Scattering Chamber

The pressure in the scattering chamber should be below approximately 10 Pa (high vacuum). Lower pressures in the UHV range are usually not necessary, because PRDA is not surface-sensitive. 

Eor analysis of emitted particles, solid state surface barrier detectors (SBD) are used inside the scattering chamber to measure the number and energy of the reaction products. Stopper foils are used to prevent scattered projectiles from reaching the detector. Depth profiles can be obtained from the energy spectra, because reaction products emitted in deeper layers have less energy than reaction products emitted from the surface. The concentration in the corresponding layer can be determined from the intensity of reaction products with a certain energy. 

The nuclear reaction products are usually measured in a high-vacuum scattering chamber. At resonance NRA, where the beam energy is varied, at each energy the... 

Figure 5.6. Diagram of a low-energy, high-angle electron-impact spectrometer. (A) Electron gun (B) monochromator (180° spherical electrostatic energy selector) (C) electron optics (D) scattering chamber (E) analyzer (180° spherical electrostatic energy selector) (F) electron multiplier (G) amplifier and pulse discriminator (H) count-rate meter (I) multichannel scaler (J) X Y recorder (K) digital recorder. (After Kupperman et a/.<42))...

Studies of the interaction of chlorine trifluoride with deuterium or hydrogen atoms in a scattering chamber were accompanied by frequent flashes or explosions, within 3 h if the reactor had been vented, or after 8 h if it had not. 

When it reaches its full capability, TASCC will accelerate all ions between lithium and uranium to energies up to 50 MeV/u and 10 MeV/u, respectively, It will feed some major pieces of apparatus the Q3D magnetic spectrometer, the isotope separator, a growing array of gas and solid-state detectors housed in a 1.5 m diameter scattering chamber, and the 8ir" Y-ray spectrometer [AND 84], All are currently operational except the 8ir spectrometer, which is being built by a consortium of Canadian universities and AECL Chalk River, with completion scheduled for late 1986. It will comprise two subsystems i) a spin spectrometer of 72 bismuth germanate (BGO) detectors, and ii) an array of 20 Compton-suppressed hyperpure (HP) Ge detectors. 

Information from beam exposures of the sample can be obtained a number of ways. For surface adsorption probabilities greater than 0.03, the King and Wells method [16] can accurately be employed to determine initial adsorption probabilities of a gas species. In short, a King and Wells measurement monitors the partial pressure of the scattering chamber before, during, and after exposure of the sample to the beam flux. A typical reflectivity measurement can be seen in Fig. 2. 

Utilization of both ion and neutral beams for such studies has been reported. Toennies [150] has performed measurements on the inelastic collision cross section for transitions between specified rotational states using a molecular beam apparatus. T1F molecules in the state (J, M) were separated out of a beam traversing an electrostatic four-pole field by virtue of the second-order Stark effect, and were directed into a noble-gas-filled scattering chamber. Molecules which were scattered by less than were then collected in a second four-pole field, and were analyzed for their final rotational state. The beam originated in an effusive oven source and was chopped to obtain a velocity resolution Avjv of about 7 %. The velocity change due to the inelastic encounters was about 0.3 %. Transition probabilities were calculated using time-dependent perturbation theory and the straight-line trajectory approximation. The interaction potential was taken to be purely attractive ... 

Figure 3. Diagram of the standard PIXE scattering chamber.

For each reaction, the fluorescence from all bands of the BaX C-X system has been measured in order to estimate the relative total reactive cross sections electronic transition moments, the factor in the proportionality constant k in eqn (2) needed to relate different molecules, is obtained from the estimated radiative lifetimes of the C states. The are estimated using both the scattering chamber and... 

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