Linear Accelerator

An 8 MeV linear electron accelerator is the experimental centerpiece of the radiation chemistry effort. This instrument is capable of delivering pulses of electrons ranging from 2 nanoseconds to 1.5 microseconds in duration. These pulses are delivered to a sample container where they ionize molecules in the sample, a process called pulse radiolysis. The ions and electrons rapidly recombine, but in the process produce large quantities of free radicals. If the sample is an aqueous solution, the radicals produced in greatest quantities are the hydroxyl radical (OH), the hydrogen atom and the hydrated electron (eaq-). The free radicals react with molecules dissolved in the water to produce the chemical species and processes that are the subject of our studies.

Detection of molecules produced by pulse radiolysis is carried out by means of optical absorption spectroscopy. Every molecule has a characteristic absorption spectrum in the visible and near ultraviolet wavelengths. By tuning a monochromator to pass only light of a wavelength that a particular molecule absorbs, the scientist can observe the increase in absorption as the concentration grows, followed by the decrease as the transient molecule reacts further. By careful selection of the molecules and wavelengths to be probed, the scientist can unravel the many reactions that contribute to an overall chemical process and lead to the ultimate reaction products.

LINAC characteristics:
Nominal beam energy: 8 MeV
RF source: 20 MW, 2856 Mhz klystron
Pulse duration: 2 to 100 nanosec, 1.5 microsec
Pulse frequency: 1 to 10 Hz or single shot
Maximum beam current: 4 amps
Nominal beam diameter: 5 mm
Pulse-to-pulse dose stability: ±3%

This linear accelerator was built by Titan Beta (Dublin, CA) and installed in March, 1995. The specifications were chosen to optimize accelerator performance for radiation chemical studies of reactions in the nanosecond-to-microsecond time domain.

Supported by the Division of
Chemical Sciences
Office of
Basic Energy Sciences
at the
U.S. Department of Energy

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Radiation Laboratory
Univ. of Notre Dame
Notre Dame, IN 46556

Tel: (574) 631-6163
Fax: (574) 631-8068

Last Modified: 02/02/2006