Electron accelerator facility

Table 2. Comparison between time-resolved spectrophotometric detection set-ups of several laser-photocathode electron accelerator facilities for picosecond pulse radiolysis. 

Pulse-probe studies using the Laser Electron Accelerator Facility (LEAF) at Brookhaven National Laboratory have revealed changes in optical absorption occurring on the picosecond time scale in rare gas fluids. In xenon, excimers are formed which absorb in the visible and near infra-red as shown in Fig. la. The absorption grows in during the first 50 picoseconds [see Fig. 1(b)].This growth is concomitant with ion recombination that leads first to excited atoms, reaction 1(a), which immediately form excimers, Xe, because of the high density of xenon. 

James R Wishart received a B.S. in Chemistry from the Massachusetts Institute of Technology in 1979 and a Ph.D. in Inorganic Chemistry from Stanford University in 1985 under the direction of Prof Henry Taube. After a postdoctoral appointment at Rutgers University, in 1987 he joined the Brookhaven National Laboratory Chemistry Department as a Staff Scientist in the Radiation Chemistry Group. He founded and presently supervises the BNL Laser-Electron Accelerator Facility for picosecond electron pulse radiolysis. His research interests include ionic liquids, radiation chemistry, electron transfer, and new technology and techniques for pulse radiolysis. He has authored over 90 papers and chapters, and is the co-editor of Advances in Chemistry Series o. 254, Photoehemistry and Radiation Chemistry. 

Figure 1 Schematic representation of the Laser-Electron Accelerator Facility at Brookhaven National Laboratory. The laser beam is split to generate both the electron pulse and the probe light (scheme courtesy of Dr. J. Wishart, Brookhaven National Laboratory).

To exploit the capabilities of fast lasers, a new picosecond Laser-Electron Accelerator Facility (LEAF) has been recently developed at Brookhaven National Laboratory. In this facility, schematically shown in Figure 1, laser light impinging on a photocathode inside a resonant cavity gun merely 30 cm in length produces the electron pulse. The emitted electrons are accelerated to energies of 9.2 MeV within that gun by a 15 MW pulse of RF power from a 2.9 GHz klystron. The laser pulse is synchronized with the RF power to produce the electron pulse near the peak field gradient (about 1 MeV/cm). Thus the pulse length and intensity are a function of the laser pulse properties, and electron... 

As mentioned above, a 3.5-cell RF photocathode gun is in operation as the accelerator for the Brookhaven National Laboratory Laser-Electron Accelerator Facility. Recently, 1.6-cell RF photocathode guns have replaced thermionic cathode systems as injectors for 30 MeV linear accelerators at Osaka University and the Nuclear Engineering Research Laboratory in Tokai-mura, Japan [6]. Another RF photocathode gun accelerator is under construction at the ELYSE facility at the Universite de Paris-Sud at Orsay, France. A magnesium cathode is in use at LEAF, copper is used at NERL, while the Orsay accelerator will use Cs Te. 

Brookhaven National Laboratory s Laser Electron Accelerator Facility (LEAF) uses a titanium-sapphire laser Ahv = 798 nm fwhm = 100 fs and energy per pulse is 0.01 J. 

This laser is a component of Brookhaven National Laboratory s Laser Electron Accelerator Facility (LEAF). 

The facility costs are based on the concept of a mobile remote repair facility. The advantages of this concept are low-cost, minimal shielding requirements, and flexible use of the overall repair facility. The main components for a remote repair are the electron accelerator, the power supply, and the robotic control system including the remote video system. Table 14 shows the estimated costs for these main components. 

Laser-plasma accelerators represent a unique tool for investigating matter properties at a reduced laboratory scale, compared to large-scale facilities. Nowadays, efficient electron acceleration can be provided by such table-top accelerators and can be used to perform experiments in a variety of fields. 

Soviet Union, where an electron irradiation plant to treat imported grains went into operation in 1980 at Port Odessa and some 400,000 tonnes/year of grain were successfully treated by two electron accelerators. This facility is not currently in use in the Ukraine, after the collapse of the Soviet Union. 

An optimum processing time of 180 min is required for a complete cycle of 100 kGy dose. A shutdown time of at least 8 h was necessary after every 100 kGy addition to allow sufficient diffusion of oxygen in the PTFE powder. The total time for the whole process from 20 to 500 kGy was approximately 50 h, including the 8 h shutdown intervals after every 100 kGy addition. To achieve 500 kGy, the doses were added to the PTFE powder in 100 kGy steps. These treatment parameters were chosen in order to avoid excess temperature rise, which might favor deactivation of the radical formation, as well as to control agglomerate size and chemical structure via absorbed dose. Further information on the electron accelerator (ELV-2) facility can be found in [11]. 

The nuclear industry makes available about 3000 nuclides, including both the stable and the radioactive nuclides. Approximately 50 radioactive nuclides, along with some stable nuclides that have been isotopically enriched, are essential in research, medical, and industrial applications. Many of these are now produced commercially, but several still are dependent on government facilities. Some, for economic reasons, come from other countries. Radiation processing for sterilization of disposable medical supplies is an important operation using cobalt-60 from Canada. Electron accelerators have replaced... 

In comparison with other laboratories techniques in polymer chemistry, radiochemical synthesis seems to be a large-scaled experiment, expensive, and exotic. But this is only partially true. There exist industrial facilities like electron accelerators and... 

Fig. 6. Scheme of the laser-driven RF electron accelerator of pulse radiolysis facility ELYSE. IP ion vacuum pump, CPC cathode preparation chamber, W vacuum valve, SOL solenoid, D dipole, TRl and 2 triplets, Q quadrupole, WCM wall current monitor, PC Faraday cup, T translator for Cerenkov light emitter and visualization screen LME laser entrance mirror, LMEx laser exit mirror, VC virtual cathode FIS horizontal slit, VS vertical slit. (Reproduced with permission from Ref 28.)... 

Radiation processing plays an important role in industry, health care, agriculture and environmental technology. It involves the use of large radionuclide (gamma-radiation) sources and electron accelerators in industrial and institutional facilities. Quality assurance is vital for the success of this technology. In fact, it is indispensable for... 

Photocathode-based picosecond electron accelerators are conceptually simpler than pre-bunched thermionic systems, although they require reasonably powerful, multicomponent femtosecond or picosecond laser systems to drive the photocathode. In addition, the availability of synchronized laser pulses allows the development of advanced detection capabilities with unprecedented time resolution. The combination of ease of use and powerful detection methods has stimulated strong interest in photocathode gun systems. Since the installation ofthe first photocathode electron gun pulse radiolysis system at BNL [5,13], four additional photocathode-based facilities have become operational and two more are in progress. The operational centers include the ELYSE facility at the Universite de Paris-Sud XI in Orsay, France [7,8], NERL in Tokai-Mura, Japan [9,10], Osaka University [11,12], and Waseda University in Tokyo [13]. Facilities under development are located at the Technical University of Delft, the Netherlands, and the BARC in Mumbai, India. 

Irradiation Facility Radio-active source Electron accelerator... 

Radiation cross-linking affects different characteristics of polymers like mechanical behaviour, chemical stability, thermal and flame resistance. Until now, radiation cross-linking is limited to only a few industrial applications cross-linking of rubber or polymers for tyres, cables, pipes (e.g. in under floor heating systems), and heat-shrinkable tubes. Nevertheless, there exist industrial facilities like electron accelerators and gamma plant. Some of these radiation sources are operated by research institutes. 

Irradiations were carried out at the 60Co-gamma facility at Riso (2) and at the 10 Mev. linear electron accelerator at Riso (I). All solutions were irradiated in 5 cc. borosilicate glass cells, fitted with 5/20 standard taper joints. The method of evacuation, saturation, and filling is being described elsewhere by Sehested et al. (7). 

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