STATUS OF THE MICROWAVE PASER EXPERIMENT* P. Schoessow 1 #, A. Kanareykin 1 , E. Bagryanskaya 2 , V. Gorelik 2 , A. Kovshik 3 , A. V. Tyukhtin 3 , N. Yevlampieva 3 , S. Antipov 4 ,W. Gai 4 , M. Conde 4 , J.G. Power 4 1 Euclid Techlabs LLC, Rockville, MD 2 International Tomography Center, Novosibirsk, Russia, 3 Saint-Petersburg State University, Saint-Petersburg, Russia, 4 Argonne National Laboratory, Argonne, IL Abstract The PASER is a new method for particle acceleration, in which energy from an active medium is transferred to a charged particle beam. The effect is similar to the action of a maser or laser with the stimulated emission of radiation being produced by the virtual photons in the electromagnetic field of the beam. We are developing a demonstration PASER device operating at X-band, based on the availability of a new class of active materials that exhibit photoinduced electron spin polarization. We will report on the status of active material development and measurements, numerical simulations, and preparations for microwave PASER experiments at the Argonne Wakefield Accelerator facility. INTRODUCTION The principal goal of this project is the development and demonstration of the PASER (Particle Acceleration by Stimulated Emission of Radiation) operating in the microwave regime. This accelerator is based on an active medium - a new concept where the optical energy from an intense light source is transferred into the kinetic energy of an accelerated electron beam. Recently discovered chemical systems such as Tetraphenylporhpyrin (TPhP) or fullerene (C 60 ) molecules dissolved in organic solvents have been demonstrated to be active microwave amplifying or absorbing materials [1]. The main objective of the project is to perform proof- of-principle experiments to demonstrate the feasibility of the microwave PASER. In outline, the active paramagnetic medium is contained in a resonant cavity or waveguide placed in a static magnetic field. When pumped by an intense optical pulse, a population inversion is created in the medium. Initial bench test experiments will study the amplification of a microwave pulse by active media in bulk without the need for an EPR spectrometer. The bench test apparatus will then be modified by providing a cavity with a beam channel to accommodate an acceleration experiment. Besides particle acceleration based on the microwave PASER, the technologies being developed under this project have a number of important potential applications. One very promising application of these materials is in their use as active amplifying substances in optically pumped low noise and relatively high operating temperature solid-state maser amplifiers. The bench test system could lead to the development of compact, portable ESR spectrometers. This work relies heavily on both CW and time- resolved (TR) EPR (electron paramagnetic resonance, also known as ESR, electron spin resonance) measurements of candidate active materials. A review of the basic EPR principles and other background information can be found in ref. [2]. Figure 1. Energy level diagram of the active C 60 -LC medium. Transitions to T y can be either absorptive or emissive. Inset: EPR spectra of C 60 (narrow curve) and TPhP showing both absorption and emission characteristics. (Negative corresponds to emission.) ACTIVE MEDIUM DEVELOPMENT. EPR MEASUREMENTS We have studied microwave active materials with respect to the maximum rf field amplification that can be obtained and consequently the maximum energy gain that can be demonstrated with the microwave PASER experiment. C 60 -TPhP-E7 samples were studied with variations in the C 60 -TPhP complex content (1:1 and 2:1 ratios) and different complex concentrations in E7 and LC2 with the purpose of selecting an optimal composition of this type of liquid crystalline solution with a maximum EPR signal over a 120-150 MHz line width. Merck E7 and LC2 (Merck ZLI-4389) liquid crystal solvents were used in these experiments. The goal of these measurements is to find a medium with a high spin polarization density that is optimal for use in the bench test and beam acceleration experiments. This work included time resolved electron spin resonance S 0 S 1 T z T y T x Optical pump frequency k z k x k y Microwave emission absorption Intersystem crossing ___________________________________________ *Work supported by DOE SBIR Phase II Funding. # paul.schoessow@euclidtechlabs.com THPMS078 Proceedings of PAC07, Albuquerque, New Mexico, USA 03 Linear Colliders, Lepton Accelerators and New Acceleration Techniques 3166 A14 Advanced Concepts 1-4244-0917-9/07/$25.00 c 2007 IEEE