[PPT] - Measurements of (n,) cross section s Khryachkov Vitaly Institute PowerPoint Presentation

SLIDE 1

Measurements of (n,α) cross sections

Khryachkov Vitaly

Institute for physics and power engineering (IPPE) Obninsk, Russia

SLIDE 2

Justification for the (n,α) reaction cross section measurement

Reactor criticality (structural material , O, N)
Standards (10B, 6Li)
Gas production
Astrophysics
Dosimetry

SLIDE 3

Activation method;
Direct measurement of α – particle yield;

Experimental methods for (n,α) reaction investigation

SLIDE 4

Activation method

D A n

Z M Z M 2 3  

   





  

    * 1 3 2 3

N D

Z M Z M

  

   

N N

Z M Z M 1 3 * 1 3

, T1/2

n

1-st stage 2-st stage Gamma- detector Sample Gamma-ray

SLIDE 5

Limitations of the activation method

Residual nuclear must by radioactive!
Half-life time for residual nuclear must be

convenient!

Energy of gamma-ray must be convenient!
Yield of gamma-ray must be significant!

For stable residual nuclear activation measurement can not by done at all!

SLIDE 6

∆E-E method

Target Alpha- particle dE-detector E-detector Neutrons

Low energy particles can not pass through ∆E detector!
High energy particles will not be stopped in E-detector!
Low geometrical registration efficiency!
It is needed to repeat measurements for different angles!

SLIDE 7

Classical ionisation chamber

7

HV

1 6 3 4 2 5

1) Target; 2)

238U target;

3) Anode; 4) Anode signal connector; 5. Frisch grid; 6. Guard electrodes; 7. Resistor.

SLIDE 8

Relative method to cross section measurement

Neutrons

Investigated target (Cr) Standard target (U) ФI=ФS

Cr n Cr

N n    

) , (  



U f U ff

N n    

) (



U Cr U ff n

N N n n   

) ( ) , (

 

 

SLIDE 9

Classical spectrometer events classification

1. Target
2. Full absorption
3. Electrodes
4. Gas a-particles
5. Protons
6. Wall effect

n

SLIDE 10

Scheme of ionisation chamber with 226Ra α- particle source b)

226Ra

SLIDE 11

226Ra decay scheme

SLIDE 12

Scheme of the IPPE experimental setup

238U Anode Cathode Grid Anode

PA PA TFA SA TFA D DLA WFD PC

Stop Input 1 Input 2

PA – preamplifier, TFA – timing filter amplifier, D – discriminator, SA – spectroscopy amplifier, DLA – delay line amplifier, WFD – waveform digitizer, PC – personal computer.

SLIDE 13

Anode pulse shape

1000 2000 3000 4000 5000 200 400 600 800 TE T0 QAMax TG TL TS

QA Time, ns

SLIDE 14

Amplitude of anode pulse vs electron drift time

20 30 40 50 60 70 80 90 100 0,125 0,250 0,375 0,500 0,625 0,750 0,875 1,000

Rn area Po area

 window QAMax, channel

, s

SLIDE 15

α-particle directionality determination

2,00 2,25 2,50 2,75 3,00 200 400 600 800

QA, channel Time, s

1 2

QF QB QF QB Cathode Anode

SLIDE 16

α-particle directionality determination 2

20 40 60 80 100 120 140

Count

218Po

G, a.u.

100 200 300 400

High dE/dx near the cathode High dE/dx near the anode

222Rn

end begin A A

dx dE dx dE end dt t dQ begin dt t dQ G               ) ( ) ( ) ( ) (

SLIDE 17

Result of α-particle selection

20 40 60 80 100 120 1000 2000 3000 4000 5000 6000

Count

original spectrum
spectrum after regection

Energy, channel

SLIDE 18

standards
reactivity predictions of thermal and fast reactors;
calculation of helium production in fuel pins and

claddings of reactors;

calibration of the strength of neutron sources;
astrophysics;
dosimetry.

Justification for the light isotopes measurement

6Li, 10B, 12C, 14N, 16O, 19F, 20Ne

SLIDE 19

10B. Two-dimensional response function

SLIDE 20

10B. Anode pulse amplitude vs electron drift time

40 50 60 70 80 90 100 10 20 30 40 50 60 70

p+

14N(n,)

Ar

Anode pulse amplitude, channel

, channel

SLIDE 21

10B(n,α)7Li. Solid target response function

20 40 60 80 20 40 60 80

1 0

Detector gas: Ar(90%)CH4(10%) cos(90

)=0

cos(0

)=1

p,  and

7Li from 10B(nth,) 7Li 7Li from 10B(n,) 7Li

-particles from

10B(nth,) 7Li

-particles from

10B(n,) 7Li

quasi

7Li+ particles from 10B(n,) 7Li

Cathode pulse amplitude (channel) Anode pulse amplitude (channel)



SLIDE 22

Solid target kinematics peculiarity.

(1) (2) Li  Li(2) Li(1) N-beam

1 2 3 4 5 6 7 0.0 0.1 0.2 0.3 0.4 0.5

0
1

cos() limit Neutron energy, MeV

SLIDE 23

10B. Background suppression.

20 40 60 80 100 120 10 100 1000 10000

All Target Gas

N

Anode pulse amplitude, channel

SLIDE 24

10B. Spectra after corrections.

SLIDE 25

10B(n,α)7Li cross-section result

0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0 4,5 5,0 5,5 6,0 0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7

Data IRMM and IPPE

ENDF B VI=JEFF 3.0
JENDL 3.3
JEF 2.2
Zhang
Bichsel
Davis
Friesenhahn

Cross section, barn En, MeV

SLIDE 26

Why is it difficult to measure light elements?

It is difficult to prepare a clean target
Low reaction cross section
The kinematical effect – dependence of anode

pulse amplitude from the emission angle.

Negative Q – value. Background from (n,α), (n,p)

reaction, elastic recoil at working gas.

Background of a detector.
Light elements from the air (O, N) are present on

the electrodes surface.

Fine structure in cross section.

SLIDE 27

Problems of a solid target

Number of atoms is limited by self-absorption;
No radioactive isotope number of atoms

determination problem.

Energy losses in the target;
The particle leaking effect.
Background from reactions on working gas

components and chamber electrodes.

Problem with solid target preparation for some

elements (e.g. noble gases)

SLIDE 28

Gaseous target

Kr+CO2, Kr+BF3, Kr+CH4, Kr+N2…..

SLIDE 29

Gaseous target properties

Number of atoms in gaseous target is limited only by

chamber size and working gas pressure;

For events taking place on the working gas components we

can register both alpha particle and residual nuclear. Signal to noise ratio will be better.

Anode pulse amplitude is proportional to sum of alpha

particle and residual nuclei energies. PA~Eα+ER=En+Q.

There are no energy losses in target.
There are no the particle leaking effect

SLIDE 30

20 40 60 80 100 120 20 40 60 80 100 120

16O(n,) 13C, En=7.1 MeV

detector gas Kr(97%)CO2(3%)

5

4 3 2 1

Anode pulse amplitude (channel) Cathode pulse amplitude (channel)

Two-dimensional response function of gaseous target

Identified signatures of:

16O(n,0)13C signal from the

detector gas (1), alpha particle background

f the cathode (2),

background

f

protons emitted by the cathode that stopped in the detector gas (3), background

f

protons emitted by the cathode which crossed the grid (4), Protons background of the detector gas (5).

SLIDE 31

238U

h R0 R1 R2

Anode Cathode Grid Anode

PA PA TFA SA TFA D DLA WFD PC

Stop Input 1 Input 2

Scheme of the experimental setup

PA – preamplifier, TFA – timing filter amplifier, D – discriminator, SA – spectroscopy amplifier, DLA – delay line amplifier, WFD – waveform digitizer, PC – personal computer. 1-monitor chamber; 2-main chamber.

1 2

SLIDE 32

100 200 300 400 500 400 500 600 700 800 900 1000 1100 1200 1300 Cathode Anode

Time (channel) Pulse amplitude (channel)

Fission fragment 100 200 300 400 500

50

50 100 150 200 250 300 350 400 Pc Pa 10% of amplitude 90% of amplitude Tr Td Cathode Anode

-particle

Examples of signals of the main chamber and monitor chamber DSP allows you to analyse: 1) Amplitude of anode pulse; 2) Amplitude of cathode pulse; 3) Time when anode signal appeared; 4) Time when anode signal reached the satiation; 5) Time when cathode signal appeared; 6) Time when cathode signal reached the satiation; 7) Ionisation distribution along the particle track. (Anode signal shape).

SLIDE 33

R1 R2 h

One of the most crucial points of this technique was precise determination of the radii of the truncated cone’s bases. Indium or aluminium stripes and disks were used to measure the profile of the collimated neutron beam at energies 2.5 and 7.4 MeV, respectively. Investigation of the neutron beam profile was needed. N Oxygen= 2.464*1020 nuclei at V=5.6346*10-5 m3

) ( 3

2 2 2 1 2 1

R R R R h V    

Geometry of the gaseous target

N(238U) atoms in the monitor= 6.831*1018 (solid target ~500 mkg/cm2)

SLIDE 34

2 4 6 8 10 12 14 16 18 20 22 0,00 0,02 0,04 0,06 0,08 0,10 0,12 0,14 0,16

Cross Section (b) Neutron Energy (MeV)

ENDF/B-VI

27Al(n,) 24Na

En=7.4 MeV, =25 mb

Cross section of 27Al(n,)24Na reaction

SLIDE 35

10 20 30 40 50 0,0 0,2 0,4 0,6 0,8 1,0 1,2 R0=37.73+-0.11 mm measured -ray yield error function fit

Normalised -ray yield Radial distance from beam axis at collimator exit (mm)

Scheme of the experiment of neutron beam profile measurement

SLIDE 36

Rotational symmetry of the neutron beam at En=7.4 MeV

0,0 2,5 5,0 7,5 10,0 12,5 15,0 17,5 20,0 22,5 25,0 27,5 30,0 32,5 35,0 37,5 40,0

30 60 90 120 150 180 210 240 270 300 330

0,0 2,5 5,0 7,5 10,0 12,5 15,0 17,5 20,0 22,5 25,0 27,5 30,0 32,5 35,0 37,5 40,0

experiment
fit:

R0=38.64 mm x0=-0.55 mm, y0=0.65 mm View from n- source

SLIDE 37

10 20 30 40 50 60 70 80 90 100 110 200 400 600 800 1000 1200 1400 1600 1800 2000

238U( decay) 238U(n,fission)

Counts/channel

Neutron beam ON
Neutron beam OFF

Pulse amplitude (channel) Pulse height spectrum of 238U neutron monitor measured with: neutron beam on, and neutron beam off

SLIDE 38

Pulse height spectrum of 238U neutron monitor measured with: neutron beam on (1), and neutron beam off (2)

10 20 30 40 50 60 70 80 90 100 110 0,1 1 10 100 1000 10000 100000

(2) (1)

238U( decay) 238U(n,fission)

Counts/channel

Neutron beam ON
Neutron beam OFF

Pulse amplitude (channel)

SLIDE 39

Energy spectrum of α-particles

20 40 60 80 100 120 1000 2000 3000 4000 5000 6000 7000 8000

16O(n,) 13C

P

Counts/channel Anode pulse amplitude (channel)

Nuclear Physics 48 (1963) Disintegration of 16O and

12C by fast neutrons. E. A. Davis, T. W. Bonner, D. W.

Worley, and R. Bass

Present work

SLIDE 40

Two-dimensional spectrum of drift time of the end of the particle track versus the anode pulse amplitude. The dashed rectangle defines the region of interest for final analysis. The drift time window ΔTd determines the height of the effective volume of the gaseous target Δx

20 40 60 80 100 120

16O(n,) 13C 16O(n,) 13C, En=7.1 MeV

detector gas Kr(97%)CO2(3%)

Td

cathode

Anode pulse amplitude (channel)

Drift time of origin or end of particle track Td(channel)

SLIDE 41

Δt distribution for 16O(n,α) α-particles

20 40 60 80 100 120 100 200 300 400 500 600

N

dt, channel

t

SLIDE 42

Method of type of particle determination

p

Alphas

SLIDE 43

20 40 60 80 100 120 20 40 60 80 100 120

particles

background

16O(n,) 13C, En=7.1 MeV

detector gas Kr(97%)CO2(3%)

Anode pulse amplitude (channel) Rise time Tr (channel)

Two-dimensional spectrum of rise time versus amplitude of anode pulse with the dashed line separating  particles from background

SLIDE 44

Pulse height spectrum in: GIC mode (1), TPC mode after rise time suppression of background (2), TPC mode after rise time and drift time suppression of background (3). The percentages in brackets show the background contribution (BC) to the  particle line within the pulse height window ΔP for the three different operation modes of the spectrometer 20 40 60 80 100 120 1000 2000 3000 4000 5000 6000 7000 8000

16O(n,) 13C

(3) (2) (1)

P

Counts/channel

GIC mode, background contribution (BC 19%)
TPC mode, rise time suppression (BC 2.5 %)
TPC mode, rise time suppression and

additionally drift time suppression (BC 1.2 %)

Anode pulse amplitude (channel)

Energy spectrum of α-particles

SLIDE 45

Justification for the 16O(n,)13C measurement   

SLIDE 46

4 5 6 7 8 9 10 50 100 150 200 250 300 350 400

Status by 2005

Neutron energy, MeV Cross section, mb

Seitz-55
Walton-57
Davis-68
Dandy-68
ENDF/B-VI.8

Cross-section of 16O(n,0)13C reaction (direct reaction measurements)

SLIDE 47

4,0 4,5 5,0 5,5 50 100 150 200 250 300 350 400 Cross section, mb Neutron energy, MeV

Sekharan-67
Johnson-72
Bair-73
Harissopulos-05
ENDF/B-VI.8

Status by 2005

Cross-section of 16O(n,)13C reaction (obtained from an inverse reaction)

SLIDE 48

3,5 4,0 4,5 5,0 5,5 6,0 6,5 7,0 7,5 8,0 8,5 9,0 50 100 150 200 250 300 350 400

Neutron Energy (MeV)

ENDF/B-VI.8
ENDF/B-VII.0
BROND-2.2
JENDL-3.3
CENDL-2.0

Cross section (mb) Cross-section of 16O(n,0)13C reaction (Evaluations)

SLIDE 49

5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40

Experiment
Convolution Corr. ENDF B VII
Corrected ENDF B VII
ENDF B VII

Cross-section, barn En, MeV Results of the cross section measurement of 16O(n,0)13C at IRMM in compared with ENDF evaluations and experimental data

SLIDE 50

Counting statistics: typical  5%
Radii of cone: 1.1%
Height of cone: 1%
Gas pressure: 0.1%
Temperature of gas: 0.3%
Content of CO2: 2%.
Number of oxygen nuclei: 2.5%.
Background contributed into -peak: 1.2%
Number of 238U nuclei: 0.7%
Number of the fission fragments: 1.5%
Correction for neutron background
from neutron source 1.5%
Total error not related to statistics: 3.6%
Total uncertainty: 6.1%

Experimental uncertainties

SLIDE 51

Advantages of the method

Dead time for main and monitor channel is equally
The simple response function of the spectrometer
Achieved a big mass of the target
A simple method for determining the mass of non-

radioactive target

Developed numerical methods to effectively suppress

backgrounds

Wall effect is absent

SLIDE 52

10B+n → α+7Li+2.7895 MeV 7Li exited states: E*=0.47761 MeV 10B+n → 2α+t+0.3225 MeV

Isotopes

10B (20%) 11B (80%)

σ ~ 3000 barn
is used as a shielding of thermal neutrons
tritium is a source of β-rays
chemical properties of tritium are the same as those of hydrogen
tritium can replace hydrogen in all of its compounds

10B(n,2α)t reaction. The tritium production cross

section for neutron interaction with 10B nuclei

SLIDE 53

10 20 30 40 50 60 70 80 90 100 110 120 200 400 600 800 1000 1200 1400 1600 1800

Solid target I II III VI V

10 20 30 40 50 60 70 80 90 100 110 120 50 100 150

Anode signal amplitude, channel N Gaseous target

1 2 3

Gaseous target: 1 – 10B(n,α0); 2 - 10B(n,α1); 3 - 10B(n,t) Solid target: I – 10B(n,α0); II – 10B(n,α1); III – 10B(n,t); VI – 7Li; V – 7Li+α

SLIDE 54

20 40 60 80 10 20 30 40 50 60 70

5 4 3 2 Anode pulse amplitude, channel

Drift time, channel

1

Two dimensional plot obtained for neutron energy En=5.3 MeV. Numbers mark different reaction channels: 1 – 10B(nth,α1)7Li; 2 – 10B(nth,α0)7Li; 3 – 10B(nf,2α+t) (break-up reaction); 4 – 10B(nf,α1)7Li; 5 – 10B(nf,α0)7Li

Products of 10B(n,α)7Li reaction on fast neutrons

SLIDE 55

Relative method of cross section determination

F N N

B

* *

 

 

F N N

T B T

* * 

 

  N NT

T 

Measurement of 10B(n,2α)t reaction’s cross section was carried out relative to 10B(n,α) reaction cross section.

SLIDE 56

Results of the cross section measurement of

10B(n,2α)t reaction

SLIDE 57

20 40 60 80 100 120 10 20 30 40 50

Anode pulse rise time, channel Anode pulse amplitude, channel

20 40 60 80 100 120 10 20 30 40 50

20Ne(n,3) 20Ne(n,2) 16O(n,0) 20Ne(n,1)

Anode pulse rise time, channel Anode pulse amplitude, channel

20Ne(n,0)

20Ne(n,α)17O cross section measurement

SLIDE 58

Particles separation

1 2

QF QB QF QB Cathode Anode

20 30 40 50 60 70 80 90 100 50 100 150 200 250 300 350

 , channel

N



SLIDE 59

20Ne(n,α)17O cross section measurement

4,0 4,5 5,0 5,5 6,0 6,5 7,0 0,02 0,04 0,06 0,08 0,10 0,12 0,14 0,16 0,18 0,20 0,22 0,24 0,26 0,28 0,30 0,32 0,34

Cross section, barn En, MeV

20Ne(n,0)+ 20Ne(n,1)

Boner IPPE 2010

SLIDE 60

20Ne(n,α)17O cross section measurement

5,5 5,6 5,7 5,8 5,9 6,0 6,1 6,2 6,3 6,4 6,5 6,6 6,7 6,8 6,9 7,0 0,00 0,02 0,04 0,06 0,08 0,10 0,12 0,14 0,16 0,18 0,20 0,22 0,24 0,26 0,28 0,30

Cross section, barn En, MeV

20Ne(n,0)

5,5 5,6 5,7 5,8 5,9 6,0 6,1 6,2 6,3 6,4 6,5 6,6 6,7 6,8 6,9 7,0 0,00 0,01 0,02 0,03 0,04 0,05 0,06 0,07 0,08 0,09 0,10 0,11

20Ne(n,1)

Cross section, barn En, MeV

5,5 5,6 5,7 5,8 5,9 6,0 6,1 6,2 6,3 6,4 6,5 6,6 6,7 6,8 6,9 7,0 0,000 0,005 0,010 0,015 0,020 0,025 0,030 0,035 0,040 0,045 0,050

20Ne(n,2)

Cross section, barn En, MeV

5,5 5,6 5,7 5,8 5,9 6,0 6,1 6,2 6,3 6,4 6,5 6,6 6,7 6,8 6,9 7,0 0,000 0,005 0,010 0,015 0,020 0,025 0,030

20Ne(n,3)

Cross section, barn En, MeV

SLIDE 61

Calculation of helium production and radiation damages in -

fuel-element cladding;
Material of reactor vessel;
reactor core;
Other construction contacted with neutron flux.

Justification for the structural material (n,α) reaction cross section measurement

Monte Carlo calculation based on the evaluated nuclear data provided by libraries. Whether their accuracy is sufficient?

SLIDE 62

Some of structural material isotopes properties

Isotope Natural abundance, % (n,α) reaction Q-value, MeV

50Cr, T1/2>1,8*1017 y, EC

4,345 +0,3213

52Cr, stable

83,489

1,2097

53Cr, stable

9,501 +1,7903

54Cr, stable

2,365

1,5466

Isotope Residual nuclear Stability

50Cr 47Ti

Stable

52Cr 49Ti

Stable

53Cr 50Ti

Stable

54Cr 51Ti

T1/2=5,76 min Isotope Residual nuclear Stability

54Fe 51Cr

T1/2=27,7 d, ec

56Fe 53Cr

Stable

57Fe 54Cr

Stable

58Fe 55Cr

T1/2=3,55 min Isotop e Residual nuclear Stability

58Ni 55Fe

T1/2=2,7 y, ec

60Ni 57Fe

Stable

61Ni 58Fe

Stable

62Ni 59Fe

T1/2=44,5 d

Cr Fe Ni

SLIDE 63

Present status of experimental data and evaluation for chromium isotopes

SLIDE 64

ENDF/B VII.1 to JENDL 4.0 cross section ratio

SLIDE 65

Status of experimental data for 50Cr(n,α)47Ti

SLIDE 66

Classical ionisation chamber

7

HV

1 6 3 4 2 5

1)

50Cr target;

2)

238U target;

3) Anode; 4) Anode signal connector; 5. Frisch grid; 6. Guard electrodes; 7. Resistor.

SLIDE 67

Motivations for removing solid target from cathode surface

1) Target surface 10 times less then cathode surface; Probability of gaseous particle absorption is proportional to the surface area. 2) Target material – gold. Low probability for charge particle emission;

SLIDE 68

New chamber design.

7

HV

1 6 3 4 2 5 8

1) Cr target; 2)

238U target;

3) Anode; 4) Anode signal connector; 5. Frisch grid; 6. Guard electrodes; 7. Resistor. 8. Golden threads

6 1 8

SLIDE 69

238U target

50 100 150 200 250 500 1000 1500 2000 2500 3000 3500 4000

Time= 20 minutes S=34323 events Anode signal amplitude, channel N

Stainless steel backing
238U enriched to 99,99 %
Total 238U mass – 4,598 mg
Total number of 238U atoms – 1,167*1019

SLIDE 70

Digital signal processing

238U Anode Cathode Grid Anode

PA PA TFA SA TFA D DLA WFD PC

Stop Input 1 Input 2 50Cr

PA – preamplifier, TFA – timing filter amplifier, D – discriminator, SA – spectroscopy amplifier, DLA – delay line amplifier, WFD – waveform digitizer, PC – personal computer.

SLIDE 71

50Cr target parameters

SAMPLE

Gold backing of 84 mg/cm2
50Cr - 365 μg/cm2
50Cr enriched to 96,8 %
52Cr - 2.98%,
53Cr - 0.18%
54Cr - 0.04%.
Target area – 14,11 cm2
Total 50Cr mass – 5,15 mg
Total 50Cr number of atoms – 6,22*1019

SLIDE 72

Background (neutron beam off)

20 40 60 80 100 120 20 40 60 80 100 120

Anode pulse amplitude, channel

Drift time, channel

Cr target Cathode Gas

SLIDE 73

Own α - activity of the detector

20 40 60 80 100 120 2 4 6 8 10 12 14 16

Working gas 0,00025 Bk Anode pulse amplitude, channel N

20 40 60 80 100 120 5 10 15 20 25 30

Cathode 0,0011 Bk

20 40 60 80 100 120 50 100 150 200 250 300 350 400

Target 0,0043 Bk E=4,8 Mev 237Np ??? – 4,79 (51%), 4,77

(25%), 4,65 (9%) (2,14*106 years).

SLIDE 74

Drift time selection for -particles only

50 55 60 65 70 10 20 30 40 50 60 70 80

Anode pulse amplitude, channel

Drift time, channel

SLIDE 75

Drift time selection for -particles only

50 55 60 65 70 10 20 30 40 50 60 70 80

Anode pulse amplitude, channel

Drift time, channel

HV

SLIDE 76

Rise time of anode signals

40 60 80 100 120 10 20 30 40 50 60

Anode pulse amplitude, channel

Pulse rise time, channel

SLIDE 77

Result for 50Cr

5 6 7 8 0,000 0,005 0,010 0,015 0,020

Cross section, barn Neutron energy, MeV ENDF/B VII.1 JENDL - 4.0 JEFF - 3.1A BROND - 3A EAF - 2010 IPPE 2011 Matsuyama JENDL - 3.3

SLIDE 78

A.Paulsen data for natural chromium.

4,5 5,0 5,5 6,0 6,5 7,0 7,5 0,000 0,001 0,002 0,003 0,004

Cross section, barn Neutron energy, MeV

SLIDE 79

Experimental uncertainties

Counting statistics: (статистическая ошибка)

Number of the -particles.
Number of the fission fragments.

Errors not related to statistics:

-particles “tail” extrapolation – 0,4%.
Fission fragments “tail” extrapolation – 0,6%.
Number of 238U atoms – 1,5%.
238U cross section – 1%.
Number of chromium atoms – 3,2%.

Total error not related to statistics – 3,7%. Typical statistical uncertainty is from 2 to 15 %.

SLIDE 80

52Cr target

52Cr target on the gold backing - 190 mg/cm2.

Target diameter – 30.9 mm;

52Cr target was 280 μg/cm2.

Isotopic composition:

50Cr - 0.1%, 52Cr-99.5%, 53Cr – 0.3% 54Cr – 0.1%.

Total mass of 52Cr is 2.1 mg.

SLIDE 81

Result for 52Cr(n,α)49Ti reaction cross section

6.50 6.75 7.00 7.25 7.50 0.000 0.001 0.002 0.003 0.004

ENDF/B VII.1 JEFF - 3.1A JENDL - 4.0 BROND - 3A EAF - 2010 IPPE 2014 Cross section, barn Neutron energy, MeV

52Cr(n,)

SLIDE 82

Determination of the nuclei number in the self-supporting target

SLIDE 83

Result for 54Fe(n,α)51Cr reaction cross section

4,0 4,5 5,0 5,5 6,0 6,5 7,0 7,5 8,0 8,5 9,0 5 10 15 20 25 30 35 40 45 50 JENDL - 4.0 JEFF - 3.1A BROND - 3A EAF - 2010 ADL - 3 ENDF/B VII.1 A.Paulsen(79) IPPE 2015 J.W.Meadows(91) W.Mannhart(07) Y.M.Gledenov(97) S.K.Saraf(91) LuHan-Lin(89) Y.Ikeda(88) FanPeiguo(85)

Cross section, mb Neutron energy, MeV

SLIDE 84

Using digital spectrometer was measured:

10B(n,) 0 and 1 channels
10B(n,2t)
14N(n,) 0, 1, 2 and 3 channels
14N(n,t)
16O(n,) 0 channel
19F(n,) 0, 1, 2 and 3 channels
20Ne(n,) 0, 1, 2 and 3 channels
36Ar(n,) 0, 1, 2 and 3 channels
40Ar(n,) 0 and 1 channels
50Cr(n,)
52Cr(n,)
53Cr(n,)
54Fe(n,)
57Fe(n,)

SLIDE 85

Conclusion

A few modification of digital spectrometry

for (n,α) reaction products registration was developed.

Background of different nature can be

efficiently suppressed.

Measurements for set of light and structural