Detection, solid angle

In ERD, from the consideration of various characteristics, e.g. maximum accessible depth, depth and mass resolution, detection sensitivity, etc, none of the experimental parameters, such as Mi, Eo, a,(3,0 beam spot-size, and the detection solid angle Q can be optimized without affecting the other. In our system, based on our needs as well as other anticipated applications, the overall choice of the ERD parameters are 30 MeV 35ci as the probing beam with 0 = 30°, a = (3 =... 

Fig. 1 Electrode configuration of the endcap trap. The open structure offers a large detection solid angle and good access for laser beams testing the micromotion of the ion. Micromotion is minimized by applying dc voltages Ui, U2, Uu, Ud.

The calibration of a PIXE system, i.e., the determination of sensitivity factors, which assign absolute concentration data to numbers of counts in X-ray peaks, can be performed in two different ways. First, sensitivity factors can be deduced theoretically or in a semiempirical way from calculated cross sections for X-ray excitation and from X-ray absorption data for the absorbents present between the points of emission and detection, in the actual experimental setup. Second, sensitivity factors can be deduced from measurements performed on standard samples consisting of pure elements or pure chemical compounds. The detection solid angle and the energy-dependent detector efficiency should also be determined. 

In TOF-SARS [9], a low-keV, monoenergetic, mass-selected, pulsed noble gas ion beam is focused onto a sample surface. The velocity distributions of scattered and recoiled particles are measured by standard TOF methods. A chaimel electron multiplier is used to detect fast (>800 eV) neutrals and ions. This type of detector has a small acceptance solid angle. A fixed angle is used between the pulsed ion beam and detector directions with respect to the sample as shown in figure Bl.23.4. The sample has to be rotated to measure ion scattering... 

TOF detector systems usually have smaller solid angles and sensitivity than AF - E systems, because of the long TOF system in front of the energy detector and the limited size of the stop detector. They also have worse detection limits for very light elements (hydrogen), because of the low probability of obtaining start and stop signals for particles of very low atomic number [3.172]. 

The factor (q/a ) may be obtained from independent optical and geometrical measurements, since q is the transmittance of the attenuator used for the incident beam, a is the solid angle of detection of scattered light and is the thickness of sample. 

Suppose your experiment failed to detect a type of decay you were seeking What can you say about its occurrence The simplest answer is what is termed the one-event upper limit. You assume that you had detected one event, and calculate the resulting decay rate, cross section, and the like, taking into account detection efficiencies, solid angles, and so forth. 

Of course, we still have to detect the gammas and to include the solid angle of the detectors. If we have a detector of area Ad and efficiency e at a distance rd from the material in the target, we obtain the number counted... 

Another important parameter is the yield. The yield of particles detected by a solid state de-tector subtending a small solid angle, Q, (typically Q < 10 sr) is given by ... 

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