This thesis deals with the measurement of the differential elastic scattering cross sections of the elements lead, mercury, tungsten, antimony, selenium and zinc for 14-MeV neutrons in the angular range from about 15˚ to 90˚. In the introduction in chapter 1 it is pointed out that a knowledge of these cross sections is important in connection with the so-called cloudy crystal ball model. In particular the scattering data for neutrons of intermediate energy (order of magnitude of 10 MeV) are a direct and sensitive test for the optical model, since the theory is directly applicable to the elastic scattering of neutrons of not too low energy. .... 

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Emilsson, Erik Örjan,

Göteborgs universitets publikationer - e-publicering och e-arkiv

Sweden and the European miracles : conquest, growth and voice : a survey of problems and theories /

Nauta, Hendrik

University of Groningen

   University of GroningenDifferential elastic scattering cross sections for 14-MeV neutronsNauta, HendrikIMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite fromit. Please check the document version below.Document VersionPublisher's PDF, also known as Version of recordPublication date:1957Link to publication in University of Groningen/UMCG research databaseCitation for published version (APA):Nauta, H. (1957). Differential elastic scattering cross sections for 14-MeV neutrons. 's-Gravenhage:Excelsior.CopyrightOther than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of theauthor(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).Take-down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons thenumber of authors shown on this cover page is limited to 10 maximum.Download date: 12-11-201972S U [ I M A R YTh i , s  t hes i . s  dea l s  w i t h  t he  measu renen t  o f  t he  d i f f e ren t i a le last ic  scat ter j .ng cross sect ions of  the e lements lead,  mercury,tungsten, anti.nony, seleniun and zinc for 14-MeV neutrons in theangular range from about 15o to 90".I n  t h e  i n t r o d u c t i o n  i n  c h a p t e r  I  i t  i s  p o i n t e d  o u t  t h a t  aknowledge of  these cross sect ions is  important  in  connect ion wi ththe so-cal led c loudy crysta l  bal l  modeI .  In  par t icu lar  the scat-ter ing data for  neutrons of  in termediate energy (order  of  magni-tude of  10 MeV) are a d i rect  and sensl t ive test  for  the opt ica lmode l ,  s i nce  the  theo ry  i s  d i rec t l y  app l i cab le  t o  t he  e las t i cscat ter Íng of  ncutrons of  not  too low energy.In  chap te r  2  a  c r i t i ca l  su rvey  o f  t he  me thods  fo r  measu r i ngthe above cross sect ions is  g iven.  From a d iscussion of  the ad-vantages and d isadvantages of  the d i f ferent  methods and geome-t r ies we concluded that  r ing-shaped scat terers and a smal l  spher-ica l ly-shaped detector  should be used for  the scat ter ing measure-nents wi th 14-MeV neutrons.  The absolute values of  the cross sec-t ions could be evaluated wi thout  a knowledge of  the neutron in-tensi ty  and the detector  sensi t iv i ty .  Wi th a v iew to the calcula-t ion of  the cross sect ions and the necessary correct ions,  torus-shaped scat terers were used.  The spher ica l  shape of  the detectorof fers the advantage that  the detector-sensi t iv i ty  is  non-di rec-t ional.A  desc r i p t i on  o f  t he  appa ra tus  i s  g i ven  i n  chap te r  3 .  TheT(d ,n )aHe  reac t i on  was  used  as  t he  neu t ron  sou rce .  The  angu la rd i s t r i bu t i on  o f  t he  ene rgy  and  the  an i so t ropy  were  ca l cu la tedfrom the k inet ics of  the react ion.  The e last ica l ly  scat tered neu-t rons were detected by way of  recoi l  protons,  or ig Ínat ing in  ano rgan i c  ( sphe r i ca l l y - shaped )  sc in t i l l a to r  (5  g , / I  t e rphenyL  i nxy lene) .  The sc int i l la t ion detector  was b iased in such a way thatinelast ica l ly  scat tered neutrons and gamma rays were not  detect-ed.  A proport ional  counter  f i l ted wi th borontr i f luor ide served asthe neutron noni tor-.  Chapter  4 deals r ry i th  the calculat ion of  the cross sect ions andthe  co r rec t i ons .  The  c ross  sec t i ons  we re  f i r s t  ca l cu la ted  w i thsome s impl i fy ing a.stions, caused by thly .  The fo l lowing enuation of the neutt ica l ly  scat tered nt i c  sca t te r i ng  o f  rdue to the f in i te  drec t i on  f o r  t he  f i rthe determinat i .on cuncerta inty .A d iscussion ofto a very pronouncelar  d is t r ibut ions oxima and miniura, whand larger  neutrond i s t r i bu t i ons  on l ythe  ene rgy  o f  t henuclear  s t ructure.  1are pract ica l ly  iderl a r  d i s t r i . bu t i ons  1roughly by s imple Ian opaque disk of t lo f  the angular  d is tmuch better agreenet ive d iscussion of  1t he  d i f f e ren t i a lr ts  lead,  mercury,:V neutrons in  ther Ín ted  ou t  t ha t  ain connect ion wi th: t icu lar  the scat-r  (order  of  magni-i t  for  the opt ica lLe  to  t he  e las t i cods for  measur ingrussion of  the ad-ethods and geome-and a small spher-catteri.ng measure-of  the cross sec-r f  the neutron i .n-ew to the calcula-) r rect ions,  torus-)e of  the detectorr i tJ  is  non-di rec-n  chap te r  3 .  Theurce.  The angularI  we re  ca l cu la tedlIy scattered neu-or i .g inat ing in  anc, / l  terpheny I  inln such a way thati  were not  detect-fluoride served as:ross sections andt  ca l cu la ted  w i th73some s impl i fy ing assumpt ions.  Subsequent ly  the necessary correc-t ions,  caused by these s impl i f icat ions,  were calculated separate-Iy .  The fo l lowing ef fects were considered:  1)  exponent ia l  a t te-nuation of the neutrons in the scatterer. 2) energy loss of elas-t ica l ly  scat tered neutrons in  the Iab.  system. 3)  mul t ip le e las-t i c  sca t te r i ng  o f  neu t rons  i n  t he  sca t te re r .  4 )  angu la r  sp readdue to the f in i te  d imensions of  scat terer  and detector .  The cor-rect ion for  the f i rs t  e f fect  is  the most  important  one,  whereasthe determinat ion of  the last  two ef fects is  inherent  wi th someuncertai.nty.A d iscussion of  the resul ts  is  g iven in chapter  5.  In  addi t ionto a very pronounced maximum in the forward d i rect ion,  the angu-Iar  d is t r ibut ions of  the e last ica l ly  scat tered neutrons show na-x ima and min ima,  which tend to smal ler  angles for  heavier  nucle iand larger  neutron energy.  In  a f i rs t  approximat ion the angulard is t r ibut ions only depend on the mass number of  the nucleus andthe  ene rgy  o f  t he  i nc iden t  neu t rons  and  no t  on  the  de ta i l s  o fnuclear  s t ructure.  The angular  d is t r ibut ions for  lead and mercuryare pract ica l ly  ident ica l .  The qual i ta t ive features of  the angu-Iar  d is t r ibut ions for  14-MeV neutrons could be reproduced onlyroughly by s imple Fraunhofer  d i f f ract ion of  neutron waves f roman opaque d isk of  the s ize of  the nucleus.  However,  a descr ipt ionof  the angular  d is t r ibut ions by means of  the opt ica l  model  g ivesmuch bet ter  agreement  between theory and exper i ,ment .  A qual i ta-t ive d j .scussion of  th Ís  model  is  g iven.

Differential elastic scattering cross sections for 14-MeV neutrons

ARTS repository - University of Groningen

   University of GroningenDifferential elastic scattering cross sections for 14-MeV neutronsNauta, HendrikIMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite fromit. Please check the document version below.Document VersionPublisher's PDF, also known as Version of recordPublication date:1957Link to publication in University of Groningen/UMCG research databaseCitation for published version (APA):Nauta, H. (1957). Differential elastic scattering cross sections for 14-MeV neutrons. Excelsior.CopyrightOther than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of theauthor(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).The publication may also be distributed here under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license.More information can be found on the University of Groningen website: https://www.rug.nl/library/open-access/self-archiving-pure/taverne-amendment.Take-down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons thenumber of authors shown on this cover page is limited to 10 maximum.Download date: 08-06-202272S U [ I M A R YTh i , s  t hes i . s  dea l s  w i t h  t he  measu renen t  o f  t he  d i f f e ren t i a le last ic  scat ter j .ng cross sect ions of  the e lements lead,  mercury,tungsten, anti.nony, seleniun and zinc for 14-MeV neutrons in theangular range from about 15o to 90".I n  t h e  i n t r o d u c t i o n  i n  c h a p t e r  I  i t  i s  p o i n t e d  o u t  t h a t  aknowledge of  these cross sect ions is  important  in  connect ion wi ththe so-cal led c loudy crysta l  bal l  modeI .  In  par t icu lar  the scat-ter ing data for  neutrons of  in termediate energy (order  of  magni-tude of  10 MeV) are a d i rect  and sensl t ive test  for  the opt ica lmode l ,  s i nce  the  theo ry  i s  d i rec t l y  app l i cab le  t o  t he  e las t i cscat ter Íng of  ncutrons of  not  too low energy.In  chap te r  2  a  c r i t i ca l  su rvey  o f  t he  me thods  fo r  measu r i ngthe above cross sect ions is  g iven.  From a d iscussion of  the ad-vantages and d isadvantages of  the d i f ferent  methods and geome-t r ies we concluded that  r ing-shaped scat terers and a smal l  spher-ica l ly-shaped detector  should be used for  the scat ter ing measure-nents wi th 14-MeV neutrons.  The absolute values of  the cross sec-t ions could be evaluated wi thout  a knowledge of  the neutron in-tensi ty  and the detector  sensi t iv i ty .  Wi th a v iew to the calcula-t ion of  the cross sect ions and the necessary correct ions,  torus-shaped scat terers were used.  The spher ica l  shape of  the detectorof fers the advantage that  the detector-sensi t iv i ty  is  non-di rec-t ional.A  desc r i p t i on  o f  t he  appa ra tus  i s  g i ven  i n  chap te r  3 .  TheT(d ,n )aHe  reac t i on  was  used  as  t he  neu t ron  sou rce .  The  angu la rd i s t r i bu t i on  o f  t he  ene rgy  and  the  an i so t ropy  were  ca l cu la tedfrom the k inet ics of  the react ion.  The e last ica l ly  scat tered neu-t rons were detected by way of  recoi l  protons,  or ig Ínat ing in  ano rgan i c  ( sphe r i ca l l y - shaped )  sc in t i l l a to r  (5  g , / I  t e rphenyL  i nxy lene) .  The sc int i l la t ion detector  was b iased in such a way thatinelast ica l ly  scat tered neutrons and gamma rays were not  detect-ed.  A proport ional  counter  f i l ted wi th borontr i f luor ide served asthe neutron noni tor-.  Chapter  4 deals r ry i th  the calculat ion of  the cross sect ions andthe  co r rec t i ons .  The  c ross  sec t i ons  we re  f i r s t  ca l cu la ted  w i thsome s impl i fy ing a.stions, caused by thly .  The fo l lowing enuation of the neutt ica l ly  scat tered nt i c  sca t te r i ng  o f  rdue to the f in i te  drec t i on  f o r  t he  f i rthe determinat i .on cuncerta inty .A d iscussion ofto a very pronouncelar  d is t r ibut ions oxima and miniura, whand larger  neutrond i s t r i bu t i ons  on l ythe  ene rgy  o f  t henuclear  s t ructure.  1are pract ica l ly  iderl a r  d i s t r i . bu t i ons  1roughly by s imple Ian opaque disk of t lo f  the angular  d is tmuch better agreenet ive d iscussion of  1t he  d i f f e ren t i a lr ts  lead,  mercury,:V neutrons in  ther Ín ted  ou t  t ha t  ain connect ion wi th: t icu lar  the scat-r  (order  of  magni-i t  for  the opt ica lLe  to  t he  e las t i cods for  measur ingrussion of  the ad-ethods and geome-and a small spher-catteri.ng measure-of  the cross sec-r f  the neutron i .n-ew to the calcula-) r rect ions,  torus-)e of  the detectorr i tJ  is  non-di rec-n  chap te r  3 .  Theurce.  The angularI  we re  ca l cu la tedlIy scattered neu-or i .g inat ing in  anc, / l  terpheny I  inln such a way thati  were not  detect-fluoride served as:ross sections andt  ca l cu la ted  w i th73some s impl i fy ing assumpt ions.  Subsequent ly  the necessary correc-t ions,  caused by these s impl i f icat ions,  were calculated separate-Iy .  The fo l lowing ef fects were considered:  1)  exponent ia l  a t te-nuation of the neutrons in the scatterer. 2) energy loss of elas-t ica l ly  scat tered neutrons in  the Iab.  system. 3)  mul t ip le e las-t i c  sca t te r i ng  o f  neu t rons  i n  t he  sca t te re r .  4 )  angu la r  sp readdue to the f in i te  d imensions of  scat terer  and detector .  The cor-rect ion for  the f i rs t  e f fect  is  the most  important  one,  whereasthe determinat ion of  the last  two ef fects is  inherent  wi th someuncertai.nty.A d iscussion of  the resul ts  is  g iven in chapter  5.  In  addi t ionto a very pronounced maximum in the forward d i rect ion,  the angu-Iar  d is t r ibut ions of  the e last ica l ly  scat tered neutrons show na-x ima and min ima,  which tend to smal ler  angles for  heavier  nucle iand larger  neutron energy.  In  a f i rs t  approximat ion the angulard is t r ibut ions only depend on the mass number of  the nucleus andthe  ene rgy  o f  t he  i nc iden t  neu t rons  and  no t  on  the  de ta i l s  o fnuclear  s t ructure.  The angular  d is t r ibut ions for  lead and mercuryare pract ica l ly  ident ica l .  The qual i ta t ive features of  the angu-Iar  d is t r ibut ions for  14-MeV neutrons could be reproduced onlyroughly by s imple Fraunhofer  d i f f ract ion of  neutron waves f roman opaque d isk of  the s ize of  the nucleus.  However,  a descr ipt ionof  the angular  d is t r ibut ions by means of  the opt ica l  model  g ivesmuch bet ter  agreement  between theory and exper i ,ment .  A qual i ta-t ive d j .scussion of  th Ís  model  is  g iven.

English

Nauta, Hendrik,

University of Groningen Digital Archive

University of Groningen Research Database

  
 University of Groningen
Differential elastic scattering cross sections for 14-MeV neutrons
Nauta, Hendrik
IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite from
it. Please check the document version below.
Document Version
Publisher's PDF, also known as Version of record
Publication date:
1957
Link to publication in University of Groningen/UMCG research database
Citation for published version (APA):
Nauta, H. (1957). Differential elastic scattering cross sections for 14-MeV neutrons 's-Gravenhage:
Excelsior
Copyright
Other than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of the
author(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).
Take-down policy
If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately
and investigate your claim.
Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the
number of authors shown on this cover page is limited to 10 maximum.
Download date: 11-02-2018
72
S U [ I M A R Y
Th i , s  t hes i . s  dea l s  w i t h  t he  measu renen t  o f  t he  d i f f e ren t i a l
e last ic  scat ter j .ng cross sect ions of  the e lements lead,  mercury,
tungsten, anti.nony, seleniun and zinc for 14-MeV neutrons in the
angular range from about 15o to 90".
I n  t h e  i n t r o d u c t i o n  i n  c h a p t e r  I  i t  i s  p o i n t e d  o u t  t h a t  a
knowledge of  these cross sect ions is  important  in  connect ion wi th
the so-cal led c loudy crysta l  bal l  modeI .  In  par t icu lar  the scat-
ter ing data for  neutrons of  in termediate energy (order  of  magni-
tude of  10 MeV) are a d i rect  and sensl t ive test  for  the opt ica l
mode l ,  s i nce  the  theo ry  i s  d i rec t l y  app l i cab le  t o  t he  e las t i c
scat ter Íng of  ncutrons of  not  too low energy.
In  chap te r  2  a  c r i t i ca l  su rvey  o f  t he  me thods  fo r  measu r i ng
the above cross sect ions is  g iven.  From a d iscussion of  the ad-
vantages and d isadvantages of  the d i f ferent  methods and geome-
t r ies we concluded that  r ing-shaped scat terers and a smal l  spher-
ica l ly-shaped detector  should be used for  the scat ter ing measure-
nents wi th 14-MeV neutrons.  The absolute values of  the cross sec-
t ions could be evaluated wi thout  a knowledge of  the neutron in-
tensi ty  and the detector  sensi t iv i ty .  Wi th a v iew to the calcula-
t ion of  the cross sect ions and the necessary correct ions,  torus-
shaped scat terers were used.  The spher ica l  shape of  the detector
of fers the advantage that  the detector-sensi t iv i ty  is  non-di rec-
t ional.
A  desc r i p t i on  o f  t he  appa ra tus  i s  g i ven  i n  chap te r  3 .  The
T(d ,n )aHe  reac t i on  was  used  as  t he  neu t ron  sou rce .  The  angu la r
d i s t r i bu t i on  o f  t he  ene rgy  and  the  an i so t ropy  were  ca l cu la ted
from the k inet ics of  the react ion.  The e last ica l ly  scat tered neu-
t rons were detected by way of  recoi l  protons,  or ig Ínat ing in  an
o rgan i c  ( sphe r i ca l l y - shaped )  sc in t i l l a to r  (5  g , / I  t e rphenyL  i n
xy lene) .  The sc int i l la t ion detector  was b iased in such a way that
inelast ica l ly  scat tered neutrons and gamma rays were not  detect-
ed.  A proport ional  counter  f i l ted wi th borontr i f luor ide served as
the neutron noni tor-
.  
Chapter  4 deals r ry i th  the calculat ion of  the cross sect ions and
the  co r rec t i ons .  The  c ross  sec t i ons  we re  f i r s t  ca l cu la ted  w i th
some s impl i fy ing a.s
tions, caused by th
ly .  The fo l lowing e
nuation of the neut
t ica l ly  scat tered n
t i c  sca t te r i ng  o f  r
due to the f in i te  d
rec t i on  f o r  t he  f i r
the determinat i .on c
uncerta inty .
A d iscussion of
to a very pronounce
lar  d is t r ibut ions o
xima and miniura, wh
and larger  neutron
d i s t r i bu t i ons  on l y
the  ene rgy  o f  t he
nuclear  s t ructure.  1
are pract ica l ly  ider
l a r  d i s t r i . bu t i ons  1
roughly by s imple I
an opaque disk of t l
o f  the angular  d is t
much better agreene
t ive d iscussion of  1
t he  d i f f e ren t i a l
r ts  lead,  mercury,
:V neutrons in  the
r Ín ted  ou t  t ha t  a
in connect ion wi th
: t icu lar  the scat-
r  (order  of  magni-
i t  for  the opt ica l
Le  to  t he  e las t i c
ods for  measur ing
russion of  the ad-
ethods and geome-
and a small spher-
catteri.ng measure-
of  the cross sec-
r f  the neutron i .n-
ew to the calcula-
) r rect ions,  torus-
)e of  the detector
r i tJ  is  non-di rec-
n  chap te r  3 .  The
urce.  The angular
I  we re  ca l cu la ted
lIy scattered neu-
or i .g inat ing in  an
c, / l  terpheny I  in
ln such a way that
i  were not  detect-
fluoride served as
:ross sections and
t  ca l cu la ted  w i th
73
some s impl i fy ing assumpt ions.  Subsequent ly  the necessary correc-
t ions,  caused by these s impl i f icat ions,  were calculated separate-
Iy .  The fo l lowing ef fects were considered:  1)  exponent ia l  a t te-
nuation of the neutrons in the scatterer. 2) energy loss of elas-
t ica l ly  scat tered neutrons in  the Iab.  system. 3)  mul t ip le e las-
t i c  sca t te r i ng  o f  neu t rons  i n  t he  sca t te re r .  4 )  angu la r  sp read
due to the f in i te  d imensions of  scat terer  and detector .  The cor-
rect ion for  the f i rs t  e f fect  is  the most  important  one,  whereas
the determinat ion of  the last  two ef fects is  inherent  wi th some
uncertai.nty.
A d iscussion of  the resul ts  is  g iven in chapter  5.  In  addi t ion
to a very pronounced maximum in the forward d i rect ion,  the angu-
Iar  d is t r ibut ions of  the e last ica l ly  scat tered neutrons show na-
x ima and min ima,  which tend to smal ler  angles for  heavier  nucle i
and larger  neutron energy.  In  a f i rs t  approximat ion the angular
d is t r ibut ions only depend on the mass number of  the nucleus and
the  ene rgy  o f  t he  i nc iden t  neu t rons  and  no t  on  the  de ta i l s  o f
nuclear  s t ructure.  The angular  d is t r ibut ions for  lead and mercury
are pract ica l ly  ident ica l .  The qual i ta t ive features of  the angu-
Iar  d is t r ibut ions for  14-MeV neutrons could be reproduced only
roughly by s imple Fraunhofer  d i f f ract ion of  neutron waves f rom
an opaque d isk of  the s ize of  the nucleus.  However,  a descr ipt ion
of  the angular  d is t r ibut ions by means of  the opt ica l  model  g ives
much bet ter  agreement  between theory and exper i ,ment .  A qual i ta-
t ive d j .scussion of  th Ís  model  is  g iven.


   University of GroningenDifferential elastic scattering cross sections for 14-MeV neutronsNauta, HendrikIMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite fromit. Please check the document version below.Document VersionPublisher's PDF, also known as Version of recordPublication date:1957Link to publication in University of Groningen/UMCG research databaseCitation for published version (APA):Nauta, H. (1957). Differential elastic scattering cross sections for 14-MeV neutrons. Excelsior.CopyrightOther than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of theauthor(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons).The publication may also be distributed here under the terms of Article 25fa of the Dutch Copyright Act, indicated by the “Taverne” license.More information can be found on the University of Groningen website: https://www.rug.nl/library/open-access/self-archiving-pure/taverne-amendment.Take-down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons thenumber of authors shown on this cover page is limited to 10 maximum.Download date: 30-10-202372S U [ I M A R YTh i , s  t hes i . s  dea l s  w i t h  t he  measu renen t  o f  t he  d i f f e ren t i a le last ic  scat ter j .ng cross sect ions of  the e lements lead,  mercury,tungsten, anti.nony, seleniun and zinc for 14-MeV neutrons in theangular range from about 15o to 90".I n  t h e  i n t r o d u c t i o n  i n  c h a p t e r  I  i t  i s  p o i n t e d  o u t  t h a t  aknowledge of  these cross sect ions is  important  in  connect ion wi ththe so-cal led c loudy crysta l  bal l  modeI .  In  par t icu lar  the scat-ter ing data for  neutrons of  in termediate energy (order  of  magni-tude of  10 MeV) are a d i rect  and sensl t ive test  for  the opt ica lmode l ,  s i nce  the  theo ry  i s  d i rec t l y  app l i cab le  t o  t he  e las t i cscat ter Íng of  ncutrons of  not  too low energy.In  chap te r  2  a  c r i t i ca l  su rvey  o f  t he  me thods  fo r  measu r i ngthe above cross sect ions is  g iven.  From a d iscussion of  the ad-vantages and d isadvantages of  the d i f ferent  methods and geome-t r ies we concluded that  r ing-shaped scat terers and a smal l  spher-ica l ly-shaped detector  should be used for  the scat ter ing measure-nents wi th 14-MeV neutrons.  The absolute values of  the cross sec-t ions could be evaluated wi thout  a knowledge of  the neutron in-tensi ty  and the detector  sensi t iv i ty .  Wi th a v iew to the calcula-t ion of  the cross sect ions and the necessary correct ions,  torus-shaped scat terers were used.  The spher ica l  shape of  the detectorof fers the advantage that  the detector-sensi t iv i ty  is  non-di rec-t ional.A  desc r i p t i on  o f  t he  appa ra tus  i s  g i ven  i n  chap te r  3 .  TheT(d ,n )aHe  reac t i on  was  used  as  t he  neu t ron  sou rce .  The  angu la rd i s t r i bu t i on  o f  t he  ene rgy  and  the  an i so t ropy  were  ca l cu la tedfrom the k inet ics of  the react ion.  The e last ica l ly  scat tered neu-t rons were detected by way of  recoi l  protons,  or ig Ínat ing in  ano rgan i c  ( sphe r i ca l l y - shaped )  sc in t i l l a to r  (5  g , / I  t e rphenyL  i nxy lene) .  The sc int i l la t ion detector  was b iased in such a way thatinelast ica l ly  scat tered neutrons and gamma rays were not  detect-ed.  A proport ional  counter  f i l ted wi th borontr i f luor ide served asthe neutron noni tor-.  Chapter  4 deals r ry i th  the calculat ion of  the cross sect ions andthe  co r rec t i ons .  The  c ross  sec t i ons  we re  f i r s t  ca l cu la ted  w i thsome s impl i fy ing a.stions, caused by thly .  The fo l lowing enuation of the neutt ica l ly  scat tered nt i c  sca t te r i ng  o f  rdue to the f in i te  drec t i on  f o r  t he  f i rthe determinat i .on cuncerta inty .A d iscussion ofto a very pronouncelar  d is t r ibut ions oxima and miniura, whand larger  neutrond i s t r i bu t i ons  on l ythe  ene rgy  o f  t henuclear  s t ructure.  1are pract ica l ly  iderl a r  d i s t r i . bu t i ons  1roughly by s imple Ian opaque disk of t lo f  the angular  d is tmuch better agreenet ive d iscussion of  1t he  d i f f e ren t i a lr ts  lead,  mercury,:V neutrons in  ther Ín ted  ou t  t ha t  ain connect ion wi th: t icu lar  the scat-r  (order  of  magni-i t  for  the opt ica lLe  to  t he  e las t i cods for  measur ingrussion of  the ad-ethods and geome-and a small spher-catteri.ng measure-of  the cross sec-r f  the neutron i .n-ew to the calcula-) r rect ions,  torus-)e of  the detectorr i tJ  is  non-di rec-n  chap te r  3 .  Theurce.  The angularI  we re  ca l cu la tedlIy scattered neu-or i .g inat ing in  anc, / l  terpheny I  inln such a way thati  were not  detect-fluoride served as:ross sections andt  ca l cu la ted  w i th73some s impl i fy ing assumpt ions.  Subsequent ly  the necessary correc-t ions,  caused by these s impl i f icat ions,  were calculated separate-Iy .  The fo l lowing ef fects were considered:  1)  exponent ia l  a t te-nuation of the neutrons in the scatterer. 2) energy loss of elas-t ica l ly  scat tered neutrons in  the Iab.  system. 3)  mul t ip le e las-t i c  sca t te r i ng  o f  neu t rons  i n  t he  sca t te re r .  4 )  angu la r  sp readdue to the f in i te  d imensions of  scat terer  and detector .  The cor-rect ion for  the f i rs t  e f fect  is  the most  important  one,  whereasthe determinat ion of  the last  two ef fects is  inherent  wi th someuncertai.nty.A d iscussion of  the resul ts  is  g iven in chapter  5.  In  addi t ionto a very pronounced maximum in the forward d i rect ion,  the angu-Iar  d is t r ibut ions of  the e last ica l ly  scat tered neutrons show na-x ima and min ima,  which tend to smal ler  angles for  heavier  nucle iand larger  neutron energy.  In  a f i rs t  approximat ion the angulard is t r ibut ions only depend on the mass number of  the nucleus andthe  ene rgy  o f  t he  i nc iden t  neu t rons  and  no t  on  the  de ta i l s  o fnuclear  s t ructure.  The angular  d is t r ibut ions for  lead and mercuryare pract ica l ly  ident ica l .  The qual i ta t ive features of  the angu-Iar  d is t r ibut ions for  14-MeV neutrons could be reproduced onlyroughly by s imple Fraunhofer  d i f f ract ion of  neutron waves f roman opaque d isk of  the s ize of  the nucleus.  However,  a descr ipt ionof  the angular  d is t r ibut ions by means of  the opt ica l  model  g ivesmuch bet ter  agreement  between theory and exper i ,ment .  A qual i ta-t ive d j .scussion of  th Ís  model  is  g iven.

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Sweden and the European miracles : conquest, growth and voice : a survey of problems and theories /

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