Neutron windows

Two important experimental facilities, the thermal column and the shielding facility (see Sections 3.1 and, 3.2j, require that a section approximately 6 by 6 ft be removed from.the east and west thermal-shield side plates. Two components are added to the thermal-shield design by.these facilities (1) the neutron window, and (2) the neutron-absorbing curtain. The locations of these components may be visualized by referring to Figs. 2.B and C. When the 6- by 6-ft hole is cut in the thermal shield, it becomes necessary to replace... 

The Neutron Window. The neutron window is a 3-in. sheet of lead placed between the permanent graphite and the thermal column to absorb gamma radiation but permit easy neutron passage. The lead sheet is mounted in a steel frame and pl aced in the approximately 6- by 6-ft hole in the outer thermal shield. 

Precaution Flamm. solid powd. mod. fire hazard as powd. or dust or when exposed to flame si. explosion hazard as dust incompat. with halocarbons reacts incandescently with fluorine and chlorine reacts with Li, P Hazardous Decomp. Prods. Heated to decomp, in air, emits very toxic fumes of BeO NFPA Health 3, Flammability 1, Reactivity 0 Uses Structural material in space technology moderator In nuclear reactors source of neutrons windows for x-ray tubes in gyroscopes, computer parts, inertial guidance systems additive in solid-propellant rocket fuels beryllium-copper alloys aircraft brakes neutron reflectors... 

Scandium is used as a neutron window or filter in nuclear reactors. Scandium compounds are used in high-intensity lamps. 

In order that the high-pressure neutron window be as thin as possible while maintaining the necessary mechanical strength, it is necessary that it remain cool. This is achieved by water cooling that keeps the window at room temperature even when the sample temperature reaches... 

Figure 35. Two sites, the window and the cation sites, in which benzene molecules may be present within Na+X. Sites have been identified by neutron diffraction studies. [Reproduced with permission A. N. Fitch, H. Jobic, and A. Renouprez, J. Chem. Soc. Chem. Commun. 284 (1984).]...

PAD (perturbed angular distribution) is a variation of PAC with nuclear excitation by a particle beam from an accelerator. QMS is quasielastic MdBbauer-spectroscopy, QNS is quasielastic neutron spectroscopy. For MOBbauer spectroscopy (MS), perturbed angular correlation (PAC), and /J-nuclear magnetic resonance (/3-NMR), the accessible SE jump frequencies are determined by the life time (rN) of the nuclear states involved in the spectroscopic process. Since NMR is a resonance method, the resonance frequency of the experiment sets the time window. With neutron scattering, the time window is determined by the possible energy resolution of the spectrometer as explained later. 

A top cross-sectional sketch of the fast neutron gauge is shown in Fig 14. The sample is sandwiched between the neutron source capsule and the window of a shielded thermal neutron detector. The actual assembly includes either a 5 curie plutonium-beryllium capsule or a 4 microgram 252 Cf capsule as the source of fast neutrons the neutron output for each source is about 107 neutrons/sec. The sample container... 

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