Electrostatic accelerator systems

Referring again to Figure 2.4, the slow positrons emitted from the boron were accelerated and focussed by the electrostatic lens system... 

The most attractive approach to reducing the specific impulse of electrostatic accelerators and thereby to maintain reasonable electrical power system requirements is to choose a propellant with a small charge to mass ratio. In direct contrast to electrothermal rockets, electrostatic rockets require propellants with large molecular weights for efficient operation. 

Neutron generator systems utilising electrostatic acceleration to induce a tritium-deuterium nuclear reaction and specially designed parts (including tubes) thereof. 

FIGURE 10 The first free-electron user facility was established at the University of California, Santa Barbara. This device operates in the far infrared and employs an electrostatic accelerator, as shown in the background. A magnetically focused system of electron-beam optics is used to transport the beam from the accelerator through the wiggler (in foreground) and back to the accelerator. (Photo courtesy of Luis Elia.)... 

To produce beams of extreme specifications, for example, very high-energy particles or heavy-ion beams, a chain of accelerators have to be used (see O Tables 50.2-50.4 and the Internet sources referred to there). Generally, the ions coming from the ion source are accelerated in the first step by an electrostatic accelerator and after a bunching system, preparing the DC beam for the acceleration in an RF-based structure, they are accelerated further by cyclic or linear accelerators. 

The ion beam is produced in the following way U atoms are evaporated from an oven at a temperature of typically 400 C, and are ionized and excited to the metastable 2 5 state by electron impact, when leaving the oven aperture. The electrons are emitted from a little ring-shaped tungsten wire cathode which is placed horizontally several millimeters above the oven exit. The cathode is held at ground potential, the oven at +200 V. The electrons are accelerated directly onto the oven aperture thus counterpropa-gating to the ions which are accelerated in the same electric field. The ions pass the cathode loop and are formed into a well-collimated beam by an electrostatic lens system. 

As discussed in the early sections it seems that there are very few effective ways to stabilize the transition state and electrostatic energy appears to be the most effective one. In fact, it is quite likely that any enzymatic reaction which is characterized by a significant rate acceleration (a large AAgf +p) will involve a complimentarity between the electrostatic potential of the enzyme-active site and the change in charges during the reaction (Ref. 10). This point may be examined by the reader in any system he likes to study. 

---