Pulse radiolysis linac

The stroboscopic pulse radiolysis with the single bunch electron pulse instead of pulse trains started in Argonne National Laboratory in 1975 [54]. The research fields have been extended by the stroboscopic pulse radiolysis with the picosecond single electron bunch, although most of researches had been limited to hydrated and solvated electrons in the aqueous and alcoholic solutions. This system was unable to study the kinetics of the geminate ion recombination in liquid hydrocarbons until the modification of the Argonne linac in 1983, which made possible the quality measurements of the weak absorption. 

The foray into sub-nanosecond pulse radiolysis was continued by Matheson and Jonah at Argonne, Tabata and co-workers in Tokyo, and Katayama and co-workers in Hokkaido.The experiments at Argonne measured the decay of the hydrated electron both from about 100 ps to 4 ns and from I ns to 40 ns. These results clearly showed that the decay measured was approximately a factor of 10 slower than that predicted by theory. The decay profiles are very similar to those determined using a linac-laser combination about 15 years later. The decay of the OH radical was also considerably slower than what theory predicted, which is, of course, no surprise that the two should decay at similar rates. 

Ogata A, Nakajima K, Kozawa T, Yoshida Y. (1996) Femtosecond single-bunched linac for pulse radiolysis based on laser wakefield acceleration. IEEE Trans Plasma Science 24 453-459. 

Yaday P, Rulkarni MS, Shirdhonkar MB, Rao BSM. (2007) Pulse radiolysis Pune University LINAC facility. Current Science 92 599-605. 

Almost all the work in pulse radiolysis is based on the use of three types of electron accelerators linear accelerators (linacs). Van de Graaff accelerators, and Febetrons. The first accelerator used by Keene at Manchester was a 4-MeV linac with pulses of 0.2-2 ps duration [47a] this was replaced in 1967 with an 8-12-MeV linac capable of delivering pulses from 5 ns to 5 ps duration [93]. Further improvements made to the Manchester system up to 1989 have been documented [93]. Similarly, the 13-MeV linac used at Argonne in 1960 by Matheson and Dorfman produced pulses of 0.4 to 5 ps duration [46], whereas in 1989 the equipment comprised a 20-MeV linac, capable of producing pulses from 25 ps to 10 ps duration, and a 3-MeV Van de Graaff accelerator, which is dedicated to EPR and magnetic resonance studies (see below) [95, 98]. 

The stroboscopic pulse radiolysis system described above was modified at Argonne National Laboratory to use a single fine-structure pulse from a 20-MeV L-band linac [150]. This reduced the uncertainty in the age of the primary produets to the width of a fine-structure pulse and allowed kinetic measurements to be extended to 3.5 ns. In practice, the time resolution of absorbance measurements was 100 ps. 

Because it involves more accelerating structures with multiple RF frequencies and phase relationships, and a high-performance electron gun source to inject the electrons in about one nanosecond, a sub-harmonic pre-buncher adds a lot of cost and complexity of operation ofthe linac facility. Consequently, only a few pre-bunched picosecond linacs were built for pulse radiolysis studies. The first one was installed at Argonne National Laboratory in the 1970s [2] subsequently other picosecond installations were built at the University of Tokyo Nuclear Energy Research Laboratory (NERL) in Tokai-Mura [3,4] and Osaka University [4].Very recently, a new pre-bunched linacfor pulse radiolysis has been built at the Shanghai Institute of Applied Physics. 

At the Institute for the Organic Synthesis and Photoreactivity (ISOF) is operating a 12 MeV (maximum energy with no load) Vickers L-band (1.3 GHz) traveling wave electron linear accelerator. The LINAC was put in operation mainly to be used as energy source for pulse radiolysis studies. 

The support by the Office of Basic Energy Sciences, Division of Chemical Sciences, U.S. Department of Energy, under grant No. FG-05-92-ER14310, is gratefully acknowledged. All pulse radiolysis experiments described here were performed in collaboration with John R. Miller at the Argonne National Laboratory linac facility. Renata Kobetic and Timothy R. Schatz are thanked for their work on the laser photolysis experiments. 

To collect this volume of data, linear accelerators with nanosecond time resolution were, and still are now, routinely used around the world. Faster, picoseond linac machines were built first in Toronto and then at Argonne National Laboratory. Picosecond accelerators for pulse radiolysis have been in use for nearly three decades at Argonne, at the Osaka University Radiation Laboratory, and the University of Tokyo Nuclear Engineering Research... 

The next two techniques, flash photolysis and pulse radiolysis, are similar in that unstable species can be formed and studied. Many of the same limitations exist for both techniques. Beck has recently reviewed the capabilities of available laser and pulse radiolysis facilities for creating chemical species.(Beck 1986) The current available from the picosecond pulse of the Argonne Linac is about a factor of 3 higher than given in that article (25 nC). 

---