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The response of NE-102 plastic scintillator to stopped 3He nuclei
412
Nuclear Instruments and Methods in Physics Research A251 .(1986) 412-413 North-Holland, Amsterdam
Letter to the Editor T H E R E S P O N S E O F NE-102 P L A S T I C S C I N T I L L A T O R T O S T O P P E D 3He N U C L E I B.J. M c P A R L A N D * Department of Physics, University of British Columbia, Vancouver, BC, Canada V6T 1W5
3He nuclei, produced from the 6Li(cr+, 3He)3He reaction, were detected with NE-102 plastic scintillator telescopes. The relative light response of the scintillator to these nuclei is examined as a function of deposited energy ranging from 40 to 120 MeV.
The response of NE-102 plastic scintillator to stopped 3He nuclei has been measured for energies between 40 and 120 MeV. This response has also been compared to a calculation. 3He nuclei, produced from the 6Li(*r+, 3He)3He reaction for pion energies between 60 and 140 MeV, were detected in coincidence using NE-102 plastic scintillator telescopes [1]. Each telescope consisted of two 1 mm thick transmission counters and a 25.4 mm thick stopping counter, sufficient to stop the 3He nuclei (which had a maximum range of 14 mm in the scintillator). Each counter was sheathed in a 22 #m thick aluminum sheet. The telescope responses were calibrated using the 110 MeV protons produced from the *r+d---, 2p reaction using a heavy-water target at T, = 80 MeV. As these protons would pass completely through the stopping counter, a 35 mm thick aluminum degrader was placed between the heavy-water target and the telescope to reduce the mean proton energy incident to 30 MeV. The exact energies of the protons and 3He nuclei deposited in the stopping counter were estimated using a Monte Carlo code [2]. Using a result given by Wright [3], a parameterization of the light output generated by a charged particle stopping in plastic scintillator is, L = xf0Rln(1 + a I d E / d x l) dx,
protons and deuterons with energies up to 147.5 MeV and 120 MeV, respectively. Eq. (1) was evaluated via a numerical integration, where Gooding's and Pugh's value for a was used. d E / d x was calculated directly from the Bethe-Bloch equation for carbon and hydrogen, and Bragg's additivity rule was applied to determine the energy loss in NE-102 (CHu04). As a test of this method, the calculated light response for protons, deuterons, tritons and alphas were compared with those obtained by Gooding and Pugh who had used a power-law approximation for d E / d x . The agreement was excellent. Fig. 1 shows the relative light output calculated for
Protons
1.0 0.9 I.-
0.8
I-
0.7
0
i-
"l'-
0.6
He
-J 0.5
(1) -> 0.4
where h is a normalization constant, R is particle's range in scintillator, a is a constant extracted from a best fit to experimental data and d E / d x is the energy loss per unit path-length. Gooding and Pugh [4] determined a to be 23.6 ___2 m g / c m 2 MeV on the basis of measurements with low-energy protons (Tp < 14 MeV) [5]. This value agreed, to within experimental precision, with a value extracted from data taken with stopped
I-d
0.3
0.2 0.1 O' ~LZ~L9 20
40
Oe~ 0
i
60
80
INCIDENT
* Current address: Department of Clinical Physics, Princess Margaret Hospital, 500 Sherboume St.. Toronto, Ontario, Canada M4X 1K9. 0168-9002/86/$03.50 © Elsevier Science Publishers B.V. (North-Holland Physics Publishing Division)
I
|
,oo,2o
ENERGY
|
I
,4o,oo
(MeV)
Fig. 1. The relative light output for protons and 3He nuclei stopping in NE-102 plastic scintillator is shown as a function of incident energy. The curves are the responses calculated from eq. (1); the data are the measured 3He light responses.
B.J. McParland / Response of NE-102 plastic scintillator protons and 3He nuclei stopped in NE-102 plastic scintillator. The arbitrary normalization from Gooding's and Pugh's paper of a unity fight output for a stopped 160 MeV proton was also used here. The data are the 3He responses given by,
L. = Lp(A,/Ap),
(2)
where L v is the calculated relative light response for the stopped 0r+d-*2p proton and A T and Ap are the measured mean of the stopping counter's ADC response to 3He nuclei and protons, respectively. The errors shown ( ± l o ) are those due to the statistical uncertainty in estimating the proton and 3He ADC means only. In general, there is a fair agreement between the data and the calculation for deposited energies below 80 MeV. Above this point, the relative scintillation output measured is significantly less than that calculated. As the parameterization has been able to reproduce measured data for less densely-ionizing
413
protons and deuterons, this deviation suggests that a perhaps has a d E / d x dependence. The author thanks Dr. E.G. Auld for useful discussions. This work was supported in part by the Natural Sciences and Engineering Research Council of Canada.
References [1] B.J. McParland, E.G. Auld, P. Couvert, G. Giles, G. Jones, W. Ziegler, X. Aslanoglou, G.M. Huber, G.J. Lolos, S.I.H. Naqvi, Z. Papandreou, D.R. Gill, D.F. Ottewell and P.L. Walden, Phys. Lett. B156 (1985) 47. [2] B.J. McParland, Ph.D. Thesis, University of British Columbia (1985) unpublished. [3] G.T. Wright, Phys. Rev. 91 (1953) 1282. [4] T.J. Gooding and H.G. Pugh, Nucl. Instr. and Meth. 7 (1960) 189; 11 (1961) 365. [5] H.C. Evans and E.H. Bellamy, Proc. Phys. Soc. 74 (1959) 1483.
Nuclear Instruments and Methods in Physics Research A251 .(1986) 412-413 North-Holland, Amsterdam
Letter to the Editor T H E R E S P O N S E O F NE-102 P L A S T I C S C I N T I L L A T O R T O S T O P P E D 3He N U C L E I B.J. M c P A R L A N D * Department of Physics, University of British Columbia, Vancouver, BC, Canada V6T 1W5
3He nuclei, produced from the 6Li(cr+, 3He)3He reaction, were detected with NE-102 plastic scintillator telescopes. The relative light response of the scintillator to these nuclei is examined as a function of deposited energy ranging from 40 to 120 MeV.
The response of NE-102 plastic scintillator to stopped 3He nuclei has been measured for energies between 40 and 120 MeV. This response has also been compared to a calculation. 3He nuclei, produced from the 6Li(*r+, 3He)3He reaction for pion energies between 60 and 140 MeV, were detected in coincidence using NE-102 plastic scintillator telescopes [1]. Each telescope consisted of two 1 mm thick transmission counters and a 25.4 mm thick stopping counter, sufficient to stop the 3He nuclei (which had a maximum range of 14 mm in the scintillator). Each counter was sheathed in a 22 #m thick aluminum sheet. The telescope responses were calibrated using the 110 MeV protons produced from the *r+d---, 2p reaction using a heavy-water target at T, = 80 MeV. As these protons would pass completely through the stopping counter, a 35 mm thick aluminum degrader was placed between the heavy-water target and the telescope to reduce the mean proton energy incident to 30 MeV. The exact energies of the protons and 3He nuclei deposited in the stopping counter were estimated using a Monte Carlo code [2]. Using a result given by Wright [3], a parameterization of the light output generated by a charged particle stopping in plastic scintillator is, L = xf0Rln(1 + a I d E / d x l) dx,
protons and deuterons with energies up to 147.5 MeV and 120 MeV, respectively. Eq. (1) was evaluated via a numerical integration, where Gooding's and Pugh's value for a was used. d E / d x was calculated directly from the Bethe-Bloch equation for carbon and hydrogen, and Bragg's additivity rule was applied to determine the energy loss in NE-102 (CHu04). As a test of this method, the calculated light response for protons, deuterons, tritons and alphas were compared with those obtained by Gooding and Pugh who had used a power-law approximation for d E / d x . The agreement was excellent. Fig. 1 shows the relative light output calculated for
Protons
1.0 0.9 I.-
0.8
I-
0.7
0
i-
"l'-
0.6
He
-J 0.5
(1) -> 0.4
where h is a normalization constant, R is particle's range in scintillator, a is a constant extracted from a best fit to experimental data and d E / d x is the energy loss per unit path-length. Gooding and Pugh [4] determined a to be 23.6 ___2 m g / c m 2 MeV on the basis of measurements with low-energy protons (Tp < 14 MeV) [5]. This value agreed, to within experimental precision, with a value extracted from data taken with stopped
I-d
0.3
0.2 0.1 O' ~LZ~L9 20
40
Oe~ 0
i
60
80
INCIDENT
* Current address: Department of Clinical Physics, Princess Margaret Hospital, 500 Sherboume St.. Toronto, Ontario, Canada M4X 1K9. 0168-9002/86/$03.50 © Elsevier Science Publishers B.V. (North-Holland Physics Publishing Division)
I
|
,oo,2o
ENERGY
|
I
,4o,oo
(MeV)
Fig. 1. The relative light output for protons and 3He nuclei stopping in NE-102 plastic scintillator is shown as a function of incident energy. The curves are the responses calculated from eq. (1); the data are the measured 3He light responses.
B.J. McParland / Response of NE-102 plastic scintillator protons and 3He nuclei stopped in NE-102 plastic scintillator. The arbitrary normalization from Gooding's and Pugh's paper of a unity fight output for a stopped 160 MeV proton was also used here. The data are the 3He responses given by,
L. = Lp(A,/Ap),
(2)
where L v is the calculated relative light response for the stopped 0r+d-*2p proton and A T and Ap are the measured mean of the stopping counter's ADC response to 3He nuclei and protons, respectively. The errors shown ( ± l o ) are those due to the statistical uncertainty in estimating the proton and 3He ADC means only. In general, there is a fair agreement between the data and the calculation for deposited energies below 80 MeV. Above this point, the relative scintillation output measured is significantly less than that calculated. As the parameterization has been able to reproduce measured data for less densely-ionizing
413
protons and deuterons, this deviation suggests that a perhaps has a d E / d x dependence. The author thanks Dr. E.G. Auld for useful discussions. This work was supported in part by the Natural Sciences and Engineering Research Council of Canada.
References [1] B.J. McParland, E.G. Auld, P. Couvert, G. Giles, G. Jones, W. Ziegler, X. Aslanoglou, G.M. Huber, G.J. Lolos, S.I.H. Naqvi, Z. Papandreou, D.R. Gill, D.F. Ottewell and P.L. Walden, Phys. Lett. B156 (1985) 47. [2] B.J. McParland, Ph.D. Thesis, University of British Columbia (1985) unpublished. [3] G.T. Wright, Phys. Rev. 91 (1953) 1282. [4] T.J. Gooding and H.G. Pugh, Nucl. Instr. and Meth. 7 (1960) 189; 11 (1961) 365. [5] H.C. Evans and E.H. Bellamy, Proc. Phys. Soc. 74 (1959) 1483.