Bertolini, G.

Cappellani, F.

Fumagalli, W.

Henuset, M.

Restelli, G.

Archive of European Integration

LITHIUM DRIFTED SEMICONDUCTOR DETECTORS 
U I N N U C L E A R SPECTROSCOPY { § ¡ f | 
bv lili-
^¿ΓΓ.ΓITU*, 'i!' 'aiii! 
G. BERTOLINI, F. CAPPELLANI, W. FUMAGALLI, M. HENUSET 
and G. RESTELLI 
1965 
f Sit!. ':.;:· ¿-tfijjN-
.. -.,JliáiÉA 
Joint Nuclear Research Center 
Ét 
Ispra Establishment — Italy 
Chemistry Department 
Nuclear Chemistry Service #\m 
This document was prepared under the sponsorship of the Commission 
of the European Atomic Energy Community (EURATOM). 
Neither the EURATOM Commission, its contractors nor any person ÆiMEnma Nei 
Φ ΐ Ι Ι Ι Ε β a"80ntheirbeha^æiiiiiiiil' 
¡pä 
Make any warranty or representation, express or implied, with respect 
to the accuracy, completeness, or usefulness of the information con­
tained in this document, or that the use of any information, apparatus, 
method, or process disclosed in this document may not infringe privately 
owned rights; or 
Assume any liability with respect to the use of, or for damages resulting 
A . , ™ , + U ~ ,,,.,» „ £ : _ Γ „ _ _ „ ^ : _^__ ι i t- ι ι 
fri, ukit J 
E U R 2580.e 
LITHIUM DRIFTED SEMICONDUCTOR DETECTORS IN NUCLEAR 
SPECTROSCOPY by G. BERTOLINI, F. CAPPELLANI, W. FUMAGALLI, 
M. HENUSET and G. RESTELLI 
European Atomic Energy Community - EURATOM 
Joint Nuclear Research Center - Ispra Establishment (Italy) 
Chemistry Department - Nuclear Chemistry Service 
Brussels, November 1965 - 10 Pages - 6 Figures - FB 25 
Results obtained in beta and gamma spectroscopy, together with short details 
on the construction of silicon and germanium Li-drifted detectors are presented. 
E U R 2580.e 
LITHIUM DRIFTED SEMICONDUCTOR DETECTORS IN NUCLEAR 
SPECTROSCOPY by G. BERTOLINI, F. CAPPELLANI, W. FUMAGALLI, 
M. HENUSET and G. RESTELLI 
European Atomic Energy Community - EURATOM 
Joint Nuclear Research Center - Ispra Establishment (Italy) 
Chemistry Department - Nuclear Chemistry Service 
Brussels, November 1965 - 10 Pages - 6 Figures - FB 25 
Results obtained in beta and gamma spectroscopy, together with short details 
on the construction of silicon and germanium Li-drifted detectors are presented. 
E U R 2580.e 
LITHIUM DRIFTED SEMICONDUCTOR DETECTORS IN NUCLEAR 
SPECTROSCOPY by G. BERTOLINI, F. CAPPELLANI, W. FUMAGALLI, 
M. HENUSET and G. RESTELLI 
European Atomic Energy Community - EURATOM 
Joint Nuclear Research Center - Ispra Establishment (Italy) 
Chemistry Department - Nuclear Chemistry Service 
Brussels, November 1965 - 10 Pages - 6 Figures - FB 25 
Results obtained in beta and gamma spectroscopy, together with short details 
on the construction of silicon and germanium Li-drifted detectors are presented. 

EUR 2S80.e 
EUROPEAN ATOMIC ENERGY COMMUNITY — EURATOM 
LITHIUM DRIFTED SEMICONDUCTOR DETECTORS 
IN NUCLEAR SPECTROSCOPY 
by 
G. BERTOLINI, F. CAPPELLANI, W. FUMAGALLI, M. HENUSET 
and G. RESTELLI 
1965 
Joint Nuclear Research Center 
Ispra Establishment — Italy 
Chemistry Department 
Nuclear Chemistry Service 

- 3 -
LITHIUM DRIFTED SEMICONDUCTOR DETECTORS IN NUCLEAR 
SPECTROSCOPY 
INTRODUCTION (°) 
The construction and performances of lithium drifted semi-
conductor detectors as spectrometers, have been extensively descri-
bed in literature (1) 
The intrinsic high resolution of these detectors together 
with the development of low noise preamplifiers, allow a very good 
resolution, either in beta either in gamma spectroscopy, respecti-
vely by Si and Ge detectors. 
The results obtained in the study of alpha particle ioniza-
tion in gases on the Pano factor (F^L0,08) (2) and those obtained 
in electron spectroscopy by surface barrier detectors (3) (fwhm = 
./. 
(1) - F.S. GOULDING : I.E.E.E. NS-11 n° 3 - (1964) - 177 
(2) - VOROBYOV : private communication 
(3) - H.J. LANGMANN and 0. MEYER : Nucl. Instr.&Meth. 30 (1964) 135 
(°) Manuscript received on August ?1, 1965 
= 2.9 KeV for 624 KeV electrons with 2.7 KeV for electronics) seem 
to indicate that the ultimate limit in resolution also in semicon­
ductor detectors is not yet achieved and is practically conditioned 
by the construction technology and the electronic noise. 
In this paper we present a short description of the techniques 
used in this laboratory in the construction and some examples of the 
utilization of these detectors in electron and gamma spectroscopy. 
CONSTRUCTION; 
The procedure followed in the construction of the detectors 
is based on the results obtained by Pell (4) on lithium drifting in 
ρ ­ n junctions. 
Li diffuses interstitially in Si and Ge, with an higher mobi­
lity in the second one. 
Nevertheless while silicon diodes can be drifted at tempera­
ture of the order of 150°C or more depending on the resistivity of 
the starting material, germanium diodes have been drifted at tempe­
ratures of the order of 60° ­ 70°C at maximum. 
This limit is imposed by the higher thermally generated cur­
rent due to the lower energy gap (Ge : 0,63 ev ­ Si : 1,04 ev). 
P­type silicon crystals ranging in resistivity from 100 to 1500 
ilcm and p­type Germanium of resistivity 5­10Ücm, have been used. 
In the case of Ge, dislocation density in the starting mate­
rial is a very critical point because dislocations in the crystal 
act as nucleation points for Lithium precipitation : an EPD at least 
­2 below 2000 cm is necessary. 
Lithium metal is evaporated in vacuum on one face of the 
etched crystal and then diffused in argon flow at temperatures of 
respectively 400°C for Si and 350°C for Ge. 
Electroless Ni plating provides ohmic contacts. 
The drift is performed in air using an automatic system of 
control of the drift temperature and of the power dissipated into 
the diode (5). 
./. 
(4) ­ E.M. PELL : J. Appi. Phys. : 31 (1960) 291. 
(5) ­ G. DEARNALEÏ, G.C. LEWIS : AERE R­4335 (I963). 
­ 5 ­
Drifted depths are determined by capacitance measurements and 
stain techniques. In the case of Silicon, in order to get windowless 
type detectors for electron and low energy gamma spectroscopy, the 
diode is drifted to the opposite side and then a surface barrier is 
produced on this side by etching and subsequent gold evaporation 
(n +­i­p+) (5). Sensitive depths of the order of 8 mm in Silicon and 
χ 7 mm in Germanium have been obtained with useful areas up to 3 cm 
The storage of Si detectors does not present problems: although 
not necessary the continuous application of a 50­100 volt bias to the 
diodes improves the lithium compensation. Por Ge detectors the only 
efficient storage v/ö have found, is in vacuum at liquid nitrogen tem­
perature: in these conditions detectors have been operated for months 
without appreciable worsening of the characteristics. 
SILICON DETECTOR: 
The application of this detector in nuclear spectroscopy seems 
to fit particularly measurements of beta spectra and internal conver­
sion electrons. 
Its utilization as gamma spectrometer is drastically limited 
to low energy gammas and XL­rays due to the low absorption efficiency 
and atomic number of Silicon. 
Sometimes the use of silicon can be preferred to germanium when 
it is of interest to evidenciate a peak respect to a near one of higher 
energy and intensity. A typical gamma spectrum is shown in fig. 1. In 
the application to electron and beta spectroscopy, the detectors are 
operated at about 255°K using a Peltier effect device. The resolutions 
obtained are of the order of 7 KeV for conversion electrons of Cd 109 
2 88 KeV and Cs 137 661 KeV gammas, for a 50 mm χ 2 mm detector. (6) 
Resolutions of 7 KeV for the conversion electrons of the 661 KeV 
2 gamma of Cs 137 for a 250 mm χ 3 mm detector have been obtained by 
cooling at 190° K. 
In a previous paper (7) we have pointed out, referring to sur­
face barrier detectors, the importance of the knowledge of the backseat­
./. 
(6) ­ G. BERTOLINI, P. CAPPELLANI, G. RESTELLI: Nucí. Inst, and Meth. 
32 (1965) 86. 
(7) ­ G. BERTOLINI, P. CAPPELLANI, R. PANTECHI, G. RESTELLI: Nucl. Inst. 
and Meth. 2? (1964) 281 . 
­ 6 ­
tering tail associated to the electron peaks of different energies, 
to give a correct interpretation of the continuous beta spectra. 
The knowledge of the backscattering is obviously required also 
to make evaluations of internal conversion coefficients. 
In the study of radioactivity of U 232 (8) in the determination 
of Ζ conversion ratios for the 58 and 128 KeV transitions (fig. 2) it 
M has been observed that this ratio would be affected by an error of 
about 15$ for the 58 KeV conversion electrons and of the order of 5$ 
for the 128 KeV conversion electrons, if the backscattering is not 
taken into account. 
The error becomes much higher, of course, if the evaluation is 
made for peaks quite far in energy; as for instance for K/L ratios. 
GERMANIUM DETECTOR: 
In our laboratory at this moment, germanium detectors find 
their applications in activation analysis and in heavy elements studies. 
A problem treated in activation analysis was the determination 
of hafnium in hafnium depleted zirconium oxide; this is of interest 
due the importance of the problem in nuclear technology and also on 
account of the difficulty to perform a chemical separation between 
Hf and Zr. By a scintillation spectrometer, namely a Nai (Tl) 3" x 
χ 3" crystal, an evaluation is impossible for Hf content bäow 100 
ppm (9)· 
Fig. 3 ­ 4 and 5 show gamma spectra taken by a Ge detector of 
pure Hf02, of natural zirconium containing 2$ of Hf and finally of 
a depleted sample with unknown Hf content. 
The determination can be performed using either the 130 KeV 
or the 480 KeV gamma line of Hf 131 ; a content of about 100 ppm has 
been obtained with good agreement between the values (93 and 103 ppm 
respectively) resulting from the two peaks. The estimated sensitivity 
of the method is 10 ppm. 
In heavy elements the presence of a certain number of gamma and 
ζΔ 
(8) ­ G. BERTOLINI, P. CAPPELLANI, G. RESTELLI, H.L. SCHERPP: Nuclear 
Physics to be published. 
(9) ­ Y. KAMEMOTO, S. ÏAMAGISHI: Nippon Kagaku Zasshi 84 (1963) 270. 
- ν -
Xrays peaks of near energy inhibits a good determination of energies 
and relative intensities of the radiations. 
Fig. 6 shows a gamma spectrum from a source of Pu 240 of the 
following isotopie composition: 
Pu 239 : 2,96 % 
Pu 240 : 96,8 % 
Pu 241 : 0,2 $ 
Pu 242 : 0,03 $ 
From the spectrum the relative intensities of the gamma transi­
tions with respect to the total alpha transitions have been determi­
ned. Taille I shows the data obtained compared with those in ref. 10. 
The total conversion coefficients for the 45 and 104 KeV tran­
sitions are reported together with the theoretical values calculated 
for E 2 transitions. 
The conversion coefficients for the 163 and 210 KeV gamma are 
not given due to the strong dependence on the alpha branching (11) 
and decay scheme assumed. 
T A B L E I 
GAMMA ! Gamma intensities ! _ „ „_ ! Total conversion coefficients 
Ref. 10 Energy ! $ of decay ! * ! experimental !(E2) theoretical 
45 KeV ! 4,5 x 10~2 !3,6 χ 1Ò"2! 540 ! 613 
104 KeV ! 7,1 x 10~3 !9,1 x 1Õ3! 11,8 ! 11,35 
163 KeV ! 4,7­°,5x 10~4 !5,1 x 1Õ4! ! 
210 KeV ! 4,2Í0,6x 10~4 !4,8 χ 1Õ4! ! 
X KL ! 5,3 x 1θ"4 ! ! ! 
X KM­N ! 1,43 x 10­3 ! ! ! 
Acknowledgments: The autors are indebted to R. BENOIT for designing 
the low noise preamplifiers, to the activation analysis group for the 
Hf determination and to A. OSTIDICH for preparation of Plutonium sources, 
(10) ­ J.E. CLINE: IDO 16695 (1961) 43 
(11) ­ E.F'. TRET'YAKOV, L.N. KONDRAT'EV, G.I. KHLEBNIKOV and L.L. 
GOL'DIN, JETP 9 (1959) 250. 
I/I 
c 
O 
«10 
8 -
6-
4 -
2-
0 
U-NpXL 
I 
50 
"40 \ 
100 
Pu 240 + Am 2 41 y SPECTRUM 
S i - L i DRIFTED DETECTOR 
3 0 0 m m z " 2.2 mm 77° K 
Am 241 59.6 KeV 
Pu 240 45KeV / \ 
o / \ 3.3 KeV f w h m 
150 channel 200 
Fig.1 
V) 
c 
o υ 
10-
8-
6 -
4 -
-
2-
«10* 
BACKSC. J 
LEVEL β .JSJ Λ.. 
Ó 
58 KeV 
*L «M 
40 53.5 1 1 
—' \ 
50 
χ102 
/ 
100 
128 KeV 
* L eM 
110 123.5 KeV 
\ \ 
u 2 3 2 
CONVERSION ELECTRONS 
Si - LITHIUM DRIFTED DETECTOR 
50mm2»2mm 260°K 
/ V 
150 channel 
Fig.2 
«10* 
W ) 1 2 H 
c 
S10-
8-
6-
4 -
2-
0 
Hf-181 
133+136 KeV i 
« ^ 
\ 
-10 χ ^ 
u-
I 
50 
Hf 02 
Hf-181 
346 KeV 
\ 
fl 
*~ΛΙ V 
too 
Hf-181 
482KeV 1 
150 200 250 3Ò0 channel 350 
Fig.3 
χ10' 
c 
Í4- I o 
2-
Hf-181 
133+136 KeV ZrO- + 27.Hf 
Hf-181 
346 Κ eV 
Hf-181 
482 KeV 
200 
Fig.4 
250 300channel ÍÍÕ 
xlO4 
8 -
in 
c -
D O O 
6 -
4 -
2-
ír 
Î Hf-181 
1133-136 KeV 1 
50 
p 
302 : 
II 
"5 
J 
a 233 
Î12 340 KeV 
1 
Hf-181 
346KeV 1 
100 150 
Ge- 250mm2 »2mm 
Zr + Hf 103ppm 
Hf-181 Nb-97 Zr-96 
482 KeV 665KeV 723 756KeV 
J 1 π 
A ^ " \ Nb-97 Nb-95 
\ 750 KeV 764KeV 
\ ñ¥ 
200 250 300 channel 
Fig. 5 
0- 10 
c 
D O 
8-
6- q 
2-
45 KeV 
PU 240 GAMMA SPECTRUM 
250mm2x2.5mm 
77° K 
104 KeV 163 KeV 210 KeV I 
350 channel 400 
Fig.6 
mW 
To disseminate knowledge is to disseminate prosperity — I mean 
general prosperity and not individual riches — and with prosperity 
disappears the greater part of the evil which is our heritage from 
«Mil» Pi 
nmt', ml 
iiça 
mm 
:mm mMåk 
SALES OFFICES 
All Euratom reports are on sale at the offices listed below, at the prices given on the back of the 
cover (when ordering, specify clearly the EUR number and the title of the report, which are shown 
on the cover). 
m£j 
PRESSES ACADEMIQUES E U R O P E E N N E S 
98, Chaussée de Charleroi, Bruxelles 6 
Banque de la Société Générale - Bruxelles 
compte N° 964.558, 
Banque Belgo Congolaise - Bruxelles 
compte N° 2444.141, 
Compte chèque postal - Bruxelles - N° 167.37, 
Belgian American Bank and Trust Company - New 
compte No. 22.186, 
Lloyds Bank (Europe) Ltd. - 10 Moorgate, London E.C.2, 
Postcheckkonto - Köln - Nr. 160.861 
h »iirtfr !''*5!tá*r¡W 
OFFICE CENTRAL D E V E N T E DES PUBLICATIONS 
DES COMMUNAUTES E U R O P E E N N E S 
2. place de Metz, Luxembourg (Compte chèque postal N° 191-90) 
W 
il Ite:»» 
BELGIQUE — BELGIË 
MONITEUR BELGE 
40-42, rue de Louvain - Bruxelles 
BELGISCH STAATSBLAD 
Leuvenseweg 40-42 - Brussel 
D E U T S C H L A N D 
BUNDESANZEIGER 
Postfach - Köln 1 
U-'l 1 · ' 
mim 
G R A N D - D U C H E D E L U X E M B O U R G 
OFFICE CENTRAL DE VENTE 
DES PUBLICATIONS DES 
COMMUNAUTES EUROPEENNES 
9, rue Goethe - Luxembourg 
F R A N C E 
SERVICE DE VENTE EN FRANCE 
DES PUBLICATIONS DES 
COMMUNAUTES EUROPEENNES 
26, rue Desaix - Paris 15e 
É^îf l- '
: i <"t , f ,MÏ'1 ' ' ' 
»»¡/M *: Mer is iä ii usi ITALIA LIBRERIA DELLO STATO Piazza G. Verdi, 10 - Roma 
3 
TiSÉ 
N E D E R L A N D 
STAATSDRUKKERIJ 
Christoffel Plantijnstraat - Den Haag 
t i i [wuMmn 
EURATOM — C.I.D. 
51-53, rue Belliard 
Bruxelles (Be lg ique ) 
CDNA02580ENC 
mmm ¡HH 


Lithium Drifted Semiconductor Detectors in Nuclear Spectroscopy. EUR 2580.

LITHIUM DRIFTED SEMICONDUCTOR DETECTORS U I N N U C L E A R SPECTROSCOPY { § ¡ f | bv lili-^¿ΓΓ.ΓITU*, 'i!' 'aiii! G. BERTOLINI, F. CAPPELLANI, W. FUMAGALLI, M. HENUSET and G. RESTELLI 1965 f Sit!. ':.;:· ¿-tfijjN-.. -.,JliáiÉA Joint Nuclear Research Center Ét Ispra Establishment — Italy Chemistry Department Nuclear Chemistry Service #\m This document was prepared under the sponsorship of the Commission of the European Atomic Energy Community (EURATOM). Neither the EURATOM Commission, its contractors nor any person ÆiMEnma Nei Φ ΐ Ι Ι Ι Ε β a"80ntheirbeha^æiiiiiiiil' ¡pä Make any warranty or representation, express or implied, with respect to the accuracy, completeness, or usefulness of the information con­tained in this document, or that the use of any information, apparatus, method, or process disclosed in this document may not infringe privately owned rights; or Assume any liability with respect to the use of, or for damages resulting A . , ™ , + U ~ ,,,.,» „ £ : _ Γ „ _ _ „ ^ : _^__ ι i t- ι ι fri, ukit J E U R 2580.e LITHIUM DRIFTED SEMICONDUCTOR DETECTORS IN NUCLEAR SPECTROSCOPY by G. BERTOLINI, F. CAPPELLANI, W. FUMAGALLI, M. HENUSET and G. RESTELLI European Atomic Energy Community - EURATOM Joint Nuclear Research Center - Ispra Establishment (Italy) Chemistry Department - Nuclear Chemistry Service Brussels, November 1965 - 10 Pages - 6 Figures - FB 25 Results obtained in beta and gamma spectroscopy, together with short details on the construction of silicon and germanium Li-drifted detectors are presented. E U R 2580.e LITHIUM DRIFTED SEMICONDUCTOR DETECTORS IN NUCLEAR SPECTROSCOPY by G. BERTOLINI, F. CAPPELLANI, W. FUMAGALLI, M. HENUSET and G. RESTELLI European Atomic Energy Community - EURATOM Joint Nuclear Research Center - Ispra Establishment (Italy) Chemistry Department - Nuclear Chemistry Service Brussels, November 1965 - 10 Pages - 6 Figures - FB 25 Results obtained in beta and gamma spectroscopy, together with short details on the construction of silicon and germanium Li-drifted detectors are presented. E U R 2580.e LITHIUM DRIFTED SEMICONDUCTOR DETECTORS IN NUCLEAR SPECTROSCOPY by G. BERTOLINI, F. CAPPELLANI, W. FUMAGALLI, M. HENUSET and G. RESTELLI European Atomic Energy Community - EURATOM Joint Nuclear Research Center - Ispra Establishment (Italy) Chemistry Department - Nuclear Chemistry Service Brussels, November 1965 - 10 Pages - 6 Figures - FB 25 Results obtained in beta and gamma spectroscopy, together with short details on the construction of silicon and germanium Li-drifted detectors are presented. EUR 2S80.e EUROPEAN ATOMIC ENERGY COMMUNITY — EURATOM LITHIUM DRIFTED SEMICONDUCTOR DETECTORS IN NUCLEAR SPECTROSCOPY by G. BERTOLINI, F. CAPPELLANI, W. FUMAGALLI, M. HENUSET and G. RESTELLI 1965 Joint Nuclear Research Center Ispra Establishment — Italy Chemistry Department Nuclear Chemistry Service - 3 -LITHIUM DRIFTED SEMICONDUCTOR DETECTORS IN NUCLEAR SPECTROSCOPY INTRODUCTION (°) The construction and performances of lithium drifted semi-conductor detectors as spectrometers, have been extensively descri-bed in literature (1) The intrinsic high resolution of these detectors together with the development of low noise preamplifiers, allow a very good resolution, either in beta either in gamma spectroscopy, respecti-vely by Si and Ge detectors. The results obtained in the study of alpha particle ioniza-tion in gases on the Pano factor (F^L0,08) (2) and those obtained in electron spectroscopy by surface barrier detectors (3) (fwhm = ./. (1) - F.S. GOULDING : I.E.E.E. NS-11 n° 3 - (1964) - 177 (2) - VOROBYOV : private communication (3) - H.J. LANGMANN and 0. MEYER : Nucl. Instr.&Meth. 30 (1964) 135 (°) Manuscript received on August ?1, 1965 = 2.9 KeV for 624 KeV electrons with 2.7 KeV for electronics) seem to indicate that the ultimate limit in resolution also in semicon­ductor detectors is not yet achieved and is practically conditioned by the construction technology and the electronic noise. In this paper we present a short description of the techniques used in this laboratory in the construction and some examples of the utilization of these detectors in electron and gamma spectroscopy. CONSTRUCTION; The procedure followed in the construction of the detectors is based on the results obtained by Pell (4) on lithium drifting in ρ ­ n junctions. Li diffuses interstitially in Si and Ge, with an higher mobi­lity in the second one. Nevertheless while silicon diodes can be drifted at tempera­ture of the order of 150°C or more depending on the resistivity of the starting material, germanium diodes have been drifted at tempe­ratures of the order of 60° ­ 70°C at maximum. This limit is imposed by the higher thermally generated cur­rent due to the lower energy gap (Ge : 0,63 ev ­ Si : 1,04 ev). P­type silicon crystals ranging in resistivity from 100 to 1500 ilcm and p­type Germanium of resistivity 5­10Ücm, have been used. In the case of Ge, dislocation density in the starting mate­rial is a very critical point because dislocations in the crystal act as nucleation points for Lithium precipitation : an EPD at least ­2 below 2000 cm is necessary. Lithium metal is evaporated in vacuum on one face of the etched crystal and then diffused in argon flow at temperatures of respectively 400°C for Si and 350°C for Ge. Electroless Ni plating provides ohmic contacts. The drift is performed in air using an automatic system of control of the drift temperature and of the power dissipated into the diode (5). ./. (4) ­ E.M. PELL : J. Appi. Phys. : 31 (1960) 291. (5) ­ G. DEARNALEÏ, G.C. LEWIS : AERE R­4335 (I963). ­ 5 ­Drifted depths are determined by capacitance measurements and stain techniques. In the case of Silicon, in order to get windowless type detectors for electron and low energy gamma spectroscopy, the diode is drifted to the opposite side and then a surface barrier is produced on this side by etching and subsequent gold evaporation (n +­i­p+) (5). Sensitive depths of the order of 8 mm in Silicon and χ 7 mm in Germanium have been obtained with useful areas up to 3 cm The storage of Si detectors does not present problems: although not necessary the continuous application of a 50­100 volt bias to the diodes improves the lithium compensation. Por Ge detectors the only efficient storage v/ö have found, is in vacuum at liquid nitrogen tem­perature: in these conditions detectors have been operated for months without appreciable worsening of the characteristics. SILICON DETECTOR: The application of this detector in nuclear spectroscopy seems to fit particularly measurements of beta spectra and internal conver­sion electrons. Its utilization as gamma spectrometer is drastically limited to low energy gammas and XL­rays due to the low absorption efficiency and atomic number of Silicon. Sometimes the use of silicon can be preferred to germanium when it is of interest to evidenciate a peak respect to a near one of higher energy and intensity. A typical gamma spectrum is shown in fig. 1. In the application to electron and beta spectroscopy, the detectors are operated at about 255°K using a Peltier effect device. The resolutions obtained are of the order of 7 KeV for conversion electrons of Cd 109 2 88 KeV and Cs 137 661 KeV gammas, for a 50 mm χ 2 mm detector. (6) Resolutions of 7 KeV for the conversion electrons of the 661 KeV 2 gamma of Cs 137 for a 250 mm χ 3 mm detector have been obtained by cooling at 190° K. In a previous paper (7) we have pointed out, referring to sur­face barrier detectors, the importance of the knowledge of the backseat­./. (6) ­ G. BERTOLINI, P. CAPPELLANI, G. RESTELLI: Nucí. Inst, and Meth. 32 (1965) 86. (7) ­ G. BERTOLINI, P. CAPPELLANI, R. PANTECHI, G. RESTELLI: Nucl. Inst. and Meth. 2? (1964) 281 . ­ 6 ­tering tail associated to the electron peaks of different energies, to give a correct interpretation of the continuous beta spectra. The knowledge of the backscattering is obviously required also to make evaluations of internal conversion coefficients. In the study of radioactivity of U 232 (8) in the determination of Ζ conversion ratios for the 58 and 128 KeV transitions (fig. 2) it M has been observed that this ratio would be affected by an error of about 15$ for the 58 KeV conversion electrons and of the order of 5$ for the 128 KeV conversion electrons, if the backscattering is not taken into account. The error becomes much higher, of course, if the evaluation is made for peaks quite far in energy; as for instance for K/L ratios. GERMANIUM DETECTOR: In our laboratory at this moment, germanium detectors find their applications in activation analysis and in heavy elements studies. A problem treated in activation analysis was the determination of hafnium in hafnium depleted zirconium oxide; this is of interest due the importance of the problem in nuclear technology and also on account of the difficulty to perform a chemical separation between Hf and Zr. By a scintillation spectrometer, namely a Nai (Tl) 3" x χ 3" crystal, an evaluation is impossible for Hf content bäow 100 ppm (9)· Fig. 3 ­ 4 and 5 show gamma spectra taken by a Ge detector of pure Hf02, of natural zirconium containing 2$ of Hf and finally of a depleted sample with unknown Hf content. The determination can be performed using either the 130 KeV or the 480 KeV gamma line of Hf 131 ; a content of about 100 ppm has been obtained with good agreement between the values (93 and 103 ppm respectively) resulting from the two peaks. The estimated sensitivity of the method is 10 ppm. In heavy elements the presence of a certain number of gamma and ζΔ (8) ­ G. BERTOLINI, P. CAPPELLANI, G. RESTELLI, H.L. SCHERPP: Nuclear Physics to be published. (9) ­ Y. KAMEMOTO, S. ÏAMAGISHI: Nippon Kagaku Zasshi 84 (1963) 270. - ν -Xrays peaks of near energy inhibits a good determination of energies and relative intensities of the radiations. Fig. 6 shows a gamma spectrum from a source of Pu 240 of the following isotopie composition: Pu 239 : 2,96 % Pu 240 : 96,8 % Pu 241 : 0,2 $ Pu 242 : 0,03 $ From the spectrum the relative intensities of the gamma transi­tions with respect to the total alpha transitions have been determi­ned. Taille I shows the data obtained compared with those in ref. 10. The total conversion coefficients for the 45 and 104 KeV tran­sitions are reported together with the theoretical values calculated for E 2 transitions. The conversion coefficients for the 163 and 210 KeV gamma are not given due to the strong dependence on the alpha branching (11) and decay scheme assumed. T A B L E I GAMMA ! Gamma intensities ! _ „ „_ ! Total conversion coefficients Ref. 10 Energy ! $ of decay ! * ! experimental !(E2) theoretical 45 KeV ! 4,5 x 10~2 !3,6 χ 1Ò"2! 540 ! 613 104 KeV ! 7,1 x 10~3 !9,1 x 1Õ3! 11,8 ! 11,35 163 KeV ! 4,7­°,5x 10~4 !5,1 x 1Õ4! ! 210 KeV ! 4,2Í0,6x 10~4 !4,8 χ 1Õ4! ! X KL ! 5,3 x 1θ"4 ! ! ! X KM­N ! 1,43 x 10­3 ! ! ! Acknowledgments: The autors are indebted to R. BENOIT for designing the low noise preamplifiers, to the activation analysis group for the Hf determination and to A. OSTIDICH for preparation of Plutonium sources, (10) ­ J.E. CLINE: IDO 16695 (1961) 43 (11) ­ E.F'. TRET'YAKOV, L.N. KONDRAT'EV, G.I. KHLEBNIKOV and L.L. GOL'DIN, JETP 9 (1959) 250. I/I c O «10 8 -6-4 -2-0 U-NpXL I 50 "40 \ 100 Pu 240 + Am 2 41 y SPECTRUM S i - L i DRIFTED DETECTOR 3 0 0 m m z " 2.2 mm 77° K Am 241 59.6 KeV Pu 240 45KeV / \ o / \ 3.3 KeV f w h m 150 channel 200 Fig.1 V) c o υ 10-8-6 -4 --2-«10* BACKSC. J LEVEL β .JSJ Λ.. Ó 58 KeV *L «M 40 53.5 1 1 —' \ 50 χ102 / 100 128 KeV * L eM 110 123.5 KeV \ \ u 2 3 2 CONVERSION ELECTRONS Si - LITHIUM DRIFTED DETECTOR 50mm2»2mm 260°K / V 150 channel Fig.2 «10* W ) 1 2 H c S10-8-6-4 -2-0 Hf-181 133+136 KeV i « ^ \ -10 χ ^ u-I 50 Hf 02 Hf-181 346 KeV \ fl *~ΛΙ V too Hf-181 482KeV 1 150 200 250 3Ò0 channel 350 Fig.3 χ10' c Í4- I o 2-Hf-181 133+136 KeV ZrO- + 27.Hf Hf-181 346 Κ eV Hf-181 482 KeV 200 Fig.4 250 300channel ÍÍÕ xlO4 8 -in c -D O O 6 -4 -2-ír Î Hf-181 1133-136 KeV 1 50 p 302 : II "5 J a 233 Î12 340 KeV 1 Hf-181 346KeV 1 100 150 Ge- 250mm2 »2mm Zr + Hf 103ppm Hf-181 Nb-97 Zr-96 482 KeV 665KeV 723 756KeV J 1 π A ^ " \ Nb-97 Nb-95 \ 750 KeV 764KeV \ ñ¥ 200 250 300 channel Fig. 5 0- 10 c D O 8-6- q 2-45 KeV PU 240 GAMMA SPECTRUM 250mm2x2.5mm 77° K 104 KeV 163 KeV 210 KeV I 350 channel 400 Fig.6 mW To disseminate knowledge is to disseminate prosperity — I mean general prosperity and not individual riches — and with prosperity disappears the greater part of the evil which is our heritage from «Mil» Pi nmt', ml iiça mm :mm mMåk SALES OFFICES All Euratom reports are on sale at the offices listed below, at the prices given on the back of the cover (when ordering, specify clearly the EUR number and the title of the report, which are shown on the cover). m£j PRESSES ACADEMIQUES E U R O P E E N N E S 98, Chaussée de Charleroi, Bruxelles 6 Banque de la Société Générale - Bruxelles compte N° 964.558, Banque Belgo Congolaise - Bruxelles compte N° 2444.141, Compte chèque postal - Bruxelles - N° 167.37, Belgian American Bank and Trust Company - New compte No. 22.186, Lloyds Bank (Europe) Ltd. - 10 Moorgate, London E.C.2, Postcheckkonto - Köln - Nr. 160.861 h »iirtfr !''*5!tá*r¡W OFFICE CENTRAL D E V E N T E DES PUBLICATIONS DES COMMUNAUTES E U R O P E E N N E S 2. place de Metz, Luxembourg (Compte chèque postal N° 191-90) W il Ite:»» BELGIQUE — BELGIË MONITEUR BELGE 40-42, rue de Louvain - Bruxelles BELGISCH STAATSBLAD Leuvenseweg 40-42 - Brussel D E U T S C H L A N D BUNDESANZEIGER Postfach - Köln 1 U-'l 1 · ' mim G R A N D - D U C H E D E L U X E M B O U R G OFFICE CENTRAL DE VENTE DES PUBLICATIONS DES COMMUNAUTES EUROPEENNES 9, rue Goethe - Luxembourg F R A N C E SERVICE DE VENTE EN FRANCE DES PUBLICATIONS DES COMMUNAUTES EUROPEENNES 26, rue Desaix - Paris 15e É^îf l- ': i <"t , f ,MÏ'1 ' ' ' »»¡/M *: Mer is iä ii usi ITALIA LIBRERIA DELLO STATO Piazza G. Verdi, 10 - Roma 3 TiSÉ N E D E R L A N D STAATSDRUKKERIJ Christoffel Plantijnstraat - Den Haag t i i [wuMmn EURATOM — C.I.D. 51-53, rue Belliard Bruxelles (Be lg ique ) CDNA02580ENC mmm ¡HH 

Lithium Drifted Semiconductor Detectors in Nuclear Spectroscopy. EUR 2580.

Abstract

Similar works

Full text

Available Versions

Archive of European Integration

Archive of European Integration