Del Mar Ventures
4119 Twilight Ridge
San Diego, CA 92130
tel (858) 755-6727
fax (858) 755-6771
v/efax (858) 630-237
v/efax: (509) 752-0123
delmar@sciner.com
http://www.sciner.com/
http://www.femtosecondsystems.com/
Del Mar Ventures> Product List> Neutron Products Index>
Parabolic Concentrator for Neutrons
Del Mar Ventures manufactures short-focus concentrators of neutrons. Concentrators may be used in a wide variety of applications to increase local neutron fluence, increase sensitivity of detection and/or imaging and to reduce exposure times.
Examples of Applications:
High sensitive local NAA
High spatial resolution (for example, in neutron radiography of thin samples).
Neutron Therapy
Neutron Capture Therapy
Standard features of Parabolic Concentrator for
Thermal Neutrons
The focus size (FWHM) of the concentrator:
3.6 mm in the focal plane
6.9 mm along its axis.
The neutron intensity in the focus is up to 10 times more than in the primary beam.
The angle aperture of the device is about 53°.
Focusing techniques are widely used for the enhancement of neutron beam intensity. Focusing of thermal neutrons utilizes the Bragg reflection from crystals or multilayer structures. Different approaches to the design of a focusing device have been proposed and realized. As major efforts in this field were aimed at monochromatic focusing, the devices built have long focal distances (for example, in the range of 1.8 - 6m for the focusing single crystal diffractometer E6 at the Hahn-Meither Institute, Berlin, Germany) and a small angle divergence of the beam in the focal point.
In many applications the intensity enhancement is the primary aim and there is no need for monochromatic neutrons. For such applications one can use new type of neutron crystal concentrators with a short focal distance. Concentrator uses a unique technique developed first for X-ray radiation.
Design of the concentrator
The concentrator consists of an Al-support and a reflector made from highly oriented pyrographite (HOPG).
The parabolic shape of the reflector is attributed to the shape of the external surface of the support. The cross section in the xz-plane follows the equation z =R2 (1.2 £ R £ 3 cm). The wall thickness of the support is 2 mm. It's top is cut off to give access to the focus. There are flanges at both sides. The flange from the top side may serve for connecting with a position-sensitive neutron detector. The detector can move along the z-axis for the investigation of the spatial distribution of neutron intensity. An Al foil on the entrance flange protects the luminescent screen of the detector from light. A Cd shield covers the central part of the foil and screens the detector from the direct neutron beam, as well.
HOPG is placed on the external surface of the support by a special method up to a thickness of 4 mm. Aberrations of the design can be caused by non-negligible depth of reflection and HOPG mosaicity. Both effects must result in focus smearing and intensity reduction. The mosaic spread (FWHM) of HOPG used for the concentrator manufacture was determined by an X-ray method with the Cu Ka line. It amounts to (1.2 ± 0.1)° .
It should be noticed that such a concentrator is a polychromatic device. The concentrator described was optimized for thermal neutron (T =300K° ) and covers the wavelength range of about 1.2 Å - 2.6 Å (corresponding to the variation of the first derivative over the parabolic curve).
Position-sensitive neutron detector can be used for observation of the spatial distribution of the primary and concentrated beams with a resolution better than 0.05mm. It contains a luminescent screen, an image intensifier, a voltage supplier and an interface card for connecting with a computer. Detailed description of the neutron detector can be found here.
To discuss your customer requirements for neutron concentrators contact Del Mar Ventures:
Del Mar Ventures> Product List> Neutron Products Index>
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