Collimated beam apparatus

Petri factor. The UV intensity or irradiance may be different over the surface area of the targets (pathogens) to be irradiated. The Petri factor (Pp is then defined as the ratio of the average of the UV intensity (or incident irradiance) over the area of the Petri dish to the UV intensity (or irradiance) at the center of the dish. It is used to correct the intensity (irradiance) reading at the center of the Petri dish to more accurately reflect the average UV intensity (incident fluence) over the surface area. A well-designed collimated beam apparatus should be able to deliver a Petri factor ranging from 0.9 to 0.95. 

When MS 2 is used as a bioassay, the data are organized by plotting the dose-response data on a graph of the log inactivation versus the UV dose (mJ/cm ). According to a report on ultraviolet disinfection released by the National Water Research Institute (NWRI), the data must fall in the area bounded by the following equations when using a collimated beam apparatus ... 

A relatively high He background is obviously inherent in all He-beam experiments. Even a highly collimated beam puts a continuous, heavy He load on the pumps evacuating the sample chamber. In the case of the apparatus shown in Fig. 2, the beam collimated to 0.2° (1.5 x 10 sr) supplies the sample chamber with about 1.5 x 10 He/sec (5.7 x 10" mbarl/s). In view of some... 

Another apparatus that is very useful in studies of the mechanism of catalytic surface reactions is shown in Fig. 17. This is used in a molecular-beam surface scattering experiment (22b) in which a well-collimated beam of the reactant gas or gas mixture is scattered from a crystal surface and the products that are desorbed after a single scattering at a given solid angle... 

The UV dose data from bench-scale collimated beam tests for UV disinfection was first reported by Qualls and Johnson (23). Their original apparatus consisted of low-pressure UV lamps housed in a cardboard box with a 5.08 cm diameter, 72 cm long tube extending from a cut-out hole in the middle of the lamp arc length (20). 

As one can see from the above, many factors can affect the results. These factors include apparatus setup, collimated beam column, UV lamp, intensity measurement, shutter type and operation, Petri dish specifications, sample volume and depth of the liquid, mixing condition, pathogen testing, and water quality (24). In order to obtain consistent results, the recommendations below should be followed. 

Fig. 6. Schematic diagram of a two-beam apparatus to study H2 formation on grains. Separate beams of H and D atoms are produced in an RF source, with about 70 to 85% dissociation of the feed H2 and D2 gases. The collimated, differentially pumped thermal-energy beams of H and D atoms are brought to the ultrahigh-vacuum scattering chamber, where they are adsorbed onto a grain sample (olivine, pyrolitic graphite, etc.). The HD and D2 produced on the surface are desorbed using temperature-programmed desorption (TPD) and are detected by the quadrupole mass selector (QMS) (Vidali et al, 1998).

Figure 9. View of the essential parts of the crossed beam apparatus using short-lived radioactive labeling and detection (23) Ay radioactive beam source By scrubber-furnace C, LN -cooled collimator D, shut-off plug Ey nozzle beam furnace and cryopump F, gate valve G, hodoscope H, LN -coohd beam trap 7, calibrated beam monitor /, silicon surface barrier detectors K, halogen crossed beam L, radioactive beam M, rotary feed-through used to close the source stopcock.

The high contrast of the spectrometer is achieved either by triple passing each FP or the whole tandem setup. It results theoretically in an elevation of the apparatus function of each interferometer to the cube, which strongly enhances the contrast defined as the ratio of the maximum transmission over its minimum value. In order to achieve this high contrast, the tandem sits in a highly collimated beam between spatial filters, which also allows the stray light at the entrance to be diminished and the bandwidth at the exit pinhole in front of a photomultiplier or an avalanche diode to be selected (Fig. 2). 

The details of the crossed-beam apparatus used in our experiment can be found in many earlier publications [17,18]. Briefly, the alkali dimer source consisted of a resistively heated molybdenum oven and nozzle assembly, with the temperatures of the nozzle and the oven being controlled independently by different heating elements. Sodium vapour carried by an inert gas, which was either He or Ne, expanded out of the 0.2 mm diameter nozzle to form a supersonic beam of Na/Na2/inert gas mixture. The Na2 concentration was about 5% molar fraction of the total sodium in the beam when He was used as carrier gas. The beam quality dropped severely when we seeded Na2 in Ne so the dimer intensity became much weaker. No substantial amount of trimers or larger clusters was detected under our experimental conditions. The Na2 beam was crossed at 90 by a neat oxygen supersonic beam in the main collision chamber under single collision conditions. The O2 source nozzle was heated to 473 K to prevent cluster formation. Both sources were doubly differentially pumped. The beams were skimmed and collimated to 2 FWHM in the collision chamber. Under these conditions, the collision energies for the reaction could be varied from 8 kcal/mol to 23 kcal/mol. 

In an atomic beam apparatus the components are symmetrically arranged about the collimating slit C with... 

In addition to point-focus apparatus there are scattering devices with an extremely elongated cross-section of the primary beam. Historically this geometry has been developed as a compromise between ideal collimation and insufficient scattering power. Their practical importance is decreasing as more powerful point-collimated sources become available. Kratky camera (Alexander [7], p. 107-110) and Rigaku-Denki camera (BaltA Vonk [22], p. 83) are the most frequent representatives of slit-focus devices. 

Since powerful X-ray sources and sophisticated beam shaping have generally become available, point-collimated setups for the study of X-ray scattering have lost their former handicap of low intensity. Today they benefit from their simple and versatile geometry. This section is devoted to an overview of modern apparatus -beginning with the source of X-radiation and ending with the detector and the data acquisition system. 

A heavy-ion microbeam provides a unique way to control the number of particles traversing individual cells and localization of dose within the cell. A collimated heavy-ion microbeam apparatus has been installed in a beam line from the AVF cyclotron to develop a novel cell surgery technique [127] (Fig. 34) (Table 5). 

The intensity of the He beam of the apparatus shown in Fig. 5 collimated to 0.4° full width at half maximum (FWHM) is typically 1010 singlets/sec (or 3 -1014 atoms/sec sr) and 1.5 -109 triplets/sec for beam energies of 66 to 350 meV and about 20% of this value at 16.5 meV (liquid-nitrogen-cooled nozzle). The triplet intensity can be increased at the expense of a poorer velocity resolution by a lower electron-acceleration voltage. 

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