Measurements of DN Yields and Time Spectra from p(1 GeV ... · PDF file6-9 May 2007, SCK*CEN...

Contact: [email protected] May 2007, SCK*CEN Mol, Belgium

Collaboration:• PNPI, Russia• IoP, Lithuania• PSI, Switzerland

Financial support:• CEA• FR Ministry of Foreign Affairs• GEDEPEON

D. Ridikas1, A. Barzakh3, V. Blideanu1, J.C. David1, D. Doré1, D. Fedorov3, X. Ledoux2, F. Moroz3, V. Panteleev3, A. Plukis4, R. Plukiene4, A. Prévost1, O. Shcherbakov3, A. Vorobyev3

1CEA Saclay, DSM/DAPNIA, 91191 Gif-sur-Yvette, France2CEA/DIF, DAM/DPTA, 91680 Bruyères-le-Châtel, France

3Petersburg Nuclear Physics Institute, 188350 Gatchina, Leningrad district, Russia4Institute of Physics, Savanoriu pr. 231, 02300 Vilnius, Lithuania

Measurements of DN Yields and Time Spectra from p(1 GeV) + natPb & p(1 GeV) + 209Bi


• high-energy high-power accelerators use of liquid metal targets (Hg, Pb, Pb-Bi, …)

• long flowing metal loop activated metal close to electronics, in hot cells, heat exchanger, pumps, …

• short transit time “moving” beta, photon and delayed neutron (DN) radioactivity

Introduction

Goal:Characterization of DNs from high-energy spallation-fission reactions


short Hg transit time delayed neutron (DN) activity

Prompt neutrons

Delayed neutrons

J-PARC/JAEA - thanks to H. Nakashima

Examples (A)


1MW

prot

ons

Meg

aPie

targ

et

PbB

i

Fiss

ion

cham

bers

1MW

prot

ons

Meg

aPie

targ

et

PbB

i1M

Wpr

oton

s

Meg

aPie

targ

et

1MW

prot

ons

Meg

aPie

targ

et

PbB

i

Fiss

ion

cham

bers

~5.3 m

DN/PN = ?

Examples (B)

MegaPie/PSI - thanks to F. Groeschel

~4.00 l/sMain pump~20 sTtransit

~ 82 litersVPbBi

570 MeV1.2 mA (1.8)0.7MW (1.0)

Ep

Ip

W

Beam on the target from14 August to 23 December!

D. Ridikas et al., Proc. of PHYSOR2006, Vancouver, Canada

DN and PN estimates using MCNPX+CINDER’90 Φn (DN)~ 106 n/(s cm2)Φn (PN)~ 106 n/(s cm2)

Important: DN yields are very sensitive to the choice of physics models!


Model-dependence of DN yields

583.351.903.5918.70Total/average

233.520.110.000.206

129.950.450.210.525

174.241.631.191.904

23.584.660.444.993

15.2516.350.8916.292

6.7855.600.8755.491

ai, n/p times 106T1/2, sai, n/p times 106T1/2, sGroup

CEM2k modelINCL4 +ABLA model

Difference by 2 orders of magnitude!

D. Ridikas et al., Proc. of Fission2005, CEA Cadarache, France


Model-dependence of Yin(A,Z) yields

76 78 80 82 84 86 88 90 92 94

10-2

10-1

100

sig

ma(

mb)

A

GSI data INCL ISABEL BERTINI CEM2k

Rb-37

74 76 78 80 82 84 86 88 90

10-2

10-1

100

sig

ma(

mb)

A

GSI data INCL ISABEL BERTINI CEM2k

Br-35 p(1 GeV) + Pb

• INCL4-ABLA gives “reasonable” predictions• other models overestimate significantly the neutron-rich side

1. Fission yields on the very neutron-rich side are difficult to reach2. No available data on DN yields from high energy fission-spallation


DN measurements from p (1GeV)+Pb at PNPI Gatchina (Russia)

Location of the experiment

SC

1 GeV protons ~20 nA

3He counter

Pb target

PNPI synchrocyclotron


He-3 counter calibration:252Cf neutron source + Monte Carlo

Proton beam monitoring:27Al foils and gamma spectroscopy from 22Na, 24Na and 7Be

Measurement strategy:a) No target at all – long irradiationsb) Concrete block – long irradiationc) Iron thick target – long irradiations

d) Lead target of variable thickness; short (350 μs), intermediate (20 s) and long (300 s) irradiations

Experimental strategy


Beam size/profile: by photo-films at exit and entrance positions

Beam intensity: by 27Al foils and gamma spectroscopy from 22Na, 24Na and 7Be

Proton beam monitoring

1GeV protons

Al foils

• 27Al(p,x)7Be monitor reaction cross section 7.5 ± 0.3 mb was taken as a reference• ratios of 24Na & 22Na with respect to 7Be were equal to 1.73 ± 0.15 & 1.99 ± 0.07

uncertainty in proton beam monitoring from 8 % to 12 %

Photo-films


Accumulated raw data


DN decay curve: p + natPb (55 cm)

Decay (s)1 10 210

coun

ts

-110

1

10

210

310

410

510Pb 55 cm

87Br

17N

88Br

9Li

background

50.809Li0.1784

95.1017N4.1733

6.5888Br16.292

2.5287Br55.601

Pn (β-n), %PrecursorHalf-life, sGroup

CTtatDN irradiii

i +−−−=∑ ))exp(1)(exp()( λλ

“Understandable” from x-sections

• p(1GeV)+Pb 9Li ~ 1000 μb• p(1GeV)+Pb 17N ~ 600 μb

• p(1GeV) +Pb 87Br ~30 μb

D. Ridikas et al., EPJ A (2007); in print


• Reproduced with 4 major contributions : 9Li, 17N, 88Br, and 87Br

DN decay curves: p + natPb


• The same 4 major contributions : 9Li, 17N, 88Br, and 87Br

DN decay curves: p + 209Bi


Experimental precursor yields (atoms/proton)

• Saturation is observed for targets thicker than 20 cm

• Similar shapes and absolute values both for Pb and Bi

17N

87Br

88Br

17N

87Br

88Br

)/( 3 cycleschpHeiii

n NtIaYP Δ= −ε

CTtatDN irradiii

i +−−−=∑ ))exp(1)(exp()( λλ

CatDNi

i +== ∑)0(

D. Ridikas et al., EPJ A (2007); in print


Precursor yields: data versus PHITS simulations

• INC (JAM) + EVAP(GEM) JAM: Jet AA Microscopic Transport ModelGEM: Generalized Evaporation ModelH. Iwase, K. Niita, T. Nakamura, Journal of Nuclear Science & Technology 39 (2002) 1142.

17N

87Br

88Br

Predictions within a factor of 2!


Extraction of x-sections : 17N & 87,88Br

p(1GeV)+A-->17N

0,01

0,10

1,00

10,00

100,00

0 50 100 150 200 250

A

sigm

a (m

b)

Dostrovsky'65Batist'77This work

Using thin targets

Br-35

1,0E-03

1,0E-02

1,0E-01

1,0E+00

1,0E+01

72 74 76 78 80 82 84 86 88 90A

sigm

a (m

b)MCNPX (INCL4+ABLA)PHITS(NMTC-JAM+GEM)GSI dataThis workGood agreement with old data

and/or systematics!


Conclusions and outlook

• importance of DNs in liquid metal targets for radioprotection issues • importance of the measurements to test model calculations

• DN yields and time spectra measured for the 1st time for p(1GeV) on thick natPb and Bi targets

• Estimates of errors on DN decay curves : below 20 %

• Major contributors are: 87Br, 88Br and 17N extraction of x-sections

• PHITS code “recommended” for such studies

• Consequences and “in-situ” experiment…


Absolute DN production yields: consequences

Assumption: p(1GeV) + Pb (55 cm thick; 10 cm ∅) at 1mA (1 MW)

~5⋅1010 n/s

~20 s after

Important data for:• SNS based on liquid metal targets• ToF facilities (DNs background neutrons)

Prompt neutrons

Delayed neutrons


~2-3m 3He

Time (x 200 ms)310

10

210

310

410

AμI = 250 I = 1.2 mA

DN spectra @ MEGAPIE (Preliminary)

U5 WD

Np Am

U5

Moniteurs

WD

WDU5

1 m

1,3 cm

U5 WD

Np Am

U5

Moniteurs

WD

WDU5

1 m

1,3 cm

Delayed neutrons

Prompt neutrons

1MW

prot

ons

Meg

aPie

targ

et

PbB

i

Fiss

ion

cham

bers

1MW

prot

ons

Meg

aPie

targ

et

PbB

i1M

Wpr

oton

s

Meg

aPie

targ

et

1MW

prot

ons

Meg

aPie

targ

et

PbB

i

Fiss

ion

cham

bers

CEA/DSM/DAPNIA’s contribution for MegaPie


MegaPie: geometrical model

top

Spallation region

up

down

down

up

Cross section S, cm2


MegaPie measurements PNPI data

( ) ( ) ( )( ) ( )( )

1 1

1 expexp

1 exp

n ni aa

i i i di i i

a x a x a xT

λτλτ

λ= =

− −= = −

− −∑ ∑

Use of parameters extracted from PNPI/Gatchina experiments

Estimates:τa ~0.5 s irradiationT ~20 s relaxationτd ~10 s heat exchanger


DN decay curves: Fe and “brick”

p + natFe 9Li, 17N, …

p + “brick” 9Li, 17N, …

p(1GeV) + natFe

p(1GeV) + “brick”

9Li17N


1. 252Cf neutron source at y = 170cm and different xmodeling with MCNPX: agreement within 5-6 %

He-3 counter calibration

0 10 20 30 40 50 60 703.63.84.04.24.44.64.85.05.25.45.65.86.06.2

Neu

tron

flux

, n/s

x 1

0-5

Target length, cm

Pb 01 MeV 05 MeV 1 MeV

2. Use of Monte Carlo withexact experimental conditionsvariable target thicknessvariable DN energy

estimated uncertainty below 10 %

3D modeling with Monte Carlo

yx

z

Eff

icie

ncy,

eve

nts/

s x 1

0-5


Photo of the experimental setup

He-3 neutron counter3He (8 atm.) + Ar(2 atm.)


Example (A)

• SNS, J-PARC, EURISOL liquid Hg• MegaPie, ADS liquid PbBi

SNS/ORNL - thanks to F. Gallmeier


Physics: ratios of relative yields relative to 87Br

901.4551021.3401181.3202351.4103541.75

a3(17N)/a1(87Br)a2(88Br)/a1(87Br)Target thickness, cm

121620.9755125640.8640159860.8920200890.95102351040.965

a4(9Li)/a1(87Br)a3(17N)/a1(87Br)a2(88Br)/a1(87Br)Target thickness, cm

Experiment

Confirmed by PHITS predictions

stable decreasing

Produced by different reaction mechanisms


DN yield as a function of incident neutron energy

Séminaire Saclay 53

n + U8 (n,f)

n

U8 (n,nf)

U7 (n,2nf)2n

U6 (n,3nf)

3n

Pa8

p

(n,pf)

U9

U5 (n,4nf)4n

Th5(n,αf)

α

6MeV

12 24 32

p(1GeV) + 238U in 2007

Thanks to P. Romain et al. CEA/DIF/DPTA What is beyond 20 MeV?


Why only 4 exponentials are sufficient?

1,0E-07

1,0E-06

1,0E-05

1,0E-04

1,0E-03

1,0E-02

1,0E-01

74 76 78 80 82 84 86 88 90 92 94 96 98

Mass A

yiel

d/fis

sion

p(1GeV)+Pbp(1GeV)+Un(14MeV)+Un(fiss)+U

U fission Pb fission; low energy high energy

Production of Br isotopes

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Measurements of DN Yields and Time Spectra from p(1 GeV ... · PDF file6-9 May 2007, SCK*CEN...

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