmutation” setup, 1.5 GeV

Mitja Majerle

majerle@ujf.cas.cz

The document about simulations of EPT setup can be downloaded in form of report at :

http://ojs.ujf.cas.cz/~mitja/articles/ept.pdf

Outline Cluster of computers (linux) MCNPX 2.4.0 First tests with PVM (in Třešt) Simulations of PHASOTRON

experiment (presented in Pavia, Avignon)

Simulations of ENERGY PLUS TRANSMUTATION setup (Dubna, Jaipur)

Cluster

1 server (the slowest machine) Hosts boot through DHCP,

filesystem through NFS – extendable to many hosts

Connections through SSH PVM (Parallel Virtual Machine) PVM works also on li1 and li2.

Parallel processing

The use of parallel processing (PVM) speeds up our calculations significantly.

A very powerful tool – where to use it ?

2000

4000

6000

8000

0

10

20

30

40

50

60

70

80

90

0 2000 4000 6000 8000 10000

Accumulated processor power [MHz]H

isto

ries

sim

ula

ted

in 1

s

nps=2000k

nps=50k

?

Simulations, how/what

we calculate

MCNPX code v. 2.4.0 (on Linux, parallel computing)

Input : setup geometry starting conditions

Output 1: neutron

distribution Cross-section libraries

(Au, Al - ENDF; Bi - experimental; Iodine - ?)

Output 2: masses of

produced elements or B-values

Influence of the setup parts

Concrete walls : Neutrons are

moderated and reflected back

197Au(n,g)198Au

1E-8

1E-7

1E-6

1E-5

1E-4

0 5 10 15 20 25 30 35 40 45

Distance along the target [cm]

B [g

-1 p

roto

n-1

]

experimentalno wallsHTAPE3XFM

ENERGY + TRANSMUTATION INFLUENCE OF THE SETUP PARTS

simplifications of the setup description different parts of the setup

SYSTEMATIC ERROR (not accurately known exp. conditions)

beam geometry reactions with protons inserted detectors

ACCURACY OF SIMULATION intra-nuclear cascade model used in calculations

PARAMETERS OF THE SETUP the number of produced neutrons (spallation,

fission, ..) k (criticality)

Control detectors for studying the setup

- with (n,g) we study LE neutrons (flat part) – odd numbers

-(n,4n) threshold is 23 MeV – even numbers

1E-07

1E-06

1E-05

1E-04

1E-03

1E-02

1E-01

1E+00

1E-10 1E-08 1E-06 1E-04 1E-02 1E+00 1E+02 1E+04

Energy [MeV]

Nne

utro

ns

on the target

under Cd

outside box

The influence of setup parts

We cannot remove some things from the setup and measure.

Simulations help us understand what would happen if we did that.

The simplifications of the blanket

No influence on high energy neutrons (even numbers)

Box has no influence on HE neutrons !

Box blurs differences.

40%, 10%

Polyethylene, Cd layer

The spectra were taken inside the 1st and 3rd gap.

No influence on HE neutrons.

1st gap, 3cm from axis

1E-06

1E-05

1E-04

1E-03

1E-02

1E-01

1E-10 1E-08 1E-06 1E-04 1E-02 1E+00 1E+02 1E+04

without Cd

without box

whole_setup

3rd gap, 3 cm from axis

1E-07

1E-06

1E-05

1E-04

1E-03

1E-02

1E-01

1E-10 1E-08 1E-06 1E-04 1E-02 1E+00 1E+02 1E+04

without Cd

without box

whole_setup

absorption done by 238U resonance capture

Comparison of HE part of spectra

0,85

0,9

0,95

1

1,05

1,1

1,15

0,1 1 10 100 1000

Neutron energy [MeV]

Ratio

w ith Cd/all

w ith box/all

Aluminum and iron holders, upper iron plate

Two simulations with and without Al, Fe components. The results do not differ outside the limits of statistical error - (HE 3%, LE 10%)

The upper iron plate reduces the number of neutrons for 2%.

The wooden plate

Wooden plate under the target(1+2cm,0.5kg/l).

Without box. Detectors from top to

bottom. Asymmetry 5% =>

negligible wood influence. 0E+0

1E-5

2E-5

3E-5

4E-5

5E-5

-10 -5 0 5 10

Radial foil position [cm]

Pro

du

ctio

n r

ate

Au-198

Au-194

Systematic error Systematic error may be done,

because we can/did not measure all the experimental conditions.

Simulations give us the estimation of the error.

In simulations we vary experimental conditions in limits of the accuracy with which we measured them.

Beam parameters influence Beam profile is approximated with Gaussian

distribution (good only near the beam center !). We must always count with beam displacement. Experimentally determined beam profiles and

displacement (V Wagner using monitor and track detector data – for profile mainly I Zhuk data):

Experiment

(Energy) Beam

integral [1013]

Beam integral on lead target [1013]

FWHM (vertical)

[cm]

FWHM (horizontal)

[cm]

Fraction of beam outside

Pb target [%]1)

Position (vertical)

[cm]

Position (horizontal)

[cm]

700 MeV 1.47(5) 1.04(8) 5.91(21) same < 27 -0.4(9) 0.2(2) 1 GeV 3.40(15) 3.25(14) 4.1(3) 2.5(3) < 6 0.2(2) 0.0(2)

1.5 GeV 1.14(6) 1.10(5) 3.7(5) 2.4(5) < 6 0.1(2) 0.3(2) 2.0 GeV 1.25(6) 1.07(10) 5.4(3) 3.8(3) <20 0.3(2) -1.4(2)

Beam profile

Simulations with 3mm, 3cm homogenous beams and with a beam with gaussian profile (FWMH=3cm).

Differences only for few percents.

Not important.-10

-8

-6

-4

-2

0

2

4

6

1 2 3 4 5 6 7 8 9 10

Foil and reaction number

beam

/3cm

-1 (i

n %

)

3mm/3cm-1

gauss/3cm-1

Beam displacement

Beam displaced for 3,5,8, and 10 mm.

Differences between results up to tens of % Displacement must be measured as accurately as possible !

0

10

20

30

40

50

60

70

1 2 3 4 5 6 7 8 9 10

Foil and reaction

Dis

pla

ced

bea

m/c

ente

r b

eam

-1 (

in %

)

3 mm

5 mm

8 mm

10 mm

The influence of protons

Activation detectors could also be activated by protons.

Cross-sections for reactions with protons are not included in MCNPX.

Estimations from Phasotron experiment and neutron/proton ratio : in gaps, near the central axis ca. 10% of activation is due to protons.

The influence of detectors on neutron field

Metal plate on top reduces the number of neutrons only for 2%. Our detectors are much smaller.

Golden strap (2mm, 4mm) in the first gap has no influence on detectors in other gaps.

Only 0.1 mm thick golden strap is an obstacle for thermal neutrons : it can reduce the production rates of reactions with thermal neutrons inside the same gap for 20%.

The influence of plastic foils for detectors on neutron field

The 4mm and 8mm polyethylene on which were placed the detectors for 1.5 GeV experiments had effect on LE neutrons.

Au in sandwich of 2 Bi foils => no influence.

1E-8

1E-7

1E-6

1E-5

1E-4

1E-3

1E-2

1E-1

1E+0

1E-10 1E-7 1E-4 1E-1 1E+2 1E+5

nothing

4mm polyeth foil

full poly

Intra-Nuclear Cascade models

In MCNPX are 3 models (above 150 MeV): Bertini CEM Isabel

The differences are up to 50% (standard, our detectors).

-25

-20

-15

-10

-5

0

5

10

15

20

25

30

1 2 3 4 5 6 7 8 9 10

Foil and reaction

mo

del

/ber

tin

i-1

(in

%)

cem

isabel

-40

-30

-20

-10

0

10

20

30

40

50

60

1 6

11

16

21

26

31

36

41

46

51

56

61

Foils and reactions of the Rez group

mo

del

/BE

RT

INI-

1 (i

n %

)

CEM/BERTINI-1

ISABEL/BERTINI-1

Neutrons per proton, criticality,..

Experimentally we cannot measure these.

For 1.5 GeV experiment, neutron production :

29 in nuc. Interactions 8 in (n,xn) 14 prompt fission.

Together 54 neutrons per 1 proton.

Without box 49 neutrons, box reflects back 10% of them.

KCODE calculations for criticality :

k=19.2% k was calculated also

by S.R. Hashemi-Nezhad - 22%.

If we add polyethylene wall at the back, k stays the same.

Neutrons per proton with beam energy

Neutrons per 1 proton and per 1 MeV in the beam

Box adds ca. 5 neutrons

Saturation Peak at 1500 MeV

0

0,005

0,01

0,015

0,02

0,025

0,03

0,035

0,04

0 500 1000 1500 2000 2500 3000

Energy [MeV]N

eutr

ons/

prot

on/M

eV

withoutwith box

Comparison with the experiment

The Greek group measures the ratios of neutrons inside and outside the box.

Calculated results do not agree with experiment.

Possible reason...

1E-07

1E-06

1E-05

1E-04

1E-03

1E-02

1E-01

1E+00

1E-10 1E-08 1E-06 1E-04 1E-02 1E+00 1E+02 1E+04

Energy [MeV]

Nne

utro

ns

on the target

under Cd

outside box

Density of polyethylene ?

density 0.35kg/l

1E-7

1E-6

1E-5

1E-4

1E-3

1E-2

1E-1

1E+0

1E-10 1E-8 1E-6 1E-4 1E-2 1E+0 1E+2 1E+4

Energy [MeV]

Nn

eutr

on

s

on the target

under Cd

outside box

density 0.7 kg/l

1E-7

1E-6

1E-5

1E-4

1E-3

1E-2

1E-1

1E+0

1E-10 1E-8 1E-6 1E-4 1E-2 1E+0 1E+2 1E+4

Energy [MeV]

Nn

eutr

on

s

on the target

under Cd

outside box

Group from Řež

4 detector types A lot of cross-section

libraries Trends in ratios

experiment/simulation are seen

3 GeV experiment would confirm these trends

d)

0.0

0.5

1.0

1.5

2.0

2.5

0 5 10 15Radial distance from the target axis R [cm]

exp

/sim

Au196 1.0 GeV Au196 1.5 GeV Au196 0.7 GeV

c)

0.0

0.5

1.0

1.5

2.0

2.5

0 5 10 15Radial distance from the target axis R [cm]

exp

/sim

Au194 1.0 GeV Au194 1.5 GeV Au194 0.7 GeV

b)

0.0

0.5

1.0

1.5

2.0

2.5

-10 0 10 20 30 40 50Position along the target X [cm]

exp

/sim

Au196 1.0 GeV Au196 1.5 GeV Au196 0.7 GeV

a)

0.0

0.5

1.0

1.5

2.0

2.5

-10 0 10 20 30 40 50Position along the target X [cm]

exp

/sim

Au194 1.0 GeV Au194 1.5 GeV Au194 0.7 GeV

Comparison between experiment and simulations

194Au 196AuR

adia

l dis

trib

uti

onL

ongi

tudi

nal d

istr

ibu

tion

Longitunidal direction

0

0.5

1

1.5

2

2.5

0 10 20 30 40 50 60

l [cm]

EX

P/C

EM

24Na

196Au

194Au

206Bi

58Co

6 MeV

8 MeV

11 MeV

23 MeV23 Mev

Radial direction

0

1

2

3

4

5

6

0 5 10 15

r [cm]

EX

P/C

EM

24Na

196Au

194Au

206Bi

58Co6 MeV

8 MeV

11 MeV

23 MeV 23 MeV

Experiment: Ep = 1.5 GeV

1.5 GeV -different shape of radial distribution for experiment and simulation

0.7 GeV, 1.0 GeV - the similar shape of radial distribution for experiment and simulation

Clear dependence on reaction energy threshold ↔ on the neutron energy

Longitudinal distribution – small differences, maybe done by not included protons

Radial distribution – big differences, description is worse for neutrons with higher energy

ratios normalized on first foil

Radial distribution 0.7 GeV

0.700.800.901.001.101.201.301.401.50

0 2 4 6 8 10 12

r [cm]

EX

P/S

IM 196Au

194Au

Radial distribution 1.0 GeV

0.70

0.80

0.90

1.00

1.10

1.20

1.30

1.40

1.50

0 2 4 6 8 10 12

r [cm]

EX

P/S

IM 196Au

194Au

Radial distribution for 0.7 GeV and 1.0 GeV

1) Very small differences of shape2) Maybe increase with energy?

Conclusions:

Very important: 1) To analyze 2 GeV experiment 2) To make 3 GeV experiment

0

0.2

0.4

0.6

0.8

1

1.2

0 500 1000 1500 2000

Beam energy [GeV]

EX

P/S

IM 196Au

194Au

Necessary systematic of experiments with different beam energy

Dependence of EXP/SIM ratios for firstradial foil on beam energy