Acceleration sources

Elastic recoil spectrometry (ERS) is used for the specific detection of hydrogen ( H, H) in surface layers of thickness up to approximately 1 pm, and the determination of the concentration profile for each species as a function of depth below the sample s surfece. When carefully used, the technique is nondestructive, absolute, fast, and independent of the host matrix and its chemical bonding structure. Although it requires an accelerator source of MeV helium ions, the instrumentation is simple and the data interpretation is straightforward. 

Figure 4.13. Schematic diagram of a tandem accelerator source of high energy alpha particles.

Laboratoire d Optique Appliquee, ENSTA, Summer school on ultrafast X-ray science with lasers and accelerator sources, Cargese, France, 2003 (see http //loa.ensta.fr/ufx/, last accessed 03 September 2006)... 

The development of high fluxes of low-energy neutrons from pulsed accelerator sources, such as IPNS at Argonne National Laboratory (USA), KEK (Japan) and, especially, ISIS at Rutherford Appleton Laboratory (UK) provides a most suitable probe for studies of the vibrational dynamics of hydrogenous materials. The advantages of neutron scattering for the study of molecular dynamics stem from their remarkable properties. 

Particle accelerator sources. Various particle accelerators are listed in a table modified from Spinks and Woods . Pulsed beams are out of context here, but... 

ESR is muon spin resonance (pSR), carried out at high-energy accelerator sources such as TRIUME (Vancouver, Canada) that provide muons. 

Spacecraft and rodcets provide platforms with longer durations of low effective acceleration. Sounding rockets can provide 5 to 15 minutes of low g. The Space Shuttle can provide up to 17 days and the International Space Station (ISS) can provide months of low g. Avera accderation levels on spacecraft in low earth orbit can be on the or of lO g. There ate two sources of acceleration that account for this. One is atmo hoic drag. The other acceleration effect is the so-called gravity gradient These acceleration sources will be discussed in the next sectioa... 

The ternary Am- Cm-Be source (the ABC source) may find increasing application, since it may be possible to prepare sources with outputs of up to 5 X10 ° s This type of source is produced by reactor irradiation of the conventional Am-Be source. Wing and Wahlgren have estimated the optimum sensitivities for 60 elements using an ABC source with a fast-neutron output of 5 X10 s S giving fluxes of 1.4x 10 ncm s" These authors used this source for the measurement of F, by the F(n,a) N reaction with a lower limit of detection of 0.4 mg of F. The precision of the method was good and the measurement rapid. The sensitivity compared favourably with methods using accelerator sources of neutrons. 

D.M. Mattox, R.E. Cuthrell, C.R. Peeples, PL. Dreike, Design and performance of a moveable-post-cathode magnetron sputtering system for making PBFAII accelerator sources. Surf. Coat. Technol. 33 (1987) 425. 

The electron accelerators can operate several ways. The acceleration requires a force provided by an electric field, which can be a continuous electrostatic potential (e.g.. Van de Graaff) or oscillation in time and space as produced by radio frequency, microwave or laser radiation (e.g.. Synchrotron, LINAC). Most of these methods use heated cathode to get the acceleration of electrons, usually from an electrostatically (about 10 keV) pre-accelerated source. These accelerators can provide from several hundred keV to several hundred MeV energy electrons (Synchrotron accelerators can produce electrons even with GeV energy). 

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