LIGHT-OUTPUT SIMULATIONS FOR NEDA

Andrea Gottardo

Università di Padova

“Universa Universis Patavina Libertas”

20/04/23 1NEDA meeting

Plan of presentation Introduction : The importance of light-output

response in scintillators Calculations for light-output produced by neutrons Light-output spectra First estimations of efficiency and cross-talk for

NEDA Conclusions

20/04/23 2NEDA meeting

Light-output response: why?

The light-output response of a scintillator has to be addressed carefully when estimating the efficiency or the cross-talk effect

In fact, the actual signal intensity from a PMT depends on the light-output.

electronics

PMTlightNeutron

Scintillatorcharge

Neutrons with the same energy do not always produce the same light output, i.e. the same signal intensity

20/04/23 3NEDA meeting

Scintillator light response

The light-response depends on:

• The energy of the particle(s) scattered by collisions with the incoming neutrons

• The kind of the particle(s) scattered by collisions with the incoming neutrons

• Other characteristics of the scintillator such as the optical coupling to the PMT, the light transport and reflection in the scintillator itself…

20/04/23 4NEDA meeting

Light-output importance for NEDA

Simulation for neutron detectorRealistic estimation of the intensity of output signals

J. Ljungvall et al., NIM A 528 (2004), 741.

The final goal is to obtain a credible evaluation of some key parameters such as efficiency and cross talk

NEDA as multiplicity filter to select n-rich reaction channels

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Light-output definitionThe light-output L is usually given in MeVee: the particle energy required to generate 1 MeVee of light is defined as 1 MeV for fast electrons

L is generally less for heavier particles such as protons, deuterons, alphas, beryllium, carbon…

Therefore, the light output L in a certain path dx is a function of the deposited energy E in dx: L(E)

e- @ 1 MeV PMTLight: 1MeVee

e- range

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Light-output estimation

The Birks-Chou formula provides a theoretical description of the light emission

However, an easier phenomenological formula is also available

ΔL = light output of the particle scattered by a neutron in a single ith step of its stopping process E

E - ΔE

i

iLL

12

1

dx

dEC

dx

dEkB

dx

dES

dx

dL

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Light output parametrization (1) Dekempeneer et Liskien NIM A 256 (1987) 489-498: NE213

The light-output function provided for protons is a polynomial one (3rd order ) : LP(E)=A0+A1E+A2E2+A3E3

Carbon, Boron: L(E) = 0.0097 E

Deuteron: L(E) = 2 Lp(E/2)

Alpha: L(E) = •0.0201E1.871 E < 6.76 MeV•-0.6278+0.1994 E E ≥ 6.76 MeV

Be: L(E) = 0.013E

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Light output parametrization (2) Many parameterizations exist in literature, also for energies above 16 MeV.

R.A. Cecil et al. NIM 161 (1979) 439-447, for example

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N.P. Hawks et al., NIM A 476 (2002) 190

D. Cano-Ott and collaborators, private comm.

Light output parametrization (3)

Gaussian resolution for L2222 Y+Lβ+LμFWMH

µ = 0.045

β = 0.075

Y = 0.002H. Schölermann and H. Klein, NIM 169 (1980), 25

The resolution describes:

1. Light transmission from different points (µ)

2. Statistical effects on light production (β)

3. Noise (Y)

20/04/23 10NEDA meeting

Light output for 10 MeV neutrons(electrons)

Deposited energy Light output

10* keV 10 * keVee16/06/2009 11NEDA meeting20/04/23 11NEDA meeting

Light output for 10 MeV neutrons(protons)

Deposited energy Light output

10 * keV 10 * keVee20/04/23 12NEDA meeting

Light output for 10 MeV neutrons(carbon)

Deposited energy Light output

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Light output for 10 MeV neutrons(alphas from 12C+n->9Be+4He)

Deposited energy Light output

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Light output for 10 MeV neutrons(9Be from 12C+n->9Be+4He)

Deposited energy Light output

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Light output for 10 MeV neutrons(deuterons)

Deposited energy Light output

10 * keV 10 * keVee20/04/23 16NEDA meeting

Light output for 10 MeV neutrons(all)

Deposited energy Light output

10 * keV 10 * keVee20/04/23 17NEDA meeting

EfficiencyThe efficiency of the NEDA prototype is calculated for an emission at 1m distance with an angular aperture of θ =14°

20/04/23 18NEDA meeting

θ

1 m

source

The efficiency has been calculated for 4 different thresholds as:

sentN

Neff 1

Tayfun Huyuk,

private comm.

16/06/2009 NEDA meeting 19

Efficiency: resultsThreshold

(MeVee)Efficiency

%

0 74.6

0.25 6.5

0.50 6.0

0.75 5.5

Threshold (MeVee)

Efficiency%

0 63.6

0.25 40.1

0.50 36.2

0.75 33.1

10 keVee

10 keVee

1 MeV n

8 MeV n

0.75

0.25

0.50

0.25

0.50

0.75

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Cross talk

n

n'

Cross talk: the same neutron can be scattered and detected among different scintillators

hit

hits

N

N

1

2Cross talk:

We calculated it for 19 detectors, in the same conditions as the efficiency simulation

20/04/23 20NEDA meeting

Tayfun Huyuk,

private comm.

Threshold (MeVee)

Cross talk%

0 46.8

0.25 16.2

0.50 8.7

0.75 3.8

Threshold (MeVee)

Cross talk%

0 39.4

0.25 17.6

0.50 12.0

0.75 8.3

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10 keVee

10 keVee

0.75

0.25

0.50

0.25

0.50

0.75

1 MeV n

8 MeV n

Cross talk: results

Conclusions and open problems

1. What parameterization to be used?

2. Is the light-output really a universal function?

3. Need to test the scintillator to validate simulations?

20/04/23 22NEDA meeting

Several available, situation more confused for energies above 16 MeV

We have implemented in Narray code the calculations for the light output of a scintillator, considering the different kinds of recoils involved.

HOWEVER…

Light output for 10 MeV neutrons(photons)

Deposited energy Light output

10 keV 10 keVee16/06/2009 23NEDA meeting20/04/23 23NEDA meeting