cosmogenic induced activity

Cosmogenic induced activityCosmogenic induced activity

Susana Cebrián [email protected]

University of Zaragoza (Spain)

IDEA (Integrated Double-beta decay European Activities)

Paris, 14th-15th April 2005

Task leaders: Maura Pavan, Susana Cebrián

mailto:[email protected]

Detailed implementation plan for first 18 months

Outline of the talk

• Task 2: final remarks

• Task 3: description and results of the activation study for Ge

• Task 4: points for discussion

• Outlook and summary

S. Cebrián, Cosmogenic Induced Activity IDEA meeting, Paris, April 2005

Poster “Cosmogenic activation of materials” presented at the “Low Radioactivity Techniques 2004” workshop, Sudbury (Canada), December 2004

(available at http://lrt2004.snolab.ca/talks/posters/irastorza-poster.pdf)

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http://lrt2004.snolab.ca/talks/posters/irastorza-poster.pdf

Task 2: Analysis of computational codes for n/p activation

DELIVERABLE: Report summarizing the features and limitations of codes:

• Target materials and product isotopes covered

• Projectiles allowed

• Range of applicable energies

• Physical models and/or experimental data sets for cross-sections

• Checks with experimental data

• “Technical” information: language, code source, support, ...

At IDEA website: http://idea.dipscfm.uninsubria.it/frontend/docs/reports/cosmogenics-task2.pdf


http://idea.dipscfm.uninsubria.it/frontend/docs/reports/cosmogenics-task2.pdf

Monte Carlo codes

+ neutron activation studies possible - very time-consuming (specially for some products)

General-purpose MC codes

+ wide coverage of projectiles, targets and energies in principle

+ easy availability and support

+ different models can be used for the hadronic physics

- not many comparisons with measurements of activation yields available

Semiempirical codes

+ wide coverage of targets and products

+ short calculation time and simplicity of use

- only proton-induced reactions

Conclusions for Task 2


Study using different codes and comparing with data when possible

Task 3: Comparison of results for some problems of interest

DELIVERABLE: Report comparing the performances of different codes

• Identification of the most reliable codes• Quantification of the uncertainties or spread in the estimates• Identification of weak points of codes for treating our problems

… and preliminary results for open questions in activation for DBD

Problem of activation in Ge

1. Excitation functions for relevant isotopes in Ge have been obtained

2. Rates of production by cosmic neutrons have been estimated and compared with previous results


Excitation functions for 60Co and 68Ge

• Experimental data with proton beams: in natural Ge:

Horiguchi’83 25-64 MeV Aleksandrov’91 660 MeV Norman’05 800 MeV

in 70Ge and 76Ge: NUCLEX 1000 MeV

• Calculations based on semiempirical Silberberg & Tsao formulas: YIELDX: p >100 MeV

• Calculations based on Monte Carlo codes: CEM p 100-1700 MeV ISABEL (by Majorana Collaboration) n <2000 MeV HMS-ALICE p, n <150 MeV MENDL-2 (using versions of ALICE) p <200 MeV, n <100 MeV

Thanks to S. Mashnik for providing us with his calculations with CEM and HMS-ALICE


Using the following data:

0,001

0,010

0,100

1,000

10,000

10 100 1000 10000energy (MeV)

pro

du

ctio

n c

ross

se

ctio

n (

mb

)

YIELDX (Silberberg &Tsao) Aleksandrov'91 Norman'05

MENDL-2P (p) MENDL-2 (n) CEM95 (p)

HMS-ALICE (p) HMS-ALICE (n)


60Co production in nat Ge

Differences at low energies between MENDL and HMS-ALICE calculations below a factor ~3

The most contributing energy region to the activation yield is 200-500 MeV, (~40% of the total)

for neutrons up to 3 times bigger that for protons

Measurements at 660 and 800 MeV agree very well with YIELDX (~15%)


60Co production in 70Ge and 76Ge

Calculations seem to overestimate these measurements, but they reproduce experimental data in nat Ge

in 76Ge are bigger than in 70Ge (from both calculations and measurements)

enrichment could be useless or even harmful for 60Co


68Ge production in nat Ge

Best agreement with measurements: YIELDX at high energy and HMS-ALICE at low energy

The most contributing energy region to the activation yield is up to ~100 MeV

for protons up to twice bigger that for neutrons


68Ge production on Ge isotopes

Increasing A between target and product makes cross sections decrease significantly in all estimates …

… except for YIELDX calculations, which however agree well with the experimental measurement

Cosmic neutron spectrum (E)

• Parameterization based on measurements:


)()( EEdER n

J. F. Ziegler, IBM Journal of Research and Development 42 (1998) 1.

E>20 MeV:4.5 10-3 n/cm2/s

dectt eeRA )1( exp


Rates of production

HMS-ALICE (<150 MeV)+YIELDX (≥ 150 MeV)

giving best agreement with measurements0.3+4.5=4.8 0.02+6.64=6.7

MENDL-2 (<100 MeV)+YIELDX (≥ 100 MeV)

maximal estimate of 0.16+4.81=5.0 ~0+6.8=6.8

Miley’92

Nucl. Phys. B (Proc. Suppl.) 28A (1992) 2124.8 3.5

SIGMA (GENIUS)

NIMA 481 (2002) 1496.4

SHIELD (GERDA)

GERDA meeting2.54 2.48

Production of 60Co (kg -1 d-1)natural Ge

enriched Ge (86% 76Ge, 14% 74Ge)

Maximum deviation: factor 2.6

Enrichment does not reduce significantly 60Co activation


HMS-ALICE (<150 MeV)+YIELDX (≥ 150 MeV)

giving best agreement with measurements77.1+11.8=88.9 2.8+10.4=13.2

MENDL-2 (<100 MeV)+YIELDX (≥ 100 MeV)

maximal estimate of 114.8+19.2=134.0 0.1+14.4=14.5

Miley’92 NPB (PS) 28A (1992) 212

26.5 1.2

Avignone’92

NPB (PS) 28A (1992) 280 experimental rates30±7

SIGMA (GENIUS)NIMA 481 (2002) 149

58.4

SHIELD (GERDA)GERDA meeting

101.22 5.42

Production of 68Ge (kg -1 d-1)natural Ge

enriched Ge (86% 76Ge, 14% 74Ge)

Enrichment reduces significantly 68Ge activation, but in different proportionsRates enhanced in some

estimates due to high cross sections at low energies

Maximum deviation: factor 5


• ALICE codes seem to be the most reliable at low energies and

semiempirical YIELDX at high energies

Conclusions for Task 3

Summary of the activation study in Ge

• Excitation functions have been described combining HMS-ALICE and

YIELDX results below and above 150 MeV

• Activity yields derived are acceptably compatible with other estimates for 60Co but quite bigger discrepancies arise for 68Ge

Conclusions regarding codes

to what extent are equal for neutrons and protons at medium-high energies? good prediction capabilities for proton production at low energies imply the same for neutron production ?

but …

Task 4: Preparation of n/p activation tests on targets of interest

GOAL: to measure the production cross-sections and/or rates of production with n/p beams on the targets of interest

Essential to validate calculations with different codes

• Ge: the most interesting irradiation experiment could be with neutrons at

low energies to shed light on production of 68Ge. The use of both natural and

enriched targets would be highly recommended.


Indications from the activation studies

• Te: the most uncertain region in the excitation function of 60Co is 1-3 GeV

Irradiation experiment underway at CERN with 1.4 GeV p

• target sample: natural or enriched?

• projectile: n or p?

• energy beam: mono-energetic?

• facility and time: for irradiation and for gamma-counting

Design of new irradiation experiments


An example of a possible experiment: 68Ge in Ge

• At Svedberg Laboratory (Sweden):

monoenergetic neutrons 25-180 MeV, ~5 105 n/cm2/s

• Rate of production of 68Ge in nat Ge (assuming =100 mb):

R = 1.6 104 s-1

• Activity in 68Ge after 1 h of irradiation:

A = 1.7 Bq = 1.5 105 d-1

• Gamma counting at 1077 keV line (3%):

~440 counts/d

WP Task

9.R2 - Table 1 – IDEA - Second 18 months Execution Plan

13st to 18th month (1.04.2005-30.09.2005)

19th to 24th month(1.10.2005-31.03.2006)

25th to 30th month(1.04.2006-30.09.2006)

4 B1

Tasks

- Up-grade and development of simulation codes

- Upgrading of existing codes for n/p activation- Design of further n/p activation tests on Ge and TeO2

- further n/p activation experiments

- Start-up of tests at CERN and other labs on Ge and TeO2

Milestones and Delivera

bles

- Upgraded codes for n/p activation and related technical report

- progress report

Outlook


Summary

• The analysis of computational codes for n/p activation is

completed and the report is available

• A study of activation in Te and Ge for isotopes relevant in

DBD is underway, using available experimental data and

different calculations. Preliminary conclusions have been

drawn.


• The preparation of new activation experiments has just

been started up

cosmogenic induced activity

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