DE1803806C3 - Device for guiding a sub-thermal neutron beam and focusing device made of microneutron guides - Google Patents

Description

8 03 806

I. - Lungs of the straight neutron guide).

A curved neutron egg is also known with approximately the same dimensions, the radius of curvature being approximately 300 to 500. In the case of greater lengths of the neutron egg, this radius of curvature can also be 2000 m, for example. To prevent excessive heating and activation of the reflective coating, end; this already outside the high-flow area of the Reakior-C'ores. Copper coatings on the carrier material aluminum and nickel coatings on pilaster materials are known as materials for the new iron (Reactor Science and Technology, | ourual oil Nuclear Lnergy. Part A / B, Vo !. 17, I96J, pages 217 to 22'r, Nukleonik, volume 4.1962, pages 23 to 25).

A mefir channel collimator is also known Neutrons, which are made from niagnosed and polished pilaster sheets. With him there can be a · good one Neutron polarization can be achieved (journal of Nuclear Knergy, Part A and B, Reactor Science Technology, Vol. 17,!% J, pages 227 to 231). Hs only a little tweak noiw endig to these collimators to be used as a new iron filter. To do this, the The collimator consists of two parts and the walls are made of materials with ligaments that reflect neutrons well have, for example nickel plaitiene Steel sheets.

If the inner part is hinged so that the angle between the two parts can be optionally adjusted, the collimator can also be used as a neutron generator. Each sheet metal packet file is approx. 100 cm long and consists of about 5 to b layers with l.ul't gaps in between. In the first instance, however, it is doubtful whether this reflection collimator system produces just as high a cold neutron intensity as an oil crystal filter or a curved, tubular new iron conductor with reflecting walls.

The known new-iron conductors have the disadvantage that the neutron illuminance that can be achieved with them at the mouth of the new iron conductor is relatively low. It would be experimental work in any case more desirable, in addition to the advantage of being able to switch the Untergnindsiörsirahhmg and the In order to gain the freedom of movement of space, it is also possible to have high neutron illuminance levels available. In addition, the linear adjustment and maintenance of the radius of curvature is tedious or difficult.

Hs is therefore the task of the discovery. a Find new iron conductors with the highest possible illuminance, whose radius of curvature compared to the known executions klein isi und steis constant remains.

The solution to this task? provides according to the invention provides that the side facing the neutron beam sides of the boundary surfaces having a plurality of parallel, thick respectively uniform, alternating layers Λ and B are provided, wherein the thick on the order of a few micrometers layers \ .hin a duichlässigen for suhihci mix neutron Material in! a win Wei 1 little different Brechun.L'spKicv iiiul the ■■■■ de: (irößenordnuiig of some / ehutc microns iiickeu layers B consists of a the subthcrmischei:! Neuirorien reflective material, uiu i, ^i; the radius of curvature Limiting areas ii: ... order of magnitude from a few tenths of a mile to cinigei mire today (micro-neutron line).

The index of refraction for the neutrons in the different materials is determined according to D. j, 11 u g h e s

where N --- the Alomdichle of the material, <■) ,,, /, ~ mean the coherent scattering amplitude, λ = the neutron wavelength. Since the index of index / 7 is less than 1 in most substances, total reflection occurs at a critical angle

I 2 (1 - / i)

Since the refractive index depends on the neutron wavelength, the critical angle according to formula (2) also depends on it. The micronutrient according to the invention is preferably suitable for sub-thermal oiler cold neutrons with a wavelength of from b to 20 angstroms.

In an advantageous keep Auslührungslorm of erlin diingsgemäßeii micro neutron guide the for the subthermischen neutron permeable layers \ aluminum and do sublhermischen neutron reflective layers / ( 'made of nickel. The layers Λ this case have a thickness of about 1 micron, while the layers / They have a thickness of approximately 0.1 µm.

The microneedle rings of the type according to the invention have a liasis diameter d of 1 to 20 / entimes, while the radius of curvature is about 1 to 0.2 meters.

In addition, according to Tier Krl'indimg, the microneedle iron can be performed very easily and precisely produce. Such manufacturing processes have proven particularly successful:

a) tlas vacuum evaporation on a positive oiler Negative mold at a vacuum of 10 "l'orr using nuclear-pure vapor deposition materials,

b) the electrolv tables application of the individual layers on a positive or negative form in one gal \ anic bath,

c) the K; testicle dusting down to the respective layer materials in a gas vent at low pressure aiii a positive oiler negative form.

The korderung for high new iron Belei'chiuiigs strengths is according to the invention with a 1-focus device from microneutron guides in that described above Art achieved by the fact that several such microneedle tubes are curved in only one plane Boundary surfaces are assembled to form a hollow body, which has the l-'orm of a polygonal Kegelsiuinpies with convex inwardly curved On the other hand, befweisi. Line such Kokussierungseinrichf.ing can also be tlie l'orm of a spherical shell with the ball cap cut off.

The focusing device exists when using, in en, en; Mrahlenkan.i- mn circle; undem i.luei scliniü from cmc! Kugellu-.lhscn.'U ¹ um cut K iij'elkappe (KriMimiun; ', in K Grenzungsi ί, κ hen in.''Ac. 1 .lic η cn) where ι, -: ■': '' Si ι ahlenka'iai sow oh I a in the Re,!>. ! o! 'u and des I ,,; .c'iungsreiik'οι s ν '.irgeschenei Hesti, !! liüiiL's'k.iH.! ¹ ! , ils- ,. iJi cui in the Lmleiuuii. ' Beschi iebenc 'u'h.mnier neutrons before, of great length ν will be destroyed. In \ crbiniiung mn a Sirahl canal on the right. kiLier cross-section has the

Focusing device according to the invention the shape of a truncated cone with convex inwardly curved Sidewalls on. In the latter case, the boundary surfaces reflecting neutrons have a Curvature in only one plane.

Ocr base diameter (/ of a focusing device according to the type described in the invention is 1 cm to 20 cm. While the radius of curvature ρ of layers A and B is approximately 0.2 to 1 meter.

Expediently, the one used as the carrier material is used in the manufacture of the focusing device Positive form made from a salt, because this is then very much after the individual layers have been applied can easily be removed again. The same applies to a manufacturing method of the focusing device via a negative form. Production using a negative mold even has the advantage that it does not must be removed again.

In the following, the structure and mode of operation of the Microneutron conductor according to the invention using the example a focusing unit formed from it are explained in more detail:

The figure shows a longitudinal section through a focusing device circular cross-section.

For the cold neutrons arriving in the .Strahlenkanal I with the diameter ι / = 2 cm, there are the following two possibilities to pass the crlindungsgcmällc focusing device 2 and - / to get to the target 4u:

a) The neutrons in the axial area fly through the central cavity i of the focusing device 2 without any reflection and strike the focusing position 4 / 'des l'argcts 4, -j almost perpendicularly.
h) The neutrons in the area close to the wall experience at least one kellexion in the curved neutron-reflective layers II of the l'oku ^ sienmgseinrichning 2 and are thereby deflected towards i 1 nkussieningssielle 4Λ.

The number of kellcxions should be flour flour as '■> or ti. "Because with the number of rellexii> ne: i and the inevitably associated long flight in the neutron-conducting layer Λ the length and thus the wavelength ^ k ~ y neutron radiation is changed. the radius of curvature η of the curved layer Λ and barren I okussierungseinriehiting 2 is determined by the Basisdiirchmesser ι /, the Sirahlenkanaldurchmesser supposed to be which is equal, to the number of reflections, y according to the critical angle for total reflection, which is dependent isl of the wavelength of the neutron radiation, and according to the (Ίrolle tier focussing sial 4 / 'on the target An,

For the focusing device described in the exemplary embodiment, the thickness of the neutron-conducting layer Λ made of aluminum was 1 μm. the thickness of the neutron-reflecting layer δ made of nickel 0.1 (im. the radius of curvature <t of these layers Λ and H 10 cm, the arc length / of the outermost layer of the focusing device 2 cm, the critical angle y _IV ■ = 0.2 / Λ Ncutron wavelength.

With the described focusing micro-neutron guides According to the invention, besides the properties that generally characterize the neutron guide in particular, extremely high neutron flux densities of about 10 "n / cm-see and above achieve. In addition, it is easily possible with a microneedle-like type 90 'deflection de; even in the tightest of spaces; Netitronenstromes to achieve what the bishet known neutron conductors with a radius of curvature of 300 to 2000 m was simply impossible.

I lieizu 1 sheet / one minute

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Claims (8)

Patent claims: S. Equipment for guiding, in particular for redirecting, a subthermal neutron beam with boundary surfaces curved in at least one plane, the sides of which facing the neutron beam are provided with at least one layer that totally reflects the subthermal neutrons (neutron halo), characterized in that! the ropes of the boundary surfaces facing the neutron beam are provided with several parallel, equally thick, alternating layers A and B , with the `` layers '' of the order of magnitude of a few micrometers made of a material that is permeable to the subthermal neutrons a refractive index little different from the value 1 and the layers B of the order of magnitude of a few tenths of a micrometer from one of the sub-thermal ones. Neutron-reflecting material exist, and that the radius of curvature of the boundary surfaces is in the order of a few tenths of a meter to a few Mieres (Mikrciieuiroiieiileiier). 2. Mikruiieuironeiileiie: · according to claim! .Due to this characterized in that the layers Λ which are permeable to the subthermal neutrons are made of aluminum and the sub-thermal neutron reflective layers are made of nickel. 3. Microneedron guide according to claim 2, characterized in that the layers A permeable to the subhermal neutrons have a thickness of about 1 μm and the layers B reflecting the sub-thermal neutrons have a thickness of about 0.1 μm. 4. Microneutron guide according to claims I to j. characterized in that the one / one layers .- \ and B are produced by vacuum vapor deposition on the boundary surfaces. ). Microneutron guide according to claims 1 to 3, characterized in that the individual layers Λ and are produced by electrolytic application on the boundary surfaces. b. Microneutron guide according to Claims 1 to 3, characterized in that the one / one layers A and B are produced by cathode sputtering of the respective layer material. 7. Focusing device made of microneedron guides according to claims I to 5, characterized in that several such microneedle cells composed of a hollow body with boundary surfaces / 11 curved in only one plane are of the shape of a polygonal truncated cone with convex inwardly curved Since it has walls η. 8. Focusing device made of microneutron guides according to ilen claims I to .3, characterized in that this / u a hollow body are shaped, which has the shape of a Ktigel half-shell with a cut off spherical cap 4. Focusing device according to the claims 6 and 7, characterized in that the base diameter c / of the larynx about 1 cm to 20 cm and the radius of curvature i> der I lohlkörperw; <;:.:> entrusted to me up to 0.2 m. The invention relates to a device for routing, in particular / by rerouting, a sub-thermal Neutron beam with at least i "of a curved boundary surface, whose the neutron beam / Unwaid sides with at least one of the sub-thermal neutrons totally reflecting Layer provided and (neutron guide). Such new iron conductors are used as experimental aids in irradiation experiments outside of the Irradiation channel of the reactor ν ei turns. You serve the following purposes: a) separation of the disturbing background radiation, b) Separation of the sub-thermal from the thermal neutron beams with the possibility of one Beam focusing. c) intensification of the intensity of the neutron beam, if the effective space angle is the neutrons lotary lecturing new iron conductor is larger; than the geometric angle of the neutron guide. By means of neutron tubes of great length, it is possible to guide neutrons from the reactor core to any experimental menus and facilities / \\ which may be set up outside the reactor building. This has the following advantages: These are located outside the reactor building! .aboraloi leu and l.xpen mentierstänue become ini. Also achieved by an extremely low circumferential perturbation, especially if the neutron guide is slightly curved. so that the aii in straight flight:> the reactor C ore incoming neutrons are turned off, and when special \ bschirmschilde are provided which laboratories and ^[: Protect .xperimeniieremi u hiungeu before animal diffuse interference from the Reakiorgebäude. Furthermore, the possible number of exposure expenmenia can be increased because the neuti'onenleit '.' I 'tubes radiate out from the reactor core and with increasing distance from the reactor, Liehen provides ever larger spaces for the exponential facilities can be won. In addition, one end of curved neutron guide tubes can be brought into C \> re zones with the highest neutron flux, since fast neutrons cannot be carried away by them. Neutron guides are for the following low-energy versions Interesting for the reasons mentioned above: (a) Small-angle scattering experiments on ordinary or magnetic materials; (b) single-y-rays, examinations, especially Koin / iden / experimenie. In the case of a high-flow reactor, the latter require special attention to the principle of safety; (c) Capability spectroscopy with slow neutrons and a chopper; (d) Transmission experiments at very low energies. A neutron guide is known ("Nukleonik", Volume 4. 1. Heft. 1962. Pages 2J to 25), which consists of a straight, internally highly polished, copper-clad tube of cylindrical cross-section, the diameter of which is on the order of centimeters Long \ r. of the order of 20 to 10 meters, and that is evacuated. ^ "IeIl a straight, tubular neutron guide brings about an increase in intensity in the case of 'slow neutrons of G" = 4y - /' ii, where;. ·, The critical angle! for the total reflection at the inner Neiirunenleiier-Rolr «.md (for example i-> ■ H '■' for cold neutrons with a length of 10 Å) and Ω the effective solid angle with ίϊ - .to ^: .7. ^: is (o = inner radius of the neutron guide;